On the validity of the British Upper Jurassic turtle “Pleurosternon portlandicum” (Paracryptodira, Pleurosternidae)

A new Iberian pleurosternid (Jurassic-Cretaceous transition, Spain) and first neuroanatomical study of this clade of stem turtles

“…The presence of Pleurosternon had been confirmed in the Upper Jurassic (upper Tithonian) and Lower Cretaceous (Berriasian) records of both Great Britain and France (Gônet et al 2018;Joyce and Anquetin 2019;Guerrero and Pérez-García 2020), the species Pleurosternon bullockii being the only one identified in the two regions (Guerrero and Pérez-García 2020). The specimen analyzed here allows us to recognize the presence of a form closely related to Pleurosternon bullockii in the Iberian record, expanding the palaeobiogeographic distribution of the genus Pleurosternon, and describing a second representative, Pleurosternon moncayensis sp.…”

“…The ornamental pattern of Peltochelys duchastelii is also radically different from that of any representative of Paracryptodira but resembles that of some members of Cryptodira (see Meylan 1988;Pérez-García 2011). Furthermore, the reinterpretation of the putative presence of a single gular scute in Peltochelys duchastelii, made by Joyce and Rollot (2020), contrasts with the condition in the members of Paracryptodira, the presence of two scutes being recently confirmed for Pleurosternon bullockii, a condition shared with all other pleurosternids (Guerrero and Pérez-García 2020). Taking all this into account, the Joyce and Rollot's (2020) reconsideration of some Mesozoic European members of Pleurosternidae as representatives of Compsemydidae,exclusively as a result of the inclusion of Peltochelys duchastelii in a matrix of Paracryptodira, cannot be supported here.…”

“…The first-hand study of all these taxa shows that each of these two putative groups does not possess a unique ornamental pattern shared between its members and different from those of the other. Thus, the pattern of Selenemys lusitanica is different from that of Riodevemys inumbragigas, Peltochelys duchastelli and the indisputable members of Compsemydidae (Compsemys victa and Berruchelus russelli), but it is shared with Pleurosternon bullockii (see Pérez-García and Ortega 2011; Guerrero and Pérez-García 2020). A sutured bridge is present in all those paracryptodiran taxa.…”

“…A single lineage of freshwater stem turtles (i.e., Testudinata not belonging to the crown Testudines) is identified in the Upper Jurassic to Lower Cretaceous record of Europe: Pleurosternidae (Pérez-García 2020a). Although this lineage of Paracryptodira has been known in Europe since the first half of the 19th century, only two of the European taxa defined before the 21st century are currently identified as valid forms: Pleurosternon bullockii (Owen 1842), currently known in uppermost Jurassic (Tithonian) and lowermost Cretaceous (Berriasian) sites in Great Britain and France (Gônet et al 2018;Guerrero and Pérez-García 2020); and Dorsetochelys typocardium (Seeley 1869), identified in the lowermost Cretaceous (Berriasian) record of both Great Britain and Germany (Pérez-García 2014). However, the European diversity recognized for this Laurasian lineage has markedly increased over the last decade, through the description of three new forms in the Iberian Peninsula (Pérez-García 2017): the oldest European pleurosternid, Selenemys lusitanica Pérez-García and Ortega 2011, from the upper Kimmeridgian of the Lusitanian Basin in central-western Portugal; a taxon from the uppermost Jurassic (Tithonian) of the Spanish province of Teruel, Riodevemys inumbragigas Pérez-García, Royo-Torres and Cobos 2015a; and the youngest pleurosternid identified worldwide, Toremys cassiopeia Pérez-García, Espílez, Mampel and Alcalá 2015b, also from a site in Teruel Province, but from the uppermost Lower Cretaceous (Albian) (Pérez-García and Ortega 2011;Pérez-García et al 2015aPérez-García 2017).…”

Ontogenetic development of the European basal aquatic turtle <i>Pleurosternon bullockii</i> (Paracryptodira, Pleurosternidae)

“…Thus, all these specimens were located in the Middle Purbeck Unit (Milner, 2004), and, despite all these adults being situated in slightly more recent stratigraphic levels than that where the juveniles were found, adult specimens of this species were also recognized at older levels outside the Purbeck Limestone Group (i.e. in the Portland Group; see Guerrero and Pérez-García, 2020). Therefore, the fact that the juvenile specimens were found in a different level than the adults probably suggests that they had a different lifestyle than the adults to maintain optimal growth rates.…”