Vestinautilus padus, 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 : 121-122

Vestinautilus padus sp. nov.

urn:lsid:zoobank.org:act:9743A462-BB55-45D0-9BA6-1C1AB43DE9DC

Fig. 10 ; Table 6

Etymology

After the Latin nomen ‘ padus ’, meaning ‘twine, yarn’ and referring to the conch shape like a yarn reel.

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. 10 ; MB.C.30383 .

Diagnosis

Species of Vestinautilus with strongly depressed, rounded-trapezoidal whorl profile (ww/wh ~ 2.10), venter broadly arched, ventrolateral shoulder defined by an angular margin produced by a broad ridge. A second, sharper ridge is located on the umbilical wall near the ventrolateral shoulder. Whorls weakly embracing, coiling very high (WER ~ 2.55). Ornament with delicate growth lines.

Description

Holotype MB.C.30383 is a rather well-preserved specimen with a diameter of 34 mm ( Fig. 10 ). It is a subevolute conch (ww/dm = 0.90; uw/dm = 0.33) with a very high coiling rate (WER = 2.57). The diameter of the umbilical window is about 5 mm. The whorl profile is strongly depressed (ww/wh = 2.11) and rounded-trapezoidal in outline with a broadly arched venter. The flanks and the venter are fused together; they are separated from the convex umbilical wall by two longitudinal ridges, which are separated by a shallow longitudinal groove. While the outer of the two ridges is subangular in cross section, the inner one is sharp and probably raised only by shell material. The shell ornament consists of delicate growth lines, which are reinforced on the inner longitudinal ridge.

Remarks

Vestinautilus padus sp. nov. belongs to the species of the genus that possess a very broad whorl profile (ww/wh> 2.00) and an ornament with only a few spiral ridges. In this respect, V. cariniformis ( Sowerby, 1825) , V. paucicarinatus ( Foord, 1891) , V. pinguis ( de Koninck, 1844) and V. semiplicatus are similar, but these four species have a concave venter at least in some phases in ontogeny ( Sowerby 1825; de Koninck 1844; Foord 1891, 1900). Subvestinautilus crassimarginatus ( Foord, 1900) and S. crateriformis ( Foord, 1900) have a convex venter in all stages ( Foord 1900), but they do not have the spiral ridges that are characteristic for V. padus sp. nov.

Figures

Fig. 10. Vestinautilus padus sp. nov., holotype MB.C.30383. Scale bar units = 1 mm.

Tables

Table 6. Conch dimensions (in mm) and ratios of Vestinautilus padus sp. nov.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZW
MB.C.30383	33.5	30.2	14.3	11.1	12.6	0.90	2.11	0.33	2.57	0.12