7.7.16

Tortugas Europeas en el XIV Annual Meeting de la EAVP

Estamos en plena celebración de uno de los congresos de paleontología más relevantes de Europa, el Annual Meeting of the European Association of Vertebrate Palaeontologists. Se trata de su XIV edición, celebrada en la ciudad holandesa de Haarlem. Entre los trabajos presentados por los miembros del Grupo de Biología Evolutiva de la UNED figuran aquellos centrados en el análisis de varias tortugas europeas. Los resultados de estas investigaciones son defendidos hoy. Sus resúmenes son los siguientes:

A NEW GENUS FOR THE EUROPEAN MIDDLE EOCENE TURTLE ‘AFF. ERYMNOCHELYSEREMBERTI, AND STUDY OF TWO NEW CLOSELY RELATED FORMS

The European ‘aff. Erymnochelyseremberti is the only member of the Erymnochelys group of turtles (Pleurodira, Podocnemididae) so far defined in the Laurasiatic record. It is known by a single specimen, from the Lutetian (middle Eocene) of the French locality of Saint-Germain-en-Laye (Yvelines, Île-de-France). This specimen corresponds to a partial skeleton, including the skull and lower jaw, the fragmentary but partially reconstructed dorsal carapace, the relatively complete plastron, and various partial remains of the axial and appendicular skeleton. Its description and detailed study are completed here, a diagnosis for this species being proposed for the first time. It is attributed to a new genus, corresponding to both the first genus of the Erymnochelys group defined outside of Africa and the oldest unambiguous generic determination of a member of this group heretofore attested. It corresponds to a coastal form, all the African representatives being continental taxa. This middle Eocene species is not the only member of the Erymnochelys group identified in the European record, this group also being represented in the Early and Late Eocene. Thus, a Spanish specimen from the late Eocene (Priabonian) of Can Beuloví (Sobremunt, Osona, Catalonia), as well as an almost complete shell from the early Eocene (Ypresian) of the French locality of Soulane (Jonquières, Aude, Languedoc-Roussillon-Midi-Pyrénées), are studied. This French specimen is identified as attributable to a new species, being the oldest defined representative of the Erymnochelys group. The Spanish specimen also corresponds to a new species.

THE OLDEST EUROPEAN TESTUDINIDS: DESCRIPTION OF NEW TAXA AND REVISION OF POORLY-KNOWN FORMS


Testudinidae is the only extant clade of tortoises (i.e. terrestrial turtles). It is recognized as a very successful group, based on its abundance, diversity, and geographic distribution. It is relatively abundant in the fossil record. In this sense, the knowledge about its Neogene evolutionary history is relatively good. However, its Paleogene record is much more limited.
Testudinids are known in Europe from the early Eocene. Scarce information on the taxonomy and systematics of the European Eocene testudinids was so far available. The oldest testudinids from Europe, recovered in early and middle Eocene levels of several countries, are studied here. Some of them were previously known, being generally attributed to North American genera (i.e. Hadrianus and Achilemys). The hypothesis suggesting that the European Eocene genera are exclusive of this continent is confirmed. Thus, two new genera are proposed. The largest collection of European Paleogene testudinids, from the middle Eocene of Mazaterón (Soria, Spain), has been prepared for this study. A new species from Mazaterón is proposed. The validity of some European Eocene taxa is refuted, the French middle Eocene ‘Testudo castrensis’, the Austrian middle Eocene ‘Cheirogaster steinbacheri’, and the Spanish middle-late Eocene ‘Asturichelys multicostatus’ being proposed as nomina dubia. The diagnosis of several forms is emended. In addition, some of the taxa analyzed here are included for the first time in a phylogenetic hypothesis including, among others, the European medium to large testudinids.

ON THE PRESENCE OF BOTHREMYDIDAE (TESTUDINES, PLEURODIRA) IN THE EUROPEAN CENOZOIC RECORD


Pleurodira is a lineage of turtles originated in Gondwana. Several migrations of this group to Europe are known from the Upper Cretaceous, and especially, during the uppermost Cretaceous and the Eocene. In this regard, several representatives of Podocnemididae (Pelomedusoides) are known in the Eocene record of this continent, including the abundant and diverse European taxon Neochelys, as well as various forms of the Erymnochelys group, currently under study (e.g. ‘aff. Erymnochelys’ eremberti). A second Gondwanan lineage of Pelomedusoides also migrated from Africa to Europe: Bothremydidae. This group was very abundant and diverse on the uppermost Cretaceous record of this continent. However, it has not so far been unambiguously identified in the European Cenozoic record.
A new representative of Pleurodira is presented here. It comes from the early Eocene of Southwestern Europe. The new taxon is represented by two skulls. It is attributable to Pelomedusoides. Several characters shared with the members of Bothremydidae are recognized in this taxon. Its detailed study, together with the revision of poorlyknown specimens, provides new data to assess whether Bothremydidae was part of the turtle fauna of the European Eocene record.

THE OLDEST MEMBER OF THE CROWN PLEURODIRA IN LAURASIA

Pleurodira is one of the two major lineages of turtles known from the Early Cretaceous to the present. The first representatives of this clade are Gondwanic forms. In fact, extinct and extant pleurodires were restricted to relatively warm regions, their temperature requirements being much more extreme than those of the sister group Cryptodira. Although Pleurodira is now restricted to tropical and intertropical regions, changes in the global temperatures and in the relative position of the landmasses allow the dispersal of some representatives to Laurasia. Thus, these diachronic migrations were known from the Santonian, being especially relevant between the uppermost Cretaceous and the Eocene. In this sense, both Bothremydidae and Podocnemididae were relatively abundant and diverse in the European record (Bothremydidae in the Late Cretaceous and Podocnemididae in the Paleogene).
A new representative of Pleurodira, corresponding to a member of Bothremydidae, is presented here. The new taxon comes from pre-Santonian levels of Southwestern Europe. It is represented by abundant remains, highlighting a skull, relatively complete and partial shells, abundant plates, and appendicular elements. This discovery shows that the first migration of Pleurodira from Gondwana to Laurasia occurred earlier than hitherto proposed.
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