Two New Species of Symplocos Based on Endocarps from the Early Miocene Brandon Lignite of Vermont, USA
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Acta Palaeobotanica 58(2): 185–198, 2018 e-ISSN 2082-0259 DOI: 10.2478/acpa-2018-0008 ISSN 0001-6594 Two new species of Symplocos based on endocarps from the early Miocene Brandon Lignite of Vermont, USA BRUCE H. TIFFNEY 1*, STEVEN R. MANCHESTER2 and PETER W. FRITSCH 3 1 Department of Earth Science and College of Creative Studies, University of California, Santa Barbara, California, U.S.A., 93106; e-mail: [email protected] 2 Florida Museum of Natural History, Dickinson Hall, P.O. Box 117800, Gainesville, Florida, U.S.A, 32611; e-mail: [email protected] 3 Botanical Research Institute of Texas, Fort Worth, Texas, U.S.A., 76107; e-mail: [email protected] Received 27 April 2018; accepted for publication 6 June 2018 ABSTRACT. We describe two new species of Symplocos (Symplocaceae) from the early Miocene Brandon Lignite Flora of Vermont, USA. The endocarps of Symplocos laevigata (Lesq.) comb. nov. are most similar in morphology and anatomy to those of the extant species S. tinctoria of southeastern North America and S. wikstroemiifolia of eastern Asia, both of S. sect. Hopea, and to those of several species of S. sect. Lodhra, endemic to eastern Asia; they are also somewhat similar to those of S. minutula of the Tertiary of Europe. The endocarps of Symplocos hitchcockii sp. nov. are most similar in morphology and anatomy to those of living members of S. sect. Lodhra, and are also somewhat similar to fossil S. incurva of the Tertiary of Europe. This report extends the fossil record of Symplocos endocarps to eastern North America and underscores the mixed mesophytic to subtropical nature of the Brandon flora. KEYWORDS: Symplocos, Symplocaceae, endocarps, early Miocene, Brandon Lignite, Vermont, USA INTRODUCTION The Brandon Lignite flora of Forestdale, palynoflora (Traverse 1955), as well as exami- Rutland County, Vermont (43°50′N, 73°03′W) nations of fruits and seeds of the Nyssaceae provides one of the few windows into the Neo- (Eyde & Barghoorn 1963) and Alangiaceae gene vegetation of northeastern North Amer- (Eyde et al. 1969). In subsequent research, ica (Graham 1999, Ochoa et al. 2012, Baum- fruits and seeds were described represent- gartner 2014). It was first noted by Edward ing the Alismataceae, Illiciaceae, Lythraceae, Hitchcock (1853), and the fruits and seeds Magnoliaceae, Rutaceae, Sargentodoxaceae, were initially described by Leo Lesquereux Staphyleaceae and Vitaceae (Tiffney & Bar- (1861a, b). They were again studied in the ghoorn 1976, 1979, Tiffney 1977a, b, 1979, early 1900s by the state geologist of Ver- 1980, 1981, 1993, Haggard & Tiffney 1997). mont, George Perkins (1904, 1906), resulting The known flora is dominated by mixed meso- in a proliferation of new genera and species, phytic forest elements, several of which have now recognized to represent variations within been extirpated from North America but per- a far more limited diversity of taxa. A detailed sist in eastern Asia. re-investigation of the flora was initiated by Symplocos Jacq. (Ericales: Symplocaceae) Elso Barghoorn in the late 1940s, resulting in was first recognized in the Brandon flora descriptions of the woods (Spackman 1949) and from pollen (Traverse 1955). Tiffney (1977a) identified two separate fruit morphologies * Corresponding author as belonging to the genus, but these were 186 B.H. Tiffney et al. / Acta Palaeobotanica 58(2): 185–198, 2018 neither described in detail nor formally named, whether these fossils are more closely related although Mai (1986) illustrated and com- to extant North American, South American, or mented on them. The nomenclature of these Old World species. and other Brandon fossils was complicated because the pioneering investigators applied multiple specific and generic names to what STRATIGRAPHY was ultimately the same species. Further, the Brandon fossils were illustrated by drawings The Brandon flora occurs within lignite and (Lesquereux 1861b), and their descriptions associated variegated clays situated in an elon- often involved only the external morphology, gate, narrow, kaolin-filled cleft between two with no information on internal structure or resistant Cambrian rocks: the Dunham Dolo- anatomy. Additionally, many of the type speci- mite and Cheshire Quartzite. The full extent mens were difficult to locate. of the deposit is uncertain, but underground Extant Symplocos comprises about 350 liv- mining in the late 19th and early 20th centu- ing species of trees and shrubs, distributed ries suggests that it is ca 60 m deep, ca 100 m from India through Southeast Asia and Male- across and ca 1–2 km long. During the Pleis- sia to northeastern Australia, as well as in the tocene glaciation, much of the fossil-bearing Americas, where they are mostly restricted deposit was eroded away, but portions of the to the Neotropics (Nooteboom 1975, Fritsch lignite and associated clays were forced into et al. 2008). During the Tertiary, Symplocos the kaolin by the overriding ice, protecting the was common and widely distributed in Europe fossils. No other rocks of Cenozoic age occur (e.g. Mai & Martinetto 2006). Endocarps of in proximity, and there is no basis for radio- the genus have been reported from Tertiary metric dating; thus, the age of the sediments sites in North America (Tiffney 1977a, Doyle is based entirely on biostratigraphy. Tiffney et al. 1988, Manchester 1994). Reports of fossil (1994), reviewing the carpological flora, and leaves (e.g. Chaney & Sanborn 1933, MacGin- Traverse (1994), reviewing the palynologi- itie 1969) are difficult to confirm because of cal evidence, both independently and jointly their similarity to those of other ericalean (Tiffney & Traverse 1994) suggested an early genera. Miocene age for the flora, with Traverse (1994) The classification of extant Symplocaceae suggesting more specifically a middle early has been updated through phylogenetic analy- Miocene age: ca 18 to 20 Ma. ses based on morphological characters and DNA sequence data (Fritsch et al. 2008). This classification, accommodating the generaSym - MATERIALS AND METHODS plocos and Cordyloblaste Henschel ex Moritzi, and including two subgenera, three sections, The deposit is generally covered by Pleistocene and Holocene sediments, and was mined locally for coal and two series within Symplocos, has provided in the middle 1800s. The mining revealed the mate- a framework for the evaluation of fossil rep- rial described by Lesquereux (1861a, b). It was again resentatives of the family. Fruit morphology mined for paper clay and pigmented clays in the late and anatomy provide additional characters 1800s through 1920s, providing Perkins with material. that help to circumscribe clades resolved by The precise derivation of these early fossils within the deposit is unclear, as many came from underground DNA. Hence, fossil fruits can provide informa- workings. A small area of sediment near the surface tion relevant for the phylogenetic placement of was uncovered with the use of heavy equipment in the extinct species and facilitate the study of bio- late 1940s and again in the early 1970s. This revealed geographic patterns through time. a narrow band of lignite and associated dark gray The Brandon fossil fruits are well preserved, plastic clay. Both were distorted and clearly not in the original position, presumably having been deformed with anatomical features of endocarp, meso- by the passage of Pleistocene ice. The two separate carp and exocarp intact, facilitating detailed units reflect distinct environments and have yielded comparison with extant members of the Sym- slightly different floras, although with elements in plocaceae. On this basis, we describe two spe- common. Collection involved taking large masses of cies of Symplocos from the Brandon Lignite, the lignite and the clay and breaking them by hand to seek fossils; the clay was also broken down in a mild evaluate their phylogenetic position in relation base and sieved for smaller specimens (Tiffney 1990). to extant species, and consider their biogeo- The sectioned fossil materials were prepared by graphic implications. Of particular interest is Richard Eyde and Bruce Tiffney by dehydrating in B.H. Tiffney et al. / Acta Palaeobotanica 58(2): 185–198, 2018 187 ethanol and embedding in celloidin (Johansen 1940) cited the illustrations that were to be pub- prior to sectioning with a Bausch & Lomb sliding lished in the upcoming volume Report on microtome (# 10164) in sections 20 to 40 μm thick, the Geology of Vermont (RGV; Lesquereux and were visualized by transmitted light. Several fossils, including the type material, were examined 1861b). The RGV was published in two vol- with x-ray microCT scanning technology, using a GE umes (Hitchcock 1861). The illustrations of Phoenix V|tome|xm240 CT Scanner at the Uni- several taxa of Brandon fossil fruits and seeds versity of Florida College of Engineering Nanoscale and their captions were published in the first Research Facility, with a tungsten reflection target. volume (pgs 228–234), and the descriptions Reconstructed tiff stacks were processed with Avizo 9.0 lite software to obtain isosurface renderings and (repeated from Lesquereux 1861a) were pub- virtual slices. lished as an appendix in the second volume, We examined fruits of 198 living species repre- pages 712–718. In initially describing Nyssa sented by more than 420 collections of the herbaria laevigata, Lesquereux (1861a, p. 361) cited of Naturalis Biodiversity Centre-Leiden (L), the Field Museum (F), the California Academy of Sciences (CAS the figure in which it was to be illustrated in and DS) and Harvard University (A and GH). They RGV volume one as Fig. 156. In his descrip- were sectioned transversely with a diamond-bladed tion of N. laevigata in RGV volume two, page annular saw and photographed to record internal mor- 717, however, he cites the accompanying illus- phology and anatomy by reflected light. Fruits from tration as Fig. 151. However, it is clear that the same collections were boiled to soften them, and outer tissues removed to expose the endocarp surface the RGV illustration number should have been features.