''Kyphosichthys'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of basal

actinopterygian Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of skin ...

bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

known from the lower

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

(Anisian) marine deposits (

Guanling Formation The Guanling Formation is a Middle Triassic (Anisian or Pelsonian in the regional chronostratigraphy) geologic Formation (geology), formation in southwestern China. Geology The formation encompasses two members. The first member is primarily c ...

) in

Luoping Luoping County () is located in Qujing City, in eastern Yunnan province, China. It borders Xingyi, Guizhou to the east, Xilin County, Guangxi Zhuang Autonomous Region to the southeast, Shizong County to the southwest, and Luliang County, Qilin ...

, eastern

Yunnan Province Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

, southwestern

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. The species is the first known fossil record of highly deep-bodied

ginglymodi Ginglymodi is a clade of ray-finned fish containing modern-day gars (Lepisosteidae) and their extinct relatives (including the family (biology), family Lepidotidae) in the Order (biology), order Lepisosteiformes, the extinct orders Semionotiforme ...

ans.

Description

''Kyphosichthys'' (

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

for "bent fish") has a strongly arched hump between the head and the dorsal fin, from which its name derives. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

measures 96 mm in

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

, and 76 mm in

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

. The greatest body height occurs at the posterior opercular margin, where the body height is over 70% of the standard length. The dorsal fin and anal fin are located far back on the body, the latter is only half as long as the dorsal fin. The pelvic fins are much smaller than the pectoral fins. The forked

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is hemi-

heterocercal Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

due to a heavy lobe extending into the dorsal lobe of the fin, but outwardly is nearly symmetrical. The body is covered in ganoid scales; those of the anterior flank are decorated with ornate ridges and tubercles while the scales further back are smoother. In describing ''Kyphosichthys'', Xu and Wu compared its body form to modern day deep-bodied fish such as the boarfish and butterflyfish (''

Chaetodon ''Chaetodon'' is a tropical fish genus in the family (biology), family Chaetodontidae. Like their relatives, they are known as "butterflyfish". This genus is by far the largest among the Chaetodontidae, with about 90 living species included here, ...

'' sp.), and inferred that ''Kyphosichthys'' was similarly a slow swimmer but highly maneuverable, likely adapted to structurally complex habitats.

Classification

When it was first described, ''Kyphosichthys'' was assigned as ''

incertae sedis or is a term used for a taxonomy (biology), 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 ...

'' within

Ginglymodi Ginglymodi is a clade of ray-finned fish containing modern-day gars (Lepisosteidae) and their extinct relatives (including the family (biology), family Lepidotidae) in the Order (biology), order Lepisosteiformes, the extinct orders Semionotiforme ...

, a group of

Holostean Holostei is a group of ray-finned bony fish. It is divided into two major clades, the Halecomorphi, represented by the single living genus, '' Amia'' with two species, the bowfins (''Amia calva'' and ''Amia ocellicauda''), as well as the Ginglymo ...

fish which includes the living

gar Gars are an ancient group of ray-finned fish in the family Lepisosteidae. They comprise seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine waters of eastern North America, Central America and Cuba ...

s as well as extinct species. A phylogenetic analysis of ''Kyphosichthys'' and other

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

neopterygians placed ''Kyphosichthys'' in an unresolved

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

with ''Lepisosteus'' (living gars) and the extinct ''

Semionotus ''Semionotus'' (from , 'mark' and , 'back') is an extinct genus of ray-finned fish found throughout Northern Pangaea (North America and Europe) during the late Triassic, becoming extinct in the Early Jurassic The Jurassic ( ) is a Geological ...

''.

Description

Classification

References

Further reading