Paleontology in Oregon
Oregon's geologic record extends back approximately 400 million years ago to the Devonian period, before which time the state's landmass was likely submerged under water.
The era's fossils include marine and terrestrial plants, invertebrates, fish, amphibians, turtles, birds, mammals, and traces such as eggs and animal tracks.
By the mid-19th century local fossils had come to the attention of formally trained scientists, and modern research has produced data on climate change and extinction.
[2][3] The state's oldest individual rock is a limestone near Suplee dated to nearly 400 million years ago, during the Devonian period of the Paleozoic era.
[4][6] Fragmentary remains of Permian trilobites, including the endemic species Cummingella oregonensis, have been found in the state's Coyote Butte Formation.
Oregon's fossil flora and fauna track these environmental changes with the addition of species adapted to deeper water or more tropical terrestrial conditions.
[4][10] Additionally, a new genus of basal thalattosaur has been recovered from the Brisbois Member of the Vester Formation in Central Oregon near the community of Suplee.
[11]The breakup of the Pangaean supercontinent during the transition to the Jurassic period created a subduction zone in Oregon's ancient seaway, burying older rock formations and giving way to new volcanic island chains.
[3] Oregon's Jurassic invertebrates, such as the reef-building clam Lithiolus problematicus and the mussel-like Buchia piochii, indicate shallow sea environments similar to those of the state's late Triassic.
[4] Plant fossils from Oregon's Jurassic period show that the terrestrial environment became warmer and wetter, creating swampy conditions.
[1][4] Oregon's islands collided with the Laramidian continent at the end of the Jurassic, creating a new western coastline during the Cretaceous period.
As sea levels rose the Pacific grew to cover more of Oregon's landmass, eventually stopping at the base of a coastal mountain range.
These include species of the fern Dicksonia, cycads Ctenis and Ctenophyllum, conifers Podozamites and Taxites, seeds of the palm Attalea, and the tree-fern Tempskya.
An amateur discovery in 2005, popularly dubbed "Mitchell's Monster," shows that short-necked plesiosaurs roamed the state's Cretaceous seas along with ichthyosaurs.
[1][15] Other sites nearby in Wheeler County have yielded the remains of Oregon's only known pterosaur, attributed to Bennettazhia oregonensis, as well as teeth from the extinct goblin shark Scapanorhynchus.
Only two non-avian dinosaur fossils have been found in Oregon, and both are isolated bones in marine rocks, which evidently bloated and floated out to sea.
One is the pedal phalanx of a large (5 m long) ornithopod, intermediate in size and morphology between Tenontosaurus and Eolambia, from the Early Cretaceous (Albian) Hudspeth Shale near Mitchell, Oregon.
[16][17][18][19] The other is a sacrum fragment, attributable to a hadrosaur similar to Lambeosaurus, recovered from Late Cretaceous (Campanian) sandstones at Cape Sebastian on the southern Oregon coast.
[2][3] Oregon's paleoenvironment in the Cenozoic reflected the era's overall global cooling trend, shifting from tropical to temperate to glacial climates.
Westward shift in the state's shoreline brought a more diverse terrestrial fauna, including a variety of extinct land mammals.
[4] Shark teeth from over a dozen genera have been found at a variety of sites, including the Rocky Point Quarry to the west of the Nehalem River.
[31] The flora included cinnamon, cycads, palms, the primitive sycamore Platanophyllum angustilobus, walnuts, magnolias, figs, grapes, coffee trees, cashews, and bananas.
Later additions included perissodactyls such as Merychippus, Parahippus, Protapirus, and Diceratherium, artiodactyls such as Dromomeryx and Blastomeryx, and proboscids like Gomphotherium and Platybelodon.
[4] Pleistocene megafauna are found across the northern half of Oregon and include such finds as the Tualatin mastodon,[44] the McMinnville mammoth,[45] and the Woodburn Teratornis.
[46] The Willamette Valley Pleistocene Project has reported the discovery of mammoth tracks, attributable to the ichnotaxon Proboscipeda, near the Yamhill River.
[49][50] Tectonic activity associated with the Cascadian Subduction Zone continued throughout the Quaternary, leaving evidence of a series of earthquakes and tsunamis in the past 60 thousand years.
[51][52] At the end of the Last Glacial Maximum, collapse of the ice dam surrounding Lake Missoula initiated a series of large-scale floods that inundated much of the state from 19-13 thousand years ago.
Historian Adrienne Mayor cites as an example the Klamath Tribes of the Modoc, who attributed local fossils to water monsters killed by the mythological figure Coyote.
[50] Edward Drinker Cope, whose rivalry with Marsh spurred the "Bone Wars" of the late nineteenth century, also collected fossils in Oregon.
Recent research from the park includes volcano ecology, radiometric dating, gis applications, systematic paleontology, and mammal paleoecology.
