Showing papers by "Margaret E. Collinson published in 2011"
TL;DR: The geographically widespread records of Molaspora, some species of possibly related Arcellites, and fossil megaspores attributable toregnellidium show that the parent plants of all of these reproductive organs were widely dispersed in the geological past and that the current distribution of Regnellidium—which is restricted to Brazil, Uruguay, and Argentina—is relict.
Abstract: In common with the single extant species of the water fern Regnellidium, Regnellidium diphyllum, megaspores of Eocene and Oligocene representatives of this genus are characterized by having twisted, leaflike folds forming an acrolamella around the triradiate suture. The fossil and modern megaspores also have very similar wall ultrastructure and sculpture, and the morphology of the attached microspores of both is indistinguishable. Specimens of one of the species of the Cretaceous megaspore genus Molaspora—namely, Molaspora lobata, with attached microspores from Spain—and spores in the sporocarp Regnellidium upatoiensis from Georgia, United States, share some characters with those of extant Regnellidium, but the surface ornament of the microspores and the ultrastructure of the megaspore and microspore walls are different. The inner layer of the inner perine of M. lobata megaspores is thinner than the outer layer and of more compact, spongiose construction than that of Eocene and Oligocene Regnellidium spor...
18 citations
TL;DR: In this article, the parent plant groups concerned were more widespread during the Late Cretaceous than previously recognised, and these new records indicate that the parent-plant groups concerned, such as Minerisporites succrassulus and megaspores referable to Parazolla have not been recorded previously from beyond North America, and hitherto only one European occurrence of Ghoshispora has been noted.
15 citations
01 Jan 2011
TL;DR: A growing body of evidence is questioning the selective preservation of resistant biomacromolecules, such as cutan in leaf cuticles; lignin in woods, fruit walls and seed coats; sporopollenin in spores and pollen and algaenan in algal cysts.
Abstract: Selective preservation of resistant biomacromolecules, such as cutan in leaf cuticles; lignin in woods, fruit walls and seed coats; sporopollenin in spores and pollen and algaenan in algal cysts, has previously been invoked in survival of these tissues and organs in the fossil record. A growing body of evidence is questioning this paradigm, suggesting that biomacromolecules may provide the structural template for formation of geomacromolecules in fossils which form as the result of (i) polymerization of labile constituents (e.g. in situ polymerization of cutin, waxes and internal lipids in cuticles; oxidative polymerization incorporating an aliphatic component into sporopollenin), (ii) loss (e.g. loss of cellulose from lignin–cellulose complexes), and (iii) transformation (e.g. lignin methoxyphenols to phenols). Recommended future research directions include: (a) taphonomic experiments to simulate the molecular alteration sequence in diverse environments, (b) analysis of fossils (time series) from a range of depositional settings, and (c) identifying those modern plant organs that lack an expected fossil record. This will require a combination of microscopical and chemical approaches to monitor alteration and understand specific controls on plant preservation.
14 citations
01 Dec 2011
TL;DR: Charcoal is recorded from late Cretaceous sediments of Dinosaur Provincial Park, Alberta, Canada and represents the first documented observations of charcoal at this locality despite over one hundred years of research as mentioned in this paper.
Abstract: Charcoal is recorded from late Cretaceous sediments of Dinosaur Provincial Park, Alberta, Canada and represents the first documented observations of charcoal at this locality despite over one hundred years of research. Abundant charcoal deposits have been recorded throughout the 1.7 million year sediment sequence indicating multiple fire events within this locality. Fire appears to be a major influencing factor within this Cretaceous ecosystem and may have affected the life of the inhabiting dinosaurs. The occurrence of charcoal allows reconstruction of the burned vegetation at multiple locations within Dinosaur Provincial Park. The charcoal assemblage is comprised of gymnosperm wood only, which may be a reasonable representation of the local vegetation; however it could be the result of a taphonomic bias. The absence of additional plant types within the charcoal assemblage may also be due to certain species being preferentially burnt owing to a more fire prone nature.