Maccoyoceras habadraense, Korn & Bockwinkel, 2022

Korn, Dieter & Bockwinkel, Jürgen, 2022, Early Carboniferous nautiloids from the Central Sahara, southern Algeria, European Journal of Taxonomy 831, pp. 67-108 : 101-102

publication ID	https://doi.org/ 10.5852/ejt.2022.831.1871
publication LSID	lsid:zoobank.org:pub:EAA2EAE2-DA8B-4516-B332-CB8423B8EEAA
DOI	https://doi.org/10.5281/zenodo.6903240
persistent identifier	https://treatment.plazi.org/id/CDDB23E7-2380-4600-BCF0-71E3F2159BF2
taxon LSID	lsid:zoobank.org:act:CDDB23E7-2380-4600-BCF0-71E3F2159BF2
treatment provided by	Felipe
scientific name	Maccoyoceras habadraense
status	sp. nov.

Treatment

Maccoyoceras habadraense sp. nov.

urn:lsid:zoobank.org:act:CDDB23E7-2380-4600-BCF0-71E3F2159BF2

Fig. 28 View Fig , Table 16 View Table 16

Diagnosis

Species of Maccoyoceras reaching about 100 mm conch diameter. Conch with weakly depressed whorl profile (ww/wh ~1.10); venter flattened, ventrolateral shoulder narrowly subangular. Whorls just touching the preceding. Ornament in the juvenile stage with few coarse, granulated spiral lines on the flank, in the adult stage without spiral lines. Fine, sharp growth lines on the flank, with weakly biconvex course with a shallow lateral sinus and a moderately high ventrolateral projection. Venter with delicate growth lines with deep sinus.

Etymology

Named after the type locality Hassi Habadra.

Type material

Holotype ALGERIA • Mouydir , west of Hassi Habadra (locality MOU-W); Argiles de Teguentour (HelicocyclusOuaoufilalites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; illustrated in Fig. 28N View Fig ; MB.C.30485 .

Description

Holotype MB.C.30485 is an incomplete specimen with 66 mm conch diameter ( Fig. 28 View Fig ). It allows the study from both sides. The conch is extremely discoidal (ww/dm= 0.34) and evolute (uw/dm =0.46) with a high coiling rate (WER =2.17). The whorl profile is weakly depressed hexagonal (ww/wh =0.93) and widest at the rounded umbilical margin. The flanks converge barely towards the subangular ventrolateral shoulder that separates the flanks from the flattened venter. The umbilical wall is convexly rounded.

There are two ontogenetic stages in the ornament development; the first ranges up to about 35 mm conch diameter and possesses about ten spiral lines on the flank. The second stage does not show spirals but

only fine, narrow-standing growth lines with weakly biconvex course. These are restricted to the flanks, while the venter shows very delicate growth lines forming a very deep sinus.

Remarks

Maccoyoceras habadraense sp. nov. has similarities with M. pentagonum , but has a wider umbilicus (uw/dm = 0.45 in M. habadraense sp. nov. but only 0.40 in M. pentagonum ). Furthermore, the spiral lines are markedly coarser in M. habadraense sp. nov.; this feature also distinguishes the new species from the other species of the genus.