Opis

P1 elements of the apparatus usually with icrion on the external process, elements of the S series more or less reduced, simplified morphologically and bearing processes with unmineralized bases of denticles.
The icriodontids have their roots in the Ordovician and the original aspect of their apparatus is a triramous P1 element with icrion on its probably ventral process and a set of ramiform complex elements similar to other prioniodontids but with a tendency to reduce denticulation in some of them or separate particular denticles on the processes that became less and less mineralized. At the beginning of the Devonian this change was already advanced, the anterior process in P1 element being represented only by an expansion of the base, but the dorsal process still preserved denticulation. The Devonian lineage of Latericriodus with this kind of apparatus continued until the mid-Givetian represented there by its type species. A further reduction of the dorsal process in the late Emsian resulted in the emergence of the lineage of Icriodus, with only one process represented in the P1 element. This branch continued to the mid Famennian, in some parts of its occurrence represented by several separate lineages. Meanwhile additional processes with icrion developed in offshoots of Latericriodus or the icrion was replaced with a single row denticles in others. As a result of the disapearance of the icrion in the late Frasnian, the lineage of Pelekysgnathus originated. Probably from this lineage emerged conodonts lacking the P series elements at all and, in replacement, changing their coniform elements of the rest of the apparatus into robust structures, eventually developing a kind of icrion (Fungulodus). Rare specimens from the Famennian of the Holy Cross Mountains seem to document the evolution from Latericriodus to the late Famennian Antognathus, but also the early evolution of Pelekysgnathus and apparatuses composed exclusively of ‘simple cones’ 

Synonimy

Zasięg czasowy

Llanvirn-Famennian

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.