New Silurian cooksonias from dolostones of north-eastern North America

Abstract

New specimens of Cooksonia and Hostinella are described from the Bertie Group of Ontario and New York State, which is dated by faunas as latest Silurian (P ídolí). The rare plant fossils are unusual in that they are preserved in fine-grained, slightly argillaceous dolostones ('waterlime') rather than clastic rocks. At least two species of Cooksonia are present, one with ± globular sporangial morphology close to C. hemisphaerica Lang. Those with ellipsoidal/ discoidal sporangia are compared with C. pertoni Lang, C . paranensis Gerrienne et al . and C. bohemica Schweitzer, the latter represented by a single specimen from the P ídolí of the Czech Republic. However, the paucity of specimens, which prevents assessment of taphonomic influences on shape, combined with the absence of any anatomical features and the gross morphological simplicity of the fossils, precludes specific assignment. Specimens of Hostinella include one in which apices and a lateral basal structure resembling a root are preserved. It is concluded that the Laurentian assemblage of Ontario and New York State is less diverse and disparate than coeval assemblages, which are also preserved in marine rocks. Its preservation in limestones may have been facilitated by the hypersalinity inferred from various sedimentary features, which would restrict the activity of many decomposers.

Thalloid carbonaceous incrustations and the asynchronous evolution of embryophyte characters during the Early Paleozoic

“…In parts of the central Appalachians, there are small organic fragments scattered throughout the carbonatedominated sequences that lie between the Bloomsburg and the Bertie Waterlime, but these remain undocumented. None of the specimens of Cooksonia described by Banks (1973) or Edwards et al (2004) possesses convincing evidence of tracheids. However, several specimens of Cooksonia illustrated by Edwards et al (2004) clearly show coalified central strands.…”

“…None of the specimens of Cooksonia described by Banks (1973) or Edwards et al (2004) possesses convincing evidence of tracheids. However, several specimens of Cooksonia illustrated by Edwards et al (2004) clearly show coalified central strands. Tomescu et al (2009) have demonstrated that the carbon isotopic signatures of all of the Silurian thalloid compressions throughout the central Appalachian Basin are consistent with a terrestrial origin.…”

“…The sequence of Silurian plant remains from the central Appalachians has recently been reviewed by Beck and Strother (2008) who concluded that no bone fide tracheophytes of Silurian age have been found in the Appalachian Basin. The plant record ends in the Bertie Waterlime (Přídolí) which is the only Silurian deposit in eastern North America known to contain fertile material belonging to Cooksonia (Banks, 1973;Edwards et al, 2004). In parts of the central Appalachians, there are small organic fragments scattered throughout the carbonatedominated sequences that lie between the Bloomsburg and the Bertie Waterlime, but these remain undocumented.…”

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].…”

New trace fossil evidence for eurypterid swimming behaviour

“…Although OʼConnell's () early deltaic interpretation has since been widely contested, the presence of terrestrial plants ( Cooksonia ; Edwards et al . ) and early fish (Burrow & Rudkin ) in the Williamsville Formation A Member may be indication of a nearby fluviatile source and thus further evidence for reduced salinity levels.…”