Quercus sp.

Wheeler, Elisabeth A. & Manchester, Steven R., 2021, A Diverse Assemblage Of Late Eocene Woods From Oregon, Western Usa, Fossil Imprint 77 (2), pp. 299-329 : 310-312

Quercus sp. Red oak group

Text fig. 6a–g

M a t e r i a l. UF 279-24550.

D e s c r i p t i o n. Growth rings distinct. Ring-porous to semi-ring-porous.

Vessels exclusively solitary, latewood vessels in diagonal to radial alignment ( Text-fig. 6a, b ), round to occasionally oval in outline, mean tangential diameter of earlywood vessels 199 (28), 124–244 µm; perforations simple (Textfig. 6e); vessel-vasicentric pits alternate, rounded in outline ( Text-fig. 6d ), ~9–10 µm; vessel-ray parenchyma pits with reduced borders, horizontally to vertically elongate, variable ( Text-fig. 6e ); vessel element lengths 275–325 µm. Thinwalled tyloses present.

Imperforate tracheary elements include vasicentric tracheids ( Text-fig. 6d ), and non-septate fibers with thick walls.

Axial parenchyma apotracheal, relatively abundant, diffuse, diffuse-in-aggregates, and in 1-seriate lines (Textfig. 6a, b); strands of 4 cells.

Rays of two distinct sizes ( Text-fig. 6a, b, c ), uniseriate (rarely with biseriate portions) ( Text-fig. 6f ) and wide rays 38–62 cells wide, 0.49–1.1 mm; some wide rays with areas of cells of differing wall thicknesses and some with imperforate elements, probably beginning of ray dissection; homocellular, composed of procumbent cells ( Text-fig. 6g ); uniseriate rays 2–7–15 cells high; numerous 8–12–14 per mm.

Crystals occasional in chambered axial parenchyma strand, usually less than 4-chambers.

C o m p a r i s o n s w i t h e x t a n t w o o d s. This wood has features of the Castaneioideae (e.g., Wheeler et al. 2022): vessels exclusively solitary in radial/diagonal, vasicentric tracheids, vessel-ray parenchyma pits with reduced borders, homocellular rays of two distinct sizes, apotracheal parenchyma. Because the latewood vessels are rounded in outline, this wood is assigned to the Red Oak group, Quercus sect. Lobatae LOUDON ; latewood vessels in the White Oak group are angular in outline (e.g., Brazier and Franklin 1961, Panshin and DeZeeuw 1980). Distinguishing species in the Red Oak Group based on wood anatomy is not feasible, so we are only designating it as Quercus sp. Red Oak Group.

C o m p a r i s o n s w i t h o t h e r f o s s i l w o o d s. This ring-porous to semi-ring-porous wood differs from the Nut Beds Quercinium crystallifera R.A.SCOTT et E.A.WHEELER , which is diffuse to semi-ring-porous. Other differences are that UF 279-24550 has exceptionally wide rays, its rays are not typically aggregate, and crystals are not common. Reports of fossil oak woods are quite common in the literature, with different species reflecting differences in age and locality as much as differences in anatomy (e.g., Müller-Stoll and Mädel 1957, Suzuki and Ohba 1991).

C o - o c c u r r i n g f r u i t s. Manchester and McIntosh (2007) illustrated an oblate nut covered in whorls of scales and preserved as a silica cast lacking internal anatomy from locality UF 279 (figs 37–39) that was interpreted as representing an acorn of Quercus with the nut fully enclosed by the cupule.

Figures

Text-fig. 6. Quercus sp. Red Oak, UF 279-24550. a, b: Wood semi-ring-porous to diffuse-porous; vessels exclusively solitary; thinwalled tyloses in wide vessels; diffuse, diffuse-in-aggregates axial parenchyma; rays of two distinct sizes. TS. c: Rays of two distinct sizes, TLS. d: Vessel-vasicentric tracheid pitting, RLS. e: Vessel-ray parenchyma pitting with reduced borders, vertically elongate, RLS. f: Narrow rays 1-2 cells wide, TLS. g: Ray composed of procumbent cells, RLS. Scale bars: 200 µm in a, b, c; 50 µm in d, f, g; 20 µm in e.