Pentremites godonii (Defrance, 1819) - fossil blastoid from the Mississippian of Indiana, USA.

This species is also referred to (incorrectly) as Pentremites godoni.

Blastoids are an extinct group of echinoderms. They resemble crinoids in having a head, or theca, perched atop a long stem of stacked columnals composed of calcite. Crinoids and blastoids are pelmatozoans - stalked echinoderms. Both groups are sessile, benthic, filter-feeding organisms. The overall structure and morphology of crinoid heads and blastoid heads are quite different. Blastoid heads have pentaradial symmetry and somewhat resemble closed flower buds or nuts. They have 5 ambulacral grooves extending outward and downward from the summit of the theca. During life, many thin, delicate brachioles extended from the ambulacral grooves - these structures captured tiny particles of food from seawater as the blastoid engaged in filter feeding.

The complete blastoid specimen shown above is associated with lace-like fenestrate bryozoans (best seen by zooming in on the matrix - click on the photo).

Classification: Animalia, Echinodermata, Blastozoa, Blastoidea, Spiraculata, Pentremitidae

Stratigraphy: Indian Springs Formation, Upper Mississippian

Locality: unrecorded/undisclosed site near the town of Sulphur, Crawford County, far-southern Indiana, USA

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