Trochodendron beckii (HERGERT et H.K.PHINNEY) R.A.SCOTT et E.A.WHEELER, 1982

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 : 322-323

Trochodendron beckii (HERGERT et H.K.PHINNEY) R.A.SCOTT et E.A.WHEELER, 1982

Text-fig. 11j–m

M a t e r i a l. UF279-24558 (estimated minimum diameter of stem 15 cm), USNM 326709 (holotype, estimated minimum diameter 18 cm).

D e s c r i p t i o n. Growth rings distinct, marked by noded rays and abrupt transition in radial diameters of latewood tracheids to the subsequent ring’s earlywood tracheids. Vessels absent. Transition from earlywood to latewood abrupt. Tangential diameter of earlywood tracheids 29 (7), 15–51 µm; tangential diameter of latewood tracheids 26 (5) µm, 17–42; scalariform intertracheary pitting observed on radial walls; axial parenchyma rare, occasional isolated cells; rays of two distinct sizes: uniseriates and multiseriates up to 15 cells wide; uniseriates numerous, composed

1. Watari (1952), 2. Takahashi and Suzuki (1988), 3. Wheeler and Manchester (2002), 4.Wheeler and Dillhoff (2008), 5. Jeong et al. (2009), 6. Bayam et al. (2018), 7. Akkemik et al. (2016)

* 50–600 reported as range, with 750 µm given as outlier.

exclusively of upright cells; central cells of multiseriate rays procumbent, with up to 10 marginal rows of upright cells, heights of multiseriate portions of the rays 0.7–1.56 mm.

Note: We did not measure total ray height including the uniseriate margins because it was difficult to be sure of where the uniseriate margins ended.

R e m a r k s. Vesselless woods are rare among angiosperms, and this specimen with its wide heterocellular rays and scalariform bordered pits has features of Trochodendraceae ( Bailey and Nast 1945, Hergert and Phinney 1954). This specimen from the Post Hammer locality (UF 279) further documents the occurrence of Trochodendron wood in the Eocene of Oregon ( Scott and Wheeler 1982). This species was previously recognized from the Miocene of Oregon ( Hergert and Phinney 1954) from the same formation where fossil trochodendraceous infructescences and leaves have been recognized ( Manchester et al. 2018). There are differences in the quantitative features (tracheid diameters, ray width) between the woods from these separate occurrences, but we don’t consider them to be great enough to treat them as different species. Although the two extant genera of this family, Trochodendron and Tetracentron , are confined to eastern Asia, the family is well represented in the Cenozoic of western North America and known from leaves and fruits of both modern and extinct genera ranging from Paleocene to Miocene ( Manchester et al. 2018, Manchester et al. 2021).

Figures

Text-fig. 11. Acer Post Hammer species 1, UF 279-34456. a, b: Diffuse-porous wood with distinct growth rings, marked by marginal parenchyma, vessels solitary and in short radial multiples, TS. c: Crowded alternate intervessel pits, TLS. d: Simple perforation plates, helical thickenings in vessel elements, TLS. e: Rays 2–3-seriate, gum deposit in vessel element, TLS. Acer Post Hammer species 2. UF279-34466. f: Diffuse-porous wood with distinct growth rings, marked by marginal parenchyma, vessels solitary and in short radial multiples, TS. g: Alternate intervessel pits, helical thickenings in vessel elements, TLS. h: Rays 1–4(–5)-seriate, TLS. i: Crystalliferous strand, multiseriate ray, TLS. Trochodendron beckii, UF 279-24558. j, k: Distinct growth rings, abrupt transition from earlywood to latewood, vesselless, wide raysnoded atgrowth ring boundaries, TS. l:Rays of two distinct sizes, uniseriate and multiseriates>10-seriate, TLS. m. Scalariform intertracheary pits. RLS. Scale bars: 500 µm in j; 200 µm in a, f, k, l; 100 µm in b, h; 50 µm in c, d, e, g, i, m.