Dunkleosteidae is an
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 ...
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
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 ...
placoderms that lived during the
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, whe ...
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
''Dinichthys'' (from el, δεινός , 'terrible' and el, ἰχθύς 'fish') is an extinct monospecific genus of giant, marine arthrodire placoderm from the Late Devonian (Famennian stage), comparable in size, shape, and ecological role ...
'' (when they were not
synonymized as each other) and grouped together in the family
Dinichthyidae
''Dinichthys'' (from el, δεινός , 'terrible' and el, ἰχθύς 'fish') is an extinct monospecific genus of giant, marine arthrodire placoderm from the Late Devonian (Famennian stage), comparable in size, shape, and ecological role ...
, 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
clade
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, ...
s 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 t ...
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
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 ...
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, t ...
of
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 f ...
''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 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 ...
more closely related to ''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: ...
'' 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 spec ...
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 d ...
below:[
However, the subsequent 2016 Zhu ''et al.'' study using a larger morphological dataset recovered ]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 ...
well outside of 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 ...
, 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 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 f ...
, ''Dunkleosteus'', is known from Late 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 th ...
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
''Eastmanosteus'' ("Eastman's bone") is a fossil genus of dunkleosteid placoderms. It was closely related to the giant ''Dunkleosteus'', but differed from that genus in size, in possessing a distinctive tuberculated bone ornament, a differently s ...
''
''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 in ...
surfaces of the plates, a distinctively shaped nuchal
The nape is the back of the neck. In technical anatomical/medical terminology, the nape is also called the nucha (from the Medieval Latin rendering of the Arabic , "spinal marrow"). The corresponding adjective is ''nuchal'', as in the term ''nu ...
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
Kerman ( fa, كرمان, Kermân ; also romanization of Persian, romanized as Kermun and Karmana), known in ancient times as the satrapy of Carmania, is the capital city of Kerman Province, Iran. At the 2011 census, its population was 821,394, in ...
, 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, wher ...
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 Stage. It is named after the town of Givet in Fra ...
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, uncertainty ...
'' of the Late 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 ...
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