Thereitis carlsbergi Hansen 2019, n. sp.
Creators: name: Hansen, Thomas
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Cerithiopsidae
Thereitis
Thereitis carlsbergi

description: Thereitis carlsbergi n. sp.
Figs 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 comes from Rødvig, while paratype MGUH 33205 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.
description: Published as part of Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, pp. 1-196 in Zootaxa 4654 (1) on pages 114-115, DOI: 10.11646/zootaxa.4654.1.1, http://zenodo.org/record/3365803