Modern Cats Research Articles

Evolution: Bridging the sabertooth gap(e)

Saber-toothed felids are models of how extreme biomechanical specialization can evolve. A new study reveals a continuous morphological spectrum between sabertooths and modern cats, with specialization acting as a macroevolutionary ratchet.

Catalogue of specimens of Felidae family (Mammalia, Carnivora) specimens deposited in the State Museum of Natural History NASU, Lviv, Ukraine

Currently, modern cats (Felidae) are divided into 8 lineages (phylogenetic lines), which include 14 genera and approximately 40 modern species (Загороднюк та ін., 2022). The cat collection of the State Museum of Natural History NASU, like all vertebrate collections, has a regional character, therefore it is represented by only two species: European wildcat – Felis silvestris Schreber, 1775 and Eurasian lynx – Lynx lynx (Linnaeus, 1758). The collection has been filled since the foundation of the Didushytskyi Museum, the heir of which is a modern museum, that is, from the middle of the 19th century. According to the method of making, the collection consists of stuffed animals (25), skulls (10) and skins (2). It consists of 37 samples (20 of European wildcat and 17 Eurasian lynx). Earlier in the collection there were 13 more samples, which were lost for various reasons or transferred to other collections (5 stuffed Eurasian lynx and European wildcat, and 3 skulls of Eurasian lynx). In the archive of the Museum preserved acts of transfer of exhibits to the Institute of Zoology NASU and Kyiv zoological museum and Uzhhorod University, where among others there are Felidae, however, we failed to find these samples in the mentioned museums. One Eurasian lynx was transferred to the museum of Grodno city (Belarus) in 1924. The oldest exhibit is Eurasian lynx skull, dated of 1857, the youngest – European wildcat skin dated of 2013. The main number of samples, almost 40%, collected from 1880 to 1889. The largest number of exhibits (4) arrived during 1880. All samples collected in the Carpathians and Ciscarpathians (14 – Lvivska oblast, 11 – Ivano-Frankivska oblast, 1 – Ternopilska oblast of Ukraine and 3 – form South-Eastern Poland) and one Eurasian lynx collected in Polissia region. The main ways of income – gifts to the founder of the museum Volodymyr Didushytskyi from his friends and acquaintances, some samples were purchased. Three samples (stuffed Eurasian lynx, stuffed animal and two skulls of a European wildcat) came from the Natural History Museum (disbanded in 1940) of the Shevchenko Scientific Society in Lviv. Scientific analysis of the State Museum of Natural History NASU cat collection was not carried out, indirectly the collection is mentioned in the guidebooks by the museum (Dzieduszycki, 1895; Guidebook, 1957; State, 1982) and K.A. Tatarynov monograph (Татаринов, 1973).

A genomic exploration of the early evolution of extant cats and their sabre-toothed relatives.

BackgroundThe evolutionary relationships of Felidae during their Early–Middle Miocene radiation is contentious. Although the early common ancestors have been subsumed under the grade-group Pseudaelurus, this group is thought to be paraphyletic, including the early ancestors of both modern cats and extinct sabretooths.MethodsHere, we sequenced a draft nuclear genome of Smilodon populator, dated to 13,182 ± 90 cal BP, making this the oldest palaeogenome from South America to date, a region known to be problematic for ancient DNA preservation. We analysed this genome, together with genomes from other extinct and extant cats to investigate their phylogenetic relationships.ResultsWe confirm a deep divergence (~20.65 Ma) within sabretoothed cats. Through the analysis of both simulated and empirical data, we show a lack of gene flow between Smilodon and contemporary Felidae.ConclusionsGiven that some species traditionally assigned to Pseudaelurus originated in the Early Miocene ~20 Ma, this indicates that some species of Pseudaelurus may be younger than the lineages they purportedly gave rise to, further supporting the hypothesis that Pseudaelurus was paraphyletic.

A genomic exploration of the early evolution of extant cats and their sabre-toothed relatives

Background: The evolutionary relationships of Felidae during their Early–Middle Miocene radiation is contentious. Although the early common ancestors have been subsumed under the grade-group Pseudaelurus, this group is thought to be paraphyletic, including the early ancestors of both modern cats and extinct sabretooths. Methods: Here, we sequenced a draft nuclear genome of Smilodon populator, dated to 13,182 ± 90 cal BP, making this the oldest palaeogenome from South America to date, a region known to be problematic for ancient DNA preservation. We analysed this genome, together with genomes from other extinct and extant cats to investigate their phylogenetic relationships. Results: We confirm a deep divergence (~20.65 Ma) within sabre-toothed cats. Through the analysis of both simulated and empirical data, we show a lack of gene flow between Smilodon and contemporary Felidae. Conclusions: Given that some species traditionally assigned to Pseudaelurus originated in the Early Miocene ~20 Ma, this indicates that some species of Pseudaelurus may be younger than the lineages they purportedly gave rise to, further supporting the hypothesis that Pseudaelurus was paraphyletic.

Enhancing mitogenomic phylogeny and resolving the relationships of extinct megafaunal placental mammals

Mitochondrial genomes provided the first widely used sequences that were sufficiently informative to resolve relationships among animals across a wide taxonomic domain, from within species to between phyla. However, mitogenome studies supported several anomalous relationships and fell partly out of favour as sequencing multiple, independent nuclear loci proved to be highly effective. A tendency to blame mitochondrial DNA (mtDNA) has overshadowed efforts to understand and ameliorate underlying model misspecification. Here we find that influential assessments of the infidelity of mitogenome phylogenies have often been overstated, but nevertheless, substitution saturation and compositional non-stationarity substantially mislead reconstruction. We show that RY coding the mtDNA, excluding protein-coding 3rd codon sites, partitioning models based on amino acid hydrophobicity and enhanced taxon sampling improve the accuracy of mitogenomic phylogeny reconstruction for placental mammals, almost to the level of multi-gene nuclear datasets. Indeed, combined analysis of mtDNA with 3-fold longer nuclear sequence data either maintained or improved upon the nuclear support for all generally accepted clades, even those that mtDNA alone did not favour, thus indicating “hidden support”. Confident mtDNA phylogeny reconstruction is especially important for understanding the evolutionary dynamics of mitochondria themselves, and for merging extinct taxa into the tree of life, with ancient DNA often only accessible as mtDNA. Our ancient mtDNA analyses lend confidence to the relationships of three extinct megafaunal taxa: glyptodonts are nested within armadillos, the South American ungulate, Macrauchenia is sister to horses and rhinoceroses, and sabre-toothed and scimitar cats are the monophyletic sister-group of modern cats.

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.

Morphological modularity in the vertebral column of Felidae (Mammalia, Carnivora)

BackgroundPrevious studies have demonstrated that the clear morphological differences among vertebrae across the presacral column are accompanied by heterogeneous functional signals in vertebral shape. Further, several lines of evidence suggest that the mammalian axial skeleton is a highly modular structure. These include its composition of serial units, a trade-off between high shape variance and strong conservation of vertebral count, and direct association of regions with anterior expression sites of Hox genes. Here we investigate the modular organisation of the presacral vertebral column of modern cats (Felidae, Carnivora, Mammalia) with pairwise comparisons of vertebral shape covariation (i.e. integration) and evaluate our results against hypotheses of developmental and functional modularity. We used three-dimensional geometric morphometrics to quantify vertebral shape and then assessed integration between pairs of vertebrae with phylogenetic two-block partial least square analysis (PLS).ResultsSix modules were identified in the pairwise analyses (vertebrae included are designated as ‘C’ for cervical, ‘T’ for thoracic, and ‘L’ for lumbar): an anterior module (C1 to T1); a transitional module situated between the last cervicals and first thoracics (C6 to T2); an anterior to middle thoracic set (T4 to T8); an anticlinal module (T10 and T11); a posterior set composed of the last two thoracics and lumbars (T12 to L7); and a module showing covariation between the cervicals and the posterior set (T12 to L7). These modules reflect shared developmental pathways, ossification timing, and observed ecological shape diversification in living species of felids.ConclusionsWe show here that patterns of shape integration reflect modular organisation of the vertebral column of felids. Whereas this pattern corresponds with hypotheses of developmental and functional regionalisation in the axial skeleton, it does not simply reflect major vertebral regions. This modularity may also have permitted vertebral partitions, specifically in the posterior vertebral column, to be more responsive to selection and achieve higher morphological disparity than other vertebral regions.

Phylogenomic evidence for ancient hybridization in the genomes of living cats (Felidae).

Inter-species hybridization has been recently recognized as potentially common in wild animals, but the extent to which it shapes modern genomes is still poorly understood. Distinguishing historical hybridization events from other processes leading to phylogenetic discordance among different markers requires a well-resolved species tree that considers all modes of inheritance and overcomes systematic problems due to rapid lineage diversification by sampling large genomic character sets. Here, we assessed genome-wide phylogenetic variation across a diverse mammalian family, Felidae (cats). We combined genotypes from a genome-wide SNP array with additional autosomal, X- and Y-linked variants to sample ∼150 kb of nuclear sequence, in addition to complete mitochondrial genomes generated using light-coverage Illumina sequencing. We present the first robust felid time tree that accounts for unique maternal, paternal, and biparental evolutionary histories. Signatures of phylogenetic discordance were abundant in the genomes of modern cats, in many cases indicating hybridization as the most likely cause. Comparison of big cat whole-genome sequences revealed a substantial reduction of X-linked divergence times across several large recombination cold spots, which were highly enriched for signatures of selection-driven post-divergence hybridization between the ancestors of the snow leopard and lion lineages. These results highlight the mosaic origin of modern felid genomes and the influence of sex chromosomes and sex-biased dispersal in post-speciation gene flow. A complete resolution of the tree of life will require comprehensive genomic sampling of biparental and sex-limited genetic variation to identify and control for phylogenetic conflict caused by ancient admixture and sex-biased differences in genomic transmission.

Wild cats and cut marks: Exploitation of Felis silvestris in the Mesolithic of Galgenbühel/Dos de la Forca (South Tyrol, Italy)

The present taphonomic study investigates the role of a small carnivore, Felis silvestris, in the subsistence strategies of Early Mesolithic hunter-gatherers who inhabited the Eastern Alps during the Early Holocene. A reasonable amount of wild cat remains, some bearing cut marks, were recovered during the archaeological excavations of the rock shelter site Galgenbühel/Dos de la Forca, located in South Tyrol (Adige Valley, Bolzano, Italy). The site was frequented from approximately 8500 to 7500 BC cal. by Sauveterrian groups whose economy was centered on the exploitation of nearby wetlands and the forested valley bottom and slopes. The fauna comprises abundant fish remains, molluscs, pond turtles as well as mammals, the latter dominated by the beaver, the wild boar and the red deer. In the reconstruction of hunter-gatherer subsistence strategies, it often thought that carnivores were exploited primarily for their fur. The present taphonomic study was carried out to verify if the exploitation of wild cat by Mesolithic groups was related to the procurement of additional resources. The analysis of the archaeological sample regarding skeletal frequencies and cut-mark distribution was integrated by an experimental work conducted on modern cats in order to reconstruct the chaîne opératoire adopted by man for the treatment of the carcasses. The 3D digital microscope analysis provided for each stria morphometrical parameters in order to identify the origin of cut marks. The anthropic traces found in the wild cat assemblage of Galgenbühel/Dos de la Forca are only partly related to skinning. The localisation and the features of some marks attest disarticulation and therefore support the use of F. silvestris as food.

Convergence and divergence in the evolution of cat skulls: temporal and spatial patterns of morphological diversity.

BackgroundStudies of biological shape evolution are greatly enhanced when framed in a phylogenetic perspective. Inclusion of fossils amplifies the scope of macroevolutionary research, offers a deep-time perspective on tempo and mode of radiations, and elucidates life-trait changes. We explore the evolution of skull shape in felids (cats) through morphometric analyses of linear variables, phylogenetic comparative methods, and a new cladistic study of saber-toothed cats.Methodology/Principal FindingsA new phylogenetic analysis supports the monophyly of saber-toothed cats (Machairodontinae) exclusive of Felinae and some basal felids, but does not support the monophyly of various saber-toothed tribes and genera. We quantified skull shape variation in 34 extant and 18 extinct species using size-adjusted linear variables. These distinguish taxonomic group membership with high accuracy. Patterns of morphospace occupation are consistent with previous analyses, for example, in showing a size gradient along the primary axis of shape variation and a separation between large and small-medium cats. By combining the new phylogeny with a molecular tree of extant Felinae, we built a chronophylomorphospace (a phylogeny superimposed onto a two-dimensional morphospace through time). The evolutionary history of cats was characterized by two major episodes of morphological divergence, one marking the separation between saber-toothed and modern cats, the other marking the split between large and small-medium cats.Conclusions/SignificanceAncestors of large cats in the ‘Panthera’ lineage tend to occupy, at a much later stage, morphospace regions previously occupied by saber-toothed cats. The latter radiated out into new morphospace regions peripheral to those of extant large cats. The separation between large and small-medium cats was marked by considerable morphologically divergent trajectories early in feline evolution. A chronophylomorphospace has wider applications in reconstructing temporal transitions across two-dimensional trait spaces, can be used in ecophenotypical and functional diversity studies, and may reveal novel patterns of morphospace occupation.

Germ Cell Transplantation in Felids: A Potential Approach to Preserving Endangered Species

With the exception of the domestic cat, all members of the family Felidae are considered either endangered or threatened. Although not yet used for this purpose, spermatogonial stem cell (SSC) transplantation has a high potential to preserve the genetic stock of endangered species. However, this technique has not previously been established in felids. Therefore, we developed the necessary procedures to perform syngeneic and xenogeneic SSC transplants (eg, germ cell [GC] depletion in the recipient domestic cats, enrichment and labeling of donor cell suspension, and the transplantation method) in order to investigate the feasibility of the domestic cat as a recipient for the preservation and propagation of male germ plasm from wild felids. In comparison with busulfan treatment, local x-ray fractionated radiation was a more effective approach to depleting endogenous spermatogenesis. The results of both syngeneic and xenogeneic transplants revealed that SSCs were able to successfully colonize and differentiate in the recipient testis, generating elongated spermatids several weeks posttransplantation. Specifically, ocelot spermatozoa were observed in the cat epididymis 13 weeks following transplantation. As donor GCs from domestic cats and ocelots were able to develop and form mature GCs in the recipient environment seminiferous tubules, these findings indicate that the domestic cat is a suitable recipient for SSC transplantation. Moreover, as modern cats descended from a medium-size cat that existed approximately 10 to 11 million years ago, these results strongly suggest that the domestic cat could be potentially used as a recipient for generating and propagating the genome of wild felids.

The Gaping Truth: A New Rationale for the Reconstruction of the Face of Smilodon fatalis

Smilodon fatalis is the best known saber‐toothed cat. It has often been reconstructed by artists and anatomists who presume that this animal closely resembled a modern conical‐toothed felid, with the addition of elongated canine teeth. However, saber‐toothed canines do more than affect the distance to which this animal must gape to clear these teeth to make a bite. Greater gape means that there must be an increased soft tissue mass of lip and mucosa surrounding the oral opening. These tissues would be stretched to their maximum at full gape; however when relaxed, with the mouth closed, or open to less than full gape, these features would still be of greater volume than in conical‐toothed felids. It is likely that the upper lip in Smilodon would show a greater degree of sag than is typical for modern cats. The soft tissues of the nose are not preserved in Smilodon, although past reconstructions assumed that the nasal profile is nearly vertical, as is the case in modern cats. We suggest, instead, that the nasal soft tissues in Smilodon are retracted to a degree commensurate with the retraction of the nasal bones. The lower incisor row of Smilodon is strikingly larger than in comparable‐sized modern Panthera tigris, and would therefore need to be more voluminous to stretch over such teeth It is also likely that the lower lip in Smilodon sagged; perhaps causing this felid to resemble a bloodhound more than a conical‐toothed felid.Grant Funding SourceAmerican Association of Anatomists

Evolution of Skull and Mandible Shape in Cats (Carnivora: Felidae)

The felid family consists of two major subgroups, the sabretoothed and the feline cats, to which all extant species belong, and are the most anatomically derived of all carnivores for predation on large prey with a precision killing bite. There has been much controversy and uncertainty about why the skulls and mandibles of sabretoothed and feline cats evolved to become so anatomically divergent, but previous models have focused on single characters and no unifying hypothesis of evolutionary shape changes has been formulated. Here I show that the shape of the skull and mandible in derived sabrecats occupy entirely different positions within overall morphospace from feline cats, and that the evolution of skull and mandible shape has followed very different paths in the two subgroups. When normalised for body-size differences, evolution of bite forces differ markedly in the two groups, and are much lower in derived sabrecats, and they show a significant relationship with size and cranial shape, whereas no such relationship is present in feline cats. Evolution of skull and mandible shape in modern cats has been governed by the need for uniform powerful biting irrespective of body size, whereas in sabrecats, shape evolution was governed by selective pressures for efficient predation with hypertrophied upper canines at high gape angles, and bite forces were secondary and became progressively weaker during sabrecat evolution. The current study emphasises combinations of new techniques for morphological shape analysis and biomechanical studies to formulate evolutionary hypotheses for difficult groups.

Co-existence of scimitar-toothed cats, lions and hominins in the European Pleistocene. Implications of the post-cranial anatomy of Homotherium latidens (Owen) for comparative palaeoecology

Human occupants of Europe shared food resources with a number of larger Carnivora, and their coexistence with two lion-sized felids, the lion and the scimitar-toothed machairodont Homotherium latidens, poses intriguing paleoecological problems. We investigate the ecology of Homotherium latidens using an exceptional sample of postcrania from the Spanish Early Pleistocene site of Incarcal, making comparisons with modern cats and with other machairodont species. Evidence of cursorial adaptations in Homotherium suggests a hunting technique different from modern cats or smilodontine sabre-tooths. Some, like reduction of the claws, would have limited the ability of individual homotheres to bring down large prey, implying group action. Homotherium would also have been disadvantaged in direct confrontation with Pleistocene lions by smaller body mass, reduced forepaw muscle strength, smaller claws and more fragile dentition. Its hunting technique would have worked best in more open habitats, but competition from lions would have forced it to seek moderate cover. Among factors that could de-stabilise coexistence of the two big cat species in Pleistocene Europe we invoke a decrease in environmental mosaicism associated with stepped climatic change over the last million years, and the increased importance of humans within the larger predator guild.

Cementum onSmilodon sabers

The maxillary canines of Smilodon californicus Bovard, 1907 have a deeply curved cementoenamel junction. The gingiva of modern cats is attached to the tooth at the cementoenamel junction and provides tactile and other dental information to the animal. The presence of cementum at the cervix of the maxillary canines, also called sabers, would indicate that the gingiva in Smilodon was attached in this region. Such an attachment would be advantageous, providing stability and sensory input for the large tooth. Also, gingiva at the cervix would impact the manner in which the teeth were used. Previous study using scanning electron microscopy of dental casts was indirect. The purpose of this study was to confirm by direct methods the presence of cementum at the cervix of Smilodon californicus sabers. Parts of three Smilodon californicus sabers were sectioned and examined with light and scanning electron microscopy (EDS). In addition, percent weight of calcium and phosphorus was measured in enamel, dentin, and cementum using electron dispersive spectroscopy. Cementum was identified in the cervical region of each saber. Spectroscopy confirmed that the tissue is calcified and the mineral is hydroxyapatite. Percent calcium and percent phosphorus of individual tissues were highly variable between specimens. However, the ratios of calcium to phosphorus were not significantly different from the hydroxyapatite standard. In the future, bite models will have to take the presence of soft tissues into account.

Patterns of Y and X Chromosome DNA Sequence Divergence During the Felidae Radiation

The 37 species of modern cats have evolved from approximately eight phylogenetic lineages within the past 10 to 15 million years. The Felidae family has been described with multiple measures of morphologic and molecular evolutionary methods that serve as a framework for tracking gene divergence during brief evolutionary periods. In this report, we compare the mode and tempo of evolution of noncoding sequences of a large intron within Zfy (783 bp) and Zfx (854 bp), homologous genes located on the felid Y and X chromosomes, respectively. Zfy sequence variation evolves at about twice the rate of Zfx, and both gene intron sequences track feline hierarchical topologies accurately. As homoplasies are infrequent in patterns of nucleotide substitution, the Y chromosome sequence displays a remarkable degree of phylogenetic consistency among cat species and provides a highly informative glimpse of divergence of sex chromosome sequences in Felidae.

Development and eruption sequence of deciduous and permanent teeth in the saber-tooth catHomotherium serumCope

ABSTRACT A sample population from Friesenhahn Cave, Bexar County, Texas, is used to describe the juvenile dentition of Homotherium serum. Analysis of thirteen juvenile dentitions of Homotherium serum Cope results in identification of eight stages in the eruption of deciduous and permanent teeth. These stages permit a direct comparison between Homotherium and modern felid dentitions. The eight stages progressively describe the teeth in terms of eruption and replacement, position, cusp patterns, and degree of wear. Comparisons are made between deciduous and permanent teeth of Homotherium serum to aid in future identifications and to suggest a functional significance. The deciduous dentitions of Homotherium serum and Smilodon floridanus are compared and contrasted. The bimodal age distribution of Homotherium serum is used to suggest that Friesenhahn Cave was a denning cave. Data on the eruption sequences of four modern cats are summarized and compared with Homotherium serum to propose a time-table for the eruption of Homotherium dentition.