Diagnoza

The M elements robust, with almost flat surfaces along the posterior external ridge .
Mature elements prominently costate, the S₀ element usually bear five inner ribs (even in some juveniles). All the elements hyaline with rudimentary white matter .

Porównanie

The apparatus of D. robustus is of the same organization as that of D. arcuatus. The only difference consists in the ornamentation of the inner margins of mature elements. There are populations transitional between these two species but the evolutionary relations hips between them are far from being clarified. They probably formed a network of allopatric, independently evolving lineages that occasionally interbred until a complete separation of the lineages at an unknown level of the Darriwilian, when along with the D. robustus lineage another line, leading from D. arcuatus to D. santacrucensis  was established. Juvenile elements of these species are hardly distinct morphologically. In consequence of a high developmental and population variability it is also not always possible to separate some morphologically close element types within the symmetry transition series .

Autekologia

Występowanie geograficzne

Mójcza, Holy Cross Mts.

Zasięg czasowy

At the discontinuity surface in the Mójcza Limestone and continues as high above as to 1.8 m above the bentonite (A. tvaerensis/superbus transition zone). Rare,specifically unidentifiable elements of Drepanodus occur sporadically even higher in the section.

Materiały muzealne

ZPAL

Literatura

Bergström, S.M. 2007. Middle and Upper Ordovician conodonts from the Fågelsång GSSP, Scania, southern Sweden. Geologiska Föreningens i Stockholm Förhandlingar 129, 77–82.

Dzik, J. 1994. Conodonts of the Mójcza Limestone. In: Dzik, J., Olempska, E., & Pisera, A. Ordovician carbonate platform ecosystem of the Holy Cross Mountains. Palaeontologia Polonica 53, 43–128.