Christian A. Meyer

Formation and Taphonomy of Human Footprints in Microbial Mats of Present-Day Tidal-flat Environments: Implications for the Study of Fossil Footprints

This study concerns the formation, taphonomy, and preservation of human footprints in microbial mats of present-day tidal-flat environments. Due to differences in water content and nature of the microbial mats and the underlying sediment, a wide range of footprint morphologies was produced by the same trackmaker. Most true tracks are subjected to modification due to taphonomic processes, leading to modified true tracks. In addition to formation of biolaminites, microbial mats play a major role in the preservation of footprints on tidal flats. A footprint may be consolidated by desiccation or lithification of the mat, or by ongoing growth of the mat. The latter process may lead to the formation of overtracks. Among consolidated or (partially) lithified footprints found on present-day tidal flats, poorly defined true tracks, modified true tracks, and overtracks were most frequently encountered while unmodified and well-defined true tracks are rather rare. We suggest that modified true tracks and overtracks make up an important percentage of fossil footprints and that they may be as common as undertracks. However, making unambiguous distinctions between poorly defined true tracks, modified true tracks, undertracks, and overtracks in the fossil record will remain a difficult task, which necessitates systematic excavation of footprints combined with careful analysis of the encasing sediment.

Comparative analysis of Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco): implications for sauropod ichnotaxonomy

Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco) are described and compared. Emphasis is put on track preservation and trackway configuration. The trackways are similar with respect to preservation and the pes and manus track outlines, but they show a large range of trackway configuration. Only one of the trackways reveals digit and claw impressions, and thus differences in trackway gauge and the position of pes and manus tracks are the most explicit characters for their distinction. The Late Jurassic to Early Cretaceous ichnotaxa Brontopodus, Parabrontopodus and Breviparopus are reviewed and a differential diagnosis is given for the trackways studied. The reference trackway of Breviparopus corresponds to one of the studied trackways of Morocco. Parabrontopodus and Breviparopus are considered to be both valid ichnotaxa, even though we recommend the latter to be formally erected based on better-preserved tracks than those currently exposed. The analysed trackways and ichnotaxa suggest that trackway configuration, notably trackway gauge (width), is not decisively influenced by extrinsic factors such as ontogenetic stage, locomotion speed and substrate properties. However, it cannot be excluded that it is related to other factors such as individual behaviour or even sexual dimorphism.

Preliminary Report on the Courtedoux Dinosaur Tracksite from the Kimmeridgian of Switzerland

In 2002 a new dinosaur tracksite was discovered in calcareous laminites of early Late Kimmeridgian age along the future course of the “Transjurane” highway in Courtedoux, Canton Jura, Northern Switzerland. The site has an extraordinary scientific potential, as the laminites, which have been deposited in an intertidal to supratidal environment, contain at least 6 track-bearing levels in a total thickness of about 1 m. The laminites are being systematically excavated by the “Section de paleontologie” over an area of approximately 1500 m2. So far the main track level has been uncovered over an area of about 650 m2, which reveals 2 trackways of theropods and 17 trackways of sauropods. The sauropod tracks are the smallest known in the Kimmeridgian so far, and the trackways belong to the ichnogenus Parabrontopodus, which has been revealed for the first time in Switzerland. The tracksite belongs to the “Middle Kimmeridgian megatracksite” sensu Meyer (2000), and represents the most important dinosaur tracksite in Switzerland, perhaps with the potential for development into one of the worlds largest sauropod tracksites. It will be protected in situ underneath an especially constructed highway-bridge, thus offering opportunities for future research and the development of an interpretative center for education and tourism.

A survey of fossil footprint sites at glen canyon national recreation area (western USA): A case study in documentation of trace fossil resources at a national preserve

Fossil footprints are very widespread in the Late Paleozoic and Mesozoic rocks of eastern Utah, but until recently have not been studied in detail. This is surprising in light of the fact that skeletal remains of fossils in this area are generally rare, whereas footprints are common and very informative about the distribution and behavior of ancient vertebrates. In this report we describe more than three dozen tracksites in the Glen Canyon National Recreation Area (GCNRA) and immediate vicinity, from eight formations (Cedar Mesa, Moenkopi, Chinle, Wingate, Kayenta, Navajo, Summerville, and Morrison) that range in age from Permian through Jurassic. Tracks in the Permian, cf. Anomalopus (or Chelichnus) and Stenichnus, represent at least two types of pre‐archosaurian reptiles, and reveal evidence of predator–prey interaction and digging activity. Footprints in the Moenkopi include a large number of swim traces attributable to amphibians, and horseshoe crabs. Footprints in the Chinle Group include the first e...

A sauropod dinosaur megatracksite from the Late Jurassic of northern Switzerland

The largest known sauropod trackway site from the Upper Jurassic in Europe has been found in the northern Jura Mountains of Switzerland. Since the initial discovery of the site in 1988, detailed ichno‐facies mapping of the sites has been undertaken and completed. Six separate sites (from 5 to 45km apart) have been located to date; the largest one, displaying 345 single imprints, extends over a surface of 7000 m2. As all of the reported sites occur within the same bed, these vertebrate prints form a megatracksite covering an area of more than 360 km2. All localities are stratigraphically within the Reuchenette Formation. Two biostratigraphically diagnostic ammonites have been found within the sequence (Aulacostephanus; Gravesia), indicating an Upper Kimmeridgian age (sensu gallico). In the easternmost sites, imprints occur on mud‐cracked tidal pond deposits, whereas the western tracksites are found in supratidal algal marsh deposits. The track‐bearing horizon is immediately below a trans‐gressive event at ...

Super sizing the giants: first cartilage preservation at a sauropod dinosaur limb joint

Re-examination of the sauropod dinosaur Cetiosauriscus greppini von Huene 1922 (Reuchenette Formation; Kimmeridgian, Late Jurassic) from northwestern Switzerland has revealed a well-preserved cartilage capsule at the distal extremity of the right humerus. The capsule represents hyaline cartilage together with fibrocartilage and can be distinguished by colour, surface structure and histology from the periosteum of the bone. This is the first fossil evidence for articular cartilage in a sauropodomorph dinosaur. It indicates the presence of a large articular capsule on sauropod forelimbs, which was only hypothesized until now, and shows that the forelimb length of sauropods was larger than previously assumed.

Crocodylomorph Trackways from the Jurassic to Early Cretaceous of North America and Europe: Implications for Ichnotaxonomy

Trackways described as Batrachopus (Batrachopodidae Lull, 1904) from the Lower Jurassic of Europe are rare and in some cases different from the type trackways from North America. Differences may be in part attributable to preservation, but current evidence suggests that there is inherent variability in Batrachopodidae morphotypes, beyond that attributable to differential preservation. Type Batrachopus is a stout-toed form, with minimal digit divarication (i.e., a long foot), whereas Antipus describes slender-toed forms with a wider foot and wider digit divarications. Antipus is also similar to Crocodylopodus (ichnofamily Crocodylopodidae: Fuentes Vidarte and Meijide Calvo, 1999) from near the Jurassic-Cretaceous boundary in Spain. Crocodylopodus has a relatively large manus, and a less outwardly rotated trackway, but is not sufficiently different from Batrachopodidae to warrant its own ichnofamily. Manus-pes size (area) ratios (heteropody) may also be important in differentiating different crocodylomorph ichnotaxa, as is the case with other archosaurian ichnotaxa. However, heteropody may change with size, and be less pronounced in large individuals. Manus and pes rotation patterns, and trackway width are variable and may be of use for differentiation of ichnotaxa but may also be a function of speed.

Mechanical implications of pneumatic neck vertebrae in sauropod dinosaurs

The pre-sacral vertebrae of most sauropod dinosaurs were surrounded by interconnected, air-filled diverticula, penetrating into the bones and creating an intricate internal cavity system within the vertebrae. Computational finite-element models of two sauropod cervical vertebrae now demonstrate the mechanical reason for vertebral pneumaticity. The analyses show that the structure of the cervical vertebrae leads to an even distribution of all occurring stress fields along the vertebrae, concentrated mainly on their external surface and the vertebral laminae. The regions between vertebral laminae and the interior part of the vertebral body including thin bony struts and septa are mostly unloaded and pneumatic structures are positioned in these regions of minimal stress. The morphology of sauropod cervical vertebrae was influenced by strongly segmented axial neck muscles, which require only small attachment areas on each vertebra, and pneumatic epithelia that are able to resorb bone that is not mechanically loaded. The interaction of these soft tissues with the bony tissue of the vertebrae produced lightweight, air-filled vertebrae in which most stresses were borne by the external cortical bone. Cervical pneumaticity was therefore an important prerequisite for neck enlargement in sauropods. Thus, we expect that vertebral pneumaticity in other parts of the body to have a similar role in enabling gigantism.

The Dangers of High-Rise Living on a Muddy Seafloor: An Example of Crinoids from Shallow-Water Mudstones (Aalenian, Northern Switzerland)

Abstract A crinoid Lagerstätte of Chariocrinus württembergicus (Opalinuston Formation, Aalenian, Middle Jurassic) was formed under storm conditions. The Lagerstätte is oriented parallel to paleowave crests, and exhumed concretions indicate sediment reworking. Paleoflow was nearly perpendicular to (storm-) wave ripple-crests and was directed towards a depocenter to the south-southeast. Both waves and currents affected crinoid parts, such as stems, and document combined flow conditions. The crinoids lived on a low-relief swell somewhat above storm wave base in a muddy environment, and caused their own in-situ burial. During a storm, wave agitation led to suspension of sediments extending into the habitat of the crinoids. The crinoids provided additional friction within the near-bottom, suspension-rich, agitated water body, thereby reducing the speed of water currents. This led to sediment deposition, and the crinoids were buried in fine-grained sand and silt. In this way, they induced their own burial; therefore, the Lagerstätte is the product of a feedback process. Rapid burial of the crinoids led to their excellent preservation. Articulated preservation is possible only if the flow was too slow to remove the crinoids from their substrate. Some crinoids tried to escape these hostile conditions by autotomizing their crowns, but these were pushed down to the seafloor by oscillatory water movement, and were immediately covered, mouth upward, by sediments. The preserved crowns provide an estimate of the population density in the range of 110 animals m−2, which is a minimum value because some crowns might have been washed away before burial.

The tracks of giant theropods (Jurabrontes curtedulensis ichnogen. & ichnosp. nov.) from the Late Jurassic of NW Switzerland: palaeoecological & palaeogeographical implications

Abstract Jurabrontes curtedulensis, a new ichnogenus and species of Late Jurassic giant theropod dinosaur track is described based on very well-preserved and morphologically-distinct tracks, all carefully excavated along federal highway A16 (Canton Jura, NW Switzerland). All trackways were systematically documented including parameter measurements, descriptions, outline drawings, orthophotos and laserscans. Jurabrontes is characterised by sub-equal track length and width, a small anterior triangle, weak mesaxony, three blunt digits (dII-III-IV) with pronounced (sub)triangular claw marks, a rounded heel, and clear phalangeal pad impressions. The combination of features of Jurabrontes is typical for a theropod (and not ornithopod) trackmaker. Jurabrontes is compared to other similar ichnotaxa and unnamed tracks of large theropods from the Early Jurassic to Late Cretaceous, from which it is clearly different. The sheer size of the largest tracks, that are amongst the largest worldwide and of similar size to Tyrannosauripus from the Late Cretaceous, suggests a ‘megalosaurid’ or large allosaurid theropod as a trackmaker. The presence of such large theropod tracks in tidal-flat deposits of the Jura carbonate platform and associated with small to large sauropod tracks has important palaeoecological implications for the dinosaur community and for palaeoenvironmental and palaeogeographical reconstructions. Jurabrontes - urn:lsid:zoobank.org:act:B482D2AF-637A-4B2D-8B0B-FEAD54CA2A26 J. curtedulensis- urn:lsid:zoobank.org:act:30D45944-5A2B-45E1-89B9-20298E475D51