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    Review of sclerorhynchoids (chondrichthyes: bataoidea) and its phylogenetic and taxonomic implicatons

    Villalobos Segura, Eduardo (2020) Review of sclerorhynchoids (chondrichthyes: bataoidea) and its phylogenetic and taxonomic implicatons. Doctoral thesis, Birkbeck, University of London.

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    Abstract

    Recently molecular analysis shifted long-standing conceptions regarding the taxonomic and phylogenetic relationships of batoids. These changes and current phylogenetic work and classifications of fossil batoids have not been integrated. Sclerorhynchoids are one of most diverse and widely recorded clades of Cretaceous batoids whose phylogenetic relations remain undetermined. With the discovery and description of specimens of sclerorhynchoids from Morocco, the present study revaluates the phylogenetic relations of the group and proposes a new topology and rearrangement of it with respect of other batoids as a suborder of Rajiformes. These changes are contrasted with previous works. Whilst these analyses do not provide the ultimate truth regarding the phylogenetic relations of the sclerorhynchoids they represent an important steppingstone for future phylogenetic works involving fossil batoids and morphological data. With the similar composition of the major clades between molecular analyses and the present study a timescaling analyses using tip-dating, basic and minimum branch length is carried out, with the objective of stablishing a possible divergence time for sclerorhynchoids and other batoids groups. These results are compared using stratigraphic indices. Overall tip-dating presented slightly better scores. The ages estimated by the morphological data recover later divergence events than those with molecular data. Diversity curves (taxonomic diversity estimate and shareholder quorum subsampling) were used to compare the estimated ages between molecular and morphological data, this comparison resulted in morphological data presenting a better overlap with possible divergence events recovered by the diversity curves. Finally, a taxonomic update of the group is presented. A total of 30 genera and 72 valid species were found as a result of the bibliographic review. The bibliographic review revealed an uneven sampling effort between regions, which needs to be addressed, to properly establish an adequate approximation to the diversity of the group and batoids.

    Metadata

    Item Type: Thesis
    Copyright Holders: The copyright of this thesis rests with the author, who asserts his/her right to be known as such according to the Copyright Designs and Patents Act 1988. No dealing with the thesis contrary to the copyright or moral rights of the author is permitted.
    Depositing User: Acquisitions And Metadata
    Date Deposited: 13 Jul 2020 15:19
    Last Modified: 17 Jun 2021 20:08
    URI: https://eprints.bbk.ac.uk/id/eprint/40478

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