''Heintzichthys'' 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 ...

monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

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 ...

that lived what is now

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

during the

Famennian The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...

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. The

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

was discovered in the

Cleveland Shale The Cleveland Shale, also referred to as the Cleveland Member of the Ohio Shale, is a Late Devonian (Famennian) shale Member (geology), geologic member in the eastern United States. Identification and name The Cleveland Shale was identified in ...

near

Cleveland Cleveland is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located along the southern shore of Lake Erie, it is situated across the Canada–U.S. maritime border and approximately west of the Ohio-Pennsylvania st ...

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

, in the United States.

Phylogeny

''Heintzichthys'' is 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 ...

Selenosteidae Selenosteidae is an extinct family of small to large-sized arthrodire placoderms from the Late Devonian. With the exception of the Chinese '' Phymosteus'', selenosteids lived in shallow seas in what is now Eastern North America (the Cleveland S ...

of 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 ...

Aspinothoracidi Aspinothoracidi is a clade of placoderms, extinct armored fish most diverse during the Devonian. The gigantic apex predator ''Dinichthys'', is the best-known member of this group. Many other genera, such as the infamous ''Dunkleosteus'', were pre ...

, which belongs to the clade

Pachyosteomorphi Pachyosteomorphi 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, leadi ...

, 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 ''Heintzichthys'': According to a 2022 Jobbins ''et al.'' study, ''Heintzichthys'' was found to be a sister taxa to ''

Gorgonichthys ''Gorgonichthys'' is extinct monospecific genus of large arthrodire placoderm. Fossils are found in the Upper Famennian Cleveland Shales of Late Devonian in Ohio. The type species is ''Gorgonichthys clarki''. Description ''Gorgonichthys'' had ...

''. {{Clade, style={{Clade , 1=''

Gymnotrachelus ''Gymnotrachelus'' is an extinct monospecific genus of large selenosteid arthrodire placoderm of the Late Devonian known from the Late Famennian Cleveland Shale of Ohio. The type species is ''Gymnotrachelus hydei''. Phylogeny ''Gymnotrachelus'' ...

'' , 2={{Clade , 1=''

'' , 2=''Heintzichthys''

References

{{Reflist {{Arthrodira, E. {{Taxonbar, from=Q21078591, from2=Q16937211 Selenosteidae Arthrodire genera Placoderms of Europe Placoderms of North America Late Devonian animals {{Placoderm-stub