科研之友
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摘要
Cynoclupea nelsoni gen. et sp. nov., is described from Lower Cretaceous (Barremian-Aptian) sediments of the Morro do Chaves Formation in north-eastern Brazil. Diagnostic characters of the Clupeomorpha, such as abdominal and dorsal scutes, a pre-epiotic fossa, and an otophysic connection, were identified in C. nelsoni. The presence of the recessus lateralis furthermore indicates that the species is a member of the Clupeiformes. Given the absence of odontodes covering the skull bones, which are synapomorphic to the Denticipitoidei, and the apparent presence of a postorbital branch of the supraorbital sensory canal located deep within the body of the lateral wing of the frontal, C. nelsoni is assigned to the suborder Clupeoidei. In this suborder, derived character states of the suspensorium indicate that Cynoclupea is the sister group of a Glade composed of the Chirocentridae (wolf -herrings) and Engraulidae (anchovies). The evolution of abdominal scutes and of microphagy vs. macrophagy in the Clupeoidei are discussed in light of' this hypothesis. The discovery of Cynoclupea supports not only the existence of a diversified freshwater clupeiform fauna as early as in the Barremian-Aptian, but also indicates that the divergence between the Clupeoidei and Denticipitoidei must have occurred before this interval.
- 出版日期2017-5-1
