Planetoceras destrictum Korn & Miao & Bockwinkel 2022, sp. nov

Autor: Korn, Dieter, Miao, Luyi, Bockwinkel, Jürgen
Rok vydání: 2022
Předmět:
DOI: 10.5281/zenodo.6302063
Popis: Planetoceras destrictum sp. nov. urn:lsid:zoobank.org:act: 42BD8B9E-A638-4C4F-9472-0B0EE6AB489E Figs 12���13; Table 8 Diagnosis Species of Planetoceras with moderately depressed, rounded-pentagonal whorl profile (ww/wh ~ 1.65), venter slightly flattened, ventrolateral shoulder broadly rounded. Umbilical margin subangular to narrowly rounded, umbilical wall steep, flattened. Whorls slightly embracing. Etymology After the Latin ��� destrictum ���, meaning ���sharp��� and referring to the angular umbilical margin. Type material Holotype ALGERIA ��� Gourara, Sebkha de Timimoun 14.5 km west-southwest of Timimoun; ���Dalle �� Merocanites ��� (Tournaisian-Vis��an boundary interval); illustrated in Fig. 12; MB.C.30385. Description Specimen MB.C.30385 is a fully chambered specimen with a diameter of 67 mm (Fig. 12). It is a stout, subinvolute conch (ww/dm = 0.76; uw/dm = 0.29) and has a depressed, subtrapezoidal whorl profile with a broadly rounded venter, a rounded ventrolateral shoulder, weakly flattened, slightly converging flanks, a rounded umbilical margin and a rounded umbilical wall. It has a very high coiling rate (WER = 2.59). The specimen shows a morphological change in the shape of the umbilicus. During the last volution of the phragmocone, the umbilical margin changes from subangular to rounded. At the same time, the umbilical wall changes from flattened to rounded. The suture line extends nearly linearly across the venter and possesses a very shallow lobe on the flank (Fig. 13). Remarks Planetoceras destrictum sp. nov. differs from the species described from Belgium, the South Urals and North America in the flattened venter, which is rounded in those species. More similar is P. globatum (Sowerby, 1824), a species with a very similar whorl profile (Histon 1999) but a more slender conch (ww/dm ~ 0.55 at 58 mm dm) than P. destrictum sp. nov. (ww/dm ~ 0.76 at 67 mm dm). Planetoceras transforme sp. nov. (described below) has a much stouter conch (ww/dm ~ 0.85).
Published as part of Korn, Dieter, Miao, Luyi & Bockwinkel, J��rgen, 2022, The nautiloids from the Early Carboniferous Dalle �� Merocanites of Timimoun, western Algeria, pp. 104-129 in European Journal of Taxonomy 789 on pages 124-125, DOI: 10.5852/ejt.2022.789.1635, http://zenodo.org/record/5965355
{"references":["Histon K. 1999. A revision of A. H. Foord's monograph of Irish Carboniferous nautiloid cephalopods (1897 - 1901). Part 2. Monographs of the Palaeontographical Society 153: 63 - 129."]}
Databáze: OpenAIRE
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