Stalked crinoids from Gan (Late Ypresian, southwestern France): exceptional stereom preservation, paleoecology and taxonomic affinities

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449

Detailed studies of the middle Ilerdian (lower Ypresian) blue marls of the Gulf of Languedoc (Corbières, Aude, France), belonging to the north Pyrenean foreland basin, have revealed a more abundant and diverse crinoid fauna than previously documented from the Lower Eocene. Here we describe five species of stalked crinoids in the family Rhizocrinidae (Cherbonniericrinus requiensis n. sp., ?Democrinus elongatus, Globulocrinus amphoraformis n. gen., n. sp., Pseudoconocrinus doncieuxi and P. lavadensis n. sp.), one barnacle-like species in the stalkless family Holopodidae (Holopus plaziati n. sp.) and a single feather star in the family Conometridae (Amphorometra atacica). Several sites have yielded brachials and rhizoids in addition to abundant aboral cups and columnals indicating in situ fossilisation of the dissociated skeletal elements. P. lavadensis n. sp. and ?D. elongatus have been collected only from outcrops located in the upper part of the middle blue marls, while P. doncieuxi predominates, with a wide range of morphological variation, in the lower blue marls. The fossil assemblage at the locality of Réqui near Montlaur differs from the others in the smaller size of most individuals and the presence of H. plaziati n. sp., C. requiensis n. sp., G. amphoraformis n. gen., n. sp., and P. doncieuxi suboblongus n. subsp. This particular association with high juvenile mortality corresponds to an unstable environment with mixed substrates (muddy and rocky). The crinoid fauna of the Corbières appears to be the most diverse of Early Eocene age known to date. With the fauna of the London Clay, a boreal formation of the same age, it shares the presence of the genera Democrinus and Amphorometra in an open-sea environment. A comparison with extant faunas allows the depth of deposition at the Ypresian sites in the Gulf of Languedoc to be estimated between from 100 and 140 meters.

Section: Palaeobathymetry and Palaeogeographymentioning

confidence: 89%

Section: Taphonomy and Palaeoecologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A diverse crinoid fauna (Echinodermata, Crinoidea) from the Lower Eocene of the Gulf of Languedoc (Corbières, Aude, southern France)

Roux

Martinez²,

Vizcaı̈no³

2021

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449

“…The lightness of these ossicles allows them to be transported without conspicuous attrition. During a prolonged stay on the sea bottom or in the superficial part of the sediment, biocorrosion weakens the external layer of the ossicles, which partially disappears at the slightest displacement or reworking, blunting the joints and angles (Améziane-Cominardi and Roux 1987;Merle and Roux 2018). Around Entrechaux and at Vedene, there is a mixture of well-preserved and worn ossicles.…”

Section: Taphonomy Paleoecology and Paleobathymetrymentioning

confidence: 99%

“…Paraconocrinus rhodanicus n. sp. is a small species with distal Co articulated by narrow synarthries of fulcral ridge bordered by slightly depressed areas as in most species of the genus Paraconocrinus (Merle and Roux 2018;Roux et al 2019). The Co figured from the Middle Miocene near Turin (see especially Albus 1931 andManni 2005) differ in having a larger size and more massive shape.…”

Section: Ordermentioning

confidence: 99%

Early Miocene stalked crinoids (Echinodermata) from the southern Rhodanian basin (southeastern France). Paleoenvironments and taxonomy

Roux

Philippe²

2021

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420

Using recent samplings and specimens from ancient collections, 14 sites and five species of stalked crinoids have been listed in the Miocene of the southern Rhodanian basin (southeastern France). Three species and two genera are new for science: Papacrinus avignonensis n. gen., n sp. (Balanocrininae), Paraconocrinus rhodanicus n. sp. (Rhizocrinidae) and Gastecrinus vinealis n. gen., n. sp. (Incertae sedis). The identification among the Mediterranean Miocene fauna of the genus Metacrinus, now confined to the Indo-Pacific province, was confirmed by the discovery of brachial ossicles attributed to Metacrinus berthei. The richest and most diversified site was exposed during temporal excavations at the Place du Palais des Papes in Avignon. Four out of the five stalked crinoid species were found in this fossil assemblage in which M. berthei predominates. ?Endoxocrinus gastaldii is associated with M. berthei in several sites. Using dissociated ossicles, differences in quantitative and qualitative characters between these two species are deeply analyzed with their taphonomical, taxonomical and paleoecological consequences. Paleoreliefs and valleys, which had been incised during the Burdigalian, channeled currents. They favored stalked crinoid settlement on various substrates during the late Burdigalian—Lower Langhian transgression. Comparison with the extant fauna allows us to estimate the depth range of the biotopes with stalked crinoids from 100 to 250 m. These estimates are in agreement with those deduced from other paleontological studies.

New Eocene species of the crinoid genera Holopus and Cyathidium (Cyrtocrinida: Holopodidae) from north-eastern Italy

MARTINEZ-SOARES,

ROUX,

GIUSBERTI

et al. 2024

Holopodidae is one of the three families in the order Cyrtocrinida that have extant representatives. Two genera have been described, Holopus and Cyathidium, both with extant species and fossil representatives dating back to the Cenomanian (Late Cretaceous). Eocene (Lutetian) holopodid material from the Chiampo Valley (north-eastern Italy) has recently been attributed to H. spileccense, the type-stratum and locality of which is the Ypresian of the nearby Spilecco Hill, and to C. gastaldii known from the Miocene of Turin. Here we describe new holopodid material from both Chiampo and Spilecco, comprising cups and numerous brachials. Using qualitative and quantitative characters, the Chiampo holopodids are deemed to be assignable to two new species: Holopus fabianii sp. nov. and Cyathidium chiampoensis sp. nov. The Chiampo material includes the first records of keystone plates and distal brachials for an extinct species of Holopus. New proximal brachials are described for H. spileccense but no keystone plate was found for this species. Access to the holotype of Cyathidium gastaldii has enabled a description of the specimen and a first diagnosis for the species. Formerly described cups, as well as a newly collected one, are attributed to Cyathidium sp. due to the lack of diagnostic characters. The affinities between H. spileccense, H. fabianii sp. nov. and the extant Indo-Pacific H. alidis suggest that these three species might share a common Gondwanan origin.