Myelodactylida Ausich, 1998 Family

Ausich, William I., Wilson, Mark A. & Vinn, Olev, 2012, Crinoids from the Silurian of Western Estonia, Acta Palaeontologica Polonica 57 (3), pp. 613-631 : 628

Order Myelodactylida Ausich, 1998 Family Myelodactylidae Miller, 1883 Myelodactylus ? sp.

Fig. 5A .

Material.—The columnal on which this identification is based is TUG 1395−7from the Ohesaare Formation at Ohesaare Cliff, Saaremaa, Estonia.

Discussion.—One apparently elliptical columnal from Ohesaare Formation was exposed with the articular facet parallel to bedding. The only common Silurian crinoids to have elliptical columnals are the myelodactylids. This columnal ( Fig. 5A ) has radially disposed crenulae on half of the columnal facet, and the other half of the columnal facet is damaged. This facet is not similar to Gotland myelodactylids illustrated by Donovan and Franzén−Bengtson (1988); thus this identification is considered tentative. Myelodactylids have very small and inconspicuous crowns. They are normally identified from pluricolumnal segments that have some degree of planispiral coiling and bilaterally symmetrical columnals.

Figures

Fig. 5. Camerate, disparid, and flexible crinoids from the Silurian of Estonia. A. Myelodactylus? sp., TUG 1395−7, Ohesaare Formation (Pridoli), Ohesaare Cliff. Articular facet of columnal. B. Saaremaacrinus estoniensis gen. et sp. nov., holotype, TUG 1395−3, middle Äigu Beds, Kaugatuma Formation (Pridoli), Kaugatuma Cliff. B1, lateral view of theca, interpretation of plates in Fig. 4; B2, tegmen view of theca. C, D. Cicerocrinus osiliensis (Jaekel, 1900), Ohesaare Formation (Pridoli), Ohesaare Cliff. C. TUG 1376−1. C−ray lateral view of calyx. D. GIT 405−242. C−ray lateral view of calyx. E. Protaxocrinus salteri? (Angelin, 1878), TUG 1395−4, Ninase Member, Jaani Formation (Wenlock), Suuriku Cliff. E1, CD interray view of crown and proximal column; E2, CD interray view of calyx, proximal arms and column, note badly beach−worn preservation. F. Caleocrinus balticensis sp. nov., GIT 405−12, Juuru Stage (Llandovery), Heltermaa. D−Ray lateral view of crown. G, H. Desmidocrinus laevigatus sp. nov., middle Äigu Beds, Kaugatuma Formation (Pridoli), Kaugatuma Cliff. G. TUG 1395−1, holotype. G1, oblique D−ray lateral view of calyx; G2, CD−interray lateral view of calyx; G3, D−ray lateral view of incomplete crown. H. TUG 1395−2, paratype. D−ray lateral view of calyx.