Data from: The nervous and circulatory systems of a Cretaceous crinoid: preservation, paleobiology, and evolutionary significance

Featherstars, those comatulid crinoids that shed their stalk during their
ontogeny, are the most species-rich lineage of modern crinoids and the
only ones present in shallow water today. Although they are of
considerable paleontological interest as a ‘success story’ of the Mesozoic
Marine Revolution, their fossil record is relatively species-poor and
fragmentary. New Spanish fossils of the Cretaceous featherstar Decameros
ricordeanus preserve the shape and configuration of nervous and
circulatory anatomy in the form of infilled cavities, which we reconstruct
from CT scans. The circulatory system of D. ricordeanus was relatively
extensive and complex, implying a pattern of coelomic fluid flow that is
unique among crinoids, and the peripheral parts of the nervous system
include linkages both to the circulatory system and to the surface of the
body. A phylogenetic analyses – the first to include both living and
fossil featherstars and which includes characters from internal anatomy –
recovers D. ricordeanus among the lineage of featherstars that includes
Himerometroidea, Tropiometra, and “Antedonoidea,” among others. D
ricordeanus is larger than almost any modern featherstar, and its
elaborate coelomic morphology appears to be a consequence of positive
allometry. All featherstars with coelomic diverticula are shown to belong
to a single comatulid subclade, and this feature may constitute a
synapomorphy of that group. Some preservation of cavities corresponding to
soft tissue is probably not exceptional in fossil crinoids, providing an
opportunity to study the diversity and evolution of extinct anatomical
systems typically only preserved in Lagerstätten.