Diagnoza
The symmetrical tr element with smooth lateral surfaces, its inner margin sharp, in juveniles with smooth flanks, but in adults they may bear angulations. The ne elements robust , with a deep round incision above the base. All elements hyaline. Porównanie
Two main element types were identified by LINDSTROM(1971), the apparatus reconstruction
has been further developed by VAN WAMEL (1974), LOFGREN (1978), and DZIK (1990). During the evolution of this Drepanodus lineage elements become more and more prominently ornamented along their inner edges. In the Arenig some rare specimens (usually large ones) bear three ridges along this edge but I was not able to find any with more el aborated ornamentation, which is
typical for later D. robustus. Somewhat arbitrarily, I assign to D. arcuatus the se populations transitional to D. robustus that still did not develop five ridges along the inner edge in adult elements.
"Protopanderodus n. sp. A" MCCRACKEN, 1989 from the P. serra Zone of Northern Yukon, Canada, may be a successor of D. arcuatus. Oblique bases make it superficially similar to some species of Protopanderodus which, however, have quite different "platform" series elements and less elaborated apparatuses. Autekologia Występowanie geograficzne
A few specimens of Drepanodus , collected by Dr. Wieslaw BEDNARCZYK from
the limestone bed once exposed in the Bukówka quarry definitely belong to this species. None of the two large tr elements present in the sample has any lateral ridges. However, a specimen
of similar size from the borehole Bukówka IG 1 (depth 83.5-84 m) shows five distinct ridges. This rather exceeds possible population variability and the sample seems thus to be of different age, probably closer to the base of the Mójcza Limestone where similar large elements occur. Somewhat
enigmatic is the presence in both Bukówka samples of a few possible ke elements with a very convex
posterior side and prominent medial rib. There are too few specimens available to statewith certainty whether they belong to another sympatric species of Drepanodus or perhaps they represent ne elements of a species of rotopanderodus.
To D. arcuatus I assign also population s from below the discontinuity surface in Mójcza, with elements usually armed with three sharp ridges. Zasięg czasowy
The typical D. arcuatus is confined to the
Arenig . Materiały muzealne Literatura
Dzik, J. 1994a Conodonts of the Mójcza Limestone. In: J. Dzik, E. Olempska, & A. Pisera. Ordovician carbonate platform of the Holy Cross Mountains. Palaeontologia Polonica 53, 43-128. | 
