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Thalassemys bruntrutana, a new turtle species from Late Jurassic of Switzerland (free pdf)

Ben Creisler

A new paper in open access:

Christian Püntener, Jérémy Anquetin & Jean-Paul Billon-Bruyat  (2015)
Thalassemys bruntrutana n. sp., a new coastal marine turtle from the
Late Jurassic of Porrentruy (Switzerland), and the paleobiogeography
of the Thalassemydidae.
PeerJ 3:e1282
doi:  https://dx.doi.org/10.7717/peerj.1282


Background. The Swiss Jura Mountains are a key region for Late
Jurassic eucryptodiran turtles. Already in the mid 19th century, the
Solothurn Turtle Limestone (Solothurn, NW Switzerland) yielded a great
amount of Kimmeridgian turtles that are traditionally referred to
Plesiochelyidae, Thalassemydidae, and Eurysternidae. In the past few
years, fossils of these coastal marine turtles were also abundantly
discovered in the Kimmeridgian of the Porrentruy region (NW
Switzerland). These findings include numerous sub-complete shells, out
of which we present two new specimens of Thalassemys (Thalassemydidae)
in this study.

Methods. We compare the new material from Porrentruy to the type
species Th. hugii, which is based on a well preserved specimen from
the Solothurn Turtle Limestone (Solothurn, Switzerland). In order to
improve our understanding of the paleogeographic distribution of
Thalassemys, anatomical comparisons are extended to Thalassemys
remains from other European countries, notably Germany and England.

Results. While one of the two Thalassemys specimens from Porrentruy
can be attributed to Th. hugii, the other specimen represents a new
species, Th. bruntrutana n. sp. It differs from Th. hugii by several
features: more elongated nuchal that strongly thickens
anterolaterally; wider vertebral scales; proportionally longer
plastron; broader and less inclined xiphiplastron; wider angle between
scapular process and acromion process. Our results show that Th. hugii
and Th. bruntrutana also occur simultaneously in the Kimmeridgian of
Solothurn as well as in the Kimmeridgian of England (Kimmeridge Clay).
This study is an important step towards a better understanding of the
paleobiogeographic distribution of Late Jurassic turtles in Europe.