| Heterosteus | |
|---|---|
 | |
| Life reconstruction ofHeterosteus ingens | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | †Placodermi |
| Order: | †Arthrodira |
| Suborder: | †Brachythoraci |
| Family: | †Heterosteidae |
| Genus: | †Heterosteus Asmuss, 1856 |
| Species | |
| Synonyms | |
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Heterosteus (also known asHeterostius[1][2]) is anextinctgenus ofheterosteidplacoderm of theMiddle Devonian known from remains discovered inEurope andGreenland. According to Denison, 1978, Heterosteus might have beenplanktivorous, along withHomosteus, andTitanichthys.[3]
Heterosteus was originallydescribed in 1837 as species ofTrionyx, a softshelled turtle.[4] Also in later studies it was often misidentified and given names likeIchthyosauroides,Asterolepis asmussi andChelonichthys asmusii.[1] Even in recent studies, it is controversial as to whether to use genus nameHeterosteus orHeterostius. According toInternational Code of Zoological Nomenclature, suffix ‘-ostius’ inscientific name should not be corrected as ‘-osteus’, so some studies use the genus nameHeterostius.[1]
This genus includes the largest species in the family, and are among the largestarthrodires, as well, with the type species,H. asmussi, having an estimated body length of up to 6 metres (19 ft 8 in).[5] The genus differs fromHerasmius by having the orbits on slightly longer eyestalk-like projections. The various species are found inGivetian-aged deposits in Europe and Greenland. With the except of the GermanH. rhenanus, all species are known from freshwater deposits:H. rhenanus is based on fragments found in a marine deposit.
Heterosteus is thetype genus for thefamilyHeterosteidae, which belongs to thesuperfamilyDunkleosteoidea. It is a relative of the giantDunkleosteus, as shown in thecladogram below:[1]
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