Fossilization What’s a fossil and how are they formed?
I. Fossilization A. The four types of fossils 1. mold fossils=a fossilized impression made in the substrate - a negative image of the organism.
3. trace fossils = fossilized nests, gastroliths, burrows, footprints, etc. 1. Signs that a living thing was present 4. true form fossils= fossils of the actual animal or an animal part
B. True form and trace fossils 1. True form fossils a. Commonly come from hard parts of the body b. Bones-The fossilized bones of a tremendous number of species of dinosaurs have been found since 1818, when the first dinosaur bone was discovered.
c. Teeth and Claws- a broken tooth of a carnivore is found with another dinosaur's bones, especially those of herbivores. Lots of fossilized teeth have been found, including those of Albertosaurus and Iguanodon
d. Eggs Embryos and Nests- 1. first found in France in 1869 2. over 200 sites 3. nests and clutches of eggs tells much about dinosaurs' nurturing behavior
e. Skin 1. had thick, bumpy skin 2. A 12-year-old girl discovered a T. rex's bumpy skin imprint f. Muscles, Tendons, Organs, Blood Vessels 1. dinosaur "mummies", fossilized imprints of dinosaur skin and other features 2. extremely rare because these soft tissues usually decay
2. Trace Fossils a. Trackways (sets of footprints) - usually made in mud or fine sand - 1500 sites
Fossil footprints have yielded information about: * Speed and length of stride * two or four legs * stalking behavior * existence of dinosaur herds and stampedes * how the tail is carried
b. Toothmarks=generally appear on bones c. Gizzard Rocks = Gastroliths - swallowed stones to help grind their food - Coprolite = fossilized feces * up to 40 cm (16 inches) in diameter
d. Burrows and Nests - considered trace fossils of the animal that laid them