Brian F. Platt

The Trace-Fossil Record of Vertebrates

SUMMARY: The trace-fossil record of vertebrates contains behavioral evidence of fish, amphibians, reptiles, dinosaurs, mammals, and birds in continental, transitional, and marine paleoenvironments since the Devonian. The study of vertebrate trace fossils includes tracks, trails, burrows, nests, and such feeding traces as bite marks, coprolites, gastroliths, and regurgitalites. Behaviors recorded by these traces include various kinds of (1) locomotion, (2) dwelling, (3) aestivation, (4) breeding and nesting, as well as (5) acts of feeding, which also result in (6) digestion, (7) regurgitation, and (8) defecation. These trace fossils represent the interaction between a vertebrate and a medium, which includes softgrounds, firmgrounds, hardgrounds, plants, and other animals. Humans also have a trace-fossil record, and, like other vertebrates, produce numerous trace fossils that result from different kinds of behavior.

Newly discovered sauropod dinosaur tracks with skin and foot-pad impressions from the Upper Jurassic Morrison Formation, Bighorn Basin, Wyoming, U.S.A.

Abstract A recently discovered dinosaur tracksite from the Upper Jurassic Morrison Formation, Bighorn Basin, Wyoming, contains abundant sauropod tracks that exhibit varying degrees of preservation. Most of these tracks appear as indistinct bulges on the bottoms of sandstone beds, but several are well preserved and show foot-pad and skin impressions. Three track morphotypes are recognized: a sauropod pes print, a Brontopodus-like manus print, and a diplodocid manus print. The Brontopodus-like manus print most likely represents the footprint of a brachiosaur. This morphotype also contains evidence of phalangeal nodes—the first reported for a sauropod manus. The diplodocid manus print is unique because it contains impressions of a substantial ungual on digit I and a heel pad. A partial sauropod track cast also contains an impression of interlocking, polygonal scales. This is only the second known North American sauropod footprint that contains skin impressions. The spectrum of preservational quality of the tracks and associated trace fossils is used to infer the relative moisture content of the original substrate. Moisture content of the original substrate is estimated to have been moist to borderline saturated. Observations of the tracks at the study areas also are used to establish a list of features that can be used to distinguish deep vertebrate tracks from load casts resulting from gravity-induced soft-sediment deformation.

Empirical Determination of Physical Controls on Megafaunal Footprint Formation Through Neoichnological Experiments with Elephants

ABSTRACT We performed a series of neoichnological experiments with elephants to investigate the relationship between the various factors involved in controlling megafaunal footprint formation. Our ultimate goal was to provide a means to calculate original sedimentary properties of fossil-footprint–bearing siliciclastic rocks, especially those containing sauropod dinosaur tracks. Previous semiquantitative and model-based research identified multiple variables that influence footprint creation and preservation, but no rigorous, empirically based models have been constructed. We conducted track-making trials with experimental sediments and one adult female African elephant (Loxodonta africana) and one adult female Asian elephant (Elephas maximus) in a zoo setting. Data collected included track dimensions, sediment particle size distribution, sediment bulk density (&rgr;b), volumetric water content of the sediment (&thgr;v), and trackmaker walking velocity (v) and weight. We performed multiple regression analysis with a backward elimination technique to obtain the following relationship: where Vn is track volume normalized by track length, measured in cm2, &thgr;v is in percent, &rgr;b is measured in g/cm3, and v is measured in m/s. We demonstrate the utility of this equation by calculating the original moisture content of sauropod-track–bearing siltstone and sandstone beds in the Upper Jurassic Morrison Formation. Original water content values are extremely useful for paleoenvironmental and paleohydrological interpretations of sediments and paleosols. Furthermore, paleoclimate studies can benefit greatly from original soil moisture values calculated from megafaunal footprints associated with paleosols.

A NEW SYSTEM FOR DESCRIBING AND CLASSIFYING TETRAPOD TAIL TRACES WITH IMPLICATIONS FOR INTERPRETING THE DINOSAUR TAIL TRACE RECORD

Abstract We introduce new terminology and a new classification scheme for describing tetrapod tail traces, focusing on the interpretation of dinosaur tail traces. Our classification divides tail traces into (1) tail impressions—there is no evidence of forward motion; (2) protracted tail traces—they persist for at least one stride length; and (3) abbreviated tail traces—they persist for less than one stride length. Protracted tail traces are simple or compound, based on the amount of interruption of the tail trace, which we quantify by the percent interruption metric (PIM). Abbreviated tail traces are also simple or compound. Classifications are modified further by sinuosity, which we describe as low or high. The PIM approximates vertical tail motion, and sinuosity approximates lateral tail motion. Sediment variations, preservation, and lateral motion resulting from locomotion must be taken into consideration when interpreting tail traces. This new classification scheme is applied to a partial theropod trackway with associated tail trace from the Upper Jurassic Morrison Formation, Bighorn Basin, Wyoming, United States. The tail trace is protracted and simple with low sinuosity and a low PIM; we interpret this as the result of relatively low tail motion. We hypothesize that significant differences exist between ornithopod and theropod tail trace patterns. We also suggest that protracted tail traces associated with bipedal dinosaur trackways are not the result of the use of the tail as a stabilizing third leg; some may represent incidental contact of the sediment by the tail owing to backward rotation about the pelvis during deceleration.

Burrowing Through the Literature: The Impact of Soil-Disturbing Vertebrates on Physical and Chemical Properties of Soil

Abstract Soil-disturbing vertebrates (SDV) are relatively low in biodiversity and biomass compared with the dominant soil fauna (microorganisms and invertebrates), but they can nevertheless have a great impact on the physical and chemical properties of soils. Our goal is to take an ichnological (organism-substrate interactions)–based approach to review the impacts of SDV on soils; these impacts result in three basic categories of physical structures (traces): subterranean excavations, constructed surficial mounds, and surficial excavations and depressions. We focus on direct rather than indirect effects and frame these in terms of soil additions, losses, translocations, and transformations. We look at publication trends in the SDV literature and graphically summarize examples of maximum reported construction heights, excavation depths, and volumes of soil displacement for various SDV. We then review SDV impacts on soil color, texture, horizonation, structure, bulk density, soil moisture, porosity and permeability, organic matter, pH, cation exchange capacity, and the nutrients Ca, Mg, N, K, P, S, and Si. Translocations are common sources of variation in these properties and may be especially important in creating nutrient-rich patches in otherwise limited landscapes. Common results of SDV activity include destruction of soil structure, decreases in bulk density, and increases in infiltration rates, porosity, and permeability. Additions of excrement and plant material are important sources of organic matter, N, and K. Direct soil losses may occur through geophagy and trampling and wallowing behaviors. Erosion is an important indirect impact often related to killing of surface vegetation from mounding and foraging behaviors.

Quantifying Soil Structure and Porosity Using Three-Dimensional Laser Scanning

Advancements in three-dimensional (3D) digital surface scanning have opened up the possibility of capturing soil morphological information from irregular objects in high resolution. One of these advancements has been the development of a multistripe laser triangulation (MLT) technique that sweeps a series of laser stripes across a surface, while a camera offset from the laser source monitors the deformation and intensity of the reflected laser stripes. MLT scanning can be used to describe soil architecture (i.e., soil structure and porosity) from soil surfaces and soil specimens. The technique allows for the geometry of both small (<1 cm) and large (several meters) objects to be digitally captured in fine detail. In this paper, we provide examples of how MLT scanning has been applied to 3D soil specimens including the determination of bulk density from clods, the quantification of ped geometries, and the development of morphometrics from casted biopores. Examples of soil surface application of MLT scanning include the quantification of soil structure and interpedal pores from the field (excavation walls) and quantification of volume changes and crack formation in the laboratory (soil cores). When combined with other digital morphometric tools such as computed tomography, 3D laser scanning has the potential to quantify the architecture of soils across scales ranging from submicrometers to meters.

Actualistic Studies of the Spatial and Temporal Distribution of Terrestrial and Aquatic Organism Traces in Continental Environments to Differentiate Lacustrine from Fluvial, Eolian, and Marine Deposits in the Geologic Record

Actualistic studies of modern continental environments and the spatial and temporal distribution of terrestrial and aquatic organisms are summarized and synthesized to understand how to better interpret the significance of trace fossils to differentiate lacustrine from fluvial, eolian, and marine deposits in the geologic record. The purpose of this approach is to develop an understanding of the physicochemical factors that control the occurrence, diversity, abundance, and tiering of organism behavior and parallels what is known for benthic and other trace-making organisms in marine environments. The distribution of traces observed in Lake Tanganyika and Lake Eyre, an overfilled lake in a tropical rift basin setting and an underfilled lake in an arid midlatitude ephemeral playa setting, respectively, are described, synthesized, and compared with the Mermia, Coprinisphaera, Termitichnus, Skolithos, and Scoyenia ichnofacies models proposed for continental environments. The comparisons show that all the models are inappropriate for the fluvial-lacustrine settings of Lake Tanganyika and Lake Eyre because the models do not support the environmental uniqueness or distinctive collection of traces across these environments, nor do they provide sufficient interpretive power. The multiple ichnocoenoses for each subenvironment observed in the balanced-filled and underfilled lacustrine systems more accurately record the environmental uniqueness and distinctive collection of traces found in each environment. Ichnocoenoses are better suited for continental depositional systems and their environments because they reflect the nature of processes and distribution of life in continental settings, which are inherently heterogeneous spatially and temporally. Ichnocoenoses also provide sufficient interpretive power for trace-fossil associations formed under different physicochemical conditions for each type of environment. General trends in trace-fossil diversity, abundance, distribution, and tiering are predicted for alluvial (fluvial), lacustrine, and eolian environments so that new models based on the distribution of ichnocoenoses and their sedimentary and pedogenic characteristics from outcrop and core can be constructed.

Experimental Approaches to Understanding Fossil Organisms

Part I Functional Morphology 1. Crinoids Aweigh: Experimental Biomechanics of Ancyrocrinus Holdfasts Roy E. Plotnick and Jennifer Bauer 2. Ultra-elongate freshwater pearly mussels (Unionida): Roles for function and constraint in multiple morphologic convergences with marine taxa Laurie C. Anderson 3. Relationships of Internal Shell Features to Chemosymbiosis, Life Position, and Geometric Constraints within the Lucinidae (Bivalvia) Laurie C. Anderson 4. Modern Analogs for the Study of Eurypterid Paleobiology Danita S. Brandt and Victoria McCoy 5. New Applications for Constrained Ordination: Reconstructing Feeding Behaviors in Fossil Remingtonocetinae (Cetacea: Mammalia) Lisa Noelle Cooper, Tobin L. Hieronymus, Christopher J. Vinyard, Sunil Bajpai, and J.G.M. Thewissen Part II Taphonomy and Environment 6. Patterns in Microbialites Throughout Geologic Time: Is the Present Really the Key to the Past? Kristen L. Myshrall, Christophe Dupraz, Pieter T. Visscher 7 The Relationship Between Modern Mollusk Assemblages and their Expression in Subsurface Sediment in a Carbonate Lagoon, St. Croix, U.S. Virgin Islands Karla Parsons-Hubbard, Dennis Hubbard, Caitlin Tems, and Ashley Burkett 8. Biotic Segregation In An Upper Mesotidal Dissipative Ridge And Runnel Succession, West Salish Sea, Vancouver Island, British Columbia John-Paul Zonneveld, Murray K. Gingras, Cheryl A. Hodgson, Luke P. McHugh, Reed A. Myers, Jesse A. Schoengut, and Bryce Wetthuhn 9. Using X-ray Radiography to Observe Fe distributions in Bioturbated Sediment Murray K. Gingras, John-Paul Zonneveld, and Kurt O. Konhauser 10. Phytoliths as Tracers of Recent Environmental Change Ethan G. Hyland Part III Organism-Substrate Interaction 11. Large Complex Burrows of Terrestrial Invertebrates: Neoichnology of Pandinus imperator (Scorpiones: Scorpionidae) Daniel I. Hembree 12. Biomechanical Analysis of Fish Swimming Trace Fossils (Undichna): Preservation and Mode of Locomotion Maria Cristina Cardonattoand Ricardo Nestor Melchor 13. The Neoichnology of Two Terrestrial Ambystomatid Salamanders: Quantifying Amphibian Burrows Using Modern Analogues Nicole D. Dzenowski and Daniel I. Hembree 14. Biogenic Structures of Burrowing Skinks: Neoichnology of Mabuya multifaciata (Squamata: Scincidae) Angeline Catena and Daniel I. Hembree 15. Novel Neoichnology of Elephants: Nonlocomotive Interactions with Sediment, Locomotion Traces in Partially Snow-Covered Sediment, and Implications for Proboscidean Paleoichnology Brian F. Platt and Stephen T. Hasiotis 16. Burrows and Related Traces in Snow and Vegetation Produced by the Norwegian Lemming (Lemmuslemmus) Dirk Knaust 17. Near-Surface Imaging (GPR) of Biogenic Structures in Siliciclastic, Carbonate, and Gypsum Dunes Ilya V. Buynevich, H. Allen Curran, Logan A. Wiest, Andrew P.K. Bentley, Sergey V. Kadurin, Christopher T. Seminack, Michael Savarese, David Bustos, Bosiljka Glumac, and Igor A.Losev

The foraging pits of the nine-banded armadillo, Dasypus novemcinctus (Mammalia: Xenarthra: Dasypodidae), and implications for interpreting conical trace fossils

The nine-banded armadillo (Dasypus novemcinctus) is a well known burrower, but individuals spend the majority of their time above ground foraging for soil organisms by repeatedly digging pits through the soil surface. Little ichnological attention has been given to these foraging pits even though their great prevalence within the geographic range of extant armadillos implies that they might have a trace fossil record in paleosols extending back to at least the Paleocene. This research describes the foraging pits constructed by D. novemcinctus with implications for recognition and interpretation of similar conical trace fossils. Field observations yielded an association between one large-diameter (41 cm wide) dwelling burrow, three relatively short, straight shelter burrows (up to 19 cm wide and 38 cm long), and abundant variously sized foraging pits (up to 18 cm wide and 14.5 cm deep). Plaster casts of foraging pits showed that most were asymmetrical, vertically oriented, downward-tapering elliptical cones (width>depth), with smooth to coarsely dimpled walls and common elongate, parallel grooves, isolated curved grooves, and distinct paired grooves, resulting from scratching with the elongated middle two digits of the forelimb. Digital models of plaster casts are used to quantify several aspects, including a new property, conicality. Relative compactness and volume exploited indicate that surface pits are more efficient for soil foraging than subterranean burrows. Recognition of fossil armadillo foraging pits would enable paleoenvironmental and paleoclimatic interpretations analogous to the habitats and ranges of extant armadillos. Conical trace fossils in the Upper Jurassic Morrison Formation are potential examples of ancient vertebrate foraging pits, although they are not attributable to armadillos because of their age. Brian F. Platt. Department of Geology and Geological Engineering, University of Mississippi, 120A Carrier Hall, University, Mississippi 38677, USA bfplatt@olemiss.edu

NEOICHNOLOGY OF SEMIARID ENVIRONMENTS: SOILS AND BURROWING ANIMALS OF THE SONORAN DESERT, ARIZONA, U.S.A.

Abstract: Whereas soils in semiarid environments have received considerable attention, specific biogenic structures produced by the plants and animals that inhabit them are less well understood. Soils in a field site in the Santa Catalina Critical Zone Observatory in the semiarid Sonoran Desert of southern Arizona were investigated to develop a model to improve the interpretation of analogous paleosols and associated soil ecosystems in the geologic record. A flat plateau of desert scrubland was divided into thirty-six 4 m2 plots for description and study. Field methods included mapping of soil surfaces, imaging with ground-penetrating radar, casting of open burrows, description of soil trenches, and soil coring. Laboratory methods included analysis of soil bulk geochemistry, clay mineralogy, and thin sections as well as detailed descriptions of burrow casts. Soils included 10–40 cm thick Entisols and Aridisols with blocky peds, pervasive, coarse (3–5 mm) to very fine (< 1 mm) roots, and were dominated by the burrows of ground squirrels and ants, as well as those of various lizards, snakes, scorpions, spiders, centipedes, termites, and insect larvae. Burrow morphologies included small (< 1 cm) to large (> 1 cm) diameter simple vertical shafts, isolated ovoid chambers, subhorizontal tunnels, subvertical to subhorizontal networks of branching tunnels, and complex branching galleries. Bioturbation was concentrated in the upper 20 cm of the soil profile, whereas roots often extended to the base of the profile. Results from this study advance our understanding of the traces produced by different soil organisms and their impact on soil development in modern settings and will be valuable for the interpretation of the paleosols from semiarid environments in the rock record.