A/ 7 

 Common Fossils of Western New York 



r* i A LJ L L SCIENCES 



Carol A. Heubusch LIBRARY 



Geologist, Buffalo Museum of Science 



Introduction 



There are many people who find a fossil and want to know something 

 about it. This article has been prepared to aid these amateur collectors. 

 Descriptions are limited to the common invertebrate fossils of Western New 

 York although some primitive plants and fishes are found. Many kinds of 

 fossils are not discussed for various reasons: few or no representatives are 

 present locally; there is difficulty in recognizing and identifying some 

 groups; space is lacking to provide necessary detailed descriptions of the 

 numerous classifications. 



What is a Fossil? 



A fossil is some evidence of the existence of a plant or animal which is 

 found preserved in the rocks. To insure preservation, it is necessary that 

 organisms be embedded soon after death in some protective material. Hard 

 parts must be present since soft parts of organisms are rarely preserved. 

 Some sort of alteration of the resistant parts usually occurs, either mineral 

 infiltration of pore spaces or substitution of the original material by mineral 

 matter. The resulting composition of the fossil is often calcium carbonate, 

 the same substance of which the hard parts may be originally composed. 

 Some fossils are composed of silica while others are of chitin, a complex 

 organic substance. Fossils are sometimes preserved as black carbonaceous 

 films on rock. 



Besides the actual remains of animals and plants, any evidences of their 

 former existence are counted among the fossils. Objects indicating the 

 former presence of organisms include casts and molds, trails, tracks, imprints, 

 and burrows. 



Fossils are often not perfectly preserved. They may be crushed or 

 distorted and they are frequently fragmentary. Many fossils can be identified 

 from fragments. 



Fossils are found in almost all the sedimentary rocks of Western New 

 York. The essentially flat-lying layered rocks are composed of sediments 

 once deposited in warm shallow seas covering this area. This occurred 

 mainly during the geologic times of the earth's history called the Devonian 

 and Silurian periods over 300 million years ago. There was a great abund- 

 ance and variety of life in these seas. A small percentage of the animals 

 was preserved in the soft sediments. The sediments consolidated forming 

 rock, the finer grained forming shale and the coarser grained, sandstone. 

 Calcium carbonate was precipitated from the sea water; it settled to the 

 bottom and became limestone. 



Irregularly rounded rocks of various sizes are often mistaken for fossils. 

 These rocks may be concretions which have been formed inorganically by 

 the collection of mineral matter around some nucleus. They may resemble 

 animal bones. Rocks divided into segments by cracks which have been filled 

 with a different rock may be mistaken for fossil turtle shells. 



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