Psilophyton Research Articles

Revisiting the Rebreuve plant assemblage from the Lower Devonian of Artois, northern France

ABSTRACT French Lower Devonian floras are rare, especially compared to certain other Western European countries. In this study, we reassess an assemblage collected in the 1930s in the Rebreuve quarry (Pas-de-Calais, northern France). We describe new features in several taxa and update taxonomic names from original descriptions. For instance, re-examination of vegetative remains previously described as Psilophyton princeps, led to the discovery of fertile structures allowing us to refer these specimens to Sawdonia. In total, this flora consists of 10 taxa, including up to four different Psilophyton species, such as P. parvulum. Other taxa include Danziella artesiana, Drepanophycus cf. spinaeformis, Sporogonites exuberans and some specimens of Taeniocrada and Sciadophyton, revealing a diverse Lower Devonian plant assemblage. The Rebreuve assemblage represents a typical Emsian flora from Laurussia and bears striking resemblance with coeval Belgian assemblages. Previous palynological investigations, in addition to the similarities with well-dated Belgian floras, suggest an early Emsian age for this assemblage. The paleogeographical implications of findings are discussed.

THE ALLOMETRY OF PLANT REPRODUCTIVE BIOMASS AND STEM DIAMETER

The allometry of reproductive biomass M was determined for one moss (Polytrichum commune), four pteridophytes (Psilophyton princeps, Psilotum nudum, Lycopodium lucidulum, and L. clavatum), six gymnosperms (Larix decidua, Pseudotsuga douglasii, Tsuga canadensis, Pinus rigida, Picea abies, and Taxus baccata), and two angiosperms (Crataegus sp. and Quercus bicolor). Biomass M was measured for individual and grouped reproductive organs and regressed as a function of stem diameter D measured proximal to M for representative reproductive stems from each species. Published data for Cooksonia pertoni were used to estimate sporangial M. The data from this vascular plant fossil were compared to those from other species. Least squares regression of the entire data set yielded M = 0.12D2,9 (r2 = 0.94, N = 215), indicating that M, on the average, compiled with M Dα3.0. The allometries of the moss, pteridophyte, gymnosperm, and angiosperm species, however, were M = 0.46D4.6 (r2 = 0.99, N = 41), M = 0.07D3.2 (r2 = 0.91, N = 65), M = 0.56D2.2 (r2 = 0.92, N =85), and M = 0.44D1.8 (r2 = 0.97, N = 21), respectively, indicating that the proportionality M Dα3.0. recedes with finer taxonomic resolution. The data for Cooksonia were found to comply with the allometry of Polytrichum when the regression curve of this moss was extrapolated into the size range of the fossil species. Analyses showed that intraspecific allometric scaling factors α were dependent upon the manner in which plant stems taper. Species or portions of branching systems with α >; 4.0 had essentially untapered stems (e.g., Polytrichum commune, Psilotum nudum, twigs of Larix decidua); species with α <; 2.2 had tapered stems resulting from secondary growth in most cases. The evolution of tapered primary stems and secondary growth was interpreted to alter reproductive allometry.

A reconsideration of cf. Psilophyton princeps (Croft & Lang, 1942), a zosterophyll widespread in the Lower Old Red Sandstone of South Wales

EE WARDS, D., KENRICK, P. & CARLUCCIO, L. M., 1988. A reconsideration of cf. P lophyton princeps (Croft & Lang, 1942), a zosterophyll widespread in the Lower Old Rt 1 Sandstone of South Wales. The Lower Devonian plant from Llanover Quarry, Gwent, cal ed cf. Psilophyton princeps, is shown to be a zosterophyll and placed in a new genus. It comprises an ere t planar pseudomonopodial and isotomously branching system of spiny axes with subaxillary pre ections (axillary tubercles) with circinate tips, sometimes replaced by a downwardly directed, spiring, branching axis. Its xylem, strap-shaped in cross-section and exarch, is composed of directly and ndirectly connected annular thickenings. An extended distal fertile zone consists of axes with spot ingia in two opposite or sub-opposite rows. Each sporangium comprises two equal valves, ellip'ical to reniform in face view, and is held upright on a short curved stalk. Dehiscence is around the convex margin which is bordered by a narrow strip of thickening. The Welsh plants are comp ired with other zosterophylls and appear closest to Sawdonia ornata except that they possess sub-axillay branches and lack the characteristic dark-tipped spines. Detailed analysis of coalified mater: and the distribution and fabric of pyrite in permineralizations shows that the original structure of the tracheids was similar to that in Gosslingia and most other zosterophylls, and that the taphonomic processes, with lignified walls preserved as coalified layers and softer tissues replaced by pyrite, were also broadly the same. Permineralizations in pyrite and limonite allow an evaluation of the effects of oxidation of pyrite on original cell structure.

Chemotaxonomy of Some Paleozoic Vascular Plants. Part I: Chemical Compositions and Preliminary Cluster Analyses

The chemical compositions of plant fossils having trimerophyte (Pertica,Psilophyton princeps, P. cf.jorbesii), rhyniophyte (Taeniocrada), and zosterophyll (Sawdonia) morphological characteristics are chemically analyzed and chemotaxonomically related to vascular ( ?Eohostimella, Renalia, Chahuria) and putative non-vascular plant fossils (Botryococcus, Parka, Pachytheca, Prototaxites,Nematothallus, Spongiophyton, Protosalvinia, Orestovia) whose taxonomic affinities are unknown or speculative. Separation of the material examined into clusters representing higher taxa (i.e., algal, nonalgal, trimerophyte, rhyniophyte, zosterophyll plant groupings) is effected by the weighting of chemical data during cluster analyses. The weighting of phenolic and monohydroxycarboxylic acid constituents is shown to cluster vascular plant material, while the criteria of carbon chainlength ranges and maxima separate vascular from non-vascular plant fossils. Multivariate analysis of the data, using chemical and geological factors, results in the clustering of four groups: (1)Botryococcus, Parka, Pachytheca, (2)Spongiophyton, Prototaxites, Nematothallus, Orestovia, (3)Eohostimella,Taeniocrada, Renalia, and (4)Psilophyton spp.,Pertica, Chaleuria. Sawdonia andProtosalvinia appear as data points showing no observable affinity with any of the above fossils.Protosalvinia, Renalia, andChaleuria are interpreted as being chemotaxonomically intermediate. These data are interpreted as indicating taxonomic affinities on a very broad scale ; possible evolutionary trends in specific chemical compounds, as they relate to vascular and non-vascular plant geochemistry, are discussed.

New Fertile Species of Psilophyton from the Devonian of Maine

New Fertile Species of Psilophyton from the Devonian of Maine

A new Devonian species of the genus Cooksonia (Psilophytales)

A new plant species, Cooksonia crassiparietilis, is described from the Lower Devonian of central Kazakhstan. It is found associated with Psilophyton princeps Dawson and Zosterophyllum australianum Cookson and Lang. The species is differentiated from other species of Cooksonia on the basis of sporangium size and wall structure. Forked sporangia are reported. Dehiscence of the sporangia is described as apical and lateral. This report extends the geographic range of the genus. — F. M. Hueber.

On the Occurrence of Psilophyton princeps in the Early Upper Devonian of New York

On the Occurrence of Psilophyton princeps in the Early Upper Devonian of New York

XVII.—Contributions to the Study of the Old Red Sandstone Flora of Scotland. VIII. On Arthrostigma, Psilophyton, and some associated Plant-remains from the Strathmore Beds of the Caledonian Lower Old Red Sandstone

It is well known that there are two distinct horizons in the Caledonian Lower Old Red Sandstone which contain abundant plant-remains (Evans, 1929). At the lower horizon of the Carmyllie and Cairnconnan Beds the flora consists, so far as is clearly known, of Pachytheca, Nematophyton, Parka, and one vascular plant, Zosterophyllum myretonianum (Lang, 1927). In certain greenish-grey flags and sandstones of the Strathmore Beds near the summit of the stratigraphical succession fragmentary plant-remains are abundant along a line stretching from Rosemount, south of Blairgowrie, through Murthly, Glenalmond, Callander, and Balloch, to near Brodick in Arran. From these beds a small but quite distinct assemblage of fossil plants is known. Pachytheca is clearly recorded. The well-defined remains of vascular plants have so far all been referred to Arthrostigma gracile, Dawson, and Psilophyton princeps, Dawson. References to Psilophyton robustius occur, but there is no evidence that the type of plant distinguished from Gaspé under that name has been found in the Strathmore Beds.

VIII. On the spines, sporangia, and spores of Psilophyton princeps , Dawson, shown in specimens from Gaspé

Psilophyton princeps , though still incompletely known, is one of the most important Early Devonian plants, both on account of its morphology and of the place it occupies in the history of investigation of Pre-carboniferous vegetation. It was originally distinguished and described by Dawson from specimens collected in the Gaspé peninsula, Canada. As shown in the restoration, published in the ‘Geological History of Plants’ (DAWSON, 1882), he regarded the plant as consisting of horizontally growing rhizomes, from which sprang erect branch-systems; the branching was dichotomous and the fine distal ramifications terminated in large ovoid sporangia. From the description (DAWSON, 1871) it is clear that the lower portions of the sub-aerial branch-systems were markedly spiny, while the spines, though present, became less numerous and more distant in the distal, fertile regions. The distribution of the spines according to Dawson is not shown in his restoration; it is well illustrated in a modification of Dawson’s restoration by PIA (1926, fig. 109).

On the Cuticular Structure of the Devonian Plant Psilophyton.

Summary An investigation of the cuticle of Psilophyton princeps Dawson from the original locality in Canada has revealed the presence of stomata on the epidermis of the stem. This epidermis resembles in a general wily that of the petrified members of the Psilophytales from the Rhynie Chert, but the stomata differ in the presence of cuticular thickenings and the epidermal cells are usually papillate and not ridged. In the numerical distribution of stomata on the stem, Psilophyton agrees with Asteroxylon rather than Rhynia. There is no evidence that the highly cuticularised spines are homologous with the traumatic intumescences of Rhynia, and they differ from the slightly larger and less spine-like leaves of Asteroxylon, with which a closer comparison is possible, in the absence of stomata.