BAESI

1. November 12, 2011: THE FOSSIL RECORD: Fossils and How They Form Instructor: Jonathan Hendricks Assistant Professor of Paleontology, SJSU, Dept. Geology Email: jonathan.hendricks@sjsu.edu BAESI

2. What Are Fossils? • Fossil: the remains or evidence of life from a previous geological time. • “Fossil” is from the Latin word fossilis, meaning “dug up”. • Remains of past life do not have to have been turned to stone to be fossils!

3. Slide shows two figures. One of a drawing by Gesner of a fossil and modern crab; one of a photograph of Gesner’s fossil crab. Comparison of Fossil and Modern Crab Gesner was the first person to illustrate fossils (1565).

4. Slide shows a fossil shark tooth. “Tongue Stones” Tongues of snakes or dragons?? Figure from: Pimiento C, Ehret DJ, MacFadden BJ, Hubbell G (2010). PLoS ONE 5(5): e10552. doi:10.1371/journal.pone.0010552.g002

5. Key Questions • Are fossils a result of Vis plastica? • Do fossils have an organic origin? • When did they get into rocks? Before or after the rock formed? • What caused them to be petrified?

6. Slide shows a picture of a shark’s tooth and a drawing (by Steno) of a shark’s head, full of teeth. Steno’s Revelation Nicolaus Steno (1631-1687), Danish anatomist. Dissected a shark. Tongue stones look like sharks teeth because they were sharks teeth! How did sharks’ teeth get into rock? Steno’s Revelation: surrounding rock must have been soft when teeth were deposited and later became hardened. Overturned idea that rocks have been exactly the same as we see them today since the earliest days of the creation….

7. Darwin Said…. “For my part, following out Lyell’s metaphor, I look at the geological record as a history of the world imperfectly kept, and written in a changing dialect; of this history, we possess the last volume alone, relating only to two or three countries. Of this volume, only here and there a short chapter has been preserved; and of each page, only here and there a few lines.” -- Darwin (1859)

8. How Good is the Fossil Record? Answer is complex and depends on the question being asked. Most ancient species never left a fossil record. Many species that did leave a fossil record will never be collected or observed. The rock & fossil records areincomplete. Our questions must keep these factors in mind.

9. Two Major Types of Fossils • Two major types of fossils: • Body fossils: Evidence of the morphologies (body forms) of ancient organisms. • Trace fossils: Evidence of the activities of ancient organisms.

10. Slide shows two photographs. One is of a museum drawer full of ammonoid fossils. The other shows a photograph of a T. rex skeleton. Preservation of Body Fossils Fossil record composed mostly of mineralized hard-parts (e.g., shells & bones).

11. Slide shows two photographs. One is of a soft-bodied arthropod from the Cambrian of Utah, showing internal organs. The other is a photograph of a fossil jellyfish from PLoS ONE. Preservation of Body Fossils Fleshy “soft-parts” rarely preserved. Typically preserved only in absence of O2. Fig. 3 from Cartwright P, Halgedahl SL, Hendricks JR, Jarrard RD, Marques AC, et al. (2007) Exceptionally Preserved Jellyfishes from the Middle Cambrian. PLoS ONE 2(10): e1121. doi:10.1371/journal.pone.0001121

12. Slide shows two photographs. One is of permineralized fossil plant remains under a microscope, showing cellular level detail. The other is a photograph of a petrified log from Florissant, CO. Permineralization Petrified wood and many bones have this type of preservation. Empty pore spaces are filled with inorganic material, often silica or calcite. Petrified Wood (Tree Stump)

13. Slide includes two photographs. One shows of snail shells and external molds of snail shells. The other shows an endocast of a mammal brain. Molds and Casts Mold = cavity Cast = filled cavity Body fossils (shells) and external molds (impressions) of shells. Endocast of fossil camel brain.

14. Carbonization Residue of concentrated carbon that remains after other organic remains have been lost. Slide shows photographs of a carbonized fossil plant leaf and insect.

15. Slide shows three figures. One shows mammoth hair. Another shows a frozen mammoth bone. The last shows a figure of elephant relationships based upon DNA extracted from a frozen bone. Unaltered Remains Mammoth hair. Above and lower left iguresfrom Rogaev EI, Moliaka YK, Malyarchuk BA, Kondrashov FA, Derenko MV, et al. (2006) Complete Mitochondrial Genome and Phylogeny of Pleistocene MammothMammuthusprimigenius. PLoSBiol 4(3): e73. doi:10.1371/journal.pbio.0040073 33,000 year old frozen mammoth bone from Siberia

16. Unaltered Fossil Shells with Color Patterns Visible Under UV Light Conusoniscus Cercado Fm. PRI (Loc. TU1230)

17. Slide shows three figures. One is of worm burrows. The other two show dinosaur footprints. Movement Trace Fossils Dinosaur tracks. Worm burrows. Dinosaur track figures from Wilson JA, Marsicano CA, Smith RMH (2009) Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa. PLoS ONE 4(10): e7331. doi:10.1371/journal.pone.0007331

18. Slide shows two photographs of dinosaur coprolites including a large specimen and a microscopic photo taken of a coprolite, showing dissolved bone inside. Digestive Trace Fossils “Coprolite” From USGS.

19. Slide shows two photographs. One shows a drill hole made by a snail on a clam shell. The other shows a scar made by a crab on a snail shell. Predation Trace Fossils Repair scar Drill hole

20. Most Dinosaurs are Known from Only a Few Bones • Slide contains two figures. One shows paintings of recently discovered dinosaurs. The other shows the bones actually discovered from those dinosaurs. Figures from Hocknull et al. (2009) Hocknull SA, White MA, Tischler TR, Cook AG, Calleja ND, et al. (2009) New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia. PLoS ONE 4(7): e6190. doi:10.1371/journal.pone.0006190

21. New dinosaur from Utah. Slide shows two images of Brontomerus: one showing a skeleton highlighting the few bones that were found and the second showing an artists reconstruction of the dinosaur kicking a predatory dinosaur. Brontomerus Taylor, M. P., M. J. Wedel, and R. L. Cifelli. 2009. A New Sauropod Dinosaur from the Lower Cretaceous Cedar Mountain Formation, Utah, USA. ActaPalaeontologicaPolonica 56(1):75-98. 2011  doi: 10.4202/app.2010.0073. “Fig. 1. Skeletal inventory of the camarasauromorphsauropodBrontomerusmcintoshi gen. et sp. nov. from the Lower Cretaceous Cedar Mountain Formation of Utah, in left lateral view. Preserved elements are white, missing elements are reconstructed in gray. After aCamarasaurusgrandis reconstruction kindly provided by Scott Hartman.”