Brittle stars from the Lower Cretaceous of Patagonia: first ophiuroid articulated remains for the Mesozoic of South America

Abstract

The first articulated remains of ophiuroids for the Mesozoic of South America are described from the Lower Cretaceous of Neuquén Basin, Argentina. The taxonomic analysis allows the assignment of the material described herein to the extinct genus Ophiopetra. The specimens belong to a new species, but considering the poor preservation, a new name is not introduced, as it would be based on an incomplete diagnosis. Certain characteristics (e.g., the diameter of the disc, the width/height ratio of the vertebrae) suggest that these ophiuroids are paedomorphic specimens. In light of the latest classification of the Ophiuroidea, and new insights on the spine articulation microstructure of Ophiopetra lithographica presented herein, a transfer of Ophiopetra to the family Ophionereididae within the order Amphilepidida is proposed. This material expands the palaeogeographic record of this genus, since it represents the first remains of Ophiopetra described in the Southern Hemisphere. It is also the first Cretaceous record of the genus worldwide.

Brittlestar diversity at the dawn of the Jenkyns Event (early Toarcian Oceanic Anoxic Event): new microfossils from the Dudelange drill core, Luxembourg

“…The lateral arm plates of Dermacantha share greatest similarities with those of the extinct ophionereidid Ophiopetra Hess in Enay & Hess, 1962 from the Upper Jurassic of Europe and the Lower Cretaceous of Argentina (Fernández et al 2019). The general plate architecture and the spine articulation morphology are similar to such an extent that we anticipate close phylogenetic ties, to be explored using phylogenetic analyses.…”

AQUARIA-BASED OBSERVATIONS OF THE OPHIUROIDOPHIOLEPIS SUPERBAAND THE TRACKWAYS IT PRODUCES

“…Ophiuroids are generally regarded as being restricted to fully marine environments but they have been observed in brackish environments as well (Mángano et al 1999). Although fossil evidence of ophiuroids is abundant, their tendency to disarticulate makes meaningful interpretation of their role in ancient systems difficult (Kerr et al 2004; Fernández et al 2019). In contrast, trace fossils attributed to ophiuroids are common and diverse (Yang and Song 1985; Wilson and Rigby 2000; Bell 2004; Schlirf 2012; Knaust and Neuman 2016; Belaústegui et al 2017; Feng et al 2019) and provide clear evidence of occupation of a particular depositional setting if the trace fossils are demonstrated to have indeed arisen from ophiuroid activity (Frey and Seilacher 1980).…”