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On the morphology of the astragalus and calcaneus of the amphicyonids (Carnivora, Mammalia) from the Paleogene of Europe: implications for the ecology of the European bear-dogs
Abstract
The Paleogene mammals of Europe are rarely known from partial or complete skeletons. As a result, their systematics and ecology are often solely based on dental characters and postcranial remains, when available, are usually neglected. This explains why the locomotion of mammals of the Eocene-Oligocene transition, the “Grande Coupure”, is poorly known. The aim of this study is to describe the tarsal bones (astragali and calcanei) and characterize the locomotion of amphicyonid carnivorans, one of the most abundant mammalian predator groups from the Phosphorites du Quercy (France) sites. The identification of taxa and the characterization of both posture and locomotion were carried out using four criteria: relative abundance (in comparison with dental data), morphology, size, and body mass. Seven morphotypes, four among astragali and three among calcanei, are identified as Amphicyonidae and show various postures: plantigrade, semi-digitigrade, and digitigrade. One morphotype of the astragalus and one of the calcaneus are identified as Cynodictis lacustrisGervais, 1852, which exhibits a digitigrade posture. The study of postcranial bones, such as tarsals, allows for a better understanding of the ecology of these animals and deserves more interest in future morphological and phylogenetic studies.
... Hunt (2009:71) thought what he termed the longlegged North American Early Miocene amphicyonids, such as Daphoenodon superbus (Peterson, 1910), were evolved from a form close to Daphoenus vetus. Fournier et al. (2020) recently described the astragalus and calcaneus of early amphicyonids from Quercy fissure deposits in southern France. Although most isolated ankle bones are not attributable to specific taxa, one was identified as belonging to Cynodictis lacustris that has a digitigrade posture. ...
... These early ursids from the Early Miocene have already achieved the body size of a coyote or a small modern wolf and are considerably more derived than the earlier Eoarctos. Most recently, Fournier et al. (2020) identified one amphicyonid, Cynodictis lacustris from Quercy phosphorites in southern France, as having a digitigrade posture based on its ankle bone morphology. Four other amphicyonids that are not attributable to specific taxa, however, appear to be mostly plantigrade. ...
An exquisitely preserved male skeleton of an early arctoid, Eoarctos vorax new genus and species, provides a unique window into the origin and early divergence of Carnivora. Recovered from the Fitterer Ranch locality in the early Oligocene (Orellan to Whitneyan North American Land Mammal ages) Brule Formation of southwestern North Dakota (~32 Ma), the new arctoid offers an opportunity to evaluate the fundamental relationships of the caniform (dog-like) carnivorans. Eoarctos vorax possesses a suite of plesiomorphic characters inherited from its miacid ancestors, making it an ideal model for ancestral arctoids. We present a comprehensive treatment of E. vorax, combining traditional description with photographic documentation, modern microCT, laser scans, and photogrammetry.Showing its plesiomorphic morphology, Eoarctos vorax is scansorial in locomotion, somewhat like a modern raccoon, retaining the ability to climb trees and lacking cursorial adaptations present in the early canid Hesperocyon. However, E. vorax shows clear signs of durophagous cranio-dental adaptations, presumably for an obligatory diet of mollusks, and frequent damage to shell-crushing premolars, plus associated dental infections.We review several other key North American early arctoids and present total-evidence (nuclear DNA and discrete morphological characters) Bayesian and parsimony analyses of Caniformia phylogeny, including extinct stem taxa plus a living member of all modern families. We recognize an endemic North American ursoid clade, family Subparictidae, which includes Eoarctos vorax as its most derived member. We demonstrate the importance of North America as an early cradle of evolution for caniform carnivorans, including early precursors of Canidae, Amphicyonidae, Ursidae, and Pinnipedia.
... The morphology of ankle bones, including the astragalus, has made possible the study of mammalian locomotion [13]. The shape of ankle bones is associated with locomotion and habitat use in ungulates [14,15], carnivores [16][17][18] and primates [19,20]. Numerous studies have also been undertaken in rodents, providing insights into the locomotory ecology of numerous clades through space and time [21][22][23][24][25][26][27]. ...
The North American rodent fossil record includes hundreds of species representing both an incredible taxonomic diversity and great ecological disparity. Although it is during the Oligocene that taxonomic diversity first peaks, it is not until the Miocene, almost 10 Myr later, that many ecologies, particularly locomotory ecologies, are recorded. Here, I present a new Oligocene-aged species of beaver from Montana, Microtheriomys articulaquaticus sp. nov., which represents the oldest semi-aquatic rodent in North America and the oldest amphibious beaver in the world, pushing the advent of semi-aquatic ecology in beavers by 7 Myr. I also provide morphological data supporting a terrestrial ecology for the sister taxon to Castoridae. Together with existing data, these findings lead to a new hypothesis for the evolutionary ecology of castorids whereby swimming was exapted from burrowing during the Oligocene. This evolution of semi-aquatic locomotion may have taken place in North America instead of Eurasia. It started in small beavers with gigantism achieved only much later. Indeed, body size evolution in castoroids follows a directional drift. Beavers obey Cope's rule, a selection for larger size over time that appears associated with semi-aquatic ecology and may well explain their low modern diversity.
... Fewer scansorial mammals (Gliridae + Nyctitheriidae) than semiterrestrial mammals (Theridomyidae + Herpetotheriidae) were predated in both levels, but the difference is greater in TB33 than in O3 (Table 7). This is counterintuitive, given that some evidence suggests that Paramiacis had better climbing abilities than Cynodictis, which is shown to have been terrestrial (Fournier et al., 2020). There are fewer bite marks attributable to Paramiacis on bones from TB33 than to Cynodictis from O3. ...
... In turn, determining postcranial bones is crucial because it can provide data on the locomotion and ecology of Paleogene mammals, which are generally poorly known. For instance, based on the tarsal bones from the Quercy Phosphorites housed in Belgian collections and in the MNHN, Fournier et al. (2020) reconstructed the locomotion (i.e., arboreal, terrestrial) and the posture (i.e., plantigrade, semi-digitigrade, digitigrade) of selected European amphicyonids. Moreover, having data on the locomotion of the extinct mammals adds another layer of information to the reconstruction of the paleoenvironments and their evolution through time and space. ...
The Quercy Phosphorites Formation in France is world famous for its Eocene to Miocene faunas, especially those from the upper Eocene to lower Oligocene, the richest of all. The latter particularly helped to understand the ‘Grande Coupure’, a dramatic faunal turnover event that occurred in Europe during the Eocene-Oligocene transition. Fossils from the Quercy Phosphorites were excavated from the middle 19th century until the early 20th century in a series of sites and became subsequently dispersed over several research institutions, while often losing the temporal and geographical information in the process. In this contribution, we provide an overview and reassess the taxonomy of these barely known collections housed in three Belgian institutions: the Université de Liège, KU Leuven, and the Royal Belgian Institute of Natural Sciences. We focus our efforts on the carnivorous mammals (Hyaenodonta and Carnivoramorpha) and assess the stratigraphic intervals covered by each collection. These fossils are derived from upper Eocene (Priabonian), lower Oligocene (Rupelian), and upper Oligocene (Chattian) deposits in the Quercy area. The richness of the three collections (e.g., the presence of numerous postcranial elements in the Liège collection), the presence of types and figured specimens in the Leuven collection, and some identified localities in the RBINS collection make these collections of great interest for further studies on systematics and the evolution of mammals around the ‘Grande Coupure’.
... Study of a perfectly preserved cranium and mandible of one of these migrants demonstrated that they belonged to a genus known from Europe, but to a new species (Hunt & Yatkola 2020, 'A new species of the amphicyonid carnivore Cynelos Jourdan, 1862 from the early Miocene of North America'). A final article focuses on this family (Fournier et al. 2020) through the analysis of ankle bones. Moving from bear-dogs to true bears, the early ancestors of the living giant panda were present in Europe in the Miocene and the last of them is known from Spain (Abella et al. 2019, 'The last record of an ailuropod bear from the Iberian Peninsula'). ...
Using finite element analysis on the astragali of five macropodine kangaroos (extant and extinct hoppers) and three sthenurine kangaroos (extinct proposed bipedal striders) we investigate how the stresses experienced by the ankle in similarly sized kangaroos of different hypothesized/known locomotor strategy compare under different simulation scenarios, intended to represent the moment of midstance at different gaits. These tests showed a clear difference between the performance of sthenurines and macropodines with the former group experiencing lower stress in simulated bipedal strides in all species compared with hopping simulations, supporting the hypothesis that sthenurines may have utilized this gait. The Pleistocene macropodine Protemnodon also performed differently from all other species studied, showing high stresses in all simulations except for bounding. This may support the hypothesis of Protemnodon being a quadrupedal bounder.
The paleontological collection from Geographical Society Cave located in southern part of Primorskii Territory is found to comprise 5 species of ursids and mustelids: Ursus arctos, Meles anakuma, Martes zibellina, Gulo gulo and Lutra lutra. Bone remains of brown bear (Ursus arctos) predominate; scant tooth-marks of large carnivores on their surfaces suggest bears to have been only occasional prey, dying mainly when overwintering in the cave. The presence of Asian badger (Meles anakuma) and true otter (Lutra lutra), whose findings are not known northwardly, provide the possibility to regard southern regions of the Russian Far East as a refuge, where these species survived during the Late Pleistocene.
The Quercy Phosphorites Formation in France is world famous for its Eocene to Miocene faunas, especially those from the upper Eocene to lower Oligocene, the richest of all. The latter particularly helped to understand the ‘Grande Coupure’, a dramatic faunal turnover event that occurred in Europe during the Eocene-Oligocene transition. Fossils from the Quercy Phosphorites were excavated from the middle 19th century until the early 20th century in a series of sites and became subsequently dispersed over several research institutions, while often losing the temporal and geographical information in the process. In this contribution, we provide an overview and reassess the taxonomy of these barely known collections housed in three Belgian institutions: the Université de Liège, KU Leuven, and the Royal Belgian Institute of Natural Sciences. We focus our efforts on the carnivorous mammals (Hyaenodonta and Carnivoramorpha) and assess the stratigraphic intervals covered by each collection. These fossils are derived from upper Eocene (Priabonian), lower Oligocene (Rupelian), and upper Oligocene (Chattian) deposits in the Quercy area. The richness of the three collections (e.g., the presence of numerous postcranial elements in the Liège collection), the presence of types and figured specimens in the Leuven collection, and some identified localities in the RBINS collection make these collections of great interest for further studies on systematics and the evolution of mammals around the ‘Grande Coupure’.
Background: Ecometric patterning is the sorting of mean values of functional traits in communities in space through time at continental scales. Ecometric patterns can emerge from intraspecific population-level processes (selection along an environmental gradient), species-level processes (geographic sorting of species based on functional trait differences), or clade-level processes (geographic sorting based on phylogenetically shared traits). We analysed a hind limb ratio related to locomotion in carnivores (Mammalia, Carnivora) to determine (1) whether its ecometric patterning involves intraspecific population-level evolutionary processes; (2) whether ecometric patterning is produced by clade sorting processes; and (3) how ecometric patterns are altered by species turnover during glacial–interglacial cycles. Data: We analysed (1) intraspecific variation in hind limb ratio in five species to evaluate the importance of population-level processes in ecometric patterning; (2) the distributions of ratios within and among communities to evaluate the importance of clade sorting; and (3) the distributions of ratios of seven glacial fossil assemblages to evaluate temporal dynamics in ecometric patterns. We also analysed three-dimensional calcaneum shape to assess the strength of phylogenetic and functional components of hind limb variation. Analytical methods: Geometric morphometrics, phylogenetic comparative methods, and phylogenetic community assembly methods were used to evaluate trait-based clade sorting; RLQ analysis was used to measure the correlation between vegetation openness, spatial scale, species occurrences, phylogeny, and hind limb traits; and trait space was used to analyse turnover between glacial and extant carnivore communities. Results: Population-level selection is either too weak or ineffective to produce hind limb trait gradients within carnivore species; however, clade-level trait-based sorting has a strong impact on community-level trait distributions. RLQ analysis demonstrates that clade membership interacts with hind limb ratios and vegetation openness in carnivore community assembly. Glacial–interglacial cycles produced turnover in faunas and hind limb trait distributions regardless of location or biome.
The Middle to Late Eocene sediments of Texas have yielded a wealth of fossil material that offers a rare window on a diverse and highly endemic mammalian fauna from that time in the southern part of North America. These faunal data are particularly significant because the narrative of mammalian evolution in the Paleogene of North America has traditionally been dominated by taxa that are known from higher latitudes, primarily in the Rocky Mountain and northern Great Plains regions. Here we report on the affinities of two peculiar carnivoraforms from the Chambers Tuff of Trans-Pecos, Texas, that were first described 30 years ago as Miacis cognitus and M. australis. Re-examination of previously described specimens and their inclusion in a cladistic analysis revealed the two taxa to be diminutive basal amphicyonids; as such, they are assigned to new genera Gustafsonia and Angelarctocyon, respectively. These two taxa fill in some of the morphological gaps between the earliest-known amphicyonid genus, Daphoenus, and other Middle-Eocene carnivoraforms,
and lend additional support for a basal caniform position of the beardogs outside the Canoidea. The amphicyonid lineage had evidently given rise to at least five rather distinct forms by the end of the Middle Eocene. Their precise geographical origin remains uncertain, but it is plausible that southern North America served as an important stage for a very early phase of amphicyonid radiation.
The Early Miocene Napak XV locality (ca 20.5 Ma), Uganda, has yielded an interesting assemblage of fossils, including the very well represented amphicyonid Hecubides euryodon. The remarkable find of a nearly complete mandible, unfortunately with poorly preserved dentition, together with new dental remains allow us to obtain a better idea about the morphology and variability of this species. Additionally, we describe a newly discovered mandible of Hecubides euryodon from the Grillental-VI locality (Sperrgebiet, Namibia), which is the most complete and diagnostic Amphicyonidae material found in this area. Comparisons with Cynelos lemanensis from Saint-Gérand-le-Puy (France), the type locality, and with an updated sample of the species of amphicyonids described in Africa leads us to validate the genus Hecubides. Hecubides would be phylogenetically related to the medium and large size species of Amphicyonidae from Africa, most of them now grouped into the genera Afrocyon and Myacyon, both endemic to this continent.
The Nimravidae is a family of extinct carnivores commonly referred to as “false saber-tooth cats.” Since their initial discovery, they have prompted difficulty in taxonomic assignments and number of valid species. Past revisions have only examined a handful of genera, while recent advances in cladistic and morphometric analyses have granted us additional avenues to answering questions regarding our understanding of valid nimravid taxa and their phylogenetic relationships. To resolve issues of specific validity, the phylogenetic species concept (PSC) was utilized to maintain consistency in diagnosing valid species, while simultaneously employing character and linear morphometric analyses for confirming the validity of taxa. Determined valid species and taxonomically informative characters were then employed in two differential cladistic analyses to create competing hypotheses of interspecific relationships. The results suggest the validity of twelve species and six monophyletic genera. The first in depth reviews of
Pogonodon
and
Dinictis
returned two valid species (
P. platycopis
,
P. davisi
) for the former, while only one for the latter (
D. felina
). The taxonomic validity of
Nanosmilus
is upheld. Two main clades with substantial support were returned for all cladistic analyses, the Hoplophoneini and Nimravini, with ambiguous positions relative to these main clades for the European taxa:
Eofelis
,
Dinailurictis bonali
, and
Quercylurus major
; and the North American taxa
Dinictis
and
Pogonodon
.
Eusmilus
is determined to represent a non-valid genus for North American taxa, suggesting non-validity for Old World nimravid species as well. Finally,
Hoplophoneus mentalis
is found to be a junior synonym of
Hoplophoneus primaevus
, while the validity of
Hoplophoneus oharrai
is reinstated.
Hyaenodontidae is a diverse component of the carnivorous guild in early Eocene (Wasatchian) North American mammalian faunas. Although there have been suggestions that early members of the family had diverse locomotor repertoires, few Wasatchian postcrania are adequately described. Here we describe the first known postcranial remains of the rare Wasatchian hyaenodontid Galecyon, based principally on a well-preserved partial skeleton from the Willwood Formation, Wyoming. Galecyon is reconstructed as a 5.2-7.9 kg terrestrial carnivore. Small but significant differences throughout the skeleton distinguish Galecyon from Prolimnocyon. Galecyon is reconstructed as scansorial/generalized terrestrial because these postcranial differences consistently indicate a more terrestrial habit than in the scansorial Prolimnocyon. Among other hyaenodontids, Arfia shows evidence for parallel terrestrial adaptation, whereas Pyrocyon is morphologically intermediate between Galecyon and Prolimnocyon. Manipulation of the well-preserved bones forming the crurotarsal joint of Galecyon provides evidence that contradicts a previous proposal that Arfia, another Wasatchian hyaenodontid, was capable of hind foot reversal. In both genera, movements at the crurotarsal joint were largely restricted to a parasagittal plane. Phylogenetic analysis of a new postcranial character set supports a pattern of relationships for early Eocene hyaenodontids different from that supported by dental morphology. Combining the two data partitions favors most aspects of the dental topology, but the conflict between dental and postcranial data indicates that confident phylogenetic resolution can be elusive, even with relatively dense sampling.
We describe a new large-sized species of hypercarnivorous hyainailourine-Kerberos langebadreae gen. & sp. nov.-from the Bartonian (MP16) locality of Montespieu (Tarn, France). These specimens consist of a skull, two hemimandibles and several hind limb elements (fibula, astragalus, calcaneum, metatarsals, and phalanges). Size estimates suggest K. langebadreae may have weighed up to 140 kg, revealing this species as the largest carnivorous mammal in Europe at that time. Besides its very large size, K. langebadreae possesses an interesting combination of primitive and derived features. The distinctive skull morphology of K. langebadreae reflects a powerful bite force. The postcranial elements, which are rarely associated with hyainailourine specimens, indicate an animal capable of a plantigrade stance and adapted for terrestrial locomotion. We performed the first phylogenetic analysis of hyainailourines to determine the systematic position of K. langebadreae and to understand the evolution of the group that includes other massive carnivores. The analysis demonstrates that Hemipsalodon, a North American taxon, is a hyainailourine and is closely related to European Paroxyaena. Based on this analysis we hypothesize the biogeographic history of the Hyainailourinae. The group appeared in Africa with a first migration to Europe during the Bartonian that likely included the ancestors of Kerberos, Paroxyaena and Hemipsalodon, which further dispersed into North America at this time. We propose that the hyainailourines dispersed into Europe also during the Priabonian. These migrants have no ecological equivalent in Europe during these intervals and likely did not conflict with the endemic hyaenodont proviverrines. The discovery of K. langebadreae shows that large body size appears early in the evolution of hyainailourines. Surprisingly, the late Miocene Hyainailouros shares a more recent common ancestor with small-bodied hyainailourines (below 15 kg). Finally, our study supports a close relationship between the Hyainailourinae and Apterodontinae and we propose the new clade: Hyainailouridae.
New remains of the early Eocene hyaenodontid Indohyaenodon raoi are described from the Vastan Lignite Mine in Gujarat, western India, including the first known rostrum, upper dentition, and postcrania, substantially expanding our knowledge of the species and providing insights into its functional morphology and relationships. Craniodental morphology suggests that I. raoi had a broad diet, including non-vertebrate material as well as flesh of a diversity of prey species. Postcranial morphology is broadly similar to that of other early hyaenodontids and suggests a scansorial locomotor repertoire. Dental morphology indicates that I. raoi is closely related to other South Asian hyaenodontids, with shared features including strong cingula, narrow premolars, and a reduced P4 protocone. We present the most comprehensive phylogenetic analysis of Hyaenodontidae to date, which corroborates this relationship but finds South Asian hyaenodontids to be the stem of a group that includes most African hyaenodontids. This and other higher-level relationships within Hyaenodontidae are, however, weakly supported, and substantially different alternative hypotheses of relationships are not significantly less parsimonious, reflecting strong character conflict. Factors contributing to this conflict include the isolation of hyaenodontid faunas on different continents during much of the Eocene, canalization and simplification of carnivorous dentitions, and a lack of non-dental material for critical hyaenodontid groups. The new phylogeny is consistent with either an African or an Asian origin for the group.
The genus Adelpharctos was known until now through the species A. mirus by a unique mandible (p2-m2) from the old collections of the Quercy whose geological age was unknown. New material coming from the locality of Pech-du-Fraysse completes our knowledge of the genus particularly for the maxilla and upper teeth. Adelpharctos belongs to the sub-family Hemicyoninae in the family Ursidae. It differs from the middle Miocene hemicyonines which have more massive molars and from the group Cephalogale-Phoberogale by some morphological characters. It seems to be a branch coming from the ancestral stem group of the sub-family.
The most primitive canid Hesperocyon from the late Eocene to early Oligocene (Duchesnean to Whitneyan) of North America possesses a combination of both cursorial and noncursoiial limb characteristics. Compared to 'the archaic miacoid carnivorans, Hesperocyon has a number of advanced features suggestive of running adaptations, such as absence of a large teres major process on the scapula, a relatively reduced deltoid crest on .the humerus, elongated and adjoined metapodials, and laterally oriented fovea capitis femoris. On the other hand, Hesperocyon retains some primitive , arboreal characteristics such as a short, broad scapula with long acromion, a stout humerus with a deep bicipital groove and a thin-bladed bra-chioradialis crest, an anteriorly bowed ulna, a sharply angled pelvic floor, a relatively large muscle scar for flexor digitorum longus and caudal tibialis on the tibia, and a short, deep, and hooked distal phalanx suggestive of a retractile claw. This combination of cursorial and noncursorial characters shows that Hesperocyon represents a transitional stage from its arboreal plantigrade ancestors to its cursorial digitigrade descendants. Examination of a series of miacoids and primitive canids (Vulpavus, Miacis, Hesperocyon, Cormo-cyon, Leptocyon, and Tomarctus) reveals that the canid metatarsus did not become erect until the Arikareean Cormocyon and Leptocyon. Increased extension angle of the tibioastragalar joint was achieved through realignment of the plantar tendon groove to be continuous with the astragalar trochlea and elimination of the astragalar foramen. By combining anatomical characters with results of a morphometric analysis, I have concluded that Hesperocyon was plantigrade in posture and probably scansorial in life.
Mammal teeth bring important information regarding phylogeny and diet. However, postcranial elements, although poorly studied for small Paleogene mammals, can provide other significant data. The purpose of this study is to associate tarsal bones with dental specimens for a systematic identification. We thus chose the Belgian locality of Dormaal (Tienen Formation, Belgium) that has yielded the earliest Eocene mammals of Europe. This particularly rich fauna, dated between 55.5 and 55.8 Ma, occurred during the Paleocene-Eocene Thermal Maximum, a key period in the mammal evolution. It is composed by archaic mammals (“condylarths”, arctocyonids, plesiadapiforms, “insectivorans”…) and also by earliest modern taxa (primates, rodents, carnivoraforms, artiodactyls …), representing about 14,000 dental specimens. 488 tarsal bones are studied according to three methods: morphology, relative abundance and relative size. 12 morphotypes of astragali and 18 of calcanei are discriminated and most of them are identified at the level of species (e.g. the marsupial Peratherium constans), genus or family (e.g. ischyromyid rodents). New perspectives in phylogeny and paleoecology are proposed for further studies implying tarsal bones.
We describe six proviverrine species from the Early Eocene of France. Three species are new: Minimovellentodon russelli sp. nov. from Mutigny [mammal palaeogene (MP)8 + 9], Boritia duffaudi sp. nov. from La Borie (MP8 + 9), and Leonhardtina godinoti sp. nov. from Grauves (MP10). We describe new specimens and propose new generic combinations for three species from MP10: Protoproviverra palaeonictides, Matthodon menui, and Oxyaenoides lindgreni. We also propose a new generic combination for the primitive Eoproviverra eisenmanni (MP7). Matthodon menui was previously considered as a possible oxyaenodontan, but the new fossils clearly support its reference to Hyaenodontida. Leonhardtina godinoti and Ma. menui are the oldest occurrences for these genera, which were previously unknown before the Middle Eocene. Moreover, the discovery of the proviverrine Mi. russelli in Mutigny implies that the Proviverrinae dispersed in Northern Europe between biozone Palaeocene-Eocene (PE) III (Abbey Wood) and biozone PE IV (Mutigny). This also supports a homogenization of the European faunas during the Early Eocene. The dispersal is concomitant with the disappearance of the oxyaenodontans, arfiines, and sinopines (Hyaenodontida) from Europe. The proviverrines may have filled the ecological niches left vacant by the disappearance of the other carnivorous mammals. With 20 genera and over 30 species, proviverrines were successful in Europe. We performed the first phylogenetic analysis comprising almost all the Proviverrinae. Our analyses indicate that the Proviverrinae diversified greatly during the Early Eocene Climatic Optimum and show a general trend towards specialization throughout the Eocene. © 2014 The Linnean Society of London
The discovery of new remains assigned to Stenoplesictis (Feliformia, Carnivora) in the deposit of Quercy (France) allows a more precise study of this genus. S. cayluxi Filhol, 1880 and S. minor Filhol, 1882, two species previously described by Filhol, are synonymized. A new species, Stenoplesictis crocheti, is described. It is represented by dental remains and two well preserved skulls. The basicranial anatomy is studied with special focus on the auditory region. Stenoplesictis may be a primitive feloid, like the extant Nandinia binotata. Some other material recently assigned to the genus is discussed. The African and Asian material differs from the European specimens, especially the morphology of the teeth and is excluded from the genus. Therefore, an Asian origin of the genus can not be demonstrated and the presence of Stenoplesictis in Asia remains to be confirmed.
During the transition from the Eocene to the Oligocene epochs, the mild tropical climates of the Paleocene and early Eocene were replaced by modern climatic conditions and extremes, including glacial ice in Antarctica. The best terrestrial record of the Eocene-Oligocene transition is found in North America, including the spectacular cliffs and spires of the Big Badlands National Park, in South Dakota. The first part of this book summarises the latest information in dating and correlation of the strata of late middle Eocene through early Oligocene age in North America, including the latest insights from argon/argon dating and magnetic stratigraphy. The second part reviews almost all the important terrestrial reptiles and mammals found near the Eocene-Oligocene boundary in the White River chronofauna, from the turtles, snakes and lizards to the common rodents, carnivores, artiodactyls, and perissodactyls. This is the first comprehensive treatment of these rocks and fossils in over sixty years and will be an invaluable resource to vertebrate palaeontologists, geologists, mammalogists and evolutionary biologists.
Locomotor mode is an important component of an animal's ecology, relating to both habitat and substrate choice (e.g., arboreal versus terrestrial) and in the case of carnivores, to mode of predation (e.g., ambush versus pursuit). Here, we examine how the morphology of the calcaneum, the 'heel bone' in the tarsus, correlates with locomotion in extant carnivores. Other studies have confirmed the correlation of calcaneal morphology with locomotion behaviour and habitat. The robust nature of the calcaneum means that it is frequently preserved in the fossil record. Here, we employ linear measurements and 2D-geometric morphometrics on a sample of calcanea from eighty-seven extant carnivorans and demonstrate a signal of correlation between calcaneal morphology and locomotor mode that overrides phylogeny. We used this correlation to determine the locomotor mode, and hence aspects of the palaeobiology of, 47 extinct carnivorous mammal taxa, including both Carnivora and Creodonta. We found ursids (bears), clustered together, separate from the other carnivorans. Our results support greater locomotor diversity for nimravids (the extinct 'false sabertooths', usually considered to be more arboreal), than previously expected. However, there are limitations to interpretation of extinct taxa because their robust morphology is not fully captured in the range of modern carnivoran morphology.
Fossil material from 90 fossil localities, mostly paleokarstic, has been gathered together to study western European bat evolution and diversity from the middle Eocene (~44 Ma) to the early late Oligocene (~29 Ma). The morphological and biometric observations and comparisons of the tooth material allow recognition of 7 families, 10 genera and 57 species; amongst the latter, 45 are described in detail here together with 11 subspecies. Several taxa of various systematic ranks are described as new: 1 subgenus and 17 species including 6 new subspecies; 1 new family and 2 new genera were described in a previously published paper but originate from this large review. From these new results, and the long period covered (more than 10 Ma), this work suggests a number of phyletic hypotheses. Amongst others, the relationship between the new fossil family Mixopterygidae and the fossil and extant families Emballonuridae and Hipposideridae is discussed. The peculiar Necromantis fossil genus being now better documented, its particular inferior molar pattern is exemplified as defining the necromantodont pattern. Even though the affinities of Necromantis remain unclear, the new data indicate that the previous assignment to Megadermatidae was incorrect. Thanks to the available information from the bat material, the relative dating of yet unstudied and undated new localities is proposed from biochronal reference stages, characterized by some bat species with a given size and morphology. Also, further data are given for faunas dated by the numerical ages method. The comparison of fossil and modern bat cenograms suggests that the body weight composition of a community is linked to the nature of the environment in which it evolves. Finally, these analyses allow deducing some possible bat evolutionary modalities either by the variations in the represented weight range or by the proportion of the different weight categories. They indicate that extinctions preferentially affected “extreme species” from a morphological point of view, as well as in terms of body mass. Consequently, this allows discussion of the effect of Stehlin’s faunal Grande Coupure faunal event amongst western European bats at the Eocene–Oligocene boundary.
The impact of environment, interspecific competition, and, to a lesser extent history, on the structure of the guild of large predatory mammals is explored in one fossil and four Recent communities. Two aspects are emphasized: (1) the number of species within each guild and (2) the extent of locomotor convergence as inferred from morphology among the constituent species. Locomotor behavior reflects habitat choice, hunting mode, and escape strategy, all of which appear to be important avenues of adaptive divergence among coexisting predators.
Locomotor behavior in extinct and extant predators is determined from body weight and five measured characteristics of the postcranial skeleton, including ungual shape, elbow shape, and limb proportions. Results indicate that levels of morphologic and inferred ecologic similarity between large predators are higher in the tropical grassland guild of East Africa than in the equivalent guilds of either tropical or temperate forest. This may be due to the great density and diversity of terrestrial herbivores in the productive grasslands. The fossil guild, from the Late Chadron–Orellan (Oligocene) of North America, appears most similar to the tropical forest guilds, but the predators seem to have been slower and more robust than their modern counterparts. Since the Orellan represents an early stage in the evolution of large, fissiped carnivores, both ancestry and time could have influenced Orellan guild structure.
Members of the mammalian clade Carnivora have invaded nearly every continent and ocean, evolving into bamboo-eating pandas, clam-eating walruses and of course, flesh-eating sabre-toothed cats. With this ecological, morphological and taxonomic diversity and a fossil record spanning over sixty million years, Carnivora has proven to be a model clade for addressing questions of broad evolutionary significance. This volume brings together top international scientists with contributions that focus on current advances in our understanding of carnivoran relationships, ecomorphology and macroevolutionary patterns. Topics range from the palaeoecology of the earliest fossil carnivorans to the influences of competition and constraint on diversity and biogeographic distributions. Several studies address ecomorphological convergences among carnivorans and other mammals with morphometric and Finite Element analyses, while others consider how new molecular and palaeontological data have changed our understanding of carnivoran phylogeny. Combined, these studies also illustrate the diverse suite of approaches and questions in evolutionary biology and palaeontology.
North American amphicyonid carnivorans are prominent members of the mid-Cenozoic terrestrial carnivore community during the late Eocene to late Miocene (Duchesnean to Clarendonian). Species range in size from <5 kg to >200 kg. Among the largest amphicyonids are Old and New World species of the genus Amphicyon: A. giganteus in Europe (18-∼15? Ma) and Africa, A. ingens in North America (15.9-∼14.2 Ma). Amphicyon first appears in the Oligocene of western Europe, surviving there until the late Miocene. Migration to Africa and North America takes place in the early Miocene. The genus occurs in the Arrisdrift fauna (Namibia) of southwest Africa, indicating migration south through the length of the African continent by the mid-Miocene. Its occurrence in Asia is problematical because of the tendency to place any moderately large Asian amphicyonid in the genus, and because of the fragmentary nature of many fossils. Here I report the earliest North American occurrences of Amphicyon (18.8-∼17.5 Ma), assigning these individuals to a new and previously undescribed species, Amphicyon galushai, from early Hemingfordian sediments of western Nebraska and north-central Colorado. In the New World, small early Hemingfordian Amphicyon galushai is probably ancestral to larger late Hemingfordian A. frendens, and to the terminal and largest species of the genus, early to mid-Barstovian A. ingens. Diagnostic basicranial and dental traits place these species in the Amphicyonidae, and demonstrate a close relationship of the North American lineage to the type species of the genus, A. major, from Sansan, France. Amphicyon galushai is known from a complete adult skull, a partial juvenile skull, three mandibles, and the isolated teeth and postcranial elements of ∼15 individuals, all from the early Miocene Runningwater Formation of western Nebraska. The species also is represented by a crushed rostrum from the Troublesome Formation, north-central Colorado. Basicranial, dental, and postcranial anatomy distinguish A. galushai from its contemporary in the Runningwater Formation, the large digitigrade beardog Daphoenodon. The Runningwater Formation contains the last occurrence of Daphoenodon in North America and the first occurrence of Amphicyon; the overlap in stratigraphic ranges of these two carnivores provides a useful early Miocene biostratigraphic datum. The two amphicyonids occur together in the same quarries, associated with canid, mustelid, and rare procyonid carnivores, which are much smaller animals. The North American species of Amphicyon (A. galushai, A. frendens, A. ingens) most likely adopted ecological roles similar to the large living felids (in particular, the lion Panthera leo). Their robust skeleton with powerful forelimbs, massive clawed feet, heavily muscled jaws with large canines, and a composite crushing/shearing dentition suggest a mobile predator that most likely stalked and ambushed prey from cover, overpowering its victims through sheer size and strength.
The early Middle Miocene locality at Arrisdrift, Namibia, has yielded seven species of carnivores, comprising a giant creodont, two amphicyonids, a mustelid, a stenoplesictid and two felids. The mustelid, stenoplesictid and felids belong to new genera and one of the amphicyonids is a new species, while the other forms are similar to species already known from East Africa and Europe. Comparisons of the Namibian fossils with those from other parts of Africa and Europe suggest that Arrisdrift correlates with Faunal Set P IIIa of East Africa (Pickford 1981) and the early part of MN04 of the European mammal zonation (ca 17-17.5 Ma) (Mein 1990).
DEDICATION RICHARD H. TEDFORDPawnee Buttes, Colorado, 1999
Carnivores exhibit a wide range of locomotor behaviors. However, an animal’s morphology limits its range of movements and therefore provides a constraint to certain locomotor activities. For instance, the body proportions and morphology of the sea otter (Enhydra lutris) make it an excellent swimmer, whereas it has difficulty moving on land. Likewise, the arboreal specializations of the ringtail (Bassariscus astutus), which allow it to perform complex acrobatic movements, restrict its abilities for other forms of locomotion such as running or digging. Some carnivores improve the effect of their locomotor skills with behavioral modifications; for example, the group hunting behavior of the African lion (Panthera leo) and the gray wolf (Canis lupus) allows them to catch prey that they would not be able to catch as individuals (Mech 1970; Schaller 1972). Therefore, from an evolutionary viewpoint, one must recognize that behavioral adaptations may be as important as morphological adaptations. However, although the behavior of many carnivores is poorly known, it is possible to infer a great deal from their morphological adaptations and to use this information in a predictive way to understand their role in particular ecosystems.
Astragalar fossils have been intensively studied as an indicator of the functional morphology and phylogenetic relationships of mammals. However, relatively few studies have investigated the relationship between astragalar size and body mass, usually with a focus on a particular taxonomic group. Here, univariate and multiple regression models are used to analyze the relationship between astragalar size and body mass based on an extensive sample of extant land mammals (11 orders, 48 species, 80 individuals; body mass ranging from 18 g to 3.4 t). The analyses revealed the size of the tibial trochlea to be a better predictor of body mass than the total size of the astragalus. Based on these results, estimates of the body mass of several Paleogene land mammals were calculated and compared to those of previous studies. Thus, for example, the body mass of "Baluchitherium", the largest terrestrial mammal known to date, was estimated at about 10-15 t.
The postcranial skeleton of the late Paleocene Arctocyon primaevus is described based on a sub-complete associated specimen. A comparison with arboreal or scansorial and fossorial extant taxa shows that on the forelimb, several features suggest arboreal capabilities, including the development of abductors and adductors, the development of digital flexors, which allows grasping/manipulative ability, as well as the highly mobile articulations, the convex ulna, and the pentadactyl, plantigrade foot. In contrast with the highly mobile joints of the limbs, Arctocyon had a rigid posterior thoracic area, characterized by revolute zygapophyses unknown in extant mammals. The morphology of the most anterior caudal vertebra indicates that the tail was long, powerful, muscular, and rigid at its base, and that it played an important role in locomotion. The morphology of the hind limb is congruent with that of the forelimb, the development of the adductors, flexors, and rotators of the mobile hip joint being emphasized. Although the femoral trochlea is longer and better defined than in highly arboreal taxa, Arctocyon probably moved in a controlled fashion. A comparison with South American borhyaenoids shows that Arctocyon is morphologically more similar to some predator-like Miocene metatherians than to any living mammal. It represents an interesting mix between Prothylacinus and Borhyaena in overall size and proportions, and shows a development of crests and processes of the humerus similar to those of Prothylacinus. Arctocyonidae, which evolved towards incipient saber-toothed canines combined with cheek teeth compatible with an omnivorous diet, and which show a postcranium that is morphologically more similar to carnivorans than to ungulates, represent a mosaic of features that is of particular interest in the evolution of mammals.
Previous analyses of the mammalian clade Carnivoramorpha have tended to sample only cranial and dental character systems, particularly those that included early Cenozoic taxa, Viverravidae and basal Carnivoraformes (the latter being a paraphyletic array of taxa traditionally referred to as the ‘Miacidae’). In this study we add more than 100 postcranial characters to an existing dataset dominated by cranio-dental characters. The addition of the new characters permits the inclusion of a large number of basal carnivoraforms, known solely or predominantly from postcranial characters, that previously would have been ‘unplaceable’ in a phylogenetic analysis. The resultant phylogeny recovers most of the same clades identified in previous studies, but resolves some relationships differently within the basal carnivoraforms. A novel (unnamed) monophyletic subclade of the Carnivoraformes is recovered, supported in part by characters from both the prior and new datasets. The inclusion of a substantial suite of postcranial characters expands the ability to assess the relationships of basal carnivoramorphan taxa, and permits the inclusion of many taxa represented only by incomplete material.
Fossil Carnivora from “Orléanais” continental sands. All the fossil carnivora from Orleanais are dated to middle Miocene. They belong to Amphicyonidae (7 species and 6 genera), Ursidae (3 species, 3 genera), Mustelidae (13 species, 8 genera), Nimravidae (1 species, 1 genus), Viverridae (3 species, 2 genera) and Felidae (4 species, 2 genera).