The Oligocene Equisetum from Qaidam Basin, Northeastern Tibetan Plateau in China and its implications

Megafossils of Betulaceae from the Oligocene of Qaidam Basin and their paleoenvironmental and phytogeographic implications

“…A. confucii Unger (Simarubaceae), which was found from a nearby layer and is the most common member among fossil Ailanthus , is thought to have shared a similar ecological niche with extant A. altissima in the past, also indicating that climate conditions at the fossil site were much warmer and more humid during the early Oligocene than currently ( Yang et al., 2021b ). In addition, some fossil fruits and leaves from this region, including Podocarpium (A. Braun) Herendeen, Acer L., Ulmus L., Cupressus L., Chamaecyparis Spach, Thuja L., Adiantum L., and Equisetum L., have been previously reported ( Yan et al., 2018 ; Chen et al., 2021 ; Yang, 2022 ). Preliminarily research based on the coexistence approach suggests that the mean annual temperature (MAT) and mean annual precipitation (MAP) was about 14 °C and 600–1200 mm, respectively ( Yang, 2022 ), which is partly consistent with a recent study ( Song et al., 2020 ) focused on coetaneous northeastern Qaidam Basin (MAT = 11.6 ± 2.4 °C, MAP > 1000 mm).…”

Evidence of the oldest extant vascular plant (horsetails) from the Indian Cenozoic

“…cf. fluviatoides China Stem Chen et al (2021) Equisetum sp . Ethiopian plateau Stem García Massini et al.…”

“…, E. arcticum Pavlyutkin et al.) from the Cenozoic Period of Asia, North America, Europe, and Africa ( Table 2 ; Knowlton, 1902 ; Jennings 1920 ; Smith, 1938 ; Bell, 1949 ; Graham, 1963 ; Becker, 1973 ; Brown, 1975 ; Hickey, 1977 ; Mciver and Basinger, 1989 ; Verdcour, 1999 ; Uhl et al., 2002 ; Silva–Pineda et al., 2009 ; Pole and McLoughlin, 2017 ; Chen et al, 2021 ; Pavlyutkin et al., 2020 ). The current Siwalik specimens are characterized by the narrow-jointed stem, 10–15 mm long internodes, 10–12 teeth present in deep brown leaf sheath, basal fused lamina, and apically pointed tip with longitudinal striae, key characters that differentiate our specimens from earlier reported stem fossil species of Equisetum .…”

“…cf . fluviatoides 3–19 mm 10–30 mm 12–30 – – – – – – Chen et al (2021) E. clarnoi < 8 mm 25 mm Visible – – – – – Sunken stomata arranged vertically in a single line flanking each of the external biangulate stem ridges Brown (1975) E. arcticum 5 Visible 14–16 – – – – – – Pavlyutkin et al. (2020) E. magnum 10–18 > 43 30–60 – – Acute to acuminate 1–3 mm 3 mm – Hickey (1977) E. alexoensis < 10 mm 50 mm > 24 – – – – – – Bell (1949) E. fluviatoides 3–19 mm 30 mm 12–30 9–23 mm 12–30 Attenuate – – – Mciver and Basinger (1989) E. siwalikum sp.…”

“…9 ). The terminology for the morphological descriptions of fossil specimens follows Pole and McLoughlin (2017) and Chen et al. (2021) .…”