Sandbergeroceras tuberculosocostatum ( Sandberger & Sandberger, 1850 )

Korn, Dieter & Bockwinkel, Jürgen, 2021, The pharciceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea), European Journal of Taxonomy 771, pp. 1-79 : 67-71

Sandbergeroceras tuberculosocostatum ( Sandberger & Sandberger, 1850)

Figs 49 , 50C , 51B , 52 ; Table 30

Goniatites tuberculoso-costatus Sandberger & Sandberger, 1850: 64 , pl. 4 fig. 1.

Sandbergeroceras sandbergerorum Miller, 1938: 178 , text-fig. 38a.

Sandbergeoceras tuberculoso-costatum – Hyatt 1884: 333.

Sandbergeroceras tuberculoso-costatum – Foord & Crick 1897: 244, text-fig. 155a–f.

Triaenoceras costatum – Drevermann 1903: 85, pl. 5 figs 1–5.

Sandbergeroceras tuberculosocostatum – Bogoslovsky 1969: 278, text-fig. 92b.

Sandbergeroceras sandbergerorum – House & Ziegler 1977: pl. 6 figs 16–18.

Triainoceras tuberculosocostatum – Korn & Klug 2002: 148, text-fig. 137g.

non Goniatites tuberculoso-costatus – Tietze 1869: 38; 1871: 130, pl. 16 fig. 6.

Diagnosis

Species of Sandbergeroceras with thinly discoidal, subevolute conch at 30 mm dm (ww / dm ~ 0.35; uw/ dm ~0.40). Whorl profile weakly depressed (ww/ wh ~1.10); venter narrowly rounded. Venter becoming subacute at about 40 mm dm. Two shallow spiral grooves on the venter. Shell ornament with 30 almost linear, sharp ribs on the flanks and coarse growth lines.

Material examined

Lectotype (designated here)

GERMANY • Rhenish Mountains, Oberscheld; early Frasnian (Red Ironstone); 28 (Wiesbaden Museum); illustrated by Sandberger & Sandberger (1850 –1856: pl. 4 fig. 1) and House & Ziegler (1977: pl. 6 figs 16–18); Wiesbaden Museum nr. 28. ( Fig. 49A )

Most probably, the illustration of a smaller individual ( Sandberger & Sandberger 1850 –1856: pl. 4 fig. 1a–f) is from the inner whorls of the same specimen.

Additional material

GERMANY • 1 specimen; Rhenish Mountains , Oberscheld; early Frasnian (Red Ironstone); SMF.Mbg.6360 • 1 specimen; Rhenish Mountains , Oberscheld ; early Frasnian (Red Ironstone); Wiesbaden Museum nr. 41 .

Description

Lectotype 28 is an incomplete specimen, without shell remains, with an original conch diameter of more than 70 mm in iron-rich limestone ( Fig. 49A ). The outer whorl is crushed but the inner whorls are rather well-preserved. It allows an insight into the conch ontogeny from the initial stage to the adult stage. Up to about 18 mm diameter, the conch is very evolute; thereafter, the whorl begins to grow in height and the relative width of the umbilicus decreases. At 15 mm diameter, the whorls are broadly kidney-shaped in profile and the venter is broadly rounded. At about 30 mm diameter the whorls are already much higher and at about 45–50 mm diameter apparently already compressed-triangular with a very narrow venter. The inner whorls are apparently unsculptured, but at about 10 mm diameter sharp, initially closely spaced ribs appear; at about 12 mm diameter there are about eight ribs on a quarter whorl. The ribs are present up to a conch diameter of 30 mm; they run almost straight across the flank.

SMF.Mbg.6360: incomplete, slightly distorted specimen of about 75 mm conch diameter in iron-rich limestone with shell remains preserved ( Fig. 50C ). It is a specimen showing the transition from the preadult to the adult stage. It has a diameter of about 75 mm; at this stage the conch has the shape of a lens (ww/ dm ~0.25, uw/ dm ~0.30). The whorl profile is compressed triangular with subacute venter, the coiling rate is very high (WER ~2.45). Almost the entire last whorl is sculptureless; only at the beginning a few folds are visible on the inner half of the flank. Two inner whorls can be partially studied in the umbilicus. They show that the conch is evolute and coarsely ribbed. There are about 30 sharp ribs per whorl.

The suture line shows, at a whorl height of 15.5 mm, a Y-shaped, divided external lobe with very narrow, ventrally somewhat pouched prongs and a median saddle reaching half the height of the lobe ( Fig. 51B ). The ventrolateral saddle is rounded and slightly tilted in the dorsal direction. The lateral lobes are deep and inflated, with a mammiform base. Two more, V-shaped and much smaller umbilical lobes follow on the flank. On the inner flanks and the umbilical wall no portion of the suture line is preserved, but it is likely that more lobes would follow.

Remarks

With the decision of the International Commission of Zoological Nomenclature (1956), at the request of Miller (1952), the species Sandbergeroceras sandbergerorum was declared an objective synonym of S. tuberculosocostatum . This decision was apparently unknown to House (in House & Ziegler 1977), so that he considered S. sandbergerorum valid and designated the Wiesbaden specimen as lectotype. This specimen is determined here as the lectotype of S. tuberculosocostatum .

The suture line shown here significantly differs from the illustration of Sandberger & Sandberger (1850 – 1856: pl. 4 fig. 1f), which had been copied several times ( Foord & Crick 1897; Miller 1938; Bogoslovsky 1969; Korn & Klug 2002). The reason for this difference could be that the latter specimen has been cut too deeply and therefore some features have been lost; the illustrations of specimens as well as suture lines are usually excellent and very accurate in this monograph. The suture line shown here ( Fig. 51B ) is similar to the one published by Bogoslovsky (1969) for “ Triainoceras gerassimovi ”. However, that species has only two lobes on the flank, the somewhat pouched, V-shaped lateral lobe and a somewhat smaller, V-shaped umbilical lobe. Because of this somewhat simpler suture line with fewer elements, the species became the type species of Altayites (Korn & Klug 2002) .

Although the material is incomplete and not well preserved, the species can be reasonably well defined. One problem, however, could be that the specimens do not belong to the same species.

Sandbergeroceras tuberculosocostatum differs from S. costatum in the form of the whorl profile. This is much slenderer in S. tuberculosocostatum (ww/ wh ~ 1.10 in comparison to ~ 1.30 in S. costatum ). Furthermore, the whorl profile begins to flatten with a subacute venter already at about 30 mm conch diameter in S. tuberculosocostatum , while the venter is still rounded in S. costatum .

The main difference to S. archiaci sp. nov. is that the ventrolateral grooves are less pronounced in S. tuberculosocostatum . The umbilicus is, at a comparable diameter, narrower in S. tuberculosocostatum (ww / dm ~ 0.40 in S. tuberculosocostatum but ~ 0.50 in S. archiaci sp. nov.).

Figures

Fig. 49.Sandbergerocerastuberculosocostatum(Sandberger&Sandberger, 1850).A.Lectotype specimen 28 (Wiesbaden Museum) from Oberscheld; photograph and reproduction of the figure in Sandberger & Sandberger (1850–1856: pl. 4 fig. 1). B. Specimen 41 (Wiesbaden Museum) from Oberscheld; specimen of the figure in Sandberger & Sandberger (1850–1856: pl. 8 fig. 2). C. Reproduction of the figure in Sandberger & Sandberger (1850–1856: pl. 4 fig. 1a–c). Scale bar units = 1 mm.

Fig. 50. A. Sandbergeroceras archiaci sp. nov., holotype MB.C.3671 (Koch Coll.) from Oberscheld (Anna Mine). B. Sandbergeroceras costatum (d’Archiac & de Verneuil, 1842), neotype MB.C.7695 (Erbreich Coll.) from Dillenburg.C. Sandbergeroceras tuberculosocostatum (Sandberger & Sandberger, 1850), specimen SMF.Mbg.6360 from Oberscheld. Scale bar units = 1 mm.

Fig. 51. A. Sandbergeroceras costatum (d’Archiac & de Verneuil, 1842), suture line of neotype MB.C.7695 from Dillenburg, at ww =15.7 mm, wh= 12.7 mm.B. Sandbergeroceras tuberculosocostatum (Sandberger & Sandberger, 1850), suture line of specimen SMF.Mbg.6360 from Oberscheld, at ww =13.5 mm, wh =15.5 mm. Abbreviations: see Material and methods. Scale bar units = 1 mm.

Fig. 52. Sandbergeroceras tuberculosocostatum (Sandberger & Sandberger, 1850), reproductions of illustrations in Drevermann (1903). Scale bar units = 1 mm.

Tables

Table 30. Conch dimensions and ratios of selected specimens of Sandbergeroceras tuberculosocostatum (Sandberger & Sandberger, 1850).

Specimen	dm	ww	wh	uw	ah	ww / dm	ww / wh	uw / dm	WER	IZR
SMF.Mbg.6360	74.8	18.8	37.2	22.6	26.8	0.25	0.51	0.30	2.43	0.28
SMF.Mbg.6360	46.5	15.1	14.2	17.8	–	0.32	1.06	0.38	–	–