Abstract

Starfish from the Pennsylvanian LaSalle Limestone of Illinois are the first species of Calliasterella to be found outside Russia. The type and only previously known species, C. mira, was described in 1879 from Pennsylvanian strata near Moscow. Our specimens are much better preserved, even though in death the arms curled inward to conceal the ambulacrals and most of the adambulacrals. The madrepore is known for the first time, and the shape of the aboral side of the disk is established. Our species differs from C. mira in having less acuminate corners on disk plates, scattered tubercles instead of a paxillary ridge on each aboral arm plate, and differently shaped supramarginals, axillaries, and adambulacrals. Aborally, this hemizonidan starfish bears a striking similarity to the phanerozonidan Protopalaeaster, and many plates appear homologous.

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