''Nichollsemys'' is a genus of extinct

sea turtles Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

. The only known species is ''Nichollsemys baieri''.

Taxonomy

Biostratigraphy and paleobiogeography of Late Cretaceous chelonioids of North America

Fossils of the ''Nichollsemys'' have been found in

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

, Canada, by Donald Brinkman. The fossils found are all skulls. The name of ''Nichollsemys'' is a tribute to

Elizabeth Nicholls Elizabeth (Betsy) Laura Nicholls (January 31, 1946 – October 18, 2004) was an American-Canadian paleontology, paleontologist who specialized in Triassic marine reptiles. She was a paleontologist at the Royal Tyrrell Museum in Alberta, Cana ...

, a paleontologist from Canada who studied

marine reptiles Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...

from the

Triassic period The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

. She had previously done work with Brinkman when they found the

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

genus Pattinatator.

Evolution

Description

The full length of the ''Nichollsemys'' is unknown, but Brinkman made a chart of the length of some parts of the specimen. The length from the

basioccipital The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull this area is rough and uneven, and is joined t ...

to the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

measures 11.4 cm, the width of all the quadrates measures 9.8 cm, the depth at level of the quadrates measures 7.1 cm, the intraorbital width measures 2 cm, and the length measures 3.6 cm. Brinkman, Donald B, et al.: "Measurements of the Skull of Nichollsemys Baieri." Research Gate, Sept. 2006
/ref> The cranium has many things in common with that of

Toxochelys ''Toxochelys'' () is an extinct genus of marine turtle from the Late Cretaceous period. It is the most commonly found fossilized turtle species in the Smoky Hill Chalk, in western Kansas. Description ''Toxochelys'' was about 2 m (6 ...

: for example, they both have a rostrum basisphenoidale shaped like a rod.

References

{{Taxonbar, from=Q96286664 Prehistoric turtle genera Prehistoric turtles of North America Chelonioidea