Boliviacrinus isaacsoni, a New Genus and Species of Middle Devonian Camerate Crinoid from Bolivia

Boliviacrinus isaacsoni n. gen. and sp. is only the second Devonian crinoid to be described from Bolivia. This Middle Devonian (Eifelian) species, one of the youngest members of the monocyclic camerate crinoid family Patelliocrinidae, represents an end member of a distinctly conservative lineage within a predominantly Silurian family. While the cup in Boliviacrinus isaacsoni became more complex by increasing the number of fixed brachials and interbrachials, such primitive features as relatively large, hexagonal-shaped first primibrachials and heptagonal-shaped primaxils, a clearly distinct posterior interray, and uniserial arms were retained.