Heliobatis
Encyclopedia
Heliobatis is an extinct genus
of ray
in the Myliobatiformes
family
Dasyatidae. At present the genus contains the single species Heliobatis radians.
The genus is known primarily from the Early Eocene, 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.
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 in the American Journal of Science
. Two years later Edward Drinker Cope
, 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
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
meaning "the sun" and batis, meaning "skate" or "ray." The derivation of the specific epithet radians is not mentioned in Marsh's description.
, with males possessing claspers
. Heliobatis individuals have up to three modified dermal denticles, forming barbed stinger
s, on their tail
s, though individuals are often found with less than three. The genus is considered to have been demersal 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
, Procambarus primaevus
, and prawn
s 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.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of ray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
in the Myliobatiformes
Myliobatiformes
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived members evolved their...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Dasyatidae. At present the genus contains the single species Heliobatis radians.
The genus is known primarily from the Early Eocene, Wasatchian
Wasatchian
The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 55,400,000 to 50,300,000 years BP lasting . It is usually considered to be within the Eocene, more specifically the...
stage, Fossil Lake deposits. Fossil Lake is part of the Green River Formation
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...
in southwest Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
. Heliobatis is one of only two known rays to have been found in the Green River formation; the other species, Asterotrygon maloneyi
Asterotrygon
Asterotrygon is an extinct genus of stingray from the Eocene Green River Formation in Wyoming. Several complete skeletons representing juveniles, adults, males and females have been uncovered from the late early Eocene Fossil Butte Member of the formation. The type and only species, A. maloneyi,...
, was only recognized and described in 2004.
History and classification
The genus was described from a single incomplete holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen, number YPM 528, currently residing in the collections of the Peabody Museum of Natural History, New Haven, Connecticut
New Haven, Connecticut
New Haven is the second-largest city in Connecticut and the sixth-largest in New England. According to the 2010 Census, New Haven's population increased by 5.0% between 2000 and 2010, a rate higher than that of the State of Connecticut, and higher than that of the state's five largest cities, and...
, 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
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
. He published his brief 1877 type description in the American Journal of Science
American Journal of Science
The American Journal of Science 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
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
, 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
Henry Weed Fowler was an American zoologist born in Holmesburg, Pennsylvania.He studied at Stanford University under David Starr Jordan...
published a very brief description of a ray genus he dubbed Palaeodasybatis discus based on a partly restored Academy of Natural Sciences
Academy of Natural Sciences
The Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
specimen, number ANSP 89344
Academy of Natural Sciences
The Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
. 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
Helios
Helios was the personification of the Sun in Greek mythology. Homer often calls him simply Titan or Hyperion, while Hesiod and the Homeric Hymn separate him as a son of the Titans Hyperion and Theia or Euryphaessa and brother of the goddesses Selene, the moon, and Eos, the dawn...
meaning "the sun" and batis, meaning "skate" or "ray." The derivation of the specific epithet radians is not mentioned in Marsh's description.
Description
Heliobatis ranges from 8 to 90 cm (3.1 to 35.4 in) in length, with an average of between 30 and 40 cm (11.8 and 15.7 in). As in modern stingrays the genders are dimorphicSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, with males possessing claspers
Valva
In biology, a clasper is a male anatomical structure found some groups of animals, used in mating.Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve as intromittent organs used to channel semen into the female's cloaca during mating...
. Heliobatis individuals have up to three modified dermal denticles, forming barbed stinger
Stinger
-Biology:* Stinger, an organ or body part found in various animals that usually delivers some kind of venom.* Stinger , a minor neurological injury suffered by athletes.-Sports and entertainment:...
s, on their tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
s, though individuals are often found with less than three. The genus is considered to have been demersal in nature. As in the modern skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
genus Raja
Raja (genus)
Raja is a genus of skates in the family Rajidae, containing nearly thirty species. They are flat-bodied cartilaginous fish with a rhombic shape due to their large pectoral fins extending from or nearly from the snout to the base of their tail. Their sharp snouts produced by a cranial projection of...
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
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...
, Procambarus primaevus
Procambarus
Procambarus is a genus of crayfish in the family Cambaridae, all native to North and Central America. It includes a number of troglobitic species, and the parthenogenetic Marmorkrebs...
, and prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
s Bechleja rostrata
Bechleja
Bechleja is an extinct genus of shrimp which existed during the Eocene period. It contains four species....
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.