''Torosteus'' 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 Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

arthrodire Arthrodira (Greek for "jointed neck") is an Order (biology), order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetratin ...

placoderm Placoderms (from Ancient Greek πλάξ 'plax'', ''plakos'''Plate (animal anatomy), plate' and δέρμα 'derma'''skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Pal ...

from the Early

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during ...

stage of the

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...

period. Fossils are found in the

Kimberley Kimberly or Kimberley may refer to: Places and historical events Australia Queensland * Kimberley, Queensland, a coastal locality in the Shire of Douglas South Australia * County of Kimberley, a cadastral unit in South Australia Ta ...

region of Australia.

Description

''Torosteuss body size and

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

are similar to ''

Incisoscutum ''Incisoscutum'' is an extinct genus of arthrodire placoderm from the Early Frasnian Gogo Reef, from Late Devonian Australia. The genus contains two species ''I. ritchiei'', named after Alex Ritchie, a ichthyology, palaeoichthyologist and senior ...

'' and ''

Compagopiscis ''Compagopiscis'' is an extinct genus of placoderm known from the Gogo Formation. It lived in the Upper Devonian (Frasnian stage) of Western Australia. The genus is monotypic, with its only species being ''Compagopiscis croucheri''. Descripti ...

'', suggesting a possible

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

lifestyle, although they were on different

trophic level The trophic level of an organism is the position it occupies in a food web. Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the ...

s of their

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

. Bite force analysis has suggested that it was an active predator, and fossils have been found in numbers, suggesting possible

schooling A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of fo ...

behavior.

Phylogeny

''Torosteus'' was originally classified as a member of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Plourdosteidae. However,

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

analysis later found Plourdosteidae to be an invalid grouping, and the family was dismissed. ''Torosteus'' is now considered to be a member of the

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

Incisoscutoidea, which belongs to the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Coccosteomorphi Coccosteomorphi is an extinct clade of arthrodire placoderms within the Eubrachythoraci (of the suborder Brachythoraci), armored fish most diverse during the Devonian. Most are considered to be pelagic (open ocean) long-distance swimmers, leadin ...

, one of the two major clades within

Eubrachythoraci Eubrachythoraci is an extinct clade of arthrodire placoderms within the suborder Brachythoraci, armored fish most diverse during the Devonian. Most are considered to be pelagic (open ocean) long-distance swimmers, leading to their widespread dis ...

. 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 shows the

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

of ''Torosteus'':

References

Arthrodires {{Placoderm-stub