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Systematic treatment
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Family - Typhaceae
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Genus - Typha Linnaeus 1753
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Species - T. orientalis Presl 1851
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Description— Linear leaf fragments are characterized with parallel veins and entire
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margin (Fig. 2a; Fig. S1). Inter-costal (stomatal zone) and costal zones with width
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ratio ca. 4.2 are arranged alternately on both adaxial and abaxial epidermis (Fig. 2b).
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Superficial stomatal apparatuses (9.1–14.2×8.8–12.8 µm), 5–6 rows on the
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inter-costal zone, are longitudinally oriented. Subsidiary cells are brachyparacytic, i.e.
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with two lateral subsidiary cells parallel to guard cells but not completely enclosing
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them (Fig. 2c). Guard cells, 9.1–14.2×1.8–3.1 µm, are reniform. Epidermal cells with
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straight to slightly curved anticlinal walls are irregular-polygonal in the inter-costal
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zones except over the costal zones where they are elongate and rectangular (Fig. 2b, c;
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Table S3).
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Discussion— The genus Typha with ca. 10–16 species (Heywood, 1993; Mabberley,
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1997; Sun & Simpson, 2010), nearly cosmopolitan, is a perennial herb of wetland
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ecosystem (Heywood, 1993; Dahlgren et al., 1985). It is characterized by creeping
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rhizomes; distichous leaves with sheath at base; elongated spongy laminas with
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parallel venation; cylindrical spike like inflorescences with lower part female and
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upper part male, which connect each other closely or with a gap; achenes with long
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stipes (Heywood, 1993; Mabberley, 1997; Sun & Simpson, 2010). The genus is
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traditionally divided into section Bracteolatae and section Ebracteolatae based on the
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presence or absence of bracteole in female flower (Kronfeld, 1889; Graebner, 1900;
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Sun & Simpson, 2010). A recent molecular study by Na et al. (2010) supports the
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traditional classification, while the study later disagree with it (Kim & Choi, 2011).
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The leaf characters of Typha are usually regarded as unifacial, spongy, margin
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entire, linear in shape, with parallel veins. Both adaxial and abaxial epidermal
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surfaces of Typha except T. pallid are composed of inter-costal (stomata zone) and
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costal zones. Stomatal apparatuses, either sunken (Fig. S2; Plate SI 1–8; Plate SII 9–
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12) or superficial (Plate SII 13–16; Plates SIII–SV), are longitudinally oriented in
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distinct rows. Subsidiary cells are brachyparacytic (Plates SI–SII; Plate SIII 17–20) or
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paratetracytic (Plate SIII 21–24; Plates SIV–SV). Guard cells are reniform (Plates SI–
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SV). Costal epidermal cells are isodiametric, irregular-polygonal and
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rectangularly-elongated along leaf axis (Plates SI–SV). Anticlinal walls of epidermal
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cells are straight to slightly curved (Plates SI–SV).
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Based upon the consistency of leaf morphological and epidermal characteristics
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between the fossils and extant Typha, the fossils fall within the circumscription of the
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genus Typha (Table S3).
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Comparison with extant species of Typha:
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Ten species of Typha for comparison come from the PE herbarium, Institute of
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Botany, Chinese Academy of Sciences, Beijing (Table S1). Two sections are divided
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within the genus Typha, based on their adaxial and abaxial epidermal characters
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(Plates SI–SV). In section 1, covering only one species (T. pallid), stomata are
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distributed only along the margin of adaxial epidermis in 1–4 rows (Plate SI 1), and
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stomatal zones and costal zones are arranged alternately at abaxial side (Plate SI 3). In
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section 2, including 9 species, both adaxial and abaxial epidermal surfaces possess
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alternately arranged costal and inter-costal zones (Plate SI 5–8; Plates SII–SV). A key
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to separate extant species of Typha related to our Shanxi fossils based on their
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epidermal characters is listed as below.
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Key to extant species of Typha related to Shanxi fossil specimens:
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1. Apparent inter-costal and costal zones alternately arranged only at adaxial
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epidermis…………………………………………………………………T. pallid
1. Apparent inter-costal and costal zones alternately arranged at both adaxial and
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abaxial epidermis …………………………………………………………………2
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2. Stomata sunken, lower than adjacent epidermal cells……………………………
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T. elephantine, T. lugdunensis
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2. Stomata superficial, on the same level with adjacent epidermal cells…………3
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3. Subsidiary cells typically paratetracytic………T. angustifolia, T. domingensis
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3. Subsidiary cells typically brachyparacytic…………………………………4
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4. Costal epidermal cells mostly rectangular-shaped………………………
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T. orientalis, Fossil Typha
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4. Costal epidermal cells mostly irregular-polygonal-shaped………………
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T. davidiana, T. latifolia, T. laxmannii, T. minima
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Here we assign the fossils into T. orientalis due to its consistency with the extant
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T. orientalis at species level (see the key listed above; Fig. 2a–f; Table S3).
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Comparsion with other Typha fossils:
The Typha megafossils perserved as leaves, inflorescences, fruits, and seeds have
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also been reported from the late Cretaceous to late Pliocene sediments from other
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parts of the world (Table S6). The late Cretaceous Typha leaves from Wyoming, USA
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(Dorf, 1942) and seeds in Sachsen-Anhalt, Germany (Knobloch & Mai, 1986) are
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regarded as the earliest records of this genus. Among those fossil records, most of the
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leaf impressions were recognised as “Typha” mainly based on their preserved leaf
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morphology with parallel venation and transverse veinlets (e.g., Reid et al., 1926;
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Dorf, 1942; MacGinitie, 1953), which might have few and limited taxonomical value.
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We could not go to higher taxonomic resolution if no epidermal data is avaible on the
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linear or lanceolate monocot leaves with primary parallel venation preserved in the
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sediments (Herendeen & Crane, 1995; Smith et al., 2010).
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Only a case of fossil Typha leaves with epidermal data was reported in the Miocene
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sediments of southern New Zealand (Pole, 2007). Unfortunately it might be not
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unequivocal Typha based on the epidermal character combination of extant Typha.
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Unlike modern Typha, the fossil Typha sp. (Pole, 2007) lacks clear division of both
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costal and inter-costal zones on the epidermal surface and its subsidiary cells are
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dicyclic and paratetracytic rather than brachyparacytic and paratetracytic, which are
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unique combinative characters in the extant Typha based on our survey (Table S3).
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SReferences
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Structure, Evolution, and Taxonomy. Berlin: Springer-Verlag. 520 pp.
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and Palaeontology of the Fox Hills and Lower Medicine Bow Formations of Southern
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Wyoming and Northwestern Colorado, pp. 1-78. Carnegie Institute of Washington
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Graebner P (1900) Typhaceae. In: Das Pflanzenreich. (ed Engler A). Berlin,
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Herendeen PS, Crane PR (1995) The fossil history of the monocotyledons. In:
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