''Heliobatis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of

stingray Stingrays are a group of sea rays, which are cartilaginous fish related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes and consist of eight families: Hexatrygonidae (sixgill stingray), Plesiobatidae ( ...

in the Myliobatiformes family Dasyatidae. At present the genus contains the single species ''Heliobatis radians''. The genus is known primarily from the

Early Eocene In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

, Wasatchian stage, Fossil Lake deposits. Fossil Lake is part of the Green River Formation in southwest Wyoming. ''Heliobatis'' is one of only two known rays to have been found in the Green River formation; the other species, Asterotrygon maloneyi, was only recognized and described in 2004.

History and classification

The genus was described from a single incomplete holotype specimen, number '' YPM 528'', currently residing in the collections of the Peabody Museum of Natural History, New Haven, Connecticut, USA. The specimen was collected from an outcrop of Fossil Lake and presents a dorsal view of the fish. It was first studied by prolific American paleontologist Othniel Charles Marsh. He published his brief 1877

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have ...

in the ''

American Journal of Science The ''American Journal of Science'' (''AJS'') is the United States of America's longest-running scientific journal, having been published continuously since its conception in 1818 by Professor Benjamin Silliman, who edited and financed it himself ...

''. Two years later

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...

, rival to Marsh, published a description for a ray specimen giving it the name ''Xiphotrygon acutidens.'' though the description by Cope is more complete and includes an illustration of his type specimen, the old name ''Heliobatis'' has seniority. In 1947

Henry Weed Fowler Henry Weed Fowler (March 23, 1878 – June 21, 1965) was an American zoologist born in Holmesburg, Pennsylvania. He studied at Stanford University under David Starr Jordan. He joined the Academy of Natural Sciences in Philadelphia and worked as ...

published a very brief description of a ray genus he dubbed ''Palaeodasybatis discus'' based on a partly restored Academy of Natural Sciences specimen, number '' ANSP 89344.'' The specimen, which was subsequently lost, was noted for having a more rounded or disc like body than ''Heliobatis.'' The genus was synonymized with ''Heliobatis'' based on illustrations of Fowler's type specimen, characterizing the more rounded appearance as an artifact of the incomplete nature of Marsh's holotype. The generic epithet ''Heliobatis'' is a derivation of the words ''

helios In ancient Greek religion and Greek mythology, mythology, Helios (; grc, , , Sun; Homeric Greek: ) is the deity, god and personification of the Sun (Solar deity). His name is also Latinized as Helius, and he is often given the epithets Hyper ...

'' meaning "the sun" and ''batis,'' meaning "skate" or "ray." The derivation of the

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''radians'' is not mentioned in Marsh's description.

Description

''Heliobatis'' ranges from in length, with an average of between . As in modern stingrays the genders are dimorphic, with males possessing claspers. ''Heliobatis'' individuals have up to three modified

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s, forming barbed stingers, on their tails, though individuals are often found with less than three. The genus is considered to have been

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

in nature. As in the modern skate genus '' Raja'' the teeth of ''Heliobatis'' are small and closely spaced. The teeth are triangular and shaped for feeding on small fish, crustaceans, and mollusks. ''Heliobatis'' is notably abundant at the same site on Fossil Lake where the only Green River Formation

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

, '' Procambarus primaevus,'' and prawns '' Bechleja rostrata'' are found. The genus has a long tail which is very slender, often missing the tip, sporting small spines along the dorsal midline. The tail provides up to half of the total body length.

References

{{Taxonbar, from=Q203710 Dasyatidae Eocene fish Fossil taxa described in 1877 Cenozoic fish of North America