Hybodontoidae Owen, 1846

Duncan, Mags, 2004, Chondrichthyan genus Lissodus from the Lower Carboniferous of Ireland, Acta Palaeontologica Polonica 49 (3), pp. 417-428 : 419

Superfamily Hybodontoidae Owen, 1846 Family Lonchidiidae Herman, 1977 Genus Lissodus Brough, 1935

Type species: Hybodus africanus Broom, 1909 .

The diagnosis of the genus Lissodus Brough, 1935 as provided by Duffin (1985) in a revision of the genus, states that these are hybodont sharks whose teeth have small to moderately large crowns (in an extended description of the type species Lissodus africanus ( Broom, 1909) (originally Hybodus africanus ), Duffin (1985) gives an average length of the teeth as 1.2 mm), with a single low central cusp which is usually flanked by much lower lateral cusplets; the lateral margins of the crown are steeply inclined to meet with an incised root−crown interface. The lingually directed root is hybodontoid having large, simple vascular foramina with anaulacorhize organization, a central longitudinal pulp cavity occurring high up at the crown−root interface and a single row of small foramina at the upper labial roof face. A small to well−developed labial crown peg is present and may be supported by a labial root buttress in some species.

Duffin (1985) suggested that Lonchidion Estes, 1964 is a junior synonym of Lissodus and that all previously erected valid species of Lonchidion belong to Lissodus . Further he suggested that it is best to distinguish Lissodus at generic level only and if based on dental characters Lissodus transpires to deserve to become a genotype of a distinct family of hybodontiforms, then although Lissodus has priority as a genus, the family name Lonchidiidae takes priority.

The type species of Lissodus is Hybodus africanus Broom, 1909 from the Lower Triassic of the Orange Free State of South Africa. In 1935, Brough re−described the type species and assigned it to the new genus Lissodus . Duffin (1985) described a new species from the Carboniferous ( Lissodus wirkworthensis ) and reviewed the genus, which, as now understood, comprises at least twenty−one species ranging in age from Late Devonian to Cretaceous ( Duffin 2001).

A number of specimens in this paper have been assigned to the genus Lissodus on the basis of the characters described above (although not all specimens exhibit all characters). The specimens have been grouped into five morphotypes, which are not given specific names for the reasons outlined above. Since all five morphotypes are derived from the same samples (with the exception of a single specimen allocated to Morphotype 1, TCD.36764), it is probable that they are derived from a single biological species. Similarities to species proposed in the literature on the basis of a single morphotype are noted in the descriptions.