Lithocarpoxylon ashwillii, Wheeler & Manchester, 2021

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 : 308-310

Lithocarpoxylon ashwillii sp. nov.

Text-fig. 5a–g

H o l o t y p e. Designated here. UF 279-24559 (Textfig. 5a–g).

P l a n t F o s s i l N a m e s R e g i s t r y N u m b e r.

PFN 002680 (for new species).

R e p o s i t o r y. Paleobotany Collections , Florida Museum of Natural History , Gainesville, Florida, USA .

T y p e l o c a l i t y. UF 279. About 3 km east of Post,

Crook County, Oregon, USA.

T y p e s t r a t u m a n d a g e. John Day Formation,

Eocene.

E t y m o l o g y. Named for Melvin Ashwill, who alerted

S. R. Manchester to these woods.

D i a g n o s i s. Growth rings distinct. Semi-ring-porous to diffuse-porous. Exclusively solitary vessels in a diagonal to radial arrangement. Simple perforation plates. Vesselray parenchyma pits with reduced borders, often vertically elongate. Vasicentric tracheids present. Axial parenchyma diffuse, diffuse-in-aggregates and in uniseriate lines. Nonseptate fibers. Uniseriate rays and aggregate rays composed of loosely associated narrow rays.

D e s c r i p t i o n. Minimum estimated diameter of 30 cm.

Growth rings distinct. Semi-ring-porous.

Vessels in diagonal to radial alignment; exclusively solitary, round to oval in outline ( Text-fig. 5a, b ), mean tangential diameter of the earlywood vessels (first three rows) 208 (28)–215 (39) µm, 160–260 µm. Simple perforation plates ( Text-fig. 5c, d ), end walls of vessel elements usually horizontal ( Text-fig. 5g ). Vessel-ray parenchyma pits with reduced borders and commonly vertically elongated (Textfig. 5d). Thin-walled tyloses common in wider vessels.

Non-septate fibers of medium wall thickness. Some with small (ca. 3 µm) bordered pits on radial walls. Vasicentric tracheids present ( Text-fig. 5c, g ).

Axial parenchyma apotracheal diffuse, diffuse-inaggregates, and in 1-seriate lines ( Text-fig. 5a, b ), 4–8 cells per strand.

Rays uniseriate ( Text-fig. 5f, g ), homocellular composed of procumbent cells and heterocellular with some square and upright cells; upright and square cells more common in region of vessels. Some loosely aggregate rays composed of 1–2(–3)-seriate rays ( Text-fig. 5f ). Rays 2–15–47 cells high; uniseriate rays 12–15–18/mm.

Solitary prismatic crystals occasional in chambered axial parenchyma, 1 crystal per chamber, number of chambers 2–10 ( Text-fig. 5e ).

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. The affinities of this wood are clearly with the Fagaceae because of the combination of semi-ring-porosity (4p), exclusively solitary vessels that are in a radial to diagonal arrangement (7p 9p), vertical vessel-ray parenchyma pits with reduced borders (32p), vasicentric tracheids (60p), and aggregate rays (101p).

Aggregate rays are rare in this fossil and comprised of loosely associated narrow ray s, similar to rays of Notholithocarpus densiflorus (HOOK. et ARN.) MANOS, CANNON et S.H.OH (synonym: Lithocarpus densiflorus (HOOK. et ARN.) REHDER ) (BWCw 8593). Images in InsideWood, the on-line FFPRI Database of Japanese Woods ( Wood Identification Database Team, FFPRI accessed 2020–2021), and wood anatomical atlases ( Ilic 1991, Ogata et al. 2008) indicate that aggregate rays in the evergreen oaks and Lithocarpus BLUME species are more common and composed of considerably wider individual rays. Two samples of Castanopsis (D.DON) SPACH (TWTw 22503, TWTw 15003) have aggregate rays composed of 1–3-seriate rays, but they were more closely associated than in this fossil. It is tempting to consider that this fossil might have affinities with Notholithocarpus MANOS, CANNON et S.H.OH , a western North America endemic, found to be more closely related to Castanopsis than to Lithocarpus ( Manos et al. 2008) . However, we only saw a small sampling of the hundreds of extant species of evergreen oaks, Castanopsis , and Lithocarpus , so we cannot be certain of that relationship.

C o m p a r i s o n s w i t h f o s s i l w o o d s. In their useful overview of Quercus L. and Quercus- like fossil woods, Suzuki and Ohba (1991) emended the diagnosis of Lithocarpoxylon ( Petrescu 1978) and indicated that this name should be applied to fagaceous woods that are diffuse to semi-ring-porous, with radially arranged pores, and aggregate rays. They noted that this combination occurred not only in Lithocarpus , but in evergreen species of Quercus and tropical species of Castanopsis . We are following Suzuki and Ohba’s recommendation and assigning this Post Hammer wood to Lithocarpoxylon . To the best of our knowledge, no other Lithocarpoxylon has aggregate rays composed of such loosely associated 1–2-seriate rays, so we designate it a new species. Selmeier and Velitzelos (2000) described evergreen oak types; transverse sections of two of their samples (15 and 20) suggest the possibility of similar aggregate rays, but, unfortunately, there were no tangential sections provided for verification.

Figures

Text-fig. 5. Lithocarpoxylon ashwillii sp. nov., UF 279-24544. a, b: Semi-ring porous wood, exclusively solitary vessels in a radial/ diagonal arrangement, diffuse axial parenchyma, TS. c: Homocellular rays composed of procumbent cells; vasicentric tracheids; vesselelements with simple perforation plates (PP), TLS. d: Vessel-ray parenchyma pits (VRP) with reduced borders, vertical,RLS. e: Crystalliferous axial parenchyma strand (C) with a single crystal per chamber; ray with procumbent cells, RLS. f: Aggregate ray (right) composed of loosely associated 1–2-seriate rays, TLS. g: Uniseriate rays, thin-walled tyloses in vessels, vasicentric tracheids (VT). Lithocarpoxylon sp., UF 279-84864. h, i: Semi-ring porous wood, exclusively solitary vessels in radial arrangement. j: Aggregate ray and uniseriate rays. k: Scalariform perforation plate with fewer than 10 bars. l: Vessel-ray parenchyma pits with reduced borders to simple, vertical. Scale bars: 200 µm in a, b, f, h, j; 100 µm in c, i; 50 µm in d. e; 20 µm in k, l.