Perissothallus, a new genus for Late Pennsylvanian–Early Permian noncalcareous algae conventionally assigned to Schizopteris (aphleboid foliage)

Abstract

The morphogenus Schizopteris was established in the early 19th century for late Palaeozoic aphleboid foliage of uncertain affinities, and numerous specimens have subsequently been assigned to this taxon. Some of these fossils do not represent foliage, but rather noncalcareous algae. Although this inconsistency has been noted, an attempt to exclude the algae from Schizopteris has not yet been undertaken. Here we propose the new genus Perissothallus to accommodate those fossils conventionally assigned to Schizopteris that represent algae. The name P. versiformis is introduced for the type species from the Upper Pennsylvanian of Kansas (USA). Specimens from the Lower Permian of Germany are interpreted as a second species of Perissothallus , and the name P. densus is proposed. Perissothallus consists of erect cylindrical branches that radiate from a small holdfast and dichotomize repeatedly. Vegetative reproduction occurs in the form of daughter thalli produced on prostrate branches. Similarities in basic structure exist between Perissothallus and members of the extant algal genera Codium (Chlorophyta), Dictyota (Phaeophyta), and Scinaia (Rhodophyta).

First record of the noncalcareous macroalga Perissothallus from shallow-water deposits (Pennsylvanian) in the Kladno-Rakovník Basin, Czech Republic

“…Perissothallus versiformis from the Upper Pennsylvanian of North America and P. densus from the Lower Permian of Germany (Krings et al 2007). Krings et al (2007) used three basic features to distinguish algae from Schizopteris-type aphleboid foliage.…”

“…Barthel (1982), Kerp & Fichter (1985), and Krings et al (2007) suggested that some of the fossils conventionally assigned to Schizopteris do not represent aphleboid foliage, but rather thalli of noncalcareous algae similar in overall morphology to certain extant members of the Chlorophyta (green algae), Phaeophyceae (brown algae), and Rhodophyta (red algae). Krings et al (2007) Krings et al from the Lower Permian of Germany.…”

“…Barthel (1982), Kerp & Fichter (1985), and Krings et al (2007) suggested that some of the fossils conventionally assigned to Schizopteris do not represent aphleboid foliage, but rather thalli of noncalcareous algae similar in overall morphology to certain extant members of the Chlorophyta (green algae), Phaeophyceae (brown algae), and Rhodophyta (red algae). Krings et al (2007) Krings et al from the Lower Permian of Germany. However, these authors acknowledged that many more specimens and forms need to be critically analyzed and formally described to complete the separation of the algae from Schizopteris, and to document the geographic distribution and stratigraphic range of these aquatic plants.…”

“…Unfortunately, noncalcareous macroalgae become preserved only where the depositional environment provides ideal conditions for fossilization. Moreover, impression/compression fossils of these organisms may easily be confused with other plant remains such as bryophytes, aphleboid foliage of several vascular plants, and roots, and thus are probably often overlooked or misinterpreted (Krings et al 2007).…”

“…Conversely, noncalcareous macroalgae are rare as fossils. The fossil representatives reported to date for this group likely represent only an infinitesimal portion of the species diversity that existed in various aquatic environments throughout geological time (Krings & Mayr 2004, Krings & Butzmann 2005. Nevertheless, noncalcareous macroalgae play important roles in the functioning of many aquatic ecosystems today (e.g., Round 1981), and likely were similarly important in the past.…”