Sphenodus
Fossil genus of fishes
From Wikipedia, the free encyclopedia
Sphenodus is an extinct genus of shark. It is placed as a member of the extinct family Orthacodontidae, which is either considered to be a member of the extinct order Synechodontiformes,[1] or the modern shark order Hexanchiformes.[2]
| Sphenodus Temporal range: | |
|---|---|
| |
| Skeleton of Sphenodus nitidus (SMNS 96844-7) from the Late Jurassic of Germany | |
 | |
| Tooth of Sphenodus nitidus | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Family: | †Orthacodontidae |
| Genus: | †Sphenodus Agassiz, 1843 |
| Type species | |
| Lamna (Sphenodus) longidens Agassiz, 1843 | |
Species classification
29 species have been described,[3] though some of these are likely synonyms, which span from the Early Jurassic (Sinemurian) to Paleocene (Danian).[2] Most species are only known from isolated teeth,[2] though the species Sphenodus macer and Sphenodus nitidus from the Late Jurassic of Germany are known from skeletons. These suggest that it was relatively large, with a body length of 2–3 metres (6.6–9.8 ft), with a fusiform body with a single dorsal fin placed posteriorly without a fin spine.[1] The teeth of Sphenodus consist of a single long, narrow central cusp, with much smaller lateral cusplets.[2] Species of Sphenodus are thought to have been actively swimming predators, eating cephalopods.[1]
A 2025 study considered Sphenodus nitidus to be a synonym of S. macer, and suggested that Sphenodus should be considered a nomen dubium. This is due to a lack of diagnostic characters associated with original type specimen teeth used to define the genus, with S. macer assigned to the new genus Archaeogracilidens which was also placed as a member of Orthacodontidae within the Hexanchiformes.[4]