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Parallel patterns and trends in functional structures in island mammals
Abstract
Endemic mammalian species on islands are generally known to have followed a different evolutionary pathway than their mainland relatives. General patterns, such as body size trends, have been described regularly. However, most island mammal species are unique and each of them is adapted to a specific local niche as part of an equally specific ecological assemblage. Therefore, comparing island species across taxa, islands and time is inherently dangerous without understanding the adaptational value of the studied feature in the compared taxa and without taking the ecological setting of the taxa into account. In this contribution, general and recurring patterns are described per taxon. Some features, like body mass change and sturdy limbs, are relatively general, whereas most features, like bone fusions and change of orbital axis, occur only in a very few taxa. Some features are even contradictory, such as brain size and degree of hypsodonty, with each taxon having its own particular design. In conclusion, general patterns are more often than not just trends and need to be applied with caution.
... Particularly, extinct insular endemics have aroused special interest, mainly because their biology and ecology were not perturbed by anthropogenic actions [12]. In addition to size shifts, extinct insular endemics are characterized, in general, by changes in postcranial bones (proportions, length, robustness, articulation loss), dentition alterations (higher degree of hypsodonty, loss of premolars, more complex enamel pattern), as well as modifications in skull and brain (absence of pneumatization, short muzzles, brain and sense organs reduction) [13]. However, such results are biased (overrepresented by large mammals), and the eco-evolutionary adaptations of small mammals to insular regimes are relatively less known. ...
... Taxonomic details (species and family), geographic distribution and geologic age of the assessed ochotonids are provided in Figure 1. Paleobiological information of insular leporids or micromammalian taxa (rodents and soricids) was also gathered for comparative purposes [13,37]. With the same objective, material of extant lagomorph species (housed at the Hungarian Natural History Museum) was also assessed. ...
... Ochotonids show clear eco-evolutionary respones to insular regimes [35]. However, when they are compared to other small insular taxa, the patterns are not so homogenous (Figure 2) [13]. Comparatively, extinct ochotonids are the small mammals from Mediterranean area that have been best paleobiologically described. ...
Fossil biotas provide an opportunity to explore eco-evolutionary adaptations to insular regimes not subjected to the anthropogenic perturbations. Historically, these studies have been biased towards large-sized taxa, and less efforts has been devoted to small ones. For this reason, the present study reviews the general and specific biological responses described in extinct insular ochotonids (Ochotonidae, Lagomorpha) from the Mediterranean Islands (Miocene-Holocene), given the last cutting-edge investigations. Parallel biological trends have been observed in these species, regarding an increase of adult body size, teeth modifications (e.g. higher hypsodonty), slow-gear lifestyle with new locomotion skills (related to digging, climbing or leaping), as well as a slow life history. Most of these features are also noticed in other extinct insular micromammals and large-sized species. Although a single ochotonid dwells in true insular environments at present, the future climate change will push them to inhabit top of mountains (ecological islands). The present paper provides useful baseline data (evolutionary history of the family, biological abilities or responses to insularity) for the design and implementation of innovative and effective management actions.
... ropalophorus, C. sp. (size II), C. cretensis; Van der Geer, 2014aVan der Geer et al., 2011). In a few cases (Myotragus balearicus, C. ropalophorus, and the smallest Hoplitomeryx) short and robust distal limb bones are already present at birth, but they become even more stout during postnatal ontogeny (Bover & Alcover, 1999b;Van der Geer, 2014a;Van der Geer et al., 2011). ...
... (size II), C. cretensis; Van der Geer, 2014aVan der Geer et al., 2011). In a few cases (Myotragus balearicus, C. ropalophorus, and the smallest Hoplitomeryx) short and robust distal limb bones are already present at birth, but they become even more stout during postnatal ontogeny (Bover & Alcover, 1999b;Van der Geer, 2014a;Van der Geer et al., 2011). ...
... However, they are rare in insular ruminants, except for the fusion of the metatarsal with the naviculo-cuboid and cuneiforms in Myotragus and Hoplitomeryx (see e.g. Bover & Fornós, 2005;Van der Geer, 2014a). Myotragus balearicus is also characterized by shortened phalanges, that is, shorter feet, rare fusion of the distal fibula (os malleolare) and tibia (observed also in Hoplitomeryx), and occasional carpal fusions (scapholunar and pisiform-cuneiform fusions), making this species the most extreme case of 'low gear' locomotion (see e.g. ...
Aim
Mammals on islands often undergo remarkable evolutionary changes. The acquisition of ‘low gear’ locomotion, namely short and robust limb elements, has been typically associated with the island syndrome in large mammals and, especially, ruminants. Here we provide an investigative framework to examine biotic and abiotic selective factors hypothesized to influence evolution of this peculiar type of gait.
Location
Islands worldwide.
Taxon
Bovidae.
Methods
We calculated response variables associated with ‘low gear’ locomotion in 21 extinct and extant insular bovids. We assembled data on the physiography of 11 islands and on life history and ecological traits of the focal taxa. We estimated 10 predictors (island area and four topographic indices, body mass, body size divergence, number of predators and competitors, large mammal richness) and used multiple regressions, regression trees, and random forests to assess their contextual importance.
Results
The acquisition of ‘low gear’ locomotion generally happens on islands with a small number of competitors. However, the roughness of the island terrain appears to be also important, without being a main driver. Finally, although the most extreme cases of ‘low gear’ locomotion occurred on islands with no mammalian predators, our models show a non‐significant relationship with this factor.
Main conclusions
The evolution of ‘low gear’ locomotion in insular ruminants does not simply result from phyletic dwarfing and predatory release. Variation in morphological responses within Bovidae to ecological and topographic traits suggests, instead, a complex interplay of biotic and abiotic factors. Current understanding on the main drivers of species evolutionary pathways and biogeographic patterns are disproportionally based on few taxa, mainly vertebrates, and in some extreme cases (like this one) even on few species. Here we show how adding more data, even within the same taxonomic group, can challenge historically accepted macroevolutionary and macroecological concepts.
... Some patterns have been claimed to be shared across space and time by a number of insular, not phylogenetically closely related mammals (e.g. Lomolino, 2005;Lomolino, Sax, Sondaar, 1977;Van der Geer, 2014;Van der Geer, Lyras, De Vos, & Dermitzakis, 2010;Van der Geer, Van den Bergh, et al., 2016), but a number of exceptions can be found when comparing different mammals on different islands (see Van der Geer, 2014 and references therein). Changes in bauplan and body size are the most spectacular of the peculiar changes undergone by island settlers ( Lomolino, 2016;Rozzi & Lomolino, 2017). ...
... Bovidae is a highly diverse clade of large mammals ( Bibi, 2013;Bibi et al., 2009;Hern andez Fern andez & Vrba, 2005) and encompasses several insular species that inhabited or are still living on islands located in different regions and characterized by different environmental features and palaeogeographic histories. The most intriguing and "ecologically na€ ıve" species (sensu Lomolino, 2016) include miniaturized buffaloes from Sulawesi and the Philippines ( Burton, Hedges, & Mustari, 2005;Croft, Heaney, Flynn, & Bautista, 2006;Custodio, Lepiten, & Heaney, 1996;Rozzi, 2017), the boselaphin Duboisia santeng from the Pleistocene of Java ( Rozzi, Winkler, De Vos, Schulz, & Palombo, 2013) and dwarfed extinct Caprini from the Mediterranean islands (K€ ohler & Moy a-Sol a, 2009; Palombo, Rozzi, & Bover, 2013;, 2014). Delving into space-time patterns of body size variation in insular mammals of intermediate ancestral size, such as insular bovids, may be crucial to confirm whether the island rule pattern is "graded" (sensu Lomolino et al., 2012 = "the degree of body size change decreases as we move from considering species of extreme, ancestral size, which change most dramatically, to those of intermediate ancestral size, which change more subtly or not at all") and to verify its overall stability. ...
Aim:
I provide the first comprehensive study on body size evolution of extinct and living insular bovids, exploring the causal biotic and abiotic selective factors for observed patterns.
Location:
Islands worldwide.
Methods:
I assembled data on the geographic characteristics of 13 focal islands (area, isolation, latitude, net primary productivity) and on the ecological and morphological characteristics of 32 insular bovid taxa (number of predators and competitors, richness of large mammals, body mass of mainland relatives). I used linear regressions and machine learning methods (regression trees and random forest analyses) to examine the hypothesized contextual importance of these factors in explaining variation in the body size of island bovids. I also calculated evolutionary rates of body size divergence of focal taxa in order to assess whether this phenomenon is influenced by time in isolation.
Results:
The results of regression, regression tree and random forest analyses were in agreement with predictions based on a hypothesis of ecological release (more pronounced body size divergence on islands with the fewest competitors and predators). Only limited support for a resource limitation hypothesis (more pronounced body size divergence for the larger taxa on smaller islands) was found.
Main conclusions:
The majority of insular bovids, as large mammals, do follow the main prediction of the island rule, exhibiting body size reduction, and predator diversity is the main factor influencing body size evolution of these taxa. Results obtained highlighted the crucial role of time in isolation, with body size reduction becoming more pronounced for bovids with longer residence times on the islands.
... Endemic elephants, variously reduced in size, have been reported from a number of Mediterranean islands. Most of the species originated from the mainland species Palaeoloxodon antiquus (e.g., dwarf straight-tusked elephants from Siculo-Maltese archipelago, Crete, Tilos, Rhodos, palaeo-Cyclades, Cyprus) (see, e.g., Ambrosetti, 1968;Athanassiou et al., 2015;Ferretti, 2008;Herridge, 2010;Herridge and Lister, 2012;Mangano and Bonfiglio, 2012;Masseti, 2006;Palombo, 2004Palombo, , 2010Poulakakis et al., 2002;Theodorou et al., 2007;Sen et al., 2014;Van der Geer et al., 2010, 2014. Conversely, in the Mediterranean islands, few dwarf mammoth remains have been reported, and those only in the oldest Pleistocene fauna of Crete (Mammuthus creticus), and in the youngest Pleistocene fauna of Sardinia (Mammuthus lamarmorai) (Herridge and Lister, 2012;Palombo et al., 2012). ...
... It is, however, worth noting that tibiae of Elephantidae, especially the distal part, show a high intra-and inter-species variation in morphology and sometimes proportions. The shapes of bones in insular large mammals, in particular that of joints, may, moreover, change considerably during the dwarfing process as size and body proportions change, as well as the appearance of apomorphic, ecomorphological features depending on landscape, environmental characteristics, and difference in gait based on speed, terrain, the need to manoeuvre, and energetic efficiency (see, e.g., Rozzi and Palombo, 2013;Scarborough et al., 2016;Van der Geer, 2014 and references in those papers). ...
Endemic elephants, variously reduced in size, have been reported from a number of Mediterranean islands. Most of these originated from the mainland species Palaeoloxodon antiquus. A few dwarf mammoth remains are recorded from Crete and Sardinia. In Sardinia, a largely incomplete skeleton and a few mammoth teeth have been reported from localities believed to range in age from the late middle to the late Pleistocene. The chronology of colonisation by the ancestral species, the actual persistence through time of Mammuthus lamarmorai on the island, and the morphological and dimensional range of the species are, however, poorly known. This research aims to describe a distal portion of a left tibia of a dwarf elephant found in the Alghero area (NW Sardinia), showing some morphological traits and dimensions consistent with those of the endemic Sardinian mammoth (Mammuthus lamarmorai). The main unanswered questions about chronology, colonisation and population dynamics of endemic Sardinian elephants are highlighted and briefly discussed.
... Isolated populations of terrestrial mammals have always raised a strong interest and received a great deal of attention in a broad range of scientific disciplines (Foster, 1964; van Valen, 1973; Sondaar, 1977; Heaney, 1978; Lomolino, 1985 Lomolino, , 2005 McNab, 2002; Meiri et al., 2006; Raia and Meiri, 2006; van der Geer, 2014a). So far, however, all the processes that lead to the origin, development and extinction of insular mammals are still poorly understood, as they follow a different evolutionary pathway than that of their mainland relatives (Sondaar, 1977). ...
... Restricted (both geographically and ecologically) environments are well-known to act as evolutionary laboratories, probably favoured by low interspecific competition and predation release (especially regarding large mammals) (Lomolino, 1985; Heaney, 1978; Millien, 2006; Meiri et al., 2011), but also induced by limited food resources, thereby causing rapid and extensive adaptive radiations (McNab, 2002). Even if body size changes are the best-known adaptation in insular environments , which can be easily observed in many (extant and extinct) insular taxa (van Valen, 1973; Heaney, 1978; Lomolino, 1985 Lomolino, , 2005 Raia et al., 2003; Lomolino et al., 2012; van der Geer, 2013 van der Geer, , 2014a), there are remarkable modifications in the craniodental and postcranial anatomy of the insular species if compared to their mainland counterparts (Sondaar, 1977 ). In some cases, the morphological changes are so extensive and peculiar that is not easy to trace back their closest mainland ancestor (e.g., Myotragus, Maremmia, Tyrrhenotragus, etc ). ...
Natural selection in isolated environments led to the positive selection of species bearing an extraordinary
array of morphological traits and a very high grade of endemism. The unbalanced
mammal assemblage found in the Upper Miocene karst infillings of the Gargano Peninsula (southern
Italy), and especially the intriguing ruminant Hoplitomeryx, is one of the best examples of fast,
isolated evolution. Hoplitomeryx exhibits a peculiar combination of craniodental and postcranial
characters, some of which are unique among the other ruminant families. For this reason, its phylogenetic
position is still puzzling and far from being clarified. Thus, every contribution to a more
comprehensive knowledge of the genus is crucial to better understand the evolutionary process
that led to such an advanced and peculiarly adapted ruminant. Here we report newly discovered
dentognathic remains from the Gargano Peninsula, which are attributed to six different species of
Hoplitomeryx on the basis of morphological and metrical evidence. Overall, our results show that
the different species of Hoplitomeryx are clearly distinguished from each other on the basis of the
dental morphology, which accounts for the high intraspecific and interspecific variability of the
genus. In addition, we describe for the first time a new type of “Muntiacus-like” upper canine, with
no-spiralization, more robust shaped and with more rounded anterior margin than the upper canines
previously reported for Hoplitomeryx.
... Toutefois, différents optima s'appliquent au clade considéré en fonction de divers facteurs évolutifs dès la phase d'immigration (sélection des immigrants) et post-colonisation (ressources disponibles, prédation, compétition, climat, etc.) (Lomolino et al., 2012). Nombre d'études validèrent cette nouvelle mouture de la loi insulaire (e.g., Lyras et al., 2006 ;van der Geer, 2014 ;Biddick & Burns, 2019 ;Athanassiou et al., 2019 ;Benítez-López et al., 2021), bien qu'une opposition substantielle (e.g., Meiri et al., 2004 ;Raia & Meiri, 2006 ;Meiri et al., 2008 ;Karagkouni et al., 2017 ;Itescu et al., 2018 ;Lokatis & Jeschke, 2018) ait scindé le débat en deux écoles majeures. Une grande part de cette opposition s'explique par l'altération des conditions insulaires liées à l'activité anthropique ainsi qu'à la sélection des taxons. ...
Islands have always fascinated scientists since their extensive exploration and documentation. They were even given the title of ‘natural laboratory’ in view of the replication of evolutionary experiments that they show both by their number and by their simplified condition compared to the mainland. Unfortunately, however idyllic they may appear, islands have suffered from major biodiversity losses due to human activity since the Holocene, disfiguring the evolutionary processes that used to take place locally. Consequently, the study of extinct island species known as ‘paleoinsular’ becomes essential to reconstruct the evolutionary framework characterising these isolated environments. To this end, bone palaeohistology is a tool of choice to access the palaeobiological archives preserved within bone tissue and to reveal the evolutionary trajectories that lead to the appearance of the biological curiosities populating islands. This article takes a particular look at island dwarfs and giants with a case study of dwarf sauropods from the Late Cretaceous European archipelago, in order to provide valuable scientific insights for tracing past worlds, increasing the fields of knowledge of the present, and adopting conservation strategies for the future.
... 2 For decades, issues related to the systematics, taxonomy, and evolutionary patterns of the Cretan deer have been attracting the attention of researches who extensively analyzed also their differences in size, feeding behavior, and locomotion. The Cretan deer phylogenetic relationships remain, however, a matter of major debate (Kotsakis et al. 1976;de Vos 1979de Vos , 1996de Vos , 2000de Vos , 2006Capasso Barbato & Petronio 1986;Capasso Barbato 1989, 1992Caloi & Palombo 1995Van der Geer et al. 2006, 2013Iliopoulos et al. 2010;Van der Geer 2014Altamura 2016). ...
The research describes for the first time a possible case of pituitary gigantism in fossil mammals, precisely in deer. The pathology was detected in two long bones (tibia and metatarsus) belonging to an individual of an unusual large size found at the Bate cave (Rethymnon, Northern Crete). It formed the basis of Candiacervus major Capasso Barbato & Petronio, 1986, the largest among the endemic deer species recorded in the Pleistocene‐Early Holocene of Crete. Radiological and histomorphological examinations highlighted a reduction in cortical bone thickness and the presence of wide lacunae inside of the bone tissue. The pathological conditions suggest a pituitary gigantism diagnosis also supported by some morphological evidence, such as the extremely elongated distal part of the metatarsal diaphysis, the proportionally small proximal epiphysis, and some bone gracility. The diagnosis of a case of pituitary gigantism as presumed responsible for the extraordinary elongation of the tibia and the metatarsal bone is intriguing as they are respectively the paratype and the holotype of the C. major. The species represents a case of a deviation from the “island rule” in Pleistocene large mammals. The new evidence recommends a taxonomic and nomenclatural revision of this species. The main outcomes of this research are as follows: i) a case of pituitary gigantism is described for the first time in an extinct mammal; ii) it is underlined that palaeohistology may provide interesting clues for disentangling taxonomic and nomenclatural issues; iii) one of the very few cases of gigantism in insular mammals is being questioned.
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... In this contribution, the taxonomy of De Vos (1996) is followed because 95.3% of the material from Liko cave belongs to size II. This size is commonly referred to as Candiacervus sp.II (De Vos, 1996; Van der Geer et al., 2006Van der Geer, 2014;Kolb et al., 2015). ...
Candiacervus sp.II is one of the deer species that inhabited the island of Crete during the Late Pleistocene. The species evolved on the island under a prolonged period of isolation and, as a consequence, developed a high degree of endemism. Fossils of this species have been discovered at many Cretan sites, including Liko cave (an attritional accumulation of several thousand fossils). In this paper, we present the results of a systematic analysis of the prevalence and anatomical distribution of bone lesions of Candiacervus sp.II, from that cave. We identified one metapodial with a healed fracture and nine (various) specimens with moderate to severe degenerative lesions of osteoarthritis. The lesions were evaluated macroscopically and radiographically, and they were classified as traumatic or degenerative. Degenerative lesions that affected adult individuals had prevalence rates below 5% and were attributed to environmental or nutritional causes. Representative bones were sampled for histological evaluation, to provide essential baseline data on possible underlying disorders. The aims of this study are to provide evidence for bone disease contributing to species morbidity, and to shed new light on causes and potential palaeoecological significance.
... It is not inferred from the browsing diet of C. astylodon that the hypsodont molars may be the adaptive response to wear-induced diets. Rather, the hypsodont molar may have evolved in combination with the elongated longevity of C. astylodon, similar to the case of M. balearicus (Jordana et al., 2012;van der Geer, 2014). For M. balearicus, not only the longevity but also other life history traits (time of weaning and sexual maturity) were modified to represent a slow life history or K-selection strategy (Marin-Moratalla et al., 2011;Jordana et al., 2013). ...
The Ryukyu Islands (Amami Islands, Okinawa Islands, and Sakishima Islands) form an island arch situated at the southern end of the Japanese archipelago. In this area, numerous fossiliferous localities have been estimated to date from the end of the Pleistocene, which have yielded abundant vertebrate fossil remains. Among the excavated fossils of terrestrial vertebrates, two extinct deer species, Cervus astylodon and Dicrocerus sp., are representative of the Late Pleistocene fauna of the Okinawa Islands. However, their ecological characteristics have been largely unknown to date. In the present study, we reconstructed the paleoecology of the deer species using mesowear and stable isotope analyses of tooth remains excavated from the Hananda-Gama Cave, Okinawa Island. Mesowear analysis estimates the properties of consumed food from the facet development of ungulate cheek teeth, with more abrasive diets (i.e., grass) resulting in more rounded cusps with a lower profile. Carbon isotopic composition (δ13C) reflects relative contribution of C3 (woody and most herbaceous plants) and C4 (grass growing in temperate to tropical regions) plants in diets, with the former showing lower δ13C values. Both extinct deer had sharp cusps with high profiles, which implied a significant amount of browse in diets. Our stable isotope analysis corroborated this: δ13C values were in the range of extant C3 feeders. Species ranges overlapped each other; however, C. astylodon had a wider range into the higher δ13C value range than Dicrocerus sp., which implied dietary niche differentiation between the two species. The dominance of C3 browse in their diet supports a hypothesis that hypsodont molar of C. astylodon was not an adaptive response to abrasive and wear-induced diet but correlated evolution with its elongated longevity, which was considered to be up to 26 years of age.
... In a recent paper published in a special issue of Integrative Zoology on 'Paleontology and evolution-part I.' (Palombo 2014), the author (van der Geer 2014) takes a review of the derived traits observed in endemic fossil insular mammals, including body size variation, cranial and postcranial changes, and modifications in dentition. At one point in the discussion, the author misinterprets and seriously distorts statements by Jordana et al. (2012) on the relationship between hypsodonty and longevity in the fossil insular bovid Myotragus balearicus Bate, 1909. ...
In a recent paper published in a special issue on ‘Paleontology and Evolution’ of Integrative Zoology (Palombo 2014), the author (Van der Geer 2014) takes a review of the derived traits observed in endemic fossil insular mammals, including body size variation, cranial and postcranial changes, and modifications in dentition.This article is protected by copyright. All rights reserved
... But since they occur in other insular ruminants, such as Myotragus balearicus, these features may be plausibly interpreted as adaptations to insular environments. These features include: (1) greatly increased robusticity of the limb bones (de Vos, 1979de Vos, , 1984), (2) slightly increased incidence of partial fusion of the tarsometatarsal joint (~10% of adult individuals; de Vos, 1979) relative to average frequencies in mainland populations (van der Geer, 2014); (3) lacrimal fossa weak or even absent; (4) relatively short lower limbs in relation to thoracolumbar length (van der Geer et al., 2006b), likely related to topography (see Terada et al., 2012); and (5) a slight increase in molar hypsodonty (de Vos, 1979). The trend in body proportions (4) is already in evidence at birth and becomes more apparent during ontogeny (van der Geer et al., 2006a). ...
Age-graded fossils of Pleistocene endemic Cretan deer (Candiacervus spp.) reveal unexpectedly high juvenile mortality similar to that reported for extant mainland ruminants, despite the fact that these deer lived in a predator-free environment and became extinct before any plausible date for human arrival. Age profiles show that deer surviving past the fawn stage were relatively long-lived for ruminants, indicating that high juvenile mortality was not an expression of their living a “fast” life. Although the effects on survivorship of such variables as fatal accidents, starvation, and disease are difficult to gauge in extinct taxa, the presence of extreme morphological variability within nominal species/ecomorphs of Candiacervus is consistent with
the view that high juvenile mortality can function as a key innovation permitting rapid adaptation in insular contexts.
... In this contribution, Inuzuka and Takahashi (2004) and Shoshani and Tassy (2005) Herridge and Lister, 2012). This new analysis should take secondarily derived characters and changes due to allometry into consideration (see for a discussion on convergent morphologies in unrelated insular taxa Van der Geer, 2014); in fact, this applies to the type species P. naumanni as well, which is an insular species of Japan. ...
During the Late Pleistocene, Naxos and adjacent areas, including Delos and Paros, constituted a mega-island, here referred to as palaeo-Cyclades. The extensive low-lying plains with lakes and rivers provided a suitable habitat for elephants. Due to long-term isolation from the mainland and mainland populations, these elephants evolved miniature size. The species found on Naxos had a body size of about ten percent of that of the mainland ancestor, Palaeoloxodon antiquus. During the glacial periods of the Late Pleistocene, P. antiquus may have migrated eastwards and southwards in search of better conditions and reached the islands. The dwarf species of the various Southern Aegean islands (e.g. Crete, Tilos, Rhodos, palaeo-Cyclades) are each the result of independent colonisation events. The very small size of the Naxos species respective to the dwarf elephants from Crete is explained as due to the lack of competitors. The only other elements of the contemporaneous fauna were a rock mouse (Apodemus cf. mystacinus) and a shrew (Crocidura sp.). Submergence of the area, climate change, volcanism, hunting by humans or a combination of these factors during the terminal Pleistocene may have caused the extinction of this endemic fauna.
... van Valen 1973;Heaney 1978;Lomolino 1985;Lomolino et al. 2006Lomolino et al. , 2012Lomolino et al. , 2013Köhler et al. 2008;Meiri et al. 2008;Palombo 2009a;Benton et al. 2010). Furthermore, several authors described the peculiar morphological traits acquired by insular mammalian species, in a few cases highlighting pervasive patterns that affected most of the representatives of particular lineages, such as proboscideans and ruminants (see e.g. de Vos 2000;van der Geer 2005van der Geer , 2014de Vos et al. 2007;Palombo 2007;Palombo et al. 2013). A comprehensive overview of the changes in body size and evolutionary patterns exhibited by both extant and fossil insular bovids is still lacking. ...
Endemic bovids are intriguing elements of insular faunas. The living species include the Japanese serow (Capricornis crispus) and the Formosan serow (C. swinhoei), the tamaraw from Mindoro, Philippines, (Bubalus mindorensis) and the anoas (B. depressicornis and B. quarlesi), 2 species of dwarf buffalos endemic to Sulawesi, Indonesia. Fossil endemic bovids are only recorded in some Asian, North American and Western Mediterranean islands. Here we present a comprehensive overview of the changes in body size and evolutionary patterns exhibited by both extant and extinct insular bovids. Our appraisal indicates that each insular representative of Bovidae shows its own peculiar evolutionary model, albeit some parallel trends exist (e.g. reduction in body size, allometric changes in limb bones, alteration of the life history traits). Some changes in morphology (e.g. the simplification of horn cores, the increase in hypsodonty, the acquisition of a 'low-gear' locomotion), for instance, appear as common, albeit not general, patterns triggered by a combination of selective forces. Body size patterns support the 'generality of the island rule' and suggest that biotic interaction had/have a major role in influencing body size evolution in these species, although in different ways on different islands. All things considered, available evidence suggest that a major role in the evolution of insular bovids is played by the structure of the insular community, the nature of available niches and by the dynamics of ecological interactions.
We studied the functional morphology of the postcranial skeleton of the endemic hippopotamus Phanourios minor, derived from the Upper Pleistocene site of Ayia Napa. The deposit, which consists of a hard limestone substrate on which the species moved, has yielded a great abundance of hippopotamus material, making the Ayia Napa locality one of the most important paleontological sites in Cyprus. The immigration of the large-sized mainland Hippopotamus to Cyprus led to the emergence of a new insular species with its main characteristic being the extremely reduced body size. In this study, all the hindlimb elements of the Cypriot hippo are described in detail and compared with those of the modern species, with the extant Hippopotamus amphibius being considered similar to the possible ancestor of P. minor. In some cases, the morphological comparison is reinforced using bones of other extinct insular and mainland hippos. Additionally, we provided a functional analysis of the hindlimb joints, suggesting specific locomotor habits for the species. The anatomical examination reveals that the elements in P. minor are robust with marked muscular insertion areas resembling those found in Hippopotamus. However, there are also similarities with Choeropsis liberiensis in certain morphofunctional traits. P. minor adapted to slow but powerful locomotion with remarkable stabilization, particularly in the zeugopodium and the autopodium. The knee was less mobile in the craniocaudal direction compared with that in recent hippos, while the abduction-adduction movements of the thigh were advanced. The pes presented good mobility in the sagittal plane and limitation in transversal movements. Thus, P. minor displayed modifications to its limbs, influenced by the mountainous island environment and the body size reduction, resulting in specialized locomotion, which was different from that of extant hippopotamuses.
We describe the first endemic large mammal from the Neogene of the Island Eivissa (Balearic Islands, Spain), a new genus and species of an endemic insular bovid, Ebusia n. gen. moralesi n. sp. (Artiodactyla, Caprini). This new taxon is the smallest caprine currently described and shows primitive, continental-like complete dentition. It has a long and complex lower p2 and upper P2 and P3, long premolar series, non-hypsodont incisors and a moderate degree of hypsodonty of the check teeth. The long bones (in particular the tibia) are rather slender, similar to those of continental bovids. However, the metapodials show an intermediate degree of shortening between continental bovids and Myotragus species and other insular ruminants. The few derived insular adaptations of Ebusia n. gen. suggest that this taxon probably represents the first phase of isolation. The morphology of the dentition and postcranial is characteristic of Caprini and similar to that of the Myotragus/Nesogoral group. This suggests that E. moralesi would be close to the ancestral continental pattern of the endemic Neogene-Quaternary caprine lineage that colonised the western Mediterranean Islands during the Messinian salinity crisis.
The species Homo luzonensis has recently been described based on a set of dental and postcranial elements found at Callao Cave (Northern Luzon, Philippines) and dated to at least 50–67 ka. Seven postcanine maxillary teeth are attributed to this taxon, five of them belonging to the same individual (CCH6) and representing the holotype of H. luzonensis, whereas the isolated upper premolar CCH8 and the upper third molar CCH9 are paratypes of the species. The teeth are characterized by their small dimensions associated with primitive features, as also found in Homo floresiensis, another hominin having evolved in an insular environment of Southeast Asia. Postcranial bones of the hands and feet of H. luzonensis and H. floresiensis show Homo habilis–like or australopith-like features, whereas cranial and dental morphology are more consistent with the Asian Homo erectus morphology. Due to this mosaic morphology, the origin and phylogenetic relationships of both H. luzonensis and H. floresiensis are still debated. To test the hypotheses that H. luzonensis derives from H. erectus or from an earlier small-brained hominin, we analyzed the µCT scans of the teeth. We investigated both external and internal tooth structure using morphometric methods including: crown outline shape, tooth crown tissue proportions, enamel-dentine junction shape, and pulp morphology. Homo luzonensis external crown morphology aligns more with H. erectus than with H. habilis/H. rudolfensis. The internal structural organization of H. luzonensis teeth exhibits more affinities with that of H. erectus and H. floresiensis than with Neanderthals and modern humans. Our results suggest that both H. floresiensis and H. luzonensis likely evolved from some H. erectus groups that dispersed in the various islands of this region and became isolated until endemic speciation events occurred at least twice during the Pleistocene in insular environments.
Body size is a useful character to unravel the biology of fossil taxa and, indirectly, the palaeoenvironment in which they lived. However, the reliability of size proxies is debated, particularly among insular endemics in which large teeth relative to body size have been observed. To shed light on this issue, here we compute statistical models to assess: (i) teeth and long bone scaling and (ii) dentition size evolutionary dynamics in the anagenetic lineage Prolagus figaro-P. sardus from the late Early Pleistocene-Holocene of Sardinia, Italy. Postcranial bones, particularly tibial epiphyses, are shown to be the most suitable parameters for prediction of body mass in Prolagus and other lagomorph taxa. By contrast, p3 should not be used for size reconstructions, whereas m1 width provided the highest correlation with long bones. On the other hand, the postcanine occlusal surface of Sardinian Prolagus (m1 and toothrow area) appeared significantly larger than those of extant lagomorphs, pointing to a higher resistance to tooth wear and a more durable permanent dentition. It seems likely that megalodontia might have evolved in Sardinian Prolagus to cope with the abrasive diet found on islands (food habit hypothesis). Nonetheless, we cannot exclude that other biological features, such as long longevity, could be co-driving forces in this fossil lineage (life history hypothesis). The results achieved throw light on size and scale evolution in lagomorphs, as well as refine the eco-evolutionary responses of small mammals to insular regimes.
This study provides a complete morphological description and functional analysis of the carpal bones of the endemic pygmy hippopotamus Phanourios minor, derived from the Upper Pleistocene site of Ayia Napa. From this deposit, numerous skeletal remains of this fossil hippo have been collected, making the locality one of the richest in Cyprus. The carpal bones were compared with those of extant hippopotamuses, to determine the changes that occurred in the fossil hippo. Examination of the elements showed that Phanourios presented some important features that were common among the endemic fossil ungulates of the Mediterranean islands. The carpal bones display a proximal–distal compression due to shortening of the distal part of the leg, due to the new ecological island conditions. However, they are robust with rough areas for strong muscular and ligament insertions, providing stability to the carpal joints, and low speed movement to the animal. The great flexor capabilities, and the limitation in ulnar deviation of the carpus, indicate that P. minor had increased agility in the sagittal plane and restricted transverse movements, while the suggestion of a more unguligrade stance for the species is ambiguous. Thus, the endemic Cypriot hippos developed specialized locomotion, suitable for walking on the rugged terrain of Cyprus, which seems to be different from that of its extant counterparts.
Changes in body proportions and functional structures in island endemics tend to evolve in parallel ways. These parallel evolutionary changes are not restricted to certain genera but occur in a wide taxonomic range. The parallel patterns and trends are functionally best explained by shared adaptational needs, such as those to cope with rugose or mountainous terrain, abrasive or nutrient‐low diets, and increased intraspecific competition. part from the extremely hypsodont molars, the latter lineage also evolved ever‐growing incisors to cope with a higher degree of wear of the front teeth, in parallel with the unrelated antelope Maremmia of the Late Miocene of Tuscany. Christian Kolb and colleagues found that the Late Pleistocene dwarf deer of Crete was characterised by low growth rates and late attainment of skeletal maturity.
This chapter gives a concise overview of the faunas of Gargano. Then, a comprehensive treatment is provided of the history of discoveries, biozones, or faunal units and the peculiarities and evolutionary aspects of individual endemic species or lineages. The palaeo‐island Gargano is now part of mainland Italy. During the Late Miocene and Early Pliocene, it was an island, harbouring a highly endemic fauna, including five‐horned deer, giant gymnures, giant pikas, and several rodent lineages. The mid‐Pliocene flooding of the area led to the extinction of this peculiar fauna. After the area emerged again and became connected to Italy in the Early Pleistocene, it was colonised by a balanced mainland fauna. From the Early Pleistocene on, the region was interested by a general uplifting, resulting in the regression and continentalisation of the area.
Museums hold millions of objects from all over the globe, offering a unique, unparalleled resource for researchers. They provide historical snapshots of data both geographically and through time, giving researchers rare access to huge amounts of information. Recent advances in analytical techniques have allowed for even more information to be obtained from collections, from radiocarbon dating to genetic sequencing. This entry provides some background on museums and their collections, along with key examples of research that has been undertaken using both nondestructive and destructive sampling methods. It also outlines details on how collections can be used, limitations in sampling, and how to search for objects in museums across Britain. The potential for collections to assist with research is enormous, and this applies not only to national museums but also to smaller regional museums.
Climate change strongly affects the range of ochotonids (Order Lagomorpha), fragmenting their habitats and restricting them to ecological islands. The present paper discusses the adaptations of extinct ochotonids to insular stressors, providing baseline data for the management and conservation of extant species. For this purpose, the body mass (BM) and locomotion of the endemic Prolagus apricenicus and Prolagus imperialis from the Gargano palaeo archipelago (Late Miocene) were assessed. P. apricenicus was a small-sized ochotonid (BM 150–250 g) and P. imperialis was probably the largest Prolagus that ever lived (BM 500–750 g). The eco-evolutionary BM dynamics suggest a targeted ecological niche for P. apricenicus, whereas the BM of P. imperialis rose abruptly as a result of growth-rate increase. In both species, the locomotion was stable and less cursorial, with leaping skills, resembling extant rocky ochotonids. Convergent eco-evolutionary patterns are observed in extinct insular ochotonids, concerning an increase of BM (giants), more efficient chewing, less cursorial and more stable locomotion, leaping skills, as well as a slower life history (longer lifespan). Such adaptations are triggered by the specific selective pressures of insular regimes. The present results point to the long-lasting insular Prolagus species as reference taxa for addressing the management of extant rocky ochotonids.
Island dwarfing is a paraphyletic adaptation across numerous mammalian genera. From mammoths to foxes, extreme body size reduction is shared by diverse organisms that migrate to an island environment. Because it largely occurs owing to ecological variables, not phylogenetic ones, skeletal characters in a dwarfed taxon compared with its ancestor may appear abnormal. As a result, allometric patterns between body size and morphological traits may differ for an island dwarf compared with its ancestor. The diminutive Late Pleistocene hominin, Homo floresiensis, displays a unique character suite that is outside of the normal range of variation for any extinct or extant hominin species. To better explain these as ecological traits due to island dwarfing, this research looks at how dwarfing on islands influences limb scaling and proportions in an organism in a similar ecological niche as H. floresiensis. Here, I analyze absolute limb lengths and static allometry of limb lengths regressed on predicted body mass of dwarfed island foxes and their nondwarfed relatives. Dwarfed island foxes have significantly smaller intercepts but steeper slopes of all limb elements regressed on predicted body mass than the mainland gray fox. These allometric alterations produce limbs in the island fox that are significantly shorter than predicted for a nondwarfed gray fox of similar body mass. In addition, the humerofemoral, intermembral, and brachial indices are significantly different. These results provide a novel model for understanding skeletal variation of island endemic forms. Unique body size and proportions of H. floresiensis are plausible as ecological adaptations and likely not examples of symplesiomorphies with Australopithecus sp. Caution should be exerted when comparing an island dwarf with a closely related species as deviations from allometric expectations may be common.
Insular gigantism-evolutionary increases in body size from small-bodied mainland ancestors-is a conceptually significant, but poorly studied, evolutionary phenomenon. Gigantism is widespread on Mediterranean islands, particularly among fossil and extant dormice. These include an extant giant population of Eliomys quercinus on Formentera, the giant Balearic genus †Hypnomys and the exceptionally large †Leithia melitensis of Pleistocene Sicily. We quantified patterns of cranial and mandibular shape and their relationships to head size (allometry) among mainland and insular dormouse populations, asking to what extent the morphology of island giants is explained by allometry. We find that gigantism in dormice is not simply an extrapolation of the allometric trajectory of their mainland relatives. Instead, a large portion of their distinctive cranial and mandibular morphology resulted from the population- or species-specific evolutionary shape changes. Our findings suggest that body size increases in insular giant dormice were accompanied by the evolutionary divergence of feeding adaptations. This complements other evidence of ecological divergence in these taxa, which span predominantly faunivorous to herbivorous diets. Our findings suggest that insular gigantism involves context-dependent phenotypic modifications, underscoring the highly distinctive nature of island faunas.
The Eastern Mediterranean islands, most of which belong to the Aegean archipelago, have a complex biogeographic history, which puts its stamp on their fauna and flora. A now extinct but most important faunal component, in terms of geographic spread and taxonomic diversity, are the elephants. The Eastern Mediterranean islands are particularly rich in Pleistocene endemic elephant localities, which preserve samples of extinct endemic populations. These were either descendants of the European straight-tusked elephant Palaeoloxodon antiquus or the Southern mammoth, Mammuthus meridionalis. Their presence, history and palaeobiogeography has been documented only for Cyprus, Crete, Kasos, Rhodes, Tilos, Kýthera, Naxos, and Delos. For six other islands only anecdotal references exist in the literature: K alymnos, Astyp alaia, Milos, S eriphos, Kýthnos and Paros. Here, we provide an update on previously published specimens and taxa, describe previously undescribed specimens that were relocated in museum collections, as well as recently excavated specimens, and put these in the context of island palaeobiogeography. We conclude that dwarf elephants, endemic to their palaeo-island, lived on the islands of palaeo-Cyclades, Astyp alaia, Crete, KasoseK arpathoseSaría, Tilos, Rhodes and Cyprus, whereas the elephants from Kephallenía, K alymnos and Kýthera are indistinguishable on the species level from mainland Palaeoloxodon antiquus. Elephant fossils of unresolved taxonomic status are reported from five present-day islands. The Eastern Mediterranean endemic elephants likely derived from separate and independent colonisation events from the mainland. No island supported more than one proboscidean species at any time. We found that isolation had no effect on the degree of dwarfism, but that there exists a threshold of about 6e10 km distance between the island and the mainland, below which no dwarfism evolved, likely as a result of genetic contact with the mainland population. We also found that although island area is correlated with the degree of dwarfism in elephants, other factors, such as the level of interspecific competition, may limit this degree.
Populations of vertebrate species introduced onto islands regularly develop similar phenotypic changes, e.g., larger or smaller body size, shortened limbs, duller coats, as well as behavioural changes such as increased tameness and reduced flight-initiation distance. These changes overlap in part with those associated with the 'domestication syndrome', especially tameness and changes in coat patterns, and might indicate a similar neural crest involvement in the concurrent development of multiple phenotypic traits. Here I examine long-term data on free-living populations of wild Polynesian rats from seven mainland countries and 117 islands (n = 3,034), covering the species' native and introduced range. Mainland populations showed no aberrant coat patterns, with the exception of one albino, whereas aberrant coat patterns were found in 12 island populations. Observed coat colour polymorphisms consisted of leucistic (including singular white patches), melanistic (darkly pigmented) and piebald (mixed) coat patterns. After isolation for at least seven centuries, wild Polynesian rat populations on islands seem to exhibit a trend towards a higher incidence of aberrant coat patterns. These phenotypic changes are here explained as a neutral, non-adaptive process, likely part of the 'domestication syndrome' (via the commensal pathway of domestication), in combination with genetic drift, little or no gene flow between the islands and/or the mainland and a relaxed selection (as a result of the weakening or removal of competitor/predator pressure) under commensality.
Terre Rosse deposits (upper Miocene; Gargano, Italy) have provided fossil remains of an insular fauna among which the genus Mikrotia (Rodentia) stands out. Several paleobiological studies have already been conducted on this genus, but its body mass has not yet been calculated accurately. The aim of the present work is to reconstruct Mikrotia magna's weight, a paramount aspect of organismal biology, especially on islands where mammals modify their size, becoming giants or dwarfs ('island rule'). Our analysis using postcranial elements (femora and humeri) predicts weights ranging from 1300 g to 1900 g (old and young populations, respectively). The presence of a large number of micromammals on the Gargano paleo-island suggests a high interspecific competition for species of the same ecological guild (Prolagus or cricetids were direct competitors of Mikrotia), which may lead to only moderate gigantism, or even body mass reductions in small mammals, following Palkovacs's model. This contrasts with the huge weight of M. magna inferred in this study. In this regard, stratigraphic and taxonomic studies suggest that M. magna was an immigrant from a neighboring island, indicating that this species originated and achieved its enormous size under other selective pressures. A native island with a lower number of competitors, and therefore with less resource limitation than Terre Rosse, might be the principal explanation for such a degree of gigantism.
Llistat de la Bibliografia Naturalística de les Balears, S-Z
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Members of the mammalian families Elephantidae and Hippopotamidae (extant and extinct elephants and hippos) include extinct dwarf species that display up to 98% decrease in body size compared to probable ancestral sources. In addition to differences in body mass, skulls of these species consistently display distinctive morphological changes, including major reduction of pneumatised areas in dwarf elephants and shortened muzzles in dwarf hippos. Here we build on previous studies of island dwarf species by conducting a geometric morphometric analysis of skull morphology and allometry in target taxa, living and extinct, and elaborate on the relation between skull size and body size. Our analysis indicates that skull size and body size within terrestrial placental mammals scale almost isometrically (PGLS major axis slope 0.906). Furthermore, skull shape in dwarf species differed from both their ancestors and the juveniles of extant species. In insular dwarf hippos, the skull was subject to considerable anatomical reorganisation in response to distinct selection pressures affecting early ontogeny (the “island syndrome”). By contrast, skull shape in adult insular dwarf elephants can be explained well by allometric effects; selection on size may thus have been the main driver of skull shape in dwarf elephants. We suggest that a tightly constrained growth trajectory, without major anatomical reorganization of the skull, allowed for flexible adaptations to changing environments and was one of the factors underlying the evolutionary success of insular dwarf elephants.
The extreme rareness of Sardinian fossil sites older than Middle and Late Pleistocene makes the Monte Tuttavista karst complex (E Sardinia, Italy) very important. Remarkable lagomorph material, recovered from several fissure infillings of Monte Tuttavista referable to the Capo Figari/Orosei 1 and Orosei 2 faunal sub-complexes (early Pleistocene, ~2.1/1.9–1.1 Ma), allowed us to describe a new endemic insular leporid, Sardolagus obscurus n. gen. n. sp. The new taxon is characterized by a peculiar combination of an advanced p3 ( Lepus -type) and a primitive P2 lacking deep flexa. The origin of such discrepancy, unprecedented among continental and insular endemic European leporids, is unclear. It could be the result of: (1) an independent evolution of p3 from an ancestor bearing the primitive P2/p3 (e.g., Alilepus , Hypolagus ), or (2) a selective reversal morphocline from an Oryctolagus / Lepus -like leporine. The lack of data about the phylogenetic origin of the new taxon makes any inference about its possible arrival to Sardinia problematic. Crossing the European leporid records and evidence of migrations to Sardinia, we hypothesize three possible ages in which the ancestor of Sardolagus obscurus could have arrived in Sardinia, restricted to the late Miocene–early/late Pliocene (~8–3.6 Ma). The phylogenetic relationship between Sardolagus obscurus n. gen. n. sp. and the oldest Sardinian leporid, recorded from Capo Mannu D1 and dated at the early/late Pliocene boundary (~3.6 Ma), is unclear at present, however it is quite likely that they pertain to the same lineage.
UUID: http://zoobank.org/ca8e0023-7c9d-4b00-a294-d166c37c5c71
Lower and Middle Palaeolithic artifacts on Greek islands separated from the mainland in the Middle and Upper Pleistocene may be proxy evidence for maritime activity in the eastern Mediterranean. Four hypotheses are connected with this topic. The first is the presence of archaic hominins on the islands in the Palaeolithic, and the second is that some of the islands were separated from the mainland when hominins reached them. A third hypothesis is that archaic hominin technological and cognitive capabilities were sufficient for the fabrication of watercraft. Finally, the required wayfinding skills for open sea-crossings were within the purview of early humans. Our review of the archaeological, experimental, ethno-historical, and theoretical evidence leads us to conclude that there is no a priori reason to reject the first two hypotheses in the absence of more targeted archaeological surveys on the islands, and thus the latter two hypotheses should be tested by future research.
Six species of the cervoid genus Hoplitomeryx are currently recognized from the Late Miocene sites of Gargano and Scontrone, in Italy: H. matthei Leinders, 1984, H. apruthiensis Mazza & Rustioni, 2011, H. apulicus Mazza & Rustioni, 2011, H. falcidens Mazza & Rustioni, 2011, H. magnus Mazza & Rustioni, 2011, and H. minutus Mazza & Rustioni, 2011. These species are interpreted as members of an anagenetic series in these two localities, which are considered as part of the same bioprovince but with different geological ages. Comparative analysis of postcranial, dental, and cranial material from Hoplitomerycidae resulted in the reinterpretation of this current taxonomic arrangement. Two distinct genera can be distinguished. The new genus Scontromeryx is restricted to Scontrone (Early Tortonian) and is characterised by the presence of second upper and lower premolars and the absence of a nasal (median) horn. Hoplitomeryx is restricted to Gargano (Middle and/or Late Tortonian), and is characterized by the loss of the second premolar and presence of a nasal horn. Both genera are characterized by orbital appendages in some species, but the morphology of these appendages differs between the genera. Six species can be recognized for Scontromeryx gen. n.: S. minutus (type species), S. falcidens, S. apulicus, S.apruthiensis, S. magnus (new combinations) and the newly described S. mazzai sp. n.. Hoplitomeryx is represented by the H. matthei (type species) and 3 newly described species H. devosi sp. n., H. macpheei sp. n. and H. kriegsmani sp. n. These two multispecies assemblages are best explained as independent adaptive radiations with the two genera as sister taxa. There is no evidence that the two localities were connected during the Late Miocene.
Evolution is one of the central unifying concepts of natural history and modern science. Although it is well documented by many lines of evidence from a number of scientific disciplines (e.g. genetics, molecular biology, comparative anatomy, biogeography), its major support indeed comes from the fossil record, where the history of life can be seen unravelling through geological deep time. Organisms have modified their characteristics over time, and new taxa have incessantly appeared. This article is protected by copyright. All rights reserved.
During the Pleistocene, the Sunda Islands to which Java belongs were frequently connected with the East Asian mainland, permitting faunal elements of Indo-Chinese origin entering Java. Therefore, most Javanese mammalian taxa are close if not identical to their mainland relatives. In particular, three fossil bovids, commonly found in the Early–Middle Pleistocene “Stegodon-Homo erectus fauna” (Bubalus palaeokerabau, Bibos palaesondaicus, and Epileptobos groeneveldtii), do not show any feature consistent with the evolutionary pattern of typical insular mammals. However, a fourth Javanese bovid, Duboisia santeng has been regarded as a typical insular endemic species due to its small size. However, since Duboisia has been claimed to be present in the late Middle Pleistocene of what is now peninsular Malaysia, the actual endemic insular status of this taxon needs further confirmation.In this study we aim to contribute to the debate by analyzing the autecology of Javanese Duboisia santeng, delving into its paleobiogeographic history and evolution. The multiproxy approach adopted here (body mass estimate, paleohabitat predictions, morphological comparison, mesowear analysis and Dental Areal Surface Texture Analysis DASTA) gave mutually consistent results and proved to be useful in supporting hypothesis regarding the complex evolution of insular faunas.
The endemic insular canid Cynotherium sardous has been known for 1 ½ centuries, yet its phylogenetic position remained unsolved. This was because inherited ancestral characters and acquired adaptations to different ecological pressures could not be separated. In this study the problem is approached again, with the use of morphological features that were either overlooked or could not be explained properly, combined with results from recent major revisions of canid phylogeny. It appears that Xenocyon is the ancestor of Cynotherium, and that this large hypercarnivorous canid, once on the island, faced a rather different menu consisting of small prey only. The subsequent necessary adaptation resulted in a small-sized dog whose dentition remained much the same, whereas its skull lost the typical fortifications seen in the other hypercarnivorous canids; these are considered superfluous for Cynotherium, which had to exchange big and strong prey for small and fast prey.
This paper describes a new species of shrew from a fossiliferous bone breccia near to Caló den Rafelino (Mallorca, Spain). The site is stratigraphically and palaeontologically dated to the earliest Early Pliocene (MN13-14). Nesiotites rafelinensis sp. nov. (Mammalia, Soricidae) is arguably the earliest representative of the Nesiotites known to date, a clade restricted to the Balearic Islands. The new species combines primitive dental traits with a relatively large size. The primitive features relate N. rafelinensis more with Asoriculus gibberodon, the possible ancestor of Nesiotites, than any other representative of the genus. The large size interrupts a, otherwise, regular trend of increase of size from the comparatively small A. gibberodon to the recent very large N. hidalgo. The faunal assemblage of Caló den Rafelino represents the earliest evidence of the fauna that arrived to the Mallorca Island during the Messinian Salinity Crisis.
Contains a detailed account and a discussion of possible origins of the fossil goat from Capo Figari. -from Authors
The endemic bovid Myotragus, from the Plio-Pleistocene deposits of Majorca, underwent a significant reduction in relative brain size, especially affecting the vision and locomotor centres. These important modifications allow the hypothesis that, under altered conditions in predator free insular environments, functional demands on neural performance are reduced, allowing a reduction in brain structures and associated sense organs. This is suggested, for example, by the small orbits and reduced visual brain structures of Myotragus balearicus Bate, 1909. These changes, which parallel those shown by domesticated animals, have been interpreted as an adaptive response to insular environmental conditions, in particular to a lack of interspecific competitors and predators. Results obtained from analysis of the smallest Cretan deer (Candiacervus ropalophorus de Vos, 1984, and Candiacervus spp. II) are not as outstanding as it is in Myotragus, and apparently run counter to the fact that dwarfed insular artiodactyls living in environments without any predation pressure would be characterised by a proportional decrease in brain volume as a rule. Brain/body mass proportion of the smallest Candiacervus species provides evidence that this endemic deer underwent only minor changes in the relative size of brain after its geographic isolation. On the other hand, orbit and foramen magnum size are proportionally reduced. Accordingly, different evolutionary process likely affected brain and sense organs changes of these endemic artiodactyls. Other factors, nature of available niches, inter-specific competition, maybe island size and time from isolation, would have played a role in the possible differential evolution of insular ruminants in addition to the change in adaptive strategy for a more efficient energy use under the free-predators environmental conditions of the insular ecosystem.
The tick fauna of the West Indies (divided into Cuba, the Greater Antilles, and the Lesser Antilles) is compared with some continental areas (Venezuela, Panama, Peru, and Madagascar). Taxonomic inventories and host and structural niche preferences are used as zoogeographical characters. On the islands the dominants are Argasid ticks, parasites of birds, bats, and reptiles, cavernicolous and lapidicolous. In the continental conditions the dominants are Ixodid ticks, macromastophiles of open fields. The colonization of the West Indies follows three main patterns: (1) a Central America-West Indies-South America route; (2) a North America-West Indies route; and (3) an anthropogenic introduction. A fourth group with cosmopolitan distribution is not included in any of the three patterns because of lack of information.
The Late Miocene-Early Pliocene "Terre Rosse" vertebrate assemblages, found in the palaeokarst fissure fillings of the Apricena-Poggio Imperiale limestone quarries (North-Western side of the Gargano promontory, southern Italy), document a very long and complex history of endemic populations of a palaeoarchipelago. That history developed in at least four populating phases, which are characterised by changes infaunal diversity and include taxa with different degree of endemism. They have been subject of several studies since the beginning of the 1970s and deserve a particular attention for their evolutionary and palaeogeographical implications. The sampling of the "Terre Rosse" fissure fillings was carried on during successive field surveys from the Leiden Museum (1969-74) and from the Florence University (1980s). Until now, however, the two resulting collections have always been studied separately by different authors: this work is the first partial attempt to integrate the information derived from the two collections. A biochronological framework is proposed integrating the chronological succession of samples by Freudenthal in the scheme elaborated by De Giuli et al. However, some uncertainty remains in the details of the position of some fissure, in particular Rinascita 1. After the pioneering description of the gigantic dormouse Stertomys laticrestatus Daams & Freudenthal 1985, the interest in the systematic of the Neogene Gargano glirids renewed just in the very last years. Four species have been recently described: Stertomys daunius Freudenthal & Martín-Suárez 2006, Stertomys daamsi Freudenthal & Martín-Suárez 2006, Stertomys lyrifer Martín-Suárez & Freudenthal 2007, and Stertomys simplex Martín-Suárez & Freudenthal 2007. In the present work the description of Stertomys from eleven further fissure fillings, documenting most of the whole succession of endemic population phases, is presented and discussed. The samples, for a total amount of 1696 dental elements, have been described by basic statistical parameter of measurements and frequency distribution of Daams' and Rinaldi's morphotypes. Where necessary, the differences among samples have been statistically tested (t-test and chi-square test). Seven taxa have been identified: S. daunius, S. laticrestatus, S. off. laticrestatus, S. ex gr. daamsi, Stertomys degiulii nov. sp., S. cf. degiulii and S. off. degiulii. In the fissure F15 S.ex gr. daamsi has the same size as S. daamsi from its type-locality Biancone 1, but a slightly more complex morphology in the upper molars. In Trefossi 1, F21b, Cantatore 3A and Fina D, S. ex gr. daamsi shows a rather similar morphology as in F15, but it is clearly smaller in size. S. degiulii, from F1, F9 (type-locality) and San Giovannino is distinctly smaller than S. gr. daamsi and presents a higher frequency of the connection of the trigon crests with the metaloph in the upper molars. S. off. degiulii from F32 is slightly larger in size and shows a higher frequency of connection of the anterolophid with the protoconid in the lower molars. S. cf. degiulii from Pirro UA is intermediate in morphology between S. degiulii and S. off. degiulii. The results of the analysis of the Stertomys species occurring in each fissure filling confirm the outline of the proposed biochronological framework and permit some improvement of the definition of the populating phases of the Gargano palaeoisland. Besides, they confirm the presence of some problems in arranging the details of the fissure succession of the oldest phase. Such uncertainties are possibly due to the frequentfaunal exchanges among the islands of the palaeoarchipelago and with the mainland during the time documented by this early phase. The results of the present contribution also suggest that an early radiation occurred in the palaeoarchipelago, producing at least five lineages. These lineages can be arranged in two main branches characterised by different size and morphology. Large-sized Stertomys species, although closely related, cannot be considered as belonging to the samephyletic lineage. Among the small-sized taxa, S. daamsi and S. degiulii might be arranged in a single phyletic lineage where a trend in reduction in size and an increase of the complexity of the pattern of connection among crests occur. S. simplex may be considered as a species with primitive morphology, very close to the ancestor of S. daamsi. Most of the evolutionary divergence is observed among the different lineages, while phyletic gradualistic changes are documented to a lesser extent.
When the car ferry “Rethymnon” sails from Piraeus towards Crete one can already feel the strong endemic atmosphere of the island. Rethymnon itself is a beautiful historical town on Crete in an area containing many Pleistocene fossil mammal localities which have yielded endemic deer, elephants and murids. A striking thing on board the ferry are notices written in Japanese which suggest that the ship was probably not launched under the name Rethymnon and served in her earlier days on the Japanese islands. For a paleontologist this is a remarkable coincidence since the Pleistocene of Japan has also yielded unbalanced endemic faunas with a very uniform composition of elephant and deer like the fauna of Crete.
Most suggested Quaternary land-bridges to mediterranean islands are geologically impossible. In an attempt to explain the presence of the vearious species, modes and ecological consequences of Quaternary island colonization by large mammals and main in the Mediterranean are discussed from a hypothetical point of view, as are the reasons for the extinction of the Quaternary fauna. Small aboricole mammals may have reached the islands on vegetation-rafts. Some larger mammals, like Myotragus on the Balearic Islands, Prolagus on Sardinia, and possibly endemic deer on the Aegean islands, could be relics of the desiccation of the Mediterranean on the Mio/Pliocene border. Hippos, elephants and giant deer reached the islands by swimming. At the arrival of new species, older endemic species became extinct by ecological competition. Overpopulation consisting of a single or few species with corresponding damages to the vegetation led to dwarfing and a adaptation to hard foods. Because of the lack of carnivores, the genetical fixed behavior patterns for flight and attack are lost in island endemics. During hte Middle (Corso-Sardinia) and Upper Pleistocene, suspected or established (Sardinia, Cyprus, Sicily) invasion of Homo sp. led to the near-complete extinction of the unwary endemic fauna. Some islands (Sicily, corso-Sardinia) were repopulated by swimming ungulates which were extermined by later human invasions. For lack of game, a permanent human settlement was nearly impossible before the Neolithic. All extant wild ungulates on the Mediterranean islands are feral domestic animals, or continental game with intact behavioural patterns introduced for religious or hunting purposes during the Neolithic or later. None of them has Pleistocene ancestors on the islands.