Plant assemblages from SW Gondwana: further evidence for high-latitude vegetation in the Devonian of Argentina

Abstract

Plant assemblages are described from the Talacasto and Punta Negra Formations, San Juan Province, the Argentine Precordillera. A detailed facies study involving trace fossil assemblages indicates that the plants were buried in shallow low-to high-energy marine environments, but not in turbidites as previously postulated. Apart from a single specimen resembling Cooksonia from the Lochkovian Talacasto Formation, the abundant compression fossils consist of short lengths of smooth axes, occasional defoliated lycopod stems, and very rare isolated sporangia. It is thus impossible to assign any to existing taxa with confidence nor are there sufficient distinguishing characters to erect new ones. Although the possible age of the formations in the Precordillera remains conjectural, the fossils themselves, even preserved in such fragmentary states, indicate much lower grades of organization than seen in coeval assemblages elsewhere, particularly on the Laurussian and South China palaeocontinents. Palaeocontinental reconstructions of Gondwana indicate that the localities are within 308 of the palaeo South Pole. Thus a global latitudinal gradient in vegetation is postulated for the Early Devonian with decreasing disparity and diversity at higher latitudes. An explanation for the latter is explored in terms of light regime and temperature in highly stressed environments.

Mid-Late Devonian assemblages of herbaceous lycophytes from northern Argentina and Bolivia: Age assessment with palynomorphs and invertebrates and paleobiogeographic importance

“…Limachi et al, 1996;di Pasquo et al, 2009;Edwards et al, 2009;Matsumura et al, , 2014 is poorly known. There appear to be many hiatuses in between the plant assemblages documented up to now (Fig.…”

First Middle Devonian Bivalves from Argentina, New Records from the Punta Negra Formation and Insights on Middle Paleozoic Faunas from the Precordillera Basin

“…More recently, however, it has been interpreted as a shallow marine inner shelf to locally continental environment by Edwards et al (2009), as suggested by the taphonomy of plant remains.…”

The Middle Devonian plant assemblage from Dechra Aït Abdallah (Central Morocco) revisited

“…Its leaf bases, however, tend to be more hexagonal than those of the Moroccan specimen. The second specimen from Argentina, which is also 9 mm wide, was referred to as specimen LPPB 13267 by Edwards et al (2009) and illustrated in their Fig. 7c.…”

“…The leaf bases of this specimen do not show any obvious notch, a feature possibly specific to the Moroccan stems. Because leaf laminae were not preserved, Edwards et al (2009) did not assign their fossil to any taxon but simply inferred that it belonged to an herbaceous lycophyte with persistent leaf bases. The same approach is taken in this paper for the undetermined lycopsid from Dechra Aït Abdallah.…”