Identification of the African–European Erymnochelys Group (Pleurodira
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Foss. Rec., 20, 245–251, 2017 https://doi.org/10.5194/fr-20-245-2017 © Author(s) 2017. This work is distributed under the Creative Commons Attribution 4.0 License. Identification of the African–European Erymnochelys group (Pleurodira, Podocnemididae) in the Belgian fossil record: first finding of Eocenochelus eremberti outside its type locality Adán Pérez-García1 and Thierry Smith2 1Grupo de Biología Evolutiva, Facultad de Ciencias, UNED, Paseo de la Senda del Rey 9, 28040 Madrid, Spain 2Directorate Earth & History of Life, Royal Belgian Institute of Natural Sciences, rue Vautier 29, 1000 Brussels, Belgium Correspondence to: Adán Pérez-García ([email protected]) Received: 16 June 2017 – Revised: 24 August 2017 – Accepted: 1 September 2017 – Published: 11 October 2017 Abstract. An almost complete plastron, as well as several of them is Bothremydidae, identified in Europe from the peripherals and a costal plate of a turtle from the middle Cenomanian (Pérez-García, 2016a). The greatest diversity Eocene of Saint-Gilles, is presented here. Although this tur- of this lineage in Europe was achieved during the upper- tle specimen was donated to the Institut royal des Sciences most Cretaceous (Tong et al., 1998; de Lapparent de Broin, naturelles de Belgique (Brussels, Belgium) more than a cen- 2001; Gaffney et al., 2006; Pérez-García et al., 2012). The tury ago, it remained undescribed. Its study allows us to rec- presence of this clade in the Cenozoic record of Europe has ognize the second pleurodiran in the Belgian fossil record, recently been confirmed, thanks to the discovery of cranial where, until now, the Eocene Neochelys was the only one and postcranial material from the lower Eocene (early Ypre- known. The Belgian material of Neochelys is known in lower sian) of Saint-Papoul (Aude, France) (Pérez-García, 2016b). Eocene (early Ypresian) levels, but the new pleurodiran spec- Whereas the confirmed record of Bothremydidae in the imen comes from the middle Eocene (early Lutetian). It is the Cenozoic levels of Europe is currently restricted to that find- first partial articulate shell of a pleurodiran turtle recognized ing, the other lineage of the crown Pleurodira that reached in Belgium, and the only member of this clade recognized in Europe was very successful during the Eocene, being repre- this country at specific level. The new specimen is a represen- sented in several countries (de Broin, 1977; de Lapparent de tative of the so-called Erymnochelys group, this lineage being Broin, 2003; Pérez-García and de Lapparent de Broin, 2013, known in Africa from the Upper Cretaceous to the present but 2015; Cadena, 2015; Pérez-García et al., 2017; Pérez-García in Europe only during the Eocene. It represents the first spec- and Chapman, 2017). This lineage is Podocnemididae, with imen of Eocenochelus eremberti identified outside its type two genera being currently recognized. The most abundant locality, the French region of Saint-Germain-en-Laye (Yve- and diverse is Neochelys Bergounioux, 1954, known by nine lines, Île-de-France), where only one specimen was found. species (de Lapparent de Broin, 2003; Pérez-García and de The plastron of the Belgian individual corresponds to the Lapparent de Broin, 2013, 2015). Neochelys is a genus of most complete for this species. Its analysis allows us not only freshwater turtles, belonging to Erymnochelyinae. The pres- to broaden the range of paleobiogeographical distribution of ence of a second genus of Erymnochelyinae, closely related Eocenochelus eremberti but also to improve the knowledge to the African extant form Erymnochelys madagascarien- about the anatomy and variability of this taxon. sis (Grandidier, 1867), has been recognized in several pub- lications (see de Broin, 1977; Lapparent de Broin in Merle, 2008; Pérez-García and de Lapparent de Broin, 2015). How- ever, it has only recently been named (Pérez-García et al., 1 Introduction 2017): it is the littoral form of Eocenochelus Pérez-García, Lapparent de Broin and Murelaga, 2017. The middle Eocene Two lineages of the crown Pleurodira have been recognized (upper middle Lutetian) “Erymnochelys” eremberti de Broin, in the European fossil record, both coming from Africa. One 1977, from Saint-Germain-en-Laye (Yvelines, France), was Published by Copernicus Publications on behalf of the Museum für Naturkunde Berlin. 246 A. Pérez-García and T. Smith: Eocenochelus in the Belgian fossil record defined as the type species of Eocenochelus (Pérez-García Sand Formation (Bruxellian in the old literature; De Geyter et al., 2017). It is represented by a single specimen, corre- et al., 2006) belongs to the upper part of the Zenne Group and sponding to a partial skeleton including the articulated skull is correlated with the NP14 biozone (Steurbaut, 2006), cor- and lower jaw, the partial carapace and plastron, and some responding to the early Lutetian (46 to 48 Ma) (Fig. 1). The vertebrae and appendicular elements. In addition, two other matrix that was associated with the specimen also contained species of this genus are currently recognized, each of them a valve of an oyster referred to Ostrea cymbula and some by a single shell: the lower Eocene (early Ypresian) Eo- buccinoid gastropods referred to Fusus longaevus, both taxa cenochelus lacombianus Pérez-García, Lapparent de Broin being sea forms (Delheid, 1893). and Murelaga, 2017, from Jonquières (Aude, France), and the upper Eocene (Priabonian) Eocenochelus farresi Pérez- García, Lapparent de Broin and Murelaga, 2017, from Osona 3 Systematic paleontology (Catalonia, Spain). Testudines Batsch, 1788 Only one representative of Pleurodira has so far been recognized in the Belgian record: Neochelys, identified by Pan-Pleurodira Joyce, Parham and Gauthier, 2004 scarce and disjointed plates from the lowest Eocene (earli- est Ypresian) of Dormaal (de Broin, 1977; de Lapparent de Pleurodira Cope, 1864 Broin, 2003). A specimen found more than a century ago, Pelomedusoides Cope, 1868 but remaining unpublished up to now, is studied in this paper. It comes from the middle Eocene (Lutetian) of Saint-Gilles Podocnemidoidea Cope, 1868 (Brussels, Belgium) (Fig. 1) and is a partial shell, which pre- serves the almost complete plastron, some peripheral plates Podocnemididae Cope, 1868 and a costal plate. It is identified as a member of Podocne- Erymnochelyinae Broin, 1988 mididae, but it cannot be attributed to Neochelys. Its study allows us to recognize the presence of the littoral form Eo- Eocenochelus Pérez-García, Lapparent de Broin and Mure- cenochelus in the Belgian record. Its attribution to the middle laga, 2017 Eocene Eocenochelus eremberti is justified, the knowledge Eocenochelus eremberti (de Broin, 1977) about this poorly represented form being improved. Institutional abbreviations: IRSNB, Institut royal des Sci- Material: IRSNB R356, a partial shell preserving the ences naturelles de Belgique, Brussels, Belgium; NHMUK, almost complete plastron articulated with the right partial Natural History Museum, London, UK; MNHN.ZA AC, third to sixth bridge peripherals (Fig. 2a–d), a disjointed left Anatomie Comparée, Muséum national d’Histoire na- bridge peripheral (Fig. 2e–g), and a disjointed costal plate, turelle, Paris, France; MNHN.ZR, Zoologie des Reptiles, probably corresponding to the left fourth costal (Fig. 2h–i) Muséum national d’Histoire naturelle, Paris, France; SMNS, (Collection Delheide, IG 8289). Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Ger- many. Locality and horizon: Saint-Gilles (Brussels, Belgium), Bruxellian regional stage, Brussels Sand Formation, early Lutetian, middle Eocene. 2 Geographical and geological context Description: The plastron of IRSNB R356 is almost The specimen described herein comes from the E. Delheid complete, only lacking the right latero-posterior margin collection that had been donated to the Royal Belgian Insti- of the posterior lobe (Fig. 2a–d). Its maximum length is tute of Natural Sciences (RBINS) on 2 August 1911. This 39.7 cm. The anterior lobe is subrounded (Fig. 2a–b). The collection bears the general inventory number IG8289 and length of this lobe is approximately half of its width. It is represented by fossil remains of mammals, birds, reptiles, lacks intergular or gular protrusions. The length of the crustaceans, mollusk shells, and plants from different fossil epiplastral symphysis is a quarter of that of the entoplastron. localities of the Belgian Tertiary. The entoplastron is rhombic, being slightly wider than long. The turtle specimen, originally referred to Emys?, was Although this plate is relatively large, its anterior end does found in 1893 in middle Eocene calcareous sands that were not reach the level of the axillary notches. The hyoplastra temporarily exposed during the construction of a house in are longer than the hypoplastra. A pair of subelliptical Aqueduc Street in Saint-Gilles (now a municipality of Brus- mesoplastra is laterally located. These plates are longer than sels) (Fig. 1). This information was communicated by E. Del- wide. The posterior plastral lobe is wide, being as wide as heid on 6 May 1893 at the Royal Belgian Malacological So- the anterior. It is longer than the anterior. Its lateral margins ciety (Delheid, 1893). Delheid discovered this fossil turtle in are slightly convex. A well-developed anal notch is present. the Brussels Sand Formation about 1.25 m below the basal Its total length is about half of its width. The lateral margins gravel bed of the Laekenian regional stage. The Brussels are subrounded. Both the pubis and the ischia were sutured Foss. Rec., 20, 245–251, 2017 www.foss-rec.net/20/245/2017/ A. Pérez-García and T. Smith: Eocenochelus in the Belgian fossil record 247 Figure 1. Map of Brussels municipality (Belgium) showing the geographic position of Aqueduc Street in Saint-Gilles where the specimen IRSNB R356 of Eocenochelus eremberti studied in this paper was discovered, in the lower Lutetian Brussels Sand Formation (middle Eocene). The position of the holotype of this species, from the upper middle Lutetian of Saint-Germain-en-Laye (Yvelines, France), is also indicated in the first map.