Cheirothricidae

Cheirothricidae [1][2][3] is a family of extinct bony fish, perhaps belonging to the Aulopiformes. They lived in the Upper Cretaceous (Cenomanian - Santonian, about 95 - 85 million years ago) and their fossil remains were found in the Middle East and Europe. They were characterized by very expanded even fins.

Cheirothricidae
Temporal range: Upper Cretaceous
Fossil of Cheirothrix species
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Aulopiformes
Family:
Cheirothricidae

Woodward, 1901

Genera

Description

The main characteristic of these small fish (the length of the body was usually between 3 and 20 centimeters in length) was given by the extreme development of the even fins; in Cheirothrix species[4] 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.

Fossil of Exocoetoides minor

Exocoetoides, on the other hand, was decidedly small in size (between 3 and 7 centimeters in length) and the pectoral fins were particularly long (they could reach the anal region); 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.

All three genera are known in the Cretaceous of Lebanon (Cheirothrix in deposits of the Santonian, the other two genera in deposits of the Cenomanian), and in Europe (Exocoetoides in Croatia and the other two in Germany).

Cheirotricides are generally considered to be representatives of the Aulopiformes; in particular, affinities have been proposed with the extinct group of Enchodontidae.

Paleobiology

Cheirothricidae had a morphology remarkably similar to that of the current 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.

Bibliography
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References
  1. Paleobiology Database
  2. GBIF
  3. Filip Pocta Rukovet palaeozoologie (1905)
  4. Karl Alfred von Zittel, Charles Rochester, Eastman, Max.Schlosser, Arthur Smith Woodward Text-book of palaeontology

Note: This article has been expanded using material based on a translation of an article from the Italian Wikipedia.

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