RESUMO
The Silurian-Devonian transition played a crucial role in the development of early terrestrial ecosystems due to the rapid diversification of early vascular plants. However, records of Pridolian plants in western Gondwana are scarce, limited to outcrops located in southern Bolivia. In this contribution, an association of fossil plants housed in the Rinconada Formation is presented. This association corresponds to primitive fossil flora with reproductive structures and sterile axes linked to basal tracheophytes. The fossil assemblage is composed of Aberlemnia caledonica, Caia langii Cooksonia cf. cambrensis, C. paranensis, C. cf. pertoni, Hostinella sp, Cf. Isidrophyton sp, Salopella marcensis, Steganoteca striata, two morphotypes of doubtful taxonomy, and graptolites colonies. The association between flora remains and graptolites, represents a parautochthonous assemblage in an inner marine platform, dominated by gravity flows. This record has paleophytogeographic importance indicating the extension of the northwest Gondwana-southern Laurusia unit to more southern areas of Gondwana. This expansion would have been favored by the post-glacial climatic improvement of the Late Silurian, together with a great radiation capacity and environmental flexibility of the flora. Furthermore, the biochron is extended of three taxa (A. caledonica, C. paranensis and Cf. Isidrophyton sp) first known from the Lochkovian, to the Pridoli.
Assuntos
Fósseis , Fósseis/anatomia & histologia , Embriófitas/classificação , Embriófitas/anatomia & histologia , Ecossistema , Bolívia , Evolução Biológica , PaleontologiaRESUMO
Clam shrimps are a group of freshwater crustaceans who prospered during the Late Triassic. They were abundant in lacustrine sedimentary records of continental basins distributed throughout Pangea during this time. However, they show significant taxonomic differences between the clamp shrimp faunas from the rift basins of central Pangea and the southern Gondwanan basins. In this contribution, we show new fossil clam shrimp assemblages from the lacustrine sedimentary successions of the Eastern Cordillera of Colombia (the Bocas and Montebel formations), providing information on the Late Triassic species that inhabited the northwestern Gondwana basins. This study demonstrates that the basins of northwestern Gondwana shared Norian clamp shrimp species with rift basins of central Pangea and differed in their faunas with the basins of the southern portion of Gondwana. In addition, the Late Triassic clam shrimps paleobiogeographic distribution reflects the dispersal of this fauna throughout fluvial-lacustrine environments established in the rift valleys along the central Pangea. Therefore, the rift valleys produced during the early fragmentation of central Pangea could have acted as corridors for dispersion. Simultaneously, rift valleys also provided paleobiogeographic barriers that isolated the central Pangea clam shrimp faunas from southern Gondwana.