Yuguangia ordinata gen. et sp. nov., a New Lycopsid from the Middle Devonian (Late Givetian) of Yunnan, China, and Its Phylogenetic Implications

Abstract

A new heterosporous and ligulate lycopsid, Yuguangia ordinata gen. et sp. nov., is described from the Haikou Formation (late Givetian) of Yunnan Province, southwestern China. Its slender stems branch isotomously. Vegetative leaves are arranged in pseudowhorls. Compact bisporangiate strobili terminate distal branches and have megasporangia located proximally and microsporangia distally. Sporophylls are differentiated into horizontal pedicel, upturned lamina, and downward ''heel,'' and they are pseudowhorlly arranged, with about eight per gyre. Each sporophyll bears adaxially one mega-or microsporangium. Megasporangia and microsporangia are obovoid, round to elliptical in shape. Each megasporangium contains four or more Trileites-type megaspores. Microspores are comparable, to some extent, to those of the dispersed spore genus Acinosporites. A ligule is located at the distal end of the horizontal pedicel of a sporophyll. Distal axes have an exarch primary xylem strand, phloem, and a two-zoned cortex. This study provides a new temporal framework for ligule acquisition and early diversification of heterosporous lycopsid lineages and implies that homosporous, ligulate lycopsid lineages (i.e., Leclercqia of Protolepidodendrales) and heterosporous, ligulate lycopsid lineages (i.e., Selaginellales and Isoetales) had diverged by the late Middle Devonian.

A new Late Devonian isoetalean lycopsid from New South Wales, Australia: Cymastrobus irvingii gen. et sp. nov

“…Sporophylls of Yuguangia cones show a short pedicel and a relatively long lamina. The heel, as shown on Hao et al's (2007, figure 4) reconstruction, actually corresponds to a deflection, rather than a distal thickening, of the pedicel. Finally, in the cone axis of both Mixostrobilus and Yuguangia, the outline of the primary xylem is not undulated as in the Barraba cone.…”

“…Indeed, the Mixostrobilus cones, estimated to reach 7 cm in length, do not exceed 3.5 cm in width (Senkevitsch et al, 1993). Those of Yuguangia which may be up to 16 cm long are less than 1 cm wide (Hao et al, 2007). Mixostrobilus mega-and microsporangia are irregularly arranged and not separated in well-differentiated zones as in the Barraba cone.…”

“…The record of Devonian cones assignable to the lycopsids has greatly increased in the last 20 years and currently comprises about 15 taxa ranging from the Givetian (Senkevitsch et al, 1993;Cai and Chen, 1996;Hao et al 2007) to the late Famennian (Fairon-Demaret, 1977;Chitaley and McGregor, 1988). A majority of these fructifications, however, differs markedly from the Australian cone by their slender shape and smaller size, by the morphology of their sporophyll-sporangium units, and by their sporangial content.…”

Lilingostrobus chaloneri gen. et sp. nov., a Late Devonian woody lycopsid from Hunan, China

“…The earliest heterosporous genera are the Middle Devonian Mixostrobus [ 15 ], Yuguangia [ 16 ] and Longostachys [ 17 ]. Mixostrobus [ 15 ] and Yuguangia [ 16 ] bear bisporangiate strobili and do not produce secondary xylem.…”

From the Guiana Highlands to the Brazilian Atlantic Rain Forest: four new species of Selaginella (Selaginellaceae – Lycopodiophyta: S. agioneuma, S. magnafornensis, S. ventricosa, and S. zartmanii)

“…Selaginella P. Beauv. ( 1804 : 478, Selaginellaceae – Lycopodiophyta) is the most species-rich genus of extant lycophytes ( Valdespino, 2015a ; PPG I, 2016 ; Valdespino, 2016 ; Valdespino, 2017a ) and one of the oldest seedless vascular plants with fossils dating approximately 333–350 mya ( Banks, 2009 ) and 330–390 mya ( Hao et al, 2007 ; Klaus et al, 2016 ). The genus includes some 600–750 ( PPG I, 2016 ; Valdespino, 2016 ) or ca.…”