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Representative xenarthran and carnivoran remains from the ZRFS: Megalonyx jeffersonii (A) left lateral view of the skull (DMNH EPV.65000), (B) co-ossi fi ed neural spines of thoracic vertebrae (DMNH EPV.64916) in the left lateral and anterior views; Ursus sp. (C) posterior lumbar vertebra (DMNH EPV.66952) in the lateral and anterior views; Canis sp. (D) anterior thoracic vertebra (DMNH EPV.66953) in the lateral (reversed) and posterior views; Lontra canadensis (E) left humerus (DMNH EPV.61772) in the anterior and lateral views.
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The vertebrate record at the Ziegler Reservoir fossil site (ZRFS) near Snowmass Village, Colorado ranges from ~ 140 to 77 ka, spanning all of Marine Oxygen Isotope Stage (MIS) 5. The site contains at least 52 taxa of macro- and microvertebrates, including one fish, three amphibian, four reptile, ten bird, and 34 mammal taxa. The most common vertebr...
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Context 1
... jeffersonii Desmarest 1822 Jefferson's ground sloth, M. jeffersonii, is represented at the ZRFS by approximately 65 identifiable elements, the majority of which are post-cranial. At present, a minimum of three individuals can be recognized based on recovery of an almost complete skull of an adult, DMNH EPV.65000 (Fig. 5A), and the braincases of two juveniles (DMNH EPV.66950, EPV.66951). Elements referred to M. jeffersonii were widely distributed spatially and stratigraphically across the site, although localized concentrations likely represent associated portions of a single adult individual. However, the non-replication of elements of similar ...
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... canadensis Shreber 1776 A nearly complete and well-preserved left humerus (DMNH EPV.61772) can be referred to the northern river otter, L. canadensis. The specimen is within the size range of extant specimens (DMNH ZM.7392, ZM.7733, ZM.11107), with a strongly arched and moderately twisted shaft (Fig. 5E). The lateral supracondylar ridge is broken but appears to be less developed, and the humeral head is moderately larger, than in extant ...
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... sp. Linnaeus 1758 A posterior lumbar vertebra with a broken neural spine (DMNH EPV.66952) can be referred to Ursus, thus representing the only large carnivoran element from the ZRFS (Fig. 5C). Although the vertebra appears to be from an adult individual, the surface of the centrum suggests that the epiphysis may not have been fused. Morphologically, DMNH EPV.66952 is almost identical to, although slightly smaller than, a lumbar vertebra (DMNH ZM.6900) of a modern Ursus americanus. Most black bears from the latest ...
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... sp. Linnaeus 1758 A complete anterior thoracic vertebra (DMNH EPV.66953) can be referred to Canis and is similar in overall size and morphology (Fig. 5D) to the vertebra of the extant coyote, Canis latrans (e.g., DMNH ZM.10295). It is larger than first thoracic vertebrae of extant foxes (Vulpes spp., Urocyon cinereoargenteus) but smaller than those of dire or gray wolves (Canis dirus, Canis lupus). Therefore, based upon its morphology and size, DMNH EPV.66953 is provisionally assigned ...
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A natural karstic feasure containing remains of the Pre-Pottery Neolithic B period yielded thousands of microvertebrate remains, mainly including small mammals, reptiles and amphbians in nearly equal quantities. Taxonomic and taphonomic considerations combined with comparisons with actualistic and archaeological pitfall trap assemblages from differ...
Citations
... Fossil bearing deposits at ZRFS have been dated from 140 ka to 45 ka ; most of the paleontological materials were recovered from stratigraphic units correlated to Marine Isotope Stage (MIS) 5, also known as the Last Interglacial Period, which has an age range of 130 ka to 80 ka (Emiliani, 1955;1971;Otvos;2014). There are relatively few well-dated vertebrate paleontological sites which date to MIS 5 in North America, and many have less taxonomic diversity Sertich et al., 2014). The high elevation setting of ZFRS (~2705 meters above sea level) is also unique, as the site represents two distinct alpine ecosystems which contain well-preserved remains of vertebrates, invertebrates, and plants Sertich et al., 2014). ...
... There are relatively few well-dated vertebrate paleontological sites which date to MIS 5 in North America, and many have less taxonomic diversity Sertich et al., 2014). The high elevation setting of ZFRS (~2705 meters above sea level) is also unique, as the site represents two distinct alpine ecosystems which contain well-preserved remains of vertebrates, invertebrates, and plants Sertich et al., 2014). ...
... ZRFS was the focus of an edited volume of Quaternary Research , which was a comprehensive review of the geologic, climatic, historical, and biotic elements of the site. The ZRFS mastodons were discussed in two papers (Sertich et al., 2014;Fisher et al., 2014). Mastodons were the most common remains found at the ZRFS, with over 1800 skeletal elements found at the time of publication (Sertich et al., 2014), and 4000 skeletal elements later reported from the site (Cherney et al., 2017). ...
The Ziegler Reservoir fossil site (ZRFS) in Colorado contains over 4000 mastodon bones that date from 140,000 to 100,000 years ago. At an elevation of ~2705 meters above sea level, ZRFS represents an alpine ecosystem dated to Marine Isotope Stage (MIS) 5. Formal descriptions of cheek teeth, mandibles, crania, and femora were completed. Statistical analyses of the upper and lower third molars, including a novel measurement of interloph(id) distances, indicate significant differences between ZRFS mastodons and Mammut pacificus, while falling within the ranges for Mammut americanum. This study agrees with the taxonomic assignment of ZRFS mastodons to Mammut americanum and not Mammut pacificus. Body mass estimates of ZRFS mastodons are between 3451 and 6244 kg, and a niche model indicates elevation and water availability influenced Mammut distribution during MIS 5. Incorporating ZRFS mastodons into large comparative datasets will contribute to ongoing research into Late Pleistocene Mammut.
... Specimens were recovered from a number of localities (contents from auger cores and open-air sites) within San Luis Valley, and the species inhabited varying climatic regimes during the Irvingtonian, ranging from warm and dry interglacial deposits to cool and wet glacial deposition; there was no evidence of neotenic forms (Rogers 1985, Rogers et al. 1992. The Snowmass fossil site produced an astonishing 22,000 Ambystoma (as A. tigrinum) specimens representing over 500 individuals dating from Marine Isotope Stages 6 to 4 (MIS; 141,000 to 55,000 yr BP; Rancholabrean NALMA) and representing glacial through interglacial climatic episodes (Mahan et al. 2014, Sertich et al. 2014). Both terrestrial and neotenic morphologies were recovered from this site, but none were correlated to the various marine isotope stages. ...
... Natural Trap Cave (NTC) in Wyoming (USA) is a rare example of a relatively complete high-altitude megafaunal assemblage of late Pleistocene age ( Fig. 1; e.g., Martin and Gilbert, 1978;Agenbroad and Mead, 1994;Sertich et al., 2014). Although there is no evidence of post-mortem scavenging of skeletal remains, which is consistent with the unlikelihood of survival after a 24 m fall through the only known entrance into the cave, articulated remains are rare due to some degree of hydraulic transport (Wang and Martin, 1993;Lovelace et al., 2022). ...
Zircon crystals from ash layers intercalated with fossil-rich sediment from Natural Trap Cave (NTC) in Wyoming (USA) were investigated to refine the chronostratigraphy of this unique late-Quaternary megafaunal assemblage. Glass compositions of individual glass spicules and glass adherent to zircon along with a characteristic low-δ¹⁸O signature of zircon (on average + 2.4‰ relative to Vienna standard mean ocean water) indicate tephra provenance from post-Lava Creek Tuff activity of Yellowstone. Yellowstone glass composition was hence used to anchor the ²³⁰Th/²³⁸U zircon isochron and to compute model crystallization ages, which translate into maximum depositional ages. For the lowermost visible tephra layer in new excavations in NTC strata, an upper age limit of 138 ± 9 ka (1σ age uncertainty) was thus obtained. A younger tephra with a²³⁰Th/²³⁸U zircon date of 111 ± 8 ka is tentatively correlated with Tuff of Cold Mountain Creek from the Central Plateau Member of Yellowstone, suggesting a minor lag time between zircon crystallization and eruption. The NTC tephra record thus has high potential for refining the explosive volcanic history and tephra distribution patterns of Yellowstone during the late Pleistocene.
... High-resolution stratigraphic and temporal control can limit (but not eliminate) biases, although novel circumstances such as traps and ashfalls can minimize these biases and more faithfully capture signals of local ecology (Rogers and Kidwell, 2007). Many Late Pleistocene fossil localities in North American preserve diverse vertebrate assemblages (Kurtén and Anderson, 1980), and some sites are particularly well known for dense accumulations and/or diversity, for example: Rancho La Brea, CA; the Mammoth Site, SD; and the Ziegler Reservoir fossil site, CO (e.g., Agenbroad and Mead, 1994;Akersten et al., 1983;Sertich et al., 2014). These fossil deposits provide an extraordinary opportunity to answer far ranging questions about the evolution and extinction of local flora and fauna. ...
Excavations at Natural Trap Cave (NTC) began in the mid-1970's and quickly yielded evidence of a diverse steppe fauna that existed during the Last Glacial Maximum (MIS 2) along the western slope of the Bighorn Mountains in north central Wyoming. NTC is a karst pit cave with a 24.5 m vertical drop into a roughly 43 m wide bell-shaped ‘Main Chamber’ and during the course of early excavations a plugged entrance to a fossil-bearing ‘Lower Chamber’ was discovered. Stratigraphic relationships below the entrance to the Main Chamber of the cave were originally studied in the mid-1970's, but were never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analyzed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By leveraging more than 100 radioisotopic dates we developed an age-depth model and chronostratigraphic framework to further interrogate spatiotemporal relationships between strata, paleoenvironmental proxies, and fossil assemblages. Deposition is shown to be discontinuous; sediment accumulation in the study area is restricted to the buildup through peak penultimate and Last Glacial maxima. More recent (<10 ka) Holocene deposits unconformably cover the eroded surface of underlying Pleistocene strata. There is active reworking of sediments with transport and deposition of reactivated material within the Lower Chamber. We note that the two hiatuses coincide with interglacial periods and may reflect changing depositional circumstances within the cave such as extended periods of non-deposition, erosion, or bypass (possibly leading to deposition in the Lower Chamber). Contrary to previous reports, we demonstrate that it is unlikely a prominent snow cone existed or contributed to the pattern of sediment and fossil distribution within the study area, furthermore, we do not observe a continuous Pleistocene-Holocene transition in the study area. Further stratigraphic work will be needed to better understand the interrelationship between Main and Lower chamber deposits and the evolution of sediment accumulation in NTC.
... The late Pleistocene distribution of S. cooperi extended much farther south than the present distribution, reaching at least to San Josecito Cave (elevation 2,256 m) near the town of Aramberri, southern Nuevo León, Mexico (Cushing 1945). A more extensive distribution to the west is suggested by its occurrences at the following sites: Lubbock Lake on the Southern High Plains of Texas (Johnson 1987); Schulze Cave in Edwards County, Texas (Hafner 1993); alluvial terraces along the Colorado River at Austin, Texas (Lundelius 1992); Snowmass Village, Colorado (Sertich et al. 2011); and Dark Spring Cave in southeastern New Mexico (Tebedge 1988, as cited in Morgan and Lucas 2006). Many records point to a distributional retraction during the Pleistocene-Holocene transition (Dalquest and Schultz 1992); however, other records, such as those from Lubbock Lake that date to late Quaternary (about 9,000 years ago -Johnson 1987), indicate that its disappearance from some areas did not occur until beyond that transition. ...
This account represents a thorough update of Mammalian Species 210 on the subject species by A. V. Linzey, incorporating 102 relevant references published since 1983. Synaptomys cooperi Baird, 1857, the southern bog lemming, is an arvicoline rodent. This compact snub-nosed rodent has a thick grayish coat, small eyes and ears, gray or silver venter, and a stubby tail as long as the hind foot. It occurs from Canadian maritime provinces to southeastern Manitoba, southward to Arkansas and northeastern North Carolina. This cold-adapted species lives in mesic grasslands in the Great Plains states, in wet meadows in some eastern states, and often in wet coniferous and other forest types in the north. Its presence often can be detected by distinctive green droppings. One of two species in the genus, S. cooperi is sometimes difficult to capture and study, leading to its status of conservation concern in some states and provinces.
... Species identifications for equid post-crania were determined using a quadratic discriminant analysis implemented in the R statistical computing environment using the package MASS (R Core Team, 2016). Training data used in the analyses are from Sertich et al. (2014) and McHorse et al. (2016). For analysis of the phalanx, training data included Equus occidentalis, E. conversidens, E. lambei, E. scotti, and a northwestern stilt-legged taxon. ...
A paleontological deposit near San Clemente de Térapa represents one of the very few Rancholabrean North American Land Mammal Age sites within Sonora, Mexico. During that time, grasslands were common, and the climate included cooler and drier summers and wetter winters than currently experienced in northern Mexico. Here, we demonstrate restructuring in the mammalian community associated with environmental change over the past 40,000 years at Térapa. The fossil community has a similar number of carnivores and herbivores whereas the modern community consists mostly of carnivores. There was also a 97% decrease in mean body size (from 289 kg to 9 kg) because of the loss of megafauna. We further provide an updated review of ungulates and carnivores, recognizing two distinct morphotypes of Equus , including E . scotti and a slighter species; as well as Platygonus compressus ; Camelops hesternus ; Canis dirus ; and Lynx rufus; and the first regional records of Palaeolama mirifica , Procyon lotor , and Smilodon cf. S . fatalis . The Térapa mammals presented here provide a more comprehensive understanding of the faunal community restructuring that occurred in northern Mexico from the late Pleistocene to present day, indicating further potential biodiversity loss with continued warming and drying of the region.
... How did the ranges of the two species fluctuate in response to environmental shifts throughout the Pleistocene? Apart from specimens of M. pacificus from Idaho, to our knowledge the described mastodon specimens geographically closest to MOR 605 are specimens of M. americanum from northern Utah (Miller, 1987) and northern Colorado (McDonald et al., 2010;Fisher et al., 2014). M. americanum remains from the Wasatch Plateau in Utah (Miller, 1987) and Snowmass in Colorado (Fisher et al., 2014;Mahan et al., 2014;Sertich et Fig. 3 of Railsback et al. (2015). ...
... Apart from specimens of M. pacificus from Idaho, to our knowledge the described mastodon specimens geographically closest to MOR 605 are specimens of M. americanum from northern Utah (Miller, 1987) and northern Colorado (McDonald et al., 2010;Fisher et al., 2014). M. americanum remains from the Wasatch Plateau in Utah (Miller, 1987) and Snowmass in Colorado (Fisher et al., 2014;Mahan et al., 2014;Sertich et Fig. 3 of Railsback et al. (2015). The age data for the first appearance of Bison in North America are from Froese et al. (2017). ...
Mammut pacificus is a recently described species of mastodon from the Pleistocene of California and Idaho. We report the easternmost occurrence of this taxon based upon the palate with right and left M3 of an adult male from the Irvingtonian of eastern Montana. The undamaged right M3 exhibits the extreme narrowness that characterizes M . pacificus rather than M . americanum . The Montana specimen dates to an interglacial interval between pre-Illinoian and Illinoian glaciation, perhaps indicating that M . pacificus was extirpated in the region due to habitat shifts associated with glacial encroachment.
... The equid fossils are mostly phalanges, useful for DNA or dating studies because of their density but generally considered nondiagnostic. We used discriminant analysis, a quantitative approach that has previously led to species-level identification of equid phalanges (Sertich et al., 2014), to identify the Paisley Caves phalanges. We also investigated whether we can distinguish between the two major molecularly supported clades of Pleistocene horses, the stilt-and stout-legged equids. ...
... Bones were identified to species using discriminant analysis, a quantitative tool that uses continuous variables to estimate a series of discriminant functions, which in turn can be used to determine membership in a priori categories. Discriminant analysis on linear dimensions of bones has been successfully used for ecomorphological analysis and taxonomic identification (e.g., Plummer et al., 2008;Hopkins and Davis, 2009;Davis and McHorse, 2013;Sertich et al., 2014). In this procedure, a set of discriminant functions are estimated with reference to a training set of measured specimens of known species (or ecomorphological) identity, then used to predict the identity of unknown specimens given their measurements. ...
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Citation for this article: McHorse, B. K., E. Byrd Davis, E. Scott, and D. L. Jenkins. 2016. What species of horse was coeval with North America's earliest humans in the Paisley Caves? Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1214595.
... Vestal stresses the importance of grasslands within mountain settings, especially at lower elevations, which is further echoed by Andrews(2010:7), who notes the occurrence of bison in mountain settings in historic times as well as during the late Pleistocene and early Holocene. Recent research at a high elevation (2,705 m) Pleistocene lake near Snowmass, Colorado has demonstrated that many more mammalian species were occupying high elevation mountain settings during the late Pleistocene than previously thought(Sertich et al. 2014). At least 34 different mammalian taxa have been identified from this locality thus far, including mastodon, mammoth, camel, bison, sloth, deer, and horse. ...
The terminal Pleistocene represents a dynamic period of environmental flux and resultant extirpation, extinction, and reorganization of biotic communities. Assessment of Clovis and Folsom/Midland artifacts offers an opportunity to address human response to these changing conditions. Clovis sites range in age from ca. 11,590-10,800 RCYBP (13,550-12,850 CALBP) with Folsom technology well expressed from ca. 10,800-10,200 RCYBP (12,800-11,700 CALBP). Although firm radiocarbon assessments of Midland sites are largely lacking, it is suggested Midland technology is a different expression of the same organizational system as Folsom groups. This research outlines environmental change during this dynamic period and develops models of diverse land use strategies between Clovis and Folsom/Midland groups. It is suggested that a small change in adaptive systems can result in noticeable differences in the archaeological record when compounded through redundant activity and time. This change is in part attributed to shifting ecosystems and resource availability of the terminal Pleistocene. Spatial patterning in Clovis and Folsom/Midland artifact distributions, particularly projectile points, preforms, and channel flakes is addressed at a variety of analytical scales in this research. Private artifact collections and isolated artifact discoveries from the Continental Divide of Colorado to the eastern Kansas border are used to characterize Clovis and Folsom/Midland land use and lithic procurement across the Central Great Plains. This research demonstrates that Clovis and Folsom/Midland artifact distributions are not homogenous across the study region, and are influenced by a variety of factors including ground surface visibility and geomorphic filtering, artifact collector activity and research intensity, and diverse land use and resource procurement strategies between Clovis and Folsom/Midland groups.
... Coniferous forest taxa give way to more open-ground vertebrates. Sertich et al. (2014) interpret this as a change from a woodland ecosystem to a more open, tundra ecosystem. ...
Of the 200 beetle species identified from Rocky Mountain Late Pleistocene insect faunal assemblages, 23% are no longer resident in this region. None of the 200 species is extinct. In contrast to this, only 8% of 73 identified mammal species from Rocky Mountain Late Pleistocene assemblages are no longer resident in the Rockies, and 12 species are now extinct. Since both groups of organisms are highly mobile, it would appear that their responses to the large-scale fluctuations of climate associated with the last 125,000 years have been considerably different. Most strikingly contrasting with the insects, there are no mammals in the Rocky Mountain Late Pleistocene fossil record that are found exclusively today in the Pacific Northwest (PNW) region. The PNW does have a distinctive modern mammalian fauna, but only one of these, Keen's Myotis, has a fossil record outside the PNW region, in the eastern and central United States. No modern PNW vertebrate species have been found in any Rocky Mountain fossil assemblages. Based on these data, it appears that there has been little or no mammalian faunal exchange between the PNW region and the Rocky Mountains during the Late Pleistocene or Holocene. This is in stark contrast to the fossil beetle record, where PNW species are a substantial component in many faunas, right through to the Late Holocene.
