Dunkleosteidae is an extinct

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

arthrodire Arthrodira (Greek for "jointed neck") is an 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 penetrating most marine eco ...

placoderms that lived during the Devonian period. The gigantic

apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

Dunkleosteus terrelli ''Dunkleosteus'' is an extinct genus of large armored, jawed fishes that existed during the Late Devonian period, about 382–358 million years ago. It consists of ten species, some of which are among the largest placoderms to have ever lived: ...

'' is the best known member of this group.

Phylogeny

While members of Dunkleosteidae were previously thought to be close relatives of the genus '' Dinichthys'' (when they were not synonymized as each other) and grouped together in the family Dinichthyidae, more recent

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

studies have shown that the two

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

represent two very distinct clades within

Arthrodira Arthrodira (Greek for "jointed neck") is an 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 penetrating most marine eco ...

. Dunkleosteidae was then established as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the family

Panxiosteidae Panxiosteidae is an extinct family of arthrodire placoderms that lived during the Devonian period. Phylogeny The family Panxiosteidae was erected by Wang in 1979. Members of the family are noted for showing morphologically intermediate traits ...

, which together comprised the superfamily

Dunkleosteoidea Dunkleosteoidea is an extinct superfamily of arthrodire placoderms that lived during the Devonian period. The gigantic apex predator ''Dunkleosteus terrelli'' is the best known member of this group. Phylogeny Eubrachythoraci is divided into th ...

(one of the three major

clades A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

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 d ...

). Dunkleosteidae was thus

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

ally defined as including the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

Dunkleosteus ''Dunkleosteus'' is an extinct genus of large armored, jawed fishes that existed during the Late Devonian period, about 382–358 million years ago. It consists of ten species, some of which are among the largest placoderms to have ever lived: ...

'' and all other genera in

more closely related to ''

'' than to '' Panxiosteus''. The

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

of Dunkleosteidae from the 2013 Zhu & Zhu study is shown in the

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below: However, the subsequent 2016 Zhu ''et al.'' study using a larger morphological dataset recovered

well outside of

, leaving the status of Dunkleosteidae as a clade grouping separate from Dunkleosteoidea in doubt, as shown in the cladogram below:

Genera

''
Dunkleosteus ''Dunkleosteus'' is an extinct genus of large armored, jawed fishes that existed during the Late Devonian period, about 382–358 million years ago. It consists of ten species, some of which are among the largest placoderms to have ever lived: ...
''

The

, ''Dunkleosteus'', is known from Late Frasnian and

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...

-aged marine strata from Europe, Morocco, and North America. The best known species, ''D. terrelli'', is famous as the "world's first vertebrate apex predator," and is estimated to be up to in length: other species, however, such as ''D. raveri'', are estimated to be in length.

'' Eastmanosteus''

''Eastmanosteous'' is a diverse genus of medium to somewhat large predatory arthrodires very similar in anatomy to the species of ''Dunkleosteus''. ''Eastmanosteus'' differs from ''Dunkleosteus'' in having a unique

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

-ornamentation on the

dermal The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided ...

surfaces of the plates, a distinctively shaped nuchal plate, and sutures that are more zigzagging. The best studied species, ''E. calliaspis'' may not be of this genus due to its recently appreciated relationship to the

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the ...

-aged genus ''Xiangshuiosteus''.

''
Golshanichthys ''Golshanichthys'' is an extinct monospecific genus of dunkleosteid from the Late Devonian: Frasnian stage from Kerman, Iran. Phylogeny ''Golshanichthys'' belongs to the family Dunkleosteidae, closely related to the giant ''Dunkleosteus''. The ...
''

Fossils of ''Golshanichthys'' are found in Frasnian-aged marine strata near Kerman,

Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...

'' Heterosteus''

''Heterosteus'' is from the middle Devonian, found in Europe and Greenland. It is one of the larger members of the family, with an estimated body length of up to .

''
Kiangyousteus ''Kiangyousteus'' is an extinct monotypic genus of dunkleosteid from the Middle Devonian: Givetian aged Guanwu Formation in the Sichuan province of south-western China. The type species, ''Kiangyousteus yohii'', was the first known arthrodire f ...
''

This

Middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...

genus represents the first arthrodire described from China. Fossils are known from the Late

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian The Frasnian is one of two faunal stages in the ...

to Early Frasnian-aged Guanwu Formation in

Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...

province.

''
Xiangshuiosteus ''Xiangshuiosteus wui'' is an extinct monospecific genus of brachythoracid arthrodire placoderm from the Late Emsian stage of the Early Devonian epoch, discovered in Wuding County of Yunnan province, China. It has recently been reassessed as a ...
''

''Xiangshuiosteus'' was originally described as an arthrodire ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'' of the Late

with anatomical features suggestive of both buchanosteids and coccosteids. With the reappraisal of ''Kiangyousteus'', it is now thought to be a dunkleosteid most closely related to ''Eastmanosteus calliaspis''.

References

{{Taxonbar, from=Q5315394 Placoderm families Early Devonian first appearances Late Devonian animals Late Devonian extinctions

Phylogeny

Genera

''Dunkleosteus ''Dunkleosteus'' is an extinct genus of large armored, jawed fishes that existed during the Late Devonian period, about 382–358 million years ago. It consists of ten species, some of which are among the largest placoderms to have ever lived: ...''