Polymorphism in Conservative Structures? The Scapulocoracoids in Skates Genus Psammobatis (Chondrichthyes, Arhynchobatidae) and the Validity of P. parvacauda

MABRAGAÑA E.; VAZQUEZ, D.M.; GABBANELLI, VALERIA; GONZALEZ-CASTRO M.; DIAZ DE ASTARLOA, JUAN M

FRONTIERS IN MARINE SCIENCE

Frontiers Media SA

Año: 2020 vol. 7 p. 1 - 9

2296-7745

Skeletal structures, especially the claspers, neurocrania, and scapulocoracoids havebeen widely used to characterize and describe new species of elasmobranchs. Intra andinterspecific variation of scapulocoracoids in 3 species of Psammobatis (n = 94) from theSouthwest Atlantic Ocean were analyzed to assess its utility as a diagnostic characterin skates. Moreover, based on scapulocoracoids and body morphometric analyses, thevalidity of Psammobatis parvacauda McEachran, 1983 was evaluated. A remarkablesexual dimorphism in scapulocoracoids was observed in all species in accordancewith original descriptions, which was also evident in the principal component (PCA)and Discriminant Analyses. The number and arrangement of post-dorsal and postventral fenestra were highly variable at intra-specific level, in contrast with originaldescriptions. Particularly, one of the morphotypes observed in females of P. normani wasidentical to the one reported in P. parvacauda. Results showed intraspecific variationin this structure, as was previously observed in Sympterygia species. Therefore, thisstructure should not be used as a diagnostic character in skates, at least for thesegenera. Regarding body morphometry the PCA showed that P. parvacauda groupedwith P. normani females and the cross-validated analysis showed that P. parvacaudawas classified in the group of P. normani females. P. parvacauda is only known from itsoriginal description (one female) and a likely second specimen, but our analyses revealeda lack of diagnostic characteristics. Based on observations and measurements of theholotype of P. parvacauda, and comparisons with congenerics, P. normani is regardeda senior synonym of P. parvacauda.