Apparatus of Venoistodus venustus (Stauffer, 1935)

Diagnoza

The M elements with cusps of almost the same length as the base, S elements with sharp flat ribs along the external margin.

Porównanie

Like in all other known occurrences of the M elements of this species there are no other elements in the Mójcza Limestone that could be easily matched with them on the basis of common occurence with expected frequency (that is dominating in numbers over the ne elements) . However, in two samples, singular minute elements have been found that are identical with those proposed by Nowlan et al. ( 1988) to belong to the apparatus of "Oistodus' venustus Stauffer, 1935. This reconstruction seems more probable than the alternative one that the rest of the apparatus of the species is identical with Drepanoistodus. The unusually high abundance of Melements may result from their small size and special hydrodynamic properties. Löfgren (2006) proposed separate name for Baltic populations of such morphology.

Autekologia

Występowanie geograficzne

Zasięg czasowy

In Mójcza the species occurs from the level immediately below the bentonite (P.anserinus Zone) up to the top of the section. It may possibly occur also below the discontinuity but there the ne elements of this morphology are difficult to separate from associated Drepanoistodus species. In the North American Mid continent the species is common in the Lat e Ordovician while in the North Atlantic realm it seems to range from Arenig to Ashgill.

Materiały muzealne

Literatura

Dzik, J. 1994. 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. 

Löfgren, A. 2006. An Oistodus venustus-like conodont species from the Middle Ordovician of Baltoscandia. Paläontologische Zeitschrift 80, 12-21.