THE MAIN KINDS OF FOSSILS 



CHAPTER 3. THE MAIN KINDS OF FOSSILS 



THE PLANT KINGDOM 



General 



The plant kingdom is subdivided into nine phyla and many classes. In Table II and the 

 discussion of the phyla and classes which follows, only groups important in the fossil record 

 are included. Botanists and paleobotanists use a more elaborate classification than this one. 

 Several text books of botany contain good discussions of fossil plants. Fuller and Tippo (1949) 

 and Transeau et al. (1953) are especially recommended. 



Table II. A Classification of the Plant Kingdom 



Phylum Thallophyta (plants lacking distinct roots, stems, and leaves). 



Class Schizophyta (one -celled plants; bacteria) 



Class Algae (seaweeds, pond scum, and diatoms). 



Class Fungi (mushrooms and molds). 

 Phylum Bryophyta (mosses and liverworts). 

 Phylum Pteridophyta (ferns). 



Phylum Arthrophyta (horsetails and scouring rushes). 

 Phylum Lepidophyta (scale trees and club-mosses). 

 Phylum Pteridospermophyta (seed ferns). 

 Phylum Cycadophyta (cycads and their allies). 

 Phylum Coniferophyta (cone-bearing trees, evergreens). 

 Phylum Angiospermophyta (flowering plants). 



Phylum Thallophyta 



This phylum consists of plants of simple structure, without vascular tissue (the tissue 

 that conducts water from one part of the plant to another), whose nature can best be understood 

 by reference to examples, i.e. the bacteria, algae, and fungi. Each of these groups constitutes 

 a class of the Thallophyta, treated separately below. 



CLASS SCHIZOPHYTA. The bacteria are one -celled plants with no hard parts; their 

 fossil record is therefore very scanty. Bacteria are found in the sea, in fresh water, and in 

 other organisms. No bacteria have been recorded from the rocks of Ohio. 



CLASS ALGAE. The class Algae includes the diatoms and the seaweeds and the "pond- 

 scum" of inland waters. These two groups are very different from each other and will be 

 treated separately. 



The diatoms are also one-celled but they secrete a siliceous shell which can be preserved 

 in the rocks. They are very abundant in the sea at present and their shells accumulate in billions 

 as diatom ooze on the bottom of the sea. Ancient diatom ooze is called diatomite and may form 

 deposits many feet thick. The oldest recorded diatoms are Jurassic in age. Diatoms are exclu- 

 sively aquatic and live in both salt and fresh water . They should be found in Pleistocene lake- 

 bed deposits of Ohio, but so far we know of no record of this kind. 



