Palaeogeographic Implications of a New Iocrinid Crinoid (Disparida) From the Ordovician (Darriwillian) of Morocco

PeerJ. 2015 Dec 7;3:e1450. doi: 10.7717/peerj.1450. eCollection 2015.

Abstract

Complete, articulated crinoids from the Ordovician peri-Gondwanan margin are rare. Here, we describe a new species, Iocrinus africanus sp. nov., from the Darriwilian-age Taddrist Formation of Morocco. The anatomy of this species was studied using a combination of traditional palaeontological methods and non-destructive X-ray micro-tomography (micro-CT). This revealed critical features of the column, distal arms, and aboral cup, which were hidden in the surrounding rock and would have been inaccessible without the application of micro-CT. Iocrinus africanus sp. nov. is characterized by the presence of seven to thirteen tertibrachials, three in-line bifurcations per ray, and an anal sac that is predominantly unplated or very lightly plated. Iocrinus is a common genus in North America (Laurentia) and has also been reported from the United Kingdom (Avalonia) and Oman (middle east Gondwana). Together with Merocrinus, it represents one of the few geographically widespread crinoids during the Ordovician and serves to demonstrate that faunal exchanges between Laurentia and Gondwana occurred at this time. This study highlights the advantages of using both conventional and cutting-edge techniques (such as micro-CT) to describe the morphology of new fossil specimens.

Keywords: Crinoidea; Micro-CT; Morocco; Ordovician; Paleogeography; Paleozoic.

Grant support

Samuel Zamora is funded by a Ramón y Cajal Grant (RYC-2012-10576) and projects CGL2012-39471 and CGL2013-48877 from the Spanish Ministry of Economy and Competitiveness. Imran Rahman is funded by an 1851 Royal Commission Research Fellowship. William I. Ausich is supported by the National Science Foundation project, Assembling the Echinoderm Tree of Life (DEB 1036416). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.