Lycopsida from the lower Westphalian (Middle Pennsylvanian) of the Maritime Provinces, Canada

Abstract

A taxonomic revision of lycopsids is presented as part of a reassesment of lower to middle Westphalian adpression floras from the Maritime Provinces of Canada. Being elements of the swamp flora their record reflects sedimentary bias. Systematic collecting from the “Fern Ledges” at Saint John (New Brunswick) has yielded only a few lycopsid remains as a result of the allochthonous facies. Most records (mainly by W.A. Bell in the twentieth century) correspond to sporadic collecting by Geological Survey of Canada (GSC) personnel. Their specimens are kept in GSC Ottawa. Additional remains are in museums at Montréal (Quebec), Joggins (Nova Scotia) and Saint John (New Brunswick). We introduce a new species (Lepidodendron bellii), and reinstate another (Diaphorodendron decurtatum) described by Dawson in the 19th century. Altogether, 26 taxa are described, including stem and branch remains as well as roots, leaves, strobili and sporophylls. Three specimens are illustrated from localities outside Canada so as to clarify specific characters. A copy of Lindley and Hutton’s illustration of the type of Lepidodendron dilatatum (here recorded as Bergeria dilatata) is figured in the context of a redefinition of the genus Bergeria for stem remains with false leaf scars. Problems surrounding the morphological interpretation of arborescent lycopsids of Pennsylvanian age are discussed, and the stratigraphic and paleogeographic distribution are recorded for the different taxa. The identity of the Pennsylvanian flora of the Canadian Maritimes with that of the British Isles and western Europe in general is emphasized by the synonymies discussed. Paleogeographic proximity and a similar paleolatitude justify the identity of floras.

The distribution of plant fossils and their palaeoecology inDuckmantian(Bashkirian, Lower Pennsylvanian) strata atBrymbo, North Wales, UK

“…As stated above, we do not accept the view of Álvarez‐Vásquez and Wagner () that all leafy shoots should be included in the genus Bergeria , preferring to continue using the genus Ulodendron .…”

“…Álvarez-Vásquez and Wagner (2014) and Álvarez-Vásquez, Bek, Knight, and Wagner (2018) Bergeria which to us does not seem logical. Álvarez-Vásquez and Wagner (2014) added the comment that "the shape and size of the leaf scar to be due to the position of the leaf with regard to the leaf cushion and to the kind of leaf base, which may be either narrow or more laterally extensive."…”

“…As stated above, we do not accept the view of Álvarez-Vásquez and Wagner (2014) that all leafy shoots should be included in the genus Bergeria, preferring to continue using the genus Ulodendron. The leaf cushions are rhomboidal, slightly broader than long, and separated by narrow grooves (Figure 13a,b).…”

“…Álvarez‐Vásquez and Wagner () and Álvarez‐Vásquez, Bek, Knight, and Wagner () transferred all leafy stems of arborescent lycophytes to the genus Bergeria Presl in Sternberg, , defining it as “lycopsid stems covered with spirally arranged, rhomboidal leaf cushions, longer than broad, contiguous or separated by narrow grooves, and without a differentiated leaf scar. Leaves linear‐lanceolate, entire, single‐veined.” They argued that commonly encountered species such as L .…”

“…However, interpreted in this way, all leafy lycophyte shoots with attached cones would also be included in Bergeria which to us does not seem logical. Álvarez‐Vásquez and Wagner () added the comment that “the shape and size of the leaf scar to be due to the position of the leaf with regard to the leaf cushion and to the kind of leaf base, which may be either narrow or more laterally extensive.” We believe that the line near the top of the leaf cushion would be better described as a “false leaf scar” as done by Chaloner (, , , p. 533) because many leafy stems lose their laminae when the rock is split. It is most likely that all parts of arborescent lycophytes were originally leafy and only when the taller, maturing plants started to branch that their lower parts would have been shaded, with a subsequent reduced ability to photosynthesize, prompting the loss of leaf laminae (Thomas & Cleal, ).…”