Ageria, Abbass, 1973

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 126

Ageria sp.

Figs 29 F–G

Material. A moderately well preserved external and internal mould ( MGUH 33229), which may be mislaid, and a poorly preserved external mould MGUH 33230.

Occurrence. Lithified top of the Højerup Member of the Maastrichtian Tor Formation at Rødvig and Holtug Quarry, Stevns Klint.

Description. Protoconch not known. Teleoconch whorls flattened, relatively high, the height corresponding to about 60 % of width, separated by shallow suture. Keel on last whorl very sharp, delineated adapically by wide furrow. Base strongly flattened. Aperture subrectangular, slightly flaring with two low spiral folds on outer lip.

Teleoconch sculpture changing with growth; initial whorls carrying about 14 coarse, slightly opisthocline transverse ribs fading out towards sutures; ribs terminating abapically towards weak spiral rib delineating beaded keel. Transverse ribs fading out on later whorls, being replaced by three beaded spiral ribs; adapical keel ramp carrying three weak spiral threads. Growth lines opisthocyrt and slightly opisthocline.

Measurements. Teleoconch on disappeared specimen at least 11.2 mm high and 3.7 mm wide, consisting of nine whorls.

Remarks. Ageria sp. resembles Ageria gankinensis Kaim et al., 2004 from the Late Maastrichtian of Siberia, but differs by the denser sculpture with three instead of two primary beaded spiral ribs adapical to the keel. It seems to differ from Ageria skeldervigensis n. sp. described above from the same deposits by the relatively high whorls and extremely sharp keel, but a very limited material prevents any definite conclusions as the differences could reflect ecophenotypic variation.

Figures

FIGURE 29. A–B. Ageria skeldervigensis n. sp., Silicone cast of holotype MGUH 33226. Width 3.8, 4.5 mm respectively. C–E. Ageria laxa n. sp. C–D. Silicone cast of holotype MGUH 33227. Width 4.6 mm for teleoconch, 0.3 mm for protoconch. E. Silicone cast of paratype MGUH 33228. Width 6.7 mm. F–G. Ageria sp. F. Silicone cast of seemingly mislaid specimen MGUH 33229. Width 3.7 mm. G. Silicone cast of MGUH 33230. Width 0.6 mm. H–K. Coniscala umbilica n. sp. H. Silicone cast of paratype MGUH 33231. Width 1.4 mm. I–J. Holotype MGUH 33232. Width 19.6 mm. K. Paratype MGUH 33233. Width 12.4 mm. L–N. Opalia sp. L–M. Silicone cast of MGUH 33234. Width 1.3 mm. N. Silicone cast of MGUH 33235. Width 0.5 mm. O–Q. Claviscala minor n. sp. O–P. Silicone cast of holotype MGUH 33236. Width of teleoconch 0.9 mm. Width of protoconch 0.4 mm. Q. Silicone cast of paratype MGUH 33237. Width 1.3 mm. R. Claviscala sp., Silicone cast of MGUH 33238. Width 1.4 mm. S–V. Amaea aliceae n. sp. S–U. Silicone cast and inner mould of holotype MGUH 33239. Width 2.7, 2.0 and 3.1 mm respectively. V. Silicone cast of paratype MGUH 33240. Width 1.7 mm. W. Amaea stevniensis n. sp., Silicone cast of holotype MGUH 33241. Width 1.0 mm. X. Amaea sp. A. Silicone cast of MGUH 33242. Width of teleoconch 1.1 mm.