Zanthopsis leachii

Zanthopsis leachii

(Desmarest, 1817)

Common name Crab
Fossil group Crustaceans
Order Decapoda
Family Zanthopsidae
Genus Zanthopsis
Taxonomic status Accepted
Geological age Ypresian

Representative Specimens

Selected reference specimens illustrating this species from different geological units and fossil sites.

Identification Examples

Choose a fossil site to view photographed reference specimens.

Summary

Zanthopsis leachii was one of the large, robust crabs of the London Clay sea. Its heavily built carapace and powerful claws suggest a bottom-dwelling animal capable of tackling a wide range of food, from small invertebrates to carrion and possibly hard-shelled prey.

A crab of this size would have been an important mid-level predator and scavenger. Its armour offered protection, but the London Clay sea also contained large fish, sharks and rays, so even a substantial crab lived in an ecosystem full of animals capable of preying on it.

Quick Identification

Look for: a large, broad and robust Zanthopsis carapace with pronounced dorsal regions and strong marginal ornament; compare spination and nodulation with Z. nodosa, Z. dufouri and Z. unispinosa.

Diagnostic Features

  • Carapace broad, robust and strongly calcified.
  • Dorsal gastric, cardiac and branchial regions are prominently expressed.
  • Lateral margins carry strong ornament and projections.
  • Overall surface is sculptured but not dominated by the nodules of Zanthopsis nodosa.
  • Species-level identification requires the full pattern of regions, margins and sculpture.

Fossil Details

Typical size
Large for a London Clay crab, with a carapace commonly several centimetres across.
Fossil material
Carapace, Claw / Chela
Preservation
Robust carapaces often survive well, but marginal spines and the frontal region can be broken. Weathering may reduce the surface relief that separates the Zanthopsis species.

Similar Species

Recorded Fossil Sites

Synonyms & Previous Names

Cancer leachii

References

  • J. S. H. Collins; C. J. T. Mellish; A. J. Ross; P. R. Crabb; S. K. Donovan. (2020). A guide to the fossil Decapoda (Crustacea: Axiidea, Anomura, Brachyura) of the British Isles. Proceedings of the Geologists' Association, 131(1), 19–50 View reference
  • Thomas Bell. (1857). A monograph of the fossil malacostracous Crustacea of Great Britain. Part I. Crustacea of the London Clay. Monograph of the Palaeontographical Society, 10, i–viii, 1–44. Palaeontographical Society, London View reference
Last Reviewed
15 August 2026 Reviewed by Sam Harris