Plant assemblages from the Silurian of southern Bolivia and their palaeogeographic significance

Abstract

Abundant but fragmentary plant fossils are described from two locations in shallow water marine facies of the Lipeón (previously Kirusilla) Formation of southern Bolivia. Field relationships and limited palaeontological data suggest that the rocks are of Ludlow to possibly early P'ídolí age (i.e. late Silurian). The majority of the fossils are sterile coalified compressions or impressions of parallel‐sided axes, some with branching typical of Hostinella. No tracheids have been found and such remains are best described as rhyniophytoid. Fragments with irregular branching and variable axial diameters probably belong to algae with some similarities to Hungerfordia and Buthotrephis. Rarely axes terminate in clearly delimited globular or elliptical swellings that are interpreted as sporangia, although no spores have been recorded. The most completely preserved specimens have dichotomous branching ending in predominantly elliptical sporangia with distal borders and closely resemble Cooksonia ca‐ledonica. Solitary isolated sporangia are vertically elliptical (cf. Tarrantia), globose (cf. C. cambrensis, C. hemi‐sphaerica) or laterally extended (cf. C. pertoni). Those with cup‐ or funnel‐shaped morphologies superficially resemble the rhyniophytoid Steganotheca or dyad‐containing Culullitheca. Thus while it is impossible to compare with confidence the taxonomic composition of Bolivian assemblages with coeval ones, their overall morphological grade is closer to material collected from circum‐northern Atlantic localities than from assemblages in Australia and Kazakhsta/nChina. Palaeogeographically this translates into floristic similarities between Gondwanan high latitudes and equatorial Laurussia rather than with low latitude, north‐eastern Gondwana or with a low latitude Kazakhstan/ Xinjiang micro‐palaeocontinent

A timeline for terrestrialization: consequences for the carbon cycle in the Palaeozoic

“…Other Silurian (Přidolí Series) evidence includes records from Kazakhstan, Podolia [11] and possibly China [27]. Further corroborating evidence comes from early records of Cooksonia that are probably also within the Lycophytina total group, including several species from the Silurian (Přidolí Series): Cooksonia caledonica (Bolivia, Britain), Cooksonia bohemica (Czech Republic) and Cooksonia cambrensis (Britain) [20,28]. The earliest evidence of the Euphyllophytina total group is Wutubulaka multidichotoma from the Late Silurian (Přidolí Series) of Xinjiang, China [27].…”

“…The oldest generally accepted record of a land plant body fossil is Cooksonia from the Silurian (Wenlock Series, Homerian Stage) of Ireland [19] (figure 2n,t). Other records of Cooksonia and Cooksonia-like plants are widespread through the Ludlow and Přidolí Series of Euramerica, Kazakhstan, China and Gondwana [10,20]. Phylogenetic analyses indicate that Cooksonia is paraphyletic or possibly polyphyletic [21], and the genus has recently been redefined based on a more restrictive set of apomorphic features [22].…”

Dynamics of Silurian Plants as Response to Climate Changes

“…Cooksonia hemisphaerica, cf. Tarrantia and isolated sporangia [93] (Figure 3-L6). One of the best-preserved specimens of cf.…”

Middle Devonian lycopsids from high southern palaeolatitudes of Gondwana (Argentina)

“…This includes descriptions from Venezuela (e.g. Berry & Stein, 2000;Berry, 2000;Berry & Edwards, 1996;Edwards & Benedetto, 1985), Colombia , Brazil (Gerrienne, 1999;Gerrienne et al 2001) and Bolivia (Edwards et al 2001a). In Argentina, the presence of Devonian plants has previously been recorded by Halle (1936), Frenguelli (1951Frenguelli ( , 1952, Menendez (1967), Archangelsky (1983), Morel et al (1993), Gutierrez (1996), Gutierrez & Archangelsky (1997) and Edwards et al (2001b), although frequently age and accurate determination of the fossils is debated.…”