32 



OHIO FOSSILS 



Phylum Coniferophyta 



The conifers or evergreens of the present day need no description to characterize them. 

 Usually, their needle-like leaves and seed-bearing cones are distinctive. One group of conifers, 

 most unlike others in habit, is that of the ginkgos which shed their flat, two-lobed leaves (fig. 30) 

 in winter and look very much like hardwood trees. The ginkgos appeared in the late Paleozoic 

 and have continued to the present. They used to be found nearly all over 

 the world but they are scarce now, except as cultivated trees. Ginkgos 

 have been planted as ornamental trees because of their attractive growth 

 form and because they are tolerant of the smoke of large cities. 



Other ancient groups of conifers appearing at the beginning of 

 Mesozoic time are the pines and araucarians. The araucarians are now 

 found only in the southern hemisphere but used to flourish in the western 

 part of this country. Various kinds of fossil conifer wood (spruce and 

 tamarack) are found in Pleistocene deposits in Ohio. Some of these 

 unimpressive logs have helped to determine the exact age of the deposits 

 in which they are found through the use of the radiocarbon technique 

 (see chapter 2). 



Fig. 30 



Older still were the Cordaites (Mississippian to Permian) which were common trees in the 

 late Paleozoic forests of Ohio. Their leaves were large and strap-like and their seeds were 

 loosely arranged in bunches instead of in compact cones. Cordaitean wood, leaves, and seeds 

 have been recorded from the Pennsylvanian of Ohio. 



Phylum Angiospermophyta 



These include the hardwood trees and other true flowering plants. The adaptations found 

 in this group are the most specialized and for this reason they are often regarded as the most 

 advanced of all plants. In all of them the seed is protected inside a closed covering. The 

 Angiosperms became the dominant group of land plants in late Cretaceous time and have con- 

 tinued to increase in numbers and kinds to the present day. The ancestry of the Cretaceous 

 angiosperms still remains one of paleobotany's most perplexing problems. 



Angiosperms of various kinds (wood, leaves, seeds, and pollen) have been found in 

 Pleistocene deposits in Ohio. 



THE ANIMAL KINGDOM 



General 



The animal kingdom is subdivided into many phyla; some of them, e. g. the Arthropoda, 

 contain many kinds of generally familiar animals with an abundant fossil record; others are so 

 scarce and have such a meager fossil record that they are unknown to all but the specialists. 

 In the following table, a few phyla and many classes and orders have been omitted because they 

 are not generally known, have few representatives, and a poor fossil record. 



TABLE III. A CLASSIFICATION OF THE ANIMAL KINGDOM 



Phylum Protozoa: one -celled animals 

 Class Sarcodina: 



Order Foraminifera: Protozoa with many -chambered shells. 



Order Radiolaria: Protozoa with siliceous, unchambered shells. 

 Phylum Porifera: the sponges, many-celled. 

 Phylum Coelenterata: many-celled animals with definite body cavity. 



