Opis

A tendency to bifurcate processes of S elements starting from S1 and expanding towards S4, all elements more or less arched in profile view, M-elements tending to develop A-shaped appearance, triramous symmetrical element of the apparatus.
This is a well-defined clade but difficult to diagnose morphologically. The branch probably started with a Mehlina-like (or Pandorinellina-like, depending of which morphology of M elements is primitive) ancestral form having arched profile of denticulation in P1 elements, strongly aborally bent external process in S elements and a rather prominent external process in M elements. From this hypothetical form (similar to Vogelgnathus proclinatus) as a result of diminution of the adult size (paedomorphosis) the lineage of Vogelgnathus emerged characterized by a surprisingly primitive appearance of the apparatus for the late Devonian. Urbanekodina undata seems to be the end member of this evolutionary trend, with its elements showing a bizarre mixture of palmatolepidid and spathognathodontid aspects.
The lineage of Francodina at its beginning preserved large size of elements inherited from a P.? vogelgnathoides-like ancestor. The prioniodinid-like apparatuses of Francodina species probably originated as a result of released developmental control of the element morphology. The most surprising aspect of this is the transformation of M elements, otherwise the most morphologically stable element in the post-Ordovician conodont apparatuses. In advanced F. franconica both its processes achieved a similar length, the external process becoming ribbon-like in Sweetodina lagoviensis. The most unusual aspect of the apparatus of Planadina plana is the undenticulated internal process of M elements – the situation opposite to that typical for virtually all ozarkodinine conodonts (but similar to the Ordovician prioniodontids, e.g., Prioniodus elegans). Despite its seemingly Ligonodina-like appearance it is apparently a francodinid, and its prominent external process originated by modification of a ribbon-like structure similar to that of S. lagoviensis. 

Synonimy

Zasięg czasowy

Literatura

Dzik, J. 2006. The Famennian „Golden Age” of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359.