Trilobitoceras peculiaris, 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 : 95-96

Trilobitoceras peculiaris gen. et sp. nov.

urn:lsid:zoobank.org:act:D75CCA9E-1207-4384-8848-3AF713D0D894

Figs 23–24 , Table 13

Diagnosis

Species of Trilobitoceras gen. nov. with moderately depressed whorl profile (ww/wh ~ 1.65). Suture line with a broadly rounded median saddle.

Etymology

From the Latin ‘ peculiaris ’, meaning ‘peculiar’ and referring to the unusual conch shape.

Type material

Holotype ALGERIA • Mouydir , south of Oued Temertasset (locality MOU-Z); Argiles de Teguentour (Upper Pericyclus-Progoniatites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; illustrated in Fig. 23A ; MB.C.30477.

Paratype ALGERIA • 1 specimen; Mouydir , south of Oued Temertasset (locality MOU-D1); Argiles de Teguentour (Upper Pericyclus-Progoniatites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; illustrated in Fig. 23B ; MB.C.30478 .

Description

Holotype MB.C.30477 is a phragmocone fragment with almost half a whorl length ( Fig. 23A ). It has a depressed whorl profile (ww/wh= 1.63) with a broadly rounded venter characterised by two deep and wide ventral grooves. The flanks are almost parallel in their middle and the umbilical wall is almost flat ( Fig. 24A ). The suture line, whose course is determined by the shape of the whorl profile, has a very wide external lobe in which a low, broadly rounded median saddle rises ( Fig. 24B ).

Paratype MB.C.30478 is a fragment consisting of only two chambers of the phragmocone ( Fig. 23B ). The conch geometry is very similar to the holotype, although the ww/wh ratio is slightly higher with a value of 1.72. ( Fig. 24C ) The suture line is also similar to the holotype; however, the specimen also shows the rather narrow, rounded V-shaped internal lobe ( Fig. 24D ).

Remarks

Trilobitoceras peculiaris gen. et sp. nov. has a very similar conch morphology like T. planidorsale , but differs in the course of the suture line: T. peculiaris gen. et sp. nov. possesses a mid-ventral saddle but T. planidorsale possesses a mid-ventral lobe.

Figures

Fig. 23. Trilobitoceras peculiaris sp. nov. from Oued Temertasset (both Korn et al. 2002 Coll.). A. Holotype MB.C.30477. B. Paratype MB.C.30478. Scale bar units= 1 mm.

Fig. 24. Trilobitoceras peculiaris sp. nov. from Oued Temertasset (both Korn et al. 2002 Coll.). A. Whorl profile of holotype MB.C.30477 (dorsal portion reconstructed). B. Suture line of holotype MB.C.30477, at ww =13.6 mm, wh =7.7 mm. C. Whorl profile of paratype MB.C.30478. D. Suture line of paratype MB.C.30478, at ww =13.6 mm, wh =7.9 mm. Scale bar units =1 mm.

Tables

Table 13. Conch dimensions (in mm) and ratios of Trilobitoceras peculiaris gen. et sp. nov.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZW
MB.C.30477	–	14.3	8.8	–	–	–	1.63	–	–	–
MB.C.30478	–	13.6	7.9	–	–	–	1.72	–	–	–