Click here for Section 1. Click here for Section 2.
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THE NACO FORMATION: THE OCEAN FLOOR 300 MILLION YEARS AGO
Exhibit Section 1.
The Naco Formation was formed from a shallow, Upper Pennsylvanian coastal reef, and is about 290-295 million years old. It was then located in warm, shallow water about 15-20 meters deep and about the same distance from the shoreline.
Located in central Arizona at an elevation of about 6000 feet, this reef has done some traveling in 295 million years, including more than a mile straight up!
Brachiopods, Bryozoans, Mollusks, and Corals
Much of the fauna comprising this ancient environment were one of these phyla. While bryozoans and brachiopods are not entirely extinct, they are today very rare. Today, of course, one can see many examples of Mollusks and Corals.
While brachiopods might resemble mollusks at first sight, they are indeed quite different and thus are classified within their own phylum. The drawings below illustrate some of these differences.
Click here for specimen of the above
Illustration from THE FOSSIL BOOK, C.L. Fenton, M.A. Fenton; Doubleday, 1989; pp. 176
Illustration from THE FOSSIL BOOK, C.L. Fenton, M.A. Fenton; Doubleday, 1989; pp. 154
Illustration from A PICTORIAL GUIDE TO FOSSILS, Gerard Case; Van Nostrand Reinhold, 1982; pp. 50
Click on corresponding letters to view specimens of the above.
A C D
Featured here are fossil discoveries made by the Santa Monica Museum of Natural History on the Field Survey Expedition of June, 2000.
Brachiopod Eaten by Carnivorous Gastropod Naco Ftn., Gila County, Arizona In this fossil representing a sea floor during the Upper Pennsylvanian time period, the trail of a Gastropod is evident near the bottom. A Brachiopod, Acanthospirifer occiduus has been split open and eaten. Below and to the left of the Brachiopod is another Brachiopod, Derbyia crassa, and scattered around both specimens are Bryozoans, Polypora spinulifera. Bryozoans Naco Ftn., Gila County, Arizona Brachiopods and a Belemnite Naco Ftn., Gila County, Arizona Brachiopod Showing Pedicle Attachment
Upper Pennsylvanian, about 295-300 million years old.
Brachiopod is 1.1 inches across.
Polypora spinulifera
Upper Pennsylvanian, about 295 million years old.
Specimen on right is about .8 inches high.
Upper Pennsylvanian, about 295 million years old.
Specimen at center is about .9 inches wide.
with Brachiopods
Composita subtilita
Atrypa sp.(Surrounding specimens)
Upper Pennsylvanian, about 295 million years old.
Top Specimen is about .4 inches wide.
Continued in Exhibit Section 2.
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