Pachyscyllium: a fossil catshark identified by its teeth

Pachyscyllium is a genus of fossil catsharks known chiefly from small teeth in European marine deposits. Its record is useful for reconstructing shark communities, but it does not preserve a complete animal: body length, colour and many aspects of behaviour remain unknown. The genus was formalised in 2005 after similar teeth had circulated under several older names. Because catshark teeth change from the front of the jaw to the sides, a tooth must be compared with its position and with a series of specimens. This evidence belongs with the other entries in the ancient fish catalogue.

Quick facts

Why the genus was named in 2005

Small catshark teeth had been described long before Pachyscyllium existed as a genus. In the nineteenth century, Roberto Lawley named a Tuscan fossil tooth form Scyllium dachiardii. Related material was later moved among Scyliorhinus, Premontreia and other groupings as researchers compared crowns and roots from different European deposits. The repeated changes do not mean that each tooth name represents a different animal; they reflect the difficulty of classifying isolated teeth when the rest of the jaw is absent.

Thomas Reinecke, Carsten Moths, Alistair Grant and Uwe Breitkreuz established Pachyscyllium in 2005, designating P. albigensis as its type species. The genus gathered forms that share a useful combination of crown and root characters. It also created a clearer place for species such as P. dachiardii and P. distans, although some later works retain older combinations or qualify identifications as “cf.” or “aff.” when the fossil is incomplete.

What a tooth can show

A typical tooth has a central cusp with smaller lateral cusplets, a cutting edge and a two-lobed root. Crown proportions, the presence and number of cusplets, folds near the crown base and the shape of the root groove help distinguish species. Those characters vary along the jaw. An anterior tooth can look more upright and compressed than a lateral tooth from the same shark, so a comparison based on only one position can exaggerate differences between taxa.

The Portuguese Langhian assemblage at Brielas provides a useful example of both the value and limits of isolated material. Pedro Fialho and colleagues examined 384 shark teeth from the locality and identified Pachyscyllium dachiardii among them. That occurrence added a second reported record for the species in Portuguese sediments, but it did not yield a body skeleton or direct evidence of a particular prey animal.

Species, age and geography

Published assignments place the genus in Oligocene through Pliocene deposits, with many familiar records from Miocene marine formations in Germany, Austria, Italy and Portugal. A taxon's first and last reported fossils are not necessarily the exact beginning and end of its biological existence. Those dates depend on which isolated teeth can be identified confidently and how authors treat old names such as Scyliorhinus venloensis or Scyliorhinus distans.

Revisions have treated S. venloensis as a synonym of P. dachiardii, while the history of distans has involved several generic combinations. A catalogue record therefore needs both the published name and its basis. Teeth from different beds may represent distinct species, different tooth positions, or preservational variants. The combination of crown, root and stratigraphic context matters more than resemblance at a glance.

What remains unknown

The catshark family assignment is inferred from dental anatomy; the fossil set does not preserve the cartilage skeleton, fins, skin or reproductive organs. A modern catshark may help an artist imagine a plausible outline, but it is not a direct portrait of Pachyscyllium. No robust conversion from these teeth to total body length has been established, and tooth form does not prove a fixed menu. Small prey may be plausible for a small-toothed shark, but no stomach content or feeding trace currently specifies what this genus ate.

The genus is most informative as part of a fossil assemblage. Its teeth show that catsharks occupied European seas and let researchers compare their presence across formations. Better-associated jaws or skeletal material would test how well isolated tooth species correspond to separate biological species and would make body-size estimates more defensible.

Explore related evidence in the ancient fish catalogue.