Lentitornoceras materni, Korn & Bockwinkel, 2022

Korn, Dieter & Bockwinkel, Jürgen, 2022, The tornoceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea), European Journal of Taxonomy 806, pp. 32-51 : 45-46

publication ID	https://doi.org/ 10.5852/ejt.2022.806.1699
publication LSID	lsid:zoobank.org:pub:A2B2A310-8C8C-41B0-B934-1666129B7D90
DOI	https://doi.org/10.5281/zenodo.6380557
persistent identifier	https://treatment.plazi.org/id/267ABA4A-0287-4DEA-B888-4D391FB8D96D
taxon LSID	lsid:zoobank.org:act:267ABA4A-0287-4DEA-B888-4D391FB8D96D
treatment provided by	Felipe
scientific name	Lentitornoceras materni
status	gen. et sp. nov.

Treatment

Lentitornoceras materni gen. et sp. nov.

urn:lsid:zoobank.org:act:267ABA4A-0287-4DEA-B888-4D391FB8D96D

Fig. 8 View Fig ; Table 4 View Table4

Diagnosis

Lentitornoceras gen. nov. reaching about 45 mm conch diameter. Extremely discoidal and involute adult stage (ww/dm ~ 0.25; umbilicus nearly closed at 30 mm dm); whorl profile strongly compressed (ww/ wh ~ 0.40); whorl expansion rate moderate (WER ~ 1.80). Flanks weakly convex, umbilical margin continuously rounded, venter very narrowly rounded. Ornament with lamellar, wide-standing biconvex growth lines.

Type material

Holotype GERMANY • Rhenish Mountains , Oberscheld ; late Givetian (from a Red Ironstone block together with Pharciceras oberscheldense ); Lotz 1901–1902 Coll.; illustrated in Fig. 8 View Fig ; MB.C.30413 .

Etymology

After Hans Matern, to honour his studies on the ammonoids from the Dillenburg region.

Description

Only the holotype is available for description and illustration. It is a specimen of almost 30 mm diameter in iron-rich limestone, largely preserved with its shell ( Fig. 8A View Fig ). The shape is that of a flat lens; the ww/ dm ratio is less than 25%. The umbilicus is almost completely closed; it is bounded by a very shallow umbilical margin. The flanks are slightly convex and converge slightly to the very narrowly rounded venter. The shell bears widespread, lamellar-appearing growth lines, which are biconvex with distinct dorsolateral projection and higher ventrolateral projection across the flank; the ventral sinus is narrow and deep ( Fig. 8C View Fig ). The growth lines are coarser on the venter than on the flanks. The suture line is

typically tornoceratid with a wide, asymmetric adventive lobe, a narrow ventrolateral saddle and a small external lobe ( Fig. 8B View Fig ).

Remarks

Lentitornoceras materni gen. et sp. nov. can hardly be confused with another species from the red ironstone because of its peculiar conch morphology. Tornoceratids from other localities and stratigraphic horizons usually have a much more broadly arched venter. A comparable form is the late Givetian ‘ Lobotornoceras bensaidi ’ ( Bockwinkel et al. 2013a) ; however, this form has a suture line with a very shallow adventive lobe.