Comparative anatomy, phylogeny and cladistic classification of the order Orectolobiformes (Chondrichthyes, Elasmobranchii)

Phylogenetic relationships of the order Orectolobiformes were analyzed cladistically on the basis of comparative morphology of external features, skeleton, musculature, and sensory system. The order Orectolobiformes is a monophyletic lineage united by two synapomorphies : foramen for the ophthalmicus profundus fused with that for the ophthalmicus superficialis, and prominent inner process present on ceratobranchial. A comparison of 22 orectolobiform fishes resulted in six most parsimonious cladograms reconstructed on the basis of 136 characters. The order Orectolobiformes is additionally supported by 17 apomorphies. Parascyllium and Cirrhoscyllhim constitute a monophyletic group within Orectolobiformes supported by 41 apomorphies forming the suborder Parascylloidei and the family Parascylliidae. The other clade is supported by 24 apomorphies forming the suborder Orectoloboidei, and is divided into four succeeding clades. Brachaelitrus is supported by eight apomorphies to be ranked in the family Brachaeluridae. Orectolobus, Sutorectus and Eucrossorhinus are supported by 16 apomorphies to be ranked in the family Orectolobidae, and synonymized in the genus Orectolobus based on the relationships. Hemiscyllium and ChiloscyIlium form the family Hemiscylliidae supported by 13 apomorphies. Stegostoma, Ginglymostoma and Rhincodon are supported by 23 apomorphies and are ranked in the family Rhincodontidae including two incertae genera of Pseudoginglymostoma and Nebrius. Evolution of reproduction mode is proposed on the basis of the interrelationships. The common ancestor of Orectolobiformes had extended oviparity, and the ancestor of Orectoloboidei succeedingly acquired retained oviparity. Yolksac vivtparity occurred in ancestors of the orectolobid-brachaelurid and Rhincodon-Ginglymostoma lineages, respectively, and extended oviparity was acquired secondarily in the ancestor of Hemiscylliidae.