Cyclic changes in Pennsylvanian paleoclimate and effects on floristic dynamics in tropical Pangaea

Evidence for an Earliest Late Carboniferous Divergence Time and the Early Larval Ecology and Diversification of Major Holometabola Lineages

“…This delay (Nel et al, 2007;Béthoux, 2008) is attributable to an exponential diversification process whereby long lead times of comparatively low diversity are an extended prelude to a much later, sudden, and noticeably increased burst of diversification (Labandeira, 2005). For the Holometabola, this is best explained by the presence of sufficient climatic oscillation in the Pangaean equatorial belt such that fitness benefits gradually would accrue to holometabolous clades through heightened interspecies competition and through creation of underutilized or otherwise ecologically transformed niches during the Permian (Roscher and Schneider, 2006;DiMichele et al, 2010). Initial entry of holometabolous clades thus would have been achieved by selective forces encountered at the species level through gradual replacement of nonholometabolous taxa disadvantaged by Permian climatic oscillations.…”

“…It is significant that there was about an 80 million-year lag between the origin of holometaboly and its eventual global implementation, significantly after major climatic perturbations during the earlier Permian (DiMichele et al, 2010) and the multiple environmental crises towards the end of the period (Erwin, 2006). This delay (Nel et al, 2007;Béthoux, 2008) is attributable to an exponential diversification process whereby long lead times of comparatively low diversity are an extended prelude to a much later, sudden, and noticeably increased burst of diversification (Labandeira, 2005).…”

Wetland-Dryland Vegetational Dynamics in the Pennsylvanian Ice Age Tropics

“…The floras from this time, Morrowan and Atokan, encompassed a considerable diversity of wetland species, including Lepidodendron, pteridosperms such as Neuropteris, and various calamitaleans (Tidwell 1967;Tidwell et al 1992;Lucas et al 2009). During the later Middle Pennsylvanian (Desmoinesian) and Late Pennsylvanian (Tidwell 1988;Tidwell et al 1999;DiMichele et al 2004DiMichele et al , 2010DiMichele et al , 2013bDiMichele and Chaney 2005;Lerner et al 2009;Tabor et al 2013aTabor et al , 2013b, western wetland floras were less widespread and, as in the eastern coal basins, were greatly enriched in tree ferns, with a continued presence of pteridosperms and Sigillaria as the only tree lycopsid (figs. 15E-15L, 16B-16E).…”

Palaeoecology of Macroneuropteris scheuchzeri, and its implications for resolving the paradox of ‘xeromorphic’ plants in Pennsylvanian wetlands

“…Various lines of evidence -geochemistry (Cecil et al, 1985;Greb et al, 2002), palynology (Eble et al, 2001;Eble, 2002;Eble et al, 2003), plant megafossils (Pfefferkorn and Thomson, 1982;Phillips and Peppers, 1984;Cleal et al, 2009), the distribution of coals (Phillips and Peppers, 1984;Schutter and Heckel, 1985) and paleosols (Schutter and Heckel, 1985;FalconLang et al, 2009;DiMichele et al, 2010;Falcon-Lang and DiMichele, 2010) -indicate that this was a time of much more seasonal climates at all phases of any given glacial-interglacial cycle. Peat swamps appear to have been largely planar, peats (coals) were of higher sulfur content, and vertic paleosols were increasingly common in those rocks between and beneath coals.…”

“…Most of these formed under seasonally dry climatic regimes unfavorable to the accumulation of peat, such as channel-fill sediments formed contemporaneously with seasonally dry paleosols, and encompass a diverse array of plants varying greatly among the deposits (e.g., Leary, 1981;Feldman et al, 2005). Some of these come from sequences of floodplain or coastal plain deposits in which conditions were unfavorable for peat formation even if the landscape or local depositional environment was periodically quite wet, such as deposits capturing plants that grew within channel belts in what may have been, overall, seasonally dry environments (e.g., DiMichele et al, 2010). Thus, this group is more heterogeneous and contains a greater variety of depositional settings and original habitat conditions than the other two.…”