''Desmatochelys'' (from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

δεσμός ''desmos'' 'link' + χέλῡς ''khelus'' ‘tortoise’) is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

sea turtle 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, loggerhe ...

s belonging to the family

Protostegidae Protostegidae is a family of extinct marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest, '' Archelon'', had a head long. Like most sea turtles, they had fl ...

. This genus contains two known species, ''D. lowii'' and ''D. padillai''. ''D. lowii'' was first discovered in 1895, followed by ''D. padillai'' in 2015. Having been estimated at over 120 million years old, ''D. padillai'' is currently the oldest known species of sea turtle. ''Desmatochelys'' lived during the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

, and had a wide geographic range, primarily along the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea ...

Taxonomy

The genus contains two species: * ''Desmatochelys lowi'' * ''Desmatochelys padillai'' Initially, ''Desmatochelys'' formed its own family, Desmatochelydae. Later it was reassigned into the family Protostegidae. There is some debate among the paleontological community over the placement of Protostegidae (and therefore ''Desmatochelys'') within turtle

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

. According to Elizabeth L. Nicholls, the genus should also be expanded to include closely related members that currently belong to ''

Notochelone ''Notochelone'' is an extinct genus of sea turtle, which existed about 100 million years ago.Rhinochelys''. As of 2019, ''Desmatochelys'' contains the two previously stated species, is within the family Protostegidae, and is placed along the stem of Chelonioidea - in other words, it is considered a basal turtle genus.

Discovery

''D. lowii''

The first specimen of ''Desmatochelys'' was described by

Samuel Wendell Williston Samuel Wendell Williston (July 10, 1852 – August 30, 1918) was an American educator, entomologist, and paleontologist who was the first to propose that birds developed flight cursorially (by running), rather than arboreally (by leaping from tr ...

in the Kansas University Quarterly in 1894. In his article he describes its discovery by a railroad worker near Fairbury, Nebraska. Williston was granted access to the specimen by his colleague M. A. Low, giving rise to the name ‘lowii’. This specimen was from the Late Cretaceous Benton Formation and included a nearly complete skull and lower jaw as well as pieces of the limbs, carapace, and plastron. Since first being discovered, at least five new specimens of ''D. lowii'' have been described, found in South Dakota, Kansas, Arizona, Canada, and Mexico.

''D. padillai''

The fossils of the now known as ''Desmatochelys padillai'' were discovered in the 1940s in Colombia. The first systematic study was done by Donald Thomas Jeremy Smith at

Kingston Polytechnic , mottoeng = "Through Learning We Progress" , established = – gained University Status – Kingston Technical Institute , type = Public , endowment = £2.3 m (2015) , ...

, Surrey, England. In a part of his doctoral dissertation in 1989, he suggested the specimen should be classified under the genus ''Desmatochelys''. Elizabeth L. Nicholls confirmed this classification in 1992. Due to its incomplete features and lack of information on the geological setting, the species remained undescribed at the museum of

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

. James Parham, who is one of the taxonomic authorities of the species, had seen the original fossils at Berkeley while still a PhD candidate in 1996. He recalled, "If I had known how old the specimens at Berkeley were in 1996, I would have included them in my dissertation, for sure." Better specimens were discovered in 2007 by hobby palaeontologists, Mary Luz Parra and her brothers Juan and Freddy Parra. The specimens were recovered from Villa de Leyva in Colombia. The location is within

Paja Formation Paja may refer to: * Paja, Iran, a village in Sari County * Paja (given name), a Serbian masculine name * Paja (surname) * Paja Formation, geologic formation in Colombia * Paja Brava :''Paja Brava is also used in Spanish speaking countries to ...

, which is already dated to belong to

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

, i.e., more than 120 million years old. The fossils were preserved in the collections of the Centro de Investigaciones Paleontológicas in Villa Leyva and the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham and ...

. Formal description was done by Edwin Cadena at the Senckenerg Research Institute, and James Parham at the California State University. It was discovered in Colombia with the

. This placed its age around 120 million years, making it the oldest known sea turtle, a title which was previously held by '' Santanachelys gaffneyi''. The specific name was given in honour of Carlos Bernardo Padilla, a renowned supporter of the palaeontology of the region.

Description

''Desmatochelys'' was a large sea turtle, with some specimens reaching up to 2 meters long. Members of the genus are characterized by the extended skull roof, large nasal bones, and a paddle-like humerus, as well as a distinct body shell or carapace and reduced plastron like other protostegids. Desmatochelys padillai

Specimens of ''Desmatochelys'' have been found in Nebraska, South Dakota, Kansas, Arizona, Canada, Colombia, and Mexico. They are known to have existed along the Western Interior Seaway during the Late Cretaceous, and their range may have extended to the Pacific coast. ''Desmatochelys'', like modern sea turtles, had a wide geographic distribution within the oceans. As for its stratigraphic distribution, it is generally accepted that ''Desmatochelys'' was restricted to the Cretaceous, with occurrences ranging from the

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is precede ...

to the

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. Campani ...

. Nothing is known of this turtle's reproductive strategy, with the exception of their egg development. ''Desmatochelys'' is hypothesized to have laid rigid eggs instead of the soft-shelled eggs typical of extant marine turtles, as a closely related protostegid has been shown to do. The fossils discovered in 2007 represent an almost complete skeleton. There are four skulls, two are complete and the others are nearly complete. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

consists of lower jaw, partial right

hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra. ...

, cervical vertebrae (3–8), right and left forelimbs (missing most phalanges), nearly complete carapace, left

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

and

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

, partial hyoplastron and hypoplastron. The two partial shells are badly preserved but are distinct from those of other marine turtles.

References

{{paleontology in Colombia, state=collapsed Protostegidae Prehistoric turtle genera Late Cretaceous turtles of North America Early Cretaceous reptiles of South America Fossil taxa described in 1894 Extinct turtles