PODS OF VERTEBRATE MATERIAL FROM MOWRY SHALE (CRETACEOUS), UTAH

Several isolated pods of vertebrate material occur along a bedding plane within the Mowry Shale at an outcrop along Highway 191, approximately six kilometers north of Vernal, Utah. The size of the pods varies greatly; the largest encountered pod is 2 x 15 x 10 cm, with the thickest portion at the center. The pods contain teeth, bone and fish scales; they also contain well rounded, fine quartz grains. The overall grain size of most pods is fairly coarse, however, the individual grain sizes range from very coarse to very fine. Additionally, the overall size of teeth and bones in some pods are noticeably larger than teeth and bones in other pods. The pods are compressed and loosely cemented. Most teeth are of teleostean fish origin and are commonly from Enchodus, an alepisauroid teleost. Teleost jaw fragments and vertebral sections are among the most common bones found. Teeth from Carcharias amonensis, a lamniform shark, were also found within a small number of the pods. Some pods contain small phosphatic pebbles which possibly represent teleost microcoprolites.

The origin of these pods is the subject of ongoing research. The pods may represent regurgitates, coprolites, or may simply be piles of material amassed by ocean currents. However, the lack of a cohesive phosphatic groundmass and the high concentration of bony vertebrate material within the pods may rule out the possibility of fecal origin.