New Middle and Late Ordovician cornute stylophorans (Echinodermata) from Morocco and other peri-Gondwanan areas

Abstract

Cornute stylophorans are a minor, though typical component of Middle-Late Ordovician echinoderm assemblages adapted to soft siliciclastic substrates, in high latitude peri-Gondwanan regions. All previously reported occurrences of Darriwilian-Katian cornutes from Czech Republic, France, Morocco and Spain are revised and their plate homologies reassessed. The genera Beryllia and Juliaecarpus are reinterpreted as junior synonyms of Domfrontia, and Thoralicystis is synonymised with Bohemiaecystis. Several Mediterranean scotiaecystids previously assigned to Bohemiaecystis and/or Scotiaecystis are placed within Thoralicarpus gen. nov., and cornute taxa originally left in open nomenclature by Chauvel are formally described as Bohemiaecystis chouberti sp. nov. (AVI) and Destombesicarpus izegguirenensis gen. et sp. nov. (AVIII). Other new Mediterranean taxa include Arauricystis clariondi sp. nov., Destombesicarpus budili gen. et sp. nov., Milonicystis reboulorum sp. nov., Thoralicarpus bounemrouensis gen. et sp. nov., and T. prokopi gen. et sp. nov. The six cornute genera identified in Darriwilian-Katian Moroccan echinoderm Lagerstätten are also present in coeval assemblages of at least one other Mediterranean region, thus supporting the existence of strong faunal affinities between the Anti-Atlas, the Armorican Massif, the Barrandian area and the Iberian Peninsula.

Solutan echinoderms from the Fezouata Shale Lagerstätte (Lower Ordovician, Morocco): diversity, exceptional preservation, and palaeoecological implications

“…The occurrence of morphologically distinct, successive ontogenetic stages has already been seen in some solutans (see, e.g., Noailles et al, 2014). Comparable allometries have been also documented in other Palaeozoic echinoderms, such as eocrinoids (Parsley, 2012;Nohejlováand Fatka, 2016) and stylophorans (Lefebvre et al, 2022). In this interpretation, the unusual morphology of the Z-F24 solutans simply results from their larger size, and all specimens can be assigned to P. mobilis.…”

“…The presence of P. mobilis in the Hope Shale is more unexpected because, in the Middle Ordovician, Shropshire was part of Avalonia, which was then an independent micro-continent separated from Gondwana by the opening of the Rheic Ocean. However, several other examples of echinoderm taxa with Gondwanan affinities have been reported in the Middle Ordovician of Avalonia (see, e.g., Jefferies, 1987;Fone, 2003;Lefebvre et al, 2012;Botting et al, 2013;Lefebvre et al, 2022). These shared taxa suggest that they originated from the same pool of organisms before Avalonia rifted away from Gondwana and/or that exchanges were still possible on both sides of the Rheic Ocean in the Middle Ordovician.…”

The Late Ordovician Tafilalt Biota, Anti-Atlas, Morocco: a high-latitude perspective on the GOBE

“…At Bou Nemrou (Jbel Tijarfaïouine, western Tafilalt), the lower Sandbian Izegguirene Formation yielded the most diverse stylophoran assemblage comprising the three cornutes Arauricystis clariondi, Milonicystis reboulorum, Thoralicarpus bounemrouensis and the four mitrates Anatifopsis sp., Aspidocarpus discoidalis, Diamphidiocystis regnaulti and Eumitrocystella savilli (Lefebvre et al 2008(Lefebvre et al , 2022a. In the overlying Lower Ktaoua and Upper Tiouririne formations (Sandbian-middle Katian), cornutes were reported so far only in the eastern Tafilalt, where the amygdalothecid Domfrontia milnerorum occurs massively in a low diversity assemblage (Lefebvre et al 2022b). In most localities of the western Tafilalt (e.g.…”

An introduction to the Great Ordovician Biodiversification Event: insights from the Tafilalt Biota, Morocco

“…Despite the name 'starfish beds', asterozoans (ophiuroids and asteroids) represent a relatively minor component of the fauna, with other echinoderms such as mitrate stylophorans (Lefebvre et al 2022a) and solutans (Nohejlová & Lefebvre 2021) being far more significant. The contribution from Lefebvre et al (2022b) presents a new and diverse fauna of Middle to Late Ordovician cornute stylophorans from the Tafilalt. Other exceptionally preserved echinoderms have been described along with their mode of preservation and their palaeobiogeographical distribution, including crinoids (Botting 2018), edrioasteroids , Hexedriocystis (Zamora & Sumrall 2019), rhombiferans ) and the coronate Mespilocystites sp.…”

“…The style of preservation of these echinoderms, combined with observed sedimentary structures, indicates a mixture of autochthonous and paraautochthonous assemblages. At Bou Nemrou, the preservation of soft tissues in trilobites (Gutiérrez-Marco et al 2019;Budil & Fatka 2020) and the exceptional preservation of articulated echinoderms (Lefebvre et al 2022b) suggest these are autochthonous assemblages, while the other echinoderm Lagerstätten are a result of limited transport and show evidence of current-aligned fossil echinoderms. Nevertheless, these assemblages provide a record of localized and exceptionally preserved echinoderm meadows at a critical juncture in the history of life.…”