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Aulacephalodon peavoti
Reconstruction of the skeleton of a dicynodont synapsid, from the Permian of South Africa, on display at the Field Museum of Natural History, Chicago. These large animals with big barrel-shaped trunks are thought to have been herbivores.
GrandMesaLandOLakesViewpointStriations
Glacial striations, Land o' Lakes view on Grand Mesa --- The horizontal scratch marks in this picture were formed as rocks embedded in the bottom of glaciers moved across this bedrock.
Clinostratification
The principle of original horizontality is one of the basic principles of stratigraphy. It states that sediments are deposited in essentially horizontal layers, and it was enunciated already by Steno in his Prodromus (1669, p. 30): "...adeoque strata omnia praeter infimum duobus planis horizontis parallelis contineri" (...all strata, therefore, except the lowest, were bounded by two planes parallel to the horizon). There are, however, exceptions to this principle. Strata can be deposited at an angle when sediment is being transported over a sloping substrate. This occurs, for example on the stoss face of sand dunes, on fluvial bars, or, at an even larger scale, on the front of submerged deltas. This type of stratification is known as "clinostratification" and the inclined layers or laminae are called "foresets." This picture shows nice clinoforms (foresets dipping to the left) overlain by horizontal beds, in the Pennsylvanian Minturn Formation (CO, USA). Backpack for scale, about 50 cm in size.
Tiktaalik roseae
A cast of a famous specimen (about 50 cm in size) of the lobe-finned fish Tiktaalik roseae, from the Devonian of Canada, on display at the Field Museum of Natural History, Chicago. Tiktaalik is often presented as a "missing link" in tetrapod evolution. However, as it often happens, the picture of "sequential transitions" is much more complicated when looked at in detail, with mosaic distribution of characters between various forms.
Normal grading
Normal grading is a type of arrangement of particles in a sedimentary bed, where coarser grains lie at the bottom and finer grains at the top, resulting in a general fining-upward size distribution. Several physical processes can produce normal grading, but most commonly it is indicative of a decrease in the energy of the flow transporting the particles. The bed in the lower half of this picture shows normal grading from microconglomerate angular pebbles to granules to coarse sand at the top. Pennsylvanian Minturn Formation (CO, USA), scale in cm increments.
Lithic tools
A panel on display at the Chicago Field Museum of Natural History, meant to illustrate how the appearance of more complex tool kits signals the emergence of more sophisticated tool-making abilities. However, this general stratigraphic order of appearance is not as clear cut, and tools representing different lithic industries can be found in correlative layers or even in inverted order.
T. rex foot
Compare the foot of this big land vertebrate with the hand of a human... Pretty massive animal, right? Can you guess the species? Well, a T. rex dinosaur, of course! This specimen welcomes you in the foyer of the Denver Museum of Nature and Science, CO, US.
Mass mortality
5 different organisms (a soft-shelled turtle, 3 species of fish, and an insect) are preserved in close proximity on this slab from the Eocene Fossil Lake Basin, Wyoming (on display at the Field Museum of Natural History, Chicago).
SweetwaterRdBigFold
TECTONIC FOLDING: Large fold in gypsum layers, Sweetwater Canyon --- Folding is the result of enormous tectonic forces.
Taniwhasaurus
Replica of the skeleton of a Cretaceous large marine reptile, Taniwhasaurus antarcticus, on display at the Chicago Field Museum of Natural History. Remains of this reptile are found in locations both within the southern and northern hemisphere, illustrating an example of widespread distribution of a fossil type.
Ursus spelaeus
This large-sized extinct bear was a representative of the so-called Pleistocene megafauna. Specimen mounted and on display at the Chicago Field Museum of Natural History.