Brychaetus muelleri

Brychaetus muelleri

Woodward, 1901

Common name Bony tongue
Fossil group Bony Fish
Order Osteoglossiformes
Family Osteoglossidae
Genus Brychaetus
Taxonomic status Accepted
Geological age Ypresian

Summary

Brychaetus muelleri was a large predatory bonytongue and one of the more impressive teleosts of the London Clay. Its skull could exceed several tens of centimetres and carried broad-based, enamel-tipped teeth, while large heavy scales protected the body. The combination indicates a substantial fish capable of taking sizeable prey rather than a small plankton feeder.

Its ecology is inferred from this robust cranial and dental equipment and from osteoglossid relationships. It was probably an active predator of fishes and other relatively large prey in coastal or shelf waters. Three-dimensional skulls, isolated teeth and large scales provide unusually tangible evidence for both its size and feeding apparatus.

Quick Identification

Look for: very large cranial pieces or scales associated with broad-based pointed teeth; skull bones show coarse fibrous or radiating ornament, and complete heads have a long snout, large operculum and strongly ossified sclerotic ring.

Diagnostic Features

  • Teeth are robust, broad-based and terminate in a hard enamelled point.
  • Dermal skull bones carry coarse fibrous or radiating surface ornament.
  • Large body scales are thick, broad and strongly ossified.
  • Anterior skull bears three approximately parallel longitudinal ridges where preserved.
  • Operculum is very large and plate-like behind the cheek region.

Fossil Details

Preservation
London Clay fish skulls are commonly incomplete, compressed, pyritised or enclosed in concretions. Thin cranial margins and projecting processes are easily lost, and separated bones can be difficult to orient; species-level identification is strongest when several adjoining diagnostic bones are preserved together.

Recorded Fossil Sites

References

  • Casier, E. (1966). Faune ichthyologique du London Clay. 496 pp.. Trustees of the British Museum (Natural History), London View reference
  • Friedman, M.; Beckett, H. T.; Close, R. A.; Johanson, Z. (2016). The English Chalk and London Clay: two remarkable British bony fish Lagerstätten. Geological Society, London, Special Publications, 430(1), 165–200. Geological Society of London, London View reference
Last Reviewed
20 August 2026 Reviewed by Sam Harris