Dercetidae

The Dercetidae are an extinct family of aulopiform ray-finned fish that are known from the Late Cretaceous to the early Paleocene (and possibly to the Eocene if Stratodus is a member).^[1][2][3] They are among the many members of the diverse, extinct suborder Enchodontoidei, which were dominant during the Cretaceous.^[4][5]

Dercetidae Temporal range: Cenomanian–Danian PreꞒ Ꞓ O S D C P T J K Pg N Possible Early Eocene record
Specimen of Dercetis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Aulopiformes
Suborder:	†Enchodontoidei
Family:	†Dercetidae Woodward, 1901
Type genus
†Dercetis Agassiz, 1834
Genera
See text

They can be distinguished by their slender appearance with an elongated snout and a prominent row of dermal scutes. Many genera evolved a very slender body plan with elongated jaws, closely converging on modern needlefish.^[2][6][7]

Taxonomy

Initially, due to their slender appearance, dercetids were classified with the spiny eels in the order Notacanthiformes, but this was only based on their superficially similar body plans. More recent research indicates that the dercetids were related to modern lizardfish and grinners.^[2]

The extinct Stratodus, possibly a dercetid, is the largest aulopiform known

The following genera are known:^[7]

• Family †Dercetidae
  • Genus †Apuliadercetis Taverne, 2006
  • Genus †Benthesikyme White & Moy-Thomas, 1940 (=Leptotrachelus von der Marck, 1863)
  • Genus †Brazilodercetis Figueiredo & Gallo, 2006
  • Genus †Candelarhynchus Vernygora et al., 2018
  • Genus †Caudadercetis Taverne, 2006
  • Genus †Cyranichthys Taverne, 1987
  • Genus †Dercetis Agassiz, 1834
  • Genus †Dercetoides Chalifa, 1989
  • Genus †Hastichthys Taverne, 1991
  • ?Genus †Kwangodercetis Casier, 1965
  • ?Genus †Leccedercetis Taverne, 2008
  • ?Genus †Paradercetis Casier, 1965
  • Genus †Nardodercetis Taverne, 2005
  • Genus †Ophidercetis Taverne, 2005
  • Genus †Pelargorhynchus von der Marck, 1858
  • Genus †Rhynchodercetis Arambourg, 1943
  • ?Genus †Scandiadercetis Taverne, 2005
  • ?Genus †Stratodus Cope, 1872

The genus Robertichthys was previously considered a dercetid, but more recent studies suggest that it was an aspidorhynchid, a member of an entirely different group of fish.^[7]

Some studies suggest that this family is paraphyletic.^[4] However, others have found it to be monophyletic.^[5][6]

Evolution

Dercetids were a dominant group of marine fish throughout the Late Cretaceous, from their appearance during the late Albian/early Cenomanian up to the very end of the Maastrichtian, when they were almost entirely wiped out by the Cretaceous-Paleogene extinction event. Only a single genus, Scandiadercetis from the Danian limestone of the Limhamns kalkbrott, Sweden, is known from the Cenozoic, shortly after the extinction event.^[5] However, if the giant Stratodus is considered a dercetid, then they may have survived until the Early Eocene of the Trans-Saharan seaway.^[3]

Ecology

At some sites such as in the Maastricht Formation, dercetid remains representing a diversity of taxa have been recovered within Lepidenteron lewesiensis, a trace fossil that likely represents the fossilized burrow of a eunicid worm. This suggests that dercetids often fell prey to these worms.^[8][9]