Article

Morphological Evolution Of The Scapula In Tree Squirrels, Chipmunks, And Ground Squirrels (Sciuridae): An Analysis Using Thin‐Plate Splines

December 1993
Evolution 47(6):1854-1873

DOI:10.1111/j.1558-5646.1993.tb01274.x

Authors:

University of Michigan

The mammalian scapula, like many bones, is a single structural element that serves as an attachment site for several muscles. The goal of this study was to determine whether the scapula evolves as an integrated unit, or as a collection of distinct parts. Shape differences among the scapulae of tree squirrels, chipmunks, and ground squirrels were described using thin-plate spline analysis. This technique produces a geometric description of shape differences that can be decomposed into a series of components ranging in scale from features that span the entire form to features that are highly localized. Shape differences among tree squirrel scapulae were found only in large-scale features, indicating spatially integrated shape change. Chipmunks and ground squirrels differ from tree squirrels in several features, but shared differences reflecting divergence of their common ancestor were found only in the small-scale features. Divergence of ground squirrels from the common ancestor involved some large-scale changes but was dominated by small-scale changes. Divergence of chipmunks was dominated by large-scale changes. Thus, the scapula evolved as an integrated unit during some transitions but as a collection of distinct parts during others. These results suggest that evolutionary patterns of the postcranial skeleton may be as complex as the patterns that have been described for skulls and feeding mechanisms.

The morphology of the scapula and femur of sciuromorph rodents in light of scaling, lifestyle, homoplasy, and macroevolutionary modelling

Thesis

Oct 2020

Jan Wölfer

Der Bewegungsapparat der Sciuromorpha, einer monophyletische Gruppe von ca. 300 Arten, wurde verwendet um den Effekt der Lebensweise und der Körpermasse auf die Scapula- und Femurmorphologie zu untersuchen. Diese Nagetierklade weist eine breite Vielfalt an Lebensweisen (arboreal, fossoriell, aerial) als auch Körpermassen (drei Größenordnungen umfassend) auf. Die fossorielle Lebensweise hat sich höchstwahrscheinlich dreimal unabhängig von einem arborealen Vorfahren entwickelt. Mehr als die Hälfte der rezenten Arten wurden untersucht. Die Scapulae wurden fotografiert, während Computertomographie (CT) und Oberflächenlaserscans für die Femora verwendet wurden. Es wurden funktionsrelevante Merkmale analysiert, wie die effektive Länge der Skelettelemente, die Muskeleigenschaften soweit aus der Geometrie der Knochen ableitbar, sowie die Robustheit. Die CT-Scans wurden verwendet, um die Querschnitts- und Trabekeleigenschaften des Femurs zu analysieren. Die Gestalt wurde mittels geometrischer Morphometrie untersucht. Phylogenetic comparative methods wurden unter anderem verwendet, um den Einfluss der Phylogenie zu beurteilen als auch, ob sich die unabhängige Aneignung einer fossoriellen Lebensweise in der Evolution homoplastischer Morphologien widerspiegelt. Die Phylogenie spielte bei der Merkmalsevolution eine vernachlässigbare Rolle. Das Auftreten signifikanter Merkmalsunterschiede zwischen den Lebensweisen sowie allometrischer Anpassungen aufgrund Veränderungen in der Körpermasse hingen von dem jeweiligen Merkmal ab. Bei einigen Merkmalen unterschied sich der Einfluss der Körpermasse signifikant zwischen den einzelnen Lebensweisen, was aber nicht die Regel zu sein scheint. Die Evolution homoplastischer Morphologien war sehr unwahrscheinlich bei den fossoriellen Gruppen. Diese Ergebnisse deuten auf eine komplexe, aber adaptive Evolutionsgeschichte dieser Skelettelemente bei den Sciuromorpha hin.

Thin–plate spline analysis of the cranial base in subjects with Class III maloclusion

Article

Full-text available

Sep 1997

The role of the cranial base in the emergence of Class III malocclusion is not fully understood. This study determines deformations that contribute to a Class III cranial base morphology, employing thin-plate spline analysis on lateral cephalographs. A total of 73 children of European-American descent aged between 5 and 11 years of age with Class III malocclusion were compared with an equivalent group of subjects with a normal, untreated, Class I molar occlusion. The cephalographs were traced, checked and subdivided into seven age- and sex-matched groups. Thirteen points on the cranial base were identified and digitized. The datasets were scaled to an equivalent size, and statistical analysis indicated significant differences between average Class I and Class III cranial base morphologies for each group. Thin-plate spline analysis indicated that both affine (uniform) and non-affine transformations contribute toward the total spline for each average cranial base morphology at each age group analysed. For non-affine transformations, Partial warps 10, 8 and 7 had high magnitudes, indicating large-scale deformations affecting Bolton point, basion, pterygo-maxillare, Ricketts' point and articulare. In contrast, high eigenvalues associated with Partial warps 1–3, indicating localized shape changes, were found at tuberculum sellae, sella, and the frontonasomaxillary suture. It is concluded that large spatial-scale deformations affect the occipital complex of the cranial base and sphenoidal region, in combination with localized distortions at the frontonasal suture. These deformations may contribute to reduced orthocephalization or deficient flattening of the cranial base antero-posteriorly that, in turn, leads to the formation of a Class III malocclusion.

The Geometry of the Marmot (Rodentia: Sciuridae) Mandible: Phylogeny and Patterns of Morphological Evolution

Article

May 2003

Andrea Cardini

Marmots have a prominent role in the study of mammalian social evolution, but only recently has their systematics received the attention it deserves if sociobiological studies are to be placed in a phylogenetic context. Sciurid morphology can be used as model to test the congruence between morphological change and phylogeny because sciurid skeletal characters are considered to be inclined to convergence. However, no morphological study involving all marmot species has ever been undertaken. Geometric morphometric techniques were applied in a comparative study of the marmot mandible. The adults of all 14 living marmot species were compared, and mean mandible shape were used to investigate morphological evolution in the genus Marmota. Three major trends were observed. First, the phylogenetic signal in the variation of landmark geometry, which describes mandible morphology, seems to account for the shape differences at intermediate taxonomic levels. The subgenera Marmota and Petromarmota, recently proposed on the basis of mitochondrial cytochrome b sequence, receive support from mandible morphology. When other sciurid genera were included in the analysis, the monophyly of the genus Marmota and that of the tribe Marmotini (i.e., marmots, prairie dogs, and ground squirrels) was strengthened by the morphological data. Second, the marmotine mandible may have evolved as a mosaic of characters and does not show convergence determined by size similarities. Third, allopatric speciation in peripheral isolates may have acted as a powerful force for modeling shape. This hypothesis is strongly supported by the peculiar mandible of M. vancouverensis and, to a lesser degree, by that of M. olympus, both thought to have originated as isolated populations in Pleistocene ice-free refugia.

Brief Communication: Morphological Effects of Captivity: A Geometric Morphometric Analysis of the Dorsal Side of the Scapula in Captive-Bred and Wild-Caught Hominoidea

Article

Full-text available

Aug 2013
AM J PHYS ANTHROPOL

Many osteological collections from museums and research institutions consist mainly of remains from captive-bred animals. The restrictions related to the space of their enclosures and the nature of its substrate are likely to affect the locomotor and postural behaviors of captive-bred animals, which are widely considered uninformative regarding bone morphology and anatomical adaptations of wild animals, especially so in the case of extant great apes. We made a landmark-based geometric morphometrics analysis of the dorsal side of the scapular bone of both wild-caught and captive-bred great apes to clarify the effect of captivity on the morphology of a bone greatly involved in locomotion. The comparison suggested that captivity did not have a significant effect on the landmark configuration used, neither on average scapular shape nor shape variability, being impossible to distinguish the scapulae of a captive-bred animal from that of a wild-caught one. This indicates that the analyzed scapulae from captive Hominoidea specimens may be used in morphological or taxonomic analyses since they show no atypical morphological traits caused by living conditions in captivity. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.

Separating Size from Allometry: Analysis of Lower Jaw Morphology in the Fox Squirrel, Sciurus niger

Article

Full-text available

Aug 2003

Donald L Swiderski

The fundamentals of mechanics provide a strong basis for the hypothesis that allometry could be an important constraint on evolutionary changes in shape. Empirical evidence that allometry accounts for sufficient shape variation to be an effective constraint is much weaker. Numerous studies claim to show that most shape variation is correlated with size, but nearly all these studies use morphometric methods that confound size and shape. Consequently, the proportion of the shape variation correlated with size remains unknown. To address this issue, I examined ontogenetic change and adult variation in lower jaws of the fox squirrel, Sciurus niger. Jaw morphologies were quantified using traditional distance measurements and geometric shape variables computed from landmark coordinates. The same analyses were performed on each data set. As expected, analyses of the distance measurements found that allometry accounted for nearly all ontogenetic variation. The same analysis on the coordinate data found that allometry accounts for <50% of the ontogenetic variation in shape. In analyses of adults, allometry explained >50% of the variation in distance measurements but <25% of the variation in shape. These results confirm that analyses of distance measurements confound size and shape and that this can lead to erroneous claims about the importance of allometry.

Advances in insectivore and rodent systematics due to geometric morphometrics

Article

Feb 2009
MAMMAL REV

Lenka Barčiová

Morphometrics, the study of the variation and change in form amongst organisms, serves as a basic methodological tool in various fields of biological research, including systematics. Because it includes information about spatial relationships amongst anatomical landmarks, geometric morphometrics is more suitable for analyzing morphometric variation than methods based on distance measurements. Geometric morphometrics allows us to answer general ecological and evolutionary questions about shape. In this paper, landmark‐based methods are described and illustrated, based on a dataset of measurements from 295 Apodemus mandibles, and the applications of such methods in the systematics of insectivores (Eulipotyphla) and rodents (Rodentia) are summarized.

Evolution of Scapula Size and Shape in Didelphid Marsupials (Didelphimorphia: Didelphidae)

Article

May 2009
EVOLUTION

Diego Astúa

The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades.

Computer-aided morphological analysis for maxillo-facial diagnostic: a preliminary study

Article

Jan 2009

This article compares most of the three-dimensional (3D) morphometric methods currently proposed by the technical literature to evaluate their morphological informative value, while applying them to a case study of five patients affected by the malocclusion pathology. The compared methods are: conventional cephalometric analysis (CCA), generalised Procrustes superimposition (GPS) with principal-components analysis (PCA), thin-plate spline analysis (TPS), multisectional spline (MS) and clearance vector mapping (CVM). The results show that MS provides more reliable and useful diagnostic information.

Inferring the locomotor ecology of two of the oldest fossil squirrels: influence of operationalization, trait, body size and machine learning method

Article

Full-text available

Nov 2024
Proc Biol Sci

Correlations between morphology and lifestyle of extant taxa are useful for predicting lifestyles of extinct relatives. Here, we infer the locomotor behaviour of Palaeosciurus goti from the middle Oligocene and Palaeosciurus feignouxi from the lower Miocene of France using their femoral morphology and different machine learning methods. We used two ways to operationalize morphology, in the form of a geometric morphometric shape dataset and a multivariate dataset of 11 femoral traits. The predictive models were built and tested using more than half (180) of the extant species of squirrel relatives. Both traditional models such as linear discriminant analysis and more sophisticated models like neural networks had the greatest predictive power. However, the predictive power also depended on the operationalization and the femoral traits used to build the model. We also found that predictive power tended to improve with increasing body size. Contrary to previous suggestions, the older species, P. goti, was most likely arboreal, whereas P. feignouxi was more likely terrestrial. This provides further evidence that arboreality was already the most common locomotor ecology among the earliest squirrels, while a predominantly terrestrial locomotor behaviour evolved shortly afterwards, before the vast establishment of grasslands in Europe.

Ağaç (Sciurus anomalus) ve Yer (Spermophilus xanthoprymnus) Sincaplarının Kafa Kemikleri Üzerinde Karşılaştırmalı Geometrik Morfometrik Çalışma A Comparative Geometric Morfometric Study on Skull Bones of Tree (Sciurus anomalus) and Ground (Spermophilus xanthoprymnus)Squirrels

Article

Full-text available

Jan 2009

In this study, 10 tree squirrels (Sciurus anomalus) and 9 ground squirrels (Spermophilius xanthoprymnus) was used. For geometric morfometrics analysis, 15 homologous landmarks in the dorsal view and 16 homologous landmarks in the ventral view of the skull of both species were used. The differences in the dorsal face of the skull of both species were much more evident compared to the ventral face of the skull. The relative warp analysis based on geometric morphometrics in dorsal and ventral view of the skull of the tree and ground squirrels was found as Rw1 % 65.50, Rw2 % 12.35 and Rw1 % 53.33, Rw2 % 12.71 respectively. The gathering into groups on the axis of both species were clearly demonstrated the geometric, anatomical, and morphological differences. The differences in the dorsal view of the skull, especially in the level of the end point of the proc. zygomaticus and the incisura supraorbitale of the os frontale in TPS analysis were quite evident. On the other hand, the most differences in ventral view of the skull of both species was the level of the posterior point of the os palatinum, the middle of the upper teeth, posterior edge of the for. magnum, and the tuber faciale.

The squirrel is in the detail: Anatomy and morphometry of the tail in Sciuromorpha (Rodentia, Mammalia)

Article

Sep 2021

In mammals, the caudal vertebrae are certainly among the least studied elements of their skeleton. However, the tail plays an important role in locomotion (e.g., balance, prehensility) and behavior (e.g., signaling). Previous studies largely focused on prehensile tails in Primates and Carnivora, in which certain osteological features were selected and used to define tail regions (proximal, transitional, distal). Interestingly, the distribution pattern of these anatomical characters and the relative proportions of the tail regions were similar in both orders. In order to test if such tail regionalization can be applied to Rodentia, we investigated the caudal vertebrae of 20 Sciuridae and six Gliridae species. Furthermore, we examined relationships between tail anatomy/morphometry and locomotion. The position of selected characters along the tail was recorded and their distribution was compared statistically using Spearman rank correlation. Vertebral body length (VBL) was measured to calculate the proportions of each tail region and to perform procrustes analysis on the shape of relative vertebral body length (rVBL) progressions. Our results show that tail regionalization, as defined for Primates and Carnivora, can be applied to almost all investigated squirrels, regardless of their locomotor category. Moreover, major locomotor categories can be distinguished by rVBL progression and tail region proportions. In particular, the small flying squirrels Glaucomys volans and Hylopetes sagitta show an extremely short transitional region. Likewise, several semifossorial taxa can be distinguished by their short distal region. Moreover, among flying squirrels, Petaurista petaurista shows differences with the small flying squirrels, mirroring previous observations on locomotory adaptations based on their inner ear morphometry. Our results show furthermore that the tail region proportions of Petaurista petaurista, phylogenetically more basal than the small flying squirrels, are similar to those of bauplan-conservative arboreal squirrels.

Geometric morphometric approach to understand the body shape variation in the pony fishes (Leiognathidae) of Odisha coast, India.

Article

Full-text available

Sep 2019

Landmark-based geometric morphometric (GM) analysis was carried out in the present study on the species of the family Leiognathidae. Pattern of shape variation along the axes of the principal components and canonical variates were analyzed after the General Procrustes analysis. Canonical variates analysis confirmed the occurrence of eleven species of the family Leiognathidae along the Gopalpur-on-Sea, Odisha coast. Further, inter-specific shape variation among the species of the family were carried out using Discriminant function analysis, which would help us to understand the morphological divergence with respect to shape.

Femoral morphology of sciuromorph rodents in light of scaling and locomotor ecology

Article

Full-text available

Apr 2019

Sciuromorph rodents are a monophyletic group comprising about 300 species with a body mass range spanning three orders of magnitude and various locomotor behaviors that we categorized into arboreal, fossorial and aerial. The purpose of this study was to investigate how the interplay of locomotor ecology and body mass affects the morphology of the sciuromorph locomotor apparatus. The most proximal skeletal element of the hind limb, i.e. the femur, was selected, because it was shown to reflect a functional signal in various mammalian taxa. We analyzed univariate traits (effective femoral length, various robustness variables and the in‐levers of the muscles attaching to the greater, third and lesser trochanters) as well as femoral shape, representing a multivariate trait. An ordinary least‐squares regression including 177 species was used to test for a significant interaction effect between body mass and locomotor ecology on the variables. Specifically, it tested whether the scaling patterns of the fossorial and aerial groups differ when compared with the arboreal, because the latter was identified as the ancestral sciuromorph condition via stochastic character mapping. We expected aerial species to display the highest trait values for a given body mass as well as the steepest slopes, followed by the arboreal and fossorial species along this order. An Ornstein–Uhlenbeck regression fitted to a phylogenetically pruned dataset of 140 species revealed the phylogenetic inertia to be very low in the univariate traits, hence justifying the utilization of standard regressions. These variables generally scaled close to isometry, suggesting that scaling adjustments might not have played a major role for most of the femoral features. Nevertheless, the low phylogenetic inertia indicates that the observed scaling patterns needed to be maintained during sciuromorph evolution. Significant interaction effects were discovered in the femoral length, the centroid size of the condyles, and the in‐levers of the greater and third trochanters. Additionally, adjustments in various femoral traits reflect the acquisitions of fossorial and aerial behaviors from arboreal ancestors. Using sciuromorphs as a focal clade, our findings exemplify the importance of statistically accounting for potential interaction effects of different environmental factors in studies relating morphology to ecology.

A deformable template method for describing and averaging the anatomical variation of the human nasal cavity

Article

Full-text available

Oct 2016
BMC Med Imag

Background Understanding airflow through human airways is of importance in drug delivery and development of assisted breathing methods. In this work, we focus on development of a new method to obtain an averaged upper airway geometry from computed tomography (CT) scans of many individuals. This geometry can be used for air flow simulation. We examine the geometry resulting from a data set consisting of 26 airway scans. The methods used to achieve this include nasal cavity segmentation and a deformable template matching procedure. Methods The method uses CT scans of the nasal cavity of individuals to obtain a segmented mesh, and coronal cross-sections of this segmented mesh are taken. The cross-sections are processed to extract the nasal cavity, and then thinned (‘skeletonized’) representations of the airways are computed. A reference template is then deformed such that it lies on this thinned representation. The average of these deformations is used to obtain the average geometry. Our procedure tolerates a wider variety of nasal cavity geometries than earlier methods. ResultsTo assess the averaging method, key landmark points on each of the input scans as well as the output average geometry are located and compared with one another, showing good agreement. In addition, the cross-sectional area (CSA) profile of the nasal cavities of the input scans and average geometry are also computed, showing that the CSA of the average model falls within the variation of the population. Conclusions The use of a deformable template method for aligning and averaging the nasal cavity provides an improved, detailed geometry that is unavailable without using deformation.

Taxonomic Revision Of Elimia Christyi And E. Interrupta (Mollusca: Caenogastropoda: Pleuroceridae)

Article

Full-text available

Nov 2004
ZOOTAXA

An examination of museum material indicated that the lectotypes of Goniobasis christyi Lea, 1862 and G. instabilis Lea, 1862, along with recent collections of putative Elimia interrupta (Haldeman, 1840), represent a new species separate from E. interrupta, sensu stricto. We propose the name E. christyi for the new species, and provide re-descriptions of it and E. interrupta.

Ontogenetic Variation in Skull Shape of Thrichomys apereoides (Rodentia: Echimyidae)

Article

Feb 1999

The pattern of change in shape during postnatal development in skulls of punare (Thrichomys apereoides) skulls, was studied by geometric morphometric techniques. Skull shape observed in T. apereoides varied both with size and age, but variation in size explains most of the overall change in shape. Differences in shape observed among the eight age categories showed that main changes in shape occurred principally between the first and second age categories. Among the other age classes, changes became less pronounced leading to elongation of the snout and the mid-face and narrowing of the basicranium. The change in global shape resulted in lateral compression of the skull. Despite the high level of integration observed, localized transformations dominated the ontogenetic changes in shape indicating the presence of two large scale cranium components-the orofacial and the basicranial region. The ontogenetic pattern in this species seems to follow the same trends observed in the initial phases of development.

Comparing Wing Shape of Bats: The Merits of Principal-Components Analysis and Relative-Warp Analysis

Article

Nov 1997

James M Birch

Size and shape are fundamental features of organisms. Ideally, the methods used to describe size and shape must be sensitive enough to detect small differences, and at the same time provide interpretation that is visually satisfying. I compared shape of wings among Eptesicus fuscus, Myotis lucifugus, Pipistrellus hesperas, and Tadarida brasiliensis using three methods of morphometric analysis; principal-components analysis on traditional measures of lengths and areas, principal-components analysis of interlandmark distances, and relative-warp analysis. These species were chosen to test the efficacy of each morphometric analysis at discovering and describing differences in both size and shape. Although principal-components analyses provided similar aggregations of species based on variable loadings, only relative-warps analysis provided clear pictures as to how species differ. The molossid bat, T. brasiliensis, had narrower wings than the vespertilionid bats; this shape was not due to compression of the entire wing, but to a complicated rotation around the fifth digit. The vespertilionid bats were difficult to discern based on wing shape alone, but the warp analysis showed that P. Hesperus and M. lucifugus are more similar in shape of wing than either is to E. fuscus. Each method of analysis of shape has strengths, but relative-warp analysis provided both the power to discriminate among minor differences in shape of species within families, and the graphical capability to display those differences in a visually pleasing way.

Geometric morphometrics as a tool for interpreting evolutionary transitions in the black fly wing (Diptera: Simuliidae)

Article

Nov 2013

A geometric morphometric analysis was conducted on wing-vein landmarks on exemplar species of the family Simuliidae of the following genera: Parasimulium, Gymnopais, Twinnia, Helodon, Prosimulium, Greniera, Stegopterna, Tlalocomyia, Cnephia, Ectemnia, Metacnephia, Austrosimulium, and Simulium. Generalized least squares superimposition was performed on landmarks, followed by a principal component analysis on resulting Procrustes distances. Patterns of shape change along the principal component axes were visualized using the thin-plate spline. The analysis revealed wing shape diversity through (1) the insertion points of the subcosta and R1, resulting in the terminus of the costa exhibiting a trend towards a more apical position on the wing, and (2) the insertion point of the humeral cross vein, resulting in the anterior branch of the media exhibiting a trend toward a more basal position on the wing. Canonical variates analysis of Procrustes distances successfully assigned all exemplar species into their a priori taxonomic groupings. The diversity in wing shape reveals a trend towards decreased length of basal radial cell and increased costalization of anterior wing veins in the evolutionary transition from plesiomorphic prosimuliines to more derived simuliines. The functional significance of these evolutionary transitions is discussed.

Geometric Morphometric Analysis of Patterns of Shape Change in the Ordovician Brachiopod Sowerbyella

Article

Full-text available

Apr 2001

The brachiopod genus Sowerbyella is an abundant component of many Ordovician paleocommunities of the eastern United States. Five successive populations from a limited geographic region in central Kentucky were tested for the response of brachial valve size and shape to alterations in paleoenvironmental conditions. The populations span the interval from Chatfieldian to Maysvillian (M5-C3) including the majority of an Ecological-Evolutionary (EE) subunit previously described for brachiopods in this area. A marked diminution in size occurs subsequent to maximum deepening in the M5 sequence, and is persistent for the remainder of the interval sampled. Shape follows a different pattern, with similar changes occurring each time deep-water facies occur in the area. Discriminant analysis shows a clear separation between populations sampled from nearshore and offshore facies along discriminant function 1. End member populations in both nearshore and offshore populations diverge significantly on discriminant function 2 over periods of 6.5 and 3.5 my, respectively, the longer period spanning the majority of the EE subunit. This contrasts with stasis in valve shape in Devonian. brachiopods over an EE subunit of similar duration, but is in accordance with previous findings of less community-level stability in Ordovician EE subunits when compared with their Devonian counterparts.

Morphometric Analysis of the Superior Vestibular Nerve in Ground and Tree Squirrels (Sciuridae)

Article

Feb 2001

Using light microscospy, cross sections of the superior vestibular nerve were compared in 2 tree-dwelling species of squirrels (Sciurus carolinensis and S. niger) and 3 ground-dwelling species (Spermophilus tridecemlineatus, S. mexicanus, and S. variegatus). Fiber number, internal minor diameter of the axon, and axon area were measured for 31,959 fibers taken from 5 males of each species. Significant differences were not found within or among species, suggesting that climbing behaviors are not correlated with these morphologic features of the superior vestibular nerve.

Geometric Morphometric Character Suites as Phylogenetic Data: Extracting Phylogenetic Signal from Gastropod Shells

Article

Jan 2013
SYST BIOL

Despite being the objects of numerous macroevolutionary studies, many of the best-represented constituents of the fossil record-including diverse examples such as foraminifera, brachiopods, and mollusks-have mineralized skeletons with limited discrete characteristics, making morphological phylogenies difficult to construct. In contrast to their paucity of phylogenetic characters, the mineralized structures (tests and shells) of these fossil groups frequently have distinctive shapes that have long proved useful for their classification. The recent introduction of methodologies for including continuous data directly in a phylogenetic analysis has increased the number of available characters, making it possible to produce phylogenies based in whole or part on continuous character data collected from such taxa. Geometric morphometric methods provide tools for accurately characterizing shape variation and can produce quantitative data that can therefore now be included in a phylogenetic matrix in a non-arbitrary manner. Here, the marine gastropod genus Conus is used to evaluate the ability of continuous characters-generated from a geometric morphometric analysis of shell shape-to contribute to a total evidence phylogenetic hypothesis constructed using molecular and morphological data. Furthermore, the ability of continuous characters derived from geometric morphometric analyses to place fossil taxa with limited discrete characters into a phylogeny with their extant relatives was tested by simulating the inclusion of fossil taxa. This was done by removing the molecular partition of individual extant species to produce a "cladistic pseudofossil" with only the geometric morphometric derived characters coded. The phylogenetic position of each cladistic pseudofossil taxon was then compared with its placement in the total evidence tree and a symmetric resampling tree to evaluate the degree to which morphometric characters alone can correctly place simulated fossil species. In 33-45% of the test cases (depending upon the approach used for measuring success), it was possible to place the pseudofossil taxon into the correct regions of the phylogeny using only the morphometric characters. This suggests that the incorporation of extinct Conus taxa into phylogenetic hypotheses will be possible, permitting a wide range of macroevolutionary questions to be addressed within this genus. This methodology also has potential to contribute to phylogenetic reconstructions for other major components of the fossil record that lack numerous discrete characters.

Are long digits correlated with high forepaw dexterity? A comparative test in terrestrial carnivores (Carnivora)

Article

Full-text available

Nov 2001

The relationship between manus proportions and forepaw dexterity in 33 species of carnivores (Carnivora) was examined. Both the analysis of "raw" data and independent contrasts revealed no significant correlation between the metacarpal-phalanx (MCP) ratio and forepaw dexterity. This result was corroborated by a common origins test, which indicated that changes in the MCP ratio were not coincident with changes in forepaw dexterity throughout carnivore evolution. Together, these results suggest that the morphological basis for variations in manipulative behaviour may be quite complex. Other morphological features, such as manus and carpal shape and myology, may play a critical role in forepaw dexterity, but are not manifested as changes in manus proportions. Behavioural observations also suggest that manus proportions may be correlated more closely with locomotion rather than non-locomotory forepaw usage.

spatiotemporal reorganization of growth rates in the evolution of ontogeny

Article

Full-text available

Aug 2000

Heterochrony, evolutionary changes in rate or timing of development producing parallelism between ontogeny and phylogeny, is viewed as the most common type of evolutionary change in development. Alternative hypotheses such as heterotopy, evolutionary change in the spatial patterning of development, are rarely entertained. We examine the evidence for heterochrony and heterotopy in the evolution of body shape in two clades of piranhas. One of these is the sole case of heterochrony previously reported in the group; the others were previously interpreted as cases of heterotopy. To compare ontogenies of shape, we computed ontogenetic trajectories of shape by multivariate regression of geometric shape variables (i.e., partial warp scores and shape coordinates) on centroid size. Rates of development relative to developmental age and angles between the trajectories were compared statistically. We found a significant difference in developmental rate between species of Serrasalmus, suggesting that heterochrony is a partial explanation for the evolution of body shape, but we also found a significant difference between their ontogenetic transformations; the direction of the difference between them suggests that heterotopy also plays a role in this group. In Pygocentrus we found no difference in developmental rate among species, but we did find a difference in the ontogenies, suggesting that heterotopy, but not heterochrony, is the developmental basis for shape diversification in this group. The prevalence of heterotopy as a source of evolutionary novelty remains largely unexplored and will not become clear until the search for developmental explanations looks beyond heterochrony.

Geometric morphometrics and the development of complex structures: ontogenetic changes in scapular shape of dasypodid armadillos

Article

Full-text available

Jun 2000

Leandro Rabello Monteiro

Abstract The ontogenetic development of the scapula of Euphractus sexcinctus and Dasypus novemcinctus was studied using geometric morphometrics techniques. The relative importance of uniform, large, and small scale shape changes on ontogenetic development was assessed both by multivariate regression of shape on size and by relative warps analysis. The scapular development in both species is very similar and is characterized (and dominated) by an enlargement of the teres major process. This process serves as origin for the teres major muscle, which is responsible for limb retraction (an important function for digging behavior). There is also a global increase in relative anteroposterior length, increasing the moment arm of this muscle. The uniform shape changes during development are responsible for a small percentage of the size-based shape variation in Euphractus, and for a large percentage in Dasypus. The large scale localized shape changes (which depict the teres major process enlargement) are responsible for a large percentage of size-based shape variation. The region of the coracoid process and glenoid cavity are almost unaltered during the ontogeny in both species.

Soft Tissue Diagnosis in Maxillofacial Surgery: A Preliminary Study on Three-Dimensional Face Geometrical Features-Based Analysis

Article

Full-text available

Sep 2009
AESTHET PLAST SURG

To obtain the best surgical results in orthognathic surgery, treatment planning and evaluation of results should be performed. In these operations it is necessary to provide the physician with powerful tools that can underline the behavior of soft tissue. For this reason, considering the improvements provided by the use of 3D scanners in medical diagnosis, we propose a methodology for analyzing facial morphology working with geometrical features. The methodology has been tested on patients with malocclusion in order to analyze the reliability and efficiency of the provided diagnostic results.

Cambios en la forma de la pata posterior entre roedores sigmodontinos según su locomoción y hábitat

Article

Full-text available

Dec 2006

Los cambios de forma de la pata posterior fueron comparados y relacionados entre nueve géneros de sigmodontinos de la Guayana venezolana, utilizando la técnica geométrica ¿Thin Plate Spline¿. Los resultados mostraron que entre estos taxones se pueden distinguir tres tipos de forma según sus adaptaciones: terrestres de vegetación boscosa (Neacomys, Oryzomys), terrestres de vegetación abierta (Necromys, Sigmodon, Zygodontomys) y trepadores- arbóreos (Oecomys, Rhipidomys). Los primeros se caracterizan por presentar una superficie plantar alargada, dedos medios largos y garras cortas; los segundos presentan dedos cortos y garras largas; y los terceros superficie plantar y garras cortas, y dedos largos. En la forma semiacuática (Nectomys) la pata fue similar a los terrestres de vegetación boscosa, mientras que Oligoryzomys, considerando dentro de los terrestres, presentó más semejanza con los trepadores-arbóreos.

The Impact of Muscular Dystrophy on Limb Bone Growth and Scaling in Mice

Article

Full-text available

Feb 1998

Muscular loading affects bone growth and the factors determining size and shape. However, it is not known what epigenetic impact muscular dystrophy (dystrophia muscularis) has on limb bone growth or ontogenetic scaling. To assess the effects of two types of muscular dystrophy (genotypes dy/dy and dy2J/dy2J) on limb bone growth, we measured lengths and widths of the right humerus, femur and tibia, and lengths of the ulna and radius from dorsal/ventral radiographs of mice taken over a period of 270 days. Radiographs were taken approximately 3 times a week, and the sampling frequency was gradually reduced to once a month. We plotted measurements from each individual against time and fit a Gompertz equation to the growth of each bone. Parameters of the equation were compared using ANOVA across genotypes and between sexes. Slopes of length versus width were calculated for the limb bones of each individual using linear regression. Slope differences among genotypes and between sexes were tested using ANOVA. Control and dy2J values were significantly longer than those of dy mice in all bones, but there was considerable variation across genotypes for the various width measurements. Sexual dimorphism was found in several measurements, where males were always larger than females. There were few significant differences in limb scaling (lengths vs. widths) among genotypes and almost no scaling differences between sexes despite the size differences. Differences among widths suggest that muscular dystrophy affects different parts of limb bones in different ways. This may be the effect of the type and number of muscular attachments, as well as the usage of the limb. The sexually dimorphic measurements suggest that there are size differences in the skeleton between sexes, regardless of the genotype. Our ontogenetic allometry results indicate that size is affected by the muscular dystrophic condition and by sexual dimorphism, while shape remains largely unchanged.

Spatiotemporal reorganization of growth rates in the evolution of ontogeny

Article

Sep 2000

A comparison of the ontogeny of shape variation in the anthropoid scapula: Functional and phylogenetic signal

Article

Full-text available

Jul 2008
AM J PHYS ANTHROPOL

Nathan M. Young

This article compares ontogenetic shape variation in the scapula of 17 anthropoid species using three-dimensional landmark-based geometric morphometrics. These data are used to investigate functional and phylogenetic signal in the major components of scapular variation and to evaluate the degree to which postnatal growth contributes to interspecific differences in shape. Results indicate that the shape of the infant and adult scapula is primarily associated with positional behavior (e.g., orthograde suspensory nonquadrupeds versus pronograde quadrupeds), but within this functional structure there is phylogenetic signal, particularly at infant stages. Growth most closely correlates with infant/adult shape and locomotor function. These results suggest that the shape of the infant scapula drives the pattern of postnatal scapular growth and adult morphology. As such, variation in postnatal growth is not the primary source of interspecific variation in adult shape. Instead, interspecific differences in scapular morphology are hypothesized to be the result of selection for variation in embryonic developmental processes that affect shape.

THE MORPHO-FUNCTIONAL PECULIARITIES OF THE SYNSARCOSIS MUSCLES IN RED SQUIRRELS

Article

Full-text available

Dec 2022

In terrestrial species, body propulsion is mostly performed via the pelvic limbs. In semiaquatic species, both pairs of limbs are used in swimming and diving, whereas in arboreal species, the pelvic limbs are used to maintain body stability. Thus, in squirrels, the synsarcosis muscles participate in body propulsion during climbing, as they have well-developed muscular bellies. Among these, the pectoral transverse muscle, which originates along the entire sternum and is inserted on the humeral crest, stands out for its width. The cervical parts of the trapezius and rhomboideus muscles are reduced and their thoracic parts more developed. As a result, muscles such as the occipitoscapularis or atlantoscapularis coordinate forelimb protraction and neck displacement. The serratus ventralis muscle is very well developed and clearly divided into cranial (cervical) and caudal (thoracic) parts; it produces a strong adduction of the thoracic limbs when the parts contract, and when they relax, a large abduction of the forelimbs is produced, enlarging the body size during jumping.

Marsupial versus placental: assessing the evolutionary changes in the scapula of didelphids and sigmodontines

Article

Dec 2019
BIOL J LINN SOC

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.

Themes and variation in sciurid evolution

Chapter

Aug 2015

The widespread use of mouse models in developmental, behavioural and genetic studies has sparked wider interest in rodent biology as a whole. This book brings together the latest research on rodents to better understand the evolution of both living and extinct members of this fascinating group. Topics analysed include the role of molecular techniques in the determination of robust phylogenetic frameworks; how geometric morphometric methods help quantify and analyse variation in shape; and the role of developmental biology in elucidating the origins of skeletal elements and the teeth. The editors unite these disciplines to present the current state of knowledge in rodent biology, whilst setting the landscape for future research. This book highlights interdisciplinary links across palaeontology, developmental biology, functional morphology, phylogenetics and biomechanics, making it a valuable resource for evolutionary biologists in all fields.

Species level phenotypic variation in lower Paleozoic trilobites

Article

Dec 1998
PALEOBIOLOGY

Loren H. Smith

Phenotypic variation within species provides the raw material acted upon by natural selection and other evolutionary mechanisms. As such, the range and variation of morphology within a species can play an important role in determining the tempo of evolution. The range and variance of aspects of cranidial morphology for nine lower Paleozoic trilobites were measured to identify microevolutionary correlates of macroevolutionary patterns. Comparisons were made among sets of homologous landmarks or upon partial warp vector matrices containing similar proportions of variance. Rarefaction and bootstrap analyses helped estimate the effects of sampling. Levels of variance and range of morphology differed considerably within and among time periods. There is no significant temporal decline in the variance or range of morphology, suggesting that developmental or genomic constraints may not have been the primary factors controlling the tempo of trilobite macroevolution. The spatial distribution of cranidial variance differed considerably among taxa, suggesting that a complex set of developmental processes governed the morphogenesis of cranidia within trilobites.

Disparity and constraint in olenelloid trilobites and the Cambrian Radiation

Article

Sep 1999
PALEOBIOLOGY

The Cambrian Radiation marks the appearance of representatives of virtually all major skeletonized phyla in the fossil record and clearly represents a fundamental episode in the history of life. Furthermore, the tempo and mode of this evolutionary event have been the subject of intense debate. One area that has been debated is how so many phylum-level body plans can have evolved in such a geologically brief period. Some have argued that there was enhanced morphological flexibility and fewer evolutionary constraints at this time, leading to greater morphological disparity of Early Cambrian faunas. Others have claimed that this is not true because the evolution of most of the animal phyla significantly predates the radiation or because they failed to detect a signature of decreasing morphological disparity through time. At present, the higher-level patterns of diversification during this time period and the relevant implications for Early Cambrian uniqueness are areas of active research interest and debate. Recognizing this debate, we used both a phylogenetic and a morphometric framework to study whether there is a signature of increasing morphological constraint and decreasing flexibility through time within one of the clades that is a significant constituent of the Early Cambrian biota, specifically, the olenelloid trilobites. In this species-rich clade, we found no evidence that morphological changes were becoming either increasingly constrained or less flexible in one of the dominant Early Cambrian metazoan clades as it passed through the Cambrian Radiation.

Heterochrony and heterotopy: Stability and innovation in the evolution of form

Article

Mar 1996
PALEOBIOLOGY

Heterochrony, change in developmental rate and timing, is widely recognized as an agent of evolutionary change. Heterotopy, evolutionary change in spatial patterning of development, is less widely known or understood. Although Haeckel coined the term as a complement to heterochrony in 1866, few studies have detected heterotopy or even considered the possibility that it might play a role in morphological evolution. We here review the roles of heterochrony and heterotopy in evolution and discuss how they can be detected. Heterochrony is of interest in part because it can produce novelties constrained along ancestral ontogenies, and hence result in parallelism between ontogeny and phylogeny. Heterotopy can produce new morphologies along trajectories different from those that generated the forms of ancestors. We argue that the study of heterochrony has been bound to an analytical formalism that virtually precludes the recognition of heterotopy, so we provide a new framework for the construction of ontogenetic trajectories and illustrate their analysis in a phylogenetic context. The study of development of form needs tools that capture not only rates of development but the space in which the changes are manifest. The framework outlined here provides tools applicable to both. When appropriate tools are used and the necessary steps are taken, a more comprehensive interpretation of evolutionary change in development becomes possible. We suspect that there will be very few cases of change solely in developmental rate and timing or change solely in spatial patterning; most ontogenies evolve by changes of spatiotemporal pattern.

Geometric morphometrics of the scapula of South American caviomorph rodents (Rodentia: Hystricognathi): Form, function and phylogeny

Article

Full-text available

Nov 2009

Cecilia Clara Morgan

The scapula of the ecomorphologically diverse South American caviomorph rodents was studied through geometric morphometric techniques, using landmarks and semilandmarks to capture the shape of this complex morphological structure. Representatives of 33 species from all caviomorph superfamilies, as well as Hystrix cristata for comparisons, were analyzed. Marked differences in scapular shape were found among the major caviomorph lineages analyzed, particularly in the shape and length of the scapular spine and development of the great scapular notch. Shape differences were not influenced by body size, and only partially influenced by locomotor mode. Thus, at this scale of analysis, phylogenetic history seems to be the strongest factor influencing scapular shape. The scapular shape of erethizontids, chinchillids and Cuniculus paca could represent the less specialized state with respect to the highly differentiated scapula of octodontoids and most cavioids. In this sense, the characteristic scapular morphologies of octodontoids and cavioids could reflect particular functional capabilities and constraints associated with the evolution of prevalent locomotor modes within each lineage.

Morphometric analysis of the cranial base in Asians

Article

Feb 2013
ODONTOLOGY

This study tested the hypothesis that developmental heterogeneity in cranial base morphology increases the prevalence of Class III malocclusion and mandibular prognathism in Asians. Thin-plate spline (TPS) graphical analysis of lateral cephalometric radiographs of the cranial base and the upper midface configuration were compared between a European-American group (24 females and 31 males) and four Asian ethnic groups (100 Chinese, 100 Japanese, 100 Korean and 100 Taiwanese; 50 females and 50 males per group) of young adults with clinically acceptable occlusion and facial profiles. Procrustes analysis was performed to identify statistically significant differences in each configuration of landmarks (P < 0.001). The TPS graphical analysis revealed that the greatest differences of Asians were the horizontal compression and vertical expansion in the anterior portion of the cranial base and upper midface region. The most posterior cranial base region also showed horizontal compression between the basion and Bolton point, with forward displacement of the articulare. Facial flatness and anterior displacement of the temporomandibular joint, resulting from a relative retrusion of the nasomaxillary complex and a relative forward position of the mandible were also noted. These features that tend to cause a prognathic mandible and/or retruded midface indicate a morphologic predisposition of Asian populations for Class III malocclusion.

Localization of deformations of the midfacial complex in subjects with Class III malocclusions employing thin-plate spline analysis

Article

Nov 1997
J ANAT

This study determines deformations of the midface that contribute to a class III appearance, employing thin-plate spline analysis. A total of 135 lateral cephalographs of prepubertal children of European-American descent with either class III malocclusions or a class I molar occlusion were compared. The cephalographs were traced and checked, and 7 homologous landmarks of the midface were identified and digitised. The data sets were scaled to an equivalent size and subjected to Procrustes analysis. These statistical tests indicated significant differences (P<0.05) between the averaged class I and class III morphologies. Thin-plate spline analysis indicated that both affine and nonaffine transformations contribute towards the total spline for the averaged midfacial configuration. For nonaffine transformations, partial warp 3 had the highest magnitude, indicating the large scale deformations of the midfacial configuration. These deformations affected the palatal landmarks, and were associated with compression of the midfacial complex in the anteroposterior plane predominantly. Partial warp 4 produced some vertical compression of the posterior aspect of the midfacial complex whereas partial warps 1 and 2 indicated localised shape changes of the maxillary alveolus region. Large spatial-scale deformations therefore affect the midfacial complex in an anteroposterior axis, in combination with vertical compression and localised distortions. These deformations may represent a developmental diminution of the palatal complex anteroposteriorly that, allied with vertical shortening of midfacial height posteriorly, results in class III malocclusions with a retrusive midfacial profile.

Shape analysis using the thin‐plate spline: Neanderthal cranial shape as an example

Article

Jan 1996
AM J PHYS ANTHROPOL

Lucia Yaroch

This paper describes a new geometric method for illustrating and quantifying biological shape difference. The technique is discussed in some detail, and is illustrated by applying it to the problem of characterizing Neanderthal cranial shape. The method of thin-plate splines uses a mathematical model based on the bending of a hypothetical steel plate in order 1) objectively to generate a D'Arcy Thompson-style deformed grid that illustrates the shape contrast between two forms, and 2) to quantify the shape difference by breaking it down into a series of components based on scale. Results confirm the presence of some features traditionally attributed to Neanderthals, but some “classic” Neanderthal features do not in fact characterize the Neanderthal sample. Traits may have been misidentified because of failure to take into account differences in absolute size, use of a misleading frame of reference, and interpretation of one aspect of a large-scale change as a localized feature. In particular, the important Neanderthal “specialization” midfacial prognathism, defined as forward displacement of the nasal region and the tooth row relative to more lateral facial structures, does not appear to be a typical Neanderthal trait. The uniqueness of Neanderthals appears to have been exaggerated, and may be related to Boule's peculiar, flawed reconstruction of the skull of La Chapelle-aux-Saints. The method of thin-plate splines is a powerful technique, capable of providing a new and insightful perspective on morphological problems in physical anthropology. © 1996 Wiley-Liss, Inc.

Evolutionary changes in craniomandibular shape in the great cats (Neofelis Griffith and Panthera Oken)

Article

Nov 2008
BIOL J LINN SOC

Per Christiansen

Evolutionary shape changes in skull and mandibular anatomy was analysed in 223 specimens of pantherine felids (Neofelis nebulosa, Panthera leo, Panthera onca, Panthera pardus, Panthera tigris, Panthera uncia) compared to a small-felid outgroup, consisting of 86 specimens of nine different species, using digital surface morphometry on 25 (skull) and 17 (mandible) landmarks. Shape evolution in the pantherine species is complex and nonlinear, and involves both large-scale and small-scale shape changes. Shape changes frequently differ among the ingroup species, but the four large Panthera species (leo, onca, pardus, tigris) bear some resemblance to each other. The leopard and jaguar bear the closest resemblance to each other, and several shape changes are common to the lion and tiger, but have probably evolved convergently as a result of large size. The lion has undergone the largest and most numerous shape changes from a small-felid outgroup. Certain shape changes in the skull and, in some respects, the mandible of the clouded leopard bear resemblance to those in the four large Panthera species. The snow leopard is often regarded as the most primitive of the extant Panthera, and skull and mandibular shape changes often diverge markedly from those observed in the other five ingroup taxa; its overall skull shape is rather similar to the small-felid outgroup. This indicates that the shape changes in the clouded leopard are convergent with those of the four large Panthera species. Landmark integration showed no significant correlation with molecular phylogeny, chiefly owing to the snow leopard being placed among the four large Panthera species. A traditional phylogenetic topology with the snow leopard as the basal-most species of Panthera yielded a weak but nonsignificant phylogenetic signal. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 766–778.

Relative warp analysis of skull shape across the hybrid zone of the house mouse (Mus musculus) in Denmark

Article

Full-text available

May 2009
J ZOOL

The changes in skull shape that occur in the hybrid zone between the two European subspecies of the house mouse (Mus musculus musculus and M. m. domesticus) were studied by relative warp analyses. Landmarks observed on the ventral view of the skulls of 269 mice sampled in 18 localities in Denmark were analysed. Each population was also characterized by a hybrid index estimated from allozymic data. Although no clear pattern of within-population variability of shape could be established across the hybrid zone, the shape changes among the 18 populations were found to be correlated with the allozymic introgression but not with geographical location. Finally, the cline obtained for skull shape seems to be steeper than that corresponding to the average allozyme hybrid index which suggests that skull development could be slightly perturbed in hybrids.

A Geometric Morphometric Assessment of the Relationship between Scapular Variation and Locomotion in African Apes

Chapter

Jan 2005

In this study, we carried out a GM evaluation of the functional correlates of scapular variation in the African apes using GPA applied to landmark data and compared our findings with previous results based on linear measurements obtained using digital calipers. Scapular size and shape vary between Pan and gorillas, while gorilla subspecies differ only in scapular shape. Shape variation is significant in comparisons between all three groups, with the greatest degree of difference observed between Pan and the two gorilla subspecies. There is, however, no systematic pattern of differentiation that maps predictably to differences in frequency of suspensory or arboreal climbing behaviors. We conclude that the relationship between scapular morphology and locomotor behavior, at least in the African apes, is not a compelling one. Our findings generally confirm patterns of variation between gorillas, and between Pan and gorilla subspecies, observed by previous investigators using conventional distance measurements, and demonstrate the mutually informative nature of GM and other methods of analysis when used to address questions of biological variation.

Positional behavior of Siberian chipmunks (Tamias sibiricus) in captivity

Article

Full-text available

Apr 2008

Arboreal and semi-arboreal mammals have remarkably diverse positional behavior and associated morpho-functional adaptations related to the three-dimensional nature of their arboreal habitat. In this context, we investigated the positional behavior of captive Siberian chipmunks (Tamias sibiricus), small bodied semi-arboreal sciurids, in an aviary-type wire-mesh cage containing both terrestrial and arboreal supports. We sampled four adult individuals during a five-month period using focal animal sampling every 30s. Results showed that animals preferred 8–10cm horizontal supports and always avoided vertical supports. Locomotion occurred on both terrestrial and 8–10cm arboreal supports whereas postural behavior occurred primarily on 8–10cm arboreal supports. Quadrupedal walk dominated during locomotion, and occurred primarily on terrestrial horizontal supports, as is observed for other squirrels. The predominance of quadrupedal locomotion is consistent with the postcranial morphology of chipmunks. In contrast, clawed locomotion occurred on wire mesh and on >13cm arboreal vertical supports. Finally, pronograde and orthograde sitting, both on 8–10cm arboreal supports and on terrestrial supports, were the predominant postures, implying general predisposition to selection of stable postures on stable supports for food item manipulation and ingestion.

Evolutionary convergence of primitive sabertooth craniomandibular morphology: The clouded leopard (Neofelis nebulosa) and Paramachairodus ogygia compared

Article

Sep 2008

Per Christiansen

The sabertoothed felids were among the most unusual predators in the late Tertiary ecosystems, and the sabertooth morphology is regarded as being absent from the modern ecosystems. In recent years, the primitive Paramachairodus has become well known and has yielded much valuable information on the primitive skull morphology among sabercats, providing the first evidence-based scenarios for the evolution of skull morphology in later sabercats. However, comparison of craniomandibular morphology of the extant clouded leopard Neofelis nebulosa and Paramachairodus reveals numerous similarities and subsequent divergence from other extant great cats. In several key aspects, the clouded leopard has approached a primitive sabercat craniomandibular morphology and has diverged markedly from its sister group, the Panthera lineage. A primitive sabertooth condition arose six times in the Tertiary period, not five as is traditionally advocated. The clouded leopard appears to be a useful model for understanding primitive sabercat morphology and could shed important light on sabercat evolution. The unusual nature of the clouded leopard implies that increased efforts should be spent on insuring the continuing survival of this rare and endangered species.

3D Morphometric and Posture Study of Felid Scapulae Using Statistical Shape Modelling

Article

Full-text available

Apr 2012
PLOS ONE

We present a three dimensional (3D) morphometric modelling study of the scapulae of Felidae, with a focus on the correlations between forelimb postures and extracted scapular shape variations. Our shape modelling results indicate that the scapular infraspinous fossa becomes larger and relatively broader along the craniocaudal axis in larger felids. We infer that this enlargement of the scapular fossa may be a size-related specialization for postural support of the shoulder joint.

The Making of a Monster: Postnatal Ontogenetic Changes in Craniomandibular Shape in the Great Sabercat Smilodon

Article

Full-text available

Jan 2012
PLOS ONE

Per Christiansen

Derived sabercats had craniomandibular morphologies that in many respects were highly different from those of extant felids, and this has often been interpreted functionally as adaptations for predation at extreme gape angles with hypertrophied upper canines. It is unknown how much of this was a result of intraspecific postnatal ontogeny, since juveniles of sabercats are rare and no quantitative study has been made of craniomandibular ontogeny. Postnatal ontogenetic craniomandibular shape changes in two morphologically derived sabercats, Smilodon fatalis and S. populator, were analysed using geometric morphometrics and compared to three species of extant pantherines, the jaguar, tiger, and Sunda clouded leopard. Ontogenetic shape changes in Smilodon usually involved the same areas of the cranium and mandible as in extant pantherines, and large-scale modularization was similar, suggesting that such may have been the case for all felids, since it followed the same trends previously observed in other mammals. However, in other respects Smilodon differed from extant pantherines. Their crania underwent much greater and more localised ontogenetic shape changes than did the mandibles, whereas crania and mandibles of extant pantherines underwent smaller, fewer and less localised shape changes. Ontogenetic shape changes in the two species of Smilodon are largely similar, but differences are also present, notably those which may be tied to the presence of larger upper canines in S. populator. Several of the specialized cranial characters differentiating adult Smilodon from extant felids in a functional context, which are usually regarded as evolutionary adaptations for achieving high gape angles, are ontogenetic, and in several instances ontogeny appears to recapitulate phylogeny to some extent. No such ontogenetic evolutionary adaptive changes were found in the extant pantherines. Evolution in morphologically derived sabercats involved greater cranial ontogenetic changes than among extant felids, resulting in greatly modified adult craniomandibular morphologies.

Mathematical Analysis of Mandibular Morphogenesis by Micro-CT-Based Mouse and Alizarin Red S-Stained-Based Human Studies During Development

Article

Feb 2012
ANAT REC

Prenatal development of the mandible is an important factor in its postnatal function. To examine quantitatively normal and abnormal developmental changes of the mandible, we here evaluated morphological changes in mineralizing mandibles by thin-plate spline (TPS) including bending energy (BE) and Procrustes distance (PD), and by Procrustes analyses including warp analysis, regression analysis, and discriminant function analysis. BE and PD were calculated from lateral views of the mandibles of mice or of human fetuses using scanned micro-computed tomography (CT) images or alizarin red S-stained specimens, respectively. BE and PD were compared (1) between different developmental stages, and further, to detect abnormalities in the data sets and to evaluate the deviation from normal development in mouse fetuses, (2) at embryonic day (E) 18.5 between the normal and deformed mandibles, the latter being caused by suturing the jaw at E15.5, (3) at E15.5 and E18.5 between normal and knockout mutant mice of receptor tyrosine kinase-like orphan receptor (Ror) 2. In mice, BE and PD were large during the prenatal period and small after postnatal day 3, suggesting that the mandibular shape changes rapidly during the prenatal and early postnatal periods. In humans, BE of the mandibles peaked at 16-19 weeks of gestation, suggesting the time-dependent change in the mandibular shape. TPS and Procrustes analyses statistically separated the abnormal mandibles of the sutured or Ror2 mutant mouse fetuses from the normal mandible. These results suggest that TPS and Procrustes analyses are useful for assessing the morphogenesis and deformity of the mandible.

Skull evolution in the Rhinocerotidae (Mammalia, Perissodactyla): Cartesian transformations and functional interpretations

Article

Sep 1996

Gerald Bales

Cartesian transformation, applied as a landmark morphometric method, is used to investigate some of the evolutionary shape changes leading to the skulls of the modern rhinoceroses. The early Oligocene genusSubhyracodon serves as the primitive shape from which the extant genera (Dicerorhinus, Rhinocerso, Diceros, andCeratotherium) have been transformed. Coordinate data for 21 landmarks, defined in lateral view, are analyzed by the computer program Thinplate Splines. Each of the four transformations are interpreted separately as shape change fromSubhyracodon. Computed results forRhinoceros are also compared with previous results obtained by visual interpretation (the classic method). Among the extant genera,Ceratotherium andRhinoceros have the most derived shapes and are opposites with respect to orientation of the occiput and relative size of the mandible angle. The significance of these foci of change is discussed in terms of the functions of the masseter and posterior temporalis muscles. In head positions associated with feeding on short vs. tall grasses, the two skull shapes are consistent with a role for these muscles in support of a large mandible against gravity. This common factor may help to explain both shapes.

Geometric Morphometrics and Phylogeny

Article

Full-text available

Apr 1998

F. James Rohlf

This paper reviews some of the important properties of geometric morphometric shape variables and discusses the advantages and limitations of the use of such data in studies of phylogeny. A method for fitting morphometric data to a phylogeny (i.e., estimating ancestral states of the shape variables) is presented using the squared-change parsimony criterion for estimation. These results are then used to illustrate shape change along a phylogeny as a deformation of the shape of any other node on the tree (e.g., the estimated root of the tree). In addition, a method to estimate the digitized image of an ancestor is given that uses averages of unwarped images. An example dataset with 18 wing landmarks for 11 species of mosquitoes is used to illustrate the methods. [Keywords: squared-change parsimony, Procrustes, thin-plate spline, partial warps, mosquito wings, Culicidae] 2. Introduction The relatively new field of geometric morphometrics represents an important new paradigm for the ...

Craniofacial morphometric analysis of mandibular prognathism

Article

Apr 2006

The purpose of this study was to provide more information about the morphological characteristics of the craniofacial complex in mandibular prognathism. Forty young adult males having mandibular prognathism were compared with 40 having normal occlusion. This was conducted to carry out geometric morphometric assessments to localize alterations, using Procrustes analysis and thin-plate spline analysis, in addition to conventional cephalometric techniques. Procrustes analysis indicated that the mean craniofacial, midfacial and mandibular morphology was significantly different in prognathic subjects compared with normal controls. This finding was corroborated by the multivariate Hotelling T(2)-test of cephalometric variables. Mandibular prognathism demonstrated a shorter and slightly retropositioned maxilla, a greater total length and anterior positioning of the mandible. Thin-plate spline analysis revealed a developmental diminution of the palatomaxillary region anteroposteriorly and a developmental elongation of the mandible anteroposteriorly, leading to the appearance of a prognathic mandibular profile. In conclusion, thin-plate spline analysis seems to provide a valuable supplement for conventional cephalometric analysis because the complex patterns of craniofacial shape change are visualized suggestive by means of grid deformations.

PHYLOGENETIC ANALYSES OF THE CORRELATED EVOLUTION OF CONTINUOUS CHARACTERS: A SIMULATION STUDY

Article

Full-text available

May 1991
EVOLUTION

We use computer simulation to compare the statistical properties of several methods that have been proposed for estimating the evolutionary correlation between two continuous traits, and define alternative evolutionary correlations that may be of interest. We focus on Felsenstein's (1985) method and some variations of it and on several "minimum evolution" methods (of which the procedure of Huey and Bennett [1987] is a special case), as compared with a nonphylogenetic correlation. The last, a simple correlation of trait values across the tips of a phylogeny, virtually always yields inflated Type I error rates, relatively low power, and relatively poor estimates of evolutionary correlations. We therefore cannot recommend its use. In contrast, Felsenstein's (1985) method yields acceptable significance tests, high power, and good estimates of what we term the input correlation and the standardized realized evolutionary correlation, given complete phylogenetic information and knowledge of the rate and mode of character change (e.g., gradual and proportional to time ["Brownian motion"] or punctuational, with change only at speciation events). Inaccurate branch length information may affect any method adversely, but only rarely does it cause Felsenstein's (1985) method to perform worse than do the others tested. Other proposed methods generally yield inflated Type I error rates and have lower power. However, certain minimum evolution methods (although not the specific procedure used by Huey and Bennett [1987]) often provide more accurate estimates of what we term the unstandardized realized evolutionary correlation, and their use is recommended when estimation of this correlation is desired. We also demonstrate how correct Type I error rates can be obtained for any method by reference to an empirical null distribution derived from computer simulations, and provide practical suggestions on choosing an analytical method, based both on the evolutionary correlation of interest and on the availability of branch lengths and knowledge of the model of evolutionary change appropriate for the characters being analyzed. Computer programs that implement the various methods and that will simulate (correlated) character evolution along a known phylogeny are available from the authors on request. These programs can be used to test the effectiveness of any new methods that might be proposed, and to check the generality of our conclusions with regard to other phylogenies.

Group report: how are feeding systems integrated and how have evolutionary innovations been introduced?

Article

Full-text available

Jan 1989

Procrustes Methods in the Statistical Analysis of Shape

Article

Jan 1991

Colin R Goodall

Two geometrical figures, X and Y, in RK, each consisting of N landmark points, have the same shape if they differ by at most a rotation, a translation and isotropic scaling. This paper presents a model‐based Procrustes approach to analysing sets of shapes. With few exceptions, the metric geometry of shape spaces is quite complicated. We develop a basic understanding through the familiar QR and singular value decompositions of multivariate analysis. The strategy underlying the use of Procrustes methods is to work directly with the N x K co‐ordinate matrix, while allowing for an arbitrary similarity transformation at all stages of model formulation, estimation and inference. A Gaussian model for landmark data is defined for a single population and generalized to two‐sample, analysis‐of‐variance and regression models. Maximum likelihood estimation is by least squares superimposition of the figures; we describe generalizations of Procrustes techniques to allow non‐isotropic errors at and between landmarks. Inference is based on an N x K linear multivariate Procrustes statistic that, in a double‐rotated co‐ordinate system, is a simple but singular linear transformation of the errors at landmarks. However, the superimposition metric used for fitting, and the model metric, or covariance, used for testing, may not coincide. Estimates of means are consistent for many reasonable choices of superimposition metric. The estimates are efficient (maximum likelihood estimates) when the metrics coincide. F‐ratio and Hotelling's R2‐tests for shape differences in one‐ and two‐sample data are derived from the distribution of the Procrustes statistic. The techniques are applied to the shapes associated with hydrocephaly and nutritional differences in young rats.

Morphometrics in Evolutionary Biology

Article

Dec 1988
COPEIA

PHENOTYPIC, GENETIC, AND ENVIRONMENTAL MORPHOLOGICAL INTEGRATION IN THE CRANIUM

Article

May 1982
EVOLUTION

James Cheverud

A METHOD FOR TESTING THE CORRELATED EVOLUTION OF TWO BINARY CHARACTERS: ARE GAINS OR LOSSES CONCENTRATED ON CERTAIN BRANCHES OF A PHYLOGENETIC TREE?

Article

May 1990
EVOLUTION

Wayne P Maddison

A method is presented for assessing whether changes in a binary character are more concentrated than expected by chance on certain branches of a phylogenetic tree. It can be used to test for correlated evolution of two characters by asking whether changes in the first character are significantly concentrated on those branches on which the second character has a specified state. Thus, one could test whether this specified state is associated with, and thus might enable or select, gains or losses in the first character. The probability of achieving a concentration as or more extreme than that observed under the null hypotheses that changes are distributed randomly on the cladogram is obtained by calculating (a) the number of ways that n gains and m losses can be distributed on the cladogram and (b) the number of ways that p gains q losses can be distributed on the branches of interest given n gains and m losses in the cladogram overall. Summing (b) for appropriate p and q then dividing by (a) yields the desired probability. Simulations suggest that biases resulting from errors in parsimony reconstructions of ancestral states are not extreme.

EVOLUTION, PHYLOGENY, SEXUAL DIMORPHISM AND MATING SYSTEM IN THE GRACKLES (QUISCALUS SPP.: ICTERINAE)

Article

May 1991
EVOLUTION

Mats Björklund

According to theory, two consequences of sexual selection are sexual dimorphism in size and secondary sexual characteristics, due to either intra- or intersexual selection. In this paper I suggest three criteria for the test of an evolutionary hypothesis involving quantitative morphological characters. First, the postulated change must be shown to have occurred in evolutionary time. Second, this change must be positively correlated with a change in the proposed selective agent. Third, given two taxa with different degrees of sexual size dimorphism and different mating system, the possible influence of drift must be rejected. If the hypothesis is not rejected by these three criteria, then we still have no proof of causality, but we can at least be more confident about its plausibility. This is applied to the particular hypothesis that sexual dimorphism in the Boat-tailed and Great-tailed grackles (Quiscalus spp; Icterinae; Aves) is caused by the highly polygynous mating system in these species. In relation to an outgroup, both species have increased disproportionately in male tarsus and tail size, creating an increased sexual dimorphism. This has cooccurred with the evolution of their particular mating system. However, the variance among species in male tarsus size can be accounted for by drift, and need not be a result of selection for increased size. In contrast, the variance among species in male tail size was much larger than expected under a null model of drift, indicating directional selection for long tails. The variance in female tail size was not larger than expected by drift, whereas the variance in female tarsus size was in fact lower than expected by drift, indicating stabilizing selection. The data are consistent with the hypothesis with regard to tail size, but not with regard to body size.

ONTOGENETIC VARIATION IN PATTERNS OF DEVELOPMENTAL AND FUNCTIONAL INTEGRATION IN SKULLS OF SIGMODON FULVIVENTER

Article

Jul 1989
EVOLUTION

Patterns of variation and covariation within populations can influence how characters respond to natural selection and random genetic drift and so constrain the ability of natural selection to modify the phenotype. We examined several potential developmental and functional explanations of character covariation throughout ontogeny using known-age samples of the cotton rat (Sigmodon fulviventer) to identify the causes of covariation and to assess the variability of patterns of covariation throughout postnatal growth. Competing developmental and functional models were fit to samples of orofacial and neurocranial measures by confirmatory factor analysis and evaluated for their ability to reconstruct observed variance-covariance matrices. Samples of successive ages were simultaneously fit to a common model to test the hypothesis that the patterns of developmental and functional integration were invariant between ages. Orofacial characters derived from the same branchial-arch primordium covary early in ontogeny. Subsequently, there is a repatterning of integration that may reflect a transition from developmental to functional sources of integration. Neurocranial characters exhibit even more variation in patterns of covariation: initially, characters appear to comprise a single integrated unit; before puberty, they appear to respond to localized bone growth; after puberty, they form separate calvarial and basicranial components. This ontogenetic variation in patterns of covariation suggests that developmental constraints are transient and flexible and that the consequences of selection may depend upon the age at which it acts.

Ontogeny Of Integrated Skull Growth In The Cotton Rat Sigmodon Fulviventer

Article

Aug 1992
EVOLUTION

Because development is epigenetic, diverse aspects of morphology are integrated during ontogeny. Using the method of thin-plate splines, and the decomposition of these splines by their principal warps, we examine the ontogeny of integrated features of skull growth of the cotton rat, Sigmodon fulviventer as observed in landmark locations in the ventral view. Postnatal growth of the skull in Sigmodon is not adequately described by the familiar contrast between relatively rapid facial elongation and slow, precocial growth of the cranial base. No developmental units corresponding to "facial skull" and "cranial base" emerge from analysis of geometric shape change. Rather, skull growth is both more integrated and more complex, exhibiting both skull-wide integration and locally individualized regions. Like skull shape, integration has an ontogeny; different regions of the skull can be partitioned into developmentally individualized parts in different ways at different ages. The effective count of individualized parts decreases substantially before weaning occurs, suggesting that the integration required by the functionally demanding activity of chewing gradually develops before the functional transition occurs. Our description of skull growth and integration does not depend upon arbitrary a priori choices about what to measure; rather, we base our decomposition of the whole into parts upon results of the data analysis. Our approach complicates the study of heterochrony, but, because it expresses the spatiotemporal organization of ontogeny, it enables the study of heterotopy.

The Structure Of Individual Variation In Miocene Globorotalia

Article

Mar 1990
EVOLUTION

Analysis of probability distributions of individual organisms provides a common language to describe synchronic and diachronic diversity. When based on an appropriate quantitative description of morphology, this language can be used to explore the temporal component of diversity embedded in the fossil record. Miocene Globorotalia (planktonic foraminifera) from Deep Sea Drilling Project site 593 are described using two-point registration of landmarks in two views (spiral and apertural) and medial-axis analysis of the shape of the final chamber. The equiangular spiral parameters Θ (the angle of increment), r (the expansion rate), and t (the rate of translation down the spiral axis) appear as principal components of the landmark data. Chamber shape variation is described by three principal components of medial-axis curvature. Partial-least-squares analysis demonstrates that the first components of within-morphospace variation also explain the patterns of correlation between the landmark and chamber-shape morphospaces. In the landmark morphospaces, the distribution of sampled individuals is continuous and roughly elliptical with few stratigraphic changes. In the chamber-shape morphospace, the distribution is continuous but shows complex features beyond the elliptical; the occupied morphospace changes stratigraphically, but neither strict cladogenesis nor strict anagenesis explains the derivation of new morphologies. Exemplars of named morphospecies are scattered across these spaces with continuous variation among all forms. These names cannot be assumed to represent discrete entities.

PHYLOGENIES AND THE ANALYSIS OF EVOLUTIONARY SEQUENCES, WITH EXAMPLES FROM SEED PLANTS

Article

Sep 1989
EVOLUTION

Michael J. Donoghue

Studies of character evolution have frequently relied on ahistorical correlations rather than on phylogenies. However, correlations do not estimate the number of times that a trait evolved, and they are insensitive to the direction or the temporal sequence of character transformation. In contrast, cladograms can provide this information. A cladistic test of the hypothesis that the evolution of dioecy is favored in animal-dispersed plants indicates that dioecy may have originated somewhat more often in such lineages. Nevertheless, differences in rates of speciation or extinction must largely account for the observed species-level correlation between dispersal and breeding system. In considering the evolution of individual traits, cladograms help identify the context in which a feature evolved and specify which organisms should be compared in evaluating the causes of character change. Determining whether a feature and a performance advantage were strictly historically correlated or followed one another in sequence helps to distinguish whether the trait is an adaptation or an exaptation for the function. For example, cladograms of seed plants suggest that double fertilization arose incidentally prior to the origin of angiosperms and that the resulting product was later co-opted and elaborated as a nutritive tissue for the developing embryo. The order of character assembly in a lineage also bears on the evolution of functional and developmental interdependencies. In particular, it may be possible to trace the evolution of a character's "burden" from an initial period, during which change is more likely, through later stages, wherein successful modification is less likely owing to the evolution of dependent characters. The evolution of vessels and of floral phyllotaxis in angiosperms may exemplify this pattern. Recognition that the likelihood of character transformation may change during the evolution of a group warns against character weighting in phylogenetic analysis.

SOME MODELS FOR DEVELOPMENT, GROWTH, AND MORPHOMETRIC CORRELATION

Article

Nov 1986
EVOLUTION

Bruce Riska

Genetic and phenotypic correlations between morphometric traits can be a direct consequence of shared developmental history and common systems of growth regulation. Correlation between traits, therefore, need not imply direct functional or adaptive constraints on those traits. Useful models of the developmental origins of correlations will consider mechanisms that can reduce initially high correlation of traits that arise from a single developmental precursor. Several models presented here predict such correlations for different modes of fission of a precursor. Timing of developmental events may also affect correlations and respond to selection on adult traits. The models may apply to development of the tetrapod limb bud, including variance and covariance induced by known developmental mutants.

LEVELS OF INTEGRATION IN MAMMALIAN DENTITIONS: AN ANALYSIS OF CORRELATIONS IN NESOPHONTES MICRUS (INSECTIVORA) AND ORYZOMYS COUESI (RODENTIA)

Article

Jun 1969
EVOLUTION

Chromosomes of Spermophilus franklini and Taxonomy of the Ground Squirrel Genus Spermophilus

Article

Sep 1966

C. F. Nadler

Immunological Comparisons of Four Subgenera of Ground Squirrels

Article

Dec 1968

The primary role of functional matrices in facial growth

Article

Jan 1989

M.L. Moss

The functional matrix

Article

Jan 1969
Am J Orthod

Phenotypic, genetic, and environmental integration in the cranium

Article

Jan 1982
EVOLUTION

James Cheverud

Principal warps: Thin-plate splines and the decomposition of deformations

Article

Jan 1992

Fred L. Bookstein

The decomposition of deformations by principal warps is demonstrated. The method is extended to deal with curving edges between landmarks. This formulation is related to other applications of splines current in computer vision. How they might aid in the extraction of features for analysis, comparison, and diagnosis of biological and medical images is indicated.

Relationships among the living squirrels of the Sciurinae

Article

Jan 1959

J.C. Moore

Size and position of the functional components of the skull

Article

Jan 1952

C.J. Van Der Klaauw

Statistical Methods, ed 7. Ames

Article

Jan 1980

Phylogeny of Nearctic Sciuridae

Article

Jan 1945

M.D. Bryant

Testing for historical patterns of change: a case study with frog pectoral girdles

Article

Jan 1988

Sharon B Emerson

This study tests the decoupling hypothesis, which predicts an increase in the number of morphological constraints with a reduction in the number of independent elements. Eight cases of historical transformation of the epicoracoid cartilages of frogs were selected for analysis. Similar morphological shape changes occurred across the independently derived historical transformations as determined by a triangle analysis of shape. These results support the decoupling hypothesis and indicate that there may be generalized historical pathways of structural change. This finding is important for the development of a predictive theory in evolutionary morphology.-from Author

The Tree Squirrel Sciurus (Sciuridae, Rodentia) as a Living Fossil

Chapter

Jan 1984

The familiar living squirrel, Sciurus, is not among the classic and often-cited examples of living fossils, although squirrels have long been recognized as being among the most primitive members of the Rodentia, the mammalian order that has exceeded all others in specific diversity. In the sense that they represent the least derived family of a very diverse order, squirrels in general might be called living fossils. The recently discovered skeleton of Protosciurus (perhaps the oldest squirrel fossil) shows that the earliest recognized sciurid is strikingly similar in its osteology to living Sciurus. In the sense that it has evolved very little from what is apparently the primitive squirrel morphotype, Sciurus is a living fossil.

Statistical Methods

Article

Sep 1991

Tree Nests of Chipmunks with Comments on Associated Behavior and Ecology

Article

Aug 1974

Harold E. Broadbooks

Four additional species of Eutamias (amoenus, cinereicollis, palmeri, and ruficaudus), added to E. minimus, speciosus, and sibericus, bring to seven the number of tree-nesting chipmunks. Tree nests were at heights of 2.6 to 23 meters. Those made of grass by E. amoenus and ruficaudus were about 30 centimeters in diameter and were used for more than one year. Most tree nests were in conifers (three in woodpecker holes), one was in a clump of young willows, and one was in a cottonwood. It is during the period of weaning and exploration just before the young disperse that tree nests are used by a mother and her family. Chipmunks appear to be the only sciurids and possibly the only rodents in which the mother and her family use both underground and arboreal nests in a given year. Feeding in the pygmy forest of bushes, chipmunks occupy a special niche between those of ground squirrels and tree squirrels.

Morphometric Tools for Landmark Data: Geometry and Biology.

Article

Dec 1992

Problems of Relative Growth

Article

Sep 1994

Albumin Evolution within New World Squirrels (Sciuridae)

Article

Jul 1980

Immunological studies of the Sciuridae using quantitative microcomplement fixation indicate that the ground squirrel and chipmunk lineages diverged from tree squirrels during the early Oligocene. Chipmunks and ground squirrels diverged during the early Miocene. Radiation within the ground squirrel lineage appears to have taken place during the early and middle Miocene. These findings are, for the most part, consistent with fossil, karyotypic and other biochemical data.

The Structure of Individual Variation in Miocene Globorotalia

Article

Mar 1990

Analysis of probability distributions of individual organisms provides a common language to describe synchronic and diachronic diversity. When based on an appropriate quantitative description of morphology, this language can be used to explore the temporal component of diversity embedded in the fossil record. Miocene Globorotalia (planktonic foraminifera) from Deep Sea Drilling Project site 593 are described using two-point registration of landmarks in two views (spiral and apertural) and medialaxis analysis of the shape of the final chamber. The equiangular spiral parameters Θ (the angle of increment), r (the expansion rate), and t (the rate of translation down the spiral axis) appear as principal components of the landmark data. Chamber shape variation is described by three principal components of medial-axis curvature. Partial-least-squares analysis demonstrates that the first components of within-morphospace variation also explain the patterns of correlation between the landmark and chamber-shape morphospaces. In the landmark morphospaces, the distribution of sampled individuals is continuous and roughly elliptical with few stratigraphic changes. In the chamber-shape morphospace, the distribution is continuous but shows complex features beyond the elliptical; the occupied morphospace changes stratigraphically, but neither strict cladogenesis nor strict anagenesis explains the derivation of new morphologies. Exemplars of named morphospecies are scattered across these spaces with continuous variation among all forms. These names cannot be assumed to represent discrete entities.

Morphology and Evolution of the Wrists of Burrowing and Nonburrowing Shrews (Soricidae)

Article

Feb 1991

Donald L Swiderski

Forelimb burrowers are expected to have traits in the wrist that restrict freedom of movement relative to nonburrowers, preventing deflection of the hand by obstructions and reducing the energetic cost of digging. Wrist skeleton and ligaments were compared among representatives from several lineages of shrews. Only two traits differ between burrowers and nonburrowers; neither affects wrist function. In addition, all shrews have several traits expected to be present only in burrowers, indicating that wrist evolution was conservative and that the shared traits may have been inherited from a burrowing ancestor. The few wrist traits that differ indicate that functional interactions between anatomical elements may play a role in determining patterns of morphological evolution.

System Atics of the Holarctic Chipmunks (Tamias)

Article

May 1985

Electrophoretic data for 20 proteins were obtained from 17 species of chipmunks, including all three presently recognized subgenera. Average heterozygosity was higher than for ground squirrels (Spermophilus) but was generally within the range reported for other rodents; Tamias minimus, however, had a higher heterozygosity value than almost any other rodent species. Cladistic analyses of the electrophoretic data resulted in species groupings which differed from traditional analyses of morphological data. The species T. Sibiricus and T. striatus were grouped together, separate from all other chipmunks, thereby contradicting traditional supra-specific classifications. We recognize one genus (Tamias) with two subgenera, Tamias (composed of Sibiricus and striatus) and Neotamias with five species groups. A hypothesis concerning dispersal in the ancestral chipmunk lineage was formulated and a phylogram constructed on the basis of cladistic and biogeographic analyses. Multivariate analyses then were conducted on cranial and body measurements of 53 taxa of chipmunks, representing all recognized species and subgenera. Variation among individual taxa was detected in both general size and cranial shape. Phenetic morphological relationships among the chipmunks were ascertained by cluster analysis. The proposed phylogenetic groupings were compared with the morphological groupings in an assessment of divergent and convergent evolution within the genus.

Some Models for Development, Growth, and Morphometric Correlation

Article

Nov 1986

Bruce Riska

A Method for Testing the Correlated Evolution of Two Binary Characters: Are Gains or Losses Concentrated on Certain Branches of a Phylogenetic Tree?

Article

May 1990

Wayne Maddison

Evolution, Phylogeny, Sexual Dimorphism and Mating System in the Grackles (Quiscalus spp.: Icterinae)

Article

May 1991
EVOLUTION

Mats Björklund

According to theory, two consequences of sexual selection are sexual dimorphism in size and secondary sexual characteristics, due to either intra- or intersexual selection. In this paper I suggest three criteria for the test of an evolutionary hypothesis involving quantitative morphological characters. First, the postulated change must be shown to have occurred in evolutionary time. Second, this change must be positively correlated with a change in the proposed selective agent. Third, given two taxa with different degrees of sexual size dimorphism and different mating system, the possible influence of drift must be rejected. If the hypothesis is not rejected by these three criteria, then we still have no proof of causality, but we can at least be more confident about its plausibility. This is applied to the particular hypothesis that sexual dimorphism in the Boat-tailed and Great-tailed grackles (Quiscalus spp.; Icterinae; Aves) is caused by the highly polygynous mating system in these species. In relation to an outgroup, both species have increased disproportionately in male tarsus and tail size, creating an increased sexual dimorphism. This has cooccurred with the evolution of their particular mating system. However, the variance among species in male tarsus size can be accounted for by drift, and need not be a result of selection for increased size. In contrast, the variance among species in male tail size was much larger than expected under a null model of drift, indicating directional selection for long tails. The variance in female tail size was not larger than expected by drift, whereas the variance in female tarsus size was in fact lower than expected by drift, indicating stabilizing selection. The data are consistent with the hypothesis with regard to tail size, but not with regard to body size.

Procrustes Methods in the Statistical Analysis of Shape

Article

Jan 1991

Colin R Goodall

Two geometrical figures, X and Y, in R^K, each consisting of N landmark points, have the same shape if they differ by at most a rotation, a translation and isotropic scaling. This paper presents a model-based Procrustes approach to analysing sets of shapes. With few exceptions, the metric geometry of shape spaces is quite complicated. We develop a basic understanding through the familiar QR and singular value decompositions of multivariate analysis. The strategy underlying the use of Procrustes methods is to work directly with the N × K co-ordinate matrix, while allowing for an arbitrary similarity transformation at all stages of model formulation, estimation and inference. A Gaussian model for landmark data is defined for a single population and generalized to two-sample, analysis-of-variance and regression models. Maximum likelihood estimation is by least squares superimposition of the figures; we describe generalizations of Procrustes techniques to allow non-isotropic errors at and between landmarks. Inference is based on an N × K linear multivariate Procrustes statistic that, in a double-rotated co-ordinate system, is a simple but singular linear transformation of the errors at landmarks. However, the superimposition metric used for fitting, and the model metric, or covariance, used for testing, may not coincide. Estimates of means are consistent for many reasonable choices of superimposition metric. The estimates are efficient (maximum likelihood estimates) when the metrics coincide. F-ratio and Hotelling's T²-tests for shape differences in one- and two-sample data are derived from the distribution of the Procrustes statistic. The techniques are applied to the shapes associated with hydrocephaly and nutritional differences in young rats.

Phylogenetic Analyses of the Correlated Evolution of Continuous Characters: A Simulation Study

Article

May 1991

Form and function: Structural analysis in evolutionary morphology

Article

Sep 1981

George V. Lauder

A theoretical approach to the analysis of historical factors (Raup 1972) in evolutionary morphology is presented which addresses transformational hypotheses about structural systems. This (structural) approach to testing historical hypotheses about phylogenetic constraints on form and function and structural and functional versatility involves (1) the reconstruction of nested sets of structural features in monophyletic taxa, (2) the use of general or emergent organizational properties of structural and functional systems (as opposed to uniquely derived morphological features), and (3) the comparative examination of the consequences for structural and functional diversity of these general features in related monophyletic taxa. Three examples of emergent organizational properties are considered: structural complexity, repetition of parts, and the decoupling of primitively constrained systems. Two classes of hypotheses about the evolution of design are proposed. Transformational hypotheses concern historical pathways of change in form as a consequence of general organizational features which are primitive for a lineage. Relational hypotheses involve correlations between structure-function networks primitive for a clade and morphological diversity both between and within terminal taxa. To the extent that transformational and relational hypotheses about form are corroborated, they provide evidence of underlying regularity in the transformation of organic design that may be a consequence of the hierarchical organization of structural and functional patterns in organisms.

Mammals of the Northern Great Plains

Article

Oct 1984

For the purposes of this book, the Northern Great Plains are defined as the states of Nebraska, North Dakota, and South Dakota. As a physiographic concept, the northern part of the great interior grasslands of North America is, of course, much broader in geographic extent than the Dakotas and Nebraska, but the three states lie in the heart of the region, and thus the title for this work seems appropriate. Our expectations in writing Mammals of the Northern Great Plains were to provide a comprehensive, yet semitechnical, treatmeat of free-living mammals that would prove useful to specialist and nonspecialist alike. The content and style therefore were developed in a way we hope will interest the inquiring high-school student, on the one hand, and provide a point of reference for the professional mammalogist on the other. Between these extremes, wildlife biologists, conservationists, environmental specialists, college students of vertebrate zoology, and others interested in mammalian natural history should find the present treatment useful for their needs as well. In the accounts that follow, species of each genus are listed in alphabetical order. Genera, families, and orders are arranged in conventional phylogenetic sequence, and treatment of these higher taxa is deliberately brief. Readers desiring more detail should consult the synopsis by Anderson and Jones (1967) for orders and families and that of Walker et al. (1964 and subsequent editions) for genera. Both scientific and vernacular names of species generally follow Jones, Carter, and Genoways (1979). Information in the accounts of species is organized under five headings: Name, Distribution, Description, Natural History, and Selected References. In the first section, comment is made on the derivation of the scientific name of the species; often, alternative vernacular names are provided. The section on distribution describes the general geographic and ecological range of a species. Subspecies (if recognized) are listed in this section. The geographic ranges of most species are mapped, based on the currently known distribution; the maps, however, are deliberately conservative, and additional fieldwork in various parts of the region certainly will extend the known limits of many mammals. In several cases where too few specimens of a species have been reported to allow the distribution in the tristate region to be shaded with confidence, only the actual localities of record are indicated.

The Recent Mammals of the Neotropical Region: A Zoogeographic and Ecological Review

Article

Mar 1969

Philip Hershkovitz

The Neotropical Region, which is defined on the basis of its living mammals, is comprised of the Brazilian, Patagonian, and West Indian Subregions. The Middle American Province of the Brazilian Subregion was the primary center of origin, evolution, and dispersal for mammals now living in continental South America. The West Indies also derived its fauna from Middle America, and perhaps also from South America. Faunal interchange between these regions must have taken place since the Middle Tertiary, at the latest. By the time the Isthmian land bridge between Middle and South America was completed during the Pliocene-Pleistocene transition, nearly all modern genera of Neotropical mammals were already differentiated within their present geographic ranges. Five faunal strata of Neotropical mammals are identified on the basis of postulated centers of origin of the ancestral stock, dispersal routes of colonizers, known grades of differentiation of living descendents, and the meager fossil evidence. The living fa...

On Growth and Form Abridged

Book

Jan 1992

D'Arcy W Thompson

Size and Position of the Functional Components of the Skull. a Contribution To the Knowledge of the Architecture of the Skull, Based On Data in the Literature

Article

Jan 1952

C. J. Van Der Klaauw

Ontogenetic Variation in Patterns of Developmental and Functional Integration in Skulls of Sigmodon fulviventer

Article

Jul 1989

Comparative limb myology of two opossums, Didelphis and Chironectes

Article

Jul 1981
J MORPHOL

Barbara R. Stein

A comparative study of limb morphology indicates that the osteological and myological differences between Didelphis virginiana, the Virginia opossum, and Chironectes minimus, the water opossum, may be associated in Chironectes with decreased resistance to water and increased mechanical advantage of its muscles for increased force. Limb myology is described and a synonymy of terms is applied to the musculature of these two opossums.

The forelimb architecture of some fossorial rodents

Article

Jul 1963
J MORPHOL

Wilma H. Lehmann

Thesis (Ph. D.)--University of Illinois, 1961. Includes bibliographical references (leaves 64-69). Vita.

Morphometric integration in the rat (Rattus sp.) scapula

Article

Aug 2009
J ZOOL

Morphometric integration was analysed in 19 anatomical measures taken on the scapula and humerus in a population of 519 rats. As hypothesized, genetic integration was the highest, the average phenotypic genetic, and environmental correlations being 0·53, 0·67 and 0·42, and the index of integration 0·56, 0·69 and 0·48. Phenotypic and genetic correlation matrices were most similar (correlation =+0.79), genetic and environmental matrices least similar (correlation =+0.49). The first unrotated vector produced from principal components analysis explained a high percentage of the total variation (from 50% in the environmental to 70% in the genetic solution), and was highly heritable in all cases. Rotated vectors defined two length, one width, and one height grouping in the phenotypic solution, these being explained largely in terms of muscle assemblages. The four vectors produced in the genetic solution were similar to those from the phenotypic ones, but were more functionally interpretable. The five vectors produced from the environmental correlations paralleled those from the phenotypic correlations with regard to the length, but not the width measures. The general concordance among appropriate vectors from all three solutions was reasonably high. Twelve of the 13 vectors, as well as several hypothetical ones. exhibited moderate to high heritabilities.

The architecture of the shoulder in some mammals

Article

Nov 1968
J MORPHOL

Charles Ernest Oxnard

A series of nine features of the shoulder girdle, chosen as having functional significance in relation to the movements of the shoulder in arboreal locomotion, have been studied in 1188 specimens of 194 genera of mammals. The features were defined metrically and examined by means of a multivariate statistical technique: viz. canonical analysis. The study has shown that those mammals which are nonarboreal differ considerably among themselves and form the arboreal forms. But the myriad shapes of the shoulder girdle in a wide range of mammals (e.g. some marsupials, edentates, rodents, carnivores and primates) which climb or forage in trees, can be summarized mathematically by a very small number of similar canonical variates. This information correlates well with that of a previous series of studies carried out on the primates alone. The biological information that was postulated as being reflected by the individual canonical variates for the primates is also apparent for the arboreal mammals. The different variates separate the forms in ways which are consonant with what is known about the function of the shoulder in locomotion. Aspects of the shape of the shoulder defined by the analysis appear to be discernible from an examination of the contribution of the original variables to each individual canonical variate. This seems to confirm that the shape of the shoulder girdle within a very wide range of mammals is limited by a very small number of underlying factors of biological significance. One interpretation of the results suggests that the genetic model of the mammalian shoulder may have been sufficiently fixed at an early stage in the evolution of the class as to place considerable constraints upon the subsequent evolution of the shoulder in the different Orders.

Functional morphology of the “tongue-bite” in the Osteoglossomorph fish Notopterus

Article

Oct 1989
J MORPHOL

Osteoglossomorph fishes are characterized by having three sets of jaws: a mandibular jaw apparatus (MJA) anteriorly, a pharyngeal jaw apparatus (PJA) posteriorly, and a tongue-bite apparatus (TBA) associated with basihyal and parasphenoid teeth. The TBA is a novel complex feature of the head that characterizes osteoglossomorph fishes and provides a case study in the origin of novel functions and roles in the vertebrate musculoskeletal system. The function of the tongue-bite in the osteoglossomorph fish Notopterus was characterized by using high-speed cinematography and electromyography. The tongue-bite is used during intraoral prey processing to shred and disable prey. Two distinct uses of the TBA were defined on the basis of kinematic and electromyographic profiles: raking and open-mouth chewing. During raking behavior, the prey is held fixed in the MJA, the neurocranium is elevated, and the pectoral girdle is retracted. The adductor mandibulae, hypaxialis, epaxialis, and posterior intermandibularis muscles are all highly active, but only very low activity is observed in the sternohyoideus muscle. During open-mouth chewing behavior, the prey is located within the oral cavity, posterior pectoral girdle rotation is less than during raking, and the levator operculi muscle shows relatively high activity. We propose that a shearing action of the basihyal (moved anteroposteriorly by the posterior intermandibularis and hypaxial muscles) with respect to the neurocranium (elevated by epaxial muscles) is the critical aspect of the tongue-bite in Notopterus. The body muscles (epaxials and hypaxials) provide the main power for the tongue-bite. We hypothesize that lack of sternohyoideus activity during intraoral prey processing, posterior pectoral girdle rotation, and a long-fibered posterior intermandibularis muscle are novel structures associated with the tongue-bite apparatus within osteoglossomorph fishes.

Phylogenies and the Analysis of Evolutionary Sequences, with Examples From Seed Plants

Article

Sep 1989

Michael J. Donoghue

Correlations do not estimate the number of times that a trait evolved, and they are insensitive to the direction or the temporal sequence of character transformation. In contrast, cladograms can provide this information. A cladistic test of the hypothesis that the evolution of dioecy is favored in animal-dispersed plants indicates that dioecy may have originated somewhat more often in such lineages. Nevertheless, differences in rates of speciation or extinction must largely account for the observed species-level correlation between dispersal and breeding system. Determining whether a feature and a performance advantage were strictly historically correlated or followed one another in sequence helps to distinguish whether the trait is an adaptation or an exaptation for the function. Cladograms of seed plants suggest that double fertilization arose incidentally prior to the origin of angiosperms and that the resulting product was later co-opted and elaborated as a nutritive tissue for the developing embryo. The order of character assembly in a lineage also bears on the evolution of functional and developmental interdependencies. In particular, it may be possible to trace the evolution of a character's "burden' from an initial period, during which change is more likely, through later stages, wherein successful modification is less likely owing to the evolution of dependent characters. The evolution of vessels and of floral phyllotaxis in angiosperms may exemplify this pattern. -from Author

Morphological Evolution Of The Scapula In Tree Squirrels, Chipmunks, And Ground Squirrels (Sciuridae): An Analysis Using Thin‐Plate Splines

Abstract

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