''Eastmanosteus'' ("Eastman's bone") is a fossil

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of dunkleosteid

placoderms Placodermi (from Greek πλάξ 'plate' and δέρμα 'skin', literally 'plate-skinned') is a class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devonian period. Their head and thorax were ...

. It was closely related to the giant ''

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: ...

'', but differed from that genus in size, in possessing a distinctive tuberculated bone ornament, a differently 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 ''n ...

plate and a more zig-zagging course of the sutures of the skull roof.http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/200812/W020090813371138329343.pdf Species of ''Eastmanosteus'' had powerful jaws with sharp cutting edges and were likely active predators. Fossils have been found in many parts of the world in marine sediments dating from the Middle to Late Devonian. They were medium-to-large fish, with specimens ''E. pustulosus'' and ''E. licharevi'' approaching a total length of 3 metres. Complete exoskeletons with soft-tissue traces of ''E. calliaspis'' from Australia make this one of the best known dunkleosteids.

Phylogeny

''Eastmanosteus'' and its relative ''

'' belong to the

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 ...

Dunkleosteidae Dunkleosteidae is an extinct family of arthrodire placoderms that lived during the Devonian period. The gigantic apex predator ''Dunkleosteus terrelli'' is the best known member of this group. Phylogeny While members of Dunkleosteidae were pr ...

. 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 ''Eastmanosteus'' can be 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: Alternatively, 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

as a clade grouping separate from Dunkleosteoidea in doubt, as shown in the cladogram below:

Species

''Eastmanosteus calliaspis'' Dennis-Bryan, 1987

From the

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 ...

Gogo Formation The Gogo Formation in the Kimberley region of Western Australia is a Lagerstätte that exhibits exceptional preservation of a Devonian reef community. The formation is named after Gogo Station, a cattle station where outcrops appear and fossil ...

of northwestern

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. This is the best known member of the genus with many articulated skulls and trunk armours in museum collections. Evidence of muscle fibres, circulatory structures and nerve tissue have been preserved representing some of the oldest known

gnathostome Gnathostomata (; from Greek: (') "jaw" + (') "mouth") are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living ...

soft tissue. The largest known skull is 272mm in length suggesting a total body length of roughly 1.5m. It was one of the largest fish in the Gogo assemblage. A reexamination of the family

posits 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 ...

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 ...

'' as ''E. calliaspis''' sister taxon, and further implicates that ''E. calliaspis'' differs enough from other members of this genus to merit placement with its own genus.

''E. licharevi'' (Obrucheva, 1956)

A poorly known species from Russia, originally described from an isolated nuchal plate from the

of Timman with additional material from the

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 ...

Lipetsk Lipetsk ( rus, links=no, Липецк, p=ˈlʲipʲɪtsk), also romanized as Lipeck, is a city and the administrative center of Lipetsk Oblast, Russia, located on the banks of the Voronezh River in the Don basin, southeast of Moscow. Populat ...

''E. lundarensis'' Hanke, Stewart and Lammers, 1996

A medium-sized species from the

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

of south-central

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Winn ...

, Canada. One of the earliest and most completely known members of the genus.

''E. magnificus'' (Hussakof & Bryant, 1918)

Based on a single almost complete head shield from the Late Devonian of New York State, US. Has previously been assigned to ''

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 ...

'' and ''Dunkleosteus''.

''E. pustulosus'' (Eastman, 1897)

This is the type species and was originally placed in the genus ''Dinichthys''. It was a large and widely distributed form, with fossil material from the Middle-Late Devonian of the USA (Wisconsin, Iowa, Michigan, New York State) and the Frasnian of Poland. Eastmanosteus pustulosus

''E. yunnanensis'' (Wang, 1982)

Originally assigned to ''Dunkleosteus''. From the Middle Devonian of

Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

Province, China.

''Eastmanosteus'' species 1 Janvier

An undescribed species based on relatively well preserved material from the Frasnian of Kerman, East

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 ...

Other species

Many other species have been included within this genus based on material from Russia, Morocco, and the United States. Most of these are either indeterminate dinichthyids or are now placed in different genera.

References

{{Taxonbar, from=Q3010127, from2=Q20072202, from3=Q25422324, from4=Q20072203 Dunkleosteidae Devonian fish of Africa Devonian fish of Asia Devonian fish of Australia Devonian fish of Europe Devonian fish of North America Placoderms of Africa Placoderms of Asia Placoderms of Australia Placoderms of Europe Placoderms of North America Middle Devonian fish Late Devonian fish Fossil taxa described in 1897 Gogo fauna Fossils of Australia Fossils of Russia Fossils of Canada Fossils of Poland Fossils of China Fossils of Iran Paleontology in Yunnan Middle Devonian genus first appearances Late Devonian genus extinctions