The pharciceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea)
Author
Korn, Dieter
286CA4F3-7EBC-4AEF-A66A-B2508D001367
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany.
dieter.korn@mfn.berlin
Author
Bockwinkel, Jürgen
F7FE7EEA-B678-4FEE-879C-8C429F66BF3A
Dechant-Fein-Strasse 22, 51375 Leverkusen, Germany.
jbockwinkel@t-online.de
text
European Journal of Taxonomy
2021
2021-09-23
771
1
79
http://dx.doi.org/10.5852/ejt.2021.771.1503
journal article
4091
10.5852/ejt.2021.771.1503
d4ff05b4-fdac-44e8-8c2e-0733a93169a0
2118-9773
5536097
9FAB6919-E4AC-44A6-89AB-2E236F55FDB5
Sandbergeroceras archiaci
sp. nov.
urn:lsid:zoobank.org:act:
CA8E6D62-FBEF-45A7-B4F9-2C914A45B54D
Fig 50A
;
Table 32
Diagnosis
Species of
Sandbergeroceras
with thinly discoidal, evolute conch at
30 mm
dm (ww/ dm ~ 0.35; uw/ dm ~ 0.50). Whorl profile moderately depressed (ww/ wh ~1.55); venter flatly rounded. Two deep spiral grooves on the venter. Shell ornament with 30 sigmoidal, sharp ribs on the flanks and coarse growth lines.
Etymology
Named after Étienne Jules Adolphe Desmier de Saint-Simon, Vicomte d’Archiac (1802–1868), one of the pioneers of studying fossils from the Red Ironstone.
Material examined
Holotype
GERMANY
•
Rhenish Mountains
,
Oberscheld
(Grube Anna);
early Frasnian
(Red Ironstone);
Koch
Coll.;
MB.C.3671
.
Description
Holotype
MB.C.3671 is an incomplete, but rather well-prerserved specimen of
33 mm
conch diameter in fossil-rich and iron-rich limestone (
Fig. 50A
). It allows the study of slightly more than two whorls up to a conch diameter of
33 mm
. The conch is discoidal and evolute (ww / dm =0.35; uw / dm = 0.51)
Table 32.
Conch dimensions and ratios of selected specimen of
Sandbergeroceras archiaci
sp. nov.
| Specimen |
dm |
ww |
wh |
uw |
ah |
ww / dm |
ww / wh |
uw / dm |
WER |
IZR
|
| MB.C.3671 |
31.1 |
11 |
7.05 |
15.9 |
5.8 |
0.35 |
1.56 |
0.51 |
1.51 |
0.18 |
with low coiling rate (WER =1.51); the whorl profile depressed (ww / wh =1.56) with continuously rounded umbilical wall, flanks and venter. The venter bears two rather deep spiral grooves. Both whorls bear rounded, forward-directed ribs; there are 30 such ribs on the last whorl and 40 on the penultimate. In addition, sharp growth lines are formed at almost equal intervals of about
0.2 mm
. They extend almost straight across the flank and curve forward to a moderately high projection in the ventrolateral area.
Remarks
Sandbergeroceras archiaci
sp. nov.
differs from
S. tuberculosocostatum
and
S. costatum
in the form of the whorl profile and the umbilical width. The whorl profile is rounded-triangular with a tightly rounded venter in the latter two species, whereas the venter is weakly flattened in
S. costatum
. The ventrolateral grooves are less pronounced in
S. tuberculosocostatum
and
S. costatum
. The umbilicus is, at
30 mm
conch diameter, wider in
S. costatum
(ww/ dm ~
0.50 in
S. costatum
but only ~
0.40 in
S. tuberculosocostatum
and
S. costatum
).