Anterior Groove Echinoid

Echinoid Upper Cretaceous

Micraster is an infaunal echinoid with a distinctive heart-shaped test (approximately 5 cm from posterior groove to anterior margin). The ambulacra are narrow and subpetaloid. The anterior ambulacrum is situated in a deep groove that leads towards the mouth. The anus is positioned on the anterior margin. Below the anus there is a small fasciole, a current-generating area that swept waste material into a sanitary tube. The mouth is on the lower surface, positioned towards the anterior margin. It is partially covered by a pronounced lip or labrum. Behind the mouth is a flattened area, the plastron. Evolutionary changes in Micraster are well documented and changes in morphology can be related to the depth of burrowing.

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  • fatima whitfoot
    How old are micraster?
    2 years ago

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