Thylacodes, Guettard, 1770

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 108

Thylacodes ? sp.

Figs 27 K–M

Material. Specimen MGUH 33191 is a fragmentary 2.4 mm wide external mould.

Occurrence. Thylacodes ? sp. was collected from the top of the Maastrichtian Tor Formation at Holtug Quarry, Stevns Klint.

Description. Shell low turbiniform, sinistral with flattened apex seemingly attached to a slender bryozoan branch. Protoconch heterostrophic, consisting of two whorls on which no microsculpture can be observed. Teleoconch whorls expanding slowly, flattened on adapical side, becoming more convex on lateral and abapical side. Adapical side of whorls with strong transverse ribs curving from the adapical suture and backwards into an initially indistinct, but progressively deeper sinus situated halfway between sutures; transverse ribs continue forward and down to the periphery of the last whorl, where they are replaced rather abruptly by seven moderately coarse spiral ribs. Transverse rib number per half-whorl approximating 15 on third whorl.

Remarks. Thylacodes ? sp. differs from T. contendis n. sp. described above by the sinistral coiling and a coarser transverse ribbing. This may though just reflect ecophenetic differences within the species; especially as only a single specimen is known of the present taxon.

Figures

FIGURE 27. A–B. Melanella? sp., Silicone cast of MGUH 33183. Width 1.4 mm. C–E. Vermetus sp., C. Silicone cast of attached tube MGUH 33184. Largest diameter 6.6 mm. D. Inner mould of protoconch and initial teleoconch inside bryozoan ball. MGUH 33185. Protoconch 0.5 mm wide. E. Silicone cast of MGUH 33186. Width 3.5 mm. F–J. Thylacodes contendis n. sp. F. Attached holotype mould MGUH 33187. Width 2.4 mm. G–H. Silicone cast of paratype MGUH 33188. Width 2.9 mm. I. Silicone cast of paratype MGUH 33189. Width 3.0 mm. J. Silicone cast of free whorl paratype MGUH 33190. Tube diameter 1.8 mm. K–M. Thylacodes? sp., Silicone cast of MGUH 33191. Width 2.4 mm. N. Dendropoma sp., Protoconch and initial teleoconch tube of MGUH 33192. Width 1.7 mm. O. Laxispira sp., Silicone cast of MGUH 33193. Width 3.6 mm. P–R. Epetrium s.l. skeldervigensis n. sp. P. Silicone cast of holotype MGUH 33194. Width 2.4 mm. Q. Silicone cast of paratype MGUH 33195. Width 4.0 mm. R. Silicone cast of paratype MGUH 33196. Width 3.6 mm. S. Triphoridae genus et sp. indet. Sinistrally coiled protoconch MGUH 33197. Width 0.7 mm. T–W. Cerithiopsis restemlongis n. sp. T. Silicone cast of holotype MGUH 33198. Width 1.0 mm. U. Silicone cast of paratype MGUH 33199. Width 1.5 mm. V. Silicone cast of paratype protoconch MGUH 33200. Width 0.5 mm. W. Silicone cast of paratype protoconch MGUH 33201. Width 0.6 mm and height 1.1 mm. X. Cerithiopsis? sp., Silicone cast of MGUH 33202. Width 0.6 mm. Y–AE. Thereitis carlsbergi n. sp. Y–Z. Silicone cast of holotype specimen MGUH 33203. Width of protoconch 0.6 mm and teleoconch 1.4 mm. AE. Silicone cast of paratype MGUH 33204. Width 0.7 mm.