Fossil crinoids from the Valley of Rocks, Lynton, north Devon (Devonian)

• Published in: Proceedings of the Geologists' Association 2015-10, Vol.126 (4-5), p.582-588
• Main Authors: Fearnhead, Fiona E., Donovan, Stephen K.
• Format: Article
• Language: English
• Subjects: Columnals; Cupressocrinites; Eifelian; Emsian; Hexacrinites; Lynton Formation
• ISSN: 0016-7878
• DOI: 10.1016/j.pgeola.2015.08.006

Disarticulated crinoid ossicles, particularly columnals, from the Devonian of south-west England are locally common, but incompletely known; most studies have been in the 21st Century. A new collection of mouldic crinoid ossicles from the Lynton Formation (Lower/Middle Devonian) of the Valley of Rocks, west of Lynton, is rich in columnals of the monobathrid camerate Hexacrinites sp. D, represented by many hundreds of specimens. This is the first record of proximal columnals of Hexacrinites from the type area of the Devonian. A columnal of the cladid Cupressocrinites sp. is a rare example of a widely distributed Devonian genus; this is the oldest specimen known from the British Isles. Broad columnals of Annulocolumnus (col.) sp. A. annulus Donovan have a primitive morphology, with a wide lumen, more reminiscent of a Lower Ordovician taxon. Pentagonocyclicus (col.) sp. is a robust example of a widely distributed Palaeozoic morphotaxon. Elliptical brachials with synarthrial articulations (cladids?) are reminiscent of columnals of platycrinitid camerate crinoids. A radice ossicle with a figure-of-eight lumen is reminiscent of roots from the Silurian of Sweden. Taken together, these identifications indicate that our knowledge of the Devonian crinoids of south-west England remains incomplete in an area where few new collections have been made since the 19th Century.