Hybodus

Hybodus fraasi (Brown 1900; Late Jurassic; BSPGM 1899-1-2; ~1m in length) is close to the much smaller Ozarcus. Highly ossified cartilage skeletons and tiny teeth separate hybodont sharks from many other sharks.

Hybodus basanus (Agassiz 1837; H. reticulatus (Early Jurassic skull); 2m in length, Permian –Late Cretaceous) nests between sharks and bony fish like tiny Prohalecites. This relationship was overlooked until now. Note the spines on the dorsal fins. These are homologous with spines on spiny sharks like Diplacanthus (below). Spines are transitional betwen fleshy shark fins and transparent ray fins. The skull is also transitional between sharks and bony fish, despite the presence of large gill bars (yellow) lateral to the jaws.

Agassiz L 1833, 1837 in Agassiz L. 1833-1843. Recherches sur les Poissons fossiles-I, I, III, Neuchatel, pp 1420.

Blazejowski B 2004. Shark teeth from the Lower Triassic of Spitsbergen and their histology. Polish Polar Research 25(2)153–167.

Brown C 1900. Uber das Genus Hybodus and seine systematische Stellung. Palaeontographica46: 149-174.

Duff P 1842. Sketch of the Geology of Moray. Forsyth and Young, Elgin

Maisey JG 1983. Cranial anatomy of Hybodus basanus Egerton from the Lower Cretaceous of England. American Museum Novitates 2758:1–64.

Maisey JG 1986. Anatomical revision of the fossil shark Hybodus fraasi (Chondrichthyes: Elasmobranchii). Novitates 2857:1–16.

Maisey JG 1987. Cranial Anatomy of the Lower Jurassic Shark Hybodus reticulatus
(Chondrichthyes: Elasmobranchii), with Comments on Hybodontid Systematics. American Museum Novitates 2878: 1–39.

Miller H 1841. The Old Red Sandstone. (first edition). Thomas Constable and Sons, Edinburgh.

Chondrichthyes

Ozarcus

Squalus

Rhinopristiformes