Hickey, L. J. .
A New Genus and Species of Conifer Wood from the Late Triassic of Connecticut.
Silicified wood is a rare but locally distributed component of the Early Mesozoic sediments of the Newark Supergroup from North Carolina to Pennsylvania. However, it is almost unknown from the northward extension of this unit into New England, with the exception of a locality in the town of Southbury, Connecticut, which has been known since early in the Nineteenth Century. This site lies on the Late Triassic South Britain Formation on the southwestern margin of the Pomperaug Basin, a western outlier of the Hartford Basin. We report on a new occurrence of wood from this locality, found as a single trunk specimen, 0.5 m in diameter. The wood is pycnoxylic and consists of tracheids with mostly uniseriate to occasionally alternate-biseriate, protopinaceous pits and uniseriate rays ranging from 1 to 11 cells high. The tracheids are septate and possess highly characteristic robust spiral-thickenings. The rays consist entirely of parenchyma, have thin walls, are frequently filled with an opaque deposit inferred to represent resin, and have from 1 to 2 cupressoid cross-field pits where they cross a tracheid. The characters of the Southbury wood place it closest to the Mesozoic fossil genera Spiroxylon and Platyspiroxylon, which are unique in having robust spiral thickenings in their tracheids, except that these genera also have araucarian, rather than protopinaceous tracheid pitting. Pseudohiermirella delawarensis Axsmith, from the Late Triassic of the Newark Basin, is a less good match, especially in its lack of spiral thickenings. Overall the Southbury wood appears to lie closest to the conifer families Cheirolepidiaceae and possibly to the Cupressaceae, except that no member of either family has its highly characteristic robust spiral thickenings. It thus probably represents a member of an Early Mesozoic stem-taxon of the conifers.
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1 - Yale University, Department of Geology & Geophysics, Yale Station, P.O. Box 208109, New Haven, Connecticut, 06520-8109, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 555A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 8:30 AM