Nautiloids from the Permian Fort Apache Limestone East of Payson

Updated  11/4/17

Lower Permian Nautiloids are found in both the Fort Apache Limestone, and overlying Kaibab formation. Far more commonly found in the Kaibab, they range in size from quarter sized to 12 inch monsters. But in the Fort Apache, we have found so far only two nautiloids in our years of searching. Fortunately, they are both different morphologically and offer an interesting cross section of cephalopod life in the Fort Apache Sea. It is notable that Winters, in his monumental GSA monograph memoir 89 found only the orthocone type and identified it tentatively as Psudorothoceras knoxense.

 Aperture comparison. The differences in similar mollusks can be ascertained by comparing the shapes of the openings. (Aperture) On the left, Bellerophon - a monoplacophoran has a decidedly triangular opening. Center are a gastropod called Knightites sp. which looks very much like a small Bellerophontid, but is a gastropod. And on the right, the cephalopods have a much larger and oval opening, such as the small pea sized specimen we found below.

 This little cutie was found mixed in with our first picks for gastropods out of the acid fines. This was the only one like this, and you can clearly see the septa evenly spaced along its periphery. The center is filled in with sediment thus appears as a mound here hiding the details of the inner whorls.

 The back side is obscured by an urchin spine that was attached to it, but you can still see some of the septa clearly.

 View of the aperture, a bit crushed showing the inner whorls tucking into the opening oh-so-nautiloid style!

 Orthocone nautiloid section found at site 2 as well. This is an orthoceras type cf. Psudorothoceras knoxense. The septa can be seen inside the eroded openings in the outer conch.

 Fortunately, one end has a great view of one of the concave septa. This then would have been the side that the animal lived on in the conch. It is difficult to say how long the original conch was, perhaps 6 inches or so.

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