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Dentition of etmopterid shark Miroscyllium (Squaliformes) with comments on the fossil record of lanternsharks

Cybium: international journal of ichthyology (Impact Factor: 0.38). 01/2006; 30(4):305-312.

ABSTRACT Although modern lantern sharks (Etmopteridae, Squaliformes) are taxonomically diverse, their phylogenetic
relationships remain unclear. Numerous fossil etmopterids have been recently discovered, and their geologic occurrences are reviewed here. The dentition of the rare recent etmopterid M i ro s c y l l i u m s h e i k o i is described. The species shows peculiar ontogenetic changes in the morphology of lower and upper teeth, and allows to assign some fossil material described as Centroscyllium by Ledoux (1972) to Miroscyllium. Moreover, the presence, in Miroscyllium sheikoi, of a morphological transitional dental type between E t m o p t e ru s and C e n t ro s c y l l i u m, and its discovery in the fossil record allow to
propose an alternative way to contribute to the phylogenetic frameworks.

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    ABSTRACT: Deep-sea Lantern Sharks (Etmopteridae) represent the most speciose family within Dogfish Sharks (Squaliformes). We compiled an extensive DNA dataset to estimate the first molecular phylogeny of the family and to provide node age estimates for the origin and diversification for this enigmatic group. Phylogenetic inferences yielded consistent and well supported hypotheses based on 4685bp of both nuclear (RAG1) and mitochondrial genes (COI, 12S-partial 16S, tRNAVal and tRNAPhe). The monophyletic family Etmopteridae originated in the early Paleocene around the C/T boundary, and split further into four morphologically distinct lineages supporting three of the four extant genera. The exception is Etmopterus which is paraphyletic with respect to Miroscyllium. Subsequent rapid radiation within Etmopterus in the Oligocene/early Miocene was accompanied by divergent evolution of bioluminescent flank markings which morphologically characterize the four lineages. Higher squaliform interrelationships could not be satisfactorily identified, but convergent evolution of bioluminescence in Dalatiidae and Etmopteridae is supported.
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