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

Fernández, Diana Elizabeth; Giachetti, Luciana María; Stöhr, Sabine; Thuy, Ben; Pérez, Damián Eduardo; Comerio, Marcos; Pazos, Pablo J.

doi:10.5027/andgeov46n2-3157

Cited by 7 publications

(2 citation statements)

References 40 publications

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“…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.…”

Section: A C C E P T E D Mmentioning

confidence: 82%

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

Thuy

Numberger-Thuy

2021

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Ophiuroids, the slender-armed cousins of starfish, which constitute an important component of modern marine benthos and have been used successfully in exploration of (palaeo)-ecological and evolutionary trends, yet their fossil record is still poorly known. One of the major gaps in the known palaeobiodiversity of this group coincides with a global palaeoenvironmental crisis during the early Toarcian (Early Jurassic, 183 myr ago), known as the Jenkyns Event. Here, we describe ophiuroid remains retrieved from a series of samples from the Dudelange (Luxembourg) drill core, which spans the lower part of the Toarcian, between the top of the Pliensbachian to the onset of the Jenkyns Event. A total of 21 species are recorded, including three new genera and 12 new species. Ophiuroid diversity and abundance fluctuate in parallel with depositional facies, with lowest values coinciding with black shales. Highest diversities, including exceptional occurrences of taxa nowadays restricted to deep-sea areas, are recorded from just below the black shales corresponding to the onset of the Jenkyns Event. Our results show that even small (100 g) bulk sediment samples retrieved from drill cores can yield numerous identifiable ophiuroid remains, thus unlocking this group for the study of faunal change across palaeoenvironmental crises.

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Section: A C C E P T E D Mmentioning

confidence: 82%

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

Thuy

Numberger-Thuy

2021

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“…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).…”

Section: Introductionmentioning

confidence: 99%

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

MORTON

Myers

Gingras

et al. 2023

Palaios

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An array of trace fossils have been ascribed to brittle-star behaviors including locomotion traces such as Biformites. Brittle-star locomotion has been well described but little work has been done to link modern brittle-star behavior to the trace fossil record. To draw this connection, a brittle star was kept in an aquarium and isolated in a “walking” tank with a fine glass-bead substrate. The animal was left in the walking tank for 30 minutes then the substrate was examined for traces. A digital camera was used to record the animal's movements and to document the resulting traces. Photographs were processed with photogrammetry software to produce digital models in order to acquire high-resolution images. Walking traces were described in detail and two morphologies were identified, which correspond with the ‘rowing' and ‘reverse-rowing' modes of brittle-star locomotion. Interestingly, traces similar to Biformites were not formed although some Biformites characters are observed. Morphological similarities include elongated lobate depressions and bioglyphs. Trackway dissimilarities include a repeating, paired, symmetrical pattern observed in the lab contrasting with Biformites that is often expressed as a texture of dense and overlapping, or isolated imprints. Another dissimilarity is the expression of bioglyphs in the lab as striae compared to the positive protuberances observed in Biformites. This study illustrates the utility of using actualistic observations to: (1) refine interpretations of locomotory mechanisms, such as rowing and reverse rowing, for a better understanding of walking behavior, and (2) to expand recognition criteria for ophiuroid (and other taxa) tracks in the fossil record.

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A micromorphological analysis ofBolonia lataMeunier from the Cretaceous of the Neuquén Basin (Patagonia, Argentina): new insights into the tracemaker

Giachetti,

Fernández,

Comerio

et al. 2023

Papers in Palaeontology

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Polychaetes, echinoids and gastropods have been proposed as tracemakers for Bolonia Meunier, an elongate positive epirelief trace fossil characterized by two lobes composed of biserial, subtriangular pads and a mostly heart‐shaped cross‐section. Here, the internal structure and micromorphology of Bolonia are described for the first time using serial thin sections from shallow‐marine Lower Cretaceous intervals of the Agrio Formation (Neuquén Basin, Argentina). In vertical thin sections, a conical structure of variable width extends centrally from the base to the top of the trace. In horizontal thin sections, grains are reoriented and reworked, forming a central zigzag structure. The organic matter and clays form grain aggregates representing the internal structure of individual pads of the trace fossil. The sediment has mostly been reoriented, with grains making up subcircular pods. We interpret the central conical structure as the collapse of the medial zone of the trace fossil, which could have destroyed drain tubes, especially in the absence of early cementation. Studying horizontal thin sections, we reconstruct the diagnostic biserial pads as biserial concave structures. These are interpreted as backfilling structures produced by the aboral and lateral spines of irregular echinoids, which worked together to compact the sediment anteroposteriorly and moved alternatively, explaining the zigzag pattern in the menisci. We propose Spatangoidea or Cassiduloidea (or a closely related group) with a similar burrowing ability and spine movement as tracemakers of these Bolonia specimens.

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

Cited by 7 publications

References 40 publications

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

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

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

A micromorphological analysis ofBolonia lataMeunier from the Cretaceous of the Neuquén Basin (Patagonia, Argentina): new insights into the tracemaker

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