Solenochilus lucynae, Korn & Klug, 2023

Korn, Dieter & Klug, Christian, 2023, Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco), European Journal of Taxonomy 885, pp. 156-194 : 184-186

Solenochilus lucynae sp. nov.

urn:lsid:zoobank.org:act:C87D7BC3-B511-48C4-922B-FCF319D97534

Fig. 19 ; Table 9

Diagnosis

Species of Solenochilus with thickly pachyconic, involute conch (ww/dm ~0.80; umbilicus closed), whorl profile weakly depressed (ww/wh ~ 1.25) with broadly rounded venter and broadly rounded umbilical margin. Coiling rate extremely high (WER ~3.90), whorls moderately embracing (IZR ~ 0.25). Suture line on flanks and venter nearly straight, in dorsal area with deep, V-shaped internal lobe.

Etymology

Named after Lucyna Leda, who found the holotype.

Material examined

Holotype MOROCCO • Anti-Atlas, 18 km south-east of Rissani ; basal Mougoui Ayoun Formation; Leda 2011 Coll.; illustrated in Fig. 19 ; MB.C.31286 .

Paratypes MOROCCO • 2 specimens; Anti-Atlas, region south-east of Rissani ; basal Mougoui Ayoun Formation; Karaoui Coll.; PIMUZ 39509 , PIMUZ 39514 .

Description

Holotype MB.C.31286 is a steinkern specimen with a 72 mm conch diameter, of which the last 120 degrees belong to the body chamber ( Fig. 19 ). The peculiar conch shape with extremely high coiling rate (WER =3.92) can be described as thickly pachyconic (ww/dm=0.82); the whorl profile is characterised by the nearly circular, weakly depressed shape (ww/wh ~1.25) with venter, flanks, umbilical margin and umbilical wall broadly rounded. The embraced area of the preceding whorl is very small, the imprint zone depth is ~0.25. The internal mould is smooth, without traces of ornament. The suture line possesses a very shallow, broadly rounded lateral lobe and a very shallow external lobe.

Paratype PIMUZ 39509 is much smaller at 27 mm dm. The initial chamber is conical with a diameter of ca 4.8 mm. Half of it has broken off, exposing the first septum. The whorl height increase is extreme, while the umbilical width and whorl overlap are very low. The whorl cross section is nearly circular. The first four sutures are nearly straight with a very small and shallow external lobe. Following the fourth septum (ca 14 mm dm), a few weak radial ridges are visible on the flank, which fade out after a few millimetres. Parts of the growth lines are visible on the broadest part of the whorl, where they form a projection (at 15 mm dm).

Remarks

Solenochilus lucynae sp. nov. differs from the other Early Carboniferous species of the genus as follows: S. dorsale and S. hibernicum possess, in contrast to the new species, a slightly opened umbilicus. Solenochilus clausum has an almost closed umbilicus but differs in the more slender conch and hence a narrower whorl profile (ww/wh ~ 0.70) from S. lucynae (ww/wh ~ 1.25).

Figures

Fig. 19. Solenochilus lucynae sp. nov.; holotype MB.C.31286 (Leda 2011 Coll.) from 18 km SE of Rissani; dorsal and lateral views. Scale bar units =1 mm.