Quercinium, Unger, 1842

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 : 18-19

QUERCINIUM SP.

FIG. 9A–F

Description— Growth rings boundaries present but not well-defined ( Fig. 9A ), marked by radially flattened latewood fibers, and differences in vessel diameter between latewood and earlywood of subsequent rings.

Diffuse porous to semi-ring porous. Vessels with a very slight tendency to diagonal arrangement; exclusively solitary; vessels circular in outline ( Fig. 9A ); vessel tangential diameters average 88 (SD=17) µm, range 53–133 µm; perforation plates exclusively simple ( Fig. 9B ); pits to vasicentric tracheids circular bordered, alternate ( Fig. 9C ); vessel-ray parenchyma pits enlarged with reduced borders and vertical to diagonal ( Fig. 9D ). Tyloses present.

Vasicentric tracheids present ( Fig. 9C ). Fibers non-septate, most commonly without distinctly bordered pits.

Axial parenchyma diffuse and probably diffuse-in-aggregates, difficult to see in transverse section, but visible in longitudinal sections, 4–8 or more cells per strand ( Fig. 9E, F ).

Rays of two distinct sizes, uniseriate and multiseriate rays to 15+ cells wide ( Fig. 9E, F ); wide rays quite rare. Uniseriate rays usually less than 12 cells high (Fig. E, F). Mainly composed of procumbent cells.

Crystals not observed.

Specimen— UF 278-84878, estimated maximum diameter 8+ cm.

Occurrence— Dietz Hill (UF 278).

Comparisons with extant plants— The combination of exclusively solitary vessels, simple perforation plates, vasicentric tracheids, vertically oriented vessel-ray parenchyma pits with reduced borders, and two size classes of rays (not aggregate rays) indicates that this wood belongs to the Fagaceae , subfamily Quercoideae Oersted (1753) (Wheeler, et al. 2022). The diffuse- to semi-ring-porosity suggests an evergreen Quercus L. (1753) or Lithocarpus Blume (1825) , but they typically have aggregate rays according to Suzuki and Ohba (1991), as does the western U.S. endemic Notholithocarpus Manos, Cannon and S.H.Oh (2008) ( Wheeler et al. 2022). However, one (TWTw 20973) of the twelve Lithocarpus samples in the FFPRI image database appears to have rays similar to UF 278-14 as do multiple samples of diffuse-porous to semi-ring-porous Quercus spp. (e.g., TWTw 19013, 19097, 25282, 22654, FFPRI Wood Identification Database Team, 2002). In the Naturalis slide collection (Lw), two Lithocarpus species ( Lithocarpus ewyckii (Korth.) Rehder (1929) , L. solerianus (Vidal) Rehder (1919) and numerous species of diffuse- to semi-ring-porous Quercus (e.g., Quercus agrifolia Née, 1801 ; Q. gilva Blume, 1850 ; Q. ilex L., 1753; Q. phellos L., 1753) have rays similar to this fossil.

Comparisons with fossil woods— Probably because of a combination of original abundance in ancient landscapes, resistance to decay, and ease of recognition, reports of fossil Quercoideae woods, especially oaks, are common (see Gregory et al. 2009). At the nearby Post Hammer locality (UF 279), there are three Quercoideae woods, two Lithocarpoxylon (Petrescu) emend. Suzuki and Ohba (1991) and a Quercus of the Red Oak Group ( Wheeler and Manchester 2021), and one at the middle Eocene Clarno Nut Beds, Quercinium crystallifera Scott and Wheeler (1982) .

Because this wood has features found in both Quercus and Lithocarpus , we are not assigning it to Quercus . The emended diagnosis and discussion of Lithocarpoxylon indicate that this genus is for Quercoideae woods with aggregate rays ( Petrescu 1978, Suzuki and Ohba1991), and because this wood does not have aggregate rays we do not assign it to Lithocarpoxylon.

Quercinium vs Quercoxylon — Th e history of generic names for woods resembling Lithocarpus and Quercus is complex and has been discussed at length by Müller-Stoll and Mädel (1957), Brett (1960), Mädel-Angeliewa (1968), and Gros (1988). Relying on these publications, the best we can sort out is as follows. The oldest name applied to such woods is Kladenia used by Göppert in 1839, but Müller-Stoll and Mädel (1957) argued against using this name. Unger (1842) proposed the name Quercinium for fossil wood resembling Quercus . The name Quercoxylon was first used by Hoffman (1929), but it was not designated as gen. nov. and Quercoxylon Hoffman seems to have been mostly ignored. Subsequently, Kraüsel (1939) again proposed the genus Quercoxylon Kräusel and later Müller-Stoll and Mädel (1957, p. 125) provided a formal diagnosis for Quercoxylon (Kräusel) emend. Müller-Stoll and Mädel (1957) . In their discussion, Müller-Stoll and Mädel note that Quercoxylon and Quercinium are completely identical in content [“ Quercoxylon Kraüsel and Quercinium Unger stimmen inhaltlich völlig überein”]. Although Quercinium has priority ( Unger 1842), they stated that Quercoxylon Kraüsel (1939) should be used because most authors are of the opinion that fossil woods named after a modern genus should use - oxylon ( Müller-Stoll and Mädel 1957, p. 125–126). There is no formal requirement to use - oxylon in a generic name for a fossil wood. Consequently, we are assigning this wood to Quercinium Unger because that name has priority.

A noteworthy feature of this Dietz Hill Quercinium is that it does not have a distinct radial, diagonal, or dendritic vessel arrangement. This feature also characterizes Quercinium porosum Brett (1960) from the British Eocene, which has markedly wider vessels which average 237 µm in tangential diameter. We do not know whether this Dietz Hill sample might be root wood which could explain the lack of a distinct vessel arrangement pattern ( Cutler et al. 1987). We are not creating a new species for this small, single sample of Quercoideae wood, and think it is sufficient to report its occurrence at the Dietz Hill (UF 278) locality.

Figures

Figure 9. Fagaceae. Quercinium sp, UF 278-84878. A. Diffuse- to semi-ring-porous wood; vessels exclusively solitary, very slight tendency to diagonal arrangement, TS. B. Simple perforation plates (PP), RLS. C. Vasicentric tracheids, uniseriate rays, axial parenchyma strands, TLS. D. Vessel-ray parenchyma pits with reduced borders to simple, tyloses, RLS. E, F. Rays of two distinct sizes, TLS. Scale bars=200 µm in A, E; 100 µm in B, C, F; 50 µm in C; 20 µm in D.