Abstract Detail

Paleobotanical Section

Taylor, Wilson [1].

Ultrastructure of Middle Devonian dispersed spores from New York, including Dibolisporites echinaceus, probably derived from Calamophyton bicephalum.

The Ashokan Formation of New York contains a rich assemblage of Middle Devonian spores. Based on a thorough consideration of hundreds of specimens, it was determined that many are assignable to Dibolisporites echinaceus (Eisenack) Richardson. Similar spores (Dibolisporites gibberosus var. major (Richardson)) were reported by Bonamo and Banks in situ from Calamophyton bicephalum from the Ashokan Formation, collected from nearby by Schultes (though the actual locality has been lost). Thus, this is the first report of the ultrastructure of spores that were probably produced by this plant. The spores range in diameter from 139-220µm (avg. = 177), lack proximal sculpture except for approx. 10% nearest the equator, and bear some kind of spines distally. When viewed with the TEM, wall thicknesses range from 4-9µm. This is well below the thicknesses reported by Bonamo and Banks, though their measurements were based solely on observation using the light microscope. The specimens have been compressed and most have little contrast despite staining. The outer half of the wall in nearly all specimens appears homogeneous. However, in a few informative specimens, laminated walls can be detected. In several cases, there is evidence for an inner separable layer, and associated laminae, like that seen in many extant lycophyte megaspores . However, there is no basis to suggest that Calamophyton was a lycophyte. Though the spores are near the widely used diameter cutoff for consideration as a megaspore (200µm), there is little evidence of extensive laminae, or sponginess that is so common among both fossil (coeval and younger) and extant megaspores. It is possible that Calamophyton did not possess the developmental mechanisms to construct spore walls capable of expanding to sizes well above 200µm as some other plants of a similar age did. Some researchers have argued that similarly sculptured spores extracted from Middle Devonian deposits in Poland that occupy a smaller size class may represent functional microspores, but no such spores in this size class were present in the Ashokan assemblage.

Broader Impacts:

1 - UNIVERSITY OF WISCONSIN - EAU CLAIRE, DEPT OF BIOLOGY-PHILLIPS HALL, 105 Garfield Avenue, P.O. Box 4004, EAU CLAIRE, WI, 54702-4004, USA

Keywords:
cladoxylopsid
spore ultrastructure
Devonian.

Presentation Type: Oral Paper:Papers for Sections
Session: 35
Location: Union A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 1:30 PM
Number: 35001
Abstract ID:206