Platanoxylon haydenii, (FELIX) SUSS & MULLER-STOLL, 1977, 1977

Wheeler, Elisabeth A., Manchester, Steven R. & Baas, Pieter, 2023, A late Eocene wood assemblage from the Crooked River Basin, Oregon, USA, PaleoBios 40 (14), pp. 1-55 : 11-12

PLATANOXYLON HAYDENII (FELIX) SÜSS & MÜLLER-STOLL, 1977

FIG. 6A–F

Description— Wood diffuse-porous ( Fig. 6A, B ). Growth rings present, marked by slightly noded rays ( Fig. 6B ) and 1–2 rows of radially narrow fibers. Vessels solitary and in short multiples, some tangentially arranged ( Fig. 6A, B ); average tangential diameters range from 68 (14)–80 (12) µm; average number of vessels per mm 2 ranges from 40–63. Perforation plates exclusively scalariform ( Fig. 6D ), 4–40 bars per plate observed; intervessel pits opposite ( Fig. 6E ), vessel-ray parenchyma pits not observed. Fibers non-septate, pits not observed. Axial parenchyma diffuse, diffuse-in-aggregates, and in interrupted short uniseriate lines ( Fig. 6A–C ). Rays of two distinct sizes, larger rays typically over 1 mm and more than 10–seriate (6 F), maximum ray widths 20–30 cells, composed of procumbent cells, sometimes with 1–2 marginal rows of square cells.

Specimens— UF 278-84874, 84879, 84881, 84885, estimated maximum diameters 12 cm, 4 cm, 2.3 cm, 12 cm.

Comments— As was the case for the platanaceous wood from the Post Hammer locality ( UF.279) ( Wheeler and Manchester 2021), we were not able to clearly see the vessel-ray parenchyma pits in the Dietz Hill Platanaceae. However, their other features indicate they are Platanoxylon : diffuse-porous wood; narrow numerous vessels, predominantly solitary vessels, with occasional tangential multiples; scalariform perforation plates; intervessel pits predominantly opposite; diffuse and diffuse-in-aggregates parenchyma; tall and wide rays composed mostly of procumbent cells. There was variation in the ray sizes. In the samples that were small entire axes ( UF 278-84881, UF 278-84879), rays more than 10-seriate were less common. The characteristics that distinguish Platanaceae woods from other woods with wide rays (e.g., Fagus L., 1753, and Euptelea Siebold and Zucc., 1840 ) were detailed by Scott and Wheeler (1982) and Wheeler and Manchester (2002, 2014, 2021) and are repeated in detail in our discussion of Fagus herein.

We also searched the InsideWood database for modern and fossil woods with the following suite of features: 1p, 5p, 10a, 13a, 14p, 21p, 41p, 46a, 50a, 66p, 76p, 77p, 79a, 80a, 83a, 84a, 85a, 99p, 102p, 103p, and allowing no mismatches. This yielded four species of modern woods: three Ilex Tourn. ex L. ( Aquifoliaceae ), in which radial multiples are of regular occurrence and rays are more heterocellular, and Carpodetus serratus J.R. Forst. and G.Forst. (1776) ( Rousseaceae ), which has rays with a high proportion of square and upright cells. The rays of the Dietz Hill ( UF 278) platanaceous woods have predominantly procumbent cells with one to only a few marginal rows of square cells ( Fig. 6E, F ). Of the six fossil species returned, four can be dismissed because they lack information on critical diagnostic features, leaving only reports of Platanoxylon haydenii from the early middle Eocene of Yellowstone National Park, USA ( Wheeler et al. 1977) and the middle Eocene Nut Beds flora, Oregon, USA ( Wheeler and Manchester 2002).

Almost all western North America’s Eocene fossil wood localities have Platanaceae woods. The nearby Post Hammer locality ( UF 279) had both Platanoxylon with exclusively scalariform perforation plates and Platanus L. (1753) with both simple and scalariform perforation plates ( Wheeler and Manchester 2021). Woods similar to P. haydenii are common in the older Clarno Formation, with multiple samples occurring at both the Nut Beds ( Wheeler and Manchester 2002) and Hancock Canyon ( Wheeler and Manchester 2014). A single infructescence of Platanaceae was recovered at UF 278 (Dietz Hill), it could not be determined if it was Platanus or the extinct genus Macginicarpa Manchester (1986).

Figures

Figure 6. Platanaceae. Platanoxylon haydenii. A, B. Diffuse-porous wood, vessels mostly solitary, a few tangential multiples; diffuse and diffuse-in-aggregates axial parenchyma; fiber walls of medium thickness, TS, UF 278-84881(A), UF 278-84874 (B). C. Scalariform perforation plates, UF 278-84874, RLS. D. Opposite intervessel pitting, UF 278-84874, TLS. E. Wide (>10-seriate) and tall (>1 mm) rays, UF 278-.84874, TLS. F.Rays composed predominantly of procumbent cells, UF 278-84879, RLS. Scale bars=500 µm in E; 200 µm in A; 100 µm in B, F; 50 µm in C, D.