Morrison Formation

Abstract: Foreword: tribute to Robert Makela J. R. Horner Preface List of institutional abbreviations Introduction K. Carpenter, K. F. Hirsch, and J. R. Horner Part I. Distribution and History of Collecting: 1. Global distribution of dinosaur eggs, nests and baby skeletons K. Carpenter, and K. Alf 2. The discovery of dinosaur eggshells in nineteenth century France E. Buffetaut, and J. Le Loeuff Part II. Nests: 3. Dinosaur nesting patterns J. Moratalla, and J. Powell 4. Dinosaurian eggs from the Upper Cretaceous of Uruguay G. Faccio 5. Dinosaur egg laying and nesting in France R. Cousin, G. Breton, R. Fournier, and J-P. Watte 6. Late Maastrichtian dinosaur eggs from the Hateg Basin D. Grigorescu, D. Weishampel, D. Norman, M. Seclamen, M. Rusus, A. Baltres, and V. Teodorescu 7. Eggs and nests from the Cretaceous of Mongolia K. Mikhailov, K. Sabath, and S. Kurzanov 8. Comparative taphonomy of some dinosaur and extant bird colonial nesting grounds J. R. Horner 9. Predation of dinosaur nests by terrestrial crocodiles J. Kirkland Part III. Eggs: 10. Upper Jurassic eggshells from the western interior of North America K. F. Hirsch 11. Review of French dinosaur eggshells: eggshell morphology, structure, mineral and organic composition M. Vianey-Liaud, P. Mallan, O. Buscail, and C. Montgelard 12. Dinosaur eggs in China: on the structure and evolution of eggshells Z. Zi-Kui 13. Upper Cretaceous dinosaur eggs and nesting sites from the Deccan volcano-sedimentary province of peninsula India A. Sahni, S. K. Tandon, A. Jolly, S. Bajpai, A. Sood, and S. Srinivasan Part IV. Dinosaur Babies: 14. Life history syndromes, heterochrony, and the evolution of Dinosauria D. Weishampel, and J. R. Horner 15. Dinosaur reproduction in the fast lane: implication for size, success and extinction G. Paul 16. An embryonic Camarasaurus from the Upper Jurassic Morrison formation B. Britt, and B. Naylor 17. Upper Jurassic sauropod babies from the Morrison formation K. Carpenter, and J. McIntosh 18. Thermal travails of ornithopod nestings: implications for endothermy and insulation G. Paul 19. A baby Dryosaurus from the Upper Jurassic Morrison formation of Dinosaur National Monument K. Carpenter 20. An embryo of Camptosaurus from the Brushy Basin Member D. Chure, C. Turner, and F. Peterson 21. Ontogenetic growth of a new species of Hypacrosaurus J. R. Horner, and P. Currie 22. A nodosaurid scuteling from the Texas shore of the Western Interior Seaway L. Jacobs, D. Winkler, P. Murray, and J. Maurice 23. Dinosaur ontogeny and population structure: interpretations based on fossil footprints from North America M. Lockley 24. Summary and prospectus K. Carpenter, K. F. Hirsch, and J. R. Horner Taxonomic Index.

Abstract: The Upper Jurassic Morrison Formation has yielded one of the richest dinosaur faunas of the world. Morrison sediments are distributed over more than a million square kilometers in the western United States and represent a mosaic of riverine, lacustrine and floodplain environments developed on a vast alluvial plain nourished by debris from the ancestral Rocky Mountains. Plant productivity must have been reasonably high to support abundant large-bodied herbivores, but the absence of coals, scarcity of small aquatic vertebrates, the abundance of oxidized sediments, and presence of calcretes lead us to believe that water was periodically in short supply. A strongly seasonal climate may have necessitated annual large-scale movements of large herbivores, accounting in part for their remarkably broad and uniform geographic distribution. Dinosaur diversity is lower in the Morrison than in the Late Cretaceous, and taphonomic alteration is higher. Massed accumulations of thousands of bones are characteristic of the Morrison. Morrison dinosaurs were not confined to specific depositional environments but were distributed across the complete spectrum of available habitats, from lakes to dry floodplains; this type of distribution is similar to that of large terrestrial mammals such as elephants and rhinos and is different from that of hippos and crocodiles. Common Morrison taxa were Camarasaurus, Apatosaurus, Diplodocus, Allosaurus and Stegosaurus; these genera probably constituted a true dinosaur community. Stegosaurus may have been partially segregated from the other genera, and Camptosaurus more strongly so. Camarasaurus and Diplodocus were gregarious, with juveniles and subadults of the former particularly common; Apatosaurus was less abundant and more solitary in its habits. Juveniles and subadults are known for a number of dinosaurs.

Abstract: In late Mesozoic time, the southern Cordilleran foreland basin was bounded on the west by the Sevier thrust belt and on the south by the Mogollon highlands. Paleocurrent indicators in fluvial and fluviodeltaic strata imply sediment delivery into the basin from both tectonic features. Ages of detrital zircons in sandstones of the basin provide insights into the nature of the sediment sources. Upper Jurassic and Lower Cretaceous fluvial strata were deposited as sediment blankets across the width of the basin but Upper Cretaceous marginal-marine facies were restricted to the basin margin, with marine facies in the basin interior. Most Upper Jurassic and Lower Cretaceous fluvial sandstones contain heterogeneous age populations of Precambrian and Paleozoic detrital zircons largely recycled from Jurassic eolianites uplifted within the Sevier thrust belt or antecedent highlands, and exposed as sedimentary cover over the Mogollon highlands, with only minor contributions of Mesozoic zircon grains from the Cordilleran magmatic arc along the continental margin. Sources in Yavapai-Mazatzal Proterozoic basement intruded by anorogenic Mesoproterozoic plutons along the Mogollon highlands were significant for the Westwater Canyon Member of the Upper Jurassic Morrison Formation and for early Upper Cretaceous (Turonian) fluviodeltaic depositional systems, in which arc-derived Cordilleran zircon grains are more abundant than in older and younger units composed dominantly of recycled detritus. Detrital zircons confirm that the Salt Wash and Westwater Canyon Members of the Morrison Formation formed separate foreland megafans of different provenance. Late Upper Cretaceous (Campanian) fluvial sandstones include units containing mostly recycled sand lacking arc-derived grains in the Sevier foredeep adjacent to the Sevier thrust front, and units derived from both Yavapai-Mazatzal basement and the Cordilleran arc farther east, with some mingling of sand from both sources at selected horizons within the Sevier foredeep. Evidence for longitudinal as well as transverse delivery of sediment to the foreland basin shows that paleogeographic and isostatic analyses of thrust-belt erosion, sediment loads, and basin subsidence in foreland systems need to allow for derivation of foreland sediment in significant volumes from sources lying outside adjacent thrust belts.

Abstract: A fossil mammal from the Late Jurassic Morrison Formation, Colorado, has highly specialized teeth similar to those of xenarthran and tubulidentate placental mammals and different from the generalized insectivorous or omnivorous dentitions of other Jurassic mammals. It has many forelimb features specialized for digging, and its lumbar vertebrae show xenarthrous articulations. Parsimony analysis suggests that this fossil represents a separate basal mammalian lineage with some dental and vertebral convergences to those of modern xenarthran placentals, and reveals a previously unknown ecomorph of early mammals.