Postcranial Traits Research Articles

A new old Budgett frog: an articulated skeleton of an Early Pliocene Lepidobatrachus (Anura, Ceratophryidae) from western Argentina

ABSTRACT The South American horned frogs or ‘escuerzos’ (Ceratophryidae) are among the best-known neobatrachians and comprise the genera Chacophrys, Ceratophrys, and Lepidobatrachus. Their relatively rich fossil record, which dates back to the Late Miocene and is largely concentrated in the Argentinean Pampas, consists mostly of variably complete cranial remains and comparatively few, mainly isolated, postcranial bones of Ceratophrys, whereas only three specimens of Lepidobatrachus are known. Here we describe two extra-Pampean ceratophryid records from the Upper Miocene–Lower Pliocene of Huayquerías del Este, Mendoza Province, Argentina, including Lepidobatrachus dibumartinez sp. nov. based on a well-preserved articulated skeleton. The new species is part of the stem of Lepidobatrachus and is diagnosed on the basis of several cranial and postcranial traits, including a large kite-shaped dorsal dermal shield. The new taxon sheds light on the evolution of a dorsal shield in the group, as well as on their paleobiogeographic history, adding support to the hypothesis of a broader ancestral distribution of Lepidobatrachus, whose diversification might have been triggered by the Late Miocene marine introgression of the Paranaense Sea. Also, it indicates that the prevalent climatic conditions during the Early Pliocene in western Argentina were much warmer and less dry than today. Finally, we discuss the potential value of the new records in calibrating the time-tree of Ceratophryidae. http://zoobank.org/urn:lsid:zoobank.org:pub:2DFB3B68-8C30-4252-A3DC-BF1F69F5AB6A

The influence of climate and population structure on East Asian skeletal morphology

Recent studies have shown that global variation in body proportions is more complex than previously thought as some traits formerly associated with climate adaptation are better explained by geographic proximity and neutral evolutionary forces. While the recent incorporation of quantitative genetic methodologies has improved understanding of patterns related to climate in Africa, Europe, and the Americas, Asia remains underrepresented in recent and historic studies of body form. As ecogeographic studies tend to focus on male morphology, potential sex differences in features influenced by climate remain largely unexplored. Skeletal measurements encompassing the dimensions of the skull, pelvis, limbs, hands, and feet were collected from male (n = 459) and female (n = 442) remains curated in 13 collections across seven countries in East Asia (n = 901). Osteological data were analyzed with sex and minimum temperature as covariates adjusted by autosomal single-nucleotide polymorphism population genetic distance using univariate Bayesian linear mixed models, and credible intervals were calculated for each trait. Analysis supports a relationship between specific traits and climate as well as providing the magnitude of response in both sexes. After accounting for genetic distance between populations, greater association between climate and morphology was found in postcranial traits, with the relationship between climate and the skull limited primarily to breadth measurements. Larger body size is associated with colder climates with most measurements increasing with decreased temperature. The same traits were not always associated with climate for males and females nor correlated with the same intensity for both sexes. The varied directional association with climate for different regions of the skeleton and between the sexes underscores the necessity of future ecogeographic research to holistically evaluate body form and to look for sex-specific patterns to better understand population responses to environmental stresses.

Evolvability in human postcranial traits across ecogeographic regions.

Though recent quantitative genetic analyses have indicated that directional selection appears to be acting on limb lengths and measures of body size in modern humans, these studies assume equal evolvability across modern human groups. However, differences in trait covariance structure due to ancient migration patterns and/or selection may limit the evolvability of populations further from Africa. This study therefore explores patterns of human evolvability across ecogeographic regions. Mean evolvability, respondability, conditional evolvability, and autonomy were calculated from variance-covariance matrices of limb length and body size measures representing 14 human groups spanning four ecogeographic regions. Measures of evolvability were compared across groups and regions, and the minimum sample size, inaccuracy, and bias were calculated for each. When compared between regions, humans demonstrate significant differences between indices of evolvability across regions. Despite the relatively recent evolution of modern humans, several measures of evolvability show a strong negative correlation with latitude across regions, demonstrating a reduction in genetic variance that is potentially reflective of human migration and/or response to selection. These results demonstrate the importance of establishing patterns of evolvability prior to additional quantitative genetic analyses, and emphasize the influence of sample size on the accuracy of estimated evolvability measures. These findings also suggest that while modern human groups share similar covariance structures, there is evidence for emergent differentiation in evolvability and respondability between human groups across ecogeographic regions, further complicating our ability to apply results derived from modern human groups to ancient hominin lineages.

Ancestry Estimation Using Cranial and Postcranial Macromorphoscopic Traits.

Ancestry estimation methods using macromorphoscopic (MMS) traits commonly focus exclusively on cranial morphology. The objective of this study was to demonstrate the value of postcranial MMS traits, highlighting a combined cranial/postcranial trait approach to ancestry estimation using quadratic discriminant function and a variety of machine learning classification models including artificial neural networks (aNN), random forest models, and support vector machine. Eight cranial and eleven postcranial MMS traits were collected from the Terry and Bass Skeletal Collections (American Black=81; American White=173). Our classification models using cranial and postcranial traits correctly classified 88-92% of the sample, improving classification accuracies by nearly fifteen percent over models relying exclusively on cranial data. These same results demonstrate the importance of a multivariate statistical framework incorporating cranial and postcranial data and the nearly unlimited potential of machine learning models to improve the accuracy of ancestry estimates over traditional methods of analysis. To facilitate implementation in casework, one of the more robust models (aNN) is incorporated into a web-based application, ComboMaMD Analytical, to facilitate cranial and postcranial MMS traits analysis for ancestry estimation.

A new compsognathid theropod dinosaur from the oldest assemblage of the Jehol Biota in the Lower Cretaceous Huajiying Formation, northeastern China

Compsognathids — long regarded as an assemblage of ‘prototypical’ small theropods including the historically significant Compsognathus and Sinosauropteryx — have patchy distributions. The majority of definitive members of the clade come from the Upper Jurassic Solnhofen Archipelago and the Lower Cretaceous Yixian Formation. Chronologically falling between these two major compsognathid localities, a new compsognathid described in this paper, Xunmenglong yingliangis gen. et sp. nov, occurs in the Huajiying Formation of northeastern China. Xunmenglong is distinguished from other compsognathids by one autapomorphy (pedal phalanx IV-4 longer than IV-3) and a unique combination of postcranial traits, including the disproportionately long lower legs. Nested among the Jehol and Solnhofen compsognathids in a phylogenetic analysis, Xunmenglong is an intriguing addition to the known range and diversity of the clade. The taxon is stratigraphically the lowest among Asian compsognathids, and its holotype specimen is the smallest among compsognathids (unless Scipionyx is treated as a compsognathid). Questions remain about habitat preferences and diversification patterns of compsognathids, but Xunmenglong offers two broader implications. (1) As previously proposed on the basis of the diverse enanthiornithine assemblage, the Huajiying Formation may preserve the oldest fauna of the Early Cretaceous Jehol Biota, which is distinct from the Late Jurassic Daohugou Biota and includes the Yixian Formation from which other Asian compsognathids were discovered. (2) Xunmenglong provides a useful calibration point with which to reconstruct biogeographic/stratigraphic patterns and to estimate allometric trends in the clade.

Non-metric traits, physiological stress indicators and paleopathological lesion on human skeletal remains from an early modern cemetery in Wyszyński Street, Wrocław, Poland (15th–18th centuries AD)

The anthropological analysis and assessment of the living conditions of historical populations should be comprehensive. Due to the scarcity of the well-preserved skeletal remains of a population buried at the cemetery in Wyszyński Street, Wrocław, each piece of information is particularly important in providing the complementary information about living and health conditions of late medieval and early modern inhabitants of Wrocław. This study aims to assess the living conditions of the late medieval and early modern Wrocław inhabitants. This aim was reached by analyzing the frequency of non-metrical cranial and postcranial traits, physiological stress indicators, and pathological lesions. The importance of these traits for population studies is also discussed. For 98 skeletons (22.4% male and 37.8% female) from a cemetery located in Wyszyński Street, (15th –18th centuries AD), the frequencies (p) of the following traits were analyzed: 38 non-metric cranial and 9 post-cranial traits, the morphological indicators of physiological stress (i.e. cribra orbitalia and enamel hypoplasia), caries and pathological lesions on bones. Among the non-metric cranial traits, only nine (23.7%) were not observed. The most frequent (from p= 0.30 to p=0.65) were foramen parietale, incisura frontalis accesoria seu foramen frontale accesorius, foramen supraorbitale, M3 mandibulare, ossicula suturae lambdoideae, and foramen mastoideum extrasuturale. Only three non-metric post-cranial traits were observed, but with low frequency (p=0.01 and 0.02). Cribra orbitalia was present in 37.0% of the skeletons while enamel hypoplasia was present in only 2.6%. Susceptibility to caries occurred in 68% of the cases while carries lesions occurred in 31.2%. Among pathological changes, the most frequent were degenerative changes (21.6%) and injuries (19.6%). Owing to the poorly preserved remains, the complete assessment of the living conditions of the population was difficult. The number of the observed traits would have probably increased, had the number of complete and well-preserved skeletons been higher. The results of the study suggest that the living conditions of the studied population were poor. It is hypothesized that the cemetery was a burial place for prisoners and victims of various epidemics that affected the city. But since the historical sources of this cemetery are scarce, it is hard to unequivocally state its purpose with certainty.

Sexual dimorphism in postcranial skeletal shape suggests male-biased specialization for physical competition in anthropoid primates.

Sexual dimorphism often arises as a response to selection on traits that improve a male's ability to physically compete for access to mates. In primates, sexual dimorphism in body mass and canine size is more common in species with intense male-male competition. However, in addition to these traits, other musculoskeletal adaptations may improve male fighting performance. Postcranial traits that increase strength, agility, and maneuverability may also be under selection. To test the hypothesis that males, as compared to females, are more specialized for physical competition in their postcranial anatomy, we compared sex-specific skeletal shape using a set of functional indices predicted to improve fighting performance. Across species, we found significant sexual dimorphism in a subset of these indices, indicating the presence of skeletal shape sexual dimorphism in our sample of anthropoid primates. Mean skeletal shape sexual dimorphism was positively correlated with sexual dimorphism in body size, an indicator of the intensity of male-male competition, even when controlling for both body mass and phylogenetic relatedness. These results suggest that selection on male fighting ability has played a role in the evolution of postcranial sexual dimorphism in primates.

Brain size and organization in the Middle Pleistocene hominins from Sima de los Huesos. Inferences from endocranial variation

The Sima de los Huesos (SH) endocranial sample includes 16 complete or partial endocasts corresponding to European Middle Pleistocene hominins. Different anatomical and molecular studies have demonstrated that these hominins are phylogenetically related to Neanderthals, thus making them the earliest unquestionable representatives of the Neanderthal lineage. The description of endocranial variation in this population is fundamental to shedding light on the evolution of the Neanderthal brain. In this contribution, we analyze and describe endocranial variation in this sample, including aspects related to brain size (endocranial volume and encephalization) and brain organization (through qualitative descriptions and quantitative analyses). Our results indicate that the SH hominins show a transitional state between a primitive hominin endocranial configuration (which is found in Homo erectus and non-SH Middle Pleistocene Homo) and the derived configurations found in Neanderthals and modern humans, without a clear anticipation of classic Neanderthal endocranial traits. In comparison with other cranial and postcranial traits that show a fully Neanderthal or clear pre-Neanderthal condition in the SH collection, endocranial variation in these hominins is surprisingly primitive and shows no Neanderthal affinity. These results and the comparison with other cranial traits confirm that Neanderthals evolved in a mosaic fashion. Traits related to mastication (dental, facial and mandibular anatomy) led the Neanderthalization process, whereas neurocranial anatomy must have acquired a fully Neanderthal condition considerably later.

Morphological integration of anatomical, developmental, and functional postcranial modules in the crab-eating macaque (Macaca fascicularis).

Integration and modularity reflect the coordinated action of past evolutionary processes and, in turn, constrain or facilitate phenotypic evolvability. Here, we analyze magnitudes of integration in the macaque postcranium to test whether 20 a priori defined modules are (1) more tightly integrated than random sets of postcranial traits, and (2) are differentiated based on mode of definition, with developmental modules expected to be more integrated than functional or anatomical modules. The 3D morphometric data collected for eight limb and girdle bones for 60 macaques were collated into anatomical, developmental, and functional modules. A resampling technique was used to create random samples of integration values for each module for statistical comparison. Our results found that not all a priori defined modules were more strongly integrated than random samples of postcranial traits and that specific types of modules did not present consistent patterns of integration. Rather, girdle and joint modules were consistently less integrated than limb modules, and forelimb elements were less integrated than hindlimbs. The results suggest that morphometrically complex modules tend to be less integrated than simple limb bones, irrespective of the number of available traits. However, differences in integration of the fore- and hindlimb more likely reflects the multitude of locomotory, feeding, and social functions involved. It remains to be tested whether patterns of integration identified here are primate universals, and to what extent they vary depending on phylogenetic or functional factors.

Biological distance at the Ryan Mound site.

The Ryan Mound site in California spans 2000 years and has been utilized in over 200 studies. The Ryan Mound has been assumed to be a culturally and, therefore, a biologically continuous population over time. This study attempts to determine whether adults at the Ryan Mound consisted of a continuous population over the span of three temporal periods by using nonmetric skeletal traits. Thirty-eight nonmetric cranial traits and four nonmetric post-cranial traits were scored on adults. Trait correlations were assessed for sex and age using chi-square and Fisher's exact tests. For bilateral traits, data were recorded for both sides, but only results from the left side are reported. Most data were recorded as present or absent. Twelve traits had scores that had more than two nominal categories, which were converted to binary values to enable mean measure of divergence (MMD) statistical analyses. After data reduction, 36 traits remained. Using these traits, standardized MMD analyses revealed that the oldest temporal period and the most recent temporal period individuals were significantly different. This study illustrates the importance of testing for biological continuity. Nonmetric studies provide a way to examine relationships within a sample to determine biological continuity. For the Ryan Mound, new populations may have moved into the region early on as part of the Meganos intrusion, or new populations may have moved into the region later, between AD 1500 and AD 1800. Comparative data from nearby sites further support the Meganos intrusion theory.

Decoupled diversification dynamics of feeding morphology following a major functional innovation in marine butterflyfishes.

The diversity of fishes on coral reefs is influenced by the evolution of feeding innovations. For instance, the evolution of an intramandibular jaw joint has aided shifts to corallivory in Chaetodon butterflyfishes following their Miocene colonization of coral reefs. Today, over half of all Chaetodon species consume coral, easily the largest concentration of corallivores in any reef fish family. In contrast with Chaetodon, other chaetodontids, including the long-jawed bannerfishes, remain less intimately associated with coral and mainly consume other invertebrate prey. Here, we test (i) if intramandibular joint (IMJ) evolution in Chaetodon has accelerated feeding morphological diversification, and (ii) if cranial and post-cranial traits were affected similarly. We measured 19 cranial functional morphological traits, gut length and body elongation for 33 Indo-Pacific species. Comparisons of Brownian motion rate parameters revealed that cranial diversification was about four times slower in Chaetodon butterflyfishes with the IMJ than in other chaetodontids. However, the rate of gut length evolution was significantly faster in Chaetodon, with no group-differences for body elongation. The contrasting patterns of cranial and post-cranial morphological evolution stress the importance of comprehensive datasets in ecomorphology. The IMJ appears to enhance coral feeding ability in Chaetodon and represents a design breakthrough that facilitates this trophic strategy. Meanwhile, variation in gut anatomy probably reflects diversity in how coral tissues are procured and assimilated. Bannerfishes, by contrast, retain a relatively unspecialized gut for processing invertebrate prey, but have evolved some of the most extreme cranial mechanical innovations among bony fishes for procuring elusive prey.

Osteological postcranial traits in hylid anurans indicate a morphological continuum between swimming and jumping locomotor modes.

Anurans exhibit a particularly wide range of locomotor modes that result in wide variations in their skeletal structure. This article investigates the possible correlation between morphological aspects of the hylid postcranial skeleton and their different locomotor modes and habitat use. To do so, we analyzed 18 morphometric postcranial variables in 19 different anuran species representative of a variety of locomotor modes (jumper, hopper, walker, and swimmer) and habitat uses (arboreal, bush, terrestrial, and aquatic). Our results show that the evolution of the postcranial hylid skeleton cannot be explained by one single model, as for example, the girdles suggest modular evolution while the vertebral column suggests other evolutionary modules. In conjunction with data from several other studies, we were able to show a relationship between hylid morphology and habitat use; offering further evidence that the jumper/swimmer and walker/hopper locomotor modes exhibit quite similar morphological architecture. This allowed us to infer that new locomotor modalities are, in fact, generated along a morphological continuum. J. Morphol. 278:403-417, 2017. © 2017 Wiley Periodicals, Inc.

New euprimate postcrania from the early Eocene of Gujarat, India, and the strepsirrhine–haplorhine divergence

The oldest primates of modern aspect (euprimates) appear abruptly on the Holarctic continents during a brief episode of global warming known as the Paleocene-Eocene Thermal Maximum, at the beginning of the Eocene (∼56 Ma). When they first appear in the fossil record, they are already divided into two distinct clades, Adapoidea (basal members of Strepsirrhini, which includes extant lemurs, lorises, and bushbabies) and Omomyidae (basal Haplorhini, which comprises living tarsiers, monkeys, and apes). Both groups have recently been discovered in the early Eocene Cambay Shale Formation of Vastan lignite mine, Gujarat, India, where they are known mainly from teeth and jaws. The Vastan fossils are dated at ∼54.5 Myr based on associated dinoflagellates and isotope stratigraphy. Here, we describe new, exquisitely preserved limb bones of these Indian primates that reveal more primitive postcranial characteristics than have been previously documented for either clade, and differences between them are so minor that in many cases we cannot be certain to which group they belong. Nevertheless, the small distinctions observed in some elements foreshadow postcranial traits that distinguish the groups by the middle Eocene, suggesting that the Vastan primates—though slightly younger than the oldest known euprimates—may represent the most primitive known remnants of the divergence between the two great primate clades.

The place of Homo floresiensis in human evolution.

Two main evolutionary scenarios have been proposed to explain the presence of the small-bodied and small-brained Homo floresiensis species on the remote Indonesian island of Flores in the Late Pleistocene. According to these two scenarios, H. floresiensis was a dwarfed descendent of H. erectus or a late-surviving remnant of a older lineage, perhaps descended from H. habilis. Each scenario has interesting and important implications for hominin biogeography, body size evolution, brain evolution and morphological convergences. Careful evaluation reveals that only a small number of characters support each of these scenarios uniquely. H. floresiensis exhibits a cranial shape and many cranial characters that appear to be shared derived traits with H. erectus, but postcranial traits are more primitive and resemble those of early Homo or even australopiths. Mandibular and dental traits show a mix of derived and primitive features. Unfortunately, many traits cannot be used to assess these two hypotheses because their distribution in H. erectus, early Homo (e.g., H. habilis), or both is unknown. H. erectus ancestry implies evolutionary convergence on a postcranial configuration similar to australopiths and early Homo, which could be explained by a return to more climbing behaviors. Body size reduction as well as brain size reduction on a scale only rarely documented in mammals would also accompany the origin of H. floresiensis from a H. erectus ancestor. H. habilis ancestry implies parallel evolution of numerous cranial characters, as well as a few dentognathic traits. A pre-H. erectus ancestry also suggests an early migration to Southeast Asia that is as yet undocumented in mainland Asia, but minimal body and brain size reduction.

Ecogeography, genetics, and the evolution of human body form

Genetic resemblances among groups are non-randomly distributed in humans. This population structure may influence the correlations between traits and environmental drivers of natural selection thus complicating the interpretation of the fossil record when modern human variation is used as a referential model. In this paper, we examine the effects of population structure and natural selection on postcranial traits that reflect body size and shape with application to the more general issue of how climate – using latitude as a proxy – has influenced hominin morphological variation. We compare models that include terms reflecting population structure, ascertained from globally distributed microsatellite data, and latitude on postcranial phenotypes derived from skeletal dimensions taken from a large global sample of modern humans. We find that models with a population structure term fit better than a model of natural selection along a latitudinal cline in all cases. A model including both latitude and population structure terms is a good fit to distal limb element lengths and bi-iliac breadth, indicating that multiple evolutionary forces shaped these morphologies. In contrast, a model that included only a population structure term best explained femoral head diameter and the crural index. The results demonstrate that population structure is an important part of human postcranial variation, and that clinally distributed natural selection is not sufficient to explain among-group differentiation. The distribution of human body form is strongly influenced by the contingencies of modern human origins, which calls for new ways to approach problems in the evolution of human variation, past and present.

The Biological Affinity of the Ancient Populations of Altar de Sacrificios and Seibal

The question of biological affinity between ancient populations is often an intriguing one. Unfortunately, the fragmentary nature and paucity of skeletal remains usually obviate the possibility of using genetically determined cranial and postcranial traits to assess biological affinity. The teeth, due to their more durable nature present more potential for genetic analysis than the bony remains. Dental traits are ideal morphological characteristics on which to base estimates of genetic distance between populations. Twin and intrafamily studies have demonstrated that many morphological characteristics of the dentition are heritable (Kraus, 1951; Kraus and Furr, 1953; Kraus 1957; Ludwig, 1957; Lundstrom, 1963; Garn, Lewis and Polacheck, 1960; Green and Aszkler, 1970; Tsuji, 1958; Greene, 1967b). Population distribution studies have shown that populations can be differentiated on the basis of varying frequencies of particular dental traits (Hanihara, 1963 and 1967; Dahlberg, 1951; Greene, 1967a and 1967b).

Heads or tails: staged diversification in vertebrate evolutionary radiations

Adaptive radiations, bouts of morphological divergence coupled with taxonomic proliferation, underpin biodiversity. The most widespread model of radiations assumes a single round, or 'early burst', of elevated phenotypic divergence followed by a decline in rates of change or even stasis. A vertebrate-specific model proposes separate stages: initial divergence in postcranial traits related to habitat use, followed by diversification in cranial morphology linked to trophic demands. However, there is little empirical evidence for either hypothesis. Here, we show that, contrary to both models, separate large-scale radiations of actinopterygian fishes proceeded through distinct cranial and later postcranial stages of morphological diversification. Early actinopterygians and acanthomorph teleosts dispersed in cranial morphospace immediately following the end-Devonian extinction and the Cretaceous origin of the acanthomorph clade, respectively. Significant increases in postcranial morphological variation do not occur until one interval after cranial diversification commenced. Therefore, our results question the universality of the 'general vertebrate model'. Based on the results of model-fitting exercises and application of the divergence order test, we find little evidence that the early onset of cranial diversification in these two radiations is due to elevated rates of cranial change relative to postcranial change early in their evolutionary histories. Instead, postcranial and cranial patterns are best fit by an Ornstein-Uhlenbeck model, which is characterized by constant evolutionary rates coupled with a strong central tendency. Other groups have been reported to show early saturation of cranial morphospace or tropic roles early in their histories, but it is unclear whether these patterns are attributable to dynamics similar to those inferred for our two model radiations.

A new helmeted frog (Anura: Calyptocephalellidae) from an Eocene subtropical lake in northwestern Patagonia, Argentina

ABSTRACT Eocene caldera-lake deposits from Río Pichileufú have yielded anuran remains in association with a taxonomically diverse flora. The floral evidence suggests that these anurans lived under climatic conditions similar to those of extant subtropical rainforests. One of the anurans is a helmeted neobatrachian, which is represented by articulated remains and represents a new species that can be assigned to the extant genus Calyptocephalella on the basis of both cranial and postcranial traits. Calyptocephalella pichileufensis, gen. et sp. nov., indicates that, despite the relatively conservative skeletal anatomy of the genus, Calyptocephalella has not always been associated with the temperate austral forests that it inhabits today. The new species also provides evidence of a biotic link with Australia, which has been proposed on the basis of other faunal and floral records, as well as on the paleogeographic history of Patagonia during the mid-Cretaceous–Eocene interval. We also discuss the significance of neobatrachian cranial features that might reflect hyperossification.

Comparative morphometric study of the Slovakian wildcat population ( Felis silvestris silvestris): Evidence for a low rate of introgression?

Statistical analyses of 60 cranial and six postcranial characters of 105 domestic cats and 77 wildcats from Slovakia showed that the two forms can be separated on the basis of just a few morphometric traits. To test the distinguishing power of these characters we first pre-classified the specimens of our sample as wildcat or domestic cat on the basis of the cranial volume, which is a non-overlapping diagnostic character in most populations investigated so far. Pearson's r correlation matrix of all 60 cranial traits showed a high degree of correlation. A linear discriminant analysis, excluding cranial volume, showed that maximal length of M 1, distance between foramen rotundum and foramen ovale and diameter of porus acusticus externus was necessary to separate the two forms. When postcranial traits were included, tibia length, femur length and distance between foramen rotundum and foramen ovale sufficed to assign the individuals to the correct group, with just one misclassification. Distinguishing between all four possible groups (domestic/wild versus male/female) was only partially possible, with a minimum 5% misclassification rate always with regard to sex. The results of the principal component analysis underlined that domestic cats and wildcats can be identified unequivocally on the basis of a set of morphometric measurements even in the absence of the best discriminating traits. In comparison with a reference population from Thuringia, Germany that the authors had studied previously, the morphological differences between domestic cats and wildcats are much more pronounced in Slovakia. Moreover, the ranking of the diagnostic value of characters differs between populations. As possible explanations for this finding, we discuss the theory of an east-west gradient in body size caused by a more maritime climate in the west and a more continental one in the east, and that of a lower degree of introgression and hybridization between the two forms in the Slovakian population.

Postcranial anatomy of Platypterygius americanus (Reptilia: Ichthyosauria) from the Cretaceous of Wyoming

ABSTRACT Ichthyosaurs remains from the Albian and Cenomanian of Wyoming have been assigned to Platypterygius americanus, but apart from structures of the distal humerus, few other unequivocal character states have been proposed to differentiate this species from its congeners. The purpose of this study was to reevaluate the postcranial morphology of Platypterygius americanus, in order to assess the validity of this species and distinguish postcranial traits relevant for specific diagnoses. Several applicable features were identified, including the location of extrazeugopodial facets on the distal humerus and femur, shape of the intermedium, relative degree of fusion within the atlas-axis complex, number of presacral centra, and varying lengths of the anterior caudal centra. Comparative assessment suggests that Platypterygius americanus is a valid taxon, and that it is possible to differentiate the various Platypterygius spp. independent of stratigraphical and/or geographical occurrence data. Nevertheless, a future review of cranial morphology in all Platypterygius spp. is necessary to bolster these conclusions.