See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/278066291 Fossil Palms (Arecaceae, Coryphoideae) Associated with Juvenile Herbivorous Dinosaurs in the Upper Cretaceous Aguja Formation, Big Bend National Park, Texas Article in International Journal of Plant Sciences · July 2010 DOI: 10.1086/653688 CITATIONS READS 15 77 3 authors, including: Steven R Manchester Elisabeth Wheeler Florida Museum of Natural History North Carolina State University 202 PUBLICATIONS 5,388 CITATIONS 82 PUBLICATIONS 1,731 CITATIONS SEE PROFILE SEE PROFILE Available from: Steven R Manchester Retrieved on: 23 July 2016 Int. J. Plant Sci. 171(6):679–689. 2010. Ó 2010 by The University of Chicago. All rights reserved. 1058-5893/2010/17106-0009$15.00 DOI: 10.1086/653688 FOSSIL PALMS (ARECACEAE, CORYPHOIDEAE) ASSOCIATED WITH JUVENILE HERBIVOROUS DINOSAURS IN THE UPPER CRETACEOUS AGUJA FORMATION, BIG BEND NATIONAL PARK, TEXAS Steven R. Manchester,1,* Thomas M. Lehman,y and Elisabeth A. Wheelerz *Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, U.S.A.; yDepartment of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, U.S.A.; and zDepartment of Forest Biomaterials, North Carolina State University, Raleigh, North Carolina 27695-8005, U.S.A., and North Carolina State Museum of Natural Sciences, Raleigh, North Carolina 27601-1029, U.S.A. Seeds of two palm species conforming to the extant genus Sabal have been recovered from the Campanian (Upper Cretaceous) Aguja Formation of Big Bend National Park, Texas: Sabal bigbendense sp. nov. and Sabal bracknellense (Chandler) Mai. These remains, found together with anatomically preserved palm stems, augment previous reports of Sabalites ungeri (Lesq.) Dorf leaves from the same formation. The co-occurrence of palm seeds with numerous juvenile hadrosaur and ceratopsian bones indicates that palms closely related to modern cabbage palms may have provided fodder and shelter for young herbivorous dinosaurs. The distribution of these and other Late Cretaceous palm fossils is reviewed. Keywords: Arecaceae, Campanian, ceratopsians, dinosaur herbivory, fossil, leaves, Sabal, seeds, stems, Texas. Introduction phytogeography of this genus and the ecological co-occurrence with herbivorous dinosaurs. Big Bend National Park in southwestern Texas preserves a continuous sequence of Upper Cretaceous (Campanian- Geologic Setting Maastrichtian) through Lower Tertiary (Paleocene) continental strata. These strata contain a varied terrestrial and aquatic The Aguja Formation contains two terrestrial intervals re- vertebrate fauna of Judithian age (;79–74 Ma; Lehman and ferred to informally as the lower and upper shale members Busbey 2007) and a diverse assemblage of dicotyledonous (Lehman and Busbey 2007). Both the lower shale member and and coniferous woods (Wheeler 1991; Wheeler et al. 1994; the lowermost part of the upper shale member consist primar- Wheeler and Lehman 2000, 2005, 2009; Lehman and Wheeler ily of dark organic-rich shale, lignite, and coal that accumu- 2001). Monocotyledons, represented by leaves, seed casts, and lated in poorly drained brackish-water marshes or swamps petrified stems and roots, also occur commonly in the Campa- close to the shoreline. These deposits interfinger with coastal nian Aguja Formation and include some of the oldest records strand plain and marine shelf deposits of the Pen Formation. for coryphoid palms. The seeds and stems co-occur with bones The upper part of the upper shale member consists of drab of juvenile hadrosaur and ceratopsian dinosaurs at multiple fluvial floodplain deposits, primarily olive, yellow, and gray localities. mudstone interbedded with lenticular stream channel sand- In this article we describe the Aguja palm seed and stem re- stone. These sediments accumulated in better-drained fresh- mains, which, along with the leaf remains already described water alluvial environments some distance landward of the by Dorf (1939), allow recognition of the modern coryphoid shoreline. Most of the diverse fossil wood assemblage thus far palm genus Sabal in the Upper Cretaceous. Sabal Adanson ex documented for the Aguja Formation has been recovered Guersent, with 15 extant species, is now confined to Mexico, from the upper shale member, including a unique association the Caribbean Islands, Bermuda, and the southeastern United of in situ tree stumps (Agujoxylon olacaceoides and Metcal- States (Zona 1990), but fossil records indicate that the genus feoxylon kirtlandense) that demonstrates that dicot trees were was more widespread in the Northern Hemisphere, occurring dominant canopy-forming elements in some Late Cretaceous in midlatitudes of North America and Europe and possibly forests at lower latitudes of western North America (Lehman also in Asia during the Tertiary (reviewed in Manchester and Wheeler 2001). 1999; Dransfield et al. 2008). Although Sabal was previously Palm leaf impressions and permineralized stem fragments recognized based on seeds as old as Early Eocene (;52 Ma), are found throughout the Aguja Formation, as well as in the the Aguja occurrence extends the minimum age of this genus overlying Javelina Formation. Baghai (1996) reported pollen back to the Campanian (;77 Ma). The significance of fossil having suggested affinities with the palm family (Arecaceae; Sabal from the Aguja Formation is considered in relation to the e.g., Arecipites Wodehouse, Palmaepollenites Potonie´, Mono- colpopollenites Thomson & Pflug, Sabalpollenites Thiergart in Raatz) from throughout the same stratigraphic interval. 1 Author for correspondence; e-mail: steven@flmnh.ufl.edu. However, the palm seed collection sites described herein and Manuscript received April 2010; revised manuscript received April 2010. the best-preserved in situ palm stems are confined to the lower 679 680 INTERNATIONAL JOURNAL OF PLANT SCIENCES 50 m of the Aguja upper shale member (fig. 1). Vertebrate bio- 2007). Exact locality information and maps for the collection stratigraphy (Rowe et al. 1992) and radiometric age determi- sites are available at the Florida Museum of Natural History nations (Befus et al. 2008) indicate that the upper shale Paleobotanical Collection, University of Florida, Gainesville, member of the Aguja Formation is Middle to Late Campa- and at the Vertebrate Paleontology Laboratory of the Texas nian in age. Memorial Museum in Austin. Description of Fossil Seeds Material and Methods The fossil seeds and stems described herein were collected at Sabal bigbendense sp. nov. (Fig. 2A–2H) four sites near the western border of Big Bend National Park. Diagnosis. Seeds subglobose-oblate, rounded dorsally; prox- Two localities are on the southern side of Rattlesnake Moun- imal surface with a broad circular depression that is domed tain, about 1 km apart and 2 km north of Maverick Road. in the center. Seeds 12.0–13.9 mm in diameter and 11.0– These two sites are Texas Memorial Museum (TMM) verte- 11.1 mm in height. Surface smooth to wrinkled. Germination brate fossil localities TMM 42534 (20 m above the base of operculum small (2.0 mm), circular, positioned equatorially the upper shale member) and TMM 43163 (40 m above to supraequatorially. the base of the upper shale member), equivalent to Florida Specimens. Holotype, here designated: UF403-53791 (fig. Museum of Natural History Paleobotanical Collection (UF) 2E–2G). Paratypes: UF402-53789 (fig. 2A,2B), UF403- localities 402 and 403, respectively. Two additional sites 53792 (fig. 2C,2D), UF403-53793 (fig. 2H). are TMM 41917 (UF401), near Bruja Canyon, and WPA-1 Localities. TMM 42534 and TMM 43163. (UF404), a site originally excavated as part of a Works Prog- These suboblate seeds conform to Sabal in having a circular ress Administration (WPA) project in the 1930s (Lehman outline; a circular rim surrounding a basal scar including the Fig. 1 Geographic and stratigraphic location of selected palm-bearing sites in the Aguja Formation of Big Bend National Park, Texas. The map shows positions of measured stratigraphic sections (1–8), also shown on a restored cross section of the intertonguing Aguja and Pen formations. Sites discussed in the text near Rattlesnake Mountain (RM) are shown, as is the approximate stratigraphic level of Dorf’s (1939) palm collection site. The stratigraphic section of the Aguja Formation at Rattlesnake Mountain shows informal subdivisions and levels of palm-bearing Texas Memorial Museum (TMM) vertebrate fossil sites and the WPA-1 ceratopsian bone bed described by Lehman (2007). Fig. 2 Fossil and extant Sabal seeds. A–H, Sabal bigbendense sp. nov. from the Aguja Formation. A, B, Basal view showing circular outline and hilar scar and lateral view showing protruding hilum and supraequatorial circular germination operculum scar; UF402-53789. C, D, Basal and lateral views of seed with longitudinally ruptured seed coat; UF403-53792. E–G, Basal, lateral, and apical views, with circular germination operculum. Arrow in G and subsequent illustrations indicates the germination operculum; UF403-53791. H, Specimen with longitudinal fractures; UF403-53793. I–S, Sabal bracknellense (Chandler) Mai from the Aguja Formation. I–K, Basal, apical, and lateral views of seed with fully intact seed coat, showing irregular indentations; UF403-53795. L, M, Basal and lateral views of seed; UF404-53798. N, O, Basal and lateral views of seed; UF403-53794. P, Q, UF401-53784. R, S, Lateral and apical views of seed; UF401-53785. T–V, Extant Sabal palmetto, Gainesville, Florida; basal