Otzinachsonia beerboweri
(arborescent cormose lycopsid)

barinophyton fossilReconstructions of three isotealean lycopsids, Clevandodendron (left), Chaloneria (middle) and Pleuromeia (right) ©

Arborescent (tree-like) lycopsid fossils were abundant in the floodplain pond facies at Red Hill. Most of these were poorly preserved decorticated stem fragments (i.e., they lack the surface features used to distinguish lycopsid taxa. However, several well-preserved specimens consisting of rhizomorphs (rooting organs) and lower stems were also found. They belong to a new species of isotealean lycopsid, Otzinachsonia beerboweri.

The rhizomorph of Otzinachsonia consist of a cormose (swollen) four-lobed base with masses of attached rootlets. The stems exhibited a spiral arrangement of elliptical leaf scars without leaf cushions. Unfortunately, the upper portion of Otzinachsonia is unknown, but it's plausible that it consisted of a single, unbranched stem. Only two of the hundreds of decorticated stem fragments found at Red Hill were branched; unbranched arborescent lycopsids are also known from the Late Devonian (Clevelandodendron), Late Carboniferous (Chaloneria) and Triassic (Pleuromeia). Assuming an unbranched growth habit, extrapolation from the taper and maximum stem width (7cm) indicate that Otzinachsonia reached a height of 120 cm.

At least two size classes of Otzinachsonia are evident. The maximum base widths of the two smaller specimens are 2.5-3.5 cm whereas the those of the three larger specimens range from 8.1-10.3 cm. Despite the differences in sizes, their proportions were very similar, which suggests that this lycopsid experienced secondary growth in both its cormose base and aerial stem. The presence of delicate rootlets, multiple size classes and preservational setting indicate that Otzinachsonia lived in multi-aged stands along the margin of the floodplain pond at Red Hill.

cormose lycopsid fossil Fossil slab showing two specimens of Otzinachsonia beerboweri. Two of the rhizomorph lobes and numerous rootlets of the larger specimen (ANSP 4512) are visible at the lower left of the slab. The other specimen (ANSP 4518) is partially obscurred by the rule. Photo courtesy of Walt Cressler.

The vast majority of decorticated lycopsid stem fragments collected at Red Hill are unidentifiable, but a couple of specimens compare favorably (c.f.) with Lepidodendropsis. You can also find out more about lycopsids.

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Scientific Papers:
Chitaley, S. and K.B. Pigg. 1996. "Clevlandodendron ohioensis, gen et. sp. nov., a slender upright lycopsid from the Late Devonian Cleveland Shale of Ohio." Amer. J. Botany 83(6): 781-789.
Cressler, W.L., 1999. "Site–analysis and floristics of the Late Devonian Red Hill locality, Pennsylvania, an Archaeopteris-dominated plant community and early tetrapod site." Unpublished Ph.D. Dissertation, Univ. Pennyslvania, Philadelphia, 156 p.
Cressler, W.L. III and H.W. Pfefferkorn. 2005. "A Late Devonian isoetalean lybopsid, Otzinachsonia beerboweri, gen. et sp. nov., from north-central Pennsylvania, USA." American Journal of Botany 92(7): 1131-1140.
Hirmer, M. 1933. "Rekonstruktion von Pleuromeia sternbergi Corda, nebst bemer Kungen zur Morpholodie der Lycopodiales." Palaeontographica B. 78: 47-56.
Pigg, K.B. and G.W. Rothwell. 1983. "Chaloneria gen.nov.; heterosporous lycophytes from the Pennsylvanian of North America." Botanical Gazette 144: 132-147.
Image Credits:
All images are copyrighted © 2002, Dennis C. Murphy. (See Terms of Use.) The reconstructions were based on Chitaley and Pigg (1996), Hirmer (1933), Jennings (1972) and Pigg & Rothwell (1983).

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