Pelecypods from the Permian Fort Apache Limestone East of Payson   Updated 9/9/17  Identifying bivalves is always challenging since there are so many similar looking types, and many of them are internal casts which present no outward identifying features as well. Fortunately for us, Stephen Winters of Florida State University in 1963 wrote a landmark memoir for the GSA - Memoir 89 in which he spent years identifying many of the tiny mollusks we were finding in the same formation from 2000 pounds of material he collected at the best localities on the Fort Apache Indian reservation. Recall that off the reservation where the formation starts to thin out considerably, there are virtually no fossils to be found anywhere! This new locality off of the High line Trail we have discovered has many of the same faunal elements as what Winters found, and appears to be nearly as rich as his typical localities. Preparation Limestones were collected on the basis of visible silicified fossils eroding out of the limestones on the surface along the trail. Complete specimens were almost never seen in the field, and many times you had to collect blindly any promising rock. Hauling this out on your backpack was quite unpleasant, however one must keep in mind that THIS locality is one of the rarest in all of Arizona because the Fort Apache Limestone here contains visible fossils. 10% muriatic acid was used to free the specimens, and three sets of sieves were used to separate out the large amount of terriginous material (find sand) from the silicified fossils. The fines were dried and examined under a binocular microscope for specimens.  Numerous specimens were layed out here, a small sample of the hundreds of mollusks collected at this site. Click to Enlarge to full 1290 size  Preservation is poor to moderate to best on the clams. Many are broken or full of wear holes before they were fossilized, and the silica replacement in many cases was not complete leaving many fragile specimens that could not be picked up with tweezers. None the less, several unique species were found. In most of the images below, Ive put a centimeter scale for reference. Type 1 Click to Enlarge to full 1290 size  Palaeonucula levatiformis. The number one most common clam, they ranged in size from extremely tiny - less than 1mm size up to 5mm. Click to Enlarge to full 1290 size  Palaeonucula levatiformis. These are some of the smallest found. Click to Enlarge to full 1290 size  Genus and species indet. Dozens of this type were found in excellent preservation, however Winters did not identify this one. Type 2 Click to Enlarge to full 1290 size  Astartella subquadrata. Another common find, many had excellent detail in the ribbing as seen here. Click to Enlarge to full 1290 size  Astartella subquadrata. Three specimens in various states of preservation. Type 3 Click to Enlarge to full 1290 size  Genus and sp. indet. We found lots of these and many of them were a larger size like this one. Look how sharp the umbo is! Type 4 Click to Enlarge to full 1290 size  Genus and sp. indet. Very few of this one were found, Winters was not able to identify this one. Click to Enlarge to full 1290 size  Bottom side of above specimen. The tooth sockets for valve alignment can be clearly seen despite the small size of this specimen. Type 5 Click to Enlarge to full 1290 size  Parallelodon anaklassium. Rare but stunning with the wing on an elongate trapezoidal shaped shell. Many fragments of this one were found before this magnificent complete specimen was found. Type 6 Click to Enlarge to full 1290 size  Permophorus sp. A very small block shaped clam. This one has no external details but its shape is diagnostic. Click to Enlarge to full 1290 size  Permophorus sp. ? Many of these are internal molds making a definite identification impossible. Type 7 Click to Enlarge to full 1290 size  Bakevellia sulcata. We found a half dozen of this species, after dissolving about 200 pounds of limestone. They are VERY peculiar! Type 8 Click to Enlarge to full 1290 size  Astartella subquadrata. Top side. This one was preserved in a very sparkley quartz with lots of little crystals. Click to Enlarge to full 1290 size  Astartella subquadrata. Bottom side. This one was preserved in a very sparkly quartz with lots of little crystals. Type 9 Click to Enlarge to full 1290 size  Aviculopecten sp. We found this first - and while we knew it appeared to be part of a bivalve, we had no idea what it would have looked like. Click to Enlarge to full 1290 size  Aviculopecten sp. More pieces showed up later in the acid fines. this one is several inches long. Think of this as the outer rim of a large pectin like shell. Click to Enlarge to full 1290 size  Aviculopecten sp. Closer view of above showing unusual tubular turrets. Click to Enlarge to full 1290 size  Aviculopecten sp. Very distorted specimen! Type 10 Click to Enlarge to full 1290 size  Aviculopecten sp. More of a wing from one side. A small collection of assorted pelecypods Click to Enlarge to full 1290 size  Assortment of similar bivalves. This is an example of the largest clams we have found intact in this formation. Paleo HOME