Contributions to Geology 21.1

Gully, scour hole, and pothole development at the base of the Gering Formation (Miocene?), southeastern Banner County, Nebraska

ROBERT F. DIFFENDAL, Jr. Conservation and Survey Division, IANR, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0517

Pages
1-6

Keywords
Arikaree, Gering, Nebraska, paleovalley, stream

Abstract
Several sediment-filled paleovalleys belonging to the Arikaree Group of Miocene (?) age occur in southeastern Banner County, Nebraska. One gully and a main paleovalley exhibit, respectively, erosional features like those in modern gullies in the area and like those on the bedrock floors of modern straight streams carrying an appreciable sediment load. Scour holes and a pothole on the valley floor of the main paleovalley are similar to those produced experimentally on the bed of a straight stream.

Fossil xenosaurid and anguid lizards from the early Eocene Wasatch Formation, southeast Wyoming, and a revision of the Anguioidea

JACQUES A. GAUTHIER Department of Paleontology, University of California, Berkeley, California 94720

Pages
7-54

Keywords
fossil, Eocene, Wasatch, Wyoming, lizards

Abstract
Fossil anguid and xenosaurid lizards are described from the early Eocene Wasatch Formation of Sweetwater County, Wyoming. Four new genera and two new species are named: Restes, Proxestops, Apodosauriscus minutus and Eodiploglossus borealis. Restes is applied to all specimens formerly referred to Exostinus rugosus Gilmore 1942, and Proxestops to a species here resurrected, Peltosaurus jepseni Gilmore 1942. A cladistic analysis is applied to the fossil and Recent species to test hypotheses of the phylogenetic relationships within and between the Anguidae and Xenosauridae.

The monophyly of the Anguimorpha within the Autarchoglossa is corroborated. The Anguioidea McDowell and Bogert 1954 is rejected because there is no evidence that indicates that Xenosauridae and Anguidae are closer to one another than either is to the Varanoidea. Neither the Xenosauridae nor the Anguidae could be derived from one another. The Anguimorpha is composed of three monophyletic taxa whose interrelationships are unresolvedÑthe Xenosauridae, the Anguidae and the Varanoidea.

McDowell and Bogert's (1954) inclusion of the Xenosaurinae and Shinisaurinae in the Xenosauridae is accepted. All fossil and Recent xenosaurids from North America are referred to the Xenosaurinae. Exostinus lancensis Gilmore 1928 is probably generically distinct from E. serratus Cope 1873, as they share only plesiomorphic characters. Restes rugosus is separated from all other xenosaurines by its unique cephalic osteoderms. E. serratus is closer to Recent Xenosaurus than either is to other xenosaurines.

Neither the Anniellinae nor the Anguinae appear to be more closely related to any other anguid subfamily. Glyptosaurines, gerrhonotines and diploglossines appear to be most closely related, and within this group the last two subfamilies are closest. The phylogenetic relationships between the anguid subfamilies, particularly the serpentine forms, are obfuscated by homoplasy and should be tested further.

Owing to the morphology of the earliest and most plesiomorphic annielline, Apodosauriscus minutus, the similarity between Anniella and Anguis is judged to be convergence. This would not, however, preclude the derivation of the Anniellinae from a more primitive anguine. Many of the characters shared by anniellines and anguines are also present in the unrelated diploglossine Ophiodes, which shares similar habits. Thus, it is equally possible that the anniellines could have been derived from an anguid that is unrelated to the Anguinae.

The genus Ophisaurus is a paraphyletic taxon that is based on characters that are plesiomorphic for the Anguinae. From the Oligocene on in Eurasia there are two groups, the gracile, Anguis-like anguines, and the robust, Pseudopus-like anguines. The phylogenetic relationships between these and other Eurasian, North African and North American anguines are unknown. "Ophisaurus" ( = Parapseudopus) hallensis is the plesiomorphic sister taxon of all other anguines, and its inclusion in Ophisaurus by Meszoely and Haubold (1975) was based on plesiomorphy.

Odoxosaurus as constituted by Meszoely 1970 is separated into two genera, Odexosaurus piger (sensu stricto) and Proxestops jepseni. O. piger is the most plesiomorphic glyptosaurine and P. jepseni is the sister taxon of all remaining glyptosaurines. The relationships among the medium-sized glyptosaurines, Xestops spp. and Peltosaurus spp., are problematic, but they are closer to the large glyptosaurines than to O. piger or P. jepseni. The relationships among the large glyptosaurines are not fully resolved. Nevertheless, Melanosaurus and Arpadosaurus are closer to Glyptosaurus, Helodermoides, Eoglyptosaurus and Paraglyptosaurus than to other glyptosaurines, and within this group, the last four genera are closest. The large glyptosaurines may have been ecologically similar to the Iygosomine scincids living in Australia today.

As presently diagnosed, Barisia is a paraphyletic taxon and some of its species, particularly those of the gadovi-imbricata group, may be closer to Abronia. Within gerrhonotines, the moreleti group, the gadovi-imbricata group, and Abronia are closest, and Elgaria is their sister taxon. These taxa, together with Gerrhonotus and Coloptychon, form an unresolved trichotomy within the Gerrhonotinae. Many of the characters that distinguish Abronia from other gerrhonotines may be paedomorphic. Since osteological characters do not yet provide the degree of resolution afforded by scutellation, one should exercise caution in the reference of fossil gerrhonotines to living species groups.

Eodiploglossus borealis is the most plesiomorphic member of the Diploglossinae. As presently defined, Diploglossus and Celestus are paraphyletic taxa. Nevertheless, there appear to be two groups among the Recent diploglossines, a Celestus-Sauresia- Wetmorena group, and a Diploglossus-Ophiodes group. The members of these groups display a remarkable character discordance that indicates that the characters often used in discussions of their relationships are highly constrained.

The remarkable external similarity of some scincids and diploglossines is convergent, rather than a retention of characters of a group that is transitional between other Autarchoglossa and the Anguimorpha. Several equivalent ecomorphs are known in the scincid-cordylid-gerrhosaur group on the one hand and the Anguidae on the other. Perhaps this accounts for the fact that the distributions of these groups are for the most part mutually exclusive.

The intramandibular joints of Varanoidea, Ophidia and Aigialosauria may be functionally equivalent, but they are not morphologically similar. The dentary is supported by the prearticular in aigialosaurs and the surangular in snakes. These bones are progressively reduced from Heloderma to Varanus to Lanthanotus. The specialized intramandibular joint of Lanthanotus reflects modifications associated with fossorial habits rather than increased mobility.

Stratigraphy of the Cretaceous Wayan Formation, Caribou Mountains, southeastern Idaho thrust belt

JAMES G. SCHMITT Department of Geoscience, University of Nevada, Las Vegas, Nevada, 89154
MARY E. MORAN W. K. Summers and Associates, Inc., P. O. Box 684, Socorro, New Mexico, 87801

Pages
55-72

Keywords
Cretaceous, Wayan, Caribou Mountains, Idaho, Phosphoria, Madison

Abstract
Stratigraphic analyses of the lower part of the Lower Cretaceous Wayan Formation in the Caribou Mountains of southeastern Idaho show it to consist of at least 585.6 m of interbedded pebble conglomerate, sandstone, mudrock, limestone, and tuff. Deposition occurred on a meandering stream dominated alluvial plain.

Petrographic studies show Wayan sandstones to be litharenites and feldspathic litharenites. Chert and carbonate rock fragment components of the sandstones were derived primarily from the Permian Phosphoria Formation and Mississippian Madison Formation, exposed in highlands associated with the Paris-Willard thrust system.

Mammalian paleontology of the Fort Union Formation (Paleocene), eastern Rock Springs Uplift, Sweetwater County, Wyoming

GUSTAV F. WINTERFELD Phillips Petroleum Company, 8055 Tufts Avenue Parkway, Denver, Colorado 80237

Pages
73-111

Keywords
Fort Union, mammal, vertebrates, Wyoming, Rock Springs Uplift, fossil

Abstract
A maximum of 549 m (1,800 ft) of exposed sedimentary rock is referred to the Fort Union Formation (Paleocene) on the east-central flank of the Rock Springs Uplift, Sweetwater County, Wyoming. Although the section is well exposed, few paleontological investigations have been done locally. Extensive search during the 1977-1979 field seasons revealed a diverse fauna of fossil vertebrates. These are the first vertebrates described from the formation in the area of the Rock Springs Uplift.

Sedimentary rocks of the local Fort Union Formation unconformably overlie the Lance Formation (latest Cretaceous) and grade upward into the Wasatch Formation (early Eocene). The base of the Fort Union Formation is marked by a conspicuous paleosol horizon and by thick channel sandstones. The eastern-most occurrence of limestone and sandstone-capped cuestas is the most convenient place to mark the uppermost horizons of the local Fort Union Formation.

Fifty-two mammalian species, distributed in nine orders and twenty-four families, were recovered from nineteen new fossil vertebrate localities in the Fort Union Formation. A middle Paleocene (Torrejonian) mammalian assemblage was recovered between the 61 and 87 m (200 and 285 ft) levels. Late Paleocene (Tiffanian) mammals were found above the 180 m (590 ft) level. Mammals characteristic of the Clarkforkian North American land mammal age were not recovered from the area by the author, but are known to be present in the uppermost part of the local Fort Union Formation (Rose, 1981).

Several new species, including three unnamed species of Palaeoryctes (Proteutheria), and unnamed species of Palaeosinopa (Proteutheria), Scenopagus? prouvus (Insectivora), Aletodon conardae (Condylarthra), and Aphronorus ratatoski (? Condylarthra) are described.

Mandibular and maxillary teeth of Chiromyoides caesor (Primates) are described for the first time. An excellent sample of Litomylus ishami (Condylarthra) was recovered and is discussed in reference to the origin of the genus Aletodon (Condylarthra). "Mckennatherium" and ''Diacodon minutus" are considered junior synonyms of Adunator.