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Free Content A Further Description of Gurgesiella Furvescens with Comments on the Interrelationships of Gurgesiellidae and Pseudorajidae (Pisces, Rajoidei)

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Abstract:

Additional specimens of Gurgesiella furvescens are used to supplement the original description which was based solely on the holotype. The clasper, neurocranium, pectoral girdle, and pelvic girdle of this species are described and compared with those of the only known congener, G. atlantiea, and with Pseudoraja fischeri. Comparisons support Hulley's (1972b) removal of G. atlantica from Pseudoraja to Gurgesiella. Gurgesiella and Pseudoraja share many character states which are considered to be derived within Rajoidei, negating the hypothesis that their resemblances are due to synplesiomorphies. Gurgesiella resembles Anacanthobatis and Cruriraja in clasper morphology and Anacanthobatis, Cruriraja, Raja (Rioraja) and R. (Atlantoraja) in the structure of its scapulocoracoid. The scapulocoracoid of Pseudoraja resembles those of some Psammobatis species. Both genera possess reduced rostra, that of Gurgesiella was probably derived from an ancestor with a stout or partially reduced rostrum, while the rostrum of Pseudoraja is too reduced to determine if it was derived from the Gurgesiella type or from a more slender type. However, Gurgesiella and Pseudoraja share five derived characters, which according to our present knowledge, are unique within Rajoidei. Thus, Gurgesiella and Pseudoraja appear to be a monophyletic group and their resemblances to other taxa can be explained by secondary relationships, parallelisms and retension of primitive character states. Similarities in shared derived character states implies that separate families for Gurgesiella and Pseudoraja are unwarranted and Gurgesiellidae is merged with Pseudorajidae. Pseudorajidae, Pseudoraja and Gurgesiella are redefined. The scapulocoracoid, not hitherto used in phylogenetic studies of Rajoidei, is introduced and appears to be an important taxonomic and phylogenetic character.

Document Type: Research Article

Publication date: October 1, 1979

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