Morphological patterns in the skulls of cats

Measurements on the skull and dentition of 159 specimens of 22 species of recent felid were analysed using multivariate statistical methods (principal components analysis and correspondence analysis). The resulting patterns were considered in the light of recent work on the systematics of felids (large cats and small cats were clearly differentiated). Within each group there are subgroups. In the small cat group one subgroup was found to consist of the species Lynx lynx, L. rufus, L. pardina, L. canadensis and possibly Felis manul. Another subgroup consisted of the species F. bengalensis, F. rubiginosa, F. planiceps and F. viverrina. These two subgroups agree well with other work on felid systematics. Subgroups which do not agree so well with other work were also found, and the reasons for this are considered. Within the large cats there are two species, F. concolor and Neofelis nebulosa , which are clearly deviant from the norm. The reasons for this deviation are also considered.     

Rapoport effect and biomic specialization in African mammals: revisiting the climatic variability hypothesis

Aim One of the mechanisms proposed to explain the tendency for geographical range size to increase from the equator to the poles, known as the Rapoport effect, is the climatic variability hypothesis. It states that, towards higher latitudes, greater seasonal climatic variability is the most important pressure that selectively promotes greater general climatic tolerance of species, and therefore also more extensive species ranges. In order to test this hypothesis, we explore the influence of climate, area and biome diversity on the latitudinal gradient of climatic specialization. Location The study used the large mammal assemblage from Africa. Methods The degree of climatic specialization of African large mammals (Primates, Carnivora, Proboscidea, Perissodactyla, Hyracoidea, Tubulidentata, Artiodactyla and Pholidota) is investigated using the biomic specialization index (BSI) for each mammal species, based on the number of biomes it inhabits. We studied the influence of 11 climatic and biogeographical predictors in the latitudinal pattern of biomic specialization. Stepwise multiple regressions were used to identify the strongest predictors of biomic specialization in Africa and, separately, in both continental hemispheres. We also studied differences among taxonomical groups (primates, carnivores and artiodactyls). We used correlograms generated using Moran's I coefficients to control for spatial autocorrelation in all these analyses. Results Average BSI values for successive 1°‐latitude bands generally decline towards the equator and temperature variability emerged as the most predictive factor in the regression model for the whole continent, thus supporting the climatic variability hypothesis. Nevertheless, there are differences between hemispheres and among taxa. While temperature variability is the most important predictor of latitudinal variability in biomic specialization in most of the regression models for the northern hemisphere, continental area for each latitudinal band is the best predictor in all the regression models in the southern hemisphere. Main conclusions It appears that similar patterns in latitudinal variation in average BSI may be caused by different factors in the two hemispheres. We suggest that the strong north–south geographical asymmetry of Africa, which influences its biogeographical structure, and the presence of land connections with Eurasia in the northern hemisphere are responsible for the observed patterns. Our data illustrate the influence of continental biogeographical structure and history on macroecological patterns.     

Unique inhibitory cascade pattern of molars in canids contributing to their potential to evolutionary plasticity of diet

Developmental origins that guide the evolution of dental morphology and dental formulae are fundamental subjects in mammalian evolution. In a previous study, a developmental model termed the inhibitory cascade model was established. This model could explain variations in relative molar sizes and loss of the lower third molars, which sometimes reflect diet, in murine rodents and other mammals. Here, I investigated the pattern of relative molar sizes (inhibitory cascade pattern) in canids, a taxon exhibiting a wide range of dietary habits. I found that interspecific variation in canid molars suggests a unique inhibitory cascade pattern that differs from that in murine rodents and other previously reported mammals, and that this variation reflects dietary habits. This unique variability in molars was also observed in individual variation in canid species. According to these observations, canid species have greater variability in the relative sizes of first molars (carnassials), which are functionally important for dietary adaptation in the Carnivora. In conclusion, an inhibitory cascade that differs from that in murine rodents and other mammals may have contributed to diverse dietary patterns and to their parallel evolution in canids.     

A Total Evidence Phylogeny of the Arctoidea (Carnivora: Mammalia): Relationships Among Basal Taxa

A total evidence phylogenetic analysis was performed for 14 extant and 18 fossil caniform genera using a data matrix of 5.6 kbp of concatenated sequence data from six independent loci and 80 morphological characters from the cranium and dentition. Maximum parsimony analysis recovered a single most parsimonious cladogram (MPC). The topology of the extant taxa in the MPC agreed with previous molecular phylogenies. Phylogenetic positions for fossil taxa indicate that several taxa previously described as early members of extant families (e.g., Bathygale and Plesictis) are likely stem taxa at the base of the Arctoidea. Taxa in the “Paleomustelidae” were found to be paraphyletic, but a monophyletic Oligobuninae was recovered within this set of taxa. This clade was closely related to the extant genera Gulo and Martes, therefore, nested within the extant radiation of the family Mustelidae. This analysis provides a resolution to several discrepancies between phylogenies considering either fossil taxa or extant taxa separately, and provides a framework for incorporating fossil and extant taxa into comprehensive combined evidence analyses.     

Interactions within and between clades shaped the diversification of terrestrial carnivores

A longstanding debate in evolutionary biology and paleontology is whether ecological interactions such as competition impose diversity dependence on speciation and extinction rates. Here, we analyze the fossil record of terrestrial mammalian carnivores in North America and Eurasia using a Bayesian framework to assess whether their diversity dynamics were affected by diversity dependence within and between families (12 in Eurasia, 10 in North America). We found eight instances of within‐clade diversity dependence suppressing speciation rates and detected between‐clade effects increasing extinction rates in six instances. Diversity dependence often involved lineages that migrated between continents and we found that speciation was more responsive to diversity changes within the clade, whereas extinction responded to diversity of taxa in other clades. The analysis of the fossil record of Carnivora suggests that interactions within and between clades are associated with different speciation and extinction regimes, opening room for a broader theory of diversity dependence.     

Chew,shake, and tear: Prey processing in Australian sea lions (Neophoca cinerea)

Pinnipeds generally target relatively small prey that can be swallowed whole, yet often include larger prey in their diet. To eat large prey, they must first process it into pieces small enough to swallow. In this study we explored the range of prey‐processing behaviors used by Australian sea lions (Neophoca cinerea) when presented with large prey during captive feeding trials. The most common methods were chewing using the teeth, shaking prey at the surface, and tearing prey held between the teeth and forelimbs. Although pinnipeds do not masticate their food, we found that sea lions used chewing to create weak points in large prey to aid further processing and to prepare secured pieces of prey for swallowing. Shake feeding matches the processing behaviors observed in fur seals, but use of forelimbs for “hold and tear” feeding has not been previously reported for other otariids. When performing this processing method, prey was torn by being stretched between the teeth and forelimbs, where it was secured by being squeezed between the palms of their flippers. These results show that Australian sea lions use a broad repertoire of behaviors for prey processing, which matches the wide range of prey species in their diet.     

Ursavus在中国的首次发现——并记禄丰古猿化石产地的其他熊类标本

本文记述的是1981年在禄丰古猿化石产地发掘中发现的熊类标本,共有二属二种和一种暂不能确定属、种的类型。其中祖熊(Ursavus)过去只见于欧洲、北美和西亚的中新世地层,在我国还是首次发现。禄丰的标本,就其大小和特征可归于Ursavus depereti;印度熊(Indarctos)过去在我国发现过两个种:中国印度熊(I.sinensis)和拉氏印度熊(I.lagrelli),禄丰的标本为前一个种;第三类型与Protursus和Ursus都有相似之处,但又有区别,鉴于材料不足,暂不订属和种。     

河南许昌灵井旧石器遗址哺乳动物群的性质及时代探讨

系统记述了在近两年从河南省许昌市灵井旧石器遗址出土的食肉目、长鼻目和奇蹄目化石:宽吻灵猫相似种(Viverra cf. zibetha)、熊未定种(Ursus sp.)、中国硕鬣狗相似种(Pachycrocuta cf. sinensis)、古菱齿象未定种(Palaeoloxodon sp.)、披毛犀(Coelodonta antiquitatis)、梅氏犀(Dicerorhinus mercki)、普通马(Equusca ballus)和蒙古野驴(Equus hemionus),并对灵井哺乳动物群的性质和年代进行了探讨,指出灵井动物群含有的北方种类较多,与北方区的很多动物群可以比较,属于北方区动物群,其生态环境为以平原草地为主,镶嵌有零散的森林,属北温带半湿润-半干旱大陆性季风气候,年平均温度似低于现在。灵井动物群中绝灭种类占44.4%,其时代应为晚更新世早期,其绝对年龄与许家窑接近,约在100kaBP。     

A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters

Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation nor the way Kolponomos may have captured hard-shelled prey have been tested. Based on mandibular symphyseal morphology shared by Kolponomos and sabre-toothed carnivores, we hypothesize a sabretooth-like mechanism for Kolponomos prey-capture, whereby the mandible functioned as an anchor. Torque generated from jaw closure and head flexion was used to dislodge prey by prying, with prey then crushed using cheek teeth. We test this hypothesized feeding sequence using phylogenetically informed biomechanical simulations and shape analyses, and find a strongly supported, shared high mandibular stiffness in simulated prey-capture bites and mandibular shape in Kolponomos and the sabre-toothed cat Smilodon. These two distantly related taxa converged on using mandibles to anchor cranial torqueing forces when prying substrate-bound prey in the former and sabre-driving forces during prey-killing in the latter. Simulated prey-crushing bites indicate that Kolponomos and sea otters exhibit alternative structural stiffness-bite efficiency combinations in mandibular biomechanical adaptation for shell-crushing. This unique feeding system of Kolponomos exemplifies a mosaic of form-function convergence relative to other Carnivora.