Unusual ambulacral branching pattern in a new Ordovician giant edrioasteroid, Bizarroglobus.

An unusual, new, giant edrioasteroid Bizarroglobus medusae n. gen. n. sp. is described from the Middle Ordovician Kanosh Shale of west-central Utah. This species has a pattern of ambulacral branching with side ambulacra arising alternately from a main ambulacral trunk, previously undocumented in edrioasteroids. This pattern is interpreted as a strategy for allometrically increasing the feeding surface during ontogeny. Bizarroglobus further differs from other isorophid edrioasteroids in the plating of the peripheral rim, and the presence of pores in the interambulacral plates primarily along the edges of the ambulacra. [ABSTRACT FROM PUBLISHER]