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Pyrite disks or spindles are sometimes mistaken for fossils of sand dollars or other forms (see marcasite). Cracks, bumps, gas bubbles, and such can be difficult to distinguish from true fossils. Specimens that cannot be attributed with certainty to either fossils or pseudofossils are treated as dubiofossils. Debates on whether specific forms ...
For instance, the conodont Eoplacognathus pseudoplanus has a short range in the Middle Ordovician period. [62] If rocks of unknown age have traces of E. pseudoplanus, they have a mid-Ordovician age. Such index fossils must be distinctive, be globally distributed and occupy a short time range to be useful.
Fossils of organisms' bodies are usually the most informative type of evidence. The most common types are wood, bones, and shells. [57] Fossilisation is a rare event, and most fossils are destroyed by erosion or metamorphism before they can be observed. Hence the fossil record is very incomplete, increasingly so further back in time.
The fossil remains of a juvenile male Mammut americanum (SDNHM 49926) were discovered in stratigraphic layer Bed E, including 2 tusks, 3 molars, 4 vertebrae, 16 ribs, 2 phalanx bones, 2 sesamoids and over 300 other bone fragments. [1] Remains of dire wolf, horse, camel, mammoth and ground sloth were also found. [1]
Fusulinid from the Plattsmouth Chert, Red Oak, Iowa ().Micropaleontology can be roughly divided into four areas of study on the basis of microfossil composition: (a) calcareous, as in coccoliths and foraminifera, (b) phosphatic, as in the study of some vertebrates, (c) siliceous, as in diatoms and radiolaria, or (d) organic, as in the pollen and spores studied in palynology.
Paleodictyon consist of thin tunnels or ridges that usually form hexagonal or polygonal-shaped honeycomb-like network. [1] Both irregular and regular nets are known throughout the stratigraphic range of Paleodictyon, but it is the striking regular honeycomb pattern of some forms such as P. carpathecum and P. nodosum which make it notable and widely studied.
Identified as bones belonging to an extinct horse, the area where the fossils were discovered, called the Hagerman Horse Quarry, was excavated and three tons of specimens were sent back to the Smithsonian in Washington, D.C. [4] Excavation of the fossils continued into the early 1930s.
Fossil of the Ordovician-Silurian tabulate coral Catenipora †Catenipora †Catenipora robusta – or unidentified comparable form †Ceraurinus †Ceraurinus icarus †Cercopyllis †Cercopyllis adolescens – type locality for species †Cercopyllis delicatula – type locality for species †Cercopyllis justiciae – type locality for species