The relationships of certain Upper Cretaceous Teleosts with special reference to the Myctophoids

Abstract

SYNOPSISRedescriptions are given of most of the genera contained in Woodward's (1901) families Enchodontidae, Dercetidae and Scopelidae. Four new suborders are erected within the order Salmoniformes, the Ichthyotringoidei, Cimolichthyoidei, Enchodontoidei and Halecoidei. The Ichthyotringoidei contains two families, the Ichthyotringidae and the new family Apateopholidae. The Cimolichthyoidei contains the Dercetidae and the new family Cimolichthyidae, with a third new family appended, the Prionolepididae. The Enchodontoidei is composed of two families, Enchodontidae and the new family Eurypholidae. The Halecoidei contains the single family Halecidae. A new family Sardinioididae is added to the Myctophiformes and a new genus, Patter sonichthys , is included within the ctenothrissiform family Aulolepidae. Each group is discussed in relation to its systematic position and the information gained is used in an overall consideration of the evolution of the teleosts in the Cretaceous. I. Genus CIMOLICHTHYS Leidy, 1857 Diagnosis (emended). Cimolichthyidae in which the head is somewhat elongated with an acutely pointed anterior region. Palatine with two longitudinal rows of teeth, only innermost row barbed. Ectopterygoid teeth also barbed. Dentary with 3 distinct rows of teeth. Dorsal fin short, mid-way along the back, consisting of 16 rays. Anal fin shorter with 11 rays and remote in position. Type species. Cimolichthys levesiensis Leidy. Remarks. The genus was originally erected by Leidy (1857) when he proposed the type species Cimolichthys levesiensis, based on palatine and ectopterygoid material showing the characteristic barbed teeth. Cimolichthys levesiensis Leidy (Text-figs. 16-21)

A fossil assemblage from the mid–late Maastrichtian of Gavdos Island, Greece, provides insights into the pre-extinction pelagic ichthyofaunas of the Tethys

“…We recognize clear similarities—not synapomorphies—between this material and members of †Enchodontidae: i) presence of a single fang on the dermopalatine; ii) ectopterygoid bearing between six to eight sparsely arranged teeth; iii) lower jaw with low coronoid process; iv) presence of a long near-symphyseal fang on mandible; v) striated ornamentation of the lateral surface of the mandible (see e.g., [ 12 , 13 , 18 , 19 , 21 , 66 – 69 ]). The morphology of the dermopalatine and its teeth, and to a lesser degree, that of the ectopterygoid and lower jaw bones and fangs are historically treated as a basis for distinguishing among different species of †enchodontids, even when fragmentary remains are considered (e.g., [ 13 , 18 , 19 , 21 , 66 , 67 ]). This approach, especially in the case of latest Cretaceous occurrences, has led to the possible lumping of †enchodontid species under the commonly recognized genus † Enchodus [ 21 ].…”

“…The fossil described herein presents two striking anatomical similarities with †enchodontoid aulopiforms: i) presence of a single palatine fang; ii) presence of a horizontal crest of the opercle [ 21 , 66 – 68 ]. A single dermopalatine fang was also described in † Rharbichthys [ 73 , 74 ] and the †dercetid † Ophidercetis [ 75 ], while a horizontal crest on the opercle is a common feature of other aulopiforms, such as †‘ichthyotringoids’ [ 66 , 68 ]. However, a combination of these two characters is only found in members of †Enchodontidae [ 66 – 70 , 76 ] and points towards the inclusion of this peculiar fish from Gavdos within the family.…”

“…A single dermopalatine fang was also described in † Rharbichthys [ 73 , 74 ] and the †dercetid † Ophidercetis [ 75 ], while a horizontal crest on the opercle is a common feature of other aulopiforms, such as †‘ichthyotringoids’ [ 66 , 68 ]. However, a combination of these two characters is only found in members of †Enchodontidae [ 66 – 70 , 76 ] and points towards the inclusion of this peculiar fish from Gavdos within the family. The closely spaced, saw-like dentition of the fossil in question differs from that of other †enchodontids from Gavdos [ 21 ], or any other known †enchodontid [ 66 , 67 , 69 , 70 , 76 – 78 ].…”

“…However, a combination of these two characters is only found in members of †Enchodontidae [ 66 – 70 , 76 ] and points towards the inclusion of this peculiar fish from Gavdos within the family. The closely spaced, saw-like dentition of the fossil in question differs from that of other †enchodontids from Gavdos [ 21 ], or any other known †enchodontid [ 66 , 67 , 69 , 70 , 76 – 78 ]. It should, thus, be accommodated in a new genus and species.…”

“…Due to its anatomical incompleteness, † Calypsoichthys cannot be extensively scored and analyzed phylogenetically, but its preserved aspects can support a preliminary discussion of its affinities through a comparison with known †enchodontid genera. The presence of a single large fang on the palatine characterizes most †Enchodontidae [ 21 , 66 – 68 ], to the exclusion of the basally diverging (sensu [ 70 ]) † Unicachichthys (which bears multiple small teeth and small fangs, [ 77 ]), † Veridagon (which bears two fangs, [ 69 ]), and possibly the †eurypholin † Vegrandichthys (it likely bears more than one dermopalatine tooth [ 70 ]). Amongst more derived †enchodontids, we note similarities in the ridged ornamentation of the lower jaw bones of † Calypsoichthys with †enchodontins—such as † Enchodus [ 21 , 66 , 67 ].…”