Early seed plants from Western Gondwana: Paleobiogeographical and ecological implications based on Tournaisian (Lower Carboniferous) records from Argentina

Abstract

The oldest seed occurrences in Western Gondwana have been recognized in a new stratigraphic section located in Western Argentina (Precordillera Basin). Palynological evidence indicates an Early Mississippian (probably Tournaisian) age for this new succession. The two identified early seeds generas, Pseudosporogonites cf. hallei and Warsteinia sancheziae n. sp. were up to now considered as restricted to the Devonian of Laurussia. This finding suggests a dispersal of earliest spermatophytes between Laurussia and Gondwana during Devonian/ Tournaisian times, thus accounting for the Rheic Ocean as a surmountable biogeographic barrier for continental biotas. Alternatively, contrasting biogeographic hypotheses dealing with early spermatophytes rising in paleotropics and then displacing herbaceous communities of non-spermatophytes typical from cool high latitudinal regions, are explored for explaining the recognized paleobiogeographical pattern. The new information supports a weak impact of the Devonian/Carboniferous biotic crisis on earliest seed plant diversity. Based on preliminary evidences of niches differentiation and ecological dynamics probably affected by wildfires, Tournaisian Gondwanan plant communities from high latitudes are interpreted as being more complex than previously thought, and more similar to those reported from Laurussia. In addition, their discovery in a sedimentary environment associated to glacigenic deposits, show that this new record might be linked to the coeval glacial age widely recorded elsewhere in Gondwana.

Disrupted continental environments around the Devonian-Carboniferous Boundary: introduction of the tener event

“…The available information for other plant taxa such as ferns (e.g. Zygopteridales, Cladoxylales, Stauropteridales) and lycophytes indicate similar continuous diversification Prestianni et al, 2015).…”

“…Timing of the events on lands still needs to be clarified and a revised palynological scheme of this critical interval is unavoidable. Moreover, recent data on plants (Decombeix et al, 2011a, b;Cascales-Miñana, 2014;Prestianni et al, 2015) tend to show that the traditional view of what happened on land at the DCB is incorrect.…”

Palynostratigraphy of the Zorritas Formation, Antofagasta region, Chile: Insights on the Devonian/Carboniferous boundary in western Gondwana

“…This association contains Waltzispora lanzonii (samples 7048 and 7050) cronostratigraphically constrained to the Tournaisian (AL to the PD interval zones) and palaegeographically restricted to north-northwestern Gondwana, with records in Brazil, Peru, Argentina, Algeria and Libya Melo, 2010, 2012;Prestianni et al, 2015). Its uncommon records in Visean strata have been considered to be probably reworked and references therein).…”

The Devonian-Carboniferous Boundary around the globe: a complement

“…In the lower part of the unit, Lower Devonian trilobites are documented (e.g. Holloway and Rustán 2012), but no stratigraphic data are available above until the diamictite levels, interpreted as Late Devonian Glacial Event (see discussion in Prestianni et al 2015). In a section located in the southern part of the Sierra de Las Minitas, Prestianni et al (2015) documented the miospore Waltzispora lanzonii from horizons located about 35 m above the diamictites in a palynological association mainly composed of Devonian taxa.…”

“…Holloway and Rustán 2012), but no stratigraphic data are available above until the diamictite levels, interpreted as Late Devonian Glacial Event (see discussion in Prestianni et al 2015). In a section located in the southern part of the Sierra de Las Minitas, Prestianni et al (2015) documented the miospore Waltzispora lanzonii from horizons located about 35 m above the diamictites in a palynological association mainly composed of Devonian taxa. However, W. lanzonii is documented only from the Tournaisian of northnorthwestern Gondwana, and therefore the Devonian taxa should be considered reworked by glacial erosion (Prestianni et al 2015).…”