Internal conulariid structures unveiled using mu CT

An extensive sample of well-preserved conulariids from the Pennsylvanian of the North American Midcontinent (Texas and Oklahoma, USA) have been studied using X-ray micro-Computed Tomography (mu CT) and have shown structures identified as longitudinal muscle bundles and a potential gastric cavity. These unequivocal structures appear in several specimens coming from different sites. Their preservation varies from a gastric cavity with muscle bundles in some individuals to only longitudinal muscle bundles in others. The muscle bundles fuse apically or medially, normally forming V-shaped pairs, and they extend along the theca/exoskeleton, parallel to the corner, towards the aperture. Longitudinal bundles have predominant perradial positions. Although there have been some articles on conulariid soft parts, most of them refer to relic soft parts. This is the first time that these structures are shown using mu CT. Discovery of conulariid soft parts contributes to knowledge of metazoan evolutionary history.

Automated summary

Well-preserved conulariids from Texas and Oklahoma in the USA were studied using mu CT, revealing longitudinal muscle bundles and a potential gastric cavity. These structures are evident in various specimens and their preservation varies. The longitudinal bundles form V-shaped pairs, fuse apically or medially, and run parallel to the apex along the theca/exoskeleton. This discovery contributes to understanding the evolutionary history of metazoans.