A Preliminary Report on Late Cretaceous Herptiles within or near Bryce Canyon National Park, Utah


Heidi Munk
Department of Geosciences, Weber State University, Ogden, Utah 84408-2507

Abstract—A research project was started in 1997 to determine if the Kaiparowits Formation (Upper Campanian) is present in Bryce Canyon National Park. Previously known localities from beds thought to represent the Kaiparowits Formation were resampled and a new locality has been found in the Wahweap Formation (Lower Campanian) of Campbell Canyon in Bryce Canyon National Park. The herptiles that have been recovered from the Wahweap locality are compared to herptiles recovered from the stratigraphically highest Cretaceous beds of the Paunsaugunt Plateau. The presence of a Late Campanian salamander, Habrosaurus, suggests correlation of the uppermost beds to the Kaiparowits Formation.

Introduction

In an effort to determine if the Kaiparowits Formation (Upper Campanian) is present in Bryce Canyon National Park, I, with the help of a few colleagues, have undertaken an undergraduate research project in Bryce Canyon National Park (beginning in 1997) and on the top of the Paunsaugunt Plateau, in the area of Podunk and Mill creeks, to compare fossils from the Wahweap Formation and from units that have been considered to represent the Kaiparowits Formation by
Eaton (1993) and Eaton et al. (1993) (Figure 1).

Gregory (1951) identified the Kaiparowits Formation as present on the Paunsaugunt Plateau. Bryce Canyon National Park occupies the eastern margin. Subsequent work has challenged Gregory's assessment. Doelling and Davis omit the formation in their 1989 map, as does Bowers in his 1990 map (following the work of Tilton, 1991). Eaton et al. (1993) and Eaton (1993) have, based on both sedimentological and paleontologic data, suggested that at least some of the Kaiparowits Formation may be present on the plateau (and within Bryce Canyon National Park) (Figure 2).

A new locality was recently discovered in the Wahweap Formation of Campbell Canyon within Bryce Canyon National Park (Figure 1). The herptile fossils (lizards, frogs and salamanders) that have been recovered to date from both the uppermost Cretaceous rocks on the Paunsaugunt Plateau and the new locality from the Wahweap Formation will be compared to taxa known from the Kaiparowits Formation. The resulting identifications will be used to help determine the absence or presence of the Kaiparowits Formation on the Paunsaugunt Plateau.



Figure 1—Map of the Paunsaugunt Plateau area showing the major faults, distribution of undifferentiated Cretaceous formations (KU), the Claron Formation (Cl), Tertiary basalts and other volcanics (Tb), Quaternary alluvium (Qa), and the area from which most of the Cretaceous vertebrates have been recovered from the uppermost Cretaceous rocks (indicated by the "1") and from the Wahweap Formation (indicated by the "2") (modified from Eaton, 1993). Bryce Canyon National park boundaries are approximate.


Figure 2—A preliminary interpretation of a generalized section of the Paunsaugunt Plateau (based on Eaton et al., 1993, and Eaton, 1993). Only the stratigraphic position of localities discussed in this report are indicted.

Methods

The field localities were Campbell Canyon in Bryce Canyon National Park and areas near Podunk and Mill creeks on the Paunsaugunt Plateau (Figure 1). We identified possible localities for sampling and collection by examining the ground surface for pieces of jaw, tooth (mammal or fish), bone, scale and/or turtle shell. When fossils were found, we located the producing layer by looking for the highest occurrence of the fossils. We then carefully removed the surface matrix of the layer in question and examine the exposed matrix for any fossils. Samples were shoveled into bags, labeled, and then carried back to base camp for washing. The matrix was then poured into nested double screens for drying in the sun before the first wash. When dry, the double screens were placed in troughs of water for breakdown of the clays and silts by the water. The top screen is a coarse window screen mesh that allows the small fossils to wash through to the bottom screen which is a finer mesh. Large fossils were retained in the upper screen as are any remaining large chunks of matrix. Smaller fossils and pieces of matrix were collected in the finer screen. With gentle agitation of the screens, the clays and silts were washed from both of the screens and into the troughs to prevent redeposition of the finer particles. After each layer of screen had been individually agitated, the screens were placed in the sun to dry. After drying for the second time, the screens were nested and washed again as above. After the second wash and dry, the fine screens were emptied into a common bucket and the coarse screens were emptied into another common but separate bucket. The matrix was then taken to Weber State University (Ogden, Utah) for removal of fossils. The matrix was then spread a little at a time on a picking tray, and then examined under a microscope for fossils. The fossils are removed with tweezers and sorted taxonomically into vials.

Results

At present, the results are few. The concentrated matrix has not been completely picked. There have been few specific identifications of the recovered fossils and this process is currently in progress. The specimens have been grouped into general taxonomic categories (e.g. crocodiles, mammals, fish, etc.). Although herptile jaws are being found, intact specimens are rare. The identifications made here are from jaws that have complete teeth in place and relatively complete vertebrae.

At the newly discovered Campbell Canyon locality (Wahweap Formation) in Bryce Canyon National Park (UMNH VP Loc. 77), teeth have been found representing sharks, rays, crocodiles, fish, mammals as well as jaw fragments of lizards, salamanders and frogs.

Specimen UMNH VP 6992 (NPS accession number 417,
catalogue number 3944) (Figure 3D) has been identified as Order Squamata, Infraorder Scincomorpha, Family Teiidae, Chamops segnis (Keqin and Fox, 1996). The specimen is an incomplete left maxillary. The specimen had six well- preserved tricuspid teeth which show some wear. The teeth are slightly recurved posteriorly with tooth replacement pits at the bases of the teeth.

Specimen UMNH VP 6994 (NPS accession number 417, catalogue number 3946) (Figure 4A,B) is identified as Order Squamata, Infraorder Scincomorpha, Family Scincidae, Subfamily Scincinae, Contogenys sp. There are three complete teeth on the jaw with the bases of three teeth showing through the attached matrix. The cusps of the teeth are flattened on the top.

Specimen UMNH VP 6995 (NPS accession number 417, catalogue number 3947) (Figure 4D) is a jaw fragment identified as Order Caudata, Suborder Ambystomatidae, Family Scapherpetonidae, Scapherpeton sp. The jaw is broken on the labial side so any other distinguishing features of species are missing. There are locations for nine teeth on this specimen.

At UMNH VP locality 61, from the stratigraphically uppermost Cretaceous rocks on the Paunsaugunt Plateau near Mill Creek, bones and teeth representing fish, crocodiles, dinosaurs, turtles and mammals have been found. Herptile fossils include vertebrae and jaw fragments of lizards, frogs, and salamanders. At this locality, specimen UMNH VP 7365 (Figure 4C) was found. The specimen is identified as Class Amphibia, Order Urodela, Family Sirenidae, Habrosaurus sp., a fragmentary tooth plate. The specimen has seven to eight rows of teeth in the fragment.

At UMNH VP locality 83, also representing the stratigraphically uppermost Cretaceous rocks on the Paunsaugunt Plateau near Mill Creek, tooth and bone fragments of hadrosaur and fish have been found. Jaw fragments representing lizards and salamanders were found here along with mammal and crocodile teeth as well as fragments of turtle shell. Gastropods and ostracods are also present at this locality. Present in the material are vertebrae from Class Amphibia, Order Urodela, Family Scapherpetonidae, Lisserpeton sp. (UMNH VP 6986) (Figure 3A-C). Several other similar specimens have also been found. The distinct triangular outline of the atlantes and the half round shape of the centrum are diagnostic of the genus (Estes, 1981). The rib-bearing part of the vertebrae is bicipital. The neural arch is missing from all specimens.

Discussion

The herptile jaws that have been recovered are most often edentulous, but occasionally there are teeth in them. The jaws have been identified to order on the basis of the shape of the jaw and whether it has a tooth bearing ridge (lizards), is continuously rounded with the teeth resting on the rounded lingual surface of the jaw as opposed to the shelf (salamanders). If the jaw is relatively flat with a textured labial side having the small ridges of the teeth then it is from a frog.


Figure 3A-C, Lisserpeton sp. atlas vertebra. D, Chamops sp. UMNH VP 6992. Scale bar = 1 mm..

Figure 4A-C, Lisserpeton sp. atlas vertebra. D, Chamops sp. UMNH VP 6992. Scale bar = 1 mm.

In the picked fragments of bone material from all of the localities discussed above, there are bone fragments that would seem to indicate similar taxa are present in the different localities. The Campbell Canyon locality (Loc. 77), in the Wahweap Formation, is distinctly different from the stratigraphically uppermost Cretaceous beds on the plateau because sharks and rays are present at this locality. Fragments of frogs and salamanders are common to all three localities.

The Habrosaurus specimen (UMNH VP 7365) from UMNH VP locality 61, is important because the salamander is only know from Late Campanian and Maastrichtian rocks (Estes, 1964). The fossil suggests that the uppermost rocks on the plateau are equivalent to the Late Campanian Kaiparowits Formation rather than the Early Campanian Wahweap Formation. The occurrence of Habrosaurus may be a potential marker fossil in the region making biostratigraphic correlation of other localities easier. The other genera discussed above are known to occur from the Santonian to Maastrichtian. Their occurrence over a broad range of time
makes them poor for boistratigraphic correlation.

Conclusion

The presence of the Kaiparowits Formation is suggested by the occurrence of the Late Campanian salamander Habrosaurus (Figure 3C). Identification of the Kaiparowits Formation within Bryce Canyon National Park will influence the way maps of the park are drawn in the future. Our understanding of the environmental history of the park will increase as the fossils from the area help to develop a picture of the area in the Cretaceous. Our understanding of the influence of the Western Interior Seaway on nonmarine rock sequences and animal life of the past will increase with future study.

Acknowledgments

Many thanks to the National Park Service, Richard Bryant and the Bryce Canyon Natural History Association (under the guidance of Gayle Pollack), who have assisted me in my research in Bryce Canyon National Park. The cooperation of the U.S. Forest Service is also appreciated for our work on the top of the plateau. Many thanks also to my mentors, Jeff Eaton and Janet Gillette, without whose guidance I would not have discovered my love of paleontology and the many wonders of Bryce Canyon National Park. Megan Hardman, Judy Wilkinson, Roger Jackman and Angie Nebeker have assisted me in the collection of the fossil bearing matrix. My greatest thanks to George, Davin and Ryan Munk without whose unending support I could have never thought about beginning a project this big, not to mention finishing the project in the future. The Petroleum Research Fund of the American Chemical Society (30989-GB8) and the Bryce Canyon Natural History Association are funding my current work on the plateau.

References

Bowers, W. E. 1990. Geologic map of Bryce Canyon National Park and vicinity, southwestern Utah. U. S. Geological Survey Miscellaneous Investigations Series Map I - 2108.

Doelling, H. H., and F. Davis. 1989. The geology of Kane County, Utah. Utah Geological and Mineral Survey Bulletin 124:1-192.

Eaton, J. G. 1993. Mammalian paleontology and correlation of uppermost rocks of the Paunsaugunt Plateau, southern Utah. In: M. Morales, (ed.), Aspects of Mesozoic geology and Paleontology of the Colorado Plateau. Museum of Northern Arizona Bulletin 59: 163-179.

Estes, R. 1964. Fossil Vertebrates from the late Cretaceous Lance Formation eastern Wyoming. University of California Press, Berkeley and Los Angeles. p. 1-187.

———. 1981. Encyclopedia of Paleoherpetology, Part 2. Gymnophiona, Caudata. Gustav Fischer Verlag. Stuttgart, New York. p. 1-115.

Gregory, H. E. 1951. The geology and geography of the Paunsaugunt Region, Utah: U. S. Geological Survey Professional Paper 226, p. 1-116.

Keqin, G. and R. C. Fox. 1996. Taxonomy and evolution of Late Cretaceous lizards (Reptilia: Squamata) from western Canada. Bulletin of the Carnegie Museum of Natural History. Pittsburgh 33:1-107.

Tilton, T. 1991. Upper Cretaceous stratigraphy of the southern Paunsaugunt Plateau, Kane County, Utah {PH.D. dissertation}. University of Utah, Salt Lake City. p. 1-162.