Distinction between sympatric species of Micraster (Echinoidea) from the English Chalk
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Sympatric species of Micraster recorded from the upper Cretaceous Chalk of England are most easily distinguished from one another by the relative height of their periprocts measured from the base of the test. The observation of Gauthier (1887) and Melville (1954) that Micraster species with a high conical aboral surface (so-called 'gibbous' forms) have a lower periproct than the associated non-gibbous forms is confirmed by numerical analysis of samples from the Santonian of Kent (M. gibbus and M. coranguinum) and the upper Campanian of Norfolk (M. stolleyi and the M. schroederi-glyphus lineage). The nomenclature of the gibbous species M. gibbus and M. stolleyi is discussed.
Palaeontology - Volume 19 Part 4 Pages 689-697Palaeontology - Volume 19 Part 4 Pages 689-697
Citations
STOKES, R. B. 1976. Distinction between sympatric species of Micraster (Echinoidea) from the English Chalk. Palaeontology, 19, 4, 689–697.