<Li> † Order Menaspiformes </Li> <Li> † Order Cochliodontiformes Obručhev 1953 </Li> <Li> Order Chimaeriformes Berg 1940 sensu Obručhev 1953 (chimaeras) </Li> <Li> Subclass Elasmobranchii <Ul> <Li> † Plesioselachus </Li> <Li> † Order Antarctilamniformes Ginter, Liao & Valenzuela - Rios 2008 </Li> <Li> † Order Elegestolepidiformes Andreev et al. 2016 </Li> <Li> † Order Lugalepidida Karatajute - Talimaa 1997 </Li> <Li> † Order Squatinactiformes Zangerl 1981 </Li> <Li> † Order Protacrodontiformes Zangerl 1981 </Li> <Li> † Infraclass Cladoselachimorpha <Ul> <Li> † Order Cladoselachiformes Dean 1909 </Li> </Ul> </Li> <Li> † Infraclass Xenacanthimorpha Berg 1940 <Ul> <Li> † Order Bransonelliformes Hampe & Ivanov 2007 </Li> <Li> † Order Xenacanthiformes Berg 1940 </Li> </Ul> </Li> <Li> Infraclass Euselachii (sharks and rays) <Ul> <Li> † Order Altholepidiformes Andreev et al. 2015 </Li> <Li> † Order Polymerolepidiformes </Li> <Li> † Order Ptychodontiformes </Li> <Li> † Order Ctenacanthiformes Zangerl 1981 </Li> <Li> † Division Hybodonta <Ul> <Li> † Order Hybodontiformes Owen 1846 </Li> </Ul> </Li> <Li> Division Neoselachii Compagno 1977 <Ul> <Li> Subdivision Selachii (modern sharks) <Ul> <Li> Superorder Galeomorphi Compagno 1977 <Ul> <Li> Order Heterodontiformes (bullhead sharks) </Li> <Li> Order Orectolobiformes (carpet sharks) </Li> <Li> Order Lamniformes (mackerel sharks) </Li> <Li> Order Carcharhiniformes (ground sharks) </Li> </Ul> </Li> <Li> Superorder Squalomorphi <Ul> <Li> Order Chlamydoselachiformes </Li> <Li> Order Hexanchiformes (frilled and cow sharks) </Li> <Li> Order Squaliformes (dogfish sharks) </Li> <Li> † Order Protospinaciformes </Li> <Li> † Order Synechodontiformes </Li> <Li> Order Squatiniformes (angel sharks) </Li> <Li> Order Pristiophoriformes (sawsharks) </Li> </Ul> </Li> </Ul> </Li> <Li> Subdivision Batoidea (rays) <Ul> <Li> Order Torpediniformes (electric rays) </Li> <Li> Order Pristiformes (sawfishes) </Li> <Li> Order Rajiformes (skates and guitarfishes) </Li> <Li> Order Myliobatiformes (stingrays and relatives) </Li> </Ul> </Li> </Ul> </Li> </Ul> </Li> </Ul> </Li>

What is the study of sharks and rays called