Paragaleus tengi was previously considered to be the only member of this genus occurring in the Western Pacific, with Paragaleus randalli occurring in the Indian Ocean and allopatric in distribution. Recent molecular and morphological studies showed that P. randalli also occurs in the Western Pacific with records from Thailand, Malaysia and Indonesia previously mostly incorrectly attributed to P. tengi. This paper provides a redescription of P. tengi and confirms the presence of P. randalli from off Taiwan in the western North Pacific. These two species are morphologically very similar in appearance but differ in meristics, dentition, some coloration attributes and minor morphological characters. The conservation status of these two species needs to be reassessed based on this new information.
The eagle ray Aetobatus flagellum (Bloch & Schneider, 1801) is redescribed based on new material from the Persian Gulf (Kuwait), Indonesia and Malaysia. A related but distinct species of Aetobatus from the western North Pacific, previously referred to as A. flagellum, is reported. Aetobatus flagellum is a medium-sized eagle ray which attains about 900 mm DW; males mature at approximately 500 mm DW. Aetobatus flagellum appears to be uncommon and restricted to estuary-influenced waters of the Indo-West Pacific. It is caught as gillnet bycatch where its habit of schooling, combined with probable small litter size, may make it particularly vulnerable to impacts from fisheries.
Two modes of oviparity are known in cartilaginous fishes, (1) single oviparity where one egg case is retained in an oviduct for a short period and then deposited, quickly followed by another egg case, and (2) multiple oviparity where multiple egg cases are retained in an oviduct for a substantial period and deposited later when the embryo has developed to a large size in each case. Sarawak swellshark Cephaloscyllium sarawakensis of the family Scyliorhinidae from the South China Sea performs a new mode of oviparity, which is named "sustained single oviparity", characterized by a lengthy retention of a single egg case in an oviduct until the embryo attains a sizable length. The resulting fecundity of the Sarawak swellshark within a season is quite low, but this disadvantage is balanced by smaller body, larger neonates and quicker maturation. The Sarawak swellshark is further uniquely characterized by having glassy transparent egg cases, and this is correlated with a vivid polka-dot pattern of the embryos. Five modes of lecithotrophic (yolk-dependent) reproduction, i.e. short single oviparity, sustained single oviparity, multiple oviparity, yolk-sac viviparity of single pregnancy and yolk-sac viviparity of multiple pregnancy were discussed from an evolutionary point of view.