Xiaochelys ningchengensis: A Sinemydid Turtle from the Jehol Biota,

Sinemydid Turtles are a group of extinct Turtles known from the Middle Jurassic to the Early Cretaceous of Asia. They have traditionally been thought to be stem-group Cryptodires (i.e. more closely related to the living Cryptodires, Turtles which can fully withdraw their heads into their shells, than to the living Pleurodires, Turtles that can partially hide their heads by folding them sideways within their shells), however some recent analyses have suggested that they might in fact be stem-group Chelonians (i.e. to have split from the lineage that led to both the Cryptodires and Pleurodires before the last common ancestor of the two groups) or stem-group Sea Turtles (more closely related to living Sea Turtles than to other Cryptodires).

In a paper published in the journal Nature: Scientific Reports on 10 November 2015, Chang-Fu Zhou of the Paleontological Institute at Shenyang Normal University and Márton Rabi of the Institut für Geowissenschaften at the University of Tübingen and Department of Paleontology and MTA – ELTE Lendület Dinosaur Research Group at Eötvös Loránd University, describe a new species of Sinemydid Turtle from the Early Cretaceous Jehol Biota of Inner Mongolia.

The new species is described from a single specimen, probably a subadult, preserved as part and counterpart on a split slab and showing exeptional preservation. It is named Xiaochelys ningchengensis, where 'Xiaochelys' means 'Small Turtle' and 'ningchengensis' means 'From Ningcheng', a reference to the Ningcheng Basin, where the specimen was found.

Xiaochelys ningchengensis from the Early Cretaceous Jehol Biota (Yixian Formation) of Ningcheng, Chifeng City, Inner Mongolia, northeastern China. Zhou & Rabi (2015).

This specimen was used to carry out a phylogenetic analysis of the relationships of Sinemydid Turtles, from which Zhou and Rabi conclude that this group are in fact Crown Group Turtles (a group defined as being all living Turtles, their most recent common ancestor, and everything descended from that ancestor), and that they are more closely related to the living Cryptodires than to the living Pleurodires.

See also...

Turtle remains from the Late Miocene to Early Pliocene Black Rock Sandstone of Victoria, Australia.                                                  Australia has a diverse assemblage of Sea Turtles today, with six of the seven living Sea Turtle species found in Australian waters and one found nowhere else. The continent also has an extensive fossil record...

Turtle eggs from the Late Cretaceous of Madagascar.                                               Turtles are unique among living Amniotes (Vertebrates that can lay...

Pappochelys rosinae: A Proto-Turtle from the Middle Triassic of Badem Württemberg, Germany.                                                     Turtles have a fairly good fossil record, as would...

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A fossil Turtle from the Early Cretaceous Jehol Biota.

One of the first Vertebrate fossils described from the Jehol Biota was Manchurochelys manchoukuoensis, a Eucryptodire Turtle from the Yixian Formation of Liaoning Province, China. The first specimen of this Turtle was discovered in the early 1940s by Japanese palaeontologists working in Manchoukuo (a Japanese puppet-state in northeast China that was not widely recognised by the outside world), but subsequently lost during the Second World War.

In 2010 Chang-Fu Zhou of the Paleontological Institute at Shenyang Normal University described a new specimen of Manchurochelys manchoukuoensis from the Yixian Formation in a paper in the journal Zootaxa.

In a paper published in the journal BMC Evolutionary Biology on 5 April 2014, Chang-Fu Zhou, along with Márton Rabi of the Institut für Geowissenschaften at the University of Tübingen and the Department of Paleontology at Eötvös Loránd University and Walter Joyce of the Department of Geosciences at the University of Fribourg, describe a third specimen of Manchurochelys manchoukuoensi from the Jiufotang Formation of Qilinshan in Inner Mongolia.

The new specimen comprises the skull, the first six vertebrae, fragments of both scapulae, the proximal end of the right humerus and forepart of the shell, obtained in two blocks that were subsequently glued together during the preparation process at the Paleontological Museum of Liaoning.

New material of Manchurochelys manchoukuoensis in dorsal view, from the Early Cretaceous Jiufotang Formation of Qilinshan, Chifeng, Inner Mongolia, China. Abbreviations: c1, costal Plate 1; cs, cervical scale; ce1-4, cervical vertebrae 1-4; f, frontal; fst, foramen stapedio-temporale; hy, hyoid; m, maxilla; m1-2, marginal scales 1–2; nu, nuchal; op, opisthotic; p1-2, peripheral Plates 1–2; pa, parietal; pf, prefrontal; pm, premaxilla; po, postorbital; pro, prootic; ps1, pleural scale 1; q, quadrate; so, supraoccipital; sq, squamosal; v1, vertebral scale 1. Zhou et al. (2014).

New material of Manchurochelys manchoukuoensis in ventral view, from the Early Cretaceous Jiufotang Formation of Qilinshan, Chifeng, Inner Mongolia, China. Abbreviations: bo, basioccipital; bs, basisphenoid; cd, central depression of basisphenoid (maybe taphonomic); ce1-7, cervical vertebrae 1-7; d, dentary; ex, exoccipital; fc, fenestra caroticus; fjp, foramen jugulare posterius; h, humerus; hy, hyoid; lar, labial ridge of the triturating surface in maxilla; lir, lingual ridge of the triturating surface in maxilla; m, maxilla; nu, nuchal; op, opisthotic; p1-2, peripheral Plates 1-2; pal, palatine; pt, pterygoid; q, quadrate; s, scapula; sq, squamosal; st, stapes; XII, foramina of cranial nerve XII. Zhou et al. (2014).

See also…

 A new species of Turtle from the Late Cretaceous of Morocco.

 A Geomydid Turtle from the Miocene of Tanegashima Island, Japan.

 A Jurassic Turtle bone-bed from the far northwest of China.

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An Eucryptodiran Turtle from the Early Cretaceous of Spain

The Eucryptodiran Turtles are capable of retracting their heads completely into their shells; all modern Turtles and Tortoises fall into this group, with the exception of the Side-Necked Turtles (Pleurodira). The group originated In Europe during the Jurassic, and expanded into Asia in the Early Cretaceous, eventually spreading across the globe.

In a paper published in the journal Acta Palaeontologica Polonica on 11 May 2012, Adán Pérez−García of the Departamento de Paleontología at the Facultad de Ciencias Geológicas at the Universidad Complutense de Madrid, Marcelo de la Fuente of the Departamento de Paleontología at the Museo de Historia Natural de San Rafael, and Francisco Ortega of the Grupo de Biología at the Facultad de Ciencias at the Universidad Nacional de Educación a Distancia, describe a new, basal (i.e. from before the modern groups separated from one another) Eucryptodiran Turtle from the Early Cretaceous (Barremian) Las Hoyas Limestone of Cuenca, Spain.

Map showing the location where the new Turtle was discovered (star). Pérez−García et al. (2012).

The new turtle is named as Hoyasemys jimenezi, Jiménez's Hoya-Turtle, after Emiliano Jiménez Fuentes, an expert on Spanish fossil Turtles. In is a small (~80 mm) turtle preserved on two slabs; it is more-or-less complete, lacking only the upper portion of the skull. The deposits it comes from are interpreted as finely laminated freshwater limestones; suggesting a low energy, freshwater environment, such as a lake.

Hoyasemys jimenezi in ventral view. (A) Photograph. (B) Interpretive drawing. Pérez−García et al. (2012).

Hoyasemys jimenezi detail of skull in ventral view. (A) Photograph. (B) Interpretive drawing. Pérez−García et al. (2012).

Hoyasemys jimenezi in ventral view. (A) Photograph. (B) Interpretive drawing. Pérez−García et al. (2012).

See also A new species of Giant Side-Necked Turtle from the Palaeocene of Columbia and Reptiles on Sciency Thoughts YouTube.

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