New Late Cretaceous and Paleocene Dicot Woods of Big Bend National Park, Texas and Review of Cretacous Wood Characteristics

Home , Aguja Formation, Cunonia, Paleocene

IAWA Journal, Vol. 30 (3), 2009: 293–318

NEW LATE CRETACEOUS AND PALEOCENE DICOT WOODS OF BIG BEND NATIONAL PARK, TEXAS AND REVIEW OF CRETACOUS WOOD CHARACTERISTICS

E.A. Wheeler1 and T. M. Lehman2

SUMMARY

Three new wood types from the Late Cretaceous and one from the Paleocene of Big Bend National Park, Texas, U.S.A. add to our knowledge of North Ameri- can Late Cretaceous and Paleocene plants. Sabinoxylon wicki sp. nov. provides further evidence of similarities in late Campanian-early Maastrichtian vegetation of Texas, New Mexico, and northern Mexico. This species is characterized by mostly solitary vessels, scalariform perforation plates, vessel-ray parenchyma pits similar to intervessel pits, vasicentric tracheids, and two size classes of rays. Storage tissue accounts for close to 50% of its wood volume. Another of the new Cretaceous wood types, referred to as Big Bend Ericalean Wood Type I, has more than 40% ray parenchyma. Both Big Bend Ericalean Wood Type I and Sabinoxylon have a combination of characters that occurs in the order Ericales (sensu APGII). The third new Cretaceous wood type is from a small axis (less than 3 cm diameter), and has a combination of features that is the most common pattern in extant eudicots (vessels solitary and in radial multiples randomly arranged, simple perforation plates and alternate intervessel pits, and heterocellular rays). The Paleocene wood (cf. Cunonioxylon sensu Gottwald) differs from all other North American Paleocene woods and has characteristics found in the predominantly Southern Hemisphere family Cunoniaceae. The characteristics of these new Big Bend woods contribute to a database for fossil angiosperm woods, and allow for comparison of incidences of selected wood anatomical features in Northern Hemisphere Cretaceous woods from Albian to Maastrichtian time as well as comparison with extant woods. Cretaceous woods as a whole differ from Recent woods in having higher incidences of exclusively solitary vessels, scalariform perforation plates, and wide rays (>10-seriate), and lower incidences of ring porosity, wide vessels (>200 µm), vessels in groups, non-random arrangements of vessels, and marginal parenchyma. The occurrence of relatively high percentages of storage cells (>40%) in some Cretaceous trees is noteworthy; the ability to produce wood with varying amounts and arrangements of parenchyma is likely to be a contributing factor to the success of angiosperm trees in a wide variety of environments. Key words: Big Bend National Park, fossil wood, Ericales, paleobotany, Creta- ceous, Aguja Formation, Javelina Formation, parenchyma, Paleocene, Black Peaks Formation.

1) Department of Wood and Paper Science, North Carolina State University, Raleigh, NC 27695-8005, and NC State Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601-1029, U.S.A. 2) Department of Geosciences, Texas Tech University, Lubbock, TX 79409-1053, U.S.A. 294 IAWA Journal, Vol. 30 (3), 2009

INTRODUCTION

We know relatively little of the wood anatomy of Cretaceous and Paleocene angiosperms. In the early 1990s a compilation based on the literature found worldwide only 108 records of Cretaceous dicot woods and 36 records of Paleocene dicot woods whose anatomy had been described in some detail and for which provenance information was available (Wheeler & Baas 1991, 1993). All but 12 of those 108 Cretaceous woods were from the latest Cretaceous (Campanian-Maastrichtian), and approximately half had characteristics of three genera: Paraphyllanthoxylon, Icacinoxylon, or Plataninium. Since then there have been new reports of Cretaceous dicotyledonous woods, but the number is still low (about 200 records worldwide) so that any new reports of Cretaceous woods contribute to our understanding of the diversity of Cretaceous woody plants. Big Bend National Park in southwestern Texas preserves a continuous sequence of Upper Cretaceous (Campanian-Maastrichtian) through Lower Tertiary (Paleocene) continental strata. We have described a diverse assemblage of both dicot and conifer woods collected from these strata (Wheeler 1991; Wheeler et al. 1994; Lehman & Wheeler 2001; Wheeler & Lehman 2000, 2005). As a result of reviewing recent collections in preparation for an overview of the Cretaceous and Paleocene woods of Big Bend, we discovered three additional Cretaceous wood types and one Paleocene wood type. The objectives of this paper are to describe these new wood types, compare them to other North American Cretaceous-Paleocene woods, to provide an overview of Northern Hemisphere Cretaceous woods and compare them with present-day woods.

STRATIGRAPHY AND SEDIMENTARY FACIES

Upper Cretaceous and Paleogene strata in the Big Bend region of Texas record the gradual withdrawal of the Cretaceous Interior Seaway from North America and preserve a succession of coastal to inland paleoenvironments (Fig. 1). A series of fossil wood horizons occur within coastal lowland deposits of the Aguja Formation, and upward through inland fluvial flood-plain deposits of the Javelina and Black Peaks Formations (Wheeler & Lehman 2000, 2005). The Aguja Formation contains two terrestrial intervals referred to informally as the lower and upper shale members (Lehman & Busbey 2007). Both the lower shale member and the lowermost part of the upper shale member consist primarily of dark organic-rich shale, lignite, and coal that accumulated in poorly drained brackish water marshes or swamps close to the shoreline. These deposits interfinger with coastal strandplain and marine shelf deposits of the Pen Formation. The upper part of the upper shale member consists of drab fluvial flood-plain deposits, primarily olive, yellow, and gray mudstone interbedded with lenticular stream channel sandstone. These sediments accumulated in better-drained, fresh water alluvial environments some distance landward of the shoreline. Most of the diverse fossil wood assemblage thus far documented for the Aguja Formation has been recovered from the upper shale member, including a unique association of in situ tree stumps (Agujoxylon olacaceoides and Metcalfeoxylon kirtlandense) that demonstrates dicot trees as dominant canopy-forming elements in some Wheeler & Lehman — Cretaceous and Paleocene woods 295

Late Cretaceous southern latitude tropical forests (Lehman & Wheeler 2001). Fossil wood is particularly abundant in the lowermost 10 to 20 m of the upper shale member (the cupressoid/podocarpoid “acme zone” of Wheeler & Lehman 2005) where two of the woods described in the present study (GS 8 and GS 9.2) were also recovered. Ver- tebrate biostratigraphy (Rowe et al. 1992) and radiometric age determinations (Befus et al. 2008) indicate that this wood-bearing interval is middle Campanian in age.

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Figure 1. Upper Cretaceous and Paleocene stratigraphy in Big Bend National Park, southwestern Texas, showing position of Cretaceous-Tertiary (K/T) boundary, and map showing general outcrop distribution within the Park (stippled), selected measured sections (1 through 8), and positions of wood collection sites discussed in text near Gano Spring (GS 8, 9.2, and 11) and near South Dagger Flat (SDF 8). 296 IAWA Journal, Vol. 30 (3), 2009

The Javelina and Black Peaks formations also consist largely of fluvial overbank deposits. These are more brightly colored than in the Aguja Formation, with prominent beds of gray, green, purple, and red mudstone and with abundant interstitial calcium carbonate nodules. The color bands represent well-differentiated buried soil profiles (paleosols) and indicate that extended periods of soil development occurred on these well-drained alluvial flood-plains (Lehman 1989, 1990). The flood-plain deposits are interbedded with thick lenses of conglomeratic stream channel sandstone. The Creta- ceous/Tertiary boundary occurs within this succession immediately above the Javelina/ Black Peaks formational contact (Fig. 1). The lower part of the Javelina Formation preserves a diverse fossil wood assemblage, including several taxa also found in the underlying Aguja Formation (e.g., Baasoxylon parenchymatosum; Wheeler & Lehman 2000). One of the new wood types described in the present report (GS 11) was obtained from this interval. Radiometric dating of a tuff bed above this interval indicates that the lower Javelina Formation is middle Maastrichtian in age (Lehman et al. 2006). There is a reduction in the number of wood types in the upper part of the Javelina Formation, where a single type of tree – the huge dicot Javelinoxylon multiporosum (Wheeler et al. 1994) dominates. Rare araucariacean conifers also occur, and perhaps grew as isolated emergents in a tropical evergreen Javelinoxylon forest (Wheeler & Lehman 2005). The same pattern persists following the K-T boundary. A prolific fossil wood horizon (known informally as the “log jam bed”) occurs in the lower part of the Black Peaks Formation, which is dated as early Paleocene (Torrejonian) based on mammalian biostratigraphy (Lehman & Busbey 2007). Many thousands of logs are preserved in the “log jam bed” – a thin but widespread stream channel sandstone. However, of the many logs examined microscopically, all but two pertain to the same species – Paraphyllanthoxylon abbotti (Wheeler 1991). One of the woods described in the present study (SDF 8) was recovered from the “log-jam bed” and represents a unique wood type in this interval. Only rare araucariacean conifer woods have been recovered from higher in the Black Peaks (Wheeler & Lehman 2005).

MATERIALS AND METHODS

The wood specimens described were collected at sites near Gano Spring (GS) and South Dagger Flat (SDF) in Big Bend National Park, Texas. Exact locality information for these sites is on file with the specimens at the North Carolina Museum of Natural Sciences (NCMNS). All woods examined are silicified. A diamond lapidary saw was used to cut thick sections (wafers) of cross (transverse), tangential, and radial surfaces. One side of each wafer was smoothed to remove saw marks, and then affixed to a glass slide using epoxy resin. The sections were then ground until they were thin enough (c. 30–50 µm) so that anatomical details could be observed with transmitted light microscopy. Photographs were taken with an Olympus D70 digital camera that embeds scale bars in the images. The descriptions of woods given below generally conform to the IAWA Hardwood List (IAWA Committee 1989). Relationships to extant groups were investigated by using the InsideWood web site (InsideWood 2004–onwards) and references found on the Wheeler & Lehman — Cretaceous and Paleocene woods 297

Kew Micromorphology Bibliography web site. Family and order names are those used on the Angiosperm Phylogeny Website (Stevens 2001-onwards). A dot grid method was used to estimate relative percentages of cell types based on a minimum 500-point count. The samples so measured were ones in hand, well-preserved, and from trunks or logs more than 30 cm in diameter. Images were opened in Image J (Rasband 1997–2009), a grid was overlain on the image, and the dots on vessels, fibers, axial or ray parenchyma, respectively, were each counted separately.

DESCRIPTIONS Cr e t a c e o u s w o o d s Sa b i n o x y l o n Estrada-Ruiz, Martinez-Cabrera & Cevallos-Ferriz 2007 Sabinoxylon wicki sp. nov. (Fig. 2) Growth rings indistinct. Diffuse porous. Vessels predominantly solitary, oval in outline. Mean tangential diameter 84 (14) µm.; 9–11 per sq. mm. Perforation plates scalariform, most commonly 7–10 bars. Vessel-vessel or vessel-tracheid pits alternate to opposite, 5–8 µm across. Vessel-ray pits small, without reduced borders, crowded. Vessel element lengths 735–1050 µm. Axial parenchyma diffuse, diffuse in aggregates, generally 8 cells per strand. Vasicentric tracheids present. Non-septate fibers with medium-thick to thick walls, some fibers with distinctly bordered pits on both radial and tangential walls. Rays of two sizes, 1–4-seriate and more than 20 cells wide, in some regions 6 to 8 cells wide. Heterocellular, narrow rays with intermixed procumbent, square, and upright cells, wide rays with marginal rows of square and upright cells. Individual wide rays to more than 4 mm high, wide and tall rays usually in vertical series so that with a hand lens ray height appears greater. More than 12 rays per mm in regions in between wide rays. Crystals occasional in chambered upright/square ray parenchyma cells. Holotype: NCSM 1086 (GS 11). Etymology: Named for Steve Wick of Terlingua, Texas, who collected this specimen, and has assisted with our fieldwork in Big Bend. Horizon: Upper Cretaceous, Maastrichtian, Javelina Formation. Comparisons to extant plants – The combination of exclusively solitary vessels (Fig. 2A, B), scalariform perforation plates (Fig. 2C), vessel-ray parenchyma pits that do not have reduced borders (Fig. 2C), vasicentric tracheids (Fig. 2C), diffuse axial parenchyma (Fig. 2A, B), two size classes of rays (Fig. 2E, F) with the widest rays being heterocellular (Fig. 2D) and more than 10 cells wide is found in some extant species of Buxaceae (Buxales), Dilleniaceae (Dilleniales, core eudicot), Geissolomataceae (Cros- somatales, Rosid, EuRosid I), Hydrangeaceae (Cornales, Asterid), and Pentaphylacaceae (Ericales). When the occurrence of crystals in chambered ray parenchyma cells is added (Fig. 2C), that combination only occurs in species of the Pentaphylacaceae (Ericales, Asterid, Euasterid I). The Pentaphylacaceae comprises 12 genera, with three groups (Pentaphylaceae, Ternstroemieae, Frezierieae). Fossil flowers of the Ericales are known from the Cre- taceous (Schönenberger & Friis 2001). 298 IAWA Journal, Vol. 30 (3), 2009 Wheeler & Lehman — Cretaceous and Paleocene woods 299

Comparisons to fossils –This Big Bend wood fits the generic diagnosis ofSabinoxylon from the late Campanian-early Maastrichtian Olmos Formation of northern Mexico: predominantly solitary vessels, alternate to opposite pits, scalariform perforation plates with fewer than 20 bars, diffuse-in-aggregates axial parenchyma, two size classes of rays with the wider rays being more than 20 cells wide, and vasicentric tracheids (Estrada-Ruiz et al. 2007). The Big Bend wood is assigned to a new species because some of the rays in the narrow ray class are wider (up to 4 cells) than in the Olmos Formation wood (exclusively uniseriate), some fibers have bordered pits on both radial and tangential walls, and crystals occur in chambered upright ray cells. Preservation of Mexican Sabinoxylon pasac was such that vessel-ray parenchyma pits could not be observed. The Big Bend wood has vessel-ray parenchyma pits that are similar to intervessel pits. There also are quantitative differences between the Big Bend wood and the Olmos Formation wood, which has a mean vessel tangential diameter of 84 (14) µm; 3–10 vessels per sq. mm, mean vessel element length 1124 (184) µm, 7–16 bars per perforation, and ray widths to 25 cells. These types of quantitative differences can be related to differences in local growing conditions and location within the tree.

Big Bend Ericalean Wood Type I (Fig. 3) Wood diffuse porous. Vessels solitary (66%) and in short radial multiples. Solitary vessels oval to circular in outline. Mean tangential diameter 70 (13) µm, 40–97 µm; 18–20 vessels per sq. mm. Perforation plates scalariform, usually with around 20 bars. Intervessel pits crowded alternate, angular in outline, with included apertures, 4–7 µm. Vessel-ray parenchyma pits similar in size to intervessel pits, or slightly smaller. Vessel element lengths 452–904 µm. Bubble-like tyloses common in many vessel elements. Fiber walls thin to medium-thick, pits not observed. Non-septate. Diffuse axial parenchyma, strands of more than 8 cells. Rays mostly 4–6-seriate, to 8-seriate, heterocellular, with intermixed procumbent and square to upright cells in the body of the ray, and uniseriate marginal rows of a variable number of square/upright cells. Multiseriate ray height averages 888 (532) µm, range 222–2220 µm, 10–12 per mm. No crystals observed. Material: NCSM 1087 (GS 8). Horizon: Upper Cretaceous, Campanian, Aguja Formation (upper shale member). Comments – In InsideWood, modern woods that are diffuse porous with vessels solitary and in radial multiples (Fig. 3A), exclusively scalariform perforation plates (Fig. 3B, C, D), only alternate intervessel pits (Fig. 3E), vessel-ray parenchyma pits simi-

← Figure 2. Sabinoxylon wicki sp. nov. – A: Diffuse porous wood, with vessels exclusively solitary, region without wide rays, XS. – B: Solitary vessels, diffuse parenchyma, XS. – C: Scalariform perforation plates, vasicentric tracheids, vessel-ray parenchyma pits small and without reduced borders, crystals in chambered upright ray parenchyma (arrow), RLS. – D: Ray composed of procumbent, upright and square cells, RLS. – E: Rays of two sizes, TLS. – F: Rays of two sizes, narrow rays 1–3 cells wide, fibers with distinctly bordered pits on their tangential walls, TLS. — Scale bar = 200 µm in A, E, 100 µm in B, D, 50 µm in C, F. 300 IAWA Journal, Vol. 30 (3), 2009 Wheeler & Lehman — Cretaceous and Paleocene woods 301 lar to intervessel pits (Fig. 3F), diffuse axial parenchyma (Fig. 3A), and heterocellular rays (Fig. 3 I) that are more than 4 cells wide (Fig. 3G, H) are found in the Ericaceae and Styracaceae of the Ericales. Because of the resemblance of this wood to those found in the order Ericales, we refer to it here as the Big Bend Ericalean Wood Type I

Big Bend Small Axis Campanian Wood (Fig. 4) Wood diffuse porous. Vessels solitary (8%) and in short radial multiples and occasional clusters. Solitary vessels oval to circular in outline. Mean tangential diameter 49 (11) µm, range 27–69 µm; 28–52 vessels per sq. mm. Perforation plates simple. Intervessel pits crowded alternate, rounded in outline, with included apertures, small c. 5 µm. Vessel-ray parenchyma pits with reduced borders, horizontally elongated and irregular in shape. Vessel element lengths 347–448 µm. Widely spaced thin-walled tyloses present in all vessels. Fiber walls thin to medium-thick, pits not observed. Scanty paratracheal parenchyma, intermixed with vessel groups. Strands of 5–8 cells. Rays 1–3- (4-)seriate, mostly 3-seriate, heterocellular, body ray cells procumbent with 1–2 marginal rows of square/upright cells. Procumbent cells not much elongated. Multiseriate ray height averages 313 (126) µm, range 120–682 µm, 9–11 per mm. No crystals observed. Material: NCMS 1088 (GS 9.2). Horizon: Upper Cretaceous, Campanian, Aguja Formation (upper shale member). Comments – The appearance of this wood in the hand sample was such that we expected it was another example of the commonly occurring small diameter axes found at localities RM 28 and CR-2 and which we described as “Baileyan Big Bend Wood, Type I” (Wheeler & Lehman 2000). However, sections reveal that this is a different wood type. Vessel multiples are common (Fig. 4A, B), perforation plates are simple (Fig. 4E), intervessel pitting is alternate (Fig. 4D), and axial parenchyma is predominantly paratracheal (Fig. 4B). All these features distinguish this wood from the commonly occurring “Baileyan Big Bend Wood, Type I” which has predominantly solitary vessels, scalariform perforation plates, and abundant diffuse to diffuse-in-aggregates parenchyma. This sample (NCMS 1088) has pith preserved (Fig. 4C) and is a small diameter axis. Whether this sample represents a young axis of a species of tree, an erect shrub or a scandent shrub is not known. The appearance of the axes in the sediments suggests a scandent form. Ray cellular composition and width differ between juvenile wood and mature wood. The only ray characteristics that can be used to try to determine the affinities of the wood are the absence of exclusively uniseriate rays and absence of

← Figure 3. Big Bend Ericalean Wood. – A: Diffuse porous wood, with vessels solitary and rarely in radial multiples. – B: Scalariform perforation plate. – C: Multiple perforation plate. – D & E: Crowded alternate intervessel pits. – F: Vessel-ray parenchyma pits. – G & H. Multiseriate heterocellular rays, axial parenchyma strands. – I: Procumbent and square/upright cells intermixed in the ray, vessel elements with scalariform perforation plates. — Scale bar = 200 µm in A, G; 100 µm in H, I; 50 µm in B, C, D, F; 20 µm in E. 302 IAWA Journal, Vol. 30 (3), 2009 Wheeler & Lehman — Cretaceous and Paleocene woods 303 heterocellular rays (Fig. 4F) commonly more than 10-seriate (Fig. 4G). Fibers do not appear to be septate so that this is not a phyllanthoid wood type. The wood pattern of randomly arranged vessels that are solitary and in multiples, simple perforation plates and alternate pitting that is not >10 µm across, non-septate fibers without distinctly bordered pits, predominantly paratracheal parenchyma, and rays that are not exclusively uniseriate or commonly more than 10-seriate is widespread in present-day angiosperms occurring in species of at least 27 families of 12 orders of core eudicots (as defined by Stevens 2001–onwards), Sapindales (Anacardiaceae, Meliaceae, Rutaceae, Sima- roubaceae), Gentianales (Apocynaceae), Apiales (Araliaceae), Asterales (Asteraceae), Rosales (Barbeyaceae, Cannabaceae, Moraceae, Rhamnaceae), Lamiales (Bignonia- ceae, Oleaceae, Scrophulariaceae, Verbenaceae), Brassicales (Capparaceae), Mal- pighiales (Dichapetalaceae, Malpighiaceae, Euphorbiaceae, Ochnaceae, Salicaceae), Fabales (Leguminosae/Fabaceae), Myrtales (Lythraceae, Melastomataceae), Ericales (Myrsinaceae, Polemoniaceae), Solanales (Solanaceae).

Pa l e o c e n e w o o d cf. Cunonioxylon sensu Gottwald (Fig. 5) Growth rings indistinct. Wood diffuse porous. Vessels mostly solitary (87%), and in radial pairs. Vessels oval to slightly blocky in outline. Mean tangential diameter 81 (11) µm; 12–20 per sq. mm. Perforation plates exclusively scalariform, 5–12 bars, bars about 5–6 µm thick, and about 11–14 µm apart. Intervessel pitting opposite. Vessel-ray parenchyma pits horizontally elongate and with reduced borders. Widely spaced tyloses common. Axial parenchyma rare. Fibers with bordered pits on both radial and tangential walls, non-septate. Rays 1–4-seriate, mostly 2–3-seriate, predominantly of upright and square cells, with some intermixed procumbent cells, with long uniseriate margins, rays often of the interconnected type with tall alternating multiseriate and uniseriate portions, total ray height more than 1 mm, 10–14 per mm. Crystals not observed. Material: SDF 8. Horizon: Paleocene (Torrejonian), lower Black Peaks Formation. Comparisons to extant plants – The combination of vessels randomly arranged (Fig. 5A, B), exclusively scalariform perforation plates (Fig. 5C, F), opposite intervessel pits (Fig. 5E, vessel-ray parenchyma pits with reduced borders (Fig. 5D), rare axial parenchyma (Fig. 5A, B), non-septate fibers with pits on both radial and tangential walls (Fig. 5C, G), and heterocellular rays occurs in the Cunoniaceae (species of Wein-

← Figure 4. Big Bend Small Axis Campanian Wood. – A: Diffuse porous wood, with vessels solitary and in short radial multiples. – B: Vessels in short radial multiples. – C: Pith cells isodiametric, cells not very variable. – D: Crowded alternate intervessel pits. – E: Simple perforation plate. – F: Body of rays composed of procumbent cells. – G: Rays mostly 3-seriate. — Scale bar = 200 µm in A, 100 µm in B, F, 50 µm in D, E, 20 µm in C. 304 IAWA Journal, Vol. 30 (3), 2009 Wheeler & Lehman — Cretaceous and Paleocene woods 305 mannia) in the Oxalidales. Today the Cunoniaceae is a Southern Hemisphere family primarily centered in eastern Australia, New Guinea, and New Caledonia, with a few genera in southern Africa, Madagascar and the Neotropics, including Mexico (Sharp 1953; Hufford & Dickison 1992). Comparisons to fossils – Schönenberger et al. (2001) reviewed the fossil record of Cunoniaceae. The bulk of the records are from the Southern Hemisphere, including a Cretaceous wood from Antarctica, Weinmannioxylon nordenskjoeldii (Poole et al. 2000). The genus Weinmannioxylon Petriella was diagnosed as having axial parenchyma diffuse or grouped in small tangential bands (translated diagnosis seen in Poole et al. 2000a), features not seen in this Big Bend wood. There are a few Northern Hemi- sphere fossils assigned to the Cunoniaceae, e.g., flowers from the Late Cretaceous (late Santonian–early Campanian) of Sweden (Schönenberger et al. 2001) and two European fossil woods: Cunonioxylon weinmannioxylon from the Oligocene of Bavaria (Hofmann 1952) and C. parenchymatosum from the Eocene of Germany (Gottwald 1992). Gottwald (1992) noted that the diagnosis of Cunonioxylon Hofmann was such that it was somewhat questionable whether the wood was related to Cunoniaceae. Hof- mann seems to have relied on the cross-sectional appearance of the Bavarian wood as the basis for assigning it to the Cunoniaceae. However, her generic diagnosis only mentions simple perforations (“Gefassdurchbrechung einfach”), not scalariform. Gottwald described the Eocene Cunonioxylon as having scalariform perforation plates with 15–40 bars and agreeing in all details with Cunonia. Evidently, as the wood resembled Cunonia, it was assigned to Cunonioxylon, although it does not conform to Hofmann’s diagnosis. Although the Big Bend wood has features seen in Cunoniaceae, we are not assigning it to Cunonioxylon because the genus diagnosis mentions simple perforations (“Gefassdurchbrechung einfach”) and axial parenchyma frequently in uniseriate rows, features not seen in the Big Bend wood.

DISCUSSION

Regional Late Cretaceous vegetation — The presence of Sabinoxylon at Big Bend provides additional evidence for similarity in Campanian-Maastrichtian woody vegetation of Texas, New Mexico and Mexico. Metcalfeoxylon occurs in the Campanian Aguja Formation of Big Bend (Wheeler & Lehman 2000), Kirtland Formation in the San Juan Basin, New Mexico (Wheeler et al. 1995; Hudson 2006), and Crevasse Canyon Formation of south-central New Mexico (Upchurch et al. 2003). This genus occurs as in situ stumps at sites in both Big Bend (Lehman & Wheeler 2001) and New Mexico (Upchurch et al. 2003). Baasoxylon occurs in the upper Campanian-lower

← Figure 5. cf. Cunonioxylon sensu Gottwald. – A: Diffuse porous wood, with vessels predominantly solitary, radial multiples rare. – B: Solitary vessels slightly angular in outline, fibers with thin walls. – C: Scalariform perforation plate with thick, widely spaced bars. – D: Vessel-ray parenchyma pits with reduced borders and horizontally elongate. – E: Opposite pits. – F: Vessels with widely spaced tyloses. – G: Rays mostly 3 cells wide, with long uniseriate portions, some fibers with pits on tangential walls. — Scale bar = 200 µm in A, 100 µm in B, F, G, 50 µm in C, D, E. 306 IAWA Journal, Vol. 30 (3), 2009

Maastrichtian of Big Bend (Wheeler & Lehman 2000) and the San Juan Basin (Hud- son 2006). Javelinoxylon, the most common wood in the Maastrichtian of Big Bend (Wheeler et al. 1994), also occurs in the Maastrichtian of Mexico (Estrada-Ruiz et al. 2007). Collectively, these occurrences support the belief that the Late Cretaceous southern latitude flora of North America shared common elements, and differed from the northern latitude flora (Wheeler & Lehman 2005).

Characteristics of Northern Hemisphere Cretaceous woods — All the Big Bend Cretaceous woods are diffuse porous and lack elaborate paratracheal parenchyma and any type of banded parenchyma. The three new types of Cretaceous woods are variations on themes of commonly occurring Cretaceous woods; one has predominantly solitary vessels, scalariform perforation plates and wide rays (features also found in Icacinoxylon), the other two have vessels solitary and in radial multiples, simple perforation plates and alternate pits (features also found in Paraphyllanthoxylon). Features of Paraphyllanthoxylon and Icacinoxylon and incidences of selected features in Cretaceous woods are discussed in more detail below.

Paraphyllanthoxylon vs. Icacinoxylon/Plataninium – The earliest known dicotyledonous woods with reliable provenance represent two distinct wood anatomical types, the phyllanthoid type and the icacinoid/platanoid type (Cedar Mt. Formation, Albian age, Utah, USA, Thayn et al. 1983, 1985). These two wood types are common throughout the Cretaceous, accounting for more than half of the records to date. The general pattern of these two wood types occurs today in a number of dicotyledonous families and orders; both patterns occur in the Eumagnoliids and the Eudicots. Paraphyllanthoxylon is the more abundant of the two wood types, with large logs, some more than 1 meter in diameter known from the Cenomanian of Alabama (Cahoon 1972) and Arizona (Bailey 1924). According to Bailey (1924) at the P. arizonense locality “fossil wood was fairly abundant … Some of the trunks are more than a foot in diameter.” Jack Wolfe and one of the authors (EW) visited the Mogollon Rim region to look for Bailey’s locality, a “barrow pit” in Show Low, Arizona. We easily found more than 20 logs, behind the barrow pit (now a rodeo ring) and exposed along road cuts in the area; most were more than 60 cm in diameter. The anatomy of all these Mogollon Rim logs is that of Paraphyllanthoxylon arizonense. Paraphyllanthoxylon also occurs in the Albian of Utah (Thayn et al. 1983), Idaho (Spackman 1948) and Texas (Serlin 1982; Wheeler 1991). These Albian and Cenomanian Paraphyllanthoxylon species have vessels that would be considered efficient in water conduction, as they are wide and composed of elements with simple perforation plates. Characteristics of phyllanthoid wood include vessels solitary and in radial multiples, simple perforation plates, alternate intervessel pitting, vessel-ray parenchyma pits with reduced borders, axial parenchyma rare to scanty paratracheal, septate fibers that lack distinctly bordered pits, heterocellular multiseriate rays, and absence of storied structure. This combination of features occurs in Lauraceae, Burseraceae, Anacardiaceae, Salicaceae, and Phyllanthaceae. Herendeen (1991b) found attachment between an axis with anatomy of Paraphyllanthoxylon and Wheeler & Lehman — Cretaceous and Paleocene woods 307 a fruit of Lauraceae, demonstrating that at least one species of Paraphyllanthoxylon is Lauraceae. However, it is unlikely that all species assigned to this genus are Lauraceae, particularly those that have markedly heterocellular rays, which are likely to be Sali- caceae or Phyllanthaceae. There are Cretaceous localities with mesofossils where the opportunity exists for finding attachment between plant parts and allow determining the affinities of these woods. These early phyllanthoid woods are “problematic” in the way the “Stopes woods” were (whose age is not yet settled), i.e., they have “advanced” wood structure, see Stopes & Fujii 1910; Stopes 1912, 1915). Characteristics of Icacinoxylon include exclusively to predominantly solitary vessels, scalariform perforation plates, wide (more than 4-seriate to 10 or more cells wide) and tall rays (>1 mm high). This combination of characters occurs in a number of eudicot orders: Crossomatales (Aphloiaceae and Staphyleaceae), Berberidopsidales (Ber- beridopsidaceae), Aquifoliales (Cardiopteridaceae, Helwingiaceae), Apiales (Pennan- tiaceae, Griseliniaceae), Asterales (Rousseaceae), Dilleniales (Dilleniaceae), Ericales (Ericaceae), Ranunculales (Eupteleaceae, Lardizabalaceae), Cornales (Hydrangeaceae), as well as in the Icacinaceae (unplaced as to order, but near Garryales). There is considerable variation within Icacinoxylon; e.g., there are species with septate fibers and species with only non-septate fibers. As Herendeen (1991a) pointed out, a review of woods assigned to Icacinoxylon is needed. Woods assigned to Plataninium or Platanoxylon usually have some vessel multiples and rays tend to be or are homocellular (e.g., Page 1968; Wheeler et al. 1995; Takahashi & Suzuki 2003). Icacinoxylon and Paraphyllanthoxylon antedate the earliest pollen and mesofossil record of angiosperms by tens of millions of years. It is puzzling that two such different wood patterns share the distinction of being the earliest confirmed dicot wood types. This might imply multiple origins of vessel elements within the angiosperms, once with simple perforation plates, once with scalariform perforation plates, or could instead reflect a change that occurred in vessel structure from a single origin. These Albian-Cenomanian woods do not shed light on the stature of the earliest angiosperms, but do indicate that dicot trees were an important element in some ecosystems by the Cenomanian. On the basis of a bibliographic survey and new collections of Berriasian- Cenomanian woods of Europe, Philippe et al. (2008) suggest that early angiosperms were small statured and had physically weak wood; large fossil angiosperm trunks are absent from the European Albian-Cenomanian and the abundance of angiosperm wood is greater in Cenomanian strata. Cantrill and Poole (2005) found comparable results for Antarctic fossil wood assemblages; pre-Cenomanian beds did not contain angiosperms. Another example of change in Albian-Cenomanian abundance and diversity of angiosperm woods is provided by Takahashi and Suzuki (2003). Two (4%) of their 54 Albian wood samples are angiosperms (Icacinoxylon), while 7 (31%) of 33 Cenomanian wood samples are angiosperms (Icacinoxylon, Paraphyllanthoxylon, Plataninium, and Hamamelidoxylon).

Comparison of Cretaceous Dicot Woods to Modern Dicot Woods — For purpose of the following comparison, we divided the Northern Hemisphere Cretaceous wood records into three time bins; Albian-Cenomanian (16 records) when angiosperm woods first 308 IAWA Journal, Vol. 30 (3), 2009 occur and when other types of fossils show a dramatic increase in angiosperm diversity (Crane 1987; Butler et al. 2009); Turonian-Santonian (50 records), and Campanian- Maastrichtian (134 records). These intervals are similar to those discussed by Butler et al. in their study of diversity patterns among herbivorous dinosaurs and plants. Each published report of a fossil wood species or type was treated as a different record; some ‘species’ have more than one record because that ‘species’ was described from more than one locality or age; for example, Paraphyllanthoxylon arizonense was described from

% Porosity % Mean tangential diameter (µm) 100 100 > 200 90 90 100–200 80 80 RP 50–100 70 70 < 50 60 60 SRP 50 50 40 40 DP 30 30 20 20 10 10 0 0 A K1 K2 K3 Recent B K1 K2 K3 Recent

% Exclusively solitary vessels % Radial arrangement of vessels 50 25 45 40 20 35 30 15 25 20 10 15 10 5 5 0 0 C K1 K2 K3 Recent D K1 K2 K3 Recent

Vessel clusters common % Perforation plates 100

% 90 Scal 25 80 Simp 70 20 60

15 50 40 10 30 20 5 10 0 0 E K1 K2 K3 Recent F K1 K2 K3 Recent Figure 6. Incidences (percentage occurrence) of wood anatomical features in the Cretaceous: Albian-Cenomanian (K1), Turonian-Santonian (K2), Campanian-Maastrichtian (K3), and Recent (R) flora worldwide. Thin lines above bars of graph = one standard deviation. – A: Porosity. RP = ring porous, SRP = semi-ring porous, DP = diffuse porous. – B: Mean vessel tangential diameter by IAWA category. – C: Exclusively solitary vessels. – D: Radial arrangement of vessels. – E: Vessel clusters common. – F: Perforation plates. – Scal = scalariform perforation plates, Simp = simple perforation plates. Wheeler & Lehman — Cretaceous and Paleocene woods 309 the Cenomanian of Arizona (Bailey 1924) and the late Campanian-early Maastrichtian of New Mexico (Wheeler et al. 1995; Hudson 2006). Appendix I contains the sources for these Cretaceous records, Appendix II the sources for Paleocene woods, excluding those references cited in the text and given in the reference section. Most of the Albian and Cenomanian woods from Europe reported by Philippe et al. (2008) have not yet been described in detail, and so these woods are not included in this survey. The incidence of selected wood anatomical features is reported here as a percentage. The base numbers on which the percentages for the three divisions of the Cretaceous and the Recent flora are given above, but with some differences by feature as some descriptions did not provide information on all of the features surveyed. The standard deviations for the percentages are based on the formula of Steel and Torrie (Steel et al. 1997): estimated SD = square root of [p (1-p) / n], where p = percentage/100 and n = number of counts for that feature. Because of the small sample size for Albian-Cenomanian woods, and resultant large standard deviations it is difficult to establish that there are any statistically significant differences between woods of that time interval and the Santonian-Turonian or the Campanian-Maastrichtian. Porosity (Fig. 6A) – Diffuse porous woods dominate throughout Cretaceous time, as they do in the Recent flora. Ring porous woods are not common even in the extant flora, and are primarily a Recent north temperate phenomenon (Gilbert 1940; Wheeler et al. 2007). The few ring porous woods from the latest Cretaceous are from high latitudes in both Southern (Poole et al. 2000b) and Northern Hemispheres (Takahashi & Suzuki 2003). Ring porosity is correlated with deciduousness (Boura & De Franceschi 2007). The low incidence of ring porous woods in the latest Cretaceous supports Wolfe’s (1987) analysis that the terminal Cretaceous event was important for the spread and diversification of deciduous taxa. Vessel diameters (Fig. 6B) – Today diffuse porous woods with uniform vessel diameters and mean tangential diameters of more than 200 µm occur only in trees (Wheeler et al. 2007); such woods occur predominantly in the wet tropics. Although most Creta- ceous woods have vessel diameters of <100 µm, woods with wider diameters do occur and are consistent with some being large trees, particularly phyllanthoid types from the Albian-Cenomanian (Bailey 1924; Cahoon 1972; Serlin 1982). In the Recent flora there are higher proportions of both very wide and very narrow vessels, as would be expected with dicots expanding from Cretaceous time into a wider range of habitats, from arid to arctic (favoring narrow vessels) and development of the multistratal forests of the wet tropical lowlands during the Tertiary. Vessel groupings and arrangement (Fig. 6C, D, E) – Consistent with earlier studies of the incidence of dicot wood features through time (Wheeler & Baas 1991, 1993), exclusively solitary vessels are more common in the Cretaceous than at present. Non- random vessel arrangements, for example, radial to diagonal arrangement of vessels and vessel clusters, gradually increased in abundance toward the end of Cretaceous time, but remained rare compared to Recent time. Perforation plates (Fig. 6F) – The most striking difference between woods of the Cretaceous and Recent is the high incidence of scalariform perforation plates during the 310 IAWA Journal, Vol. 30 (3), 2009

Cretaceous (more than 50%). It is somewhat surprising that this is the case, as simple perforations occur in the earliest dicot woods (species of Paraphyllanthoxylon) and dominate in the Recent flora. However, here we count reports of wood types, not their relative abundance. At the localities where Paraphyllanthoxylon occurs it is very common (Bailey 1924; Cahoon 1972; Hudson 2006; Oakley & Falcon-Lang 2008), and so one could hypothesize that during the Cretaceous trees with simple perforation plates accounted for more biomass and were more successful than those with scalariform perforation plates. Axial parenchyma (Fig. 7A, B) – The incidence of marginal parenchyma is markedly higher in the Recent flora than in the Cretaceous, most likely indicating a lower incidence of seasonal climates and cambial dormancy in the Cretaceous. Although correlations of marginal parenchyma occurrence with cambial dormancy and deciduousness have not been investigated to the same extent as correlation between ring porosity and de-

Apotracheal parenchyma Paratracheal parenchyma % % 100 100 Dif ScP 90 90 Dif-A Vc 80 80 Marg Alf 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 A B Ray cellular composition Ray width classes % % 100 50

90 45

80 40

70 35

60 30

50 25

40 20

30 15

20 10

10 5

0 0

C Homocellular Heterocellular D 1 1-3 4-10 >10 Figure 7. Incidences (percentage occurrence) of wood anatomical features in the Cretaceous: Albian-Cenomanian (K1), Turonian-Santonian (K2), Campanian-Maastrichtian (K3), and Recent (R) flora worldwide. Thin lines above bars of graph = one standard deviation. – A: Apotracheal parenchyma. Dif = diffuse, Dif-A = diffuse-in-aggregates, Marg = marginal. – B: Paratracheal parenchyma. ScP = scanty paratracheal, Vc = vasicentric, Alf = aliform. – C: Ray cellular composition. Homocellular = rays composed of procumbent cells, heterocellular = rays with both procumbent and upright/square cells. – D: Ray width classes. 1 = exclusively uniseriate, 1–3 = rays 1 to 3 cells wide, 4–10 = wider rays commonly reach 4 to 10 cells wide, >10 = wider rays commonly reach more than 10 cells wide. Wheeler & Lehman — Cretaceous and Paleocene woods 311 ciduousness (Boura & De Franceschi 2007), presumably they are correlated, but this needs to be investigated. Aliform axial parenchyma is much rarer in the Cretaceous than in the Recent flora (Fig. 7B). Ray parenchyma (Fig. 7C, D) – Heterocellular rays have always been more common than homocellular rays. The differences between ray widths in the Cretaceous and Recent flora are at the extremes, with uniseriate rays more common in the Recent flora than in the Cretaceous, and wide rays more common in the Cretaceous than at present. The higher incidence of wide rays in the Cretaceous reflects the common occurrence of woods of the Icacinoxylon or Platanus-type in the Cretaceous. Storage tissue in Cretaceous trees – Some Cretaceous dicot woods with trunk diameters of more than 50 cm have a high percentage of storage cells (Table 1). The most commonly occurring Cretaceous wood, Paraphyllanthoxylon, lacks axial parenchyma but its ground tissue is comprised of septate fibers, which in extant plants function as storage cells. The Cenomanian P. arizonense from the Mogollon Rim of Arizona (Bailey 1924) and the Maastrichtian P. illinoisense from the McNairy Formation of Illinois (Wheeler et al. 1987) are comprised of more than 75% storage cells. The other common tree type in the McNairy Formation (Parabombacaceoxylon magniporosum) has more than 40% parenchyma. Parenchyma percentages for Big Bend Cretaceous trees are between 40 and 60% (Table 1).

Table 1. Percentage of ray parenchyma (RP), axial parenchyma (AP), and septate fibers (SpFib) and total (TOT) percentage of storage tissue in selected Cretaceous trees from the U.S.A. — Ab = absent; ? = cell type present, but not able to determine percentage; M = Maastrichtian, Cmp = Campanian; Cen = Cenomanian.

Species Age Max RW % RP % AP % SpFib. TOT

Big Bend Ericalean Wood Cmp 6 41 ? Ab 41+ GS 8

Sabinoxylon wicki M 20 + 38 ? Ab 38 + Paraphyllanthoxylon illinoisense M 6 39 Ab 46 85 SIPC 622. 155

Parabombaceoxylon magniporosum M 2 (3) 26 17 Ab 43 SIPC 608.18, SIPC 611.20

Metcalfeoxylon kirtlandense Cmp-M 4 37 14 Ab 51 USNM 507055 (EDF 2A)

Baasoxylon parenchymatosum Cmp-M 8 55 ? Ab 55 + USNM 507057 (PGH 4a)

Agujoxylon olacaceioides Cmp-M 6 34 10 Ab 44 USNM 507039, 507042

Paraphyllanthoxylon arizonense Cen 6 33 Ab 47 80 312 IAWA Journal, Vol. 30 (3), 2009

The consequences or advantages (if any) of such high proportions of living cells for Cretaceous angiosperm trees are therefore topics of interest. Living cells function in storage, for both starch and water (Holbrook 1995). Large amounts of parenchyma with stored food material might aid in rapidly replacing cropped foliage, and be valuable for wound response, an ability that could be useful in environments characterized by large dinosaurian herbivores. Abundant parenchyma might also affect the ability of a tree to stump sprout if it were subject to being toppled by large herbivores. High proportions of storage cells in these Late Cretaceous trees might result in a condition somewhat analogous to that found in stem succulents. Buried calcareous soil profiles in Cretaceous wood-bearing deposits (e.g., Lehman 1989, 1990) indicate that at least some of these trees inhabited semi-arid environments. Periods of low water availability in Cretaceous environments could have made stored water useful, and large amounts of stored water might inhibit the production of growth rings, as water would be available year round and cambial activity might not reflect fluctuations in external water availability. In Cretaceous deposits, conifer woods with distinct growth rings co-occur with dicots lacking distinct growth rings (Wheeler & Lehman 2005). Cretaceous angiosperms could have used stored water to avoid water deficits, thus bypassing seasonal effects, or in contrast, conifer species may have been genetically stimulated to produce growth rings even when seasonality was not pronounced. High proportions of ray parenchyma would also be expected to have mechanical consequences. Relationships between wood anatomical features and physical properties are complex. Parenchyma cell walls are different from fiber and vessel element walls. Ray parenchyma is horizontally oriented, while fibers and vessels are vertically oriented. A study of 12 north temperate species found that ray volume affected modulus of elasticity (MOE) in the radial direction of the wood (Burgert et al. 2001). Studies of the properties of isolated rays indicate that rays affect the radial stiffness of wood (Kawamura 1984; Badel & Perré 1999). Greater radial stiffness could have been advan- tageous for resisting toppling by large dinosaurian herbivores of the Cretaceous or by strong storms that are likely to have occurred along the margins of inland Cretaceous seas (Wheeler & Lehman 2005). There may be correlations between high proportions of ray parenchyma and tree architecture because of the mechanical consequences of high proportions of parenchyma. Studies to measure ray parenchyma proportions in different tree architectural types could test whether any such relationships exist. There are experimental data that indicate that “primitive” vessel elements did not confer a hydraulic advantage relative to tracheids (Sperry et al. 2007). The wider diameters of the vessel elements made them more vulnerable to cavitation than tracheids, so that initially angiosperms with vessels would likely have been confined to wet habitats (Feild et al. 2004; Feild & Arens 2005, 2007). Sperry et al. (2007) suggest that diversification of cell types, not the development of vesselsper se would have contributed to the success of the angiosperms. Certainly dicots show considerable diversification in cell types and arrangements, not only in vessel features, but also in parenchyma cells involved in storage and production of secondary metabolites and wound response. Changes in secondary xylem differentiation that led to variation in parenchyma abundance and arrangement must also have been important in contributing to the success of the angiosperms and their variety in architecture. Wheeler & Lehman — Cretaceous and Paleocene woods 313

Paleocene Woods – The bulk of the Paleocene woods at Big Bend are referable to Paraphyllanthoxylon abbotti, mostly from an extensive layer of logs of this species. The cf. Cunonioxylon wood type described in this paper and a Platanus-like wood (cf. Platanoxylon haydenii, Wheeler 1991) are very rare in the same deposits; each is rep- resented by only one sample. Similarly, Paraphyllanthoxylon arizonense dominates an extensive log zone in the Paleocene of New Mexico (Ojo Alamo Sandstone; Wheeler et al. 1995). There are fewer anatomically described fossil dicot woods known from the Paleocene than for any other epoch of the Tertiary; in 1993, there were 36 records total for the entire world (Wheeler & Baas 1993), today there are 71 (InsideWood, accessed 31 December 2008). These low numbers could reflect a dramatic reduction in diversity of wood types that accompanied the terminal Cretaceous extinction event, or the general rarity of continental deposits of Paleocene age from varied latitudes worldwide. Features that change noticeably in incidence from the Campanian-Maastrichtian to Paleocene are distinct growth rings (increases to 29%), exclusively scalariform perforation plates (decreases to 37 %), mean tangential diameter >200 µm (increases to 7%).

CONCLUSIONS

The three new Cretaceous woods from Big Bend have features consistent with patterns seen in other Cretaceous dicot woods. Sabinoxylon wicki provides additional evidence indicating that the Late Cretaceous floras of Texas, New Mexico, and northern Mexico were similar. Cretaceous woods as a whole differ from Recent woods in the incidences of vessel and parenchyma features. The high incidence of scalariform perforation plates in Cretaceous woods is especially striking. The high proportions of storage cells in Creta- ceous dicot woods raises questions about the functional significance of variations in ray and axial parenchyma and septate fiber abundance. There remains much to be learned about Cretaceous angiosperm woods and any additional collections of wood from any interval of the Cretaceous would be important for understanding their past diversity.

ACKNOWLEDGMENTS

We thank the Science and Resource Management staff of Big Bend National Park, in particular D. Corrick and V. Davila, for granting collecting permits for our research and for their continued assist- ance with paleobotanical work in the Park. J. Browning prepared thin-sections of our wood samples. This work was in part supported by NSF Grants BRC 0237368 and DBI/BDI 0518386 to N.C. State University for work on databases for fossil and Recent dicot wood. Thanks are also due to the NCSU libraries administration for their support, and to the interlibrary loan services of the NCSU libraries.

REFERENCES

Badel, E. & P. Perré. 1999. Détermination des propriétés élastiques d’éléments individuels du plan ligneux du chêne par des essais de traction sur micro-éprouvettes. Ann. For. Sci. 56: 467–478. Bailey, I.W. 1924. The problem of identifying the wood of Cretaceous and later dicotyledons. Paraphyllanthoxylon arizonense. Ann. Bot. 38: 439–451. 314 IAWA Journal, Vol. 30 (3), 2009

Befus, K.S., R.E. Hanson, T.M. Lehman & W.R. Griffin. 2008. Cretaceous basaltic phreatomag- matic volcanism in West Texas: maar complex at Pena Mountain, Big Bend National Park. J. Volcanology and Geothermal Res. 173: 245–264. Boura, A. & D. De Franceschi. 2007. Is porous wood structure exclusive of deciduous trees? C. R. Palevol 6: 385–391. Burgert, I., A. Bernasconi, K.J. Niklas & D. Eckstein. 2001. The influence of rays on the transverse elastic anisotropy of deciduous trees. Holzforschung 55: 449–454. Butler, R.J., P.M. Barrett, P. Kenrick & M.G. Penn. 2009. Diversity patterns among herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/ angiosperm co-evolution. J. Evolutionary Biology 22: 446–459. Cahoon, E.J. 1972. Paraphyllanthoxylon alabamense – a new species of fossil dicotyledonous wood. Amer. J. Bot. 59: 5–11. Cantrill, D. & I. Poole. 2005. Taxonomic turnover and abundance in Cretaceous to Tertiary wood floras of Antarctica. Palaeogeography, Palaeoclimatology, Palaeoecology 215: 205–219. Crane, P.R. 1987. Vegetational consequences of the angiosperm diversification. In: E.M. Friis, W.G. Chaloner & P.R. Crane (eds.), The origin of angiosperms and their biological consequences: 107–144. Cambridge University Press, Cambridge. Estrada-Ruiz, E., H.I. Martinez-Cabrera & S.R.S. Cevallos-Ferriz. 2007. Fossil woods from the late Campanian-early Maastrichtian Olmos Formation, Coahuila, Mexico. Review of Palaeobotany and Palynology 145: 123–133. Feild, T.S. & N.C. Arens. 2005. Form, function, and environments of the early angiosperms: merg- ing extant phylogeny and ecophysiology with fossils. New Phytologist 166: 383–408. Feild, T.S. & N.C. Arens. 2007. The ecophysiology of early angiosperms. Plant, Cell and En- vironment 30: 291–309. Feild, T.S., N.C. Arens, J.A. Doyle, T.E. Dawson & M.J. Donoghue. 2004. Dark and disturbed: a new image of early angiosperm ecology. Paleobiology 30: 82–107. Gilbert, S.G. 1940. Evolutionary significance of ring porosity. Bot. Gaz. 102 (1): 105–120. Gottwald, H. 1992. Hölzer aus Marinen Sanden des Oberen Eozän von Helmstedt (Niedersach- sen). Palaeontographica B 225: 27–103. Herendeen, P.S. 1991a. Charcoalified angiosperm wood from the Cretaceous of eastern North America and Europe. Review of Palaeobotany and Palynology 69: 225–239. Herendeen, P.S. 1991b. Lauraceous wood from the mid-Cretaceous Potomac Group of eastern North America: Paraphyllanthoxylon marylandense sp. nov. Review of Palaeobotany and Palynology 69: 277–290. Hofmann, E. 1952. Pflanzenreste aus dem Phosphoritvorkommen von Prambachkirchen in Ober- österreich. Palaeontographica 92B: 122–183. Holbrook, N. M. 1995. Stem water storage. In: B.L. Gartner (ed.), Plant stems. Physiology and functional morphology: 151–174. Academic Press, San Diego. Hudson, P. J. 2006. Taxonomic and paleoclimatic significance of Late Cretaceous wood from the San Juan Basin, New Mexico. Unpub. M.S. Thesis, University of Nebraska Omaha. 82 pp. Hufford, L. & W.C. Dickison. 1992. A phylogenetic analysis of Cunoniaceae. Systematic Botany 17: 181–200. IAWA Committee. 1989. IAWA list of microscopic features for hardwood identification. IAWA Bull. n.s. 10: 219–332. InsideWood. 2004–onwards. Published on the Internet. http://insidewood/lib.ncsu.edu/search Kawamura, Y. 1984. Studies on the properties of rays (II). Mean micelle angles and physical properties of broad rays. Mokuzai Gakkaishi 30: 201–206. Lehman, T.M. 1989. Upper Cretaceous (Maastrichtian) paleosols in Trans-Pecos Texas. GSA Bull. 101: 188–203. Wheeler & Lehman — Cretaceous and Paleocene woods 315

Lehman, T.M. 1990. Paleosols and the Cretaceous/Tertiary transition in the Big Bend region of Texas. Geology 18: 362–364. Lehman, T.M. & A.B. Busbey. 2007. Big Bend Field Trip Guidebook. Society of Vertebrate Paleontology, 67th Annual Meeting, Field Trip Guidebook. 69 pp. Lehman, T.M., F. McDowell, & J. Connelly. 2006. First isotopic (U-Pb) age for the Late Creta- ceous Alamosaurus vertebrate fauna of West Texas, and its significance as a link between two faunal provinces. J. Vertebrate Paleontology 26: 922–928. Lehman, T.M. & E.A. Wheeler. 2001. Fossil dicotyledonous forest from the Upper Cretaceous of Big Bend National Park, Texas. Palaios 16: 102–108. Oakley, D. & H.J. Falcon-Lang. 2008. Morphometric analysis of Cretaceous (Cenomanian) angiosperm woods from the Czech Republic. Review of Palaeobotany and Palynology 153: 375–385. Page, V.M. 1968. Angiosperm wood from the Upper Cretaceous of central California: II. Amer. J. Bot. 55: 168–172. Philippe, M., B. Gomez, V. Girard, C. Coiffard, V. Daviero-Gomez, F. Thevenard, J-P. Billon- Bruyat, M. Guiomar, J-L. Latil, J. Le loeuff, D. Néraudeau, D. Olivero & J. Schlögl. 2008. Woody or not woody? Evidence for early angiosperm habit from the Early Cretaceous fossil wood record of Europe. Palaeoworld 17: 142–152. Poole, I., D.J. Cantrill, P. Hayes & J.E. Francis. 2000a. The fossil record of Cunoniaceae: new evidence from Late Cretaceous wood of Antarctica. Rev. Palaeobot. Palynol. 111: 127–144. Poole, I., H.G. Richter & J.E. Francis. 2000b. Evidence for Gondwanan origins for Sassafras (Lauraceae)? Late Cretaceous fossil wood of Antarctica. IAWA J. 21: 463–475. Rasband, W.S. ImageJ, U.S. National Institutes of Health, Bethesda, Maryland, USA, http:// rsb.info.nih.gov/ij/, 1997–2009. Rowe, T.R., L. Ciflli, T.M. Lehman & A. Weil. 1992. The Campanian Terlingua local fauna, with a summary of other vertebrates from the Aguja Formation, Trans-Pecos Texas. J. Vert. Paleontol. 12: 472–493. Schönenberger, J. & E.M. Friis. 2001. Fossil flowers of ericalean affinities from the Late Cre- taceous of southern Sweden. Amer. J. Bot. 88: 467–480. Schönenberger, J., E.M. Friis, M.L. Mathews & P.K. Endress. 2001. Cunoniaceae in the Creta- ceous of Europe. Evidence from fossil flowers. Annals of Botany 88: 423–437. Serlin, B.S. 1982. An Early Cretaceous fossil flora from Northwest Texas: Its composition and implications. Palaeontographica 182B: 52–86. Sharp, A.J. 1953. Notes on the flora of Mexico: world distribution of the woody dicotyledonous families and the origin of the modern vegetation. J. Ecology 41: 374–380. Spackman, W., Jr. 1948. A dicotyledonous wood found associated with the Idaho Tempskyas. Ann. Missouri Bot. Gard. 35: 107–116. Sperry, J.S., U.G. Hacke, T.S. Feild, Y. Sano & E.H. Sikkema. 2007. Hydraulic consequences of vessel evolution in angiosperms. Int. J. Plant Sci. 168 (8): 1127–1139. Steel, R.G.D., J.H. Torrie & D.A. Dickey. 1997. Principles and procedures of statistics. A bio- metrical approach. Ed. 3. McGraw-Hill, New York. Stevens, P.F. 2001-onwards. Angiosperm Phylogeny Website. Version 9, June 2008. Stopes, M.C. 1912. Petrifactions of the earliest European angiosperms. Phil. Trans. Roy. Soc. London B 203: 75–100 + pl. 6–8. Stopes, M.C. 1915. Catalogues of Mesozoic plants in the Natural History Museum. The Creta- ceous flora. Part 2. Lower Greensand (Aptian) plants of Britain. British Museum (Natural History), London. 360 pp. + 32 pl. Stopes, M.C. & K. Fujii. 1910. Studies on the structure and affinities of Cretaceous plants. Phil. Trans. Roy. Soc. London B 201: 1–90 + 9 pl. 316 IAWA Journal, Vol. 30 (3), 2009

Takahashi, K. & M. Suzuki. 2003. Dicotyledonous fossil wood flora and early evolution of wood characters in the Cretaceous of Hokkaido, Japan. IAWA J. 24: 269–309. Thayn, G.F., W.D. Tidwell & W.L. Stokes. 1983. Flora of the Lower Cretaceous Cedar Moun- tain Formation of Utah and Colorado. Part I. Paraphyllanthoxylon utahense. Great Basin Naturalist 43: 394–402. Thayn, G.F., W.D. Tidwell & W.L. Stokes. 1985. Flora of the Lower Cretaceous Cedar Moun- tain Formation of Utah and Colorado. Part III. Icacinoxylon pittiense n. sp. Amer. J. Bot. 72: 175–180. Upchurch, G.R., G.H. Mack & E.A. Wheeler. 2003. Late Cretaceous fossil forests from south- central New Mexico. Abstracts Botany 2003, Mobile, Alabama, p. 67. Wheeler, E.A. 1991. Paleocene dicotyledonous trees from Big Bend National Park, Texas: Variability in wood types common in the Late Cretaceous and Early Tertiary, and ecological inferences. Amer. J. Bot. 78: 658–671. Wheeler E.A. & P. Baas. 1991. A survey of the fossil record for dicotyledonous wood and its significance for evolutionary and ecological wood anatomy. IAWA Bull. n.s. 12: 271–332. Wheeler E.A. & P. Baas. 1993. The potentials and limitations of dicotyledonous wood anatomy for climatic reconstructions. Paleobiology 19: 486–497. Wheeler, E.A., P. Baas & S. Rodgers. 2007. Variations in dicot wood anatomy. A global analysis. IAWA J. 28: 229–258. Wheeler, E.A., M. Lee & L.C. Matten. 1987. Dicotyledonous woods from the Upper Cretaceous of southern Illinois. Bot. J. Linn. Soc. 95: 77–100. Wheeler, E.A. & T.M. Lehman. 2000. Late Cretaceous woody dicots from the Aguja and Javelina Formations, Big Bend National Park, Texas. IAWA J. 21: 83–120. Wheeler, E.A. & T.M. Lehman. 2005. Cretaceous-Paleocene conifer woods from Big Bend National Park, Texas. Palaeogeography, Palaeoclimatology, Palaeoecology 226: 233–258. Wheeler, E.A., T.M. Lehman & P. Gasson. 1994. Javelinoxylon, a new genus of malvalean tree from the Upper Cretaceous of Big Bend National Park, Texas. Amer. J. Bot. 81: 703–710. Wheeler, E.A., J. McClammer & C.A. LaPasha. 1995. Similarities and differences in dicotyledonous woods of the Cretaceous and Paleocene of San Juan Basin, New Mexico, USA. IAWA J. 16: 223–254. Wolfe, J.A. 1987. Late Cretaceous-Cenozoic history of deciduousness. Paleobiology 13: 215–226.

APPENDIX I — REFERENCES FOR INCIDENCES OF CRETACEOUS WOODS

Cevallos-Ferriz, S. 1983. Descripción de una madera de angiosperma Cretácica de Cananea, Son., Méx., los xilitos en el estudio del origen de las Angiospermopsida. Anal. Inst. Biol. Univ. Nal. Autón. México, Ser. Bótanica 54: 97–112. Cevallos-Ferriz, S.R.S. & R. Weber. 1992. Dicot from Upper Cretaceous of Coahuila. Revista UNAM Inst. Geol. 10: 65–70. Crawley, M. 2001. Angiosperm woods from British Lower Cretaceous and Palaeogene Deposits. Special Papers in Palaentology 66. The Palaeontological Association. 100 pp. Gottwald, H. 2000. Gymnosperme und dicotyle Hölzer (67) aus den “Aachener Sanden” der Obe- ren Kreide von NO-Belgien und NW-Deutschland. Documenta Naturae No. 131: 1–65. Iamandei, E. & S. Iamandei. 1999. Platanoxylon catenatum Süss & Müller-Stoll 1977 in Bacea area, Metalliferous Mts. Romania. Revue Roumaine de Géologie 43: 65–67. Iamandei, E. & S. Iamandei. 2000. Securinegoxylon bacense n.sp. in an Upper Maastrichtian- Lower Palaeocene Formation from the Bacea area, southern Apuseni (Metalliferous) Mts. Revue Roumaine de Géologie 44: 57–61. Wheeler & Lehman — Cretaceous and Paleocene woods 317

Jones, J.H. 1990. An evolutionary and paleoecological analysis of fossil woods from Baja Cali- fornia. Abstract. Third international Senckenberg conference, Frankfurt am Main, Federal Republic of Germany, May 26, 1990. Senckenberg. Naturforsch. Ges., Frankfurt am Main, Germany. Lamb, J.P. 2001. Late Cretaceous (Santonian) vegetation from the Gulf Coast. Abstracts with Programs - Geological Society of America 33 (2): 16. Meijer, J.J.F. 2000. Fossil woods from the Late Cretaceous Aachen Formation. Review of Pal- aeobotany and Palynology 112: 297–336. Page, V.M. 1967. Angiosperm wood from the Upper Cretaceous of central California. Part I. Amer. J. Bot. 54: 510–514. Page, V.M. 1970. Angiosperm wood from the Upper Cretaceous of central California. III. Amer. J. Bot. 57: 1139–1144. Page, V.M. 1979. Dicotyledonous wood from the Upper Cretaceous of central California. J. Arnold Arb. 60: 323–349. Page, V.M. 1980. Dicotyledonous wood from the Upper Cretaceous of central California. II. J. Arnold Arb. 61: 723–748. Page, V.M. 1981. Dicotyledonous wood from the Upper Cretaceous of central California. III. Conclusions. J. Arnold Arb. 62: 437–455. Petrescu, I., C. Ianoliu & I. Dragos. 1978. Prezenta genului Paraphyllanthoxylon (Euphorbiaceae) in cretacicul din Bazinul Hateg. Contr. Bot., Cluj 227–234. Prakash, U. & D. Brezinova. 1969 (iss. 1970). Wood of Bridelia from the Cretaceous of Bohemia. The Palaeobotanist 18: 173–176. Süss, H. 1960. Ein Monimiaceen-Holz aus der oberen Kreide Deutschlands, Hedycaryoxylon subaffine (Vater) nov. comb. Senck. Leth. 41: 317–330. Süss, H. 1986. Untersuchungen über fossile Buchenhölzer. Beiträge zu einer Monographie der Gattung Fagoxylon Stopes & Fujii. Feddes Repert. 97: 61–183 + pl. XVII–XXII.l. Süss, H. & W.R. Müller-Stoll. 1977. Untersuchungen über fossile Platanenhölzer. Beiträge zu einer Monographie der Gattung Platanoxylon Andreanszky. Feddes Repert. 88: 1–62 + pl. 1–14. Suzuki, M., S. Noshiro & H. Tobe. 1996. Wood structure of Japanese Mesozoic dicotyledons. In: L.A. Donaldson, A.P. Singh, B.G. Butterfield & L.J. Whitehouse (eds.), Recent advances in wood anatomy: 150–158. New Zealand Forest Research Institute. Suzuki, M. & H. Ohba. 1991. A revision of fossil wood of Quercus and its allies in Japan. J. Jap. Bot. 66: 255–274.

APPENDIX II — REFERENCES FOR INCIDENCES OF PALEOCENE WOODS

Blokhina, N.I. & S.A. Snezhkova. 1999. Fossil wood Alnus tschemrylica sp. nov. (the Betulaceae) from the Paleogene of Tschermunaut Bay (Kamchatka). Palaeontological J. 33: 466–470. Boureau, E. 1950. Étude paléoxylogique du Sahara (IX): Sur un Myristicoxylon princeps n. gen., n. sp., du Danien d’Asselar (Sahara soudanais). Bull. Mus. Natl. Hist. Nat. 2e Sér. 22: 523–528. Crawley, M. 1988. Palaeocene wood from the Republic of Mali. Bull. Brit. Mus. Nat. Hist. (Geol.) 44: 3–14. Crawley, M. 1989. Dicotyledonous wood from the lower Tertiary of Britain. Palaeontology 32: 597–622. Crawley, M. 2001. Angiosperm woods from British Lower Cretaceous and Palaeogene deposits. Special Papers in Palaentology 66. The Palaeontological Association. 100 pp. 318 IAWA Journal, Vol. 30 (3), 2009

Iamandei, E. & S. Iamandei. 1999. Platanoxylon catenatum Süss & Müller-Stoll 1977 in Bacea area, Metalliferous Mts. Romania. Revue Roumaine de Géologie 43: 65–67. Iamandei, E. & S. Iamandei. 2000. Securinegoxylon bacense n.sp. in an Upper Maastrichtian- Lower Palaeocene Formation from the Bacea area, southern Apuseni (Metalliferous) Mts. Revue Roumaine de Géologie 44: 57–61. Koeniguer, J.C. 1969 (iss. 1970). Sur un bois fossile du Paléocéne du Niger. C. R. 94e Congr. Natl. Soc. Sav., Pau, Sci., 3: 157–173. Koeniguer, J.C. 1971. Sur les bois fossiles du Paléocéne de Sessao (Niger). Rev. Palaeobot. Palynol. 12: 303–323. Melchior, R.C. 1998. Paleobotany of the Williamsburg Formation (Paleocene) at the Santee Rediversion site Berkeley County, South Carolina. In: A.E. Sanders (ed.), Paleobiology of the Williamsburg Formation (Black Mingo Group; Paleocene) of South Carolina, U.S.A.: 49–121. Transactions of the American Philosophical Society, Vol. 4, Pt. 4. Wheeler, E.A. & T.M. Michalski. 2003. Paleocene and Eocene woods of the Denver Basin, Colorado. Rocky Mountain Geology 38: 29–43.