''Guiyu oneiros'' is the earliest articulated

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

discovered. The generic name ''Guiyu'' is a transliteration of the Mandarin 鬼魚 ''guǐyú'' "

ghost A ghost is the soul or spirit of a dead person or animal that is believed to be able to appear to the living. In ghostlore, descriptions of ghosts vary widely from an invisible presence to translucent or barely visible wispy shapes, to rea ...

fish" and the specific name ''oneiros'' is from Greek ὄνειρος "dream". Fossils of ''Guiyu'' have been found in what is now

Qujing Qujing () is a prefecture-level city in the east of Yunnan province, China, bordering Guizhou province to the east and the Guangxi Zhuang Autonomous Region to the southeast; thus, it was called "Key between Yunnan and Guizhou" () and "Throat of Yu ...

Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, 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 ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, in a late

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

marine strata, about 425 million years old. ''Guiyu'' remains have been found articulated, missing only the caudal fin. The living fish is estimated to have been around 30 cm long. ''Guiyu'' was described by Chinese palaeontologist Zhu Min ( 朱敏) and others in 2009, based on a near-complete articulated specimen. It was described as a basal lobe-finned fish with anatomical features of both ray-finned and lobe-finned fishes, although, analysis of the totality of its features place it closer to the class Sarcopterygii (lobe-finned fishes). ''Guiyu'' sheds light on the early diversification of bony fishes. This clade, the osteichthyans, splits in two clades: the lobe-finned and the ray-finned (

Actinopterygii Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

) fishes. According to new data from ''Guiyu'', this split occurred during the late

period, no later than 419 million years ago (original estimate) or 425 Ma (recent estimate). ''Guiyu'' had spine-bearing

pectoral girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...

, a feature which can be found in primitive

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 ...

vertebrates. Other early bony-fish with remarkable features include ''

Andreolepis ''Andreolepis'' is an extinct genus of prehistoric fish, which lived around 420 million years ago. It was described by Walter Gross in 1968 based on scales found in the Hemse Formation in Gotland, Sweden. It is placed in the monogeneric family ...

'', '' Lophosteus'', ''

Psarolepis ''Psarolepis'' (; ''psārolepis'', from Greek ψαρός 'speckled' and λεπίς 'scale') is a genus of extinct bony fish which lived around 397 to 418 million years ago ( Pridoli to Lochkovian stages). Fossils of ''Psarolepis'' have been fou ...

'', ''

Ligulalepis ''Ligulalepis'' is an extinct genus of prehistoric bony fish. ''Ligulalepis'' was first described from isolated scales found in the Taemas-Wee jasper limestones of New South Wales (Early Devonian age) by Dr Hans-Peter Schultze (1968) and further ...

'' and '' Dialipina''. ''Guiyu'' is part of the Xiaoxiang fauna which is rich in fossils representing a marine ecosystem. Found in the late

Ludlow Ludlow () is a market town in Shropshire, England. The town is significant in the history of the Welsh Marches and in relation to Wales. It is located south of Shrewsbury and north of Hereford, on the A49 road which bypasses the town. The t ...

-aged Kuanti Formation, the remains were dated using

conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...

s as

index fossils Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bi ...

. The Xiaoxiang fauna also includes

galeaspid Galeaspida (from Latin, 'Helmet shields') is an extinct taxon of jawless marine and freshwater fish. The name is derived from ''galea'', the Latin word for ''helmet'', and refers to their massive bone shield on the head. Galeaspida lived in shallo ...

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 ...

and

acanthodians Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes), typically considered a paraphyletic group. They are currently considered to represent a grade of various fish lineages leading up to the extant Chondrichthyes, which ...

Classification

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 d ...

after the analysis of Yu ''et al.'' (2010):

Description

''Guiyu'' was covered by

ganoine Ganoine or ''ganoin'' is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars, bichirs, and coelacanths. It is composed of rod-like, pseudoprism ...

tissue, a texture that covers the scales and cranial bones as in early ray-finned fishes. The holotype specimen is about 26 cm in length and about 11 cm in depth. The head possesses about 23% of the body, and the body has a streamlined shape.

References

Prehistoric lobe-finned fish Transitional fossils Pridoli life Silurian fish of Asia Silurian China Fossils of China Paleontology in Yunnan Fossil taxa described in 2009 {{paleo-lobefinned-fish-stub