Pecopteris

Pecopteris is an extinct genus of fossil fern (Filicophyta) from the Carboniferous and Permian found in León (Spain).

Definition and history

Pecopteris is a genus of form used for sterile foliage from the Carboniferous to the Permian. It was created by Brongniart (1822) as one of the 5 sections (subgenera) of the genus Filicites, a group in which Schlotheim had included all the fern-like fossil plants.

Zeiller, 1888 defines the genre as follows. “Fronds perhaps sometimes bipinnate, but more commonly tripinnate or quadripinnate or even quadrupinnate. Rachis of the different orders are kept naked between the homologous pinnae that accompany them, and that do not have in the space that separates these pinnae or minor pinnae or pinnules. Pinnules united along their entire base, emerging from the rachis at generally quite open angles, sometimes more or less welded together, with parallel or slightly converging edges, most often entire, sometimes lobed or toothed, with a generally rounded apex or obtuse, more rarely acute. Midrib distinct, reaching almost to the apex of the pinnules; secondary veins usually alternate, which emerge from the main vein at fairly open angles, either simple, or bifurcated once or several times” This author also supposed that at least some Pecopteris seemed to have belonged to trees whose fronds grew from the upper part of the trunks of considerable height.

Morphology

As it is a form genus, the different species of Pecopteris can be assigned to different families, therefore, the following descriptions are made taking into account the taxonomic assignment:

Fronds

The form genus Pecopteris is defined according to the morphology of the sterile fronds. Therefore, obviously, the morphological characters of the frond are the most important when determining the different species. The fronds of the Pecopteris consist of compound leaves, generally three or four times divided, with a petiole or rachis that bears inserted pinnae that divide successively until reaching the last elements, the pinnules. The main rachis is assigned the primary name. The secondary rachis of the also secondary pinnae depart from it. These bear tertiary rachis and pinnae, and so on. Because the normal thing when a fossil is located is that it is not known to which order the pinnules belong, it is common for them to be called last (or of order n), penultimate (or of order n-1) and so on.

Pennules

Along the frond there can be strong variation in the shape of the pinnules. On the one hand, there are the terminal pinnules, which are frequently a first-order taxonomic character but, unfortunately, cannot always be used for classification purposes due to the fragmentary nature of the specimens sampled. On the other hand, in some groups of Pecopteris such as Lobatopteris, Polymorphopteris, Remia or Oligocarpy The presence of lobed or pinnatifid pinnules is common, mainly in the terminal part of the primary pinnae.

Sporangia

Shortly after the establishment of the genus Pecopteris, fructifications associated with the leaves were found, confirming that most species were true ferns. Due to the poor or variable state of preservation of part of the material described, but also due to the different interpretation of the diagnostic significance of some features (for example the peduncles at the base of the synangia), they have been attributed to Pecopteris a large number of genera form fructifications. The use of modern paleobotanical techniques (particularly transfer processes) have allowed a reinterpretation of the validity of many of these genera. The following fructifications in compression fossils can currently be accepted.

• Family Zygopteridaceae

- Nemejcopteris Barthel

- Corynepteris Baily

• Family Psaroniaceae

- Remia Knight (=Weissites Remy non Goeppert)

- Asterotheca Presl

- Ptychocarpus Weiss

- Acitheca Schimper

- Danaeites Goeppert (=Orthotheca Corsin)

Family Psalixochlaenaceae

- Bertrandia Dalinval (=Zeilleria Kidston pars)

Family Sermayaceae

- Oligocarpy Goeppert

Family Tedeleaceae

- Senftenbergia Corda

Distribution and habitat

Brongniart described under this genre material from the Carboniferous to the Jurassic. The current habitual use of this genus of form is that of Paleozoic species. It is currently considered a species of the Upper Carboniferous to the Permian.

Although the oldest specimens come from the beginning of Pennsylvania, it became dominant during the Stephanian. The complete record of the Pecopteris spans approximately 40 million years. Based on the first occurrences and the global radiation pattern during the Stephanian, the geographic origin of the Marattiales appears to be tropical or Euro-American.

Pecopteris.