Camerate Crawfordsville Crinoid Association With Symbiotic Gastropod
Actinocrinites gibsoni, Macrocrinus mundulus (X2), Platyceras aequilateralis

Name: Crinoids - Actinocrinites gibsoni (Family Actinocrinitidae), Macrocrinus mundulus pair (Family Batocrinidae), , Gastropod - Platyceras aequilateralis

Age: Lower Mississippian Osagean Stage (345 m.y.a)

Size (25.4 mm = 1 inch): Actinocrinites: 90 mm by 55 mm with 4 mm attached stem, Macrocrinus – 40 mm by 18 mm crown with 12 mm anal tube showing and 40 mm of attached stem and 29 mm by 15 mm crown Platyceras: 35 mm by 23 mm on a 115 mm by 125mm matrix

Location: Crawfordsville, Indiana

Camerate Crawfordsville CrinoidsDescription: A fine example of pair of the Camerate crinoid Macrocrinus mundulus (Family Batocrinidae), one of which displays the elongated anal tube from the famous Crawfordsville crinoid beds. The large cronoid is a member of the Family Actinocrinitidae known as Actinocrinites gibsoni which has a gastropod known as Platyceras aequilateralis contained within its arms. These gastropods were coprophagous, presumably feeding upon the discharge from the anal pore of the crinoid. The shape of these gastropods is thought to have been influenced by the type of crinoid with which they were associated. This is one of the larger members of the genus, but the largest members were up to 8 cm long, probably too large to have lived the same sort of existence. Preservation on this specimen is remarkably complete, down to the fine pinnules on the arms, showing that it was buried quite rapidly, preserving it from the decomposition and disarticulation that usually is the fate of most echinoderms.

click crinoid pictures to enlarge

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