''Cosmoselachus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of symmoriiform chondrichthyan from the Upper

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

( Mississippian subperiod) aged

Fayetteville Shale The Fayetteville Shale is a geologic formation (geology), formation of Mississippian age (354–323 million years ago) composed of tight shale within the Arkoma Basin of Arkansas and Oklahoma. It is named for the city of Fayetteville, Arkansas, an ...

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

, United States. The genus contains a single species, ''C. mehlingi'', which is known from a partial specimen that includes the cranium, jaws, gill arches, pectoral fins, and teeth.

Discovery and naming

The ''Cosmoselachus''

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

specimen, AMNH FF 20509, was discovered in 1979 in sediments of the

near Cove Creek in Searcy County,

, United States. Since its discovery, the specimen has been damaged and it has experienced pyrite decay while in storage at AMNH. The fossil consists of the nearly complete lower jaws with teeth, a partial upper jaw and basicranium,

gill arch Branchial arches or gill arches are a series of paired bony/ cartilaginous "loops" behind the throat ( pharyngeal cavity) of fish, which support the fish gills. As chordates, all vertebrate embryos develop pharyngeal arches, though the event ...

elements, cartilage from a partial

pectoral girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans, it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists o ...

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s and fin impressions. In 2024, Allison Bronson and others described ''Cosmoselachus mehlingi'' as a new genus and species of shark-like cartilaginous fish based on these fossil remains. The generic name, "''Cosmoselachus''", combines "Cosm", the nickname of AMNH museum specialist Carl Mehling, with the

Greek Greek may refer to: 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 of all kno ...

"σέλαχος" ("''selachos''"), which refers to cartilaginous fish. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''mehlingi''", honors Carl Mehling and his paleontological contributions.

Classification

In their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, Bronson et al.recovered ''Cosmoselachus'' a falcatid member of the order

Symmoriiformes Symmoriiformes is an extinct order of cartilaginous fish. Originally named Symmoriida by Zangerl (1981), the name has since been corrected to Symmoriiformes to avoid confusion with a family. The symmoriiform fossils record begins during the late ...

. This clade was recovered outside of the

Holocephali Holocephali (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fi ...

, contrasting with some other studies. Their results are shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

References

{{Taxonbar, from=Q124782515 Symmoriiformes Carboniferous cartilaginous fish Mississippian fish of North America Fossil taxa described in 2024