Quasipetalichthys
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, Givetian faunal stage of China. Fossils. "Quasipetalichthys" is known primarily from two poorly preserved skulls from the Givetian-aged Haikou Formation of Haikou, Kunming, China, where they were found in association with remains of antiarch placoderms such as "Bothriolepis sinensis", and "Hunanolepis". The larger of the two skulls may have been around in length. Phylogeny. "Q. haikouensis" is considered a basal petalichthyid (though in 1978 Denison referred to it as being "aberrant"). In  Zhu's 1991 redescription of "Diandongpetalichthys", "Quasipetalichthys" was placed within a different family: the Quasipetalichthyidae, 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. Other paleontological investigations into these sediments have produced spores and macrofossils from Devonian plants such as the Lycopods (classified as Lycopodophyta or Lycopsida)). 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.