Lizards (nonophidian squamates) from a vertical series of localities in the early Eocene Wasatch Formation (Washakie Basin, Wyoming, USA) deposited during an interval of global warming are described on the basis of isolated cranial and some postcranial bones. At least 24 species are present. New material supports a close relationship of the iguanid Paranolis to Anolis (to the exclusion of Anolbanolis). Records of Tinosaurus and Scincoideus are the earliest in North America; a potential affinity of the latter, a new species, with Lacertidae is explored. A new species of Palaeoxan tusia and two species related to Neotropical Night Lizards, Lepidophyma, are named. A rhineurid amphisbaenian is present. New material of Apodosauriscus minutus further bolsters the case for its relationship to living Anniella. Glyptosaurine anguids are also present, including new species referred to Xestops, Arpadosaurus, and Glyptosaurus, the last with distinctive crushing posterior teeth. A distinctive new anguimorph lineage, Entomophontes, may be related to Xenosaurus. Considerable cranial material is referred to a new species of Provaranosaurus; we argue that this lineage is closely related to extant Shinisaurus. Restes-like remains are smaller and rare. Helodermatidae is represented by a single osteoderm. The varanid Saniwa is present. The four localities examined here record an interval of warming in the Rocky Mountain interior, when temperatures rose toward their Cenozoic acme in the Eocene Climatic Optimum. Faunal composition shows only two major deviations at a higher taxonomic level, suggesting a prevailing stability. Maximal within-locality species diversity (richness), based on cranial material (18 species), is seen at the top of the section. The diversity difference between the upper and lower part of the section is statistically significant. There is an underlying component of noise to the diversity data with regard to rarer taxa. Diversity changes primarily as a result of dispersal on a local level.

Two new species of Cyprinodon are described, both restricted to saline lakes on a single island in the Bahamas. Both species have unique morphological features and specialized diets that distinguish them from the third Cyprinodon species on San Salvador Island, C. variegatus, and all other pupfishes. Cyprinodon desquamator, n. sp., is a scale-eating specialist with a greatly enlarged lower jaw and elongated body. Cyprinodon brontotheroides, n. sp., is a hard-shelled prey specialist with a protruding nasal region encasing its upper jaw, a unique appendage within Cyprinodontiformes. Both specialist species occur in syntopy with C. variegatus and Gambusia hubbsi in several shallow, hypersaline lakes on San Salvador. Geological age estimates for these lakes place the age of this species flock at 10,000 years or less. Thus, in addition to Laguna Chichancanab, this study describes species within a second remarkable species flock of specialized Cyprinodon pupfishes.

The dinosaur remains from the Upper Cretaceous Lance Formation of Wyoming, USA, have been known since 1870. Most of the fossils that are attributed to theropod dinosaurs are fragmentary skeletons consisting of cranial, axial and appendicular elements, and many isolated teeth are also known. The largest known theropod of the Lance Formation dinosaur fauna is Tyrannosaurus rex. Numerous specimens of this taxon are known from the Maastrichtian strata of the northwestern United States and southwestern Canada. In 1890 and 1892, two pedal phalanges of the left foot and several isolated teeth identified here as belonging to Tyrannosaurus were discovered near Lusk, Wyoming, by John Bell Hatcher and the prospecting party from Yale Univeristy's Peabody Museum of Natural History in New Haven, Connecticut, USA. The discovery of these fossils is significant. One of the first discoveries of Tyrannosaurus from Wyoming, it predates all other discoveries and naming of this taxon in the coeval Hell Creek Formation of Montana, North Dakota and South Dakota, USA, and the Willow Creek and Scollard formations of the province of Alberta, Canada. Additionally, a well-preserved anterior end of the right dentary with teeth discovered in 1947 of a large Tyrannosaurus from the Lance Formation of the Bighorn basin, Wyoming, is described. The discovery of this specimen is also significant, because it is the first occurrence of Tyrannosaurus in the upper coastal plain paleoenvironments located farther inland away from the coastline of the Western Interior Seaway. Previous discoveries of Tyrannosaurus fossil remains from the Lance Formation were from strata deposited near the coastline of the Western Interior Seaway. The discovery of these specimens and their lack of significant morphologic divergence from other specimens of T. rex suggest that this taxon is the only large-bodied theropod that is currently known from the Upper Cretaceous (late Maastrichtian) of northwestern North America.

Placobdella parasitica (Say, 1824) was originally described from lakes of the “North-western region.” Leeches collected during May and June, 2012, from Minnesota, USA, the type locality of Hirudo parasitica Say, 1824, were consistent with P. parasitica (Say, 1824) Moore, 1901 as described by Say (1824). The acquisition of these specimens from the type locality facilitated redescription of P. parasitica. A neotype is designated to stabilize the concept of P. parasitica. In contrast to the papillated members of the genus Placobdella, P. parasitica does not have a confusing and problematic taxonomic history. Placobdella parasitica is differentiated from its congeners by its smooth dorsal surface (or sensillae present), simple (medial unpigmented yellow line) to elaborate (medial and paramedial marbled patches) pigmentation, and ventrum with 8 to 12 stripes. Molecular comparison of CO-I sequence data from P. parasitica revealed differences of 14% from Placobdella multilineata, 14% from Placobdella papillifera, 15% to 17% from Placobdella rugosa, 15% from Placobdella ornata and 16% to 17% from Placobdella ali.