Paraorthacodus

Paraorthacodus is an extinct genus of shark. It a member of the family Paraorthacodontidae^[1][2] (though it was formerly regarded as a member of the family Palaeospinacidae^[3]), which is either placed in Hexanchiformes^[2] or in Synechodontiformes.^[1] It is known from over a dozen named species^[4] spanning from the Early Jurassic^[4] to the Paleocene,^[4] or possibly Eocene.^[3] Almost all members of the genus are exclusively known from isolated teeth, with the exception of P. jurensis from the Late Jurassic-Early Cretaceous of Europe, which is known from full body fossils from the Late Jurassic of Germany,^[5] which suggest that juveniles had a robust body with a round head, while adults had large body sizes with a fusiform profile.^[1] There was only a single dorsal fin towards the back of the body without a fin spine.^[3] The dentition had teeth with a single large central cusp along with shorter lateral cusplets,^[3] which were designed for clutching.^[1] The teeth are distinguished from those of Synechodus by the lateral cusplets decreasing in size linearly away from the central cusp rather than exponentially as in Synechodus.^[3]

Paraorthacodus Temporal range: Early Jurassic–Eocene PreꞒ Ꞓ O S D C P T J K Pg N
Paraorthacodus jurensis specimen SMNS 88987/1
Paraorthacodus jurensis specimen BSPG 1996 I 31
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Family:	†Paraorthacodontidae
Genus:	†Paraorthacodus Glückman, 1957
Species
P. andersoni P. antarcticus P. arduennae P. clarkii P. conicus P. eocaenus P. jurensis P. recurvus P. turgaicus

Taxonomy

After^[3][4]

• Paraorthacodus andersoni (Case, 1978) Late Cretaceous (Santonian and Campanian)
• Paraorthacodus antarcticus Klug et al., 2008 Late Cretaceous (Campanian)
• Paraorthacodus clarkii (Eastman, 1901) Paleocene (Thanetian)
• Paraorthacodus conicus (Davis, 1890) Late Cretaceous (Coniacian to Campanian)
• Paraorthacodus eocaenus (Leriche, 1902) Paleogene (Thanetian to Ypresian according to,^[3] exclusively Thanetian according to,^[4] considered a synonym of P. clarkii by^[6])
• Paraorthacodus jurensis (Schweizer, 1964) Late Jurassic (Kimmeridgian)
• Paraorthacodus nerviensis (Leriche, 1929) uppermost Cretaceous
• Paraorthacodus patagonicus (Ameghino, 1893) Late Cretaceous (Coniacian)
• Paraorthacodus recurvus (Trautschold, 1877) Cretaceous (Albian-uppermost Cretaceous)
• Paraorthacodus sulcatus (Davis, 1888) Late Cretaceous (Campanian)
• Paraorthacodus validus (Chapman, 1918) from the Cretaceous
• Paraorthacodus turgaicus Glickman, 1964, Paleocene (Thanetian)
• Paraorthacodus helveticus (De Beaumont 1960) Early Jurassic (Sinemurian)
• Paraorthacodus arduennae Delsate, 2001) Early Jurassic (Pliensbachian)
• Paraorthacodus kruckowi (Thies 1983) Middle Jurassic (Aalenian)