Mauricio Antón

The giant hyaena,Pachycrocuta brevirostris (Mammalia, Carnivora, Hyaenidae)

The giant hyaena, Pachycrocuta brevirostris, is known from deposits in Africa and Eurasia between ca. 3.0 and 0.5 Ma. It is the largest of the true hyaenas, but that size is not reflected in overall shoulder height since the distal limb segments are relatively shorter than those of living taxa. Its bodily proportions therefore appear to be suited to power and strength rather than speed. Its eventual extinction is part of the overall evolution in large carnivore guilds throughout the world and may have been closely linked to the extinction of machairodont cats.

Neck function and predatory behavior in the scimitar toothed cat Homotherium latidens (Owen)

ABSTRACT The morphology of the cervical vertebrae and skull structures associated with the neck musculature was studied in the felid sabertooth Homotherium latidens from the Spanish early Pleistocene site of Incarcal. Cervical anatomy of Homotherium was compared to that of modern pantherine cats, Smilodon, and other sabertoothed carnivores, and the relationship between neck function and killing behavior was investigated. Homotherium latidens possesses the structures associated with the canine shear-bite, as described in Smilodon. Our study of muscle insertion areas in the cervical vertebrae of Homotherium does not support previous statements about unusually strong scalenes and their role in stabbing. Instead, we see evidence of increased muscular control of various movements of the neck, including lateral flexion, depression and extension. These features, and the greater relative length of the neck in Homotherium and other machairodonts, are interpreted as adaptations for delivering a canine shear-bite in...

First known complete skulls of the scimitar-toothed cat Machairodus aphanistus (Felidae, Carnivora) from the Spanish late Miocene site of Batallones-1

Abstract We describe a sample of skulls, mandibles and isolated dentitions of Machairodus aphanistus from the Spanish late Vallesian (late Miocene) site of Batallones-1, near Madrid. This is the first time that the cranial morphology of this species has been seen in detail, and shows that late Vallesian M. aphanistus combined a relatively primitive cranial and mandibular morphology with very specialized upper canines, as flattened as in the later, cranially derived species M. giganteus. Cranio-mandibular adaptations for the canine shear-bite are incipient or non-existent, suggesting that the specialized canines of M. aphanistus were used within the context of a biting mechanism more similar to the canine bite of modern felids. Evolution of more extreme machairodont craniodental features in later members of the homotherin lineage converged with smilodontins but occurred independently of the initial development of derived saber-like canines. The high number of specimens, at least 14 individuals represented, reveals considerable variation in size within the population, with indications of sexual dimorphism in the size of the upper canines. Differences in cranial morphology suggest separation at the generic level between M. aphanistus and M. giganteus.

Functional anatomy of the forelimb in Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the Late Miocene of Spain and the origins of the sabre-toothed felid model

We examine the functional anatomy of the forelimb in the primitive sabre‐toothed cat Promegantereon ogygia in comparison with that of the extant pantherins, other felids and canids. The study reveals that this early machairodontine had already developed strong forelimbs and a short and robust thumb, a combination that probably allowed P. ogygia to exert relatively greater forces than extant pantherins. These features can be clearly related to the evolution of the sabre‐toothed cat hunting method, in which the rapid killing of prey was achieved with a precise canine shear‐bite to the throat. In this early sabre‐toothed cat from the Late Miocene, the strong forelimbs and thumb were adapted to achieve the rapid immobilization of prey, thus decreasing the risk of injury and minimizing energy expenditure. We suggest that these were the major evolutionary pressures that led to the appearance of the sabre‐toothed cat model from the primitive forms of the Middle Miocene, rather than the hunting of very large prey, although these adaptations reached their highest development in the more advanced sabre‐toothed cats of the Plio‐Pleistocene, such as Smilodon and Homotherium. Although having very different body proportions, these later animals developed such extremely powerful forelimbs that they were probably able to capture relatively larger prey than extant pantherins.

Implications of the functional anatomy of the hand and forearm of Ailurus fulgens (Carnivora, Ailuridae) for the evolution of the ‘false-thumb’ in pandas

Both the giant panda (Ailuropoda melanoleuca) and the red panda (Ailurus fulgens) possess a ‘false‐thumb’, actually an enlarged radial sesamoid bone, which contributes to the gripping action of the hand. These species are not closely related, however, as one is an ursid and the other an ailurid, so the fact that they share this adaptation implies a remarkable convergence. We studied the functional anatomy of this structure in the red panda, comparing it with existing descriptions of the grasping mechanism in both pandas. Previous interpretations of the radial sesamoid in Ailurus as a rod‐like structure without direct articulation to the wrist bones are inaccurate. There are various important differences between the red panda and the giant panda. In the former, the lesser development of the radial sesamoid, its connection with the flexor retinaculum, the presence of an insertion of the muscle abductor pollicis longus in the first metacarpal, which enhances its supinatory action, and the presence of a muscle flexor brevis digitorum manus point to thin‐branch climbing features serving as an exaptation to the more recent role of the red panda hand in the manipulation of bamboo.

Systematics and phylogeny of the small felines (Carnivora, Felidae) from the Late Miocene of Europe: a new species of Felinae from the Vallesian of Batallones (MN 10, Madrid, Spain)

The Spanish fossil localities of Batallones-1 and Batallones-3 are two Vallesian (Late Miocene) natural traps known for their high concentration of carnivoran mammals. These include amphicyonids, ailurids, mustelids, ursids, hyaenids, machairodont felids, and two species of small-bodied felines, one the size of an European wildcat, Felis sylvestris, and the other the size of a caracal, Caracal caracal. Although these felines are much less abundant at the sites than their larger relatives, the sabre-toothed felids, the available samples from Batallones-1 and Batallones-3 are rich; they include postcranial elements, skulls and mandibles of the smaller species, while the larger feline species is solely known from postcranial elements recorded at Batallones-1. The small feline from Batallones-1 and Batallones-3, although showing similarities with the Turolian felines, is more related to the Middle Miocene genus Styriofelis Kretzoi, 1929, and thus we propose for it the new species name Styriofelis vallesiensis. On the other hand, the new generic name Pristifelis is proposed for the species Felis attica, which shows important differences with extant Felis.

The evolution of the bone-cracking model in carnivorans: cranial functional morphology of the Plio-Pleistocene cursorial hyaenid Chasmaporthetes lunensis (Mammalia: Carnivora)

Abstract Fossil species of the family Hyaenidae represent a wide range of ecomorphological diversity not observed in living representatives of this carnivoran group. Among them, the cursorial meat-and-bone specialists are of particular interest not only because they were the most cursorial of the hyaenids, but also because they were the only members of this family to spread into the New World. Here we conduct a functional morphological analysis of the cranium of the cursorial meat-and-bone specialist Chasmaporthetes lunensis by using finite element modeling to compare it with the living Crocuta crocuta, a well-known bone-cracking carnivoran. As found with previous finite element studies on hyaenid crania, the cranium of C. lunensis is not differentially adapted for stress dissipation between the bone-cracking and meat-shearing teeth. A smaller occlusal surface on the more slender P3 cusp of C. lunensis allowed this species to use less bite force to crack a comparably-sized bone relative to C. crocuta, but higher muscle masses in the latter probably allow it to process larger food items. We use two indices, the stress slope and the bone-cracking index, to show that C. lunensis has a well-adapted cranium for stress dissipation given its size, but the main stresses placed on its cranium might have been more from subduing prey and less from cracking bones. Throughout the Cenozoic, other carnivores besides hyaenids convergently evolved similar morphologies, including domed frontal regions, suggesting an adaptive value for a repetitive mosaic of features. Our analyses add support to the hypothesis that bone-cracking adaptations are a complex model that has evolved convergently several times across different carnivoran families, and these predictable morphologies may evolve along a common gradient of functionality that is likely to be under strong adaptive control.

Quantitative inferences on the locomotor behaviour of extinct species applied to Simocyon batalleri (Ailuridae, Late Miocene, Spain)

Inferences of function and ecology in extinct taxa have long been a subject of interest because it is fundamental to understand the evolutionary history of species. In this study, we use a quantitative approach to investigate the locomotor behaviour of Simocyon batalleri, a key taxon related to the ailurid family. To do so, we use 3D surface geometric morphometric approaches on the three long bones of the forelimb of an extant reference sample. Next, we test the locomotor strategy of S. batalleri using a leave-one-out cross-validated linear discriminant analysis. Our results show that S. batalleri is included in the morphospace of the living species of musteloids. However, each bone of the forelimb appears to show a different functional signal suggesting that inferring the lifestyle or locomotor behaviour of fossils can be difficult and dependent on the bone investigated. This highlights the importance of studying, where possible, a maximum of skeletal elements to be able to make robust inferences on the lifestyle of extinct species. Finally, our results suggest that S. batalleri may be more arboreal than previously suggested.

Carnivore Trackways from the Miocene Site of Salinas de Añana (Alava, Spain)

A fossil tracksite of Lower Miocene age discovered near Salinas de Anana, Alava (Spain), has rendered an exceptionally well-preserved assemblage of vertebrate ichnites. The site shows a high proportion of carnivore tracks (3 out of 5 mammal ichnospecies) and a high number of individual trackways (15), some including over 50 consecutive footprints. The carnivore ichnites are classified as Felipeda lynxi Panin & Avram, 1962, Felipeda parvula ichnosp. nov. and Canipeda longigriffa Panin & Avram, 1962, and they are attributed to a felid, an undetermined small aeluroid, and a herpestid, respectively. The long trackways allow determination of gaits, which include lateral sequence walks and diagonal sequence trots, and of speed, which ranges from 0.4 to 1.4 m/s. Froude numbers range between 0.1 and 0.8, agreeing with gait interpretations and speed calculations. The felid trackways provide the first known evidence of group traveling in fossil cats. The herpestid footprints show modern-grade adaptations for terres...

Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the Vallesian (Late Miocene, MN 10) of Spain: Morphological and Functional Differences in Two Noncontemporary Populations

ABSTRACT We compare two populations of the primitive saber-toothed felid Promegantereon ogygia from the late Miocene (Vallesian, MN 10) of Spain. These populations come from two fossil sites, Batallones-1 and Batallones-3, located very close to each other, within the Cerro de los Batallones complex. The sites show differences in age and in their faunal assemblages, with Batallones-1 being older than Batallones-3. We find that the population from this latter site shows slightly derived characters in both dentition and postcranial elements, which clearly indicate evolution within the Promegantereon lineage, but are not strong enough to support a separation at the species level.