Terebratula Daleidensis - Royal Belgian Institute of Natural Sciences

62 Paul SARTENAER
Fig. 1 –
Oligoptycherhynchus hexatomus (SchnuR, 1851). Camera lucida drawings of serial transverse sections; figures are
distances in mm forward of the ventral umbo. IRScNBa12712. Üxheim (Hillesheim Syncline, lower Nohn Beds, upper
Lower Eifelian). Measurements: length = 16.3 mm; width = 21.7 mm; thickness = 15.8 mm.
Trigonirhynchia CoopeR, 1942 differs from
Oligoptycherhynchus in most characters. The genus is
only mentioned here, because Schmidt (1965, p. 6),
although underlining obvious differences, considered
that Camarotoechia daleidensis and C. hexatoma had
some features (outline, profile, costae) in common with
its type species Trigonirhynchia fallaciosa Bay l e,
1878 (Pragian, Armorican Massif).
Stratigraphic position and geographic location
In a remote past, Oligoptycherhynchus daleidensis
has been mentioned in the type area (Daleiden
“Muldengruppe” and adjoining region of the Grand
Duchy of Luxembourg = type area stricto sensu, and
Prümer Syncline = type area lato sensu) from the
“Spiriferensandstein”, the Daleiden-, Eifel-, Hierges-,
Rhine (Rhenish)-, and Waxweiler-“Grauwacke”, and
from the Daleiden-Waxweiler beds. A more precise
lithostratigraphic unit, covering the upper part of the
“Grauwacke”, the “Oberk(c)oblenzschichten” came
progressively in use.
O. daleidensis is now restricted to the Upper
Emsian Wiltz Beds (“Wiltz-Schichten”), of which it is
a characteristic species (see e.g. StRuve, 1964, p. 227;
WeRneR, 1980, p. 14; KowalSki, 1983, p. 101).
The presence of the species in Germany outside
the type area has still to be substantiated. The undue
importance given to a given number of median costae
4
), considered the most important character, if not the
(
3
only one, of O. daleidensis, has led to the assignment
to that species of a long string of Siegenian and
Emsian forms. No specimen has been spotted in the
various collections examined by the author. Evidence