Gamerabaena is an extinct genus of baenid

Baenidae

Baenidae is an extinct family of cryptodiran turtles.-External links:* http://www.nhm.org/site/sites/default/files/dinosaur_institute/pdf/NHM_DI_proytecto_dino_Erika_Canola_Baenidae_Turtle_experience.pdf...

 turtle

Turtle

Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

 which existed in North Dakota

North Dakota

North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

 during the late Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 period. It is known from a single fragmentary skull that was found in the Maastrichtian

Maastrichtian

The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

-age Hell Creek Formation

Hell Creek Formation

The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...

. It contains the species Gamerabaena sonsalla. Gamerabaena is similar to the genus Palatobaena

Palatobaena

Palatobaena is an extinct genus of baenid turtle. It was first named by Gaffney in 1972 and the type species is Palatobaena bairdi. It based on a fragmentary skull from the Fort Union Formation of the Bighorn Basin of Wyoming. The two other species are P. gaffneyi and P...

, but it differs in its lack of a posterior expansion of the triturating (or chewing) surface, a somewhat rectangular skull, and a wide angle between the maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

e. Gamerabaena also has a lingual ridge on the inner side of the jaw that is not seen in Palatobaena.

Gamerabaena is considered the sister taxon of Palatobaena and shares features with both Palatobaena and Plesiobaena

Plesiobaena

Plesiobaena is an extinct genus of turtle which existed in the Belly River Formation, Canada during the late Cretaceous period . It was first named by Lambe, L. M. in 1972 and the type species is Plesiobaena antiqua....

. These features, which include slightly upturned eye sockets, are seen as intermediate between the two other genera. While Gamerabaena is known only from the skull, it may belong to the same species as "Baena" hayi, which is known primarily from the shell.

Phylogeny

Cladogram

Cladogram

A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 after Tyler R. Lyson and Walter G. Joyce (2009).

External links

• Gamerabaena at the Fossil Wiki.