Abstract Detail

Paleobotanical Section

Iannuzzi, Roberto [2], Pfefferkorn, Hermann [1].

Paulophyton and Kegelidium, fertile structures from the Poti Formation (Early Carboniferous, northeastern Brazil).

Plant fossils from the Poti Formation in Piaui State of northeastern Brazil (Parnaiba Basin) include mostly pteridosperm foliage, reproductive organs associated with them, but also rare lycopsids and sphenopsids. Recently, the Poti Formation has been dated as Late Visean based on palynology and macrofloral data. Two of the fertile structures have been reinvestigated and yield new information about these Late Mississippian plants from Gondwana. Paulophyton has the appearance of an Early or Middle Devonian plant but is found in the Carboniferous. It is a rare but apparently widespread plant known from several localities in South America and one in Europe. The plant consists of finely dissected axes that do not have a lamina. The small size and terminal arrangement of sporangia in Paulophyton is reminiscent of some Rhyniophytes. Nevertheless, Paulophyton is a more advanced plant exhibiting a regular dichotomous to pseudomonopodial branching system with a strong principal axis in its lower parts. Kegelidium consists of microsporangiate fructification displaying terminal cluster of non-synangiate microsporangia on a three-dimensional, dichotomous branch system composed of leafless axes. Terminal axes bearing groups of four un-fused, and erect elongated sporangia. Two pairs of sporangia are radially arranged per ultimate divisions, each fertile terminal axis bearing between 8 to 32 sporangia. No dehiscence mechanism is visible. Kegelidium shows a close morphological similarity with early seed-ferns of Lower Carboniferous age related to Lyginopteridaceae. Kegelidium and Obandotheca, from the Late Mississippian of Peru, appear to be an intermediate evolutionary step between non-synangiate forms such as Zimmermannitheca, and advanced synangiate ones as Telangiopsis and Telangium. The presence of Kegelidium and Obandotheca in the Southern Hemisphere shows the diversity and wide-spread occurrence of pteridosperms of lyginopterid affinity in the Late Mississppian.

1 - University of Pennsylvania, Department of Earth and Environmental Sciences, Philadelphia, Pennsylvania, 19104, USA
2 - Universidade Federal do Rio Grande do Sul, Departamento de Paleontologia e Estratigrafia, Instituto de Geociencias, Av. Bento Goncalves 9500, Porto Alegre, RS, 91.509-900, BRAZIL

Keywords:
Paulophyton
Kegelidium
Visean
Mississippian
Poti Formation
Brazil
Parnaiba Basin.

Presentation Type: Paper
Session: 5-7
Location: Maybird (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 10:00 AM
Abstract ID:733