Joshua X Samuels

Joshua X Samuels
East Tennessee State University | ETSU · Department of Geosciences

PhD

About

57
Publications
13,977
Reads
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1,195
Citations
Citations since 2017
36 Research Items
835 Citations
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Introduction
My research to date has mainly focused on the paleoecology and evolution of mammals, primarily rodents and carnivorans, as well as systematics and biostratigraphy. I am very interested in understanding the responses of animals to past climate and habitat changes. Much of my current research is focused on the Gray Fossil Site in Tennessee and the Cenozoic fossil record of the John Day Basin in Oregon.
Additional affiliations
January 2010 - July 2016
National Park Service
Position
  • Museum Curator / Chief of Paleontology
February 2008 - June 2009
University of California, Los Angeles
Position
  • PostDoc Position
Description
  • NSF funded research in the lab of Blaire Van Valkenburgh, examining mammalian nose anatomy and turbinate structure. Duties involved reconstruction and analysis of carnivoran turbinates using 3D CT scan data.
Education
September 2001 - December 2007
University of California, Los Angeles
Field of study
  • Evolutionary Biology

Publications

Publications (57)
Article
Full-text available
Living rodents show great diversity in their locomotor habits, including semiaquatic, arboreal, fossorial, ricochetal, and gliding species from multiple families. To assess the association between limb morphology and locomotor habits, the appendicular skeletons of 65 rodent genera from 16 families were measured. Ecomorphological analyses of various...
Article
Rodents are important components of nearly every terrestrial ecosystem and display considerable ecological diversity. Nevertheless, a lack of data on the ecomorphology of rodents has led to them being largely overlooked in palaeoecological reconstructions. Here, geometric and linear morphometrics are used to examine how cranial and dental shapes re...
Article
Full-text available
The John Day Formation of Oregon is one of the richest and best studied assemblages in North America. Including seven members and spanning about 20 million years, there are over 150 vertebrate species known from the John Day Formation. The rodent faunas of John Day have not been as well studied as larger mammals, with many families having received...
Article
Through the Cenozoic, paleoclimate records show general trends of global cooling and increased aridity, and environments in North America shifted from predominantly forests to more open habitats. Paleobotanical records indicate grasses were present on the continent in the Eocene; however, paleosol and phytolith studies indicate that open habitats d...
Article
Studies of large herbivorous mammal (ungulate) communities have revealed an association between increased tooth crown height (hypsodonty) and a shift to more arid environments over the Cenozoic. Ecometric analyses have also been used to examine the relationship between current climate conditions and crown height of these communities, and very succe...
Article
Full-text available
Borophagus is the terminal genus of the highly diverse and successful subfamily, Borophaginae. Skeletal remains of this bone-crushing canid are most commonly found in transitional or grassland environments across North America between Late Miocene–Middle Pleistocene, but are rare or absent in forested habitats. Here, we describe a humerus from the...
Poster
Full-text available
Cricetidae, which includes a wide range of mice, rats, and voles, is the second-most diverse and abundant family of mammals. Distributed across the Americas and Eurasia, this rodent family has been extensively studied for its success and adaptability in the face of climate and habitat change, and its utility for ecological reconstruction and the bi...
Conference Paper
Beavers (genus Castor) have been present in North America since the late Miocene, around 7 million years ago. Little is known about the dispersal of Castor from Eurasia and its spread across North America. The purpose of this study is to use species occurrence data along with bioclimatic variables to create models projecting the past, present, and...
Article
Several years ago, a new genus and species of peccary, “'Muknalia minima'”, was described from the Pleistocene of Mexico. We previously examined that specimen and concluded that it was synonymous with the extant collared peccary, 'Pecari tajacu', but that taxonomic revision is rejected by the authors of the original study (this volume). Here, we pr...
Article
Full-text available
Apatemyidae are a rare and enigmatic group of small insectivorous mammals that lived in North America and Europe in the Paleogene. The last known apatemyids in North America are two species in the genus Sinclairella, known from sites in the Great Plains and Florida. Here, I formally describe an upper second molar and lower incisor of the apatemyid,...
Article
Full-text available
The early Pliocene age Gray Fossil Site of Tennessee is one of the few late Neogene sites in eastern North America outside of Florida. Here, we describe two leporid species from the site: 1) a larger, less abundant Alilepus vagus and 2) a smaller, more abundant Notolagus lepusculus. Both species are well-known taxa with relatively broad geographic...
Poster
Full-text available
Relationships among the three feliform cat-like lineages: Felidae, Nimravidae, and Barbourofelidae remain controversial, with barbourofelids either falling within Nimravidae, or elevated to family. Ecomorphological studies of locomotion can be used to infer anatomical relationships, which may provide insight to phylogeny. Previous studies often use...
Article
Full-text available
Ongoing investigation of peccary remains from fossiliferous deposits in the Yucatán resulted in re-examination of previously identified tayassuid fossils from the region. This included the recently described new genus and species of peccary, 'Muknalia minima', which is based on a dentary from Muknal Cave near Tulum, Quintana Roo, Mexico. Diagnostic...
Article
Over the past decade, we recorded exact locations of in situ fossils and measured calcareous nodules in paleosols of the Oligocene and lower Miocene (Whitneyan–Arikareean) John Day Formation of Oregon. These data enable precise biostratigraphy within an astronomical time scale of Milankovitch obliquity cycles and also provide mean annual precipitat...
Article
Members of the Mylagaulidae have been known for over a century to bear nasal horns; the only rodents, extinct or extant, ever to have done so. This striking feature is known from five of the over 30 species of mylagaulid rodents discovered across North America and Eurasia, all relatively large animals that were likely less fossorial than their rela...
Article
Full-text available
Various methods exist for measuring and analyzing dental wear patterns in mammals, and these patterns have been particularly extensively studied in ungulates. Mesowear has proven useful as a method to compare large numbers of individuals, particularly fossil individuals, observe trends through time or between groups, and estimate paleoenvironmental...
Article
Until now, the pre-Miocene fossil record of mustelids in North America has been restricted to specimens attributable to oligobunine taxa and isolated remains tentatively allocated to the genus Plesictis. In the present study, we report on a nearly complete cranium and a referred dentary of a new genus and species of mustelid. The specimens were rec...
Article
Until now, the pre-Miocene fossil record of mustelids in North America has been restricted to specimens attributable to oligobunine taxa and isolated remains tentatively allocated to the genus Plesictis. In the present study, we report on a nearly complete cranium and a referred dentary of a new genus and species of mustelid. The specimens were rec...
Article
The Great American Biotic Interchange is considered to be a punctuated process, primarily occurring during four major pulses that began approximately 2.5 Ma. Central America and southeastern Mexico have a poor fossil record of this dynamic faunal history due to tropical climates. Exploration of submerged caves in the Yucatán, particularly the natur...
Article
Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene‐aged deposits of the western United States and Mexico. Their p...
Poster
Morphological convergence due to ecological specialization has made taxonomic identifications and understanding evolutionary relationships in talpids a challenge. Previous phylogenetic analyses using large data sets and complete taxon sampling have shown large discrepancies between molecular and morphological cladograms, making the placement of fos...
Article
Full-text available
The wolverine (Gulo gulo) is the largest living terrestrial member of the Mustelidae; a versatile predator formerly distributed throughout boreal regions of North America and Eurasia. Though commonly recovered from Pleistocene sites across their range, pre-Pleistocene records of the genus are exceedingly rare. Here, we describe a new species of Gul...
Data
Gulo gulo (ETVP 291) photographed in two different orientations (A) Palate parallel to the photographic plane. (B) Alveolar margin of P4 parallel to the photographic plane. Note that in A the lingual cingulum along the P4 metastyle is obscured, but it is visible in B. Scale bar equals 1 cm. Photographs by Joshua Samuels.
Data
Dental measurements (in mm) of gulonines and some other mustelid species used in comparative analyses Data were derived from measurements of specimens and consultation of cited literature sources.
Data
Occurrences of Gulo in the fossil records of North America and Eurasia Data were derived from a wide range of literature sources, as well as occurrences listed in the MIOMAP/FAUNMAP Databases (Carrasco et al., 2007; Graham & Lundeliu Jr, 2010; http://www.ucmp.berkeley.edu/neomap/) and NOW Database (Fortelius, 2013; http://pantodon.science.helsinki....
Data
Species mean values for postcranial measurements of rodents, associated with Samuels and Van Valkenburgh (2008).
Poster
The Gray Fossil Site (GFS), a late Miocene/early Pliocene aged (7 – 4.5 Ma) site in northeastern Tennessee, is one of the richest Cenozoic localities in the eastern United States. To date, thousands of microfauna specimens have been collected, but few small mammals have been identified and thoroughly studied. This study described the first talpid s...
Article
Topographically complex regions on land and in the oceans feature hotspots of biodiversity that reflect geological influences on ecological and evolutionary processes. Over geologic time, topographic diversity gradients wax and wane over millions of years, tracking tectonic or climatic history. Topographic diversity gradients from the present day a...
Article
Full-text available
We diagnose a new species of Brontotheriidae from a middle Eocene locality, the Clarno Nut Beds, from the Clarno Formation, John Day Basin, Central Oregon. Though renowned for its richness in fossil flora, fossil vertebrates are rare in the Clarno Nut Beds and this new species is the most abundantly represented mammal. Radiometric dating constrains...
Article
Primates were common in North America through most of the Eocene, but vanished in the Chadronian, about 35 million years ago. In the Arikareean, about 6 million years later, the enigmatic primate Ekgmowechashala appeared in the Great Plains and Oregon. This taxon shows little resemblance to other North American primates and its phylogenetic positio...
Article
Full-text available
Abstract The limbs of mammals exhibit a variety of morphologies that reflect the diversity of their habitats and their functional needs, including subtle structural differences in their distal limb integumentary appendages (hooks, claws, adhesive pads). Little is known about structure and function of claws of sigmodontine rodents. Here, we analyze...
Article
Full-text available
Abstract The limbs of mammals exhibit a variety of morphologies that reflect the diversity of their habitats and their functional needs, including subtle structural differences in their distal limb integumentary appendages (hooks, claws, adhesive pads). Little is known about structure and function of claws of sigmodontine rodents. Here, we analyze...
Conference Paper
Full-text available
The John Day Formation in eastern Oregon preserves a unique and remarkably complete record of volcanic and volcaniclastic sedimentary rocks spanning about 20 million years. The 400 m of the Oligocene aged Turtle Cove Member (30.8–25.9 Ma) preserve evidence of diverse mammalian communities perturbed by at least ten volcanic events, including five da...
Conference Paper
Oreodonts (Merycoidodontoidea) are the most abundant and diverse large herbivores from the Oligocene and early Miocene of Oregon, but unresolved taxonomy has hampered study of the group’s ecology and evolution. We re-assessed the taxonomy and stratigraphic distribution of oreodonts in the John Day Formation of eastern Oregon then analyzed relative...
Conference Paper
Full-text available
The John Day Formation in eastern Oregon preserves a unique and remarkably complete record of volcanic and volcaniclastic sedimentary rocks spanning about 20 million years. The 400 m of the Turtle Cove Member (30.8-25.9 Ma) preserve evidence of diverse mammalian communities perturbed by at least ten volcanic events, including five dated tuffs and t...
Article
Fishers are elusive carnivorans, with few occurrences in the fossil record. The origin and early evolution of fishers is unclear, but they likely originated in Asia. A new record of Pekania from the Rattlesnake Formation of Oregon represents the earliest known occurrence of a fisher, more than 5 million years earlier than other records in North Ame...
Article
Members of the order Carnivora display a broad range of locomotor habits, including cursorial, scansorial, arboreal, semiaquatic, aquatic, and semifossorial species from multiple families. Ecomorphological analyses from osteological measurements have been used successfully in prior studies of carnivorans and rodents to accurately infer the locomoto...
Article
Full-text available
Living coyotes modify their behavior in the presence of larger carnivores, such as wolves. However, little is known about the effects of competitor presence or absence on morphological change in coyotes or wolves over long periods of time. We examined the evolution of coyotes and wolves through time from the late Pleistocene, during which many larg...
Article
Castor, the extant beaver, is an important member of North American and Eurasian communities, altering ecosystems and landscapes wherever it occurs. Castor has a fossil record extending back to the late Miocene in Europe, Asia, and North America. The origin and early evolution of this genus is unclear but it likely originated in Eurasia and subsequ...
Article
Inside the mammalian nose lies a labyrinth of bony plates covered in epithelium collectively known as turbinates. Respiratory turbinates lie anteriorly and aid in heat and water conservation, while more posterior olfactory turbinates function in olfaction. Previous observations on a few carnivorans revealed that aquatic species have relatively larg...
Data
List of beaver specimens used in morphometric analyses. CMN = Canadian Museum of Nature, NMNH = Smithsonian Institution (U.S. National Museum of Natural History), AMNH = American Museum of Natural History, IVPP = Institute of Vertebrate Paleontology and Paleoanthropology, FMNH = Field Museum of Natural History, MNHN = Muséum National D'Histoire Nat...
Article
Full-text available
The extant beaver, Castor, has played an important role shaping landscapes and ecosystems in Eurasia and North America, yet the origins and early evolution of this lineage remain poorly understood. Here we use a geometric morphometric approach to help re-evaluate the phylogenetic affinities of a fossil skull from the Late Miocene of China. This spe...
Article
Full-text available
Members of the subfamily Ursinae dispersed into North America from Africa and Asia during the Miocene, with the appearance of Ursavus (Schlosser, 1899), Indarctos (Pilgrim, 1913), and Agriotherium (Wagner, 1837) (Dalquest, 1986; Miller and Carranza-Castañeda, 1996; Hunt, 1998). However, none of these genera were thought to have survived past the He...
Article
In the late Oligocene and early Miocene of North America, beavers (Castoridae) diversified into two lineages of burrowing specialists, the Palaeocastorinae and Migmacastorinae. Although common in the fossil record, artefactual evidence of burrowing beaver habits is rare and thus the ecology of most species is unknown. Living fossorial rodents displ...

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Projects

Projects (7)
Project
A project focused on deciphering the diversity, systematic relationships, and paleoecology of mylagaulid rodents.
Project
A geometric morphometric description of a new genus of giant desmognathan salamander from the earliest Pliocene Gray Fossil Site. This discovery offers clues about the evolutionary pressures that have shaped the desmognathan body plan and increases our understanding of Cenozoic plethodontid diversity.