Hemiaster bowerbanki
Hemiaster bowerbanki
Summary
Hemiaster bowerbanki was an irregular, heart-urchin type echinoid that lived on or within soft marine sediment. Like living spatangoids, its body was enclosed in a rigid calcitic test but its bilateral, heart-shaped form was adapted for moving through mud rather than grazing over hard surfaces.
Its likely ecological role was that of a deposit feeder, using tube feet and spines to move sediment and collect organic particles. London Clay specimens may be represented by tests, test fragments and spines.
Quick Identification
Look for: a heart-shaped, bilaterally symmetrical sea-urchin test with a distinct front-to-back axis, petal-like ambulacral areas on the upper surface and a depressed or notched anterior margin; isolated plates alone are rarely enough for secure species identification.
Diagnostic Features
- Test irregular and distinctly bilaterally symmetrical rather than radially circular.
- Overall outline heart-shaped to ovate with a differentiated anterior end.
- Paired ambulacra form petaloid areas on the aboral surface.
- Anterior ambulacrum lies in a shallow frontal depression or sulcus.
- Tubercles are relatively fine compared with the large primary tubercles of regular echinoids.
Fossil Details
Recorded Fossil Sites
No fossil-site occurrences have yet been recorded for this species.
References
- Forbes, E. (1852). Monograph of the Echinodermata of the British Tertiaries. Palaeontographical Society Monograph View reference