The upper Triassic fernphlebopteris smithii(daugherty) Arnold and its spores

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Abstract
Phlebopteris smithii (Daugherty) Arnold is a palmate fern leaf that appears to be monopodial, with an odd number (5 to 15) of spreading pinnatifid pinnae. The sori occur in a single row on either side of the pinnule midrib and presumably are not protected by indusia. Each sorus typically contains 14 to 20 sporangia which have oblique annulii. The spores are triangular in polar view with psilate walls and trilete laesurae with straight radii which extend almost to the equatorial margins. They most closely resemble the dispersed spores Diclyophyllidites harrisii which ranges from the Carnian Stage of the Late Triassic to the Bathonian Stage of the Middle Jurassic. Phlebopteris smithii is widely distributed in Upper Triassic to Lower Jurassic units of the United States and is particularly common in the Upper Triassic (middle Carnian) Chinle Formation in the Southwest. Dispersed spores similar to those produced by P. smithii occur also in the same units. P. smithii is one of the oldest representatives of the genus and demonstrates that most of the basic characteristics of the Matoniaceae were present by the middle of the Carnian Stage of the Late Triassic.

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