INGEOSUR   20376
INSTITUTO GEOLOGICO DEL SUR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A taxonomic revision of the Paleogene dinoflagellate subfamily Wetzelielloideae: the ?hole? story
Autor/es:
WILLIAMS, GRAHAM L. ; DANASSA SARAH; A FENSOME, ROBERT; GUERSTEIN, G.R.
Lugar:
Mendoza
Reunión:
Congreso; IV INTERNATIONAL PALAEONTOLOGICAL CONGRESS; 2014
Institución organizadora:
International Palaeontological Association
Resumen:
Fossil dinoflagellate cysts of the Paleogene peridiniacean subfamily Wetzelielloideae have a stable tabulation pattern similar to that of other fossil peridiniaceans, but distinguished by a dorsal epicystal tabulation focussed around a four-sided (quadra), rather than a six-sided (hexa) 2a plate. For morphological features aside from tabulation, wetzelielloideans show great variability, especially in horn development and ornamentation, but also in degree of cavation. This diversity has distracted attention from the morphological variation of the archeopyle, which is always formed through loss of the 2a plate only and which we consider to be the most important feature in unravelling the group?s phylogeny. Critical factors are the shape and relative dimensions of the archeopyle and whether the operculum is attached (adnate) or detached. These parameters allow us to define five archeopyle types: equiepeliform, hyperepeliform, hypersoleiform, latiepeliform and soleiform. Based on archeopyle type, we can recognize six genera with an equiepeliform archeopyle, five with a soleiform archeopyle, four with a hyperepeliform archeopyle, three with a latiepeliform archeopyle and one with a hypersoleiform archeopyle. We have generally used ornamentation type and distribution as a secondary defining criterion for genera. The earliest-known wetzelielloideans, which occur around the Thanetian-Ypresian (Paleocene-Eocene) boundary, have an equiepeliform archeopyle. Other archeopyle types evolved rapidly; taxa with hyperepeliform, latiepeliform and hypersoleiform types are known from the Ypresian. Latiepeliform and hyperepeliform types are restricted to the Ypresian and Lutetian. Forms with a soleiform archeopyle appear in the late Lutetian, but are rare until the Bartonian, when they come to dominate wetzelielloidean assemblages and are the exclusive types in Priabonian and younger strata. The subfamily became extinct in the middle Oligocene. As part of our revision of the Wetzelielloideae, we propose 12 new genera and numerous new combinations