Stalked crinoids from Gan (Late Ypresian, southwestern France): exceptional stereom preservation, paleoecology and taxon
- PDF / 5,737,656 Bytes
- 20 Pages / 595.276 x 790.866 pts Page_size
- 100 Downloads / 153 Views
(0123456789().,-volV)(0123456789().,-volV)
REGULAR RESEARCH ARTICLE
Stalked crinoids from Gan (Late Ypresian, southwestern France): exceptional stereom preservation, paleoecology and taxonomic affinities Didier Merle1 • Michel Roux2 Received: 18 May 2018 / Accepted: 29 August 2018 Akademie der Naturwissenschaften Schweiz (SCNAT) 2018
Abstract Exceptionally well-preserved ossicles of xenomorphic stalked crinoids (Echinodermata) were found into the Late Ypresian clay of the Tuilerie de Gan (Pyre´ne´es-Atlantiques, southwestern France). Three kinds of columnal articulation correspond to three different genera, including the new genus Eocenocrinus. These columnals are attributed to Paraconocrinus romanensis, Democrinus londinensis and Eocenocrinus hessi n. gen., n. sp. Associated benthic fauna as well as columnal characters related to water depth confirm an increasing depth to an epibathyal environment as previously suggested by mollusk and foraminifer associations. Paraconocrinus romanensis associated with Democrinus londinensis mark the maximum water depth, which did not exceed 300 m. Distal columnal series with proximal roots of P. romanensis and D. londinensis were collected with their ossicles connected, indicating that these species lived on a muddy bottom. E. hessi n. gen., n. sp. is suspected to have been attached on hard substrate. Without diagenetic crystallizing, the crinoid stereom and its micro-biocorrosion appear as in extant specimens. We attribute to Eocenocrinus n. gen. large columnals previously described from northeastern Italy and recognize two species: E. bayani n. gen., n. sp. (Middle Lutetian) and E. didymus (Priabonian). E. hessi n. gen., n. sp. may represent the oldest known species in the family Phrynocrinidae. Keywords Crinoidea Echinodermata Eocene Paleoenvironment New taxa
Introduction Aboral cups and columnals of stalked crinoids from the Marnes de Gan Formation at Bosdarros near Gan (Pyre´ne´es-Atlantiques, southwestern France) (Fig. 1) were first described briefly and figured by d’Archiac (1850) and Rouault (1850) and attributed to Bourgueticrinus thorenti
Editorial Handling: Ben Thuy. & Didier Merle [email protected] Michel Roux [email protected] 1
De´partement Origines et Evolution, Muse´um national d’Histoire naturelle, Sorbonne Universite´ (CR2P, UMR 7207, MNHN, CNRS, UPMC), 8, rue Buffon, 75005 Paris, France
2
De´partement Origines et Evolution, Muse´um national d’Histoire naturelle, Sorbonne Universite´ (ISYEB UMR7205, MNHN-CNRS-UPMC-EPHE), 55 rue Buffon, 75005 Paris, France
d’Archiac, 1846. Roux and Plaziat (1978) listed stalked crinoids from the Pyrenean Paleogene but only referred to the occurrence of Thanetian columnals collected in the vicinity of Gan. Merle (1985, 1986) identified several beds containing crinoid ossicles in the section known as Tuilerie de Gan. Most of the specimens were isolated columnals, except for two distal stalk segments with proximal articulated roots. These columnals belong to xenomorphic stalks in which proxistele, mesistele and d
Data Loading...
