''Quasipetalichthys haikouensis'' is the type and only known species of the extinct petalichthid placoderm, ''Quasipetalichthys''. Fossil remains of ''Quasipetalichthys'' have been found in the 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 ...

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 ...

faunal stage In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convent ...

of China.

Fossils

''Quasipetalichthys'' is known primarily from two poorly preserved skulls from the

-aged Haikou Formation of

Haikou Haikou (; ), also spelled as Hoikow is the capital and most populous city of the Chinese province of Hainan. Haikou city is situated on the northern coast of Hainan, by the mouth of the Nandu River. The northern part of the city is on the ...

Kunming Kunming (; ), also known as Yunnan-Fu, is the capital and largest city of Yunnan province, China. It is the political, economic, communications and cultural centre of the province as well as the seat of the provincial government. The headqua ...

, China, where they were found in association with remains of

antiarch Antiarchi ("opposite anus") is an order of heavily armored placoderms. The antiarchs form the second-most successful group of placoderms after the arthrodires in terms of numbers of species and range of environments. The order's name was coi ...

placoderms such as ''

Bothriolepis ''Bothriolepis'' (from el, βόθρος , 'trench' and el, λεπίς 'scale') was a widespread, abundant and diverse genus of antiarch placoderms that lived during the Middle to Late Devonian period of the Paleozoic Era. Historically, ''Bot ...

sinensis'', and ''

Hunanolepis Antiarchi ("opposite anus") is an order of heavily armored placoderms. The antiarchs form the second-most successful group of placoderms after the arthrodires in terms of numbers of species and range of environments. The order's name was coin ...

''. The larger of the two skulls may have been around in length.

Phylogeny

''Q. haikouensis'' is considered a basal

petalichthyid Petalichthyida is an extinct order of small, flattened placoderm fish. They are typified by their splayed pectoral fins, exaggerated lateral spines, flattened bodies, and numerous tubercles that decorated all of the plates and scales of their ...

(though in 1978 Denison referred to it as being "aberrant"). In Zhu's 1991 redescription of ''Diandongpetalichthys'',Zhu, M. "New information on ''Diandongpetalichthys'' (Placodermi: Petalichthyida)." Early vertebrates and related problems of evolutionary biology. Science Press, Beijing (1991): 179-192. ''Quasipetalichthys'' was placed within a different family: the

Quasipetalichthyidae Quasipetalichthyidae is a family of primitive petalichthyid placoderms from Givetian-aged marine strata of Yunnan, China, and possibly Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group ...

, and was regarded as the sister group of the more advanced Macropetalichthyidae, with ''Diandongpetalichthys'' serving as the primitive sister group of these two taxa. '' Neopetalichthys'' may be very closely related to ''Quasipetalichthys'', and may or may not be placed together within Quasipetalichthyidae in a more completed phylogeny. Whether or not ''Neopetalichthys'' is included in the family, '' Eurycaraspis'' is placed in Quasipetalichthyidae as a sister taxon to''Quasipetalichthys''.

Distribution and habitat

The Haikou Formation, the only known set of rocks that has produced fossils of ''Quasipetalichthys'', appears at the earth's surface in south-central China. L. Gao. 1981. Devonian Spore Assemblages of China. Review of Paleobotany and Palynology. 34:11-23 Other paleontological investigations into these sediments have produced spores and macrofossils from Devonian plants such as the

Lycopods Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

(classified as Lycopodophyta or Lycopsida)). C. S. Li. 1990. Minarodendron cathaysiense (gen. et comb. nov.), A lycopod from the late Middle Devonian of Yunnan, China. Palaeontographica Abteilung B. 220:97-117 S. Hao, J. Xue, and Q. Wang, Z. Liu. 2007. Yuguangia ordinata gen. et sp. nov., a New Lycopsid from the Middle Devonian (Late Givetian) of Yunnan, China, and Its Phylogenetic Implications. International Journal of Plant Sciences. 168(8):1161-1175 The These plant remains often occur alongside those of Placoderms such as ''Bothriolepis'' which implies a very near-shore or freshwater environment for this geologic formation.

References

External links

''Quasipetalichthys''
at the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Paleo ...

{{Taxonbar, from=Q7269517 Fossil taxa described in 1973 Placoderms of Asia Placoderm genera Petalichthyida