Middle Devonian microfloras and megafloras from western Argentina and southern Bolivia: their importance in the palaeobiogeographical and palaeoclimatic evolution of western Gondwana

The study of microfloras and megafloras from western Argentina and southern Bolivia presented here extends our knowledge of
the biodiversity and succession of floristic events during the Middle Devonian, and hence improves the current biostratigraphy.
Among floral remains, species attributable to ‘Haplostigma’ are mostly recorded from the same Grandispora pseudoreticulata and other palynomorph-bearing sections at Balapuca (southern Bolivia) and Del Chaco and La Cortadera creeks in the Precordillera
of Argentina. The northernmost record of Grandispora pseudoreticulata is recorded from a third palynoassemblage from the Pando x-1 corehole of northern Bolivia. A great similarity among all these
assemblages (notably abundant Grandispora pseudoreticulata) suggests the identification of terrestrial connections, or at least proximity, of these local areas and other regions in
South America during the Givetian. Comparison with other contemporary Gondwanan palynofloras shows cosmopolitan species (e.g.
Geminospora lemurata, Samarisporites triangulatus, Archaeozonotriletes variabilis, Chelinospora concinna) along with some others with more restricted distribution (e.g. Grandispora pseudoreticulata, Leiotriletes balapucensis, Acinosporites ledundae). This pattern defines an Afro-South American Subrealm, which most likely results from the effects of palaeolatitude and,
in a lesser way, local palaeoenvironmental conditions. On the other hand, such a level of cosmopolitanism supports previous
palaeogeographical reconstructions where a narrow Rheic Ocean was developed between Euramerica and the northern parts of Africa
and South America.

本研究对阿根廷西部和玻利维亚南部的微群落和巨群落进行了探讨，这不仅丰富了我们对志留纪中期生物多样性及植物群落演替过程的认识，同时也提升了当前的生物地层学。在植物残骸中，归属于‘Haplostigma’的物种主要记录于阿根廷前山地带的Balapuca（玻利维亚南部）的Grandispora pseudoreticulata及其他含孢粉化石的地层，以及阿根廷Del Chaco和La Cortadera溪流区域。Grandispora pseudoreticulata最北的记录来自玻利维亚北部的Pando x-1岩心第三层孢粉组合。这些组合（尤其是Grandispora pseudoreticulata的丰富性）之间的极大相似性表明，这些地区与南美洲的其他地区在吉维特期可能存在着陆地联系或至少是邻近关系。与其他同期冈瓦纳板块的孢粉植物群落进行比较，显示出全球性分布的物种（例如Geminospora lemurata、Samarisporites triangulatus、Archaeozonotriletes variabilis、Chelinospora concinna）以及一些分布较窄的物种（例如Grandispora pseudoreticulata、Leiotriletes balapucensis、Acinosporites ledundae）。这一模式定义了非洲-南美次区域，这很可能是古纬度和一定程度上的地方古环境条件的影响所致。另一方面，这种程度的全球性分布支持了之前的古地理重建，即欧亚美大陆与非洲和南美洲北部之间形成了狭窄的雷伊克海。