Abstract Detail

Paleobotany

Richmond, Dean [1], Lupia, Richard [2], Philippe, Marc [3].

The northernmost Jurassic occurrences of Cupressinoxylon from the Morrison Formation of central Montana.

Cupressinoxylon is recognized as an integral part of the North American high latitude paleoforests of the Cretaceous Period. Some of the boreal wood genera associated with Cupressinoxylon during the Cretaceous include Xenoxylon, Piceoxylon, and Circoporoxylon (Harland et al., 2007). These same genera have recently been reported from the Upper Jurassic Morrison Formation of central Montana (Richmond et al., 2019a, b, c). The first Jurassic occurrence from North America could be a specimen identified by Knowlton from the Jurassic Knoxville Formation of California (Turner, 1891). However, this specimen has not been validated. The first recognized occurrence of the genus is from the Morrison Formation of South Dakota (Lutz, 1930). Recently Cupressinoxylon was reported from the same formation of the western Oklahoma panhandle (Richmond et al., 2018). Three tracheidoxyls were newly discovered in the Morrison Formation of central Montana.
The lowest stratigraphic specimen, PW TFA4, was found 46 meters above the underlying Swift Formation. Specimen PW 33 is associated with a Morrison-aged carbonate mound spring tufa deposit at 48 meters. The highest stratigraphic tracheidoxyl is CS PW1 at 53 meters. Measurements of only the tracheidoxyl PW TFA4 are described herein.
Earlywood tracheid cells are round or polygonal. Earlywood tracheids have an average perimeter of 112 μm with an average cell area of 940 μm². Latewood tracheid cells have an average perimeter of 64 μm with an average area of 261 μm². The reduction of latewood cell area is 72%. Cupressinoxylon has a gradual transition from earlywood to latewood incorporating 5-7 cells (Type E; Brison et al., 2001). Axial parenchyma cells are present in varying amounts and are resiniferous.
Medullary rays can be heterocellular. The rays are predominantly uniseriate and are often partially biseriate, but never triseriate. Ray heights average 246 μm. In a random 100-ray count, the number of cells per ray varies from 2-29 with a median cell count of 9. The average ray cell vertical diameter is 25 μm. No tangential bordered pits were observed.
Bordered pits in the radial section are rounded, uniseriate, and distant. The median height/width (h/w) ratio is 0.82. The distance between bordered pits is variable, ranging from 0-128 μm with an average distance of 13 μm. In specimen PW TFA4, bordered pits are occasionally biseriate with both opposite and alternate arrangements. Biseriate bordered pits were not observed in the other referenced specimens. Crossfield pitting consists of 1-2 cupressoid pits per crossfield.

1 - University Of Oklahoma, 100 E. Boyd St., Sarkeys Energy Center Suite 710, Norman, OK, 73007, United States
2 - UNIVERSITY OF OKLAHOMA, Sam Noble Museum, 2401 Chautauqua Avenue, Norman, OK, 73072, United States
3 - University Lyon, 1 CNRS, UMR 5023, Villeurbanne, Lehna, F-69622, France

Keywords:
Upper Jurassic Cupressinoxylon.

Presentation Type: Poster
Session: P3, Paleobotany Posters
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: P3PB002
Abstract ID:96
Candidate for Awards:None