The nautiloids from the Early Carboniferous Dalle à Merocanites of Timimoun, western Algeria Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz Institut for Research on Evolution and Biodiversity, Invalidenstrasse 43, 10115 Berlin, Germany. State Key Laboratory of Biogeology & Environmental Geology, School of Earth Sciences, China University of Geosciences, 388 Lumo Road, Wuhan, China. Dechant-Fein-Strasse 22, 51375 Leverkusen, Germany. dieter.korn@mfn.berlin Author Miao, Luyi 2171F5FC-45B5-452B-A134-CD1308B3A085 miaoluyi@cug.edu.cn Author Bockwinkel, Jürgen F7FE7EEA-B678-4FEE-879C-8C429F66BF3A jbockwinkel@t-online.de text European Journal of Taxonomy 2022 2022-01-28 789 104 129 http://dx.doi.org/10.5852/ejt.2022.789.1635 journal article 20812 10.5852/ejt.2022.789.1635 338a1525-2dbe-4c49-99b9-737a0b17334d 2118-9773 5965355 A475F919-D925-457E-B007-3FE2B55659A3 Planetoceras transforme sp. nov. urn:lsid:zoobank.org:act: CDD3B745-0819-4EA2-8728-D0CAB8CE609B Fig. 14 ; Table 9 Diagnosis Species of Planetoceras with moderately depressed, rounded-pentagonal whorl profile (ww/wh> 2.00), venter slightly flattened, ventrolateral shoulder broadly rounded. Umbilical margin changes Table 9. Conch dimensions (in mm) and ratios of Planetoceras transforme sp. nov.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZW
MB.C.30386	43.8	37.4	18.0	11.8	16.5	0.85	2.08	0.27	2.57	0.08
MB.C.30386	27.8	23.0	11.1	10.2	10.3	0.83	2.07	0.37	2.52	0.07

from subangular to rounded, umbilical wall steep, changing from flattened to rounded. Whorls slightly embracing. Etymology After the Latin ‘ transforme ’, meaning ‘changing’, because of the rapid early ontogenetic change in morphology. 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. 14 ; MB.C.30386 . Description Holotype MB.C.30386 consists of the first whorl with a diameter of about 28 mm ( Fig. 14A ) and a fragment of the second whorl making a total diameter of 44 mm ( Fig. 14B ). The conch is stout and has a subtrapezoidal whorl profile at 28 mm in diameter and an angular umbilical edge raised by a sharp keel. A vertical, flattened umbilical wall extends from here on one side and a converging flank on the other. At a short distance from the umbilical margin there is a pronounced but rounded ventrolateral shoulder. On the broad, slightly flattened venter there is a shallow longitudinal furrow next to the ventrolateral shoulder. Half a whorl before, at about 16 mm in diameter, the whorl profile is oval and depressed; at this diameter four longitudinal ridges are present. Of these, the innermost one becomes the ridge on the umbilical margin during the next half whorl, and the second one becomes the ridge at the inside of the ventrolateral shoulder. The third and fourth ridges become weaker and disappear on the next half whorl. The suture line extends almost straight across flanks and venter. The fragment of the larger whorl shows that the umbilical margin became rounded at 44 mm conch diameter ( Fig. 14B ). Fig. 14. Planetoceras transforme sp. nov. , holotype MB.C.30386. A . Photograph of the inner whorl. B . Whorl profile of a larger phragmocone segment. Scale bar units = 1 mm. Remarks Planetoceras transforme sp. nov. differs from the other species of the genus in the very broad whorl profile (ww/wh> 2.00), which has a value of about 1.60 in other species such as P. destrictum sp. nov. and P. globatum ( Histon 1999 ) .