ABSTRACT About 17,000 yr ago, Glacial Lake Maumee breached the Fort Wayne Moraine, sending an unimaginably large torrent of meltwater down the upper Wabash River Valley (UWRV). The Maumee Megaflood (MM) may have lasted only a few weeks, but it scoured out a deep trough along the main stem of the river, radically lowering regional base level in what amounts to a geological instant and imposing a strong disequilibrium on a landscape that continues to experience major geomorphic, environmental, and ecological adjustments. In Huntington and Wabash Counties, the central part of the trough is engorged in resistant, Late Silurian reef-associated and inter-reef rocks, producing the largest natural bedrock exposure in heavily glaciated northern Indiana. Unlike the immature, deranged drainage pattern that characterizes most of the glaciated region, streams adjacent to the UWRV form well-integrated drainage networks that exhibit features and processes more typical of high-relief bedrock areas, such as steep fall zones with prominent, lithologically controlled knickpoints, canyons, large terraces, falls and cascades, and a variety of bluff and hillside morphologies and associated groundwater phenomena. The exceptional exposures and diverse landscape of this region have attracted well over a century of interest from geomorphologists and glacial geologists, sedimentologists, stratigraphers, and paleontologists, as well as hydrogeologists, anthropologists, ecologists, and geoscience educators. Among other firsts, the organic origin of fossil reefs in the southern Great Lakes was definitively established in the UWRV, as was the occurrence of convulsive meltwater outbursts during deglaciation of the Laurentide Ice Sheet; likewise, the first direct Mississippi River–Great Lakes connection was also established here by early voyageurs. Today, the region is a popular destination for both nature tourism and history buffs, due in no small part to the burgeoning number of geologically inspired natural areas and historical sites. This field trip traces the MM from its outlet at Fort Wayne, through the bedrock gorge of the upper Wabash River, to the confluence with the late Tertiary Teays Bedrock Valley, with major emphasis on how the depositional framework and diagenetic history of the Late Silurian reef archipelago continue to reverberate in the modern geomorphic response of the valley to Pleistocene events. The first three stops focus on the Wabash-Erie Channel, which acted as the principal outlet of Glacial Lake Maumee and whose underlying geologic characteristics controlled the overall incision history of the MM. Several stops in the Wabash bedrock gorge and Salamonie Narrows will examine the handiwork of this flood, which created the spectacular klintar, or pinnacle-like reefs, of the UWRV, within a landscape that early geomorphologists likened to the scablands of eastern Washington. There, we will see world-class exposures of the fossilized Late Silurian reefs and how their organic framework and diagenesis are controlling the ongoing adjustment of the UWRV landscape and its streams to the convulsive changes imposed by the MM. Stop 9 will showcase the elusive Teays Bedrock Valley and its complex pre-Wisconsin fill, where it converges with the modern river and has been partially exhumed by a major tributary, and offers a study in contrasts between the bedrock-controlled landscapes of earlier stops and an equally steep one excavated entirely into unconsolidated deposits. After a brief stop at the iconic Seven Pillars landmark, the trip concludes at the spectacular Pipe Creek Jr. Quarry, which features several km of tall exposures through the Late Silurian carbonate complex, a late Neogene sinkhole deposit, and the overlying Pleistocene section.

We review the available data on dinosaur life histories and examine the nature and magnitude of physiological, biophysical, and demographic factors that constrained life-history variation in this group. Constraints arise from interdependencies among life-history characteristics and demographic characteristics. After a series of simulation studies of demographically imposed constraints, we conclude that life histories with age of first reproduction more than about 20 years are very unlikely and probably did not exist, even in very large dinosaurs. In a separate set of simulations, we explored the nature and magnitude of physiological and ecological constraints on rates of resource acquisition and assimilation and on allocation of assimilated resources to growth. We find that it is unlikely large hadrosaurs and other large dinosaurs could transduce food into biomass rapidly enough to mature in less than about 5 years and that a more reasonable estimate is around 10 to 12 years. Our conclusions regarding the effects of demographic constraints on life history variation do not depend on mode of temperature regulation in these animals. The results of the simulations of energetic constraints depended only slightly on mode of temperature regulation. An improved model of heat exchange with the environment is presented that is applicable to large animals. In addition, we examined the daily and seasonal dynamics of thermal energy exchange in juvenile and adult hadrosaurs in a simulated Campanian environment. We argue that the impact of constraints arising from nutritional mode (herbivory) on heat-balance models and, hence, on considerations of the suitability of particular environments to animals of particular body size must be considered. Our simulations suggest that adult hadrosaurs of body mass similar to that of Maiasaura could not have remained active throughout the winter in an environment approximated by our microclimate simulation. The most likely response to such an environment would be migration.

Nesting and parental behaviors of modern crocodilians, and ratite and megapode birds are surveyed and reviewed to provide a data base for work on dinosaurian nesting and parental behavior. The modern analogs provide information on prenesting territoriality, mating systems and pair formation, selection of a nest site, construction of the nest, method of incubation, parental attendance of nests, properties of eggs and nests, parental assistance to young at hatching, hatchling vocalization and gregariousness, posthatching parental care, and dispersal of the young. Nest construction for the group includes simple depressions, excavated holes in which eggs are buried, or mound-nests of leaf litter. Incubation temperatures may be maintained passively by nest design and siting, or the temperature may be raised by direct body contact, solar radiation, geothermal heat, fermentation of litter, or a complex combination of several heat sources. Parental behavior is independent of physiology. Ectothermic crocodilians commonly guard nests, assist the young at hatching, and may protect the young after hatching. Some endothermic megapode birds abandon eggs immediately after oviposition. Evidence for dinosaur behavior is equivocal on many points, but data from taphonomy, ichnology, eggs, and nests suggest several behaviors, including: gregariousness by both adults and juveniles; vocal and visual signaling to defend territories, establish hierarchies, and attract mates; egg burial in moist sand or leaf litter; male participation in guarding nests and providing care to young; colonial nesting; parental attendance at nests; pod formation by hatchlings; possibly vocal communication between hatchlings and adults; and possibly parental protection of hatchlings.

A new Early Cretaceous dinosaur locality in the Twin Mountains Formation at Proctor Lake, Texas, reveals information concerning hypsilophodontid social behavior. Both adults and congregations of juvenile hypsilophodontids occur at the site. Recent excavation of one mass of juveniles shows that it occurs in a shallow depression on a paleosol surface. The distribution of skeletal elements and age structure of individuals within congregations may indicate nesting and parental care of the young after hatching. Hypsilophodontids occupied the site over a long period of time, indicating attraction to the area for some reason. The region was a semi-arid flood plain within a lowland valley. Attractive features of the site may have included abundant vegetation and water or protection from predators. The accumulations of juvenile bones may represent attritional mortality of individuals from a single clutch or a succession of clutches in the nest area.

Temperature during incubation determines sex in turtles, crocodiles, and alligators and may have determined the sex of hatchlings in dinosaurs as well. Geologic evidence indicates that dinosaurs nested in upland sites in western Montana where eggs were exposed to fluctuating and/or lower temperatures as climate deteriorated at the end of the Cretaceous. Production of hatchlings of predominantly one sex, due to environmental shifts in nest incubation temperatures resulting from changing climates, would have altered drastically the population breeding structure and driven these dinosaurs toward extinction.

Studies of a complete left pes of the Texas Lower Cretaceous sauropod, Pleurocoelus sp. indet., show—on the basis of the form and size of the elements, particularly the claws—some adaptations for scratch-digging. Four distinct claws are associated with the pedal skeleton, supporting the view that this species was at least one of the Glen Rose trackmakers. Evidence presented here allies Pleurocoelus with the brachiosaurids.

Sauropod dinosaurs have a temporally disjunct distribution in the North American Western Interior during Cretaceous time, here referred to as the sauropod hiatus. Sauropod body and ichnofossils are present in inland basinal and coastal deposits of Aptian-Albian age in Wyoming, Texas, Oklahoma, and Arkansas. Body fossils of sauropods (the titanosaurid Alamosaurus) occur in inland basinal deposits of Maastrichtian age in Texas, New Mexico, Utah, and Wyoming. No sauropods of Cenomanian-Campanian age are known from a Western Interior sedimentary record dominated by coastal deposits and essentially devoid of inland basinal deposits. Dinosaur ichnofaunas from late Albian coastal deposits in New Mexico, Oklahoma, and Colorado lack sauropod footprints, and thus suggest sauropod disappearance from Western Interior coastal environments by the end of Early Cretaceous time. These observations suggest two scenarios: (1) sauropods abandoned Western Interior coastal environments at the end of the Albian, but persisted in Western Interior inland basinal environments throughout Cretaceous time, or (2) sauropods became extinct in the Western Interior at the end of the Albian and reinvaded during the Maastrichtian. Choosing between these scenarios depends on an evaluation of negative evidence. However, the close phylogenetic relationship of Alamosaurus to South American titanosaurids, the absence of sauropod fossils in inland deposits of the Campanian Two Medicine and Judith River Formations, and the availability of a dispersal route between North and South America near the end of Cretaceous time support the second scenario. Thus, sauropods apparently became extinct in the Western Interior near the end of the Albian, then reinvaded from South America during the Maastrichtian but were only able to establish themselves in inland basinal environments. The extinction of sauropods in the Western Interior at the end of Early Cretaceous time may reflect an unrecognized terrestrial extinction coincident with the well-known severe marine extinction caused by a major late Albian regression.

Herbivory in terrestrial vertebrates dates back to at least Early Permian time. Yet herbivorous tetrapods did not greatly diversify until middle Permian and into Triassic time. All of these early herbivores are characterized by isognathy and bilateral occlusion. In the Triassic Period, these herbivores can be differentiated by several trophic-related parameters: simple dentitions (procolophonids, aetosaurs), lack of chewing teeth (dicynodonts), and complex tooth morphology (trilophosaurs, rhynchosaurs, tritylodontoids). In all cases where there is a significant degree of oral processing, masticatory movement is confined to either orthal or palinal motion of the lower jaw. The mechanics of chewing among herbivores changed markedly, beginning in the Late Triassic and extending through the Cretaceous. These animals include sphenodontids, multituberculates, prosauropods, sauropods, segnosaurs, ornithopods, stegosaurs, ankylosaurs, and pachycephalosaurs. Although retaining the primitive isognathous jaw construction and consequent bilateral occlusion, ornithopods were the first group of herbivores to develop a transverse chewing stroke (through slight rotation of the lower jaws [heterodontosaurids] or upper jaws [pleurokinesis: hypsilophodontids, iguanodontids, hadrosaurids]). Measures of diversity, speciation rates, extinction rates, and net profit or loss are used to map shifts in terrestrial floras and theropsid and sauropsid herbivore clades in the Mesozoic. Two linkages appear to exist, one from the end of Triassic and into Jurassic time, and another from the middle to the end of the Cretaceous Period. Each involves both floral restructuring and herbivore community modification.