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The shape of contention: Adaptation, history, and contingency in ungulate mandibles
Abstract
Mandibles and teeth of ungulates have been extensively studied to discern the functional significance of their design. Grazing ungulates have deeper mandibles, longer coronoid processes, flatter incisor arcades, and more hypsodont molars in comparison to browsers. If the functional significance of both mandible and teeth shapes is well-established, it remains uncertain to what extent mandible shapes are really adapted to grazing, meaning that they evolved either to serve their current biological function or just as a structural requirement to accommodate higher crowned molars. Here, we address this question by studying the contribution of phylogeny, hypsodonty, and body size to mandibular shape variation. The mandible shape appeared to be significantly influenced by hypsodonty but not by body size. Interestingly, hypsodonty-related changes influenced the tooth row in artiodactyls and perissodactyls significantly but in the opposite directions, which is ultimately related to their different digestive strategies. Yet, we obtained a strong phylogenetic effect in perissodactyls, suggesting that their mandible shape should be strongly inherited. The strength of this effect was not significant within artiodactyls (where hypsodonty explained much more variance in mandible shape). Digestive strategy is deemed to interplay with hypsodonty to produce different paths of adaptation to particular diets in ungulates.
... With the emergence of grasslands and the spread of grasses, the inclusion of grasses in the diet became widespread in herbivorous mammals [42,43] and is responsible for the rapid diversification of grazing artiodactyls [16]. In morphology, the dietary shift from soft (browsing) to hard and fibrous (grazing) plant material is accompanied by profound changes in the skull and mandible, including the acquisition of high-crowned (hypsodont) molars, longer snout, and deeper mandible [44][45][46]. This pattern is present in equids, and also appeared several times among Pecora. ...
... We used the five largest eigenvectors, as they represent 95% of the cumulative shape variance explained. The ungulate tree was assembled from literature [16,46,47]. We considered individual species as either grazing artiodactyls, grazing perissodactyls, or "others" (i.e. ...
... This is especially noteworthy considering that the paleontological tree we used includes a number of non-grazing equids, such as hipparionoid horses and browsing anchitheriine equids, plus several extinct rhinos and tapirs which were all browsers. This demonstrates the method was able to find convergence among grazers despite the effect of phylogeny and body size on mandibular shape variation [46]. ...
Morphological convergence is an intensely studied macroevolutionary phenomenon. It refers to the morphological resemblance between phylogenetically distant taxa. Currently available methods to explore evolutionary convergence either: rely on the analysis of the phenotypic resemblance between sister clades as compared to their ancestor, fit different evolutionary regimes to different parts of the tree to see whether the same regime explains phenotypic evolution in phylogenetically distant clades, or assess deviations from the congruence between phylogenetic and phenotypic distances. We introduce a new test for morphological convergence working directly with non-ultrametric (i.e. paleontological) as well as ultrametric phylogenies and multivariate data. The method (developed as the function search.conv within the R package RRphylo) tests whether unrelated clades are morphologically more similar to each other than expected by their phylogenetic distance. It additionally permits using known phenotypes as the most recent common ancestors of clades, taking full advantage of fossil information. We assessed the power of search.conv and the incidence of false positives by means of simulations, and then applied it to three well-known and long-discussed cases of (purported) morphological convergence: the evolution of grazing adaptation in the mandible of ungulates with high-crowned molars, the evolution of mandibular shape in sabertooth cats, and the evolution of discrete ecomorphs among anoles of Caribbean islands. The search.conv method was found to be powerful, correctly identifying simulated cases of convergent morphological evolution in 95% of the cases. Type I error rate is as low as 4-6%. We found search. conv is some three orders of magnitude faster than a competing method for testing convergence. PLOS ONE | https://doi.org/10.1371/journal.pone.
... The cranium and mandible are complex components of the vertebrate skeleton that are intimately associated with feeding ability and are probable products of adaptation (Herring 1993). Integrating shape and biomechanical analyses can improve our understanding of how the form-function relationships of these phenotypes vary among species and the selective regimes that shaped them (Pérez-Barbería and Gordon 1999;Raia et al. 2010;Cooke and Terhune 2015). ...
... Recent advances in geometric morphometric methods (GMMs) are opening unprecedented possibilities for investigating shape (Klingenberg 2010;Adams et al. 2013). Mammals, in particular, have been extensively studied and clearly exhibit various patterns of skull shape variation (Marcus et al. 2000;Raia et al. 2010;Cáceres et al. 2014;Cardini and Polly 2013;Meloro et al. 2015;Hendges et al. 2016). The mechanical implications of this variation are a growing topic, and analyses integrating shape and biomechanical features have proven to be powerful tools for understanding form-function relationships in mammals. ...
... Diet is an important selective force acting on the craniomandibular morphologies of mammals, including peccaries (Kiltie 1985;Pérez-Barbería and Gordon 1999). Its effects could be even more pronounced on mandible shape given the more precise functional role of mandibles in feeding (Raia et al. 2010;Ross and Iriarte-Diaz 2014). The pattern we found for P. tajacu and T. pecari is characteristic of omnivorous mammals relying on hard foods (Pérez-Barbería and Gordon 1999; Ravosa et al. 2000 ;Taylor 2006;Nogueira et al. 2009;Maestri et al. 2016). ...
A primary requirement of the mammalian skull is to exert forces on different foods and to resist the forces imposed on it during feeding. Skull shape patterns within and among mammals are generally well known, but the biomechanical relevance of this variation remains limited for some groups. By integrating geometric morphometric and biomechanical analyses, we test the hypothesis that skull shape in peccaries reflects biomechanical attributes to generate and dissipate powerful forces, presumably in response to tough foods. We obtained skull shape and size from 213 specimens of the three living peccary species and estimated bite force, bite stress at molars, bending and shear stress on the mandibular corpus, and condylar stress. We found larger estimated bite forces, greater resistance to bending loads, and lower stress emerging from the larger muscle attachment areas and shorter and deeper mandibular corpora for both Pecari tajacu and Tayassu pecari relative to Parachoerus wagneri. Peccaries (P. tajacu and T. pecari) with more powerful biomechanical attributes feed mainly on tougher foods (e.g., palm fruits). These results support the hypothesis that species eating tough foods tend to have a feeding morphology mechanically adapted to stronger bites and greater biting resistance, which must be closely reflected in their craniomandibular shape. Um requerimento primário do crânio de um mamífero é exercer forças em diferentes alimentos e resistir às forças impostas nele durante a alimentação. Os padrões de forma do crânio dentro e entre mamíferos são geralmente bem conhecidos, entretanto a relevância biomecânica desta variação permanece limitada a alguns grupos. Integrando análises de morfometria geométrica e de biomecânica nós testamos a hipótese de que a forma do crânio de tayassuídeos reflete atributos biomecânicos para gerar e dissipar forças de grande magnitude, tal como em resposta à alimentos duros. Nós obtivemos a forma e o tamanho do crânio de 213 espécimes das três espécies de tayassuídeos viventes e estimamos a força de mordida e o stress nos molares, no corpo mandibular e no côndilo. Nós encontramos maiores forças de mordida e de resistência e baixo stress emergindo de áreas mais amplas de inserção muscular e de corpos mandibulares mais curtos e altos de Pecari tajacu e Tayassu pecari em relação a Parachoerus wagneri. Tayassuídeos (P. tajacu and T. pecari) com atributos biomecânicos mais poderosos se alimentam principalmente de alimentos duros (por exemplo, frutos de palmeiras). Estes resultados suportam a hipótese de que espécies que se alimentam de alimentos duros tendem a apresentar uma morfologia do aparato alimentar mecanicamente adaptada a mordidas fortes e grande resistência de mordida, que deve estar intimamente associada as suas formas craniomandibulares.
... This reflects the strict relationship between ungulate diet and the environment (Sponheimer et al., 2003). In fact, it is well known that craniomandibular morphologies of ungulates are determined by interactions between adaptations to particular feeding habits and biomechanical and/or phylogenetic constraints (P erez- Barber ıa & Gordon, 1999;Mendoza, Janis & Palmqvist, 2002;Mendoza & Palmqvist, 2008;Piras et al., 2010;Raia et al., 2010). Moreover, a small size effect in craniodental morphology has been recently established Raia et al., 2010) as a consequence of the biomechanical constraints that different digestive strategies exert on them . ...
... In fact, it is well known that craniomandibular morphologies of ungulates are determined by interactions between adaptations to particular feeding habits and biomechanical and/or phylogenetic constraints (P erez- Barber ıa & Gordon, 1999;Mendoza, Janis & Palmqvist, 2002;Mendoza & Palmqvist, 2008;Piras et al., 2010;Raia et al., 2010). Moreover, a small size effect in craniodental morphology has been recently established Raia et al., 2010) as a consequence of the biomechanical constraints that different digestive strategies exert on them . Nevertheless, no study has yet explored how and to what extent the skull shape of ungulate species responds to environmental, allometric (skull size) and spatial factors on broad-scales. ...
... If the environment affects the geographical variation in the S. scrofa mandible (Endo et al., 2002), a species of a closed related family, we might also expect a strong environmental influence on the variation in skull shape of Neotropical peccaries. However, the same cannot be expected for size due to recent findings by Raia et al. (2010) and Piras et al. (2010). Furthermore, the effects of geographical space on peccaries are expected to be mainly observed in interaction with the environment since environmental variables tend to be naturally spatially structured (C aceres et al., 2014b). ...
The influence of the environment on the geographical variation of morphological traits has been recognized in a number of taxa. Pecari tajacu and Tayassu pecari are ideal models to investigate intraspecific geographic variation in skull because of their wide and heterogeneous geographical distribution in South America. We used geometric morphometric procedures to examine the geographical variation in skull shape of 294 adult specimens of these species from 134 localities. We quantified to what extent skull shape variation was explained by environment, skull size and geographical space using variation partitioning analysis. We detected a strong pattern of geographic variation for P. tajacu skull shape, but not for T. pecari. The environment seems to be the major selective force that drives skull shape variation in both species. Nevertheless, other spatially structured processes (e.g. genetic drift, gene flow) might also have affected variation in the skull shape of the more widespread species P. tajacu. Allometric relationships might reflect the biomechanical constraints that are thought to be strong enough to limit size-related changes in T. pecari skull shape.
... Moreover, body size can be associated with didelphid habitat as it can be a reasonable prediction for dental shape in mammals (Gordon 2003, Mendoza et al. 2006, Raia et al. 2010. Body size alone has already been emphasized as an influence on molar shape (Caumul and Polly 2005), having an important role on the reconstruction of life history and ecology of fossil species based on teeth (Gingerich et al. 1982). ...
... Many studies with mammals show significant results when associating their shape with ecological, functional, and evolutionary features, whether it is with the skull, mandible, or dentition (Astúa et al. 2000, Caumul and Polly 2005, Raia et al. 2010. When shape is addressed, it appears to be strongly subjected to the action of phylogenetic inertia due to common ancestry, which means that closely related species tend to present similar shape attributes regardless of environmental pressure (Greenacre and Vrba 1984, Caumul and Polly 2005, Klingenberg and Gidaszewski 2010, as it seems to be the case of mandibular development throughout the evolution of mammals , Rivals et al. 2008, Prevosti et al. 2011, as well as the evolution of body mass in vertebrates (Abouheif 1999). ...
... If there is a strong phylogenetic signal in these shape structures throughout Didelphidae lineages, as found by Chemisquy et al. (2015), closely related species will exhibit a more similar shape regarding homologous structures than other distantly related species. This will indicate the presence of phylogenetic inertia acting on the evolution of these structures (Raia et al. 2010). If tribosphenic molars, which are inherent to marsupial diversification, assumed versatile functions (Lopatin andAverianov 2006, Luo 2007), allowing a better utilization of food, the variation of their shape could be an important clue in the understanding of feeding evolution in marsupials. ...
Tribosphenic molars are considered great innovations in mammals and are related to several structures and variables that can explain adaptation. The aim of this study was to investigate the importance of body size and habitat relation, using a phylogenetic approach, in the first lower molar shape in didelphid marsupials. Geometric morphometric analyses of the lower molar’s shape were performed on 261 specimens, 130 females and 131 males, covering 14 genera and 37 species of the Didelphidae family. The molar conformation showed a larger talonid in relation to the trigonid in more arboreal genera, and narrower and longer molars in genera with a larger body size. Phylogeny was the variable with the highest explanation for both females and males (16.17% and 9.02%, respectively). The body size was significant in males, presenting an important influence on molar shape, while the body size in females was not significant when phylogenetic relationship was controlled for. In both sexes, habitat presents a strong effect of phylogeny, with no direct effect on molar shape. Didelphid molar shape is another result of its phylogenetic history and does not respond very much to environmental pressures. Male body size influences molar shape in didelphids, even in the presence of a strong phylogenetic signal.
... Although "mandible" is in fact synonym for chewing (from the latin mandere = to chew), no straightforward link occurs between mandible shape and diet in a broad range of mammals (cf. Turnbull 1970;Raia et al. 2010;Meloro and O"Higgins 2011) and multiple factors need to be considered simultaneously in order to understand mandible shape evolution at the macroevolutionary scale. ...
... We expect a strong interplay among mandibular size, diet and phylogeny to take place in primates. Such interplay is evident in a number of studies pertaining to mammalian mandibles (Meloro et al. 2008;Raia et al. 2010;Monteiro and Nogueira 2011) and primate skulls (Fleagle et al. 2010;Perez et al. 2011;Bennet and Goswami 2012;Baab et al. 2014). ...
... Mandibular shape variation at interspecific scale has been generally interpreted as the result of a compromise between the constraints imposed by phylogenetic history and masticatory function (Caumul and Polly 2005;Meloro et al. 2008;Raia et al. 2010). Primates are no exception among mammals since they primarily exhibit a phylogenetic signal in mandibular morphology, which is secondarily influenced by adaptations to different diets. ...
Chewing on different food types is a demanding biological function. The classic assumption in studying the shape of feeding apparatuses is that animals are what they eat, meaning that adaptation to different food items accounts for most of their interspecific variation. Yet, a growing body of evidence points against this concept. We use the primate mandible as a model structure to investigate the complex interplay between shape, size, diet and phylogeny. We find a weak but significant impact of diet on mandible shape variation in primates as a whole but not in anthropoids and catarrhines as tested in isolation. These clades mainly exhibit allometric shape changes which are unrelated to diet. Diet is an important factor in the diversification of strepsirrhines and platyrrhines and a phylogenetic signal is detected in all primate clades. Peaks in morphological disparity occur during the Oligocene (between 37 and 25 Ma) supporting the notion that an adaptive radiation characterized the evolution of South American monkeys. In all primate clades, the evolution of mandible size is faster than its shape pointing to a strong effect of allometry on ecomorphological diversification in this group. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
... Assessing the role of the environment in body structure development is fundamental to inform management decisions such as selective hunting. In ungulates, selected bones are regularly used as indicators of environmental changes [35,36] and, among them, the mandible is often a main element [37][38][39][40]. Researchers frequently use mandible as an ecological indicator [41], especially in roe deer, because it is one of the first bones to ossify and to reach its final size within the early years of life [42,43]. ...
... Unfortunately, the coronoid process, being a very protruding part, is easily damaged or lost during sample preparation, so that analysis could not always take into account this part in the study of mandible shape or size [39]. Despite the difficulty of having intact mandibular samples, the coronoid process must be taken into consideration, according to us, to monitor and evaluate the relationship between trophic resources and roe deer mandible shapes, and above all for the roe deer fawn mandible samples. ...
The analysis of body shape variability has always been a central element in biology. More recently, geometric morphometry has developed as a new field in shape analysis, with the aim to study body morphological variations and the identification of their causes. In wildlife management, geometric morphometry could be a useful tool to compare the anatomical structures of an organism and quantify its geometric information in order to relate them to environmental factors, thus identifying the causes and effects of the variation and acting management and/or conservation plans. The aim of our study is to evaluate the relationship between roe deer mandible shape and trophic resources available during autumn and winter. We applied a geometric morphometry approach consisting of a Relative Warp analysis of landmark data in 26 roe deer fawn mandibles. Each sample was assigned to an age category and to an environmental category based on the territory carrying capacity. The mandible shape of samples under 8 months of age is likely influenced by the availability of trophic resources. Our findings suggest that the mandible shape is a reliable instrument to assess resource availability. Geometric morphometry could thus represent an additional tool for roe deer management.
... The causes of the development of a precocious hypsodonty in SA notoungulates are not entirely understood and they might be very complex Madden, 2014;Strömberg et al., 2013). Its development was initially linked to adaptive shifts given grassland/open habitats expansion (Flynn et al., 2003), consistent with the idea that most modern ungulate clades developed hypsodont teeth in drier and more open habitats (Damuth and Janis, 2011;Janis, 1990;Raia et al., 2010). However, recent works found that grasses only became common in SA after the Miocene, being relatively rare during the Eocene, making it unclear whether hypsodonty evolved in forested or in open but grass-free habitats Raia et al., 2010;Strömberg et al., 2013). ...
... Its development was initially linked to adaptive shifts given grassland/open habitats expansion (Flynn et al., 2003), consistent with the idea that most modern ungulate clades developed hypsodont teeth in drier and more open habitats (Damuth and Janis, 2011;Janis, 1990;Raia et al., 2010). However, recent works found that grasses only became common in SA after the Miocene, being relatively rare during the Eocene, making it unclear whether hypsodonty evolved in forested or in open but grass-free habitats Raia et al., 2010;Strömberg et al., 2013). In any case, the relevance of exogenous grit or soil's ingestion has driven the necessity to deal with tooth abrasion has been claimed and now are considered a plausible mechanism for hypsodonty evolution in ungulates (Damuth and Janis, 2011;Dunn et al., 2015;Madden, 2014;Semprebon et al., 2019;Strömberg et al., 2013). ...
Members of the Order Notoungulata are among the most diverse and common mammals in South America during the Cenozoic. Several lineages within notoungulates (e.g., suborders Typotheria and Toxodontia) show a tendency for increased body sizes and hypsodonty during the last 50 Myr. However, the timing, evolutionary mode, and drivers of such tendencies are not entirely understood. In this paper, we use an extensive database of notoungulate fossil occurrences and body mass and hypsodonty estimates to characterize the evolutionary mode of these two phenotypic traits over time, test the extent to which several factors (e.g., development of open environments in the south of South America) have influenced it through time, and investigate whether large trait values were selected through elevated origination or reduced extinction rates. Our results demonstrate that most of the major notoungulate clades evolved toward larger body sizes (up 1500 kg) and higher tooth crown, from a small and low-crowned tooth ancestor, in a punctuated mode. We also show that body mass and the hypsodonty in typotherians and toxodonts had a coupled evolutionary history. Species sorting was a relevant macroevolutionary process in some notoungulate clades, as taxa with high teeth crown and body mass had lower extinction rates. Finally, the development of the hypsodonty in notoungulates must reflect repeated and quick instances of adaptive responses to the increased availability of volcanic or other terrigenous particles, within the broad context of the SSA Cenozoic Andean mountain building.
... He also mentioned a specimen "b" not included in our analysis since the published sizes are much larger than observed in Amphimoschus ponteleviensis. Raia et al. [88] referred to an "Amphimoschus elegans" based on their geometric morphometrics analysis. This undescribed species might actually be the result of confusion between the genera Amphimoschus and Amphitragulus. ...
... The mandibles of these genera are different in shape [6]. The mandible described by Raia et al. [88] looks very similar to those of Amphitragulus elegans of Mennecart et al. [6]. ...
Amphimoschus is an extinct Eurasian ruminant genus, mostly recorded in Europe, without a close living relative and, hence, an unknown systematic position. This genus is known from around 50 localities from the late early to the middle Miocene. Two species were described during 180 years, but since their first description during the late 19 th century and early 20 th century, hardly any detailed taxonomic work has been done on the genus. Over the years, extensive collecting and excavating activities have enriched collections with more and more complete material of this still rare and enigmatic animal. Most interestingly, a number of skull remains have been unearthed and are promising in terms of providing phylogenetic information. In the present paper, we describe cranial material, the bony labyrinth, the dentition through 780 teeth and five skulls from different ontogenetic stages. We cannot find a clear morphometric distinction between the supposedly smaller and older species Amphimoschus artenensis and the supposedly younger and larger species A . ponteleviensis . Accordingly, we have no reason to retain the two species and propose, following the principle of priority (ICZN chapter 6 article 23), that only A . ponteleviensis Bourgeois, 1873 is valid. Our studies on the ontogenetic variation of Amphimoschus does reveal that the sagittal crest may increase in size and a supraorbital ridge may appear with age. Despite the abundant material, the family affiliation is still uncertain.
... However, mandible movement types are also constrained by developmental processes so that interspecific variation might reveal strong phylogenetic signal in morphological design and performance [6,17,[27][28][29]. This phylogenetic signal is found to be stronger in Perissodactyla than Artiodactyla [30]. The degree to which mandibular morphology is influenced by diet, reflects phylogenetic affinities or both is thus still debated. ...
... terrestris) differ from the other perissodactyla. Cluster analysis suggests that T. terrestris has affinities with this group, possibly due to a strong phylogenetic signal [30], however it is almost consistently isolated in the lower left space of all intervals method biplots (but see Fig 8, Case 3), suggesting significant differences with the rest of the Perissodactyla. In particular, T. terrestris has the lowest average and peak stress values (see Fig 3 and S1 and S2 Tables of the Supplementary information). ...
There is considerable debate regarding whether mandibular morphology in ungulates primarily reflects phylogenetic affinities or adaptation to specific diet. In an effort to help resolve this debate, we use three-dimensional finite element analysis (FEA) to assess the biomechanical performance of mandibles in eleven ungulate taxa with well-established but distinct dietary preferences. We found notable differences in the magnitude and the distribution of von Mises stress between Artiodactyla and Perissodactyla, with the latter displaying lower overall stress values. Additionally, within the order Artiodactyla the suborders Ruminantia and Tylopoda showed further distinctive stress patterns. Our data suggest that a strong phylogenetic signal can be detected in biomechanical performance of the ungulate mandible. In general, Perissodactyla have stiffer mandibles than Artiodactyla. This difference is more evident between Perissodactyla and ruminant species. Perissodactyla likely rely more heavily on thoroughly chewing their food upon initial ingestion, which demands higher bite forces and greater stress resistance, while ruminants shift comminution to a later state (rumination) where less mechanical effort is required by the jaw to obtain sufficient disintegration. We therefore suggest that ruminants can afford to chew sloppily regardless of ingesta, while hindgut fermenters cannot. Additionally, our data support a secondary degree of adaptation towards specific diet. We find that mandibular morphologies reflect the masticatory demands of specific ingesta within the orders Artiodactyla and Perissodactyla. Of particular note, stress patterns in the white rhinoceros (C. simum) look more like those of a general grazer than like other rhinoceros’ taxa. Similarly, the camelids (Tylopoda) appear to occupy an intermediate position in the stress patterns, which reflects the more ancestral ruminating system of the Tylopoda.
... Craniodental morphology has been linked to dietary ecology in a wide array of animals and has been particularly well-studied in ungulates (Mendoza et al. 2002;Clauss et al. 2008;Raia et al. 2010). In ungulates, one of the best-understood craniodental differences between grazing and browsing forms is the overall shape of the muzzle (Janis and Ehrhardt 1988;Solounias and Moelleken 1993;Pérez-Barbería and Gordon 2001;Tennant and MacLeod 2014). ...
... These diagrams illustrate shape change across a dietary spectrum and none corresponds with a particular taxon non-selective bulk feeders and narrow-muzzled forms inferred to be more selective (Bargo et al. 2006b; Bargo and Vizcaíno 2008;Shockey and Anaya 2011). Similar dietary trends in muzzle and mandible shape have been shown for extinct equids (Raia et al. 2010;Bernardes et al. 2013) and have also been inferred for extinct South American relatives of armadillos known as glyptodonts (Vizcaíno et al. 2011). ...
The goal of ecomorphology is to identify morphological variation that is related to ecology (e.g., dietary preference or locomotor habits), with the aim of inferring ecological traits from morphological traits. This chapter reviews the basic principles of ecomorphology and provides many examples of ecomorphic studies in a range of taxa, with an emphasis on bovids (antelope and relatives). The focus of this chapter is on “applied” ecomorphology, which refers to studies that use ecomorphology as a tool to reconstruct environments. The chapter summarizes some of the strengths and weaknesses of the applied ecomorphic approach, and discusses future directions for studies using this methodology.
... Although traditional interpretations of ecophenotypic patterns are an oversimplification of complex environmental systems (Millien et al. 2006), some interpretations may be proposed. Studies on "function versus phylogeny" covariation have improved our understanding of the role of natural selection in shaping mammalian skulls (e.g., Cheverud 1982Cheverud , 1985Polly 1998;Cardini 2003;Cardini and O'Higgins 2004;Caumul and Polly 2005;Cardini and Elton 2008;Raia et al. 2010). Selective forces, synergistically with the effects of historical contingency, may drive repeated patterns of homoplasy that provide a better understanding of the evolutionary history of phenotypes (Stayton 2005), and define the range of phenotypic possibilities (e.g., Raia et al. 2010). ...
... Studies on "function versus phylogeny" covariation have improved our understanding of the role of natural selection in shaping mammalian skulls (e.g., Cheverud 1982Cheverud , 1985Polly 1998;Cardini 2003;Cardini and O'Higgins 2004;Caumul and Polly 2005;Cardini and Elton 2008;Raia et al. 2010). Selective forces, synergistically with the effects of historical contingency, may drive repeated patterns of homoplasy that provide a better understanding of the evolutionary history of phenotypes (Stayton 2005), and define the range of phenotypic possibilities (e.g., Raia et al. 2010). Differentiation in cranial shape may be the result of convergence or parallelism, and may promote access to available resources in extreme habitats. ...
Sengis are small mammals in the order Macroscelidae that are shrew-like in appearance. They are cursorial and saltatorial, insectivorous and omnivorous. We studied Macroscelides spp. and Elephantulus rupestris with overlapping distributions in South Africa and Namibia. They have similar life histories and are good candidate species for comparative studies. We used geometric morphometric techniques for 3 views of a total of 43 skulls representing E. rupestris, M. flavicaudatus, and M. proboscideus to evaluate variation in skull shape that may be associated with geographical location. We pooled all Macroscelides into a single group because the speciation event was recent. We observed a pattern of shape variation in both taxa that followed a latitudinal gradient from the Western Province of Africa with Mediterranean vegetation to northern Namibia with xeric habitats. At higher latitudes, skulls were elongated with narrow frontals, premaxilla, and maxilla, while at low latitudes, the parietals were reduced and both occipitals and bullae timpanicae were expanded. We interpreted these patterns in the context of predator avoidance and foraging.
... The mammalian mandible represents a model for the evolution of complex structures (Atchley and Hall 1991) and its morphology has been widely studied to reconstruct feeding behaviour of extant and fossil species (Meloro 2011;Figueirido et al. 2009;van Heteren et al. 2016;Raia 2004;Raia et al. 2010;Meloro et al. 2008;Piras et al. 2010Piras et al. , 2013, to investigate relationships with ecological adaptation and phylogenetic history (Barroso et al. 2012), to assess geographic variation (Meloro et al. 2017) and getting insights into its modular structure (Klingenberg et al. 2003;Monteiro and Nogueira 2010;Guidarelli et al. 2014). In spite of its structural simplicity, studies on both terrestrial (Klingenberg et al. 2003;Raia 2004;Meloro et al. 2008Meloro et al. , 2015a Abstract Phenotypic changes in the mammalian mandible can occur at different spatial and temporal scales. ...
... Differences in feeding apparatus morphologies and diets revealed in both terrestrial (Adams and Rohlf 2000) and marine vertebrates (del Castillo et al. 2017) may indicate how partitioning of ecological niches reduce the occurrence of competition for food resources when the species are in direct sympatry (Bearzi 2005). Many studies have demonstrated that the mandible exhibits a strong correlation between form and diet, showing how adaptation to different feeding strategies and food consistency can rapidly shape the mandibular structure (Anderson et al. 2014;Meloro 2011;Meloro and O'Higgins 2011;Raia et al. 2010;Raia 2004). Therefore, mandibular shape changes could be explained in terms of adaptive processes (resulting in convergence or divergence) related to interspecific interactions and feeding ecology. ...
Phenotypic changes in the mammalian mandible can occur at different spatial and temporal scales. We investigated mandibular size and shape variation in three extant closely related dolphins (Cetacea, Odontoceti): Tursiops truncatus, Stenella coeruleoalba and Delphinus delphis in order to test the hypothesis that similar phenotypic changes occur across the same geographical gradient. Our data included 219 specimens representative of the following geographic locations: the Mediterranean Sea, the eastern north Atlantic and the North Sea. Each mandibula was photographed laterally and spatial positioning of eight homologous 2D landmarks was recorded. After applying generalised Procrustes analysis (GPA), intraspecific variation was first investigated between sexes and among populations to allow further pooling of samples. Size and shape differences among populations and species were investigated through multivariate ordination techniques (PCA), Procrustes ANOVA and allometric analyses. In all three species, Mediterranean populations clearly differed in mandible shape from the extra-Mediterranean ones. Among the three, the direction of geographic phenotypic changes was significantly similar in the striped and common dolphin, while the bottlenose dolphin was the most divergent species, differing both in size and allometric trajectory. Shape variation of the two former species highlighted a morphological convergence in the Atlantic, and a phenotypic divergence in the Mediterranean. Shape differences among the three dolphin species were interpreted in the light of different prey preferences, feeding strategies and habitat partitioning to avoid direct competition.
... integrated to the databases provided in Raia et al. (2009) and Carotenuto et al. (2010Carotenuto et al. ( , 2015. In order to assess the influence of species ecology on community composition, we assigned each species to distinct feeding categories after Price et al. (2012), Meloro et al. (2008) and Raia et al. (2010) (see Supplementary Table 1 for species attributions). When compiling the dataset, we discarded species with uncertain classification and fully revised them for synonyms. ...
... For the extinct species tips are placed at the last known appearance date of the species in the fossil record. Species first appearance records in the NOW and paleobiology databases were used to calculate branch lengths (Finarelli and Flynn, 2006;Meloro et al., 2008;Raia et al., 2010). ...
... In ungulates, the research has mostly concentrated on the inter-specific differences in the mandible shape in relation to the various Electronic supplementary material The online version of this article (doi:10.1007/s10914-016-9344-y) contains supplementary material, which is available to authorized users. feeding categories, such as browsers, grazers, or mixed feeders (Hofmann and Stewart 1972;Hofmann 1989;Pérez-Barbería and Gordon 1999;Raia et al. 2010;Fraser and Theodor 2011). On the contrary, the intra-specific level has received much less attention, despite the great geographic distribution and morphological variation in many ungulate species (Geist 1998). ...
... It is still unknown whether these particular clusters exhibit any phenotypic differences. Previous studies support a significant phylogenetic effect in mandible shape disparity in the ungulates at the inter-specific level (e.g., Pérez-Barbería and Gordon 1999; Raia et al. 2010). Furthermore, genetic structure was recently suggested to be reflected in the geographic variation of phenotypic traits in the moose (Herfindal et al. 2014). ...
Intra-specific geographic variation is probably one of the most common patterns studied in ungulate morphology. However, the shape of the mandible, a crucial feature with regard to feeding, has been greatly understudied in this context. Here, we utilized a museum collection of moose (Alces alces) mandibles to investigate whether we could detect significant variation in this species, and test for the existence of geographic patterns and associations with population genetic structure. We applied a landmark-based geometric morphometrics approach, analyzing shape data with principal component analysis and linear mixed models. A significant geographic shift in the shape of the moose mandible was revealed. The main pattern was similar in both sexes; however, there was a consistent difference in shape between males and females over the latitudinal scale. The main changes included an enlargement in the attachment surfaces of the muscles controlling biting and mastication, suggesting more effective mastication towards the north, plausibly as an adaptive response to a harder and tougher wintertime diet. Additionally, more subtle, yet statistically significant age-related shape variation was discovered. Interestingly, no or only a weak association between the morphometric variation and the genetic population structure was detected with neutral molecular markers.
... Some intrafamilial relationships are not known and were therefore left as soft polytomies. This is known to have minor impact on variance-covariance matrix estimation [34][35][36], which is important for phylogenetic comparative methods [37]. Species first appearance records in the NOW and PaleoDB databases were used to calculate branch lengths [34][35][36]. ...
... This is known to have minor impact on variance-covariance matrix estimation [34][35][36], which is important for phylogenetic comparative methods [37]. Species first appearance records in the NOW and PaleoDB databases were used to calculate branch lengths [34][35][36]. ...
Species co-occur with different sets of other species across their geographical distribution,which can be either closely or distantly related. Such co-occurrence patterns and their phylogenetic structure within individual species ranges represent what we call the species phylogenetic fields (PFs). These PFs allow investigation of the role of historical processes—speciation, extinction and dispersal—in shaping species co-occurrence patterns, in both extinct and extant species. Here, we investigate PFs of large mammalian species during the last 3 Myr, and how these correlate with trends in diversification rates. Using the fossil record, we evaluate species’ distributional and co-occurrence patterns along with their phylogenetic structure. We apply a novel Bayesian framework on fossil occurrences to estimate diversification rates through time. Our findings highlight the effect of evolutionary processes and past climatic changes on species’ distributions and co-occurrences. From the Late Pliocene to the Recent, mammal species seem to have responded in an individualistic manner to climate changes and diversification dynamics, co-occurring with different sets of species from different lineages across their geographical ranges. These findings stress the difficulty of forecasting potential effects of future climate changes on biodiversity. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
... In mammals, mandible shape is usually related to diet and feeding behaviors, and has a primary function in capturing and processing food (Prevosti et al. 2012). The size and shape variation of the mandible has been studied in several mammalian groups, such as in primates (Meloro et al. 2015), rodents (Álvarez et al. 2011), ungulates (Raia et al. 2010), and carnivores (Christiansen, 2008). In turn, variation in cranial shape (Chemisquy et al. 2021) and scapula (Astúa 2009) in Didelphidae has already been analyzed, and recently Brum et al. (2022) have evaluated variation in size and shape in the mandibles in a subset of species from all three orders of American marsupials. ...
Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates, invertebrates, and plant matter. While cranium and scapula variation has already been examined within Didelphidae, variation in mandible shape, usually associated with diet or phylogeny in other mammalian groups, has not yet been properly assessed in the family. We evaluated the variation in mandible shape and size of didelphids (2470 specimens belonging to 94 species) using 2D geometric morphometrics. We classified the diet of the didelphids into four broad categories to assess whether morphospace ordination relates to dietary habits. We also provided the most comprehensive phylogeny for the family (123 out of the 126 living species) using 10 nuclear and mitochondrial genes. We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony. We found phylogenetically structured variation in mandible morphology between didelphid groups, and our results indicate that they have a significant phylogenetic signal. The main axis of shape variation is poorly related to size, but the second is strongly allometric, indicating that allometry is not the main factor in shaping morphological diversity on their mandibles. Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa.
... The evolution of body size and its allometric consequences on shape have played an important role in ecomorphological diversification in different mammalian taxa, such as artiodactyls, carnivores, primates, and rodents (Marroig and Cheverud 2005;Renaud et al. 2006;Meloro and Raia 2010;Raia et al. 2010;Meloro et al. 2015). Indeed, locomotor specialization through adaptive evolution may be achieved through an allometric change of shape and proportions (Schmidt-Kittler 2002, 2006Meloro et al. 2015;Sansalone et al. 2018). ...
Locomotion, as a fundamental function in mammals directly associated with the use of ecological resources, is expected to have anatomical structures functionally committed that evolved under intense selective pressure, possibly carrying specializations for different locomotor habits. Among caviomorph rodents, the family Echimyidae stands out for having the greatest species richness, with relatively well-resolved phylogenetic relationships, wide variation in body mass, and remarkable diversity of locomotor habits, including arboreal, scansorial, semi-aquatic, semifossorial, and terrestrial forms. Thus, Echimyidae constitutes a promising model for understanding how phylogenetic, allometric, and ecological factors affect the evolution of postcranial structures directly linked to locomotor function. We investigated the influence of these three factors on scapular and humeral morphological variation in 38 echimyid species using two-dimensional geometric morphometry and phylogenetically informed comparative methods. Scapular and humeral shape variation had a low correlation with body mass and structure size, conveying a small or negligible allometric effect. Conversely, a significant moderate to strong phylogenetic signal was detected in both structures, suggesting that an important part of their morphometric variation results from shared evolutionary history. Notably, morphological variation of the scapula was extensively structured by phylogeny, without the marked influence of locomotor habits, suggesting that its shape may be a suitable taxonomic marker. Finally, locomotor habits were important in structuring the morphological variation of the humerus. Our results suggest that the morphologies of the scapula and humerus, despite being anatomically and functionally interconnected, were differentially shaped by ecological factors associated with locomotor habits.
... Therefore from a purely morphometric perspective, these two mandibles could belong to a single species. The functional and phylogenetic constraints on mandible shape within artiodactyls (Raia et al. 2010) may have resulted in similar mandibular morphologies in two closely related species (or genera); however, due to these uncanny morphometric similarities, we posit that Masritherium depereti CGM 30798 and Brachyodus onoideus ULg M5000 are likely conspecific, with the former being a junior synonym of the latter. ...
The University of Liège Geology Department curates a relatively complete cranium and mandible of the Miocene anthracothere Brachyodus onoideus, lacking only the premaxillae, parts of the maxillae and pterygoids. Although comparable in dimensions, the fossils probably represent two individuals. The specimens resolve several issues that have plagued interpretations of the genus regarding the resting posture of the head on the vertebral column, the hafting of the neurocranium onto the splanchnocranium and the lower dental formula. The provenance is unknown, but sandy sediment adhering to the skull and the pale, mottled colouration of the bones and teeth suggest that it may have been collected from the Sables de l’Orléanais, France. The dimensions and morphology of the mandible accord with the holotype of Brachyodus onoideus from Neuville-aux-Bois in the same sedimentary deposits; based on this similarity and metric comparisons of upper and lower dentition, we assign the Liège specimen to this species. The life appearance and behaviour of Brachyodus are discussed, with a preliminary description, a high-resolution 3D rendering, and stereo images of the specimens provided to make them available to the scientific community
... The mandible is one of the main bones involved in masticatory functions and several studies established a link between mandibular shape and diet in extant and extinct taxa, notably in primates (Daegling, 1992;Taylor, 2006;Wroe et al., 2010). In contrast, other analyses established no straightforward relationship between dietary categories and the morphology of the mandible (Arbour et al., 2019, Meloro et al., 2015Raia et al., 2010;Tamagnini et al., 2021;Turnbull, 1970, Zelditch et al., 2017 underlining the absence of a clear link between the type of food and the shape of the masticatory apparatus. This lack of a clear relationship can be explained as dietary habits and adaptations to certain types of food are not equivalent. ...
Dietary habits exert significant selective pressures on anatomical structures in animals, leading to substantial morphological adaptations. Yet, the relationships between the mandible and diet are still unclear, raising issues for paleodietary reconstructions notably. To assess the impact of food hardness and size on morphological structures, we used an experimental baseline using a model based on the domestic pig, an omnivorous mammal with bunodont, thick‐enameled dentition, and chewing movements similar to hominids. We hypothesized that the consumption of different types of seeds would result in substantial differences in the morphology of the mandible despite similar overall diets. The experiment was conducted on four groups of juvenile pigs fed with mixed cereal and soy flours. The control group received only flours. We supplemented the four others with either 10 hazelnuts, 30 hazelnuts, 30% barley seeds or 20% corn kernels per day. We investigated the shape differences between the controlled‐fed groups using three‐dimensional geometric morphometrics. Our results provide strong evidence that the supplemental consumption of a significant amount of seeds for a short period (95 days) substantially modify the mandibular morphology of pigs. Our analyses suggest that this shape differentiation is due to the size of the seeds, requiring high and repeated bite force, rather than their hardness. These results provide new perspectives for the use of mandibular morphology as a proxy in paleodietary reconstructions complementing dental microwear textures analyses. This article is protected by copyright. All rights reserved.
... and Jeff Martz (United States National Park Service), available for academic use with attribution. structuring does not preclude meaningful functional interpretation of our FFGs to study divergent feeding strategies; 25,26 this simply reflects that morphology and thus functionality is highly controlled by phylogeny. The distinction between the areas of morphospace occupied by therapsids and archosauromorphs ( Fig. 1a) represents their fundamentally different feeding priorities, in which archosauromorphs optimised prehension and therapsids optimised comminution. ...
The Triassic (252–201 Ma) marks a major punctuation in Earth history, when ecosystems rebuilt themselves following the devastating Permian-Triassic mass extinction. Herbivory evolved independently several times as ecosystems comprising diverse assemblages of therapsids, parareptiles and archosauromorphs rose and fell, leading to a world dominated by dinosaurs. It was assumed that dinosaurs prevailed either through long-term competitive replacement of the incumbent clades or rapidly and opportunistically following one or more extinction events. Here we use functional morphology and ecology to explore herbivore morphospace through the Triassic and Early Jurassic. We identify five main herbivore guilds (ingestion generalists, prehension specialists, durophagous specialists, shearing pulpers, and heavy oral processors), and find that herbivore clades generally avoided competition by almost exclusively occupying different guilds. Major ecosystem remodelling was triggered multiple times by external environmental challenges, and previously dominant herbivores were marginalised by newly emerging forms. Dinosaur dominance was a mix of opportunity following disaster, combined with competitive advantage in their new world. Terrestrial ecosystems underwent major restructuring through the early Mesozoic, culminating in dinosaur-dominated faunas. Here Singh et al. use jaw morphology to classify tetrapod herbivores into distinct feeding groups and show that their success was shaped by environmental changes and competitive constraints.
... Much of the ecomorphological literature about bovid diets have used linear measurements of craniomandibular features (e.g., Solounias et al. 1995;Spencer 1995;Mendoza and Palmqvist 2006). More recently, several studies have utilized landmark-based, geometric-morphometric analyses to study ungulate jaw shape in relation to diet and function (Raia et al. 2010;Cassini 2013;Cassini et al. 2017;Forrest et al. 2018;Cassini and Toledo 2020). Results of these analyses show that mandibular shape is useful for reconstructing the ecology of extinct taxa. ...
The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology. Our analysis includes data for 100 species of extant bovids, covering all bovid tribes and two dietary classifications. For the first classification with three feeding categories, we found that browsers (including frugivores), mixed feeders, and grazers are moderately well separated using mandibular shape. A finer dietary classification (frugivore, browser, browser-grazer intermediate, generalist, variable grazer, obligate grazer) proved to be more useful for differentiating dietary extremes (frugivores and obligate grazers) but performed equally or less well for other groups. Notably, frugivorous bovids, which belong in tribe Cephalophini, have a distinct mandibular shape that is readily distinguished from all other dietary groups, yielding a 100% correct classification rate from jackknife cross-validation. The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication. Compared to browsers, both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing. Additionally, frugivore mandibles are adapted for selective cropping. Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids.
... In such analyses, a particular phenotype is rather argued to be the result of structural, phylogenetic, functional, and environmental factors [13][14][15]. This was for instance demonstrated for the gross morphology of the appendicular and axial skeleton, with comparative analyses of the forelimb [16] in musteloids and the mandible [17] in ungulates. The extent to which lifestyle, phylogenetic heritage, body size, and other factors influence bone structure at a broad macroevolutionary scale is poorly understood. ...
Background
Mammals are a highly diverse group, with body mass ranging from 2 g to 170 t, and encompassing species with terrestrial, aquatic, aerial, and subterranean lifestyles. The skeleton is involved in most aspects of vertebrate life history, but while previous macroevolutionary analyses have shown that structural, phylogenetic, and functional factors influence the gross morphology of skeletal elements, their inner structure has received comparatively little attention. Here we analysed bone structure of the humerus and mid-lumbar vertebrae across mammals and their correlations with different lifestyles and body size.
Results
We acquired bone structure parameters in appendicular and axial elements (humerus and mid-lumbar vertebra) from 190 species across therian mammals (placentals + marsupials). Our sample captures all transitions to aerial, fully aquatic, and subterranean lifestyles in extant therian clades. We found that mammalian bone structure is highly disparate and we show that the investigated vertebral structure parameters mostly correlate with body size, but not lifestyle, while the opposite is true for humeral parameters. The latter also show a high degree of convergence among the clades that have acquired specialised (non-terrestrial) lifestyles.
Conclusions
In light of phylogenetic, size, and functional factors, the distribution of each investigated structural parameter reveals patterns explaining the construction of appendicular and axial skeletal elements in mammalian species spanning most of the extant diversity of the clade in terms of body size and lifestyle. These patterns should be further investigated with analyses focused on specific lifestyle transitions that would ideally include key fossils.
... In parallel with this, one characteristic of cavioid evolution (as well as in chinchillids), is the presence of many shifts in the evolutionary rate of size change as body size increases (Vucetich et al. 2015;Álvarez et al. 2017). The increase of body size in grazing mammals is a common pattern also recorded in ungulates, in relation to the physiological requirements of the consumption of low-quality foods, with high content of cellulose fibers, such as grasses (Raia et al. 2010;Cassini et al. 2012). This is especially valid for the case of strictly epigean taxa, in which the fastest rates of increase of body size were detected, such as hydrochoerine and dolichotine caviids (Álvarez et al. 2017). ...
Caviomorphs are a mainly South American rodent clade with high taxonomic and ecomorphological diversity. In this study, we combine geometric morphometric, functional, ancestral reconstruction, and macroevolutionary analyses to quantify the magnitude, direction, and rates of shape diversification of the caviomorph mandible, and to explore the morpho-functional implications and potential ecological catalysts of the observed shape changes. The mandible shape was significantly related to habits and size, and had a better fit with an evolutionary model where the main clades occupy distinct adaptive peaks. The morphological evolution of octodontoids is characterized by pulses of rate acceleration , but without reaching high disparity. Such pulses are mainly linked to the acquisition of fossorial specializations, including short and robust mandibles, and the increasement of forces at incisors. Conversely, derived cavioids show slower but continuous shape changes that allowed them to reach the most divergent, grazing morphologies in which slender mandibles with more marked antero-posterior movements for grinding action are favored. Interestingly, the major morphological changes occurred mainly during the early Oligocene and lower late Miocene, two time periods that involved global climatic events and strong changes in the vegetational structure of South America. The evolution of octodontoid and cavioid mandibles seems to be related to the occupation of subterranean and epigean niches, respectively , in the progressively expanded Cenozoic open landscapes of southern South America.
... After controlling for phylogenetic effects, some studies on ungulates mandible design interpreted the correlation between function and morphology as driven by adaptation. This is the case for several mandibular traits such as the coronoid process (Pérez-Barbería and Gordon, 1999) and hypsodonty index (Raia et al., 2010) that were more correlated to dietary habits than to phylogeny in grazing selenodont artiodactyls like mouflons. Therefore, we could expect consistent mandibular shape variations concentrated not only in the angular process but also in the coronoid process correlating both with dietary changes, such as those occurring after weaning and the transition from breastfeeding to a harder diet. ...
Mandibles from separate populations of free-living mouflons (Ovis aries musimon) from Southern Spain, submitted to different ecological conditions, were studied. Searching for ontogenetic shape variations we used geometric morphometrics tools and we explored the use of several mathematical models for describing growth rate variations between populations and sexes. A strong allometry was detected with variations in shape mainly matching with molar and premolar eruption. Mandible shape did not vary significantly with sex nor was sexual size dimorphism detected in adults, whatever the population. By modeling growth we detected differences between populations in all parameters such as the maturity rate describing precocity, and the time it took to reach asymptotic size (varying from 9 up to 18 months). A longer period of growth did not result in a larger asymptotic size, but it led to smaller mandibles. Mouflons with relatively late teeth replacement, lower maturation rate and smaller adult size were those of the population submitted to extreme environmental conditions, like epizootic disease, droughts and ungulate overpopulations. We discuss how a delay in reaching mature size has probably an important subsequent impact on reproductive and life-history traits in this species. Being able to record the effects of density-dependent and density-independent factors, mandibles become a target of interest for ecological and management studies also on mouflons.
... In spite of this, early attempts demonstrated that fossil phylogenies can be incorporated to test macroevolutionary hypotheses, and their inclusion provides stronger statistical power (for early examples see: Finarelli and Flynn, 2006;Meloro et al., 2008). We provided on several occasions examples on how comparative methods can be implemented in macroevolutionary studies incorporating fossils and GMM Raia et al., 2010;Meloro and Slater, 2012;Piras et al., 2012). More recently, the development of new R packages (including geomorph Adams et al., 2019;and RRphylo Raia et al., 2020) allows to detect evolutionary rates with a high degree of accuracy (in spite of phylogenetic fossil uncertainty, e.g., Smaers et al., 2016;Castiglione et al., 2018). ...
Three-dimensional (3D) models of fossil bones are increasingly available, thus opening a novel frontier in the study of organismal size and shape evolution. We provide an example of how photogrammetry can be combined with Geometric Morphometrics (GMM) techniques to study patterns of morphological convergence in the mammalian group of Xenarthra. Xenarthrans are currently represented by armadillos, sloths, and anteaters. However, this clade shows an incredibly diverse array of species and ecomorphotypes in the fossil record, including gigantic ground sloths and glyptodonts. Since the humerus is a weight-bearing bone in quadrupedal mammals and its morphology correlates with locomotor behavior, it provides an ideal bone to gain insight into adaptations of fossil species. A 3D sample of humerii belonging to extant and fossil Xenarthra allowed us to identify a significant phylogenetic signal and a strong allometric component in the humerus shape. Although no rate shift in the evolution of the humerus shape was recorded for any clade, fossorial and arboreal species humerii did evolve at significantly slower and faster paces, respectively, than the rest of the Xenarthran species. Significant evidence for morphological convergence found among the fossorial species and between the two tree sloth genera explains these patterns. These results suggest that the highly specialized morphologies of digging taxa and tree sloths represent major deviations from the plesiomorphic Xenarthran body plan, evolved several times during the history of the group.
... Tooth shape frequently reflects trophic niches that are being explored (Fitzgerald, Winemiller, Sabaj Pérez, & Sousa, 2017;Streelman, Webb, Albertson, & Kocher, 2003). As tooth shape becomes quickly adapted to the different habitats these fishes occupy (Raia, Carotenuto, Meloro, Piras, & Pushkina, 2010), it frequently reflects the type of food a species has become adapted to consume (Davit-Béal, Tucker, & Sire, 2009;Evans, 2013;Huysseune & Sire, 1998;Pasco-Viel et al., 2010;Streelman et al., 2003;Takahashi, Watanabe, Nishida, & Hori, 2007), even within a single generation (Calandra, Labonne, Schulz-Kornas, Kaiser, & Montuire, 2016;French et al., 2017). Several other phenotypic traits have shown functional divergence under ecological disparity, such as the pharyngeal jaw (Magalhaes, Ornelas-Garcıa, Leal-Cardin, Ramírez, & Barluenga, 2015), the gill rakers (Schluter & McPhail, 1992), body shape (Barluenga, Stölting, Salzburger, Muschick, & Meyer, 2006), gut length (Wagner, McIntyre, Buels, Gilbert, & Michel, 2009), mouth position (Burress, Holcomb, & Armbruster, 2016), snout length (Bonato, Burress, & Fialho, 2017), fin length, and body size (Farré, Tuset, Maynou, Recasens, & Lombarte, 2013), in the same line like as tooth size and shape. ...
Tooth shape is used to differentiate between morphologically similar species of vertebrates, including fish. This study aimed to quantify tooth shape of three sympatric species: Haplochromis kamiranzovu, H. insidiae, and H. astatodon endemic to Lake Kivu, whose existing identification criteria are currently only qualitative. A quantitative tooth shape analysis was performed based on digitized tooth outline data with a subsequent elliptic Fourier analysis to test for differences among the three species. We looked at crown shape and size differences within H. kamiranzovu and H. insidiae at geographical, habitat, and gender levels. No comparison at habitat level was done for H. astatodon because it is found only in littoral zone. The analysis revealed significant tooth shape differences among the three species. Haplochromis astatodon had a significantly longer major cusp height and a longer and larger minor cusp than that of H. insidiae. It had also a longer major cusp height and a longer and larger minor cusp than that of H. kamiranzovu. Tooth shape differences of H. kamiranzovu and H. insidiae species were not significantly different between littoral and pelagic fish (p > .05) while differences were significant between southern and northern Lake Kivu populations (p < .05). Tooth sizes in H. kamiranzovu and H. insidiae were significantly different, both in height and width as well as in their ratios, and this was true at sex and geographic levels (p < .05), but not at habitat level (p > .05). Tooth shape was also significantly different with sharp teeth for males compared with females of southern populations versus northern ones. These shape‐ and size‐related differences between sexes suggest differences in the foraging strategies toward available food resources in the lake habitat. Further research should explain the genetic basis of the observed pattern.
... These methods offer cursory insights of relative species positions over the adaptive 'morphospace' landscape, but cannot link any single trait with a specific function, and so cannot explicitly resolve the relevance of particular traits. Univariate analyses, on the other hand, may be misleading in this regard, in cases where traits have developed as compensatory characteristics that evolved to accommodate features that do have a direct link to feeding behaviour ( Raia et al. 2010). Actually, such compensation is also likely to raise, spuriously, the 'goodness-of-fit' of multivariate models as well. ...
Woody plants and grasses are two functionally distinct food groups that pose different mechanical, nutritional, and ecological challenges to herbivores. Accordingly, herbivores have evolved an array of morphological, physiological, and behavioural life history traits that reflect each species’ primary dietary niche. The prevalence of convergences across distantly related groups is evidence that many of these traits are adaptive. Most evaluations are, however, necessarily correlational, and so the functional relevance of many traits is still being debated. The last 2 decades has seen the emergence of larger, more representative, and quantitative datasets, which, along with statistical developments in evolutionary biology, means that a revised set of analyses is warranted. In this chapter we present a collection of updated datasets for almost 100 anatomical and physiological characteristics from 188 species. These data are subjected to phylogenetically-constrained analyses of relationships with diet niches (using %grass in the diet as a niche indicator). Results of these analyses highlight not only the extraordinary amount of convergence within this animal group, but also the constraints that morpho-physiology places on diet niches. To separate correlation from functional significance, we advocate an approach that considers the correlations between traits as part of each species’ “bauplan”, and highlight how this approach has already been used to link trends and outliers with mechanism in various datasets. While some questions about functional relevance require experimental manipulations that will almost certainly never be realized, synergies between experimental and correlational analyses are rapidly changing our understanding of how foraging adaptations, from locating and biting, to chewing and digesting food, have shaped the evolutionary diversification of mammal herbivores.
... Large-sized didelphids (Didelphini) have a different morphological trajectory from both small marsupials and rodents, which suggests that allometry-related effects drive their morphological variation (Cáceres et al., 2016). Even with effects derived from the historical contingency of each taxonomic group, which has a profound influence on the way in which species adapt to particular niches (Raia et al., 2010), we were able to disentangle the role of adaptation of the scapula in these Neotropical small mammalian species. ...
It is not a new concept that marsupials and placentals are distant and distinct clades among mammals. In South America, these animals coexist, occupy similar niches and, in some cases, are similar in appearance. This is especially true with respect to the locomotor categories of smaller rodents belonging to the family Cricetidae or, more specifically, the subfamily Sigmodontinae, compared with the marsupials of the Didelphidae family. In this study, we have investigated both the similarities and the differences between the two clades by examining locomotion-dependent adaptation, a crucial survival mechanism that has affected the morphology of both clades. We applied geometric morphometrics to quantify the shape of the scapula, which is a very adaptable structure. We found similar morphological adaptations between the clades, especially with respect to adaptation to life in trees. Moreover, Didelphidae are influenced by phylogenetic history to a greater extent than Sigmodontinae with regard to variation of scapula shape and allometry. These differences can be explained by the greater degree of body size variation that exists within the Didelphidae. Didelphidae have an ancient evolutionary history in South America compared with the Sigmodontinae, which have undergone a very successful and rapid diversification more recently.
... The position of 'Ceratotherium' advenientis might be affected by the lack of dental data; however, the cranial shape change is much more phylogenetically constrained Pandolfi and Maiorino 2016) than changes in tooth morphologies, which have been driven more by adaptation than by shared ancestry Raia et al. 2010;Pandolfi and Maiorino 2016). The absence of processus postorbitalis on the frontal bone and the development of the nuchal tubercle suggest an affinity with the African species. ...
A new species of Rhinocerotidae (Perissodactyla), ‘Ceratotherium’ advenientis sp. nov., fromthe late Miocene (8.1–7.2 Ma) locality of Cava Gentile, Calabria (Southern Italy), is described. ‘Ceratotherium’ advenientis displays morphological characters close to Rhinocerotina, in particular to dicerotines, and can be distinguished from the late Miocene elasmotheres, teleoceratines and aceratheres recorded in Eurasia and Africa.
The new taxon clearly differs from the European latest Miocene species Dihoplus schleiermacheri, Dihoplus pikermiensis, ‘Dihoplus’ megarhinus and Ceratotherium neumayri, and from the African species Ceratotherium douariense, Ceratotherium? primaevum and Paradiceros mukirii. ‘Ceratotherium’ advenientis also differs from
the Chinese dicerotine Diceros gansuensis and from the extant African species. The new taxon is characterized by peculiar features, in particular in the morphology and dimension of the neurocranial portion, and by having a nuchal crest wider than in the extant African rhinoceroses, C. neumayri, C. douariense, and European latest Miocene species. A cladistic analysis places ‘Ceratotherium’ advenientis in a polytomy with the extant Diceros bicornis, C. neumayri and a small clade composed by C. simum and C. antiquitatis. The
African affinities of the new taxon support the Calabrian-Peloritan arc as a northern extension of the African continental shelf during the late Miocene.
... We found some support for our hypothesis that atlas and axis shape diversity can be explained by ecomorphological factors such as body size, locomotion, and possibly diet. We also found evidence for the influence of past evolutionary history on the shape variation of these vertebrae, which is consistent with previous comparative studies of mammalian cranial (Marroig and Cheverud 2001;Raia et al. 2010;Goswami et al. 2011), appendicular (Polly 2008Martín-Serra et al. 2015), and axial (Randau et al. 2016a) structures at large phylogenetic scales. Previous quantitative analyses indicated that primate atlas shape is associated with locomotion when phylogenetic history is ignored (Manfreda et al. 2006), but a more recent study in felids found that phylogeny influences cervical vertebra shape more than diet or locomotion (Randau et al. 2016a). ...
Mammals flex, extend, and rotate their spines as they perform behaviors critical for survival, such as foraging, consuming prey, locomoting, and interacting with conspecifics or predators. The atlas‐axis complex is a mammalian innovation that allows precise head movements during these behaviors. While morphological variation in other vertebral regions has been linked to ecological differences in mammals, less is known about morphological specialization in the cervical vertebrae, which are developmentally constrained in number but highly variable in size and shape. Here, we present the first phylogenetic comparative study of the atlas‐axis complex across mammals. We used spherical harmonics to quantify 3D shape variation of the atlas and axis across a diverse sample of species, and performed phylogenetic analyses to investigate if vertebral shape is associated with body size, locomotion, and diet. We found that differences in atlas and axis shape are partly explained by phylogeny, and that mammalian subclades differ in morphological disparity. Atlas and axis shape diversity is associated with differences in body size and locomotion; large terrestrial mammals have craniocaudally elongated vertebrae, while smaller mammals and aquatic mammals have more compressed vertebrae. These results provide a foundation for investigating functional hypotheses underlying the evolution of neck morphologies across mammals. This article is protected by copyright. All rights reserved
... Consumers, in turn, may alter the morphology of their grazing apparatus (e.g. teeth, mandibles, tongues) or experience more or less wear on these structures in response to climate change (Raia et al. 2010, Muschick et al. 2011. These morphological and wear responses to climate, which can be provoked by shifts in either the consumer's metabolic demand or in the difficulty of damaging plant tissues (Padilla et al. 1996, Sigwart & Carey 2014, are regularly considered in paleo-ecological studies (e.g. ...
... The position of 'Ceratotherium' advenientis might be affected by the lack of dental data; however, the cranial shape change is much more phylogenetically constrained Pandolfi and Maiorino 2016) than changes in tooth morphologies, which have been driven more by adaptation than by shared ancestry Raia et al. 2010;Pandolfi and Maiorino 2016). The absence of processus postorbitalis on the frontal bone and the development of the nuchal tubercle suggest an affinity with the African species. ...
A new species of Rhinocerotidae (Perissodactyla), ‘Ceratotherium’ advenientis sp. nov., from the late Miocene (8.1–7.2 Ma) locality of Cava Gentile, Calabria (Southern Italy), is described. ‘Ceratotherium’ advenientis displays morphological characters close to Rhinocerotina, in particular to dicerotines, and can be distinguished from the late Miocene elasmotheres, teleoceratines and aceratheres recorded in Eurasia and Africa. The new taxon clearly differs from the European latest Miocene species Dihoplus schleiermacheri, Dihoplus pikermiensis, ‘Dihoplus’ megarhinus and Ceratotherium neumayri, and from the African species Ceratotherium douariense, Ceratotherium? primaevum and Paradiceros mukirii. ‘Ceratotherium’ advenientis also differs from the Chinese dicerotine Diceros gansuensis and from the extant African species. The new taxon is characterized by peculiar features, in particular in the morphology and dimension of the neurocranial portion, and by having a nuchal crest wider than in the extant African rhinoceroses, C. neumayri, C. douariense, and European latest Miocene species. A cladistic analysis places ‘Ceratotherium’ advenientis in a polytomy with the extant Diceros bicornis, C. neumayri and a small clade composed by C. simum and C. antiquitatis. The African affinities of the new taxon support the Calabrian-Peloritan arc as a northern extension of the African continental shelf during the late Miocene.
... To summarize our results, we used variation partitioning (Diniz-Filho & Bini, 2008;Raia et al., 2010;Meloro et al., 2014) to evaluate the singular contribution of four distinct components to litter size, which had a significant impact in the previous analyses: body mass; temperature seasonality and precipitation seasonality (grouped as seasonality); annual precipitation and evapotranspiration (grouped as humidity); and phylogenetic distance. The last was implemented as the first three principal component axes of the phylogenetic distance (that cumulatively explained 98.58% of variation), which was calculated through the 'cophenetic.phylo' ...
Reproductive season and litter size of Brazilian marsupials are reviewed in this chapter. Marsupial newborns are precocious and walk toward the nipples just after birth, for a longer lactation phase. After this obligatory lactation phase, there is the nesting phase where young can disperse from the mother, becoming independent. Breeding seasonality is discussed for marsupials, which appears to be latitude and climate dependent. Other factors relating to the onset and duration of reproductive season are discussed, such as photoperiod, birth synchrony, and semelparity. Litter sizes of marsupials are variable and dependent on biotic and environmental factors. Relevant factors related to this variation are discussed, such as latitude, clime,
isolation, body size, age and habitat.
... To summarize our results, we used variation partitioning (Diniz-Filho & Bini, 2008;Raia et al., 2010;Meloro et al., 2014) to evaluate the singular contribution of four distinct components to litter size, which had a significant impact in the previous analyses: body mass; temperature seasonality and precipitation seasonality (grouped as seasonality); annual precipitation and evapotranspiration (grouped as humidity); and phylogenetic distance. The last was implemented as the first three principal component axes of the phylogenetic distance (that cumulatively explained 98.58% of variation), which was calculated through the 'cophenetic.phylo' ...
Litter size in mammals can be influenced by morphological and environmental variables. Among mammals, the family Didelphidae includes a diverse group of New World endemic marsupials, with extensive records of variation in litter size across species. The aim of this study was to assess factors that influence litter size variation in didelphid marsupials. Phylogenetic least squares regressions were performed between the response variable, litter size, and a set of predictor variables, i.e. body size, pouch presence and geographical, climatic and productivity variables. The results showed that, despite the high phylogenetic signal, litter size is under the influence of body size and climatic variables, having latitude and elevation as their proxies. Body mass showed a positive linear relationship with litter size, although with a non-significant increasing litter size in smaller, pouchless species. Litter size in the warm, resource-rich tropics tended to be small, but females had several litters per year, increasing fecundity. We argue that offspring survivorship at higher latitudes and in cold climates appears to depend on larger litter sizes in didelphid marsupials, because strong seasonality allows time for only a few or one litter per breeding season.
... For comparison, we also performed a nonphylogenetic evaluation using a Procrustes ANOVA (or GLS; Goodall 1991) following Adams (2014a). We found it interesting to compare methodologies that incorporate phylogenetic information in two different ways: Phylogenetic ANOVA as part of the error I and CPO as part of the model (Martins and Hansen 1997;Raia et al. 2010). Procrustes ANOVA and Phylogenetic ANOVA were performed using the geomorph library (Adams et al. 2017) for the software R 3.1.3 ...
Different living mammals have developed a carnivorous habit (e.g., Carnivora, Dasyuridae, Thylacinidae, some Didelphidae). They exhibit different specializations for carnivory; however, they share some characters such as a carnassial molar. Previous studies have correlated the shape of molars with diet using morphometric indices or surface scans. In this work, we used 3D geometric morphometrics to explore the shape of the lower carnassials of 235 specimens corresponding to 71 extant species of Carnivora and six extant species of Marsupialia, both Didelphimorphia and Dasyuromorphia. We statistically estimated the effect of size, diet, and phylogeny on molar shape. All the analyses indicated a higher correlation between diet and molar shape, and a better correlation between molar shape and the position of each species on the phylogeny. Therefore, if we take into account the phylogenetic pattern, we can use molar morphology to infer diet of fossil species. Finally, this work evaluates for the first time, in a quantitative way, which of the lower molars of the Metatheria (m3 or m4) is the best analogue to the m1 of Carnivora; our results indicated the m4 is the best analogue.
... Characteristics of the jaws, teeth, and chewing stroke evolve in concert to enable the exploitation of new food types (Fraser & Rybczynski, 2014). As a functional module, the different components of the feeding apparatus (e.g., jaws, teeth) must evolve and change together to maintain function or produce a change in function such as a transition from one feeding type to another (Raia, Carotenuto, Meloro, Piras, & Pushkina, 2010). For example, modern Equus have evolved high crowned cheek teeth as a means of increasing the lifespan of the teeth in the face of increased abrasive wear. ...
In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche). Some dietary proxies exploit the fact that mammalian teeth experience wear during mastication, due to both tooth‐on‐tooth and food‐on‐tooth interactions. The distribution and types of wear detectible at micro‐ and macroscales are highly correlated with the resource preferences of individuals and, in turn, species. Because methods that quantify the distribution of tooth wear (i.e., analytical tooth wear methods) do so by direct observation of facets and marks on the teeth of individual animals, dietary inferences derived from them are thought to be independent of the clade to which individuals belong. However, an assumption of clade or phylogenetic independence when making species‐level dietary inferences may be misleading if phylogenetic niche conservatism is widespread among mammals. Herein, we test for phylogenetic signal in data from numerous analytical tooth wear studies, incorporating macrowear (i.e., mesowear) and microwear (i.e., low‐magnification microwear and dental microwear texture analysis). Using two measures of phylogenetic signal, heritability (H2) and Pagel's λ, we find that analytical tooth wear data are not independent of phylogeny and failing to account for such nonindependence leads to overestimation of discriminability among species with different dietary preferences. We suggest that morphological traits inherited from ancestral clades (e.g., tooth shape) influence the ways in which the teeth wear during mastication and constrain the foods individuals of a species can effectively exploit. We do not suggest that tooth wear is simply phylogeny in disguise; the tooth wear of individuals and species likely varies within some range that is set by morphological constraints. We therefore recommend the use of phylogenetic comparative methods in studies of mammalian tooth wear, whenever possible. In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche), some of which exploit the fact that mammalian teeth experience wear during mastication. Because methods that quantify the distribution of tooth wear involve direct observation of facets and marks on the teeth of individual animals, dietary niche inferences derived from them are thought independent of the clade to which individuals belong. However, we show that analytical tooth wear data are not independent of phylogeny and suggest that the mammalian feeding apparatus is an evolutionary module in which correlated changes in the teeth and jaws accompanying an evolutionary shift in diet change the ways in which the teeth wear.
... Un questionnement similaire peut être combiné à celui-ci concernant la morphologie de l'alvéole des molaires. Dans la mesure où l'hypsodontie a démontré avoir une influence sur la forme de la mandibule chez les ongulés (Raia et al., 2010), l'acquisition de l'hypsodontie conduit-elle à une modification de la modularité de la mandibule par rapport à des espèces aux molaires brachyodontes ? ...
L’évolution de la dentition des mammifères se caractérise par d’importantes innovations morphologiques comme la mise à occlusion et l’hétérodontie. Parmi rongeurs, dont la formule dentaire est fortement réduite, les arvicolinés possèdent une dentition hautement dérivée, avec des molaires prismatiques et hypsodontes. L’objectif de cette thèse est d’explorer les différentes innovations morphologiques de la dentition au travers des aspects développementaux et adaptatifs. Les méthodes de morphométrie géométrique sont utilisées sur les molaires, les incisives et les mandibules afin d’explorer les dynamiques de développement et d’évolution de la dentition. Un modèle développemental permettant de prédire les proportions de molaires inférieures est examiné et validé à l’échelle de l’ordre des rongeurs ; il peut également être étendu à la prémolaire. De plus, le lien entre la morphologie dentaire, notamment les proportions de molaires, et le régime alimentaire est complexe, un caractère morphologique ne reflétant pas directement une alimentation. Cependant les covariations entre les molaires marquent le mouvement de mastication et ainsi la fonction. Nos résultats confirment une imbrication complexe des contraintes historiques, fonctionnelles et développementales dans l’interprétation des morphologies. Les différentes composantes de la mandibule présentent une organisation hiérarchique complexe. Le développement de la dentition des mammifères est gouverné par des processus similaires mais des mécanismes tels que l’hétérochronie ont pu conduire à une diversification des phénotypes au cours du temps.
... However, studies have found different levels of predictive power depending on the functional and morphological data employed 67,69 . Furthermore, it seems that the capacity to relate the shape of a given mandibular corpus with a particular diet depends on the clade under study [67][68][69] . Several studies have focused on the primate mandible and its functional adaptation to different ingesta (see Ross et al. 70 for a review). ...
The relationship between primate mandibular form and diet has been previously analysed by applying a wide array of techniques and approaches. Nonetheless, most of these studies compared few species and/or infrequently aimed to elucidate function based on an explicit biomechanical framework. In this study, we generated and analysed 31 Finite Element planar models of different primate jaws under different loading scenarios (incisive, canine, premolar and molar bites) to test the hypothesis that there are significant differences in mandibular biomechanical performance due to food categories and/or food hardness. The obtained stress values show that in primates, hard food eaters have stiffer mandibles when compared to those that rely on softer diets. In addition, we find that folivores species have the weakest jaws, whilst omnivores have the strongest mandibles within the order Primates. These results are highly relevant because they show that there is a strong association between mandibular biomechanical performance, mandibular form, food hardness and diet categories and that these associations can be studied using biomechanical techniques rather than focusing solely on morphology.
... Allometry can promote also morphological diversification (Marroig and Cheverud 2005). Allometry played a key role in the ecomorphological diversification within different mammalian clades such as primates, carnivorans, artiodactyls, and rodents (Renaud et al. 2006;Raia 2010, 2015;Raia et al. 2010;). ...
The adaptation to a particular function could directly influence the morphological evolution of an anatomical structure as well as its rates. The humeral morphology of moles (subfamily Talpinae) is highly modified in response to intense burrowing and fully fossorial lifestyle. However, little is known of the evolutionary pathways that marked its diversification in the two highly fossorial moles tribes Talpini and Scalopini. We used two-dimensional landmark-based geometric morphometrics and comparative methods to understand which factors influenced the rates and patterns of the morphological evolution of the humerus in 53 extant and extinct species of the Talpini (22 extant plus 12 extinct) and Scalopini (six extant plus 13 extinct) tribes, for a total of 623 humeri. We first built a synthetic phylogeny of extinct and extant taxa of the subfamily Talpinae based on all the available information from known phylogenies, molecular data, and age ranges of fossil records. We tested for evolutionary allometry by means of multivariate regression of shape on size variables. Evolutionary allometric trajectories exhibited convergence of humeral shape between the two tribes, even when controlling for phylogeny, though a significant differences in the evolutionary rates was found between the two tribes. Talpini, unlike Scalopini, seem to have reached a robust fossorial morphology early during their evolution, and their shape disparity did not change, if it did not decrease, through time. Furthermore, the basal Geotrypus spp. clearly set apart from the other highly fossorial moles, exhibiting a significant acceleration of evolutionary shifts toward higher degree of fossorial adaptation. Our observations support the hypothesis that the evolution of allometry may reflect a biological demand (in this case functional) that constrains the rates of evolution of anatomical structures.
... DFA predicts relatively equal numbers of A. neumayri individuals in each dietary category, including grazing (Table 2). This taxon has a small masseteric fossa and shallow jaw, features suggestive of a more browsing diet (Solounias et al. 1995;Axmacher and Hofmann 1988;Raia et al. 2010). Alcicephalus neumayri, therefore, exhibited dietary patterns atypical of Maragheh ungulates; grazing was uncommon but present in these faunas (Bernor et al. 2014). ...
Giraffids were important components of the late Miocene Maragheh mammalian community. We provide detailed cranial and post-cranial morphological descriptions of six Maragheh giraffids, including Helladotherium duvernoyi, Alcicephalus neumayri, Samotherium boissieri, Samotherium major, Palaeotragus coelophrys and Bohlinia attica, extending the geological range of several taxa. We also describe a new species of Honanotherium (Honanotherium bernori), a taxon smaller than Honanotherium schlosseri. This is the westernmost occurrence of Honanotherium. We create our giraffid faunal list by first identifying each Maragheh specimen to a species, creating a representative specimen/species list. Subsequently, each specimen is described by comparing the Maragheh elements with the corresponding specimens from the type locality where each species is originally known. This method allows for accurate species identifications, and facilitates palaeoecological comparisons between multiple localities using morphological differences in the taxa. For palaeoecology, we evaluate and analyse the dentition of a few adult Maragheh giraffids using combined inner and outer mesowear variables, and find individuals spanning the dietary continuum, but with a polarity towards browsing diets. We describe limb differences among the Palaeotraginae, describe dental and limb similarities between Helladotherium duvernoyi and species of Bohlininae, and discuss the ossicones of Bohlininae. We provide comprehensive and detailed anatomical descriptions of seven giraffid taxa that can facilitate future species identifications and comparisons. © 2016 Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg
... This work also contributes to a growing body of literature that integrates geometric morphometric data into phylogenetic comparative methods (e.g., Klingenberg and Ekau 1996;Rüber and Adams 2001;Clabaut et al. 2007;Meloro et al. 2008;Morgan 2009;Figueirido et al. 2010;Raia et al. 2010;Klingenberg and Marugán-Lobón 2013). ...
... Upper tooth morphology could have been driven more by ecological adaptation than by shared ancestry, whereas cranial shape change is much more phylogenetically constrained . Recent findings suggest that teeth are the most evolutionarily labile structures in the crania of Plio-Pleistocene Rhinocerotini in response to dietary regime, as also suggested by the lowest RV values (a metric comparison of covariation between sets of shape variables) found in the morphological integration between the cranial shape in lateral view and upper teeth shape in occlusal view Raia et al., 2010). ...
eprint link http://www.tandfonline.com/eprint/RMd2IkpggRyTkimPiU8b/full
We describe and figure a well-preserved, large skull of a rhinoceros, NHMUK 36661, collected in 1860 from Upper Siwalik deposits. This specimen can be referred to Rhinoceros platyrhinus. Comparison with the type material of R. platyrhinus revealed that several specimens previously referred to this taxon, including the lectotype, should instead be assigned to Rhinoceros sp. (potentially R. sivalensis or R. unicornis). Therefore, we here provide new detailed cranial and dental characters for R. platyrhinus, which is currently known only by a few specimens collected from a restricted area of northern India. We suggest that the generic name Punjabitherium erected for R. platyrhinus represents a junior synonym of Rhinoceros due to the morphological affinities of NHMUK 36661 with R. unicornis. A principal component analysis and a cluster analysis confirmed the morphological similarities between R. platyrhinus and R. unicornis. Rhinoceros platyrhinus represents the largest rhinocerotine species in Eurasia and is characterized by a long skull and high-crowned teeth, suggesting that it was a grazer rather than a mixed feeder such as R. unicornis. This is supported by a cluster analysis on the upper teeth. The progressive increase in aridity from ca. 12 Ma to Recent in northern India could have affected the dietary regime of R. platyrhinus towards to a more grazer-like diet.
... Anatomical features of the mandible and teeth in ungulates are evidently related to the way they feed as well as the type of food a particular species prefers. When this subject is analyzed in the light of the even-toed ungulates and the deer, it should be concluded that there is a strong correlation between the mandible size and body mass (Raia et al. 2010). For that reason, it can be indirectly concluded that there is a correlation between the mandible and the body or carcass mass. ...
The study material included 152 mandibles of female fallow deer aged 3 to 12. Each mandible was characterized by 15 measurements. Based on the Principal Components Analysis it was concluded that the size and dimensional constitution of the mandible change with age. The following parameters are subjected to most significant changes: total length, middle height of the ramus. Additionally, the method indicated that there is a moderate interdependency between the mandibular parameters and an eviscerated carcass mass. Pearson's correlation coefficient allowed for determining moderate correlations between the carcass mass, mandible total length, breadth of the third molar and middle height of the ramus.
... We employed variation partitioning (Diniz-Filho and Bini 2008; Raia et al. 2010;Meloro et al. 2014a) to evaluate the singular contribution to skull shape variance of four distinct components: taxonomy (described by the categorical variable ''species''), size (described by lnCS), climate (described by the nineteen bioclimatic indices) and competition (described by the three variables of size, diet and biome overlap between the species). These factors are all considered as predictors (X) of skull shape (Y, described by the 54 shape variables, 2n -4 where n is the number of landmarks, Rohlf and Slice 1990) into multiple multivariate regression models. ...
Species morphological changes can be mutually influenced by environmental or biotic factors, such as competition. South American canids represent a quite recent radiation of taxa that evolved forms very disparate in phenotype, ecology and behaviour. Today, in the central part of South America there is one dominant large species (the maned wolf, Chrysocyon brachyurus) that directly influence sympatric smaller taxa via interspecific killing. Further south, three species of similar sized foxes (Lycalopex spp.) share the same habitats. Such unique combination of taxa and geographic distribution makes South American dogs an ideal group to test for the simultaneous impact of climate and competition on phenotypic variation. Using geometric morphometrics, we quantified skull size and shape of 431 specimens belonging to the eight extant South American canid species: Atelocynus microtis, Cerdocyon thous, Ch. brachyurus, Lycalopex culpaeus, L. griseus, L. gymnocercus, L. vetulus and Speothos venaticus. South American canids are significantly different in both skull size and shape. The hypercarnivorous bush dog is mostly distinct in shape from all the other taxa while a degree of overlap in shape—but not size—occurs between species of the genus Lycalopex. Both climate and competition impacts interspecific morphological variation. We identified climatic adaptations as the main driving force of diversification for the South American canids. Competition has a lower degree of impact on their skull morphology although it might have played a role in the past, when canid community was richer in morphotypes.
Electronic supplementary material
The online version of this article (doi:10.1007/s11692-015-9362-3) contains supplementary material, which is available to authorized users.
... Besides the issues of how to properly analyze both GM and FEA data, another problem arises when carrying out any biological study containing several species, due to the phy-logenetic structure of the data (i.e., non-independence problem). Some approaches have been proposed to take into account phylogeny such as the application of phylogenetic generalized least squares models (PGLS) to fit regressions between matrices of functional/ecological variables and shape variables (R€ uber and Adams, 2001;Clabaut et al., 2007;Meloro et al., 2008;Nogueira et al., 2009;Raia et al., 2010;Piras et al., 2013), the use of phylogeneticindependent contrasts estimated for each shape variable before associating them with contrasts derived from functional/ecological variables applying either partial least squares (Klingenberg and Ekau, 1996) or multivariate regressions (Figueirido et al., 2010) and the correlation between morphometric, functional/ecological, and phylogenetic matrices (Harmon et al., 2005;Young et al., 2007;Ast ua, 2009;Monteiro and Nogueira, 2010). In the present study, PGLS was preferred because this method is considered more informative and powerful than other methods (e.g., distance matrix correlation) (Peres-Neto and Jackson, 2001). ...
Objective:
The aim was to analyze the relationship between scapular form and function in hominoids by using geometric morphometrics (GM) and finite element analysis (FEA).
Methods:
FEA was used to analyze the biomechanical performance of different hominoid scapulae by simulating static postural scenarios. GM was used to quantify scapular shape differences and the relationship between form and function was analyzed by applying both multivariate-multiple regressions and phylogenetic generalized least-squares regressions (PGLS).
Results:
Although it has been suggested that primate scapular morphology is mainly a product of function rather than phylogeny, our results showed that shape has a significant phylogenetic signal. There was a significant relationship between scapular shape and its biomechanical performance; hence at least part of the scapular shape variation is due to non-phylogenetic factors, probably related to functional demands.
Discussion:
This study has shown that a combined approach using GM and FEA was able to cast some light regarding the functional and phylogenetic contributions in hominoid scapular morphology, thus contributing to a better insight of the association between scapular form and function. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
Mesotheriidae were small to medium‐sized native South American ungulates. Mesotheriids radiated from the early Oligocene epoch to the early–middle Pleistocene, in two subfamilies: Trachytheriinae and Mesotheriinae. Beyond the conspicuous fossil record, little is known about mesotheriid palaeobiology, and particularly, the dietary habits. To date, different studies suggest grazing habits, similar to some extant ungulates, but recent contributions are challenging this vision. Here, we explore dietary preferences in mesotheriids, focusing on food intake and oral processing strategies. We performed a shape analysis of the snout and reconstructed ancestral shapes to assess evolutionary trends within the clade. Also, we considered other morphological variables of the masticatory apparatus to perform a functional characterization. We recognized three snout configurations: Trachytherus, ‘Intermediate’ and Mesotherium morphotypes that can be associated with different food intake capabilities and, considering other morphological proxies, with the consumption of different food items. Taking into account palaeoenvironmental conditions, the evolution of the masticatory apparatus is interpreted in the context of a consumption gradient from coarse and tough foods (roots, tubers, tough leaves) to grasses. We propose that during the ecomorphological evolution of mesotheriids, an initial phase took place during the late Oligocene and Miocene, consisting of diversification and specialization for consumption of hard‐to‐break food items. A second phase began incipiently during the late Miocene, and became well‐defined during the Pliocene and Pleistocene, characterized by an ecomorphological displacement towards grazing habits. Inferred dietary habits in Mesotheriidae could provide light on palaeoecological evolution and niche partitioning within South American herbivorous mammalian communities.
Animals with large differences in body size between adults and juveniles will often exhibit differences in behavior through ontogeny, and these behavioral differences can sometimes have direct effects on skeletal morphology. Scapula shape has been shown in several groups to be highly influenced by function and in some groups to be a good indicator of body size. Megalonyx and Paramylodon, two of the most common and widespread of the North American Plio-Pleistocene giant ground sloths, had overlapping temporal and geographic ranges. However, they have few co-occurrences in the fossil record. In this study, the scapulae of juvenile and adult Megalonyx jeffersonii and Paramylodon harlani were analyzed using geometric morphometrics and compared with those of the two genera of modern tree sloths, Bradypus and Choloepus. The ground sloths have significantly different scapula shapes from each other, as do the tree sloths. The scapula shapes between juveniles and adults of each genus are also significantly different from each other, with the scapulae of the juveniles of each species more circular in appearance than the more ovoid ones in adults. All four genera show significant allometry, but it is more apparent in adults than juveniles. However, there is no difference in nonallometric shape between adults and juveniles or between each pair of genera. The ground sloths exhibit similar changes in ontogeny to those observed in modern sloths, indicating that ground sloth juveniles may have engaged in similar behaviors to those of modern sloths, such as clinging to their mothers for transportation. Ground sloth juveniles also possess morphological traits that have been linked with semiarboreal behaviors.
Convergent evolution is often reported in the mammalian order Carnivora. Their adaptations to particularly demanding feeding habits such as hypercarnivory and durophagy (consumption of tough food) appear to favour morphological similarities between distantly related species, especially in the skull. However, phylogenetic effect in phenotypic data might obscure such a pattern. We first validated the hypotheses that
extant hypercarnivorous and durophagous large carnivorans converge in mandibular shape and form (size and shape). Hypercarnivores generally exhibit smaller volumes of the multidimensional shape and form space than their sister taxa, but this pattern is significantly different from random expectation only when hunting behaviour categorisations are taken into account. Durophages share areas of the morphospace, but this seems to be due to factors of contingency. Carnivorans that hunt in pack exhibit incomplete convergence while even stronger similarities occur in the mandible shape of solitary hunters due to the high functional demands in killing the prey. We identified a stronger phylogenetic signal in mandibular shape than in size. The quantification of evolutionary rates of changes suggests that mandible shape of solitary hunters evolved slowly when compared with other carnivorans. These results consistently indicate that the need for a strong bite force and robust mandible override sheer phylogenetic effect in solitary hunters.
Phylogenetic comparative methods are one of the most important parts of the morphometric toolkit for studies of morphological evolution. The assessment of repeated independent events of evolution of phenotypic and associated ecological-functional traits is still a starting point for the study of adaptation, but modern comparative approaches go beyond correlative methods, allowing for the modeling of evolutionary scenarios and analyses of trait evolution patterns. The evidence for adaptive change due to ecological diversification is stronger (even if still circumstantial) if models that predict increases in diversification rate fit the data well and the morphological changes are associated with ecological and functional changes. A large body of literature is dedicated to methodological and theoretical aspects of comparative methods, but in the context of univariate traits. On the other hand, biological shape is a complex trait, and morphometric data is essentially multivariate. Whereas most comparative methods allow for direct multivariate extensions, dimension reduction is an almost certain requirement due to the high dimensionality of morphometric data sets and the large number of evolutionary parameters that need to be estimated by comparative methods. Objective methods with considerable statistical support to determine data dimensionality exist, but the applied literature usually relies on subjective criteria to assess how many shape dimensions should be retained. The most appropriate calculation and interpretations of principal components, the most popular dimension reduction method, are also topics that should be considered more carefully in applications. The maturity of comparative methods and the development of model-based approaches linking macroevolutionary patterns and microevolutionary processes provide an exciting perspective for the study of morphological evolution.
The use of mesowear to infer diets of extinct species is fast becoming widespread in palaeoecological studies. Nevertheless, traditional mesowear analyses suffer from a specimen number limitation, in that a minimum number of specimens identified to the species level is necessary to make accurate dietary predictions. This is problematic in many fossil African antelope (Mammalia: Bovidae) assemblages,
where isolated teeth cannot always be assigned to species. Hereweexplore the possibility of using simple dental metrics to predict diets on the basis of individual teeth as well as gnathic rows using linear discriminant function analyses.We find that browsers are accurately classified at both the individual and species levels, across all models and tooth positions. Mixed feeders and grazers are classified
accurately only sometimes, and this is probably a reflection of the more limited sample size of larger bodied species in our study. Body size was a highly significant predictor of the inaccurate classifications obtained in our models, with larger bodied species tending to grazing classifications and smaller bodied species browsing classifications. Nevertheless, the models correctly classify the majority of specimens we examined to their correct trophic group, as determined through stable isotope analyses or as defined through the literature. The methods outlined hold some promise for determining the diets of isolated fossil specimens unassigned to species in a simple manner and, when used in conjunction with other palaeodietary and palaeoecological proxies, may help determine palaeoenvironments more accurately.
Domestication of vertebrates is based on the understanding of the needs of animals in their natural environment and the success of this domestication throughout human history is largely dependent on the knowledge of their feeding behaviour. The aim of this volume is to provide advanced students and researchers with a review of current knowledge of feeding in domestic mammals and birds. The first few chapters cover feeding structures and mechanisms in birds and mammals, while the rest of the book presents chapters on feeding behaviour in particular species. The scope is wide, covering not only ruminants, pigs and poultry, but also more specifically horses, rabbits and ostrich. Contributors include leading research workers from Europe, the USA, Australia and South Africa. This book will be of significant interest to researchers in animal physiology and nutrition.
Kangaroos and ungulates are similar for most variables examined. Differences are mainly in molar widths, occipital height and muzzle width. -from Author
Modern ruminant species have traditionally been placed in three broad dietary categories (browsers, grazers and intermediates) based on their observed feeding habits. Shape analysis of premaxillary outlines of 31 species of ruminants shows that their premaxillae differ according to their dietary category. Browsers have pointed premaxillae and grazers square ones. Intermediate feeders have intermediate outlines.
The Miocene giraffid Samotherium boissieri has always been viewed as a specialized browser similar to the modern okapi, Okapia johnstoni . However, the premaxillary shape of S. boissieri falls very close to the mean of the grazers and is most similar to that of the African buffalo ( Syncerus caffer ), a committed grazer.
Quantitative analyses of the microscopic wear patterns on the molars reveal significant differences between three modern species from the three dietary groups. S. boissieri has more microscopic scratches on its teeth than either the modern giraffe Giraffa camelopardalis (a browser) or Grant's gazelle Gazella granti (an intermediate feeder). In this respect, it is indistinguishable from the wildebeest Connochaetes taurinus which is a committed grazer.
Both of these analyses suggest that this extinct giraffid was a grazer, although we cannot rule out the possibility that it was an intermediate feeder. It was definitely not a specialized browser as are both living members of the Giraffidae.
The purpose of this data set was to compile body mass information for all mammals on Earth so that we could investigate the patterns of body mass seen across geographic and taxonomic space and evolutionary time. We were interested in the heritability of body size across taxonomic groups (How conserved is body mass within a genus, family, and order?), in the overall pattern of body mass across continents (Do the moments and other descriptive statistics remain the same across geographic space?), and over evolutionary time (How quickly did body mass patterns iterate on the patterns seen today? Were the Pleistocene extinctions size specific on each continent, and did these events coincide with the arrival of man?). These data are also part of a larger project that seeks to integrate body mass patterns across very diverse taxa (NCEAS Working Group on Body Size in Ecology and Paleoecology: linking pattern and process across space, time, and taxonomic scales). We began with the updated version of D. E. Wilson and D. M. Reeder's taxonomic list of all known Recent mammals of the world (N = 4629 species) to which we added status, distribution, and body mass estimates compiled from the primary and secondary literature. Whenever possible, we used an average of male and female body mass, which was in turn averaged over multiple localities to arrive at our species body mass values. The sources are line referenced in the main data set, with the actual references appearing in a table within the metadata. Mammals have individual records for each continent they occur on. Note that our data set is more than an amalgamation of smaller compilations. Although we relied heavily on a data set for Chiroptera by K. E. Jones (N = 905), the CRC handbook of Mammalian Body Mass (N = 688), and a data set compiled for South America by P. Marquet (N = 505), these represent less than half the records in the current database. The remainder are derived from more than 150 other sources. Furthermore, we include a comprehensive late Pleistocene species assemblage for Africa, North and South America, and Australia (an additional 230 species). “Late Pleistocene” is defined as approximately 11 ka for Africa, North and South America, and as 50 ka for Australia, because these times predate anthropogenic impacts on mammalian fauna. Estimates contained within this data set represent a generalized species value, averaged across sexes and geographic space. Consequently, these data are not appropriate for asking population-level questions where the integration of body mass with specific environmental conditions is important. All extant orders of mammals are included, as well as several archaic groups (N = 4859 species). Because some species are found on more than one continent (particularly Chiroptera), there are 5731 entries. We have body masses for the following: Artiodactyla (280 records), Bibymalagasia (2 records), Carnivora (393 records), Cetacea (75 records), Chiroptera (1071 records), Dasyuromorphia (67 records), Dermoptera (3 records), Didelphimorphia (68 records), Diprotodontia (127 records), Hydracoidea (5 records), Insectivora (234 records), Lagomorpha (53 records), Litopterna (2 records), Macroscelidea (14 records), Microbiotheria (1 record), Monotremata (7 records), Notoryctemorphia (1 record), Notoungulata (5 records), Paucituberculata (5 records), Peramelemorphia (24 records), Perissodactyla (47 records), Pholidota (8 records), Primates (276 records), Proboscidea (14 records), Rodentia (1425 records), Scandentia (15 records), Sirenia (6 records), Tubulidentata (1 record), and Xenarthra (75 records).
The independent acquisition of high-crowned cheek teeth (hypsodonty) in several ungulate lineages (e.g., camels, equids, rhinoceroses) in the early to middle Miocene of North America has classically been used as an indication that savanna vegetation spread during this time. Implicit in this interpretation is the untested assumption that hypsodonty was an evolutionary response to feeding in open habitats, either due to a change in food source (from browse to graze) or to increased incorporation of airborne grit in the diet. I examined the adaptive explanation for hypsodonty in equids using criteria pertaining to process and pattern of adaptations set up in the comparative-methods literature. Specifically, I tested whether hypsodonty appeared coincident with or just after the spread of open, grass-dominated habitats in the Great Plains of North America. Phytolith (plant opal) analysis of 99 phytolith assemblages extracted from sediment samples from Montana/Idaho, Nebraska/Wyoming, and Colorado were used to establish the first continuous record of middle Eocene-late Miocene vegetation change in the northern to Central Great Plains. This record was compared with the fossil record of equids from the same area in a phylogenetic framework. The study showed that habitats dominated by C3 grasses were established in the Central Great Plains by early late Arikareean (≥21.9 Ma), at least 4 Myr prior to the emergence of hypsodont equids (Equinae). Nevertheless, the adaptive hypothesis for hypsodonty in equids could not be rejected, because the earliest savanna-woodlands roughly co-occurred with members of the grade constituting the closest outgroups to Equinae ("Parahippus") showing mesodont dentition. Explanations for the slow evolution of full hypsodonty may include weak and changing selection pressures and/or phylogenetic inertia. These results suggest that care should be taken when using functional morphology alone to reconstruct habitat change.
This article considers the statistical issues relevant to the comparative method in evolutionary biology. A generalized Linear model (GLM) is presented for the analysis of comparative data, which can be used to address questions regarding the relationship between traits or between traits and environments, the rate of phenotypic evolution, the degree of phylogenetic effect, and the ancestral state of a character. Our approach thus emphasizes the similarity among evolutionary questions asked in comparative studies. We then discuss ways of specifying the sources of error involved in a comparative study (e.g., measurement error, error due to evolution along a phylogeny, error due to misspecification of a phylogeny) and show how the impact of these sources of error can be taken into account in a comparative analysis. In contrast to most existing phylogenetic comparative methods, our procedure offers substantial flexibility in the choice of microevolutionary assumptions underlying the statistical analysis, allowing researchers to choose assumptions that are most appropriate for their particular set of data and evolutionary question. In developing the approach, we also propose novel ways of incorporating within-species variation and/or measurement error into phylogenetic analyses, of estimating ancestral states, and of considering both continuous (quantitative) and categorical (qualitative or ''state'') characters in the same analysis.
Superimposition methods for comparing configurations of landmarks in two or more specimens are reviewed. These methods show
differences in shape among specimens as residuals after rotation, translation, and scaling them so that they align as well
as possible. A new method is presented that generalizes Siegel and Benson's (1982) resistant-fit theta-rho analysis so that
more than two objects can be compared at the same time. Both least-squares and resistant-fit approaches are generalized to
allow for affine transformations (uniform shape change). The methods are compared, using artificial data and data on 18 landmarks
on the wings of 127 species of North American mosquitoes. Graphical techniques are also presented to help summarize the patterns
of differences in shape among the objects being compared.
The Caune de l'Arago Cave (southern France) has yielded one of the best preserved and best documented sedimentary successions of the European Middle Pleistocene (Oxygen Isotopic Stages 14 to 12). Herbivorous ungulates (horse, reindeer, red deer, fallow deer, bison, musk ox, argali, and tahr) are well represented in the three major stratigraphic units CM1, CM2, and CM3. CM1 and CM3 correspond to cold and dry climate and CM2 represents temperate and humid environmental conditions. Dental microwear and mesowear analyses were performed for the ungulates from CM1-3 to test whether these methods of dental wear evaluation were suitable for detecting climate-driven changes in the dietary resources of the Arago ungulate community. We found that both dental mesowear and microwear indicate dietary traits and their relationship to climatic conditions as reflected by vegetation cover and community structure. In all units, even if some species seem to share habitats or resources, it appears that the overlap in their feeding ecology is very low. The CM1 and CM3 units, where pollen analysis indicates that the climate was cold and dry, show the lowest diversity in dietary traits. The CM2, where climate is known to be more temperate and humid, the spectrum of dietary traits is large - grazers, browsers, and mixed feeders are present.
The use of geometric morphometrics in investigating morphological correlates of feeding habits in large land mammals was investigated. Mandibles of twenty‐one species of to both living and extinct land carnivores, whose feeding habits are well established, were analyzed to investigate the correlation between mandible shape and diet type. Geometric morphometrics has a high predictive value in assessing mammalian diet, and therefore represents an important tool for investigating feeding habits in extinct mammals. By pooling living and extinct species, feeding habits of the latter can be readily determined.
The analysis of fossil ungulate cheek teeth has long been one of the main sources of information about the terrestrial environments of the Cenozoic, but the methods used to extract this information have been either imprecise or prohibitively laborious. Here we present a method based on relative facet development that is quantitative, robust, and rapid. This method, which we term mesowear analysis, is based on the physical properties of ungulate foods as reflected in the relative amounts of attritive and abrasive wear that they cause on the dental enamel of the occlusal surfaces. Mesowear was recorded by examining the buccal apices of molar tooth cusps. Apices were characterized as sharp, rounded, or blunt, and the valleys between them either high or low. The method has been developed only for selenodont and trilophodont molars, but the principle is readily extendable to other crown types. Mesowear analysis is insensitive to wear stage as long as the very early and very late stages are excluded. Cluster analysis of the mesowear variables produces clusters reflecting four main groups from abrasion-dominated to attrition-dominated: grazers, graze-dominated mixed feeders, browse-dominated mixed feeders, and browsers. Most of the relatively few apparent anomalies are explained by more detailed dietary information. Mesowear analysis provides resolution within the main dietary classes and the clustering is virtually identical with and without the index of hypsodonty. Discriminant analysis using all mesowear variables and hypsodonty
A new and greatly simplified methodology for the assessment of the dietary adaptations of living and fossil taxa has been developed which allows for microwear scar topography to be accurately analyzed at low magnification (35×) using a standard stereomicroscope. In addition to the traditional scratch and pit numbers, we introduce four qualitative variables: scratch texture, cross scratches, large pits, and gouges, which provide finer subdivisions within the basic dietary categories. A large extant comparative ungulate microwear database (809 individuals; 50 species) is presented and interpreted to elucidate the diets of extant ungulates. We distinguish three major trophic phases in extant ungulates: traditional browsers and grazers, two phases represented by only a few species, and a browsing-grazing transitional phase where most species fall, including all mixed feeders. There are two types of mixed feeders: seasonal or regional mixed feeders and meal-by-meal mixed feeders. Some species have results that separate them from traditional members of their trophic group; i.e., browsers, grazers, and mixed feeders. Duikers are unique in spanning almost the entire dietary spectrum. Okapia, Tapirus, Tragulus, and Moschus species have wear similar to duikers. Proboscideans fall in the browsing-grazing transitional phase, as do the two suids studied. The latter differ from each other by their degree of rooting. Archaic fossil equids spanning the supposed browsing-grazing transition were compared to extant ungulates. Two major clusters are discerned: (1) Hyracotherium has microwear most similar to that of the duiker Cephalopus silvicultor and was a fruit/seed eating browser. (2) Mesohippus spp., M. bairdii, Mesohippus hypostylus, Meso-Miohippus (a transitional form larger than M. bairdii), Parahippus spp., and Merychippus insignis differ from Hyracotherium and are most similar to the extant Cervus canadensis. Group (2) is characterized by fine scratches which are the result of C3 grazing, an initial phase of grazing in equids which most likely did not occur in open habitats. Finer differentiation of group (2) diets shows a dietary change in the expected direction (toward the incorporation of more grass in the diet) and follows the expected evolutionary transition from the Eocene to the Oligocene and early Miocene. Consequently, these equid taxa are reconstructed here as mixed feeders grazing on forest C3 grasses. The finer dietary differentiation shows a progressive decrease in the number of scratches and pits. Mesohippus has the most pits and scratches, followed by Parahippus, and then Merychippus (which has the least). The taxon incorporating the most grass into its dietary regime in this array is Merychippus. In Mesohippus-Parahippus versus Merychippus, differences in tooth morphology are major but microwear differences are slight.
Mandibular corpus shape variability was investigated in seven families of both extant and extinct mammalian carnivores using two-dimensional landmarks and geometric morphometric methods. The landmark configuration represents the position of the fourth premolar relative to the canine and the lower carnassial, plus related features of the corpus profile. Between families, the corpus manifests differences in shape and allometry. Additionally, families differ in the relationship between the angle (a carnassial trait proxy for hypo-hypercarnivory) and mandibular corpus shape. When phylogenetic relatedness is taken into account using five different phylogenies as covariates, interspecific scaling is still present but the relationship between and corpus shape is no longer significant. This suggests that the allometric relationship reflects the physical constraints of mastication, resulting in relatively increased corpus depth with higher loads. In contrast, the angle is related to corpus curvature and this relationship is phylogenetically constrained by the reduction of the molar battery in large feliforms early during the carnivore radiation. In summary, large fissiped carnivores show extensive functional convergence in mandibular corpus shape although the evolutionary routes leading to such functional convergence are different. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 832–845.
The debate over the relative importance of natural selection as compared to other forces affecting the evolution of organisms is a long-standing and central controversy in evolutionary biology. The theory of adaptationism argues that natural selection contains sufficient explanatory power in itself to account for all evolution. However, there are differing views about the efficiency of the adaptation model of explanation. If the adaptationism theory is applied, are energy and resources being used to their optimum? This book presents an up-to-date view of this controversy and reflects the dramatic changes in our understanding of evolution that have occurred in the last twenty years. The volume combines contributions from biologists and philosophers, and offers a systematic treatment of foundational, conceptual, and methodological issues surrounding the theory of adaptationism. The essays examine recent developments in topics such as phylogenetic analysis, the theory of optimality and ess models, and methods of testing models.
We propose a new method to estimate and correct for phylogenetic inertia in comparative data analysis. The method, called phylogenetic eigenvector regression (PVR) starts by performing a principal coordinate analysis on a pairwise phylogenetic distance matrix between species. Traits under analysis are regressed on eigenvectors retained by a broken-stick model in such a way that estimated values express phylogenetic trends in data and residuals express independent evolution of each species. This partitioning is similar to that realized by the spatial autoregressive method, but the method proposed here overcomes the problem of low statistical performance that occurs with autoregressive method when phylogenetic correlation is low or when sample size is too small to detect it. Also, PVR is easier to perform with large samples because it is based on well-known techniques of multivariate and regression analyses. We evaluated the performance of PVR and compared it with the autoregressive method using real datasets and simulations. A detailed worked example using body size evolution of Carnivora mammals indicated that phylogenetic inertia in this trait is elevated and similarly estimated by both methods. In this example, Type I error at α = 0.05 of PVR was equal to 0.048, but an increase in the number of eigenvectors used in the regression increases the error. Also, similarity between PVR and the autoregressive method, defined by correlation between their residuals, decreased by overestimating the number of eigenvalues necessary to express the phylogenetic distance matrix. To evaluate the influence of cladogram topology on the distribution of eigenvalues extracted from the double-centered phylogenetic distance matrix, we analyzed 100 randomly generated cladograms (up to 100 species). Multiple linear regression of log transformed variables indicated that the number of eigenvalues extracted by the broken-stick model can be fully explained by cladogram topology. Therefore, the broken-stick model is an adequate criterion for determining the correct number of eigenvectors to be used by PVR. We also simulated distinct levels of phylogenetic inertia by producing a trend across 10, 25, and 50 species arranged in "comblike" cladograms and then adding random vectors with increased residual variances around this trend. In doing so, we provide an evaluation of the performance of both methods with data generated under different evolutionary models than tested previously. The results showed that both PVR and autoregressive method are efficient in detecting inertia in data when sample size is relatively high (more than 25 species) and when phylogenetic inertia is high. However, PVR is more efficient at smaller sample sizes and when level of phylogenetic inertia is low. These conclusions were also supported by the analysis of 10 real datasets regarding body size evolution in different animal clades. We concluded that PVR can be a useful alternative to an autoregressive method in comparative data analysis.
The radiation of ruminant artiodactyls, bovids in particular, that characterized the latter part of the Neogene, appeared to be at the expense of the hindgut-fermenting ungulates that showed a corresponding decrease in diversity and total numbers. However, climatic and vegetational changes may have been the cause for this decline, rather than direct competition with ruminants. The Tertiary change in relative diversity of hindgut fermenters, from initially more than 50% of the ungulate fauna to only 25-30%, occurred during the late Eocene and early Oligocene in higher latitudes, and in the mid-Miocene in lower latitudes. In both cases, this change was correlated with a climatic shift from low to high seasonality. Subsequently, the relative abundance of hindgut fermenters remained more or less constant in all latitudes until the end of the Pleistocene. The radiation of the ruminant artiodactyls appears to have taken place at the expense of less specialized selenodont artiodactyls that were the first artiodactyls to show an increase in diversity after the late Eocene reduction in numbers of hindgut fermenters. -from Author
The so-called 'inefficiency' of the perissodactyls, resulting from the evolution of a cecal site of fermentation, arises because the strategy of selecting fibrous herbage was developed early in their evolution. The ruminant artiodactyls did not adopt this sort of diet until they were of a sufficiently large body size for a rumen fermentation site to be physiologically possible. It appears that body size at the time of the adoption of a fibrous diet is the critical factor in determining the type of digestive system that will be evolved. Cecal digestion is in fact the superior adaptation for dealing with high fiber content herbage, provided that intake is not limited by the actual quantity of herbage available. The Equidae continued to be successful in the face of the radiation of ruminant artiodactyls because they could maintain themselves on herbage more fibrous than could be tolerated by a ruminant of similar body size.