Phragmodus sp. aff. "Baltoniodus" crassulus

(Lindstrom, 1955)from the Mójcza Limestone.

Apparatus of Phragmodus sp. aff. "Baltoniodus" crassulus

(Lindstrom, 1955).

Diagnoza

Porównanie

The species is represented in the basal beds of the Mójcza Limestone by poorly preserved specimens. A similarity to cooccurring Baltoniodus makes separation sometimes, at such a state of preservation, difficult. Especially the pIand tr elements are not easy to assign properly to a species unless their internal processes are well preserved. They differ, however, from Baltoniodus in
a less prominent denticulation of the remaining processes. Some morphologically transitional elements
have been found  that are hard to classify. Like the ramiform elements in typical populations of "B. " crassulus the elements from Mójcza also have very long, gently curved cusps. This makes identification of the species rather easy even if the processes are broken. The population from the Mójcza Limestone differs from older populations of "B ." crassulus  in the more robust appearance of the elements, which may be a result of taphonomic selection during sedimentation of the coarse sandy limestone.

Autekologia

Występowanie geograficzne

Zasięg czasowy

Typical "B." crassulus occurs in the topmost Latorpian of the Baltic area, being later replaced by species of the Baltoniodus lineage. In Mójcza and the Myszków borehole (Upper Silesian Massif) it seems to occur as high as in the basal Kundan (up to 0.3 m above the base of the limestone in Mójcza), being replaced here by an early form of P. polonicus. These species are so close morphologically that an evolutionary connection seems possible. Because of stratigraphic condensation of the section and the rarity of specimens in the transitional strata this cannot however, be precisely documented.

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.