First records ofCanis dirusandSmilodon fatalisfrom the late Pleistocene Tule Springs local fauna, upper Las Vegas Wash, Nevada

Abstract

Late Pleistocene groundwater discharge deposits (paleowetlands) in the upper Las Vegas Wash north of Las Vegas, Nevada, have yielded an abundant and diverse vertebrate fossil assemblage, the Tule Springs local fauna (TSLF). The TSLF is the largest open-site vertebrate fossil assemblage dating to the Rancholabrean North American Land Mammal Age in the southern Great Basin and Mojave Desert. Over 600 discrete body fossil localities have been recorded from the wash, including an area that now encompasses Tule Springs Fossil Beds National Monument (TUSK). Paleowetland sediments exposed in TUSK named the Las Vegas Formation span the last 250 ka, with fossiliferous sediments spanning ∼100–13 ka. The recovered fauna is dominated by remains of Camelopsand Mammuthus, and also includes relatively common remains of extinct Equusand Bisonas well as abundant vertebrate microfaunal fossils. Large carnivorans are rare, with only Puma concolor and Panthera atrox documented previously. Postcranial remains assigned to the species Canis dirus (dire wolf) and Smilodon fatalis (sabre-toothed cat) represent the first confirmed records of these species from the TSLF, as well as the first documentation of Canis dirus in Nevada and the only known occurrence of Smilodonin southern Nevada. The size of the recovered canid fossil precludes assignment to other Pleistocene species of Canis. The morphology of the felid elements differentiates them from other large predators such as Panthera, Homotherium, and Xenosmilus, and the size of the fossils prevents assignment to other species of Smilodon. The confirmed presence of S. fatalis in the TSLF is of particular interest, indicating that this species inhabited open habitats. In turn, this suggests that the presumed preference of S. fatalis for closed-habitat environments hunting requires further elucidation.

The Las Vegas Formation

“…More recent studies have shown that wetlands in the Las Vegas Valley actually responded to abrupt changes in climate on millennial to submillennial timescales (Springer and others, 2015). These dynamic ecosystems supported a diverse flora and fauna throughout the late Pleistocene (Scott and Springer, 2016;Scott and others, 2017) and are preserved in the geologic record as the deposits distributed along the length of the valley that are, in totality, what Longwell and others (1965) assigned to the Las Vegas Formation.…”

“…2). More recent mapping efforts others, 2011, 2012) and topical studies (Springer and others, 2015;Scott and Springer, 2016;Scott and others, 2017) have not adopted the alloformation approach but instead have augmented and expanded the original stratigraphic and chronologic frameworks of Haynes (1967). Haynes' informal classification (1967) of the deposits of the Las Vegas Formation has persisted for decades.…”

“…In our view, and in the interests of maintaining nomenclatural continuity, it is more sensible and efficacious to expand upon the informal classification of Haynes (1967). Therefore, this study utilizes his original framework, albeit greatly augmented and refined, and includes a hierarchy of informal members and beds based on lithologic characteristics and stratigraphic relations that were employed previously by Scott and Springer (2016), others, 2017, andothers (2017a, b). Our objective is to stabilize the nomenclature and facilitate communication regarding the sediments that make up the Las Vegas Formation, as well as to promote the continued use of these informal units by the scientific community, which will have great utility in future geologic, paleontologic, and climate studies of paleowetland deposits throughout the southwestern United States.…”

“…Tufa also occurs locally within the bed E 1a deposits, appearing as bed load crusts, phytoclasts, and oncoids. Vertebrate fossils are common in this bed and include the only confirmed specimen of Smilodon fatalis (saber-toothed cat) from the Las Vegas Formation (Scott and Springer, 2016).…”

The geology and paleontology of Tule Springs Fossil Beds National Monument, Nevada

“…), and a small stilt-legged species (Haringtonhippus francisci) also lived there during the late Pleistocene, as did Jefferson's ground sloth (Megalonyx jeffersonii) and Shasta ground sloth (Nothrotheriops shastensis). In addition, rare fossils of American lion (Panthera atrox), and new findings of dire wolf (Canis dirus) and saber-toothed cat (Smilodon fatalis), show that carnivores prowled the valley (Scott and Springer, 2016). All of these majestic animals went extinct as the Pleistocene Epoch came to a close.…”