AN ABNORMAL THORNBACK RAY RAJA CLAVATA WITH ADDITIONAL PECTORAL FINS

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AN ABNORMAL THORNBACK RAY RAJA CLAVATA

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AN ABNORMAL THORNBACK RAY RAJA CLAVATA WITH ADDITIONAL PECTORAL FINS J. R. ELLIS An abnormal thornback ray Raja clavata Linnaeus, 1758 was caught by long line on 9 March 2005 near the Shipwash Bank (south-east of Orford, at approximately 52º 01’N, 01º 39’E). The specimen was an immature male of 54 cm total length (36·5 cm disc width and 27 cm disc length), and weighed approximately 850 g. Two additional fins were present on the dorsal surface, each originating from the mid-line and lying on the right hand side of the fish (Figure 1a). The anterior additional fin was relatively large, and the more posterior additional fin smaller. The distance between the tip of the snout and the origin of the base of the anterior additional fin was 12 cm, and the origin of the base was 27 mm behind the spiracles. The maximum length and width of the anterior additional

Figure 1a

Figure 1b

Figure 1: Abnormal thornback ray Raja clavata showing (a) the dorsal surface with the anterior additional fin (A1), posterior additional fin (A2), and (b) xray of the specimen showing the upper jaw or palatoquadrate (Pal), lower jaw or Meckel’s cartilage (Mec), pectoral radials (p.r.), branchial arches (Bra), pectoral girdle (Pec), vertebral column (Ver), proterygium (Pro), mesopterygium (Mes) and metapterygium (Met), and with the approximate position of the additional fins marked.

Trans. Suffolk Nat. Soc. 41 (2005)


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