Extant Felids Research Articles

Extensive Phylogenomic Discordance and the Complex Evolutionary History of the Neotropical Cat Genus Leopardus.

Even in the genomics era, the phylogeny of Neotropical small felids comprised in the genus Leopardus remains contentious. We used whole-genome resequencing data to construct a time-calibrated consensus phylogeny of this group, quantify phylogenomic discordance, test for interspecies introgression, and assess patterns of genetic diversity and demographic history. We infer that the Leopardus radiation started in the Early Pliocene as an initial speciation burst, followed by another in its subgenus Oncifelis during the Early Pleistocene. Our findings challenge the long-held notion that ocelot (Leopardus pardalis) and margay (L. wiedii) are sister species and instead indicate that margay is most closely related to the enigmatic Andean cat (L. jacobita), whose whole-genome data are reported here for the first time. In addition, we found that the newly sampled Andean tiger cat (L. tigrinus pardinoides) population from Colombia associates closely with Central American tiger cats (L. tigrinus oncilla). Genealogical discordance was largely attributable to incomplete lineage sorting, yet was augmented by strong gene flow between ocelot and the ancestral branch of Oncifelis, as well as between Geoffroy's cat (L. geoffroyi) and southern tiger cat (L. guttulus). Contrasting demographic trajectories have led to disparate levels of current genomic diversity, with a nearly tenfold difference in heterozygosity between Andean cat and ocelot, spanning the entire range of variability found in extant felids. Our analyses improved our understanding of the speciation history and diversity patterns in this felid radiation, and highlight the benefits to phylogenomic inference of embracing the many heterogeneous signals scattered across the genome.

Distribution of the northern pampas cat, Leopardus garleppi, in northern South America, confirmation of its presence in Colombia and genetic analysis of a controversial record from the country

Abstract The common name of pampas cat includes a complex of small Neotropical felid species found in various habitats of South America. Recently several species of this complex were proposed, but there are few records in the northernmost distribution of the continent, and reports of the pampas cat’s presence in Colombia have been ambiguous. Current northern limits of Leopardus garleppi are limited to the Andes of Ecuador. Here we present the northernmost record of the species, validating its presence in Colombia and review previous controversial records from the country. The new record is based on a road-killed specimen in a dry tropical forest ecosystem in the municipality of Mercaderes, Department of Cauca. Our morphological and genetic comparisons also shown that a previous record from Colombia supported by a single skin recently used to described a new species named Leopardus narinensis belong to Leopardus tigrinus. With the information compiled from new localities in Colombia and Ecuador, the known distribution range for L. garleppi is increased towards the northern part of South America into areas of Tropical Dry Forest. The distribution now includes 14 ecoregions from Colombia to Bolivia, and four in Colombia (Eastern Cordillera real montane forests, Northwestern Andean montane forests, Northern Andean paramo, and the Patía Valley dry forests), which correspond to similar ecosystems inhabited by the species in other Andean landscapes. The potential distribution hypothesis showed that the species has high suitability in large areas of southwestern Colombia (Nariño). With the recording of L. garleppi in Colombia, the number of extant felid species in the country has increased to seven.

The roar of Rancho La Brea? Comparative anatomy of modern and fossil felid hyoid bones.

Animal vocalization is broadly recognized as ecologically and evolutionarily important. In mammals, hyoid elements may influence vocalization repertoires because the hyoid apparatus anchors vocal tissues, and its morphology can be associated with variation in surrounding soft-tissue vocal anatomy. Thus, fossil hyoid morphology has the potential to shed light on vocalizations in extinct taxa. Yet, we know little about the hyoid morphology of extinct species because hyoid elements are rare in the fossil record. An exception is found in the Rancho La Brea tar pits in Los Angeles, California, where enough hyoids have been preserved to allow for quantitative analyses. The La Brea Tar Pits and Museum houses one of the largest and most diverse collections of carnivore fossils, including hyoid elements from the extinct felids Smilodon fatalis and Panthera atrox. Here, we found that extant members of Felinae (purring cats) and Panthera (roaring cats) showed characteristic differences in hyoid size and shape that suggest possible functional relationships with vocalization. The two extinct taxa had larger and more robust hyoids than extant felids, potentially reflecting the ability to produce lower frequency vocalizations as well as more substantial muscles associated with swallowing and respiration. Based on the shape of the hyoid elements, Panthera atrox resembled roaring cats, while Smilodon fatalis was quite variable and, contrary to suggestions from previous research, more similar overall to purring felids. Thus P. atrox may have roared and S. fatalis may have produced vocalizations similar to extant purring cats but at a lower frequency. Due to the confounding of vocalization repertoire and phylogenetic history in extant Felidae, we cannot distinguish between morphological signals related to vocalization behavior and those related to shared evolutionary history unrelated to vocalization.

A morphological analysis of carnivoran ossicles from Rancho La Brea.

The morphology of the mammalian middle ear-including the size, shape, and stiffness of individual ossicles-controls their vibrational response to sound and, is closely related to an animal's auditory capabilities. While the relationship between middle ear morphology and hearing frequency has been explored in living carnivorans, the size and shape of ossicles in fossil carnivorans have been sparsely documented. In this study, we present the first morphological data on four iconic carnivoran taxa from the Rancho La Brea Tar Pits: Smilodon fatalis, Panthera atrox, Canis dirus, and Arctodus simus. These data are contextualized with samples of extant felids, canids, and ursids to determine the extent to which the ossicles of these iconic fossil taxa resemble their living relatives. Six, five, and seven linear measurements were taken from the malleus, incus, and stapes, respectively. Comparisons of geometric means reveal that the ossicles of fossil canids and felids are similar in size to living analogs, but those of A. simus are significantly larger than those of any living ursid. Further, principal components analyses demonstrate close morphological affinities between fossil and extant taxa within canids and felids, and again, a greater disparity between fossil and extant ursids. Canids and ursids occupy distinct regions of the morphospace, yet both overlap the morphological range spanned by felids. While some elements-for example, the stapes-require further specimens to facilitate more nuanced interpretations of variation, our findings underscore the need for concerted efforts towards identifying and preserving these bones within fossil assemblages.

A POSSIBLESMILODON(MAMMALIA, FELIDAE) COPROLITE FROM THE PLEISTOCENE OF ARGENTINA

ABSTRACTPleistocene large carnivores from the Pampean Region have been studied almost always based on bone remains. Here we report the first coprolite of a large carnivore from the Late Pleistocene of the Pampean Region, Argentina. The coprolite was found associated with megafauna bone remains and it shows the typical shape and size of a carnivorous mammal, with a length of 240 mm and a maximum diameter of 39.59 mm. The coprolite contains two bones of the autopodium of an artiodactyl, and numerous dermal ossicles of giant terrestrial sloths. The coprolite's composition, size, and shape allow us to discard ursids, canids, and small felids. Ursid and canid feces contain abundant plant remains, which are absent in the coprolite described here. Feces of extant felids are smaller than the coprolite here as they do not exceed 130 mm in length and 30 mm in diameter. Based on size, shape, and bone inclusions, the discovered coprolite may be attributed to the Machairodontinae saber-toothed felid Smilodon. If correctly identified, this coprolite sheds light on predatory habits of Smilodon.

Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon

Reconstructing the behavior of extinct species is challenging, particularly for those with no living analogues. However, damage preserved as paleopathologies on bone can record how an animal moved in life, potentially reflecting behavioral patterns. Here, we assess hypothesized etiologies of pathology in a pelvis and associated right femur of a Smilodon fatalis saber-toothed cat, one of the best-studied species from the Pleistocene-age Rancho La Brea asphalt seeps, California, USA, using visualization by computed tomography (CT). The pelvis exhibits massive destruction of the right hip socket that was interpreted, for nearly a century, to have developed from trauma and infection. CT imaging reveals instead that the pathological distortions characterize chronic remodeling that began at birth and led to degeneration of the joint over the animal’s life. These results suggest that this individual suffered from hip dysplasia, a congenital condition common in domestic dogs and cats. This individual reached adulthood but could not have hunted properly nor defended territory on its own, likely relying on a social group for feeding and protection. While extant social felids are rare, these fossils and others with similar pathologies are consistent with a spectrum of social strategies in Smilodon supported by a predominance of previous studies.

Pleistocene extinction and geographic singularity explain differences in global felid ensemble structure

Extant felids are hyper-carnivorous predators that originated in Asia c. 11 Mya and diversified in 8 distinct lineages, with 41 species surviving to the Recent. These species occupy almost every terrestrial habitat available in the four continental land masses they occupy and exhibit morphological and behavioral specializations to various locomotor styles and hunting modes. Today, distinct felid ensembles inhabit each continent and major biogeographic region. How the differential structuring of these ensembles was generated, and which evolutionary processes shaped these differences across ensembles, are key emerging questions. Using multivariate statistics, we analyzed a large dataset of 31 cranial and 92 postcranial linear variables describing shape and functional proxies of the entire skeleton of extant felids. We statistically demonstrate the existence of nine felid morphotypes at the global scale, whose occurrence is characteristic of different continental or biogeographic ensembles. Phylogenetically explicit analyses show that morphotypes from different felid lineages converged in different continents, but still ensembles remain distinct due to the fact that various morphotypes are missing in several of those ensembles. However, fossil evidence suggests that most of these missing morphotypes were represented by species from those territories that went extinct during the Quaternary. Furthermore, reconstructing the hypothetical felid ensembles before Pleistocene extinctions rendered the continental felid faunas remarkably more similar to each other than they presently are, leaving their remaining, relatively minor differences to outstanding geographic singularities of each continental land mass.

Genomic Adaptations and Evolutionary History of the Extinct Scimitar-Toothed Cat, Homotherium latidens

SummaryHomotherium was a genus of large-bodied scimitar-toothed cats, morphologically distinct from any extant felid species, that went extinct at the end of the Pleistocene [1, 2, 3, 4]. They possessed large, saber-form serrated canine teeth, powerful forelimbs, a sloping back, and an enlarged optic bulb, all of which were key characteristics for predation on Pleistocene megafauna [5]. Previous mitochondrial DNA phylogenies suggested that it was a highly divergent sister lineage to all extant cat species [6, 7, 8]. However, mitochondrial phylogenies can be misled by hybridization [9], incomplete lineage sorting (ILS), or sex-biased dispersal patterns [10], which might be especially relevant for Homotherium since widespread mito-nuclear discrepancies have been uncovered in modern cats [10]. To examine the evolutionary history of Homotherium, we generated a ∼7x nuclear genome and a ∼38x exome from H. latidens using shotgun and target-capture sequencing approaches. Phylogenetic analyses reveal Homotherium as highly divergent (∼22.5 Ma) from living cat species, with no detectable signs of gene flow. Comparative genomic analyses found signatures of positive selection in several genes, including those involved in vision, cognitive function, and energy consumption, putatively consistent with diurnal activity, well-developed social behavior, and cursorial hunting [5]. Finally, we uncover relatively high levels of genetic diversity, suggesting that Homotherium may have been more abundant than the limited fossil record suggests [3, 4, 11, 12, 13, 14]. Our findings complement and extend previous inferences from both the fossil record and initial molecular studies, enhancing our understanding of the evolution and ecology of this remarkable lineage.

Ecometrics and Neogene faunal turnover: the roles of cats and hindlimb morphology in the assembly of carnivoran communities in the New World

Cats possess some of the highest ankle gear ratios of any extant carnivorans, a feature that facilitates leaping and sprinting involved in ambush predation and scansorial lifestyles. In today's North American carnivoran communities, the high gear ratio of cats contributes to an overall high ecometric average for this trait and contributes strongly to measures of ecometric disparity at the community level. But cats were late additions to North American communities, arriving from Eurasia about 17 Ma at the end of the “cat gap”. This paper uses ecometric analysis to document changes in hindlimb functional diversity in North American carnivoran communities over the last 19 million years in order to better understand the roles of trait evolution, clade turnover, and environmental change in community assembly. To accomplish this, I look at the phylogenetic history of ankle gear ratios of cats and other carnivorans, and the history of their occupation of high gear ratio niches in North American communities. The primary focus is on the Great Plains, which experienced profound changes in vegetation and climate through this period. Across all Carnivoramorpha, including a variety of extinct clades, it was found that gear ratios range from 1.08 (with extant ursids and viverrids and extinct miacids and barbourofelids, one of the three cat groups considered in this paper, having the lowest values) to 1.46 (with extant felids, herpestids, and canids having the highest values). Using the fossil record combined with phylogenetic ancestor reconstruction, it is shown that stem carnivorans and early felids had gear ratios about halfway between these extremes, consistent with a semidigitigrade or mildly digitigrade stance that was not overly specialized for either leaping or sprinting. Barbourofelids and some machairodontines evolved lower gear ratios that emphasized mechanical efficiency over advantage. When cats first entered North American communities in the Miocene they did not occupy high gear ratio niches and, in fact, occupied some of the lowest gear ratio niches during the Barstovian, Clarendonian, and Hemphillian. A major restructuring of gear ratio distributions in North American carnivoran communities occurred during the Blancan that appears to have resulted from clade sorting processes involving the selective loss of low gear ratio groups, as well as the evolution of increased gear ratios in felids and canids.

Correlated Evolution of White Spots on Ears and Closed Habitat Preferences in Felids

The pigmentation patterns of many carnivorous mammals comprise contrasting white patches of hair in different parts of the body whose evolution remains largely misunderstood. Some felids (Felidae) exhibit conspicuous white spots on the posterior part of the ears, while the ear color of others is uniform. On the basis that ear movement in felids has a role in intraspecific communication and that color contrast enhances detection, here it is hypothesized that white spots on ears may be particularly adaptive under conditions of poor visibility and thus be associated with the occupancy of closed habitats. This prediction was tested using phylogenetic logistic regression models with all species of extant felids. Results show a clear association between the occurrence of white spots on ears and preference for closed habitats, and this is independent of body size and whether species that occupy both closed and open habitats are considered as closed- or open-habitat specialists. Phylogenetic signal analyses indicate that the occurrence of white spots on ears is a highly conserved trait while habitat preferences are evolutionarily labile, suggesting that the presence of white spots may have partly contributed to the adaptation of felids to closed habitats. These findings indicate that some subtle pigment traits have fulfilled a significant role in determining the success of habitat occupancy by felids and possibly other mammals, which in turn has driven the evolutionary maintenance of such traits.

Reproductive biology of the 38 extant felid species: a review

Abstract Knowledge of reproductive biology is crucial to improving in situ and ex situ breeding programmes for felids. We reviewed the available literature (223 publications) on the reproductive biology of all 38 felid species. We found that 78% of the publications (173) were focused on either or both the oestrous cycles (84) or ejaculate traits (92) of felids. Literature was biased towards the domestic cat Felis catus (31), the cheetah Acinonyx jubatus (27), and the panthera lineage (66). There was a paucity of literature on the caracal lineage (7), the bay cat lineage (3), members of the domestic cat lineage other than the domestic cat (11), and several species of the ocelot lineage. The mean duration of oestrus varies little between the different lineages and species (mean 5.2 days, range 1–10 days, nE = 2265). However, the duration of interoestrus varies greatly in most species (e.g. 1–118 days in the domestic cat). Gestation length also varies significantly between species, but is similar within each lineage and related to adult body size. Non‐pregnant luteal phases appear to persist for half the duration of pregnant luteal phases (48%, 21–71 days, nE = 256; c.f. previous reports of one‐third the duration of pregnant luteal phases). Sperm motility (sperm motility index), sperm viability, and acrosome intactness are high in the fresh ejaculates of most felid species [69% (26–90%, nE = 2104), 69% (49–87%, nE = 443), and 84% (21–100%, nE = 1763), respectively]. Teratospermia is highly prevalent within Felidae, but is particularly problematic for the puma and lynx lineages [ejaculates with 76% (63–94%) and 79% (63–98%) abnormal sperm, respectively]. Teratospermia appears to be linked to low genetic diversity. The maintenance and enhancement of genetic diversity through the use of assisted reproductive technologies should be a long‐term goal for felid conservation management. A short‐term management goal should be to improve the success of assisted reproductive technologies in felids by minimising captivity‐related stress, which can adversely affect fertility and ovarian activity.

Learning from the past to prepare for the future: felids face continued threat from declining prey

Many contemporary species of large‐felids (≥ 15 kg) feed upon prey that are endangered, raising concern that prey population declines (defaunation) will further threaten felids. We assess the threat that defaunation presents by investigating a late Quaternary (LQ), ‘present‐natural’ counterfactual scenario. Our present‐natural counterfactual is based on predicted ranges of mammals today in the absence of any impacts of modern humans Homo sapiens through time. Data from our present‐natural counterfactual are used to understand firstly how megafauna extinction has impacted felid communities to date and secondly to quantify the threat to large‐felid communities posed by further declines in prey richness in the future. Our purpose is to identify imminent risks to biodiversity conservation and their cascading consequences and, specifically, to indicate the importance of preserving prey diversity.We pursue two lines of enquiry; first, we test whether the loss of prey species richness is a potential cause of large‐felid extinction and range loss. Second, we explore what can be learnt from the large‐scale large‐mammal LQ losses, particularly in the Americas and Europe, to assess the threat any further decline in prey species presents to large‐felids today, particularly in Africa and Asia.Large‐felid species richness was considerably greater under our present‐natural counterfactual scenario compared to the current reality. In total, 86% of cells recorded at least one additional felid species in our present‐natural counterfactual, and up to 4–5 more large‐felid species in 10% of the cells. A significant positive correlation was recorded between the number of prey species lost and the number of large‐felid species lost from a cell. Extant felids most at risk include lion and Sunda clouded leopard, as well as leopard and cheetah in parts of their range. Our results draw attention to the continuation of a trend of megafauna decline that began with the emergence of hominins in the Pleistocene.

Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis.

Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation.

Patterns of sexual dimorphism in the Persian Leopard (Panthera pardus saxicolor) and implications for sex differentiation

Extant felids show a high degree of inter-sexual dimorphism, meaning significant size differences between males and females. Such a differentiation may have various ecological, behavioural and evolutionary implications, at both species and subspecies levels. We have investigated the sexual size differences in one of the most dimorphic felids, i.e. the Leopard (Panthera pardus), based on 63 craniometric and 55 morphometric samples from Iran which belong to the subspecies Persian Leopard (P. p. saxicolor). In order to explore patterns of sexual dimorphism, multivariate statistical analysis on 24 skull variables as well as univariate approaches for two body measurements were applied. We found significant inter-sexual differences in skull size whereas it was not meaningful after removing the effect of size to address skull shape. Moreover, inter-sexual differentiation was also remarkable when comparing morphometric body measurements in adults, showing that the males possess a larger head mass and longer body, but sub-adults did not show any remarkable differentiation between sexes. A combination of craniometric and morphological features is proposed for sex differentiation in Leopards.

Determination of hip-joint loading patterns of living and extinct mammals using an inverse Wolff's law approach.

It is well known that bone adapts its microstructure in response to loading. Based on this form-follows-function relationship, we previously developed a reverse approach to derive joint loads from bone microstructure as acquired with micro-computed tomography. Here, we challenge this approach by calculating hip-joint loading patterns for human and dog, two species exhibiting different locomotion, and comparing them to in vivo measurements. As a proof of concept to use the approach also for extinct taxa, we applied it to a cave lion fossil bone. Calculations were in close agreement with in vivo measurements during walking for extant species, showing distinguished patterns for bipedalism and quadrupedalism. The cave lion calculations clearly revealed its quadrupedal locomotion and suggested a more diverse behaviour compared to the dog, which is in agreement with extant felids. This indicates that our novel approach is potentially useful for making inferences about locomotion in living as well as extinct mammals and to study evolutionary joint development.

Habitat adaptations in the felid forearm

Extant cats inhabit different kinds of habitat, for example open landscapes, forests, and rocky mountainous areas. In this study, the radius and ulna of extant felids were investigated to identify ecomorphological adaptations to different habitats. Simple scatter plots and multivariate analyses (factor analysis, discriminant function analysis) revealed two distinct clusters of cats preferring open habitats to cats preferring closed habitats (i.e., forests). We also applied our approach to an existing, large database of extant cats to determine the effect of intraspecific variation on the forearm bones. According to our dataset, cat species adapted to closed habitats have relatively shorter but thicker forearm bones whereas those with longer and slimmer forearms are adapted to open habitats. Cats that inhabit mountainous habitats show no distinct differences in adaptation and plot in one of the other two habitat categories. Overall, the radius measurements are sufficient to distinguish open and forest habitats, but with inclusion of the ulna measurements, the results are more confident. The presented method of using just four measurements of the forearm bones has much potential for application to fossil taxa. We tested the approach for fossil taxa from the Miocene to Pleistocene with the result that most fossil felids were adapted to closed habitats but with some species being adapted to more open intermediate habitats.

Pleistocene Extinctions and the Perceived Morphofunctional Structure of the Neotropical Felid Ensemble

The felid Neotropical ensemble has experienced important changes from the Pleistocene to the present, the extinction of sabertooth cats being the most significant. Assuming that the morphofunctional structure of the Neotropical felid ensemble was maximally expressed when machairodontines were present, we added specimens of Smilodon fatalis and S. populator to a morphological dataset inclusive of all extant species of Neotropical felids to explore the hypothetical effect of extinction of machairodontines on the perceived morphofunctional structure of the ensemble. We studied 321 specimens of 12 extant species of Neotropical felids plus S. populator and S. fatalis by measuring 123 skull and postcranial morphofunctional variables. We used Principal Component Analysis to find morphofunctional patterns of the skull, postcranium, and both combined (with and without correction for size) of both ensembles, past (with Smilodon) and present (with Smilodon lost to extinction). Canonical Phylogenetic Ordination was performed to assess the degree of phylogenetic influence on this morphospace. We also explored the effect of including homotherines in the Pleistocene guild by including specimens of North American Homotherium serum. Size was the principal factor structuring ensembles. Important morphological characters were associated to ecological performance of species. A pattern of bodily proportions was apparent: more stout species with larger skull, longer rostrum, stronger bite force, and longer pectoral crests, versus gracile, jumping species with opposing characters. The felid morphospace shrank after the extinction of Smilodon and Homotherium, but the configuration of the portion of space containing extant felids remained stable. This pattern is associated with deep phylogenetic roots.

Ecomorphology of the African felid ensemble: The role of the skull and postcranium in determining species segregation and assembling history

Morphology of extant felids is regarded as highly conservative. Most previous studies have focussed on skull morphology, so a vacuum exists about morphofunctional variation in postcranium and its role in structuring ensembles of felids in different continents. The African felid ensemble is particularly rich in ecologically specialized felids. We studied the ecomorphology of this ensemble using 31 cranial and 93 postcranial morphometric variables measured in 49 specimens of all 10 African species. We took a multivariate approach controlling for phylogeny, with and without body size correction. Postcranial and skull+postcranial analyses (but not skull-only analyses) allowed for a complete segregation of species in morphospace. Morphofunctional factors segregating species included body size, bite force, zeugopodial lengths and osteological features related to parasagittal leg movement. A general gradient of bodily proportions was recovered: lightly built, long-legged felids with small heads and weak bite forces vs. the opposite. Three loose groups were recognized: small terrestrial felids, mid-to-large sized scansorial felids and specialized Acinonyx jubatus and Leptailurus serval. As predicted from a previous study, the assembling of the African felid ensemble during the Plio-Pleistocene occurred by the arrival of distinct felid lineages that occupied then vacant areas of morphospace, later diversifying in the continent.

Variation in craniomandibular morphology and sexual dimorphism in pantherines and the sabercat Smilodon fatalis.

Sexual dimorphism is widespread among carnivorans, and has been an important evolutionary factor in social ecology. However, its presence in sabertoothed felids remains contentious. Here we present a comprehensive analysis of extant Panthera and the sabertoothed felid Smilodon fatalis. S. fatalis has been reported to show little or no sexual dimorphism but to have been intraspecifically variable in skull morphology. We found that large and small specimens of S. fatalis could be assigned to male and female sexes with similar degrees of confidence as Panthera based on craniomandibular shape. P. uncia is much less craniomandibularly variable and has low levels of sexual size-dimorphism. Shape variation in S. fatalis probably reflects sexual differences. Craniomandibular size-dimorphism is lower in S. fatalis than in Panthera except P. uncia. Sexual dimorphism in felids is related to more than overall size, and S. fatalis and the four large Panthera species show marked and similar craniomandibular and dental morphometric sexual dimorphism, whereas morphometric dimorphism in P. uncia is less. Many morphometric-sexually dimorphic characters in Panthera and Smilodon are related to bite strength and presumably to killing ecology. This suggests that morphometric sexual dimorphism is an evolutionary adaptation to intraspecific resource partitioning, since large males with thicker upper canines and stronger bite forces would be able to hunt larger prey than females, which is corroborated by feeding ecology in P. leo. Sexual dimorphism indicates that S. fatalis could have been social, but it is unlikely that it lived in fusion-fission units dominated by one or a few males, as in sub-Saharan populations of P. leo. Instead, S. fatalis could have been solitary and polygynous, as most extant felids, or it may have lived in unisexual groups, as is common in P. leo persica.

The Head and Neck Muscles of the Serval and Tiger: Homologies, Evolution, and Proposal of a Mammalian and a Veterinary Muscle Ontology

Here we describe the head and neck muscles of members of the two extant felid subfamilies (Leptailurus serval: Felinae; Panthera tigris: Pantherinae) and compare these muscles with those of other felids, other carnivorans (e.g., domestic dogs), other eutherian mammals (e.g., rats, tree-shrews and modern humans), and noneutherian mammals including monotremes. Another major goal of the article is to discuss and help clarify nomenclatural discrepancies found in the Nomina Anatomica Veterinaria and in veterinary atlases and textbooks that use cats and dogs as models to understand the anatomy of domestic mammals and to stress differences with modern humans. We propose a unifying nomenclature that is expanded to all the head and neck muscles and to all mammalian taxa in order to help build veterinary and mammalian muscle ontologies. Our observations and comparisons and the specific use of this nomenclature point out that felids such as tigers and servals and other carnivorans such as dogs have more facial muscle structures related to the mobility of both the auricular and orbital regions than numerous other mammals, including modern humans, which might be the result of an ancient adaptation related to the remarkable predatory capacities of carnivorans. Interestingly, the skeletal differences, mainly concerning the hyoid apparatus, pharynx, and larynx, that are likely associated with the different types of vocalizations seen in the Felinae (mainly purring) and Pantherinae (mainly roaring) are not accompanied by clear differences in the musculature connected to these structures in the feline L. serval and the pantherine P. tigris.