Meike Köhler

New Miocene hominoid specimens from Can Llobateres (Vallès Penedès, Spain) and their geological and paleoecological context

Abstract Nine new dental specimens and their geological context are described from the Late Miocene hominoid locality of Can Llobateres (Valles Penedes, Spain). This brings the number of accessioned specimens from Can Llobateres to 46, nearly twice the number of specimens from the next richest Dryopithecus locality. The collection from Can Llobateres samples a broad range of morphological and metric variability. However, relative measures of sample variability indicate that this diversity is within the observed ranges for individual sexually dimorphic anthropoid species. Thus, the whole sample is attributed to Dryopithecus laietanus, based on strong similarities to the type specimen from the nearby locality of La Tarumba. Dryopithecus laietanus is the most widespread species of the genus in Spain. Six of the eight Miocene hominoid localities from Spain contain only this form, which persists for two to three million years, from the late Middle Miocene (MN 8) to the early part of the Late Miocene (MN 10).

Phalangeal adaptations in the fossil insular goat Myotragus

FIGURE 1. Geographic area of the Mediterranean sea. Arrow locates the Balearic Islands. In this paper, we describe a peculiar stabilizing mechanism in manus and pes of Myotragus, a fossil rupicaprine bovid known from Pliocene through Pleistocene deposits in the Balearic Islands (Mediterranean Sea). Deep and isolated notches on the metapodial-phalangeal and the interphalangeal joint surfaces suggest that these bones were bound together by intracapsular ligaments. Functionally, these ligaments fix the digits in a completely vertical position thus stabilizing the joints but minimizing their shock absorbing capacity. This unique morphology evolved under the special conditions of insular ecosystems, where the lack of predators allowed an increase in stability and safety at the expense of speed. Myotragus (Artiodactyla: Bovidae) is an endemic fossil goat from the Plio–Pleistocene of the Balearic Islands in the Mediterranean Sea (Fig. 1). This insular bovid is believed to have settled in these islands in the late Miocene, during the Messinian Salinity Crisis (Hsü et al., 1977; Moyà-Solà et al., 1985; Agustı̀ and Moyà-Solà, 1990), and became extinct in prehistoric times, in about 6,000 B. P. (before present; Alcover et al., 1981). Myotragus was described at the beginning of the 1900s by the English paleontologist Miss D. Bate (1909). The fossil record of Myotragus impressively illustrates the extent of structural modifications that may affect the artiodactyl skeleton through changing from a continental to an insular ecosystem (Bate, 1909; Alcover et al., 1981). Among other features, it is characterized by an extremely modified dentition and a peculiar cranial and postcranial morphology. M. balearicus, unlike any other extant ruminant, has a single evergrowing incisor with an open root in each half of the mandible (Bate, 1909). The tooth row is reduced, with the dental formula I0/1 C0/0 P2/1 M3/3 for adult individuals. The molars are hypsodont to such an extent that in juvenile specimens the roots of m1 and m2 deform the base of the mandibular ramus during ossification. The cranium is short faced, with the orbits frontalized to a similar degree as in prosimian primates. Also, the postcranial skeleton displays a large number of specializations not found in continental bovids, such as the partial fusion of tarsals, metatarsals and sesamoids, and length reduction of distal limb bones, especially of the metacarpals and the metatarsals (for more detailed descriptions see Bate, 1909; Sondaar, 1977; Leinders, 1979; Moyà-Solà, 1979; Spoor, 1988a, b). In this paper, we describe the joint surfaces of proximal, medial, and distal phalanges of foreand hindlimbs of Myotragus and compare the morphology with that of Capra and Oreotragus. We reconstruct the position of metacarpals and phalanges during stance and locomotion, with maximal congruency of the joint surfaces and provide a functional interpretation that considers the special conditions of insular ecosystems.

Un nouveau site a vertebrés continentaux de l´Eocene superieur de Zambrana (Bassin de Miranda-Treviño, Alava, Pays Basque).

Resume Des fouilles recentes dans lEocene superieur de Zambrana (Alava, Pays basque) ont livre des restes devertebres continentaux, les premiers decouverts dans le bassin tertiaire de Miranda-Trevino. Lassociation fossile est composee de tortues (Chelonii indet.), crocodiliens ( Diplocynodon sp.) et mammiferes, qui comprennent de possibles insectivores (Lipotyphla indet.), carnivores (cf. Quercygale sp.), rongeurs ( Theridomys aff. golpei, Elfomys aff. parvulus , Pseudosciurinae indet., Glamys priscus ), artiodactyles (Xiphodontidae indet.) et perissodactyles ( Paranchilophus sp., Plagiolophus aff. mazateronensis, Palaeotherium sp.). Lassociation de rongeurs et de perissodactyles suggere un âge ludien (Priabonien) moyen-inferieur, correspondant a la biozone MP 18. La faune de mammiferes de Zambrana est comparable aux faunes endemiques de lEocene moyen-superieur des bassins iberiques occidentaux et centraux. Les depots fossiliferes sont des marnes et des calcaires a niveaux de charbon, dorigine lacustre. Letude geologique de la region indique que le bassin tertiaire de Miranda-Trevino a ete fortement influence par lactivite tectonique regionale et que les premiers mouvements compressifs importants lies a la phase pyreneenne de lorogenese alpine ont eu lieu pendant lEocene inferieur.