Kionaster petersonae, n. gen. and sp. (Asteroidea), the first fossil occurrence of the Asterodiscididae, from the Miocene of Florida

Abstract

Kionaster petersonae, n. gen. and sp., from the Miocene Chipola Formation of Florida, is the first-known fossil member of the extant family Asterodiscididae Rowe. Although abactinal and marginal expressions clearly serve to distinguish the Asterodiscididae, the family was recognized only relatively recently, in part perhaps because assigned genera are few and these occur in traditionally less heavily collected areas. The original inferred presence of reduced numbers of marginal ossicles in the family is rejected. Phylogenetic analysis suggests close affinities between asterodiscidids and Goniaster L. Agassiz, 1836 (Goniasteridae). Kionaster appears closest to the eastern Pacific asterodiscidids rather than Asterodiscides itself, which is widely distributed farther west in the Pacific. Distinctive characters of Kionaster suggest a once-greater diversity within the family. Although data are limited, morphologic similarities and biogeographic distributions suggest familial origin in a low-latitude Western Hemisphere setting and the Atlantic Ocean prior to the closing of the Isthmus of Panama.