Carole T. Gee

Biology of the sauropod dinosaurs: the evolution of gigantism

The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability. There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism.

In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection

Sauropod dinosaurs, the dominant herbivores throughout the Jurassic, challenge general rules of large vertebrate herbivory. With body weights surpassing those of any other megaherbivore, they relied almost exclusively on pre-angiosperm plants such as gymnosperms, ferns and fern allies as food sources, plant groups that are generally believed to be of very low nutritional quality. However, the nutritive value of these taxa is virtually unknown, despite their importance in the reconstruction of the ecology of Mesozoic herbivores. Using a feed evaluation test for extant herbivores, we show that the energy content of horsetails and of certain conifers and ferns is at a level comparable to extant browse. Based on our experimental results, plants such as Equisetum, Araucaria, Ginkgo and Angiopteris would have formed a major part of sauropod diets, while cycads, tree ferns and podocarp conifers would have been poor sources of energy. Energy-rich but slow-fermenting Araucaria, which was globally distributed in the Jurassic, was probably targeted by giant, high-browsing sauropods with their presumably very long ingesta retention times. Our data make possible a more realistic calculation of the daily food intake of an individual sauropod and improve our understanding of how large herbivorous dinosaurs could have flourished in pre-angiosperm ecosystems.

The Genesis of Mass Carpological Deposits (Bedload Carpodeposits) in the Tertiary of the Lower Rhine Basin, Germany

Abstract Large, well-preserved carpofloras from Miocene and Pliocene lignite-bearing sequences of the Lower Rhine Basin in Germany occur in a variety of fluvial and lacustrine facies, including channel, point-bar, cut-off channel (oxbow-lake), crevasse-splay, channel-bar (sand-gravel flat), and lake-delta deposits. Despite their occurrence in a wide spectrum of depositional facies, the accumulations share a suite of distinctive characteristics. They appear as a jumble of woody material dominated by abraded pieces of wood, including conifer cones, woody fruits, seeds, small branches, and charcoal in an unconsolidated matrix of medium- or coarse-grained sand. The key characteristic of the fossil plant remains is woodiness. Close association between the lignified material and these grain sizes indicates that these woody fruits are hydrodynamically equivalent to medium- to coarse-sized sand, and were transported as bedload during flood events. Transport by bedload also is evidenced by the high degree of roundness in associated wood clasts, by abrasion in some diaspores, and by the lack of non-resistant plant parts (e.g., leaves, flowers, fleshy or delicate tissues) in the accumulations. Thus, the lignified plant remains behave as sedimentary clasts in the water column, but only after they have been fully saturated with water. Mass carpological accumulations in very coarse-grained sand on active point bars in the Sieg River near Bonn and their formation during events of extreme discharge serve as a modern analog for the fossil carpofloras. New terminology and concepts pertaining to these mass carpological deposits, or “bedload carpodeposits,” also include the terms “bedload carpobiofacies,” and “bedload carpolithofacies.” A basic depositional model for the genesis of bedload carpodeposits is presented.

The mangrove palm Nypa in the geologic past of the New World

The paleontological history of Nypa, known today as the mangrovepalm, is traced through geological time back to the Late Cretaceous. Emphasis is laid on the New World occurrences, especially in NorthAmerica, where Nypa is known from fossil fruits and pollen. In SouthAmerica, the stratigraphic range of this palm extends from theMaastrichtian to the late Eocene, whereas in North America, Nypa isrestricted to only the Eocene. Nypa occurs as pollen all along theAmerican Gulf Coast from the early Eocene (Ypresian) to the late Eocene(Priabonian), while fruit records come from the early and middle Eoceneof Maryland and Texas, respectively. The floristics of these Eocenemangroves, including possible mangrove associates, and the developmentof mangrove vegetation in the neotropics through the Tertiary andQuaternary, are discussed. New paleobotanical evidence from a middleEocene faunal and floral assemblage in Texas, the Casa Blanca flora (LaredoFormation, Claiborne Group), which contains fossil Nypa pollen andfruits, is described in detail.

EXPERIMENTAL SILICIFICATION OF THE TREE FERN DICKSONIA ANTARCTICA AT HIGH TEMPERATURE WITH SILICA-ENRICHED H2O VAPOR

Abstract It is commonly assumed that reactions in the silicification of land plants take place at low to moderate diagenetic temperatures when the solvent for the silica (H2O) is in the liquid stability field. The early Permian forest of Chemnitz, buried by rhyolitic pyroclastic deposits ca. 290 Ma, may be an example of silicification at elevated temperatures above 100 °C by siliceous H2O vapor. Many independent observations support this theory: the presence of low-density (gaseous) inclusions in primary &agr;-quartz, the impregnation and partial replacement of silica phases in the wood by fluorspar, the preservation of relict organic material in the form of the high-temperature mineral anthracite, and the close proximity of the fossil forest to an eruptive center, the Zeisigwald Caldera. We have designed an experimental apparatus that allows silicification to be simulated by silica-bearing H2O vapor. Water was reacted with rhyolitic obsidian at 150 °C for several days to take up silica, then passed through the parenchymatous stem tissue of Dicksonia antarctica in the form of a hot, silica-bearing steam. The reactions taking place in the organic tissue are documented. Amorphous silica gel was found deposited in vapor-treated cells, suggesting that steam can be efficient in transporting aqueous silica species and depositing them into stem tissue. These experiments cannot duplicate every detail found in the natural examples in Chemnitz, but they do underline how important it is to derive the temperature conditions at which the natural silicification reactions took place.

Phylogenetic Analysis of Fossil Water Lilies Based on Leaf Architecture and Vegetative Characters: Testing Phylogenetic Hypotheses from Molecular Studies

Abstract Understanding the phylogenetic diversification of the water lilies (Nymphaeales sensu lato) in deep time is currently on the rise through studies based on both molecular analyses and the fossil record. An enhanced data set of leaf architectural and vegetative characters, for example, was found to be in broad agreement with phylogenies based only on molecular characters. Yet questions remain open regarding the relationships among the genera and subgenera of Nymphaea, the minimum time of divergence of familial and subfamilial clades and the phylogenetic radiation of the nymphaeoids during the Cenozoic that led to the living genera. Here we build on the aforementioned enhanced data set by adding a suite of nine, new or previously studied, Early to Late Cretaceous and Cenozoic fossil leaves to elucidate the phylogenetic positions of the fossil taxa, to test hypotheses based on molecular studies and to resolve phylogenetic relationships within Nymphaeales. In our phylogenetic analysis, five fossil leaf species show strong relationships with Nymphaeaceae and weaker subfamilial relationships to Nymphaea subgenus Lotos and to the Victoria—Euryale clade. Three fossil leaf species have strong relationships to Cabombaceae and are stem taxa. Taken as a whole, these new phylogenetic analyses yield strong evidence for the monophyly of the living families and some subfamilial clades. They also provide support for a divergence of Cabombaceae and Nymphaeceae by the Early Cretaceous. Finally, they suggest that some subfamilial clades of Nymphaeaceae may have originated by the Albian—Cenomanian, at the time of rapid diversification of the early angiosperms.

Greater palaeobiodiversity in conifer seed cones in the Upper Jurassic Morrison Formation of Utah, USA

Although fossil conifer wood, leaves, and pollen have been known from the Upper Jurassic Morrison Formation of the Western Interior of North America for many decades, only a few conifer seed cones have been described as carbonaceous compressions and casts with little internal structure. Recently, however, over 60 silicified seed cones with preserved internal anatomy were amassed by collectors from 11 localities in northeastern and southern Utah and brought to the attention of palaeobotanists. Here we describe the silicified cones from Utah and compare them to one another in size, gross morphology and internal construction. The fossil material is sorted into five new morphotypes of seed cone. Morphotype 1 pertains to Araucariaceae, Morphotype 2 is most likely Pinaceae, and Morphotype 5 is Cheirolepidiaceae. The familial affinity of Morphotypes 3 and 4 cannot be determined at this time. Comparative size analysis based on volume calculations shows that Morphotypes 2, 3, 4 and 5 are extremely small, smaller than any Mesozoic araucarian seed cone, and that Morphotype 1 falls within the range of small fossil araucarian cones. Most cone-bearing localities are situated to the northwest, west, and south of Hanksville in southcentral Utah. With regard to palaeobiodiversity, if Araucaria delevoryasii Gee from Wyoming is included, there are now six morphotypes of seed cones that represent at least three conifer families in Utah and Wyoming. Because many conifers are arborescent and form forests, the new fossil evidence suggests that species-diverse conifer forests or woodlands were a major type of vegetation in the Morrison Formation during the Late Jurassic.

A Volunteer-Powered Dinosaur Excavation in the Upper Triassic of Switzerland

Dinosaurs continue to fascinate the general public and are the best vehicle to attract attention to the earth sciences. While much information on the animals themselves is available to earth science teachers at all levels, there is a need for up-to-date descriptions of dinosaur discovery and excavation. This paper describes a large-scale, volunteer-powered dinosaur excavation in northern Switzerland in 1988. Working with volunteers provided by organizations such as EARTHWATCH to excavate the bonebed is also an aspect of general earth science education as well as an alternative way to do paleontological fieldwork. Our team members were characterized by a high degree of motivation and eagerness to learn, making the dinosaur excavation a paleontologically productive and rewarding teaching experience. The aim of our field campaign at the Frick clay quarry was to gather taphonomic information on a mass accumulation of the prosauropod dinosaur Plateosaurus. A number of such Plateosaurus bonebeds are known from ...