Intriguing crinoid remains from the Rhaetian of Iran and their possible implications for the mid-Carnian crinoid extinction event

It has been generally accepted that the representatives of holocrinid crinoids (Holocrinidae sensu Rasmussen, or Holocrinida sensu Hess and Messing) became extinct during the mid-Carnian extinction event. Until now, the youngest known, though not yet described, holocrinid representatives were specimens of Holocrinus nov. sp. from the early Tuvalian (Carnian). Here, we report dissociated but relatively well-preserved crinoid remains from the Rhaetian of central Iran resembling two taxa: Holocrinus sp. and Isocrinus sp. (both sensu lato). The holocrinid ossicles are represented mainly by internodals, but two nodals have been also reported. One of them (pluricolumnal consisting of nodal and infranodal) possesses undifferentiated symplectical lower facets which makes possible a reliable assignment to the genus level. The presented material constitutes the youngest known holocrinid crinoids to date.