Planetoceras destrictum, Korn & Miao & Bockwinkel, 2022

Korn, Dieter, Miao, Luyi & Bockwinkel, Jürgen, 2022, The nautiloids from the Early Carboniferous Dalle à Merocanites of Timimoun, western Algeria, European Journal of Taxonomy 789, pp. 104-129 : 124-125

publication ID	https://doi.org/ 10.5852/ejt.2022.789.1635
publication LSID	lsid:zoobank.org:pub:A475F919-D925-457E-B007-3FE2B55659A3
DOI	https://doi.org/10.5281/zenodo.6302064
persistent identifier	https://treatment.plazi.org/id/42BD8B9E-A638-4C4F-9472-0B0EE6AB489E
taxon LSID	lsid:zoobank.org:act:42BD8B9E-A638-4C4F-9472-0B0EE6AB489E
treatment provided by	Felipe
scientific name	Planetoceras destrictum
status	sp. nov.

Treatment

Planetoceras destrictum sp. nov.

urn:lsid:zoobank.org:act:42BD8B9E-A638-4C4F-9472-0B0EE6AB489E

Figs 12–13 View Fig View Fig ; Table 8 View 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 à Merocanites ” (Tournaisian-Viséan boundary interval); illustrated in Fig. 12 View Fig ; MB.C.30385 .

Description

Specimen MB.C.30385 is a fully chambered specimen with a diameter of 67 mm ( Fig. 12 View Fig ). 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 View Fig ).

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).