La tortuga de Porto de Mos en la XXII Bienal de la RSEHN

Como ha sido indicado en este blog, el ejemplar de Plesiochelyidae procedente del Oxfordiense de Porto de Mos (Portugal) ha sido presentado en la XXII Bienal de la RSEHN en Coimbra (Portugal). Este espécimen fue reconocido como uno de los pocos de un Plesiochelyidae hallados en niveles pre-kimmeridgienses y como el más antiguo representante de este grupo identificado a nivel genérico (ver aquí). El resumen es el siguiente:

The most abundant and diverse group of turtles in the Iberian record is Eucryptodira. It is represented by its crown group, Cryptodira, but also by several Mesozoic forms belonging to its stem group. The oldest lineage corresponds to Plesiochelyidae, a clade exclusive of the European Upper Jurassic record. These marine turtles were not adapted to a pelagic life, being inhabitants of coastal environments, mostly related to mid and inner shelf, open or rimmed carbonated systems. The plesiochelyids disappeared during the Jurassic–Cretaceous transition as result of the regression of the shallow shelf seas of Europe, probably due to a drastic reduction of their habitat.
Several plesiochelyid representatives have been recognized in the Kimmeridgian and Tithonian Iberian records, all of them being identified in the Portuguese Lusitanian Basin (see Pérez-García accepted and references therein). The first described member of Plesiochelyidae in the Iberian record was ‘Plesiochelys choffati’, from the Tithonian of Vila Franca do Rosario (Mafra, Portugal). It is now identified as belonging to Craspedochelys, a genus relatively common in the Kimmeridgian and Tithonian levels of the Lusitanian Basin. The presence of the genus Plesiochelys was subsequently confirmed in the Tithonian record of both Portugal and Spain. The presence of a third genus of Plesiochelyidae (i.e. Tropidemys) has recently been recognized in both the upper Kimmeridgian–lower Tithonian levels of Portugal and in the Tithonian record of Spain. This taxon is probably represented by two species.
The pre-Kimmeridgian record of Plesiochelyidae is poorly known. In fact, the only currently known specimens come from the Iberian record. The first one was found in upper Oxfordian beds from Sierra de Cazorla (Jaén, Spain). It corresponds to a relatively complete shell recognized to the holotype of a putative new taxon, ‘Hispaniachelys prebetica’. However, this taxon is now considered as nomen dubium, and the specimen is presently identified as belonging an indeterminate representative of Plesiochelyidae.
The second one is a shell from an upper Oxfordian section of the Lusitanian Basin (see Pérez-García et al., accepted). It comes from Alqueidão da Serra (Municipality of Porto de Mós). Several artisanal quarries have been working for a long time in this area, yielding a variety of Jurassic light grey limestones and the famous “black limestone”, a dark mudstone with quite dark, uniform color, mainly used to produce ubiquitous Portuguese cobblestone designs (“calçada portuguesa”), a traditional art internationally recognized. These carbonate layers also are quite fossiliferous and rich of invertebrate specimens, whichmostly belong to fresh to brackish, marginal marine environments. The turtle shell was found by Adolfo Correia de Carvalho (1934-2010), owner and worker of a local quarry, during the first months of 1989. It was carefully collected from its limestone cast and offered as a donation to the Museu Municipal de Porto de Mós, yet in process of constitution at that time.
Registered and incorporated as MMPM37 by Francisco Furriel (1925-2014), a local collector and first director of the museum, the turtle shell stood out side to side with many other fossil specimens and rocks, mostly collected from Middle and Upper Jurassic, and Upper Cretaceous outcrops of the nearby region. Despite to be separated in two pieces and exhibited without any previous preparation, this fossil merited through years the curiosity of the visitors.
Due to its rarity, the turtle shell from Porto de Mós also deserved a prominent place in the museum catalogue. However, until very recently, it has not been subjected to any detailed taxonomic study. Nowadays, a plan of the Council board to move the museum to another building with a new exhibition, was recently taken as an excellent opportunity to study this specimen, as a contribution to better understand this group of Jurassic vertebrates.
The specimen MMPM37 represents the oldest remain of a turtle identified in the Portuguese record, constituting the second identification of a plesiochelyid performed in pre-Kimmeridgian levels in all of Europe. This specimen can also be recognized as the only Oxfordian plesiochelyid identified at generic level.

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Referencia: 

• Pérez-García, A., J. M. Brandão, P. M. Callapez, L. Machado, E. Malafaia, F. Ortega, and V. F. dos Santos. 2017. A plesiochelyid turtle from the upper Oxfordian of Porto de Mós (West Central Portugal). XXII Bienal de La Real Sociedad Española de Historia Natural. Libro de Resúmenes 268–269.