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(De Ribero de Dibi et al. 2001). a-b, Inapertisporites sp; c, Monoporisporites sp.; d-e-f, Polyporisporites sp.; g, Hypoxylonites sp.; h, Lacrimasporonites sp.; i, Diporisporites sp.; j, Exesisporites sp.; k-l, Dicellaesporites sp.; m, Delitschia sp.; n, Dyadosporites sp.; o, Forma A; p, Forma B; q, Forma C.
Source publication
Anta Formation (Miocene), Metán Subgroup (Orán Group), in río Piedras, Salta Province. Palynological data . Deposition of the Salta Group (Cretaceous-Paleogene) terminated in the mid Eocene - Inca Diastrophic Phase. Following a compressive tectonic event in the Central Andes, this was succeeded by deposition of Metán Subgroup, divisible into Río Se...
Citations
Despite a global fossil record, Metatheria are now largely restricted to Australasia and South America. Most metatherian paleodiversity studies to date are limited to particular subclades, time intervals, and/or regions, and few consider uneven sampling. Here, we present a comprehensive new data set on metatherian fossil occurrences (Barremian to end Pliocene). These data are analyzed using standard rarefaction and shareholder quorum subsampling (including a new protocol for handling Lagerstätte-like localities).
Global metatherian diversity was lowest during the Cretaceous, and increased sharply in the Paleocene, when the South American record begins. Global and South American diversity rose in the early Eocene then fell in the late Eocene, in contrast to the North American pattern. In the Oligocene, diversity declined in the Americas, but this was more than offset by Oligocene radiations in Australia. Diversity continued to decrease in Laurasia, with final representatives in North America (excluding the later entry of Didelphis virginiana ) and Europe in the early Miocene, and Asia in the middle Miocene. Global metatherian diversity appears to have peaked in the early Miocene, especially in Australia. Following a trough in the late Miocene, the Pliocene saw another increase in global diversity. By this time, metatherian biogeographic distribution had essentially contracted to that of today.
Comparison of the raw and sampling-corrected diversity estimates, coupled with evaluation of “coverage” and number of prolific sites, demonstrates that the metatherian fossil record is spatially and temporally extremely patchy. Therefore, assessments of macroevolutionary patterns based on the raw fossil record (as in most previous studies) are inadvisable.
The El Foyel Group is defined in the western section (Andean) of the Ñirihuau Basin, Argentina (41°44′S-71°30′W). It consists of three units: the Troncoso, Salto del Macho and Río Foyel formations. The age of the group and of the formations is still controversial. We studied the fungal remains recovered from 14 palynological samples from outcrops in the group with the intention of providing data to solve this problem. The fungal assemblage found is highly diverse and it is mostly composed of spores of different affinities (mainly ascomycetes). We identified 38 species from 18 genera (Anatolinites, Dictyosporites, Didymoporisporonites, Diporicellaesporites, Diporisporites, Dyadosporites, Exesisporites, Foveodiporites, Hypoxylonites, Inapertisporites, Lacrimasporonites, Monoporisporites, Multicellites, Papulosporonites, Pluricellaesporites, Polycellaesporonites, Staphlosporonites and one indet.). Moreover, we propose two new species (Hypoxylonites foyelensis sp. nov. and Pluricellaesporites patagonicus sp. nov.) and a new combination (Dyadosporites annulatus comb. nov.). Most of the species were recovered from samples from the Troncoso Formation (21), while the Salto del Macho and Río Foyel formations showed lesser diversity. Anatolinites subcapsilaris, Dyadosporites subovalis, Inapertisporites subovoideus, Monoporisporites singularovalis and Multicellites ellipticus, biomarkers from the Middle Eocene appeared in the Troncoso and Salto del Salto del Macho formations; whereas indicators of the Eocene-Oligocene, such as Dyadosporites elsikii, Didymoporisporonites panshanensis, Foveodiporites elegans, Lacrimasporonites fusoides and Multicellites leptaleus, were mainly recorded in the Río Foyel Formation. The appearance of the biomarkers mentioned above reinforces the Palaeogene age proposed for the El Foyel Group in previous palynological studies. The record of Hypoxylonites ater (Miocene) in the Salto del Macho formation would expand its range as far back as the Palaeogene.
