Contribution to knowledge on ontogenetic developmental stages of Lepidodendron mannebachense Presl, 1838

Abstract

A new reconstruction of Lepidodendron mannebachense is proposed here based on collection of well-preserved compressions from middle Moscovian volcanoclastics of the Radnice Basin, Czech Republic. These specimens that represent remains of juvenile and matured individuals make progress in our current knowledge on ontogeny of this species and help us to improve its whole plant reconstruction. The juvenile stage was characterised by an unbranched columnar stem. The mature stage of L. mannebachense had an umbrella-like canopy produced by combination of more or less isotomous apical dichotomies of the stem and main branches with anisotomous pseudomonopodial branching. Dichotomous branching built the frame of the crown and continued until the limit for meristem division was reached. However, most of thin terminal shoots were anisotomous lateral branches growing from the main dichotomies. Some of them as well as terminal branches bore cones on their tips. Only a narrow zone of leaves was maintained at any stage of tree development. In the mature stage, leaves were retained only at apical parts of terminal shoots. L. mannebachense was a monocarpic type of plant with a determinate growth. Lepidodendrid lycopsids dominated many early to middle Pennsylvanian tropical wetlands. During this period these spectacular plants contributed up to 60 to 80% to the biomass production in peat-forming habitats . Therefore it is not surprising that most of the reconstructions depict the Pennsylvanian coal measure forests as dominated by the arborescent lycopsids (e.g. Walton in MacGregor & Walton 1948). However, most reconstructions, especially the earlier ones, show lepidodendrids only as mature trees with an umbrella-like canopy produced by dichotomous branching (e.g. Hirmer 1927). This interpretation was based on scarce findings of some large specimens (e.g. Lindley & Hutton 1835/37, Scott 1920) and on commonly found fragments of branch compressions showing more or less isotomous dichotomous patterns. This traditional and simplified view of these bizarre trees started to change with an onset of systematic study of anatomically preserved specimens and compressions of exceptionally complete lepidodendrid tree remains (e.g. Walton 1935, Andrews & Murdy 1958, Eggert 1961, Delevoryas 1964 and especially DiMichele 1979a, b, 1980Wnuk 1985Wnuk , 1989. These studies proved that whole plant morphology of these plants is much more complex and that various growth strategies exist (for an overview see DiMichele 1992 andPhillips 1994). Therefore it is not surprising that new findings that contribute to understanding of whole-plant reconstruction of particular species are of interest to paleobotanists. Recently, several specimens of L. mannebachense that can contribute to our knowledge on ontogenetic developmental stages of this common arborescent lycopsid have been found when revising fossil plant collections in the Museum of the Geological Survey of Austria in Vienna, the National Museum in Prague and the West Bohemian Museum in Pilsen. The whole...

Growth habit of the late Paleozoic rhizomorphic tree‐lycopsid family Diaphorodendraceae: Phylogenetic, evolutionary, and paleoecological significance

“…Efficient branch‐shedding also suggests that these plants could have spored continuously once the lowest lateral branches had reached maturity—a mode of reproduction strikingly different from that inferred for members of the Lepidodendraceae, which appear to have entered their reproductive phase only near the end of determinate growth when the crown matured (see, for example, the exceptional work by Opluštil, 2010). As in most rhizomophic lycopsids, the strobili of the Synchysidendron plant were confined to strongly anisotomous branching systems resembling that shown in Fig.…”

“…The lateral, strobilus‐bearing axes were derived from strongly anisotomous divisions of the main stem (which might consequently be termed “pseudomonopodial”) and were caducous (deciduous), dropping from the main stems as apical growth proceeded upward. Developmental studies of these plants strongly suggest that, in some of the more derived forms, the lateral branches were reduced to peduncles only, bearing either single or paired strobili (for discussion regarding the developmental aspects of these extinct Paleozoic lepidodendrids see Bateman and DiMichele, 1991; Bateman, 1994; Wang et al, 2003; Opluštil, 2010).…”

Pennsylvanian ‘fossil forests' in growth position (T 0 assemblages): origin, taphonomic bias and palaeoecological insights

“…Such deposits have permitted not only reconstruction of spatial patterns, but also reconstruction of the parent plants in remarkable detail (e.g. Oplustil 2010). The number of forests preserved in tuff is not insubstantial and occurs through much of the record, but, remarkably, there are no examples from North America.…”

Arborescent lycophyte growth in the late Carboniferous coal swamps

“…This is clearly not the case as it has been shown that even quite large stems still retained their leaves (Thomas, ; Leary & Thomas, ). As pointed out by Boyce & DiMichele (), leaf laminae abscission left their persistent, taxonomically distinctive, leaf bases (cushions) that persisted until they were sloughed off from the largest/oldest stems by secondary growth leaving an exposed surface of periderm; see Thomas (, ), Wnuk () and Opluštil () for more details on this. It is also important to realize that the leaf cushions could move apart to some extent by the expansion of the inter‐cushion epidermis during the early stages of secondary growth (Thomas, , ) allowing the outer photosynthetic surface to remain attached to the stem even after a significant increase in girth.…”