Cheirothricidae


Cheirothricidae is a family of extinct marine ray-finned fish, perhaps belonging to the Aulopiformes, although they are tentatively placed as indeterminate eurypterygians. They lived during the Upper Cretaceous and their fossil remains are found in the Middle East and Europe. They were characterized by very expanded even fins.

Genera

The main characteristic of these small fish was given by the extreme development of the even fins; in Cheirothrix species the pectoral fins were particularly developed, while in Telepholis and Exocoetoides also the pelvic fins were large. In any case, the fins were large and provided with very long rays.
Cheirothrix was the largest genus, had a more robust body and could reach 20 centimeters in length; Telepholis, usually shorter and with a thinner body, had shorter pectoral fins than Exocoetoides and had some small and thin shields in the dorsal region, rounded or polygonal, adorned in the center with a tubercle. The caudal fin was not very indented. However, Telepholis may not be a cheirothricid.

Exocoetoides, on the other hand, was decidedly small in size and the pectoral fins were particularly long ; in the caudal fin both lobes were the same size.

Taxonomy and fossil record

Established in 1901 by Arthur Smith Woodward, the family Cheirothricidae was widespread in the ancient Tethys Ocean, in the areas currently occupied by the Middle East and Europe.
Two genera are known in the Cretaceous of Lebanon, and in Germany.
Members of this family are generally considered to be representatives of the Aulopiformes; in particular, affinities have been proposed with the extinct group of Enchodontidae. However, a 2009 study found them to be indeterminate members of the Eurypterygii.

Paleobiology

The Cheirothricidae had a morphology remarkably similar to that of the extant flying fishes and to that of other extinct forms like Thoracopterus. Like today's Cypselurus and Exocoetus, Cheirothricidae were also likely to perform a sort of gliding flight over water, thanks to the notable expansion of the pectoral and pelvic fins.