Rhachiosoma echinata
Rhachiosoma echinata
Summary
Rhachiosoma echinata was a strongly spined portunoid crab. It probably lived as an active bottom predator and scavenger, but its most striking feature in life would have been the defensive armour formed by the projecting spines around the carapace.
Those spines would have made the animal awkward to bite or swallow and may have discouraged some predators. It is a good example of the evolutionary contest between Eocene crustaceans developing stronger defences and the fish and other animals trying to eat them.
Quick Identification
Look for: a broad Rhachiosoma carapace with strong, extensive marginal spination; compare with R. bispinosa, where the paired principal lateral spines are the dominant feature.
Diagnostic Features
- Carapace broad and portunoid in form.
- Lateral margins are strongly and conspicuously spined.
- Spination is more extensive than the paired principal spines of Rhachiosoma bispinosa.
- Dorsal regions remain visible within the broad carapace.
- Current family placement is intentionally left unresolved; identification relies on carapace morphology rather than a forced family assignment.
Fossil Details
Similar Species
Recorded Fossil Sites
No fossil-site occurrences have yet been recorded for this species.
References
- Hiroaki Karasawa; Carrie E. Schweitzer; Rodney M. Feldmann. (2008). Revision of Portunoidea Rafinesque, 1815 (Decapoda: Brachyura) with emphasis on the fossil genera and families. Journal of Crustacean Biology, 28(1), 82–127 View reference
- 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