Thereitis carlsbergi, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 114-115

publication ID	https://doi.org/ 10.11646/zootaxa.4654.1.1
publication LSID	lsid:zoobank.org:pub:CFD82CC0-3110-472E-972B-7ADC0C523A04
DOI	https://doi.org/10.5281/zenodo.5582866
persistent identifier	https://treatment.plazi.org/id/EC746AE5-521D-4DF2-BD29-33CD2FC0C5F0
taxon LSID	lsid:zoobank.org:act:EC746AE5-521D-4DF2-BD29-33CD2FC0C5F0
treatment provided by	Plazi
scientific name	Thereitis carlsbergi
status	sp. nov.

Treatment

Thereitis carlsbergi n. sp.

Figs 27 View FIGURE 27 Y–AE, 28A

Diagnosis. Protoconch of five whorls with densely spaced oblique axial ribs and spiral ribs on the last half whorl. Teleoconch with flat whorls carrying four spiral ribs, the third generally much stronger than the others while the fourth is covered by succeeding whorl.

Derivation of name. In honour of the Carlsberg Foundation, which financed this project.

Type material. The holotype MGUH 33203 is an external mould collected by A. Rosenkrantz, 20 Sep. 1927. Paratype MGUH 33204 View Materials comes from Rødvig, while paratype MGUH 33205 View Materials is from Skeldervig. Both are from the same stratigraphic level as the holotype.

Additional material. ØSM.10042-111, 201 internal and external moulds collected in connection with this study (sample number: SH.107.A–B, SH.142, SH.174, SH.183.B, SH.206, SH.231, SH.251, SH.254, SH.274.A–C, SH.274.C (3 specimens), SH.281.A, SH.287.B, SH.287.C (2 specimens), SH.288, SH.289, SH.290, SH.291.A, SH.291.B, SH.292, SH.295.A, SH.310, SH.318.A–B, SH.320, SH.325.A, SH.328.A–B, SH.329, SH.330, SH.331, SH.332, SH.333.A–B, SH.334.A–B, SH.349, SH.350, SH.352.B, SH.353, SH.359, SH.377, SH.382 (4 specimens), SH.385.B (2 specimens), SH.385.B–C, SH.385.C (2 specimens), SH.386.C, SH.388 (2 specimens), SH.394, SH.396, SH.404, SH.405, SH.410.A–B, SH.410.B, SH.414.C, SH.415.A, SH.419.B, SH.424, SH.425, SH.437.A, SH.445, SH.465 (2 specimens), SH.466, SH.467, SH.468.A, SH.473, SH.485.C, SR.143, SR.144, SR.146, SR.147.A–B, SR.148, SR.150, SR.151, SR.152.A–B (2 specimens), SR.152.A, SR.264, SR.275 (2 specimens), SR.276.A–B (4 specimens), SR.277.C (2 specimens), SR.279, SR.280, SR.281, SR.283, SR.284, SR.287 (2 specimens), SR.288 (2 specimens), SR.290, SR.294 (2 specimens), SR.295 (4 specimens), SR.296.A–B (3 specimens), SR.297 (2 specimens), SR.298.A (3 specimens), SR.298.B, SR.301 (2 specimens), SR.302, SR.303.A–B (2 specimens), SR.305. A–B, SR.307.A, SR.308.A–B, SR.309.A, SR.310.B (2 specimens), SR.310.B–C (2 specimens), SR.311.A (2 specimens), SR.311.A–B, SR.320, SR.340, SR.359, SR.360.A–B, SR.361, SR.369, SR.372, SR.374, SR.381, SR.394, SR.398, SR.399, SR.400, SR.401, SR.402, SR.403.B, SR.404.A–B, SR.406, SR.432, SR.439, SR.449, SR.451, SR.464, SR.473, SR.480, SR.490, SR.494, SR.495, SR.496, SR.501, SR.507, SR.508, SR.509.A–B, SR.513, SR.517, SR.519.A, SR.521, SR.522, SR.523, SR.524, SR.529, SR.548, SR.552, SR.562, SR.567, SR.569, SR.577, SR.578.B–C, SR.587.A–B, SR.588.B, SR.591, SR.614, SR.619, SR.623, SR.624, SR.641, SR.652, SR.653, SR.654, SR.655 (2 specimens), SR.656 (2 specimens), SR.685 (2 specimens), SR.698.A, SO.185, DN.19 and DN.26.B), and an unspecified number found in the collections of the Natural History Museum of Denmark .

Type stratum and type locality. Cerithium Limestone Member of the Rødvig Formation just north of Kirkevig, Stevns Klint .

Occurrence. This species occurs from the lower half to the top of the lower Danian Cerithium Limestone at Stevns Klint. It is also known from the ‘dead layer’ in Dania and Vokslev quarries, Northern Jutland.

Description. The shell is high turriculate, more than five times higher than wide. The last whorl equals close to a quarter of the total shell height and the aperture approximately 1/8 the total height.

Protoconch multispiral, high conical with five moderately convex whorls separated by fairly deep sutures. First 1 ½ whorls smooth, the following covered by up to around 22 oblique collabral threads. Two weak upper and a strong abapical spiral rib appear less than half a whorl from teleoconch. Transition to teleoconch fairly gradual, being suggested by the disappearance of collabral threads.

Teleoconch consisting of up to 11 flat whorls with two narrow adapical spiral ribs of equal strength and a normally much stronger abapical rib situated on a weak carina somewhat above a narrow suture. On a few specimens the spiral ribs are of equal strength or the adapical one becomes slightly stronger than the other two. Distance between the crest of all three ribs equal; interspaces between ribs becoming wider than ribs on later whorls. A fourth spiral rib occurs just below abapical suture, rib typically more or less completely covered by succeeding whorl. Base of whorl flat. Aperture rounded rectangular with a short, smooth and straight columella with the short canal turned left.

Measurements. The largest complete specimen measures 7.4 mm in height and 1.4 mm in diameter. Protoconch approximating 0.4 mm in width and 0.8 mm in height.

Remarks. Thereitis carlsbergi n. sp. differs from the Selandian Thereitis monbergi ( Ravn, 1939) from Denmark by the presence of spiral ribs on the last protoconch whorl, the absence of axial riblets on the teleoconch, the wider interspace between the spiral ribs and by the relatively higher spire. It is distinguished from the Selandian Thereitis weinbrechti Schnetler, 2001 from Denmark by the absence of spiral ribs before the last protoconch whorl and by the stronger third spiral rib on the teleoconch. It is furthermore distinguished from the middle Danian Thereitis tricingulata ( Ravn, 1933) from Faxe, Denmark, by having only five protoconch whorls and possibly also by a slightly different spiral sculpture, although the latter may be due to the limited material available (two specimens) of T. tricingula .

References

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.