Ontogenetic data for Erisocrinus typus

<p><span>Crinoids were major constituents of Late Carboniferous (Pennsylvanian) marine ecosystems, but their rapid disarticulation rates after death resulted in few well-preserved specimens, limiting the study of their growth. This is amplified for cladids, who had among the highest disarticulation rates of all Paleozoic crinoids, due to the relatively loose suturing of the calyx plates. However, <em>Erisocrinus typus</em> Meek and Worthen, 1865, has been found in unusually large numbers, most preserved as cups, but some as nearly complete crowns, in the Barnsdall Formation in Oklahoma. The Barnsdall Formation, a Koncentrat Lagerstätte, is predominantly composed of fine- to medium-grained sandstone, overlain by mudstone and shale; severe compaction of the fossils in the mudstone and shale layer in this formation allowed for exceptional preservation of the plates. Herein, we summarize a growth study based on ten crowns of <em>E. typus</em>, showcasing a well-defined growth series of this species from the Barnsdall Formation, including fossils from juvenile stages of development, which are typically rarely preserved. We used high-resolution photographs imported into ImageJ and recorded measurements of the cup and arms for all non-distorted or disarticulated plates. Results show that the plates of the cup grew anisometrically with both positive and negative allometry. The primibrachial plates of <em>E. typus</em> grew with positive allometry. The brachial plates started as uniserial (i.e. cuneiform) as juveniles but shifted to be biserial. <em>Erisocrinus typus</em> broadly shares similar growth trajectories to other cladids. These growth patterns provide insight into feeding strategies and can aid in understanding crinoid evolutionary paleoecological trends.</span></p>