Late woods from Cherokee Ranch, Colorado, U.S.A.

Elisabeth A. Wheeler1*, Peter K. Brown2, and Allan J. Koch2 1Department of Forest Biomaterials, North Carolina State University, Campus Box 8005, Raleigh, NC 27695-8005, and North Carolina Museum of Natural Sciences, 11 W. Jones St., Raleigh, NC 27601, U.S.A. 2Cherokee Ranch Science Institute, 6113 N. Daniels Park Rd., Sedalia, CO 80135, U.S.A. *Correspondence should be addressed to: [email protected]

ABSTRACT The objectives of this paper are to: (1) describe the geologic setting of Fossil woods are common in the Late through early Eocene rocks the Cherokee Ranch wood locality; (2) of the Denver Basin, Colorado. The overwhelming majority of these woods are describe and compare the Cherokee dicotyledonous angiosperms. A new locality for fossil woods, Cherokee Ranch, Ranch fossil woods to previously in the upper D1 stratigraphic sequence (Denver Formation) is described, and evi- described Denver Basin woods; and dence for it being late Paleocene is reviewed. Most Cherokee Ranch woods resem- (3) give the basis for proposing a new ble previously described Denver Basin angiosperm woods, but there is one new genus, Ubiquitoxylon. type of wood attributed to the family . A new genus, Ubiquitoxylon, is proposed for woods with the combination of features commonly seen in the GEOLOGIC SETTING Cherokee Ranch woods. Denver Basin Paleocene woods differ from Paleocene wood assemblages to the north (Wyoming and Montana), where conifer woods Character of Petrified Logs are common and angiosperms are rare. The width and spacing of the water-con- ducting vessels and the lack of distinct growth rings in almost all of the Cherokee The 13.7-square-km Cherokee Ranch woods suggest that these did not experience water stress, and there Ranch (Fig. 1) is one of the best loca- was no pronounced seasonality. tions in the south Denver Basin for Paleogene petrified wood. KEY WORDS: Colorado, Denver Basin, fossil wood, functional traits, Approximately 40 logs (up to 1.25 m Lauraceae, paleobotany, paleoclimate, secondary xylem, vessels. in diameter and up to 10 m in length) have been found scattered over 600 INTRODUCTION square meters, the area within the upper D1 stratigraphic sequence that Little is known about the wood anatomy of Paleocene angiosperm trees, with contains logs. The logs appear to have fewer than 90 wood types described worldwide, and fewer than 25 reported for been carried by paleochannels, rather North America (InsideWood, 2004-onwards; Wheeler, 2011). Therefore, any new than an in-place fall, perhaps during locality for Paleocene angiosperm wood is important for shedding light on past high-water events, and deposited on diversity and vegetation types. The wood anatomical traits of the logs found and covered by sandbars composed of at Cherokee Ranch, Douglas County, Colorado, provide insights into the envi- coarse sand. The log-bearing sandbars ronment of the Paleocene of the southern Denver Basin. Mustoe and Viney (2017) were then submerged below the water described the mineralogy and fossilization process of the Cherokee Ranch woods. table. Logs appear stripped of branches This study complements the considerable amount of previous work on the pale- and bark from transit. No vertical trees ontology of the Denver Basin, done mostly for leaves and pollen (summaries in or stumps are present. Iron-oxide- Johnson et al., 2003; Raynolds and Johnson, 2003). cemented crusts of sandstone that coat Almost all angiosperm trees have vessel elements for water conduction, fibers and encase the petrified trees testify for support, parenchyma for storage, radial transport (rays), and wound response. to the fact logs lay where originally Variations in the proportions, sizes, arrangements, and connections between these deposited (Fig. 2). Rapid petrification cells are used in wood identification (Wheeler and Baas, 1998). For fossil wood, it can by silica from the enclosing tuffaceous, be difficult to be more specific than determining the family to which a wood sample feldspathic sandstone resulted in wood belongs. Sometimes this is because some genera within a family overlap in their wood anatomical features being preserved anatomical features or because features important for distinguishing genera may not in many logs. Many of the logs pre- be preserved in the fossil. Regardless of the affinities of the fossils, wood anatomical serve enough detail to be identified features, especially those related to water conduction (vessel diameter and frequency), as to family and genus. Topographic provide general information on environments (e.g., Baas, 1986; Carlquist, 1975, 2001). relief on Cherokee Ranch is 233 m.

Rocky Mountain Geology, May 2019, v. 54, no. 1, p. 33–46, doi:10.24872/rmgjournal.54.1.33, 7 figures, 1 table, 1 appendix 33 Received 8 October 2018 • Revised submitted 21 March 2019 • Accepted 30 March 2019 • Published online May 2019 For permission to copy, contact [email protected] © 2019 University of Wyoming; Gold Open Access: This paper is published under the terms of the CC-BY license.

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tains bones of titanotheres (Thorson, 2011). In the D1, logs occur over a 47-m interval mostly near the top of D1. Three quarters of the logs are found in a 12-m interval, elevation ~1,899–1,911 m (~6,230–6,270 ft.). (Note: both the metric system, as preferred by Rocky Mountain Geology, as well as measurements in feet are used in various places of the paper because all of the older data that are referenced on Cherokee Ranch topographic maps and Castle Pine core holes are in feet.)

Mapping of the Denver Basin Paleosol

In 2015, A.J. Koch geologically mapped the Cherokee Ranch at 1:5,000 scale (unpublished data available at the Philip S. Miller Library, Douglas County Libraries’ Archives and Local History). The mapping shows that the Denver Basin paleosol is clearly exposed in multiple loca- tions and can be correlated around the ranch and with the nearby Castle Pines core hole 27995F, 2.5 km to the east. The Denver Basin paleosol can be differentiated on the ranch from four other reddish, oxidized horizons that were also mapped. We believe that the Denver Basin paleosol mapped on the ranch is a dependable stratigraphic horizon to help understand the overlying and underlying stratigra- phy. Limited radiometric dates suggest that the base of the Denver Basin paleosol is approximately 55 Ma (Raynolds, Figure 1. Map showing location of the Cherokee Ranch 2002). Eocene leaves have been confirmed in D2 on the fossil forests. Figure from Mustoe and Viney, 2017. ranch, ~90 ft (~30 m) above the base of the paleosol (I. Miller, personal communication, 2010; see Fig. 4 this paper). Cherokee Mountain (2,024 m) is clearly visible from U.S. 85 near Sedalia. All strata on the ranch are Paleogene in age. Age of the Strata that Contain Petrified Wood The history of private ownership of Cherokee Ranch and the rugged terrain of the site have helped preserve the wood from No palynological work or age dating has been done on human predation over the years. the ranch prior to one zircon laser ablation sample taken in 2015 (Koch et al., 2018). The nearest age control is in the Ranch Stratigraphy Castle Pines core hole 27995F. Figure 4 shows the strati- graphic relationship between the Castle Pines core location, Paleogene strata are all mostly flat-lying with a regional 2.5 km to the east, and a measured section in the area of the 1–2° dip to the east. Formations exposed on the ranch petrified wood on the ranch. The Denver Basin paleosol in include the Denver Formation (D1), Dawson Arkose (D2), the Castle Pines core overlies Paleocene age strata with paly- and Castle Rock Conglomerate (Tcr) (Fig. 3). The lower nological ages of P1 (oldest) through P3 (youngest) and one 133 m (436 ft) of Denver Formation strata are believed to be radiometric date of 63.94 ± 28 Ma (Obradovich, 2002; see Paleocene D1 sequence (Raynolds, 2002). Only the upper Fig. 4 this paper). No younger palynological zones (P4–P6) half of the 133 m (436 ft) of D1 is well exposed. The Denver were found in the Castle Pines core. Because late Paleocene Basin paleosol overlies the D1 and comprises the base of the age strata are rare in the Denver Basin (Nichols and Dawson Arkose, D2 sequence, of Eocene age. The Denver Fleming, 2002), one might expect a similar age (P3) below Basin paleosol on the ranch varies in thickness from about the paleosol on nearby Cherokee Ranch; however, new age 5 m to 30 m. The D2 sequence is composed of up to 100 evidence plus more recent fieldwork argues that some of the m of mostly conglomerate and sandstone. The Castle Rock ranch strata may be much younger than the P3 age in the Conglomerate (Tcr) of late Eocene age is a very coarse flu- Castle Pines core. More recent palynology work by Nichols, vial deposit, 83 m thick, that cuts into the underlying D2 reported by Thorson (2011), indicates that P6-age strata may and trends diagonally (NW–SE) across the south end of the not be as rare as previously thought. Multiple samples taken ranch (Koch et al., 2018). The Castle Rock Conglomerate is by Thorson within 33 m of the base of the Dawson Arkose older than the end of the Eocene (33.9 ma) because it con- yielded P5 and P6 ages, leading Thorson to conclude that

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Figure 2. One of the Cherokee Ranch logs. Note the iron-oxide-cemented sandstone carapace on the left side of the log.

the age of the Dawson Arkose is still not completely under- Cherokee contains zircon ages that suggest palynological ages stood (Thorson, 2011, p. 37). As discussed in the next sec- as young as P6. More sampling is warranted to support the tion, our recent zircon laser ablation data does not agree laser ablation evidence. with the Castle Pines core or conventional regional wisdom The most probable provenance for the Paleocene zir- predicting older Paleocene as an age for our petrified wood cons found on the ranch is the Laramide igneous province horizons. in the northern part of the Colorado mineral belt (40–80 km to the north). Koch et al. (2018) reached similar con- New Evidence for a Late Paleocene Age for Cherokee clusions for the Paleocene zircons found in the Castle Rock Ranch Petrified Wood Conglomerate. The zircon northern provenance is further supported by D1 conglomerates above and below the sam- Koch et al. (2018) utilized laser ablation dating of zircons pling site (Fig. 5). The conglomerates contain Precambrian to separate lithofacies within the Castle Rock Conglomerate. Coal Creek Quartzite, derived from Coal Creek Canyon, As part of this work, a sample was taken on Cherokee Ranch which lies 60 km north of the ranch (Koch et al., 2018). As in D1 sandstone adjacent to the petrified wood 2 m below the shown in Figure 4, the 56-Ma sample is at the same eleva- base of the Denver Basin paleosol. The distribution and age tion and stratigraphically correlative with much of the petri- of the zircons in the sample show an undeniable geometric fied wood located 0.2 km directly to the west. On Figure 4, concentration within the Paleocene (65–55 Ma). The data are the enlargement of the log-bearing interval, a dashed jagged shown in Figure 5. The youngest zircon age in the distribu- line shows a proposed lithofacies relationship between the tion is 56 Ma. The strata cannot be older than the youngest northern provenance and western provenance ranch stream zircon. Further, 90% of the 64 zircons in the distribution have systems. The south-flowing streams from the north, carry- Paleocene ages younger than 64 Ma, the youngest Paleocene ing Coal Creek quartzite and zircons from the mineral belt, in the Castle Pines core. Therefore, the sandstone in the D1 on are interbedded and mixed with east-flowing stream detritus

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Although our evidence is limited to one zircon age and some stratigraphic evidence, we interpret that at least part, and perhaps all, of the petrified wood discussed in this report is late Paleocene in age. More sampling and palyno- logical work is needed to confirm how much late Paleocene section may be on the ranch. The new information on sedi- ment supply from the north may help explain why younger Paleocene strata are deposited on the ranch as compared to much of the southern Denver Basin.

MATERIALS AND METHODS

Sample Preparation and Analysis

Pieces of fossil wood were examined in the field with a hand lens. Eighteen samples from 18 distinct logs that appeared to have reasonably good preservation were selected for thin sectioning. Transverse sections (TS), radial longitu- dinal sections (RLS), and tangential longitudinal sections (TLS) were prepared for each sample. Samples that were too compressed for accurate measurements of quantitative vessel features or too poorly preserved to show minute anatomical details are not discussed herein. The hand samples and slides are archived at the Denver Museum of Nature & Science in Denver, Colorado. The specimen archive at the museum has Figure 3. Generalized stratigraphic column for the south Denver Basin showing the stratigraphic position of the petri- the catalog designation ‘DMNH’ (the institution was for- fied wood on Cherokee Ranch. Figure from Koch et al., 2018. merly called the Denver Museum of Natural History), and the specimens have been assigned DMNH numbers. containing coarse arkosic sandstones derived from the Pikes The descriptions of the woods use terminology consis- Peak Granite to the west. During very high-volume flow, the tent with the International Association of Wood Anatomists’ confluence of these two stream systems was probably condu- (IAWA) “List of Microscopic Features for Hardwood cive to creating obstructions that could favor log jams. Identification” (IAWA Committee, 1989). Tyloses in vessels commonly obscured vessel element end walls so we could Summary of Evidence for a Late Paleocene Age for the measure only a few vessel element lengths. Definitions of the Petrified Wood IAWA hardwood list terms are available on the InsideWood website (http://insidewood.lib.ncsu.edu). For quantitative features, we present mean vessel diameters with the stan- 1. Zircon laser-ablation dating evidence from a sample dard deviation in parentheses and ray heights as minimum– 2 m below the Denver Basin paleosol indicates an age mean–maximum. no older than 56 Ma. So, uppermost D1 strata on the The possible affinities for the fossil woods were initially Cherokee Ranch appear much younger than the P3 investigated using the multiple entry key of the InsideWood palynology age in the Castle Pines core. website (InsideWood, 2004-onwards; Wheeler, 2011), fol- 2. P5–P6 palynology ages have been found in four other lowed by a literature review. Appendix A gives the criteria south Denver Basin locations (Thorson, 2011). used when searching for fossil woods with features similar to 3. North provenance conglomerates on the Cherokee the Cherokee Ranch woods. The InsideWood database con- Ranch can be correlated physically northward (10 km) tains more than 9,000 coded descriptions of both modern to conglomerates in the Highlands Ranch quadrangle and fossil dicotyledonous angiosperms and 46,000-plus that underlie the Denver Basin paleosol. images. 4. D1 strata on the Cherokee Ranch are predominantly We computed the vulnerability index (VI = mean vessel arkosic and sandy, lacking volcanic detritus that is typi- tangential diameter divided by the mean number of vessels cal of lower Paleocene stratigraphy. per square mm) for each wood. Carlquist (1975, 1977) pro- 5. The 56-Ma maximum age of the laser ablation sample posed using VI values as a means of expressing the riskiness agrees with the assumed 55-Ma age for the base of the of a plant’s hydraulics. Low VI values (< 1) as found in woods Denver Basin paleosol. with many narrow vessels suggest that these woods can tol-

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Figure 4. Correlation of the Denver Basin paleosol from a measured section on Cherokee Ranch to the Castle Pines core 27995F. Palynology and age dating in the Castle Pines core show early Paleocene ages vs. the late Paleocene zircon laser- ablation age sampled on the ranch in the same stratigraphic position. Enlargement of the 33-m petrified wood interval on the ranch shows the evidence for a confluence of streams, one from the north and the other from the west (left and right of the jagged [dashed] facies line). Inset shows one of the logs.

erate environments with water stress. A plant with high VI rays are rare; rays are < 1 mm high); (7) axial parenchyma is values (> 3) is one that is unlikely to survive in environments rare or scanty paratracheal with strands usually of four cells; subject to drought or freezing. and (8) fibers are non-septate and/or septate; fiber pits are not obvious. Moreover, the following features are absent: storied RESULTS structure, helical thickenings in vessel elements, sheath cells, perforated ray cells, rays of two distinct size classes, radial Common Features canals, laticifers, and cambial variants. This combination of features characterizes many Late All the Cherokee Ranch samples analyzed to date are Cretaceous to late Eocene fossil woods from the Northern dicotyledonous angiosperms with characters commonly seen Hemisphere. If oil cells are present as well, then the wood in previously described Denver Basin woods (Wheeler and can be assigned to the Lauraceae (Laurel family) (Metcalfe Michalski, 2003). These common characters are: (1) wood is and Chalk, 1950; Richter, 1987; Mantzouka et al., 2016; Jud diffuse porous; (2) vessels are solitary and in radial multiples of et al., 2017). If the diagnostic feature of oil cells is absent, 2–3, without a pronounced pattern of arrangement; (3) perfo- then it is usually impossible to confidently assign such woods ration plates between vessel elements are simple; (4) interves- to a single family because this combination of features occurs sel pits are medium to large in horizontal width and crowded not only in the Lauraceae (order ), but in other alternate, polygonal in outline; (5) vessel-ray parenchyma pits, families in other orders, e.g., Anacardiaceae, Burseraceae, when observed, have much reduced borders or are apparently Kirkiaceae (order Sapindales), Lamiaceae, and Verbenaceae simple, and oval to horizontally elongate; (6) rays are hetero- (order Lamiales). cellular with procumbent body cells and 1–2 marginal rows of In tangential sections, three of the Cherokee Ranch upright cells (the widest rays are 3–5 cells wide; one-cell-wide woods described herein have somewhat enlarged marginal

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uniseriate rays, and the multiseriate rays have well-defined uniseriate margins usually with more than four rows of upright cells (InsideWood, 2004-onwards). We suggest that it would be useful to have a genus for the common combina- tion of features described above, and later in this paper we propose such a genus. Dicotyledoxylon (Gottwald, 1992) and Dryoxylon Schleiden in Schmid (1853, p. 28) have been used for a vari- ety of dicot woods of uncertain affinity, but are problematic. There is no diagnosis of Dicotyledoxylon. It is possible this was a typographical error and that Gottwald intended to use Dicotyloxylon (Chitaley and Patel, 1971). Dicotyloxylon was established for a young stem without secondary xylem, so it is not appropriate for woody stems. Dryoxylon includes woods with relatively few features in common, other than that they have vessels. Edwards (1931) noted, however, that Figure 5. Zircon laser-ablation data from Koch et al. (2018). the only species of Dryoxylon that Schleiden described was Note the age distribution of the zircon ages from 56 Ma to probably not a dicotyledon. 67 Ma. This geometric distribution favors a late Paleocene Unger (1842) was the first to describe a fossil wood age for the sample site. The sample can be no older than the with features of Lauraceae. Unfortunately, he used the name youngest zircon (56 Ma). Notes: (1) Z1 is the name for the oldest sample collected in the zircon laser ablation study by Ulminium for this wood, implying affinities with Ulmus Koch et al. 2018, Fig. 7; (2) The ages of the much younger (elm). Page (1967) pointed out that this name has priority Fish Canyon and Wall Mountain Tuffs are included for over Laurinoxylon Felix (1883), which also was proposed comparison. for woods with lauraceous features. Unger’s original sample was located and used to provide an emended diagnosis for ray cells, but in radial sections we could not confirm that Laurinoxylon (Unger) Felix (Dupéron et al., 2008). Dupéron these cells were oil cells. Nevertheless, we believe it most et al. (2008) and Doweld (2017) proposed rejecting the likely that these woods are Lauraceae. These enlarged cells name Ulminium and conserving the use of Laurinoxylon are sparse, so it is possible the radial sections did not intersect for fossil lauraceous woods because Laurinoxylon has been them. more commonly used for lauraceous fossil woods. We are following their proposals and using Laurinoxylon. We are Nomenclature: Background Discussion not formally proposing specific epithets for the Cherokee Ranch lauraceous woods, but informally designating them Naming fossil dicotyledonous woods having general- as Laurinoxylon Cherokee Ranch sp. A and Laurinoxylon ized features or having poor preservation so that some diag- Cherokee Ranch sp. B. We also relate them to the nostic features cannot be seen is problematic. Wheeler and Laurinoxylon groups of Mantzouka et al. (2016), groups that Michalski (2003) referred to Denver Basin woods lack- are defined by the location of the idioblasts (oil cells). ing oil cells and having the common anatomical charac- ters described above as phyllanthoid type woods and did Descriptions of the Wood Types not assign them to genus. Although these woods share some features with Paraphyllanthoxylon Bailey (1924), Family Lauraceae Jussieu 1789 which is common in the and Paleocene Genus Laurinoxylon Felix emend. Dupéron, Dupéron- of North America, they differ in ray features. Recently, Laudoueneix, Sakala & De Franceschi one of us (EAW) examined slides of the holotype of Laurinoxylon sp. A - Cherokee Ranch Paraphyllanthoxylon arizonense and additional samples col- (Fig. 6A–D) lected at and near the type locality. The rays in all samples Growth rings indistinct (Fig. 6A). Tangential diameter have thin-walled cells, lack obvious marginal rows of upright of vessels 95 (18) µm, 17–19 vessels per mm2; 42% solitary and square cells, and usually have square cells intermixed vessels; intervessel pits crowded alternate and polygonal in with procumbent cells in the body of the ray (Wheeler and outline (Fig. 6B), 8–11 µm across. Vessel-ray parenchyma Lehman, 2009; Jud et al., 2017). Rays in the “phyllanthoid” pits not found. Thin-walled tyloses present. Rays mostly 3–5 Denver Basin woods, including these Cherokee Ranch cells wide (Fig. 6C), ray height 256–420–660 µm; some woods, do not have those ray features. rays appear homocellular composed of all procumbent cells, The Denver Basin woods do not resemble more commonly heterocellular with a single row of square to Phyllanthaceae woods. Woods of this family have abundant upright cells; occasional idioblasts in marginal rows of the

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Figure 6. A–D, Laurinoxylon sp. A. DMNH EPI.40935. A, Indistinct growth rings, diffuse porous wood, vessels solitary and in radial multiples of two or occasionally three, transverse section (TS). B, Crowded alternate intervessel pits, tyloses in vessels, tangential longitudinal section (TLS). C, Rays mostly 3–4 cells wide, TLS. D, Idioblast at a ray margin, TLS. E–H, Laurinoxylon sp. B. DMNH EPI.40941. E–F, Growth ring boundary marked by radially narrowed fibers, vessels solitary and in short radial multiples, axial parenchyma sparse, TS. G, Rays mostly 3–4 cells wide, small x’s to left of idioblasts in ray margins, TLS. H, Idioblast amongst the fibers, simple perforation plates in side view, TLS. I–L, Ubiquitoxylon raynoldsii sp. nov., DMNH EPI.40936. I, Growth ring boundary marked by radially narrowed fibers, diffuse porous wood, vessels solitary and in radial multiples, TS. J, Crowded alternate intervessel pits, TLS. K, Vessel-ray parenchyma pits with reduced borders and horizontally elongate, ray body cells procumbent, radial longitudinal section (RLS). L, Rays mostly 2–3 cells wide, tylo- ses in vessels, TLS. Scale bars: 200 µm in A, E, G, and I; 100 µm in B, D, F, and L; 50 µm in C, H, J, and K.

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rays (Fig. 6D); 4–5 rays/mm. Medium-thick-walled to thick- Material: DMNH EPI.40937; DMNH EPI.40941 walled fibers, non-septate. Comments: Quantitative features primarily from Material: DMNH EPI.40935 DMNH EPI.40941. These specimens represent a new type Comments: Mantzouka et al. (2016) used Werff and of lauraceous wood for the Denver Basin, D1 sequence. The Richter’s (1996) classification scheme for Lauraceae tribes two features that set this wood type apart are: (1) idioblasts because it included wood anatomical characters. Mantzouka within the ground tissue fibers as well as in ray margins; and et al. (2016) suggested that modern genera resembling their (2) distinct growth ring boundaries defined by changes in ‘ 1’ included members of Tribe Laureae (Laurus, the the fibers’ radial diameter and a slight change in vessel diam- Litsea chinensis group) and Tribe Perseae: Dicypellium, North eter. American Persea, Systemonodaphne, and Urbanodendron. This wood fits Laurinoxylon Type 2b of Mantzouka We did not observe septate fibers in DMNH EPI.40935, et al. (2016). According to them, Type 2b’s combination of so it is unlikely to be in Tribe Perseae, which has “ubiqui- features occurs in only three extant genera: (1) Actinodaphne tous septate fibers” (Werff and Richter, 1996). Information p.p. (tropical and subtropical Asia); (2) Nectandra p.p. (tropi- in InsideWood suggests that Litsea is most similar because cal America); and (3) Neolitsea p.p. (Indo-Malaysia to eastern rays in this genus can be wider than three cells (InsideWood, Asia). 2004-onwards; Wheeler, 2011). Litsea is primarily Asian, but Only one report of Laurinoxylon seemanianum Mädel there are a few species in Australia as well as some ranging (Selmeier, 1984) had the combination of features given from North America to subtropical South America (Huang above (Appendix A). et al., 2008). More recently, Huang et al. (2018) created the Laurinoxylon sp. B has a VI value of 5.4. genus Litseoxylon for an Oligocene Chinese wood they con- sidered to belong to the Litsea complex. Their generic diag- Incertae sedis nosis specified presence of helical thickenings throughout Ubiquitoxylon Wheeler gen. nov. the vessel elements and occasional scalariform perforation (Table 1, Fig. 6I–L, Fig. 7A–O) plates; neither feature occurs in the Cherokee Ranch woods. Type species: Ubiquitoxylon raynoldsii Wheeler sp. nov. Wheeler and Michalski (2003) described but did not Generic diagnosis: Growth rings indistinct or distinct. assign species names to some D1 sequence woods with oil Diffuse porous. Vessels solitary and in short radial multi- cells. Both DB.D1 Xylotype 4a (six specimens) and DB.D1 ples, mean tangential diameter between 50–150 µm; fewer Xylotype 4b (one specimen) have oil cells only in the ray than 40 vessels per sq. mm; perforations exclusively simple; margins and thus also belong to Mantzouka et al.’s (2016) intervessel pitting crowded alternate, usually polygonal in Laurinoxylon Type 1. DB.D1 Xylotype 4a differs from the outline, medium to large; vessel-ray parenchyma pits with Cherokee Ranch wood as it has a few scalariform perfora- reduced borders, oval to horizontally elongate; average vessel tion plates. DB.D1 Xylotype 4b differs in having wider ves- element lengths less than 500 µm; axial parenchyma not sels (mean tangential diameter 134 µm), a higher vessel fre- common, sometimes scanty paratracheal; fibers non-sep- quency (23–30 per mm2), and more frequent oil cells. tate and/or septate, medium-thick-walled to thick-walled, We searched InsideWood’s fossil wood database to without distinctly bordered pits; multiseriate rays heterocel- determine if there were other fossil woods with a similar lular with procumbent body cells and 1–2 marginal rows combination of features (Appendix A). There are 93 reli- of square/upright cells, slightly inflated ray cells present or able records of fossil Lauraceae woods in the InsideWood absent; uniseriate rays rare, multiseriate rays less than six database. Of these, Laurinoxylon rennerae (Estrada-Ruiz et cells wide; mean height of multiseriate rays less than 1 mm al., 2018) from the Campanian McRae Formation of New (usually < 500 µm). Storied structure, sheath cells, tile cells, Mexico is the most similar, but it differs in having some rays of two distinct sizes, aggregate rays, normal axial and rarely occurring scalariform perforation plates. radial canals, laticifers, and cambial variants all absent. Laurinoxylon sp. A has a VI value of 5.3. Derivation of generic name: Ubiquitoxylon for the common occurrence of this combination of anatomical fea- Laurinoxylon sp. B - Cherokee Ranch tures in fossil and present-day woods. (Fig. 6E–H) Comments: As mentioned at the beginning of the Growth rings distinct, boundaries defined by changes ‘Results’ section, the combination of features of the Cherokee in fiber radial diameters and a slight change in vessel diameter Ranch woods occurs in more than one family of more than (Fig. 6E–F). Tangential diameter of vessels 99 (17) µm, 17–20 one order, most commonly Anacardiaceae and Burseraceae vessels per mm2; tyloses present, obscuring intervessel and ves- (Sapindales), Lamiaceae, and Verbenaceae (order Lamiales), sel-ray parenchyma pits. Rays mostly 3–4 cells wide; 127–331– as well as Lauraceae (Laurales). 574 µm high, 4–5 / mm (Fig. 6G). Occasional idioblasts in ray We searched the fossil wood database of InsideWood look- margins (Fig. 6G) and amongst the ground tissue fibers (Fig. ing for fossil wood genera that might accommodate the combi- 6H). Medium-thick-walled fibers, septate and non-septate. nation of features given above (see Appendix 1 for coding).

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Figure 7. Ubiquitoxylon raynoldsii sp. nov. A–E, DMNH EPI.40934. A, Vessels solitary and in occasional multiples, TS. B, Crowded alternate intervessel pits, TLS. C, Simple perforation plates, vessel-ray parenchyma pits with reduced borders, RLS. D, Rays mostly 3–4 cells wide, TLS. E, Some rays with enlarged marginal cells, TLS. F–G, DMNH EPI.40938. F, Vessels solitary and in short radial multiples, tendency to diagonal arrangement, axial parenchyma sparse. G, Rays mostly 2–3 cells wide, tyloses in vessels; crowded alternate intervessel pits. H–I, DMNH EPI.40939. H, Vessels solitary and in short radial multiples, TS. I, Rays 3–4 seriate, crowded alternate intervessel pits, TLS. J–O, DMNH EPI.40940. J, Vessels solitary and in short radial multiples, TS. K, Crowded alternate intervessel pits, RLS. L, Vessel-ray parenchyma pits with reduced bor- ders, RLS. M, Rays with procumbent body cells and upright / square marginal cells, RLS. N, Rays mostly four cells wide, marginal ray cells rarely enlarged, TLS. O, Rays 2–4 cells wide, 2-seriate ray with enlarged marginal cells, axial parenchyma strand of four cells, crowded alternate pits. Scale bars: 200 µm in A, D, F, H, J, N; 100 µm in C, E, G, I, M, O; 50 µm in B, K, L.

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Downloaded from http://pubs.geoscienceworld.org/uwyo/rmg/article-pdf/54/1/33/4718720/05401033.pdf by guest on 01 October 2021 Table 1. Variation in Ubiquitoxylon. VTD = vessel lumen tangential diameter, µm; V/mm2 =

vessels per sq. mm; %S = percentage solitary vessels; VEL = vessel element length, µm;

IVP = horizontal diameter of intervessel pits, µm; VRP = vessel-ray parenchyma pits; O =

oval; H = horizontal; RW = ray width in cell number; Inf = inflated ray cells; MsRH = Elisabeth A. Wheeler, Peter K. Brown, and Allan J. Koch multiseriate ray height in µm; Sep = septate fibers present; Ab = absent; ? = status Table 1. Variation in Ubiquitoxylon. VTD = vessel lumen tangential diameter, µm; V/mm2 = vessels per sq. mm; %S = percentage solitaryunknown; vessels; S VEL= some. = vessel element length, µm; IVP = horizontal diameter of intervessel pits, µm; VRP = vessel-ray parenchyma pits; O = oval; H = horizontal; RW = ray width in cell number; Inf = inflated ray cells; MsRH = multiseriate ray height in µm; Sep = septate fibers present; Ab = absent; ? = status unknown; S = some.

ae 2 P P e

13 9–12 21–39 9–13 3–4 ae 34

P4934 23 2

119 17–21 47 3 9–12 2–3 333

P4936 21 6

127 16 24 1 3 323

P493 27 7

13 3 3 1 3– 29

P4939 2 67

11 13–14 2 9–14 3– ae 332

P494 1

Not surprisingly, our search of the fossil wood Phyllanthaceae commonly have uniseriate rays, while uni- database returned records of woods suggested to have seriate rays are rare in these Cherokee Ranch woods. affinities with the Anacardiaceae, Burseraceae, and This wood is similar to Carlquistoxylon Wheeler, Lauraceae. Other suggestions included Euphorbiaceae, McClammer & LaPasha emend. Nunes, Pujana, Escapa, Phyllanthaceae, species of Paraphyllanthoxylon (includ- Gandolfo, Cúneo (Wheeler et al., 1995; Nunes et al., 2018) ing P. marylandense found in association with lauraceous in vessel grouping, diameter, and frequency; perforation [Herendeen, 1991]), Carlquistoxylon (unknown plate type, and parenchyma distribution. Carlquistoxylon dif- affinities), and wood types (xylotypes) with distinctive fers in having longer vessel elements (500 and 800 µm) and anatomy, but of unknown affinities and not assigned to narrower rays. Its diagnosis specifies only non-septate fibers, genus. Burseroxylon Prakash and Tripathi (1973 [issued and slightly inflated ray cells do not occur in the genus. 1975]) differs from the Cherokee Ranch woods because it Samples assigned to Ubiquitoxylon and to Carlquistoxylon are has only septate fibers, ray cells that are frequently cryst- of mature wood so the differences in vessel element length alliferous; vessel-ray parenchyma pits were not described. cannot be attributed to differences in age of the cambia that The genus Euphorbioxylon Felix emend. Mädel (1962) produced these woods. seems to have been misused by some authors. The diag- nosis of this genus mentions abundant apotracheal paren- Ubiquitoxylon raynoldsii Wheeler sp. nov. chyma, which is not a feature of these Cherokee Ranch (Fig. 6I–L, Fig. 7A–O) woods and of some other Euphorbioxylon species. Some Specific diagnosis: Same as for genus fossil woods thought to belong to the Euphorbiaceae were Specific epithet recognizes Dr. Robert (Bob) Raynolds assigned to Euphorbioxylon, even though their features did for his extensive work on Denver Basin geology. not match the generic diagnosis. For instance, axial paren- Holotype: DMNH EPI.40934 chyma is rare in Euphorbioxylon hernense Crawley (2001) Paratype: DMNH EPI.40940 and E. ortenburgense Selmeier (1988). Differences with Additional material: DMNH EPI.40936; DMNH Paraphyllanthoxylon Bailey (1924) have already been noted. EPI.40938; DMNH EPI.40939

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Repository: Denver Museum of Nature & Science. plement the leaf physiognomic analyses of Denver Basin There are some differences between DMNH EPI.40934, Paleocene leaf assemblages (Johnson et al., 2003). DMNH EPI.40938, DMNH EPI.40939, and DMNH To the best of our knowledge, no Paleocene angio- EPI.40940 in vessel diameter, frequency, and groupings sperm woods resembling the woods described herein or the (Table 1). The vessels in DMNH EPI.40934 are more com- previously described Denver Basin woods (Wheeler and monly solitary than in the other four samples, and the vessels Michalski, 2003) have been reported from Wyoming or in DMNH EPI.40938 show a slight tendency to a diagonal Montana (InsideWood, 2004-onwards; Wheeler, 2011). arrangement. We do not consider these differences sufficient to create additional species because this type of variation has CONCLUSIONS been documented within some present-day species. DMNH EPI.40936 differs from other Cherokee Ranch 1. All Cherokee Ranch woods are dicotyledonous angio- woods and from the D1 sequence phyllanthoid woods sperms and further document latitudinal variation in described by Wheeler and Michalski (2003) because its Paleocene floras and provide additional evidence for the growth ring boundaries are more distinct. Changes in fiber Denver Basin vegetation being dominated by angio- radial diameter and vessel diameter are more obvious, and sperms. rays tend to be noded (inflated) at the growth ring boundar- 2. A zircon age and stratigraphic evidence indicate that the ies. Otherwise, its anatomy is similar to DMNH EPI.40934, Cherokee Ranch woods are late Paleocene in age. DMNH EPI.40938, DMNH EPI.40939, and DMNH 3. There are two types of Lauraceae woods, and they have EPI.40940. Growth ring distinctiveness can vary within a spe- features of Laurinoxylon. cies, so we do not consider this difference enough to consider it 4. The combination of features seen in the majority of the a separate wood type and are including it in this species. Cherokee Ranch woods warrants establishing a new The VI values of Ubiquitoxylon samples range from 3.4 genus, Ubiquitoxylon. to 12.4, averaging 7.5. 5. The hydraulic features (vessel diameter and frequency) and lack of distinct growth rings imply that these trees DISCUSSION did not experience water stress or pronounced dor- mancy. The Denver Basin Project—an interdisciplinary, coop- 6. We suggest that continued exploration for fossil woods erative research effort to study the evolution of the Denver in the Western Interior will help document regional Basin—investigated 149 Upper Cretaceous and Paleogene variation in vegetation types and what might be the sites and documented not only changes in megafloral com- dominant species of the Paleocene. position through time, but also variation in coeval floras related to their proximity to the Front Range (Johnson et al., ACKNOWLEDGMENTS 2003). Different plant parts and families vary in the likeli- hood they will enter the fossil record. Invariably, when leaves John McKinney discovered and mapped most of and woods co-occur, the leaf assemblage is more diverse, yet the logs and helped select samples for analysis. National some taxa are unique to the wood assemblage (e.g., Wheeler Petrographic Service Inc. of Rosenberg, Texas, prepared the and Manchester, 2002; Allen, 2017). Consequently, fossil thin sections. Archiving is provided by the Denver Museum wood assemblages contribute to a fuller understanding of of Nature & Science. Cherokee Ranch & Castle as well as ancient vegetation. the Cherokee Ranch Science Institute provided financial The Cherokee Ranch D1 woods are a low diversity assem- support for travel, thin sections, and zircon laser ablation. blage of large angiosperm trunks, probably all Lauraceae. The We thank Ian Miller for his extremely helpful and detailed woods have similar hydraulic strategies, i.e., few and relatively review of our manuscript. We also thank Tom Michalski wide vessels, a strategy only successful where there is little water and Emilio Estrada-Ruiz for their constructive reviews. stress (e.g., Carlquist, 1975; Baas, 1986; Beeckman, 2016). The Rocky Mountain Geology (RMG) Co-Editor Arthur Snoke, high VI values of the Cherokee Ranch woods indicate that these RMG Managing Editor Brendon Orr, and RMG copy trees were not subjected to frost or drought. editor Robert Waggener of Waggener Editorial Services There is debate over how to recognize growth rings deserve thanks for their patience and thorough editorial or growth interruptions in tropical trees (e.g., Silva et al., work. George Mustoe gave permission to use Figure 1 from 2019); however, there is consensus that the lack of well- Mustoe and Viney (2017). defined growth ring boundaries, as occurs in all but one of the Cherokee Ranch woods, indicates lack of pronounced REFERENCES CITED seasonality in water availability or temperature (e.g., Poole and van Bergen, 2006). 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Nichols, D.J., and Fleming, R.F., 2002, Palynology and paly- Dupéron, J., Dupéron-Laudoueneix, M., Sakala, J., and De nostratigraphy of , Paleocene, and Eocene strata Franceschi, D., 2008, Ulminium diluviale Unger: Historique in the Denver Basin, Colorado: Rocky Mountain Geology, v. de la découverte et nouvelle étude: Annales de Paléontologie, 37, p. 135–163. v. 94, p. 1–12. Nunes, C.I., Pujana, R.R., Escapa, I.H., and two others, 2018, A Edwards, W.N.,1931, Dicotyledones (Ligna), in Jongmans, W., new species of Carlquistoxylon from the Early Cretaceous of ed., Fossilium catalogus II: Plantae: Berlin, Germany, W. Junk, Patagonia (Chubut province, Argentina): The oldest record of p. 1–95. angiosperm wood from South America: IAWA Journal, v. 39, Estrada-Ruiz, E., Wheeler, E.A., Upchurch, G.R., and Mack, p. 406–426. 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Schmid, E., 1853, Die organischen Reste des Muschelkalkes im Saal-Thale bei Jena: Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Palaeontologie-Abhandlungen 1853, p. 9–30. Selmeier, A., 1984, Fossile Bohrgänge von Anobium sp. in einem jungtertiären Lorbeerholz aus Egweil (Südliche Frankenalb): Archaeopteryx, v. 2, p. 13–29. ___ 1988, Euphorbioxylon ortenburgense n. sp. from the East Bavarian Molasse with disjunctive ray cell walls: Mitteilungen der Bayerischen Staatssammlung für Paläontologie und Historische Geologie, v. 38, p. 259–273. Silva, M. S., Funch, L.S., and da Silva, L.B., 2019, The growth ring concept: seeking a broader and unambiguous approach cover- ing tropical species: Biological Reviews, v. 94, p. 1,161–1,178. Thorson, J.P., 2011, Geology of Upper Cretaceous, Paleocene, and Eocene strata in the southwestern Denver Basin, Colorado: Denver, Colorado, Colorado Geological Survey Open-File Report 11-02, vi + 53 p. Unger, F.,1842, Synopsis lignorum fossilium plantarum acram- phibryarum, in Endlicher, S., ed., Genera plantarum secun- dum ordines naturales disposita: Wien, Austria, Universitatis Bibliopolam, supplement 2, p. 100–102. Werff, H.V.D., and Richter, H.G., 1996, Toward an improved classification of Lauraceae: Annals of the Missouri Botanical Garden, v. 83, p. 409–418. Wheeler, E.A., 2011, InsideWood—A web resource for hardwood anatomy: IAWA Journal, v. 32, p. 199–211. Wheeler, E.A., and Baas, P., 1998, Wood identification—A review: IAWA Journal, v. 19, p. 241–264. Wheeler, E.A., and Lehman, T.M., 2009, New Late Cretaceous and Paleocene dicot woods of Big Bend National Park, Texas, and review of Cretaceous wood characteristics: IAWA Journal, v. 30, p. 293–318. Wheeler, E.A., and Manchester, S.R., 2002, Woods of the middle Eocene nut beds flora, Clarno Formation, Oregon, USA: IAWA Journal, supplement 3, 188 p. Wheeler, E.A., and Michalski, T.C., 2003, Paleocene and early Eocene woods of the Denver Basin, Colorado: Rocky Mountain Geology, v. 38, p. 29–43. Wheeler, E.A., McClammer, J., and LaPasha, C.A., 1995, Similarities and differences in dicotyledonous woods of the Cretaceous and Paleocene, San Juan Basin, New Mexico, USA: IAWA Journal, v. 16, p. 223–254.

Scientific Editor: Arthur W. Snoke

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Appendix A. Criteria used in searches of the InsideWood fossil wood database for fossil Lauraceae woods similar to the Cherokee Ranch woods, Colorado.

Laurinoxylon Cherokee Ranch sp. A Ubiquitoxylon raynoldsii Wheeler sp. nov. Features used: Wood diffuse porous, vessels not Features used: Growth rings indistinct (2p), wood dif- arranged in a well-defined pattern, vessels solitary and in fuse porous (5p), vessels not tangentially or radially arranged short radial multiples (5p 6a 7a 8a 9a 10a 11a), exclusively (6a 7a 8a), vessels not exclusively solitary or commonly in simple perforation plates (13r 14e), alternate intervessel pits radial multiples of four or more or commonly in clusters (9a that are not minute (22r 24a), vessel-ray parenchyma not the 10a 11a), 13p (perforation plates simple), 22p 24a (alternate same as intervessel pits (30a), mean vessel diameter > 50 µm intervessel pits that are not minute), 40a 43a (vessel mean and < 200 µm (40a 43a), fewer than 40 vessels per sq. mm tangential diameter between 50 and 200 µm), 47p (5–20 (49a 50a), mean vessel element length < 800 µm (54a), fibers vessels per sq. mm), 61p (fibers with simple to minutely without distinctly bordered pits (62a), diffuse-in-aggregate, border pits), 78p 79a 80a 83a 84a (axial parenchyma scanty vasicentric, aliform, confluent, banded, and marginal paratracheal, not vasicentric or aliform or confluent or parenchyma all absent (77a 79a 80a 83a 85a 86a 89a), rays banded), 98p (larger rays commonly 4–10 seriate), 102a not exclusively uniseriate, not commonly > 10-seriate, not (rays < 1 mm high), 106p (heterocellular rays with procum- aggregate, not > 1 mm high, not of two distinct sizes (96a bent body cells and one marginal row of square / upright 99a 101a 102a 103a), rays heterocellular with < 4 marginal cells), 124p 125a 126a (oil cells associated with rays, not rows of square/upright cells (104a 105a 108a), sheath cells, with axial parenchyma or among the fibers). tile cells, storied structure, oil cells, normal axial and radial Results of search: Two records in InsideWood’s fossil canals all absent (110a 111e 120a 303a 304a 130a 305a). wood database had a similar combination of features. DB.D1 Xylotype 4a (Paleocene of Denver Basin), which differs in having some scalariform perforation plates, some samples with > 20 vessels per sq. mm, and slightly narrower rays (Wheeler and Michalski, 2003). Laurinoxylon rennerae from the late Campian McRae Formation, New Mexico, which differs in having some scalariform perforation plates (Estrada-Ruiz et al., 2018).

Laurinoxylon Cherokee Ranch sp. B

Features used: Growth rings distinct (1p), wood diffuse porous (5p), vessels not tangentially or radially arranged (6a 7a 8a), vessels not exclusively solitary or commonly in radial multiples of four or more or in clusters (9a 10a 11a), 13p (perforation plates simple), 22p 24a (alternate interves- sel pits that are not minute), 40a 43a (vessel mean tangential diameter between 50 and 200 µm), 47p (5–20 vessels per sq. mm), 61p (fibers with simple to minutely border pits), 65p (septate fibers present), 78p 79a 80a 83a 84a (axial paren- chyma scanty paratracheal, not vasicentric or aliform or con- fluent or banded), 96e 99e (rays not exclusively uniseriate or > 10 cells wide), 102a (rays < 1mm high), 106p (hetero- cellular rays with procumbent body cells and one marginal row of square / upright cells), 304r 124p 125a 126p (oil cells associated with rays and among the fibers, but not with axial parenchyma). Results of search: Only one report of Laurinoxylon see- manianum Mädel, synonym: Cinnamomonoxylon seemania- num (Mädel) Gottwald (Selmeier, 1984) had the combina- tion of features given above, albeit with variation in the pres- ence/absence of oil cells associated with axial parenchyma or among the fibers.

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