Eoplacognathus zgierzensis Dzik, 1976 from the Mójcza Limestone.

Apparatus of Eoplacognathus zgierzensis Dzik, 1976.

Diagnoza

The elements P₁ with the inner lobe of the anterior process approximately two times longer than the remaining lobe; the anterior process in dextral P₂ element shorter than the remaining ones.

Porównanie

This is the oldest species of the genus, different from its predecessor Lenodus variabilis solely in an elongation of the inner lobe of the anterior process (the diagnostic feature of Eoplacognathus ) and in a denticulated internal process in the M element. Its successor, E. pseudoplanus, has the inner lobe of the anterior process elongated even further, to a degree typical for most species of the genus, while the elongation of the anterior process in the P₂ elements starts from still younger E. suecicus . The degree of development in denticulation of the M elements vary rather randomly among samples. This , together with a generally incomplete preservation of the P₁ elements, hampers any biometrical study, thus not allowing clarification of the relationship with Lenodus, which precedes the species stratigraphically in Mójcza and the Baltic sections.

Autekologia

Występowanie geograficzne

Mójcza; Baltic region and Argentina.

Zasięg czasowy

In Mójcza the species appears 0.5 m below the discontinuity, where it cooccurs with Sagittodontina kielcensis. The transition to E. pseudoplanus cannot be traced in Mójcza because it corresponds to the hiatus, which covers also the range of E. pseudoplanus, E.suecicus, at least partially E. foliaceus, and probably a major part of the range of E. reclinatus.

Materiały muzealne

ZPAL

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.