Rotafolia songziensis

Rotafolia songziensis is a species of the extinct Sphenophyllales horsetails.[1]

Rotafolia songziensis
Temporal range: Upper Devonian
Scientific classification
Kingdom:
Plantae
Division:
Pteridophyta
Class:
Equisetopsida
Order:
†Sphenophyllales
Genus:
†Rotafolia
Species:
R. songziensis
Binomial name
†Rotafolia songziensis

Description

This plant is similar to Hamatophyton verticillatum and is found in the Xiejingsi Formation. R. songziensis consists of branched axes, up to 20 cm long, which have slightly swollen nodes and internodes with ribs and narrow branches produced from the nodes. The axes are protostelic. Cross sections show a roughly triangular or quadrangular organization of the primary xylem and radial arrangement of the secondary xylem. Primary xylem is exarch upon maturation, with protoxylem strands positioned around the tips of the primary xylem arms. No differentiation between fascicular and interfascicular regions of the secondary xylem is apparent, and ray cells are rarely observed. Protoxylem tracheids have helical wall thickenings, whereas the tracheids of meta- and secondary xylem possess scalariform and/or bordered pits. All R. songziensis axes bear trichomes or spines, some up to 2.8 mm long. At the nodes are whorls of six leaves, up to 2.4 cm long, that regularly or irregularly fork two to four times. The leaves are positioned perpendicular to the axis in proximal portions of the plant but inserted at acute angles in distal portions. Fertile branches are produced in a terminal strobilus (8.5 cm long), which is subtended by whorls of normally developed leaves. It consists of a central axis and up to 16 whorls of fertile units, each of which consists of a bract and 6-10 sporangia. The bracts are elongate-cuneate and have prominent marginal fringes; sporangia are attached to the abaxial surface at the base of each brac. Although R. songziensis closely resembles H. verticillatum with its external axis morphology, leaf shape, and structure of the primary xylem. However, the two forms differ in strobilus morphology.

gollark: There was also somewhat less carbohydratey stuff (bread/pasta) available for a bit, as far as I could tell.
gollark: (although marmite rice cakes seem to be missing now?)
gollark: People were complaining about supply chain disruption and how clearly everywhere needs to be self-sufficient during the start of the whole people-noticing-COVID-19 thing, but it seems like, on the whole, there was mostly food and stuff around and it got resolved fairly fast.
gollark: Stuff does manage to mostly function, most of the time, somehow.
gollark: I kind of want to read Worm, or at least some of it, to actually understand what half of this is about.

References
  1. Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, ISBN 978-0-12-373972-8 , p. 333
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