217-9 FIRST BAIERA-DOMINATED LEAF MATS IN THE MORRISON FORMATION (UPPER JURASSIC), CENTRAL MONTANA

Session: Paleontology, Paleoecology/Taphonomy

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Authors:

Abstract:

Although the Morrison Formation is well known for its dinosaur and other vertebrate faunas, it has a significant flora as well. Among the known megafossil local floras of the Morrison Formation, few are dominated in diversity or abundance by ginkgophytes. The Montezuma Creek site in southeastern Utah is dominated in abundance by the ginkgophyte Czekanowskia. Only the Jurassic Salad Bar site, also in southeastern Utah, is dominated in numbers and diversity by ginkgophytes. At these two sites, Czekanowskia turneri often occurs in nearly-monotaxic leaf mats almost completely covered in this ginkgophyte’s leaves, possibly shed seasonally and indicating deciduousness in the species. The ginkgophyte Baiera was first reported from the Morrison Formation at Temple Canyon, Colorado, in 2008. Here, we report the first occurrence of nearly-monotaxic leaf mats of Baiera in the Morrison Formation, at a site in central Montana. At this new site, Baiera dominates most bedding planes and covers most of their surfaces with leaves and fragments. Accompanying flora appears to include conifers and cycadophytes, possibly Ginkgo, and the ferns Cladophlebis heterophylla, Cl. virginiensis, Cl. alberta, and Coniopteris sp. This ginkgophyte occurrence is also the first of Baiera in the Morrison Formation north of Colorado. The Baiera leaf mats indicate that this possibly deciduous ginkgophyte, not previously known from Montana Morrison Formation sites such as Belt, could also numerically dominate some sites, as Czekanowskia does at Montezuma Creek and Jurassic Salad Bar in southern Utah.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11047

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