''Squatinactis'' is a genus of extinct elasmobranch Chondrichthyes known from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

aged Bear gulch limestone in Montana. This fish was discovered in 1974 by Richard Lund. The type specimen, named CMNH 46133, consists of a

brain case In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

, poorly preserved

jaws Jaws or Jaw may refer to: Anatomy * Jaw, an opposable articulated structure at the entrance of the mouth ** Mandible, the lower jaw Arts, entertainment, and media * Jaws (James Bond), a character in ''The Spy Who Loved Me'' and ''Moonraker'' * ...

and gills, a pectoral fin, and a partial vertebral axis. This creatures most startling feature were its broad pectoral fins which resembled those 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 ( ...

s and Angel sharks ( ''Squatina''). The holotype specimen has about 15 teeth in its jaw. This creature is named after the angel shark. Teeth found in Derbyshire, England have been tentatively identified as those belonging to ''S. caudispinatus.''

Description

''Squatinactis'' had a flattened body with a set of large pectoral fins. This fish was vaguely similar to today's stingrays and angel sharks. The flins were oddly pointed forward, with a length of around two feet long. It also had a long, whip-like tail with a spine (a feature analogous to some rays) that was actually a modified, secondary dorsal fin. The snout was short and the wide mouth was equipped with a series of long conical cladodont-shaped teeth. The body was covered in a few placoid scales, but most of the surface was bare.

Classification

Because of the bizarre nature of ''Squatinactis,'' it is somewhat difficult to classify. In the original study conducted in 1974, Lund noted that the teeth of this fish are Cladodont is design, however the term "cladodont" is used to describe many Paleozoic chondrichthyeans based on their teeth and not phylogeny (including '' Cladoselache'', ''

Ctenacanthus ''Ctenacanthus'' (from el, κτείς , 'comb' and el, ἄκανθα , 'spine') is an extinct genus of ctenacanthiform chondrichthyan. Remains have been found in the Bloyd Formation in Arkansas, United States (Carboniferous period) and in Sout ...

'', and ''

Dracopristis ''Dracopristis'' is an extinct genus of ctenacanth (a group of shark-like elasmobranchs) that lived around 307 million years ago, during the Pennsylvanian sub-period of the Carboniferous period. The fish had 12 rows of short, squat teeth, and ...

''). This fish is currently classed within the Elasmobranchii, more specially in its own grouping, the Squatinactiformes.

Ecology

This fish was probably a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

predator; it probably lived half-buried in the sand and suddenly emerged to throw itself against the prey swimming nearby. The wing-like fins and long tail were most likely useful for propulsion from the seabed. The flattened body plan is typical of bottom-dwelling predators, and is known in a large number of cartilaginous fish, both

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 ...

and

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

References

{{Taxonbar, from1=Q3967456, from2=Q111036391, from3=Q111036388, from4=Q35135303 Prehistoric cartilaginous fish genera Species described in 1974 Elasmobranchii