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Abstract Detail


Paleobotanical Section

Caruso, Joseph A. [1], Barrett-Watson, Hanna [1], Tomescu, Alexandru [1].

New gametophytes from the Early Devonian Beartooth Butte Formation (Wyoming).

The Beartooth Butte Formation hosts the only extensive Early Devonian plant assemblages in western North America and has recently yielded fossils reminiscent of thalloid bryophyte gametophytes. The fossils are <10 mm and fall within three morphological types. Type1 includes radially symmetrical thalli with 4-6 branches diverging from a central point. Branches are 0.8-1.5 mm wide at the base, up to 3 mm long, sometimes with two orders of branching, and rounded or bilobed tips. Type 2 consists of bilaterally symmetrical thalli. Branches fan out from a central area in two directions, forming a "butterfly shape". Each of the two fans, consisting of 5-6 branches, widens to almost 180°, with the outermost branches recurved and overlapping corresponding branches of the opposite fan. Branches are 0.6-1.3 mm wide at the base, up to 3.3 mm long, sometimes with two orders of branching and rounded tips. Type 3 thalli are smaller (up to 6 mm) and exhibit bilateral symmetry. Two branches, 1.5-2.2 mm wide at the base and up to 2.2 mm long with lobed tips, diverge in each of the two directions of growth. The absence of fertile structures makes it difficult to resolve the taxonomic affities of these gametophytes. Type 1 thalli resemble Ricciellopsis and Ricciopsis from the Middle Devonian of Podolia and theTriassic-Jurassic of Iran and Sweden, but are different from these in some characteristics. Type 3 thalli resemble Marchantites fossils from the Cretaceous of Spain, but type 2 thalli are not comparable to any known fossil gametophyte. Some extant Ricciaceae are reminiscent of type 1 gametophytes in their radial symmetry and diminutive sizes, but the pronounced bilateral symmetry seen in type 2 and type 3 gametophytes has no counterpart among extant bryophytes. Palynostratigraphy indicates a late Lochkovian - early Praghian (ca. 410 Ma) age for the Wyoming gametophytes, therefore they are slightly older than the early vascular plant gametophytes of the Rhynie chert and German Schiefergebirge.

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1 - Humboldt State University, Department of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

Keywords:
gametophyte
fossil
bryophyte
Devonian
Wyoming.

Presentation Type: Oral Paper:Papers for Sections
Session: 06
Location: Lindell C/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 9:15 AM
Number: 06003
Abstract ID:232


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