1 The Non-analog Vegetation of the Late 2 Paleozoic Icehouse–Hothouse and Their 12 3 Coal-Forming Forested Environments 4 Robert A. Gastaldo, Marion Bamford, John Calder, 5 William A. DiMichele, Roberto Iannuzzi, André Jasper, 6 Hans Kerp, Stephen McLoughlin, Stanislav Opluštil, 7 Hermann W. Pfefferkorn, Ronny Rößler, and Jun Wang 8 Abstract until the latest Pennsylvanian. Even the gymnosperm 22 9 A walk in the Carboniferous-and-Permian woods of the groups, which commonly grew in mineral-rich soils, are 23 10 Late Paleozoic, a time known as the Late Paleozoic Ice unfamiliar and subdominant components of these land- 24 11 Age (LPIA), would not be a walk in the woods comparable scapes. The extinct pteridosperms and cordaitaleans, and 25 12 to today’s Holocene forests. The vegetation that colonized the extant ginkgoalean, cycad, and conifer clades, ulti- 26 13 and inhabited the landscapes during glacial∗ and intergla- mately diversify and occupy better drained soil conditions 27 14 cial∗ episodes are non-analogs with the world we witness that developed in response to global climate change from 28 15 around us. Unlike continents covered in seed-bearing­ for- icehouse∗ to hothouse∗ conditions. Beginning in the latest 29 16 ests, the systematic affinities of the largest trees, and many Pennsylvanian and increasing their dominance in the 30 17 shrubs, groundcover, vines (lianas), and epiphytes lie with Permian, seed-producing clades expanded their biogeo- 31 18 the spore-producing ferns and fern allies. These ferns and graphic ranges, displacing the former fern and fern-ally 32 19 fern allies, including the club mosses (lycopsids) and giants. This change in diversity occurs during a unique 33 20 horsetails (sphenopsids), dominated both organic-rich interval in the history of Earth’s biosphere. 34 21 (peat) and mineral-substrate soils from the Mississippian The LPIA is the only time, other than the Neogene, 35 since the evolution and colonization of terrestrial plants, 36 when the planet experienced prolonged icehouse and 37 Electronic supplementary material The online version of this chapter greenhouse conditions. Extensive tropical peat swamps, 38 (https://doi.org/10.1007/978-3-030-35058-1_12) contains supplemen- tary material, which is available to authorized users. H. Kerp R. A. Gastaldo (*) Institute of Geology and Palaeontology – Palaeobotany, University Department of Geology, Colby College, Waterville, ME, USA of Münster, Münster, Germany e-mail: [email protected] e-mail: [email protected] M. Bamford S. McLoughlin Evolutionary Studies Institute, University of the Witwatersrand, Department of Palaeobiology, Swedish Museum of Natural Johannesburg, South Africa History, Stockholm, Sweden e-mail: [email protected] e-mail: [email protected] J. Calder S. Opluštil Geological Survey Division, Nova Scotia Department of Energy Institute of Geology and Paleontology, Charles University in and Mines, Halifax, NS, Canada Prague, Prague, Czech Republic e-mail: [email protected] e-mail: [email protected] W. A. DiMichele H. W. Pfefferkorn Department of Paleobiology, Smithsonian Institution, United Department of Earth and Environmental Science, University of States National Museum, Washington, DC, USA Pennsylvania, Philadelphia, PA, USA e-mail: [email protected] e-mail: [email protected] R. Iannuzzi R. Rößler Instituto de Geociências, Universidade Federal do Rio Grande do Museum für Naturkunde, Chemnitz, Germany Sul, Porto Alegre, Brazil e-mail: [email protected] e-mail: [email protected] J. Wang A. Jasper Nanjing Institute of Geology and Palaeontology, Chinese Academy Universidade do Vale do Taquari - Univates, Lajeado, RS, Brazil of Sciences, Nanjing, People’s Republic of China e-mail: [email protected] e-mail: [email protected] © Springer Nature Switzerland AG 2020 E. Martinetto et al. (eds.), Nature through Time, Springer Textbooks in Earth Sciences, Geography and Environment, https://doi.org/10.1007/978-3-030-35058-1_12 R. A. Gastaldo et al. 39 similar in physical properties to current analogs in plants–lycopsids, sphenopsids, ferns, and seed plants–were 86 40 Southeast Asia, accumulated in coastal plain lowlands. co-equal components of Carboniferous–Permian peat forests. 87 41 These forests extended over thousands of square kilome- Most of these plants reproduced exclusively by spores–the 88 42 ters during periods when global sea level was low in lycopsids, sphenopsids, ferns, and enigmatic progymno- 89 43 response to the development of extensive Gondwanan sperms–whereas the gymnosperms reproduced by seeds. 90 44 glaciation at the southern pole. When these ice sheets Many of the fossil taxa are unique to this time interval, but 91 45 melted and sea-level rose, the tropical coastal lowlands several subgroups in each broad clade persist to the present in 92 46 were inundated with marine waters and covered by near- similar ecological settings. The lycopsids were confined pri- 93 47 shore to offshore ocean sediments. The waxing and wan- marily to wetlands, the soils of which ranged from purely 94 48 ing of glacial ice was influenced by short- and long-term mineral to purely organic matter (peat) and constitute the 95 49 changes in global climate that were, in turn, controlled by majority of biomass contribution to the paleotropical peat 96 50 extraterrestrial orbital factors. As the LPIA came to a swamps (=Carboniferous and Permian coals). One taxon, 97 51 close, a new forested landscape appeared, more familiar Sigillaria, is known from sites in which the soil moisture con- 98 52 but, still, distant. ditions were better drained and, probably, seasonally dry 99 (DiMichele et al. 2005a). After the demise of tree lycopsids in 100 the Late Pennsylvanian of the paleotropics, representatives of 101 53 12.1 Introduction the clade occupied wetlands in the North and South China 102 Blocks, which persisted until the end of the Permian (see 103 54 The Industrial Revolution began in the middle of the eigh- Gastaldo et al., unit 13, this volume). Calamitean sphenopsids 104 55 teenth century and progressed rapidly after the invention of the are similar in gross structural organization to living 105 56 steam engine in 1776. The technological advances that marked Equisetales, except for the presence of secondary xylem 106 57 this time were powered by coal, which is the byproduct of peat (wood), which allowed them to grow to the size of trees. This 107 58 accumulation in extensive tropical wetland forests that cov- group occupied a narrow range of habitats, those of disturbed 108 59 ered equatorial region hundreds of millions of years ago in settings and floodplains where sedimentation built up land 109 60 what is often referred to as “Deep Time.” From the end of the surfaces. The clonal growth habit of some taxa permitted 110 61 eighteenth century to the middle of the twentieth century, as regeneration following burial in many instances (Gastaldo 111 62 exploitation of this natural resource expanded, coal-mining 1992). Several groups of ferns are known in the fossil record, 112 63 operations uncovered countless troves of fossilized plants rep- some of which are extant (see Pšenička et al., unit 11, this 113 64 resenting ancient forests. But, the plant groups comprising volume). The most conspicuous group is the marattialean 114 65 these forests were not the same as the angiosperms and gymo- ferns. Whereas modern members of this clade remain under- 115 66 sperms that have dominated the landscapes of the Paleogene story forms, some Paleozoic species grew to be trees during 116 67 or Neogene (Martinetto et al., units 1 and 2, this volume), or the LPIA. These plants, inexpensively constructed in terms of 117 68 even back in the Mesozoic (Gee et al., unit 6, this volume). carbon-biomass allocation, dominated tropical wetlands in 118 69 Rather, a hard look at them tells us that the systematic affini- the latest Carboniferous and were opportunistic taxa. In con- 119 70 ties of the largest trees, and many shrubs, groundcover, vines, trast, the progymnosperm group, which is a holdover from the 120 71 and epiphytes lie, mainly, with the spore-producing ferns and latest Devonian, is more prominent in Mississippian floras 121 72 fern allies. Imagine standing under a grove of trees, 30 m in with few recognized individuals in younger forests. These 122 73 height, where a broken canopy casts little shade, and the plants produced woody stems with conifer-like wood, some 123 74 release of spores turns the vista into a yellowish color. When of which grew to tall trees but reproduced all by spores. The 124 75 fossilized seeds were first discovered, these, too, had features progymnosperm group is a transitional mosaic to the true 125 76 very different from modern groups (Oliver and Scott 1903). seed-producing gymnosperms (see Gensel et al., unit 15, this 126 77 And, when seeds were found attached to their parental plants, volume). With the advent of seeds, true gymnospermous 127 78 it was recognized that these gymnosperms were also very dif- plants came to dominate terra ferma habitats but were also 128 79 ferent from modern forms, although several growth architec- widespread in wetlands. Several extinct groups are found in 129 80 tures look familiar (DiMichele et al. 2005a). the Permo–Carboniferous swamps including medullosan and 130 lyginopterid pteridosperms (seed ferns) in the wet tropics and 131 the cordaites, a sister group of the conifers, in both the wet 132 81 12.2 LPIA Tropical Forests: The Players and seasonally dry tropics and the north temperate zone. The 133 fossil record of the conifers and other gymnospermous groups 134 82 The coal forests of the Carboniferous were dominated by is less common in Carboniferous paleoequatorial forests and, 135 83 entirely different plant groups from those contributing most in general, found in the seasonally dry tropics.