''Denazinemys'' was a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

baenid Baenidae is an extinct family of paracryptodiran turtles known from the Early Cretaceous to Eocene of North America. While during the Early Cretaceous they are found across North America, during the Late Cretaceous they are only found in Laramidi ...

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

that lived in the present-day

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. The type and only known species is ''D. nodosa''.

History of discovery

The

holotype specimen A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was Species description, formally described. It is either the single such physical example (or illus ...

, which ''D. nodosa'' was based on, USNM 8345, consists of a partial

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

and

plastron The turtle shell is a shield for the ventral and dorsal parts of turtles (the Order (biology), order Testudines), completely enclosing all the turtle's vital organs and in some cases even the head. It is constructed of modified bony elements such ...

from the upper

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

-aged

Kirtland Formation The Kirtland Formation (originally the Kirtland Shale) is a Sedimentary rock, sedimentary geological formation. Description The Kirtland Formation is the product of alluvial muds and overbank sand deposits from the many channels draining the ...

. Numerous shell fragments from various formations were also assigned to ''Denazinemys nodosa'', based on the welted structure of the shell surface. However, with the exception of relatively complete specimens from the

Fruitland Formation The Fruitland Formation is a geologic formation found in the San Juan Basin in the states of New Mexico and Colorado, in the United States of America. It contains fossils dating it to the Campanian age of the late Cretaceous.

and the

Kaiparowits Formation The Kaiparowits Formation is a sedimentary geological formation, rock formation found in the Kaiparowits Plateau in Grand Staircase–Escalante National Monument, in the southern part of Utah in the western United States. It is over 2800 feet (8 ...

, Spicher et al. (2023) questioned the attributed specimens from other formations, as they are too fragmentary to distinguish differences in the structure of the welted shell surface. As it is not yet possible to identify these fragments precisely (several species of Baenidae having this same feature on their shell surface), the researchers restricted ''Denazinemys nodosa'' to the Upper Campanian. In 2025, other specimens assigned to ''D. nodosa'' have been reported from the

Aguja Formation The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered ...

and the

Javelina Formation The Javelina Formation is a geological formation in Texas. Dating has shown that the strata date to the Maastrichtian stage of the Late Cretaceous, approximately 70 to 66.5 million years old. The middle part of the formation has been dated to ab ...

Description

Previously, '' Scabremys ornata'' was assigned to ''Denazinemys'' as ''D. ornata''. Below are the features found in ''Denazinemys'' distinguishing the two genera: * a

that is sub-triangular with widest dimension

posteriorly Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

; * prepleurals present and touching the first

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

medially Medial may refer to: Mathematics * Medial magma, a mathematical identity in algebra Geometry * Medial axis, in geometry the set of all points having more than one closest point on an object's boundary * Medial graph, another graph that repr ...

; * the first vertebrae an irregular hexagonal shape with the greatest width posteriorly, contacting

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

second vertebrae; * extracervicals

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

to the primary cervicals, the cervicals being sub-divided; * and carapace nodes irregular and not forming distinct ridges.

Classification

''Denazinemys'' is a

along with ''

Plesiobaena ''Plesiobaena'' is an extinct genus of turtle which existed in the Belly River Formation, Canada during the late Cretaceous period (Campanian age). It was first named by Lawrence Lambe Lawrence Morris Lambe (August 27, 1863 – March 12, 1919 ...

'', ''

Boremys ''Boremys'' is an extinct genus of baenid turtle from the Late Cretaceous and early Paleocene of North America. Naming and description It is known from two species, the first being ''B. pulchra'' named in 1906 by Lawrence M. Lambe for a parti ...

'', ''Scabremys'', ''

Baena Baena is a town and municipalities in Spain, municipality of Spain located in the Córdoba Province, Spain, province of Córdoba, Andalusia. It is situated near the on the slope of a hill southeast of Córdoba, Spain, Córdoba by road. The popu ...

'' and ''

Chisternon ''Chisternon'' is a genus of baenid turtles from the Eocene of North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the ...

''. Below is a cladogram made by Sullivan ''et al.'' in 2013 showing the relations of ''Denazinemys'': (note: ''Boremys pulchra'' is partly a junior synonym of ''Boremys grandis'')

References

{{Taxonbar, from=Q15738349 Baenidae Late Cretaceous turtles of North America Kaiparowits Formation Fossil taxa described in 2006