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Heterochrony in the evolution of Late Devonian Ammonoids

100%

Korn D.

Acta Palaeontologica Polonica

1992

tom 37

nr 1

21-36

n the goniatite family Prionoceratidae, the transition from Mimimitoceras to Balvia provides an example of rapid size decrease resulting from progenesis. In the Prionoceras-Mimimitoceras stock the adult conch continued to be of rather uniform shape and size (about 60 mm) and species diversification was expressed mostly in changing juvenile morphology. In the Balvia branch, which had developed in the Wocklumeria Stufe, the adult size diminished strongly (not more than 16 mm). Progenetic Balvia displays conch morphology of ancestral Mimimitoceras juveniles, with distinct ornamentation types that were added terminally.

Evolution of the Goniatitaceae and Visean-Namurian biogeography

100%

Korn D.

Acta Palaeontologica Polonica

1997

tom 42

nr 2

177-199

Evolutionary lineages within the Carboniferous ammonoid superfamily Goniatitaceae can be recognized using cladistic and stratophenetic analyses, showing that both approaches lead to coinciding results. In the late Viséan and Namurian A, ammonoid provinces can be defined by the distribution of lineages within the goniatite superfamily Goniatitaceae. The first province corresponds to the Subvariscan Realm (where the superfamily became extinct near the Viséan-Namurian boundary), and the second embraces the majority of the occurrences, e.g. the south urals, central Asia, and North America (where the superfamily with different independent lieages continued up into the late Namurian A). In the Viséan, the superfamily was, in two short epochs, globally distributed with major transgressions, which probably led to migration events. The first is at the end of the late Viséan A (G. fimbriatus and G. spirifer Zones, when the genus Goniatites had a world-wide distribution with various species), and the second at the beginning of the late Viséan C (L. poststriatum Zone, when Lusitanoceras is globally distributed).

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Korn D.

1 1997

1 1992

Wyniki wyszukiwania

Heterochrony in the evolution of Late Devonian Ammonoids

Evolution of the Goniatitaceae and Visean-Namurian biogeography