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.

New data on the mammalian fauna from the late middle Eocene (MP 15-16) of Mazaterón (Soria, Spain): The youngest presence of the genus Prodissopsalis (Hyaenodonta, Hyaenodontidae) in Europe.

The Hyaenodonta were the most diverse carnivorous mammals in the European Eocene and were classically divided into three subfamilies: Sinopaninae, Arfianinae, and Proviverrinae, with this latter being the most successful of the three, as it exhibited a much larger geographic and temporal range. This classification is currently abandoned, as cladistic analyses of Hyaenodonta showed that several of these groups were paraphyletic. In any case, the former "proviverrines" were European endemic hyaenodontids which occupied the niche of small to medium-sized predators from the Ypresian (MP7) to the Priabonian (MP19). Recent phylogenetic proposals recognize the "Eurotherium clade" including this latter genus, besides Cartierodon and Prodissopsalis. A single species is known for Prodissopsalis, Prodissopsalis eocaenicus, previously recorded in European fossil sites of MP 12 to MP 14; nevertheless, the new material studied here, a mandible of a subadult individual from the late Middle Eocene (Bartonian, MP 15-16) site of La Solana (Mazaterón, Soria, Spain) constitutes a new species of Prodissopsalis and the youngest record of this genus up to now, extending its chronological range and remarking the shelter role of the northwestern region of the Iberian Peninsula during the Middle and Late Eocene. The new species, Prodissopsalis jimenezi provides new data not only on the eruption sequence of the genus, but also on the evolution of its dental adaptations, as the new species exhibits a more trenchant, hypercarnivorous dentition in comparison to the more primitive species P. eocaenicus, which would point toward a refining of the hunting abilities of this hyaenodont during the Middle Eocene.

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.

First evidence of pathology in the forelimb of the late Miocene saber-toothed felid Promegantereon ogygia (Machairodontinae, Smilodontini).

We examined the first evidence of pathology in the forelimb of the primitive saber-toothed felid Promegantereon ogygia, observed in a radius from the late Miocene (Vallesian, MN 10) site of La Roma 2 (Teruel, Spain). This fossil is the first evidence of a member of the Machairodontinae in this locality, and the first fossil of this species found in the Miocene basin of Teruel. The radius shows an exostosis shaped as a rough and wide bony crest probably caused by the lesion and posterior ossification of part of the tendon of the muscle abductor pollicis longus, an important extensor and abductor of the thumb. The lesion was probably due to a tearing or to high levels of exertion experienced by this muscle over a relatively long time, a general type of lesion also observed in other vertebrate fossils. With saber-toothed felids using their thumbs to immobilize prey during the hunt, the studied lesion probably affected in a significant manner the predatory abilities of the animal, causing at least a decrease in its hunting success rate.

Systematics and taxonomy of the Spanish Anchitheriinae, and their relationship with regional climate changes: a comment on Eronen et al.

In a recent paper, Eronen et al. (2010; hereafter EEFJ) observe differences in occlusal morphology, tooth crown height, and mesowear pattern between populations of the Miocene tridactyl equid Anchitherium from Spain and Germany, proposing that Spanish Anchitherium underwent adaptive evolution to local or regional arid conditions. However, these authors do not take into account the actual diversity of Iberian representatives of Anchitherium, or the fact that the Spanish fossils cover a wider temporal and geographical range than those from Germany. For these reasons, we suggest that their subsequent statistical work should be reconsidered.

Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas.

The "false thumb" of pandas is a carpal bone, the radial sesamoid, which has been enlarged and functions as an opposable thumb. If the giant panda (Ailuropoda melanoleuca) and the red panda (Ailurus fulgens) are not closely related, their sharing of this adaptation implies a remarkable convergence. The discovery of previously unknown postcranial remains of a Miocene red panda relative, Simocyon batalleri, from the Spanish site of Batallones-1 (Madrid), now shows that this animal had a false thumb. The radial sesamoid of S. batalleri shows similarities with that of the red panda, which supports a sister-group relationship and indicates independent evolution in both pandas. The fossils from Batallones-1 reveal S. batalleri as a puma-sized, semiarboreal carnivore with a moderately hypercarnivore diet. These data suggest that the false thumbs of S. batalleri and Ailurus fulgens were probably inherited from a primitive member of the red panda family (Ailuridae), which lacked the red panda's specializations for herbivory but shared its arboreal adaptations. Thus, it seems that, whereas the false thumb of the giant panda probably evolved for manipulating bamboo, the false thumbs of the red panda and of S. batalleri more likely evolved as an aid for arboreal locomotion, with the red panda secondarily developing its ability for item manipulation and thus producing one of the most dramatic cases of convergence among vertebrates.

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.