Cranial morphology in Mollisquama sp. (Squaliformes; Dalatiidae) and patterns of cranial evolution in dalatiid sharks.

Autor: Denton JSS; Department of Vertebrate Paleontology, American Museum of Natural History, New York, NY, USA., Maisey JG; Department of Vertebrate Paleontology, American Museum of Natural History, New York, NY, USA., Grace M; NOAA/Southeast Fisheries Science Center/NMFS/Mississippi Laboratories, Pascagoula, MS, USA., Pradel A; UMR 7207 CR2P - Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université Paris, Paris, France., Doosey MH; Tulane University Biodiversity Research Institute, Belle Chasse, LA, USA., Bart HL Jr; Tulane University Biodiversity Research Institute, Belle Chasse, LA, USA., Naylor GJP; Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, Gainesville, FL, USA.
Jazyk: angličtina
Zdroj: Journal of anatomy [J Anat] 2018 Jul; Vol. 233 (1), pp. 15-32. Date of Electronic Publication: 2018 May 14.
DOI: 10.1111/joa.12823
Abstrakt: Dalatiid sharks are members of a family of predominantly small, midwater meso- and bathypelagic chondrichthyans. The family is notable for both its number of monotypic genera and high morphological disparity. Three of the seven dalatiid genera are known only from holotype specimens (Mollisquama parini) or from only a handful of specimens (Euprotomicroides zantedeschia, Heteroscymnoides marleyi), with the only detailed anatomical work consistent across all taxa being studies of dentition. Here, we present detailed anatomical description of the second-ever specimen of Mollisquama (Mollisquama sp.) covering chondrocranial, jaw, dental, and muscular anatomy, derived from a phase-contrast synchrotron microtomographic scan. Mollisquama sp. is unique among dalatiids in possessing a deep carinal process, extending ventrally from the bar between the subethmoid region and basal angle in squaloid sharks, containing a large fenestra infiltrated by the suborbitalis muscle. Mollisquama sp. also exhibits additional possibly diagnostic features, including a planar configuration of the labial cartilages and the absence of labial folds; a pad-like orbital process on the palatoquadrate; and the origination of the suborbitalis muscle solely on the carina, rather than the intraorbital wall. Character optimization of anatomical data onto a phylogeny of dalatiid sharks suggests Mollisquama sp. to be among the most specialized in the family, expanding the existing dalatiid morphospace. However, the functional significance of such transformations remains unclear. Synchrotron-derived data, which do not require chemical pretreatment of specimens, may elucidate soft-tissue functional correlates in future studies of undersampled taxa, such as dalatiids.
(© 2018 Anatomical Society.)
Databáze: MEDLINE
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