Squatinactis

Squatinactis
Temporal range: Serpukhovian to Namurian
Squatinactis NT small.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Squatinactiformes
Zangerl, 1981
Family: Squatinactidae
Cappetta et al., 1993
Genus: Squatinactis
Lund and Zangerl, 1974
Species:
S. caudispinatus
Binomial name
Squatinactis caudispinatus
Lund and Zangerl, 1974

Squatinactis is a genus of extinct elasmobranch Chondrichthyes known from the Carboniferous 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, poorly preserved jaws and gills, a pectoral fin, and a partial vertebral axis. This creatures most startling feature were its broad pectoral fins which resembled those of Stingrays 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, and Dracopristis). This fish is currently classed within the Elasmobranchii, more specially in its own grouping, the Squatinactiformes.

Elasmobranchii

Thrinacoselache

Doliodus

Cladoselache

Squatinactis

Triodus

Orthacanthus

Dracopristis

Ctenacanthus

Homalodontus

Hopleacanthus

Wodnika

Tristychius

Surcaudalus

Bandringa

Sphenacanthus

Gansuselache

Onychoselache

Hamiltonicthys

Phylogenetic position of D. hoffmanorum as reconstructed by Hodnett & Grogan 2021.[citation needed]

Ecology

This fish was probably a benthic 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 and extant.


This page was last updated at 2023-02-12 07:04 UTC. Update now. View original page.

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