Chondrenchelyiformes is an extinct order of

holocephalan Holocephali (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fi ...

cartilaginous fish, known from the

Early Carboniferous Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

of Europe and North America. There are currently two recognised genera known from largely complete remains, ''

Chondrenchelys ''Chondrenchelys'' is an extinct genus of cartilaginous fish and the earliest member of Holocephali known from complete skeletons. ''Chondrenchelys'' would have been quite a relatively medium-sized fish with an elongated body up to in length, it ...

'' from the Visean of Scotland, and ''

Harpagofututor ''Harpagofututor'' is an extinct genus of eel-like cartilaginous fish from the Early Carboniferous ( Mississippian). It is primarily known from complete specimens discovered in the Bear Gulch Limestone of Montana, as well as an isolated tooth fr ...

'' from the

Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed ...

aged

Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich Lens (geology), geological lens in central Montana, renowned for the quality of its marine fossils from the late Mississippian (geology), Mississippian subperiod, about 324 million years ago. It is expo ...

of Montana, United States. Both genera have elongate, eel-like bodies, with their mouths having tooth plates similar to those of living

chimaera Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...

s, to which they share numerous anatomical similarities indicating a close relationship. Isolated tooth plates assigned to the genus '' Platyxystrodus'' likely belong to members of the family, which would extend the range of the group into the late Carboniferous.

Anatomy

Chondrenchelyiformes generally have elongate bodies with tapered heads, the lower jaw (mandible) is elongate, and articulates with the quadrate bone of the skull below the posteior edge of the eye socket. The dentition is composed of tooth plates, including paired plates in the upper and lower jaws (with the posterior tooth plates being larger than those further forward) , and an unpaired symphyseal plate at the front of the lower jaw. There is a long fin running along the upper body surface known as the median fin (which notably lacks a fin spine). The left and right halves of the pectoral girdle are not fused to each other. The pectoral fins are smaller in females in males, the pelvic

clasper In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's ...

of the male is elongate, and their metapterygia are robust.

References

{{Taxonbar, from=Q19832802 Holocephali Fossil taxa described in 1965 Cartilaginous fish orders