Laurinoxylon, FELIX EMEND DUPERON

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 : 9-11

LAURINOXYLON FELIX EMEND DUPÉRON , DUPÉRON-LAU- DOUEREIX, SAKALA, DE FRANCESCHI, 2008 LAURINOXYLON SP. A OF DIETZ HILL

FIG. 5A–F

Description— Growth ring boundaries distinct, marked by radially flattened fibers ( Fig. 5A, B ). Diffuse-porous; vessels solitary (56%) and in radial pairs ( Fig. 5A, B ); mean tangential diameter 84 ( SD =14), range 62–110 µm. Simple perforation plates; intervessel pits crowded alternate ( Fig. 5C ), polygonal in outline, 6–7–9 µm in horizontal diameter;coarse vessel-ray parenchyma pits with reduced borders, horizontally enlarged ( Fig. 5D ); vessel element length averages 339 ( SD =82), range 158–497 µm; tyloses present, thick-walled.

Axial parenchyma scanty paratracheal parenchyma, 4–6 cells per strand.

Fibers without obvious pits; non-septate, rarely septate; thin-to-thick-walled ( Fig. 5E, F ).

Rays 1–3-seriate ( Fig. 5F ), multiseriate rays heterocellular with 1–3 rows of marginal square/upright cells ( Fig. 5E ); average ray height 338 µm ( SD =141) µm, range 132–662 µm; 6–8 rays per mm.

Oil/mucilage cells present, but not common ( Fig. 5B, E, F ), isolated among fibers and possibly in ray margins.

Specimen— UF 278-84868, estimated maximum diameter 6 cm.

Occurrence— Dietz Hill ( UF 278).

Comments— The cross sections give the impression that axial parenchyma is abundant, but the longitudinal sections show that it is scanty paratracheal.

Comparison with modern woods— A search for diffuse-porous woods with randomly distributed vessels that are solitary and in short multiples (1p 5p 6a 7a 8a 9a 10a 11a), simple perforation plates (13p), alternate intervessel pits that are not minute (22p 24a), vessel-ray parenchyma pits with reduced borders to apparently simple, horizontally elongate (32p), non-septate fibers with simple pits (61p 66p), scanty paratracheal not accompanied by obvious axial parenchyma (78p 80a 83a 85a 86a), rays 1–3 seriate (97p), not homocellular (104a 105a), and oil/mucilage cells among fibers (126p) yields only members of the Lauraceae . The IW search for these features returned species of the genera Beilschmiedia Nees (1831) , Cryptocarya R. Br. (1810) , Lindera Thunb. (1783) , Litsea Lam. (1792) , and Ocotea Aubl. (1775) . The inclusion of oil/mucilage cells in rays (124p) yielded the same genera. We did not observe any scalariform perforation plates in this wood, but given that there is only one small sample, we cannot exclude the possibility of them being a rare occurrence in the original tree.

Richter’s work on the family is the most comprehensive and he noted that there is overlap in the anatomical features of some genera making it difficult in some cases to identify an isolated piece of lauraceous wood to a single genus ( Richter 1981, 1987). Reviewing images in wood anatomical atlases (e.g., the FFPRI on-line database and Itoh et al. 2022) confirms this. There is also considerable intraspecific variation as shown by the image database of FFPRI that includes multiple samples of single species. For example, the 27 samples of Lindera erythrocarpa Makino (1897) vary markedly in abundance of oil/ mucilage cells and axial parenchyma abundance as do 14 samples of Litsea acuminata (Blume) Kurata (1968) .

Comparisons with fossil woods— The diagnosis of Laurinoxylon Felix as emended by Dupéron et al. (2008) is broad enough to accommodate this Dietz Hill wood— vessels solitary and in radial multiples, perforation plates simple and sometimes scalariform (we interpret that to mean that perforation plates can be exclusively simple), intervessel pits alternate and moderately large, tyloses present, paratracheal parenchyma (type and abundance not specified), 1–5-seriate rays (rays 1–3 fall within this range), slightly heterocellular and less than 1.0 mm high, ray-vessel pits large and often stretched, libriform fibers, oil or mucilage cells (idioblasts) present (no mention of location).

A search of InsideWood’s ‘Fossil Hardwood’ database for the same features used for modern hardwoods yield- ed two reports of Cinnamomoxylon (Huard) Gottwald (1997), three of Cryptocaryoxylon Leisman (1986) , ten of Laurinoxylon and one of Litseoxylon Huang et al. (2018) . Of these the most similar is the Paleocene Laurinoxylon sp. B from the Denver Basin, Colorado, because oil/mucilage cells are not common and are amongst the fibers and ray parenchyma, however, the Paleocene wood has wider rays (Wheeler et al. 2019).

The literature is awash with reports of fossil Lauraceae dating back to mid-1800s with woods ranging in age from the late Cretaceous through the Cenozoic (see list in Gregory et al., 2009). Of those, among the most important is the critical review and summary by Dupéron-Laudoueneix and Dupéron (2005). Subsequent publications describing Lauraceae woods include those by Boonchai and Manchester (2012), Franco (2012), Shukla et al. (2013), Brea et al. (2015), Franco et al. (2015), Koutecký and Sakala (2015), Mantzouka et al. (2016), Cevallos-Ferriz et al. (2016, 2021), Jud and Dunham (2017), Estrada-Ruiz et al. (2018), Huang et al. (2018), Mantzouka (2018), Akkemik et al. (2019, 2021); Güngör et al. (2019), Parrott (2019), Pérez-Lara and Estrada-Ruiz (2019), Wheeler et al. (2019), Ruiz et al. (2020), and Vasquez-Loranca and Cevallos-Ferriz (2022). Lauraceae fossil woods are common and relatively diverse (seven species) in the nearby middle Eocene Clarno Nut Beds ( Wheeler and Manchester 2002). These more recent publications all include comparisons of the new species described therein with those previously described.

Because of the variation within Lauraceae , we prefer not to create a new species based on a single sample, but to refer to it as Laurinoxylon sp. A of Dietz Hill.

Figures

Figure 5. Lauraceae. Laurinoxylon sp., UF 278-84868. A, B. Diffuse-porous wood with distinct growth ring boundaries; vessels solitary and in radial pairs, * to the left of an oil cell., TS. C. Crowded alternate intervessel pits, polygonal in outline, tyloses, TLS. D. Vessel-ray parenchyma pits (VRP) with reduced borders to simple, RLS. E. Oil/mucilage cell (OC), RLS. F. Rays 1-3-seriate with marginal rows of 1‒3 upright/square cells; likely oil/mucilage cell (OC), mostly non-septate fibers, TLS. Scale bars=200 µm in A; 100 µm in B; E, F; 20 µm in C, D.