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H. Gregory McDonald

H. Gregory McDonald
BLM - The Bureau of Land Management Lakewood Colorado (Retired)

PhD

About

177
Publications
71,167
Reads
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4,725
Citations
Additional affiliations
January 2016 - present
BLM - The Bureau of Land Management
Position
  • Regional Paleontologist
November 2004 - January 2016
National Park Service
Position
  • Senior Curator of Natural History

Publications

Publications (177)
Article
Full-text available
The dung of the Indian wild ass was analyzed using biotic and abiotic proxies to determine its dietary habits in relation to the plant diversity and ecology in the arid region of western India. The presence of both micro and macrobotanical remains of Poaceae, Chenopodiaceae, and Fabaceae indicates they are the primary food plants of the wild ass. T...
Article
Full-text available
The paleoecology of the Shasta Ground Sloth, Nothrotheriops shastensis, is perhaps the best documented of all the North American megafauna thanks to caves in arid environments that preserve its dung. Past studies of the Shasta Ground Sloth have primarily focused on the biological aspects of its paleoecology using dung and skeletal remains, but less...
Article
Full-text available
A partial skeleton of the giant marmot Paenemarmota barbouri (Mammalia: Rodentia:Sciuridae) from Gila Group sediments in Devils Creek, Catron County, southwestern New Mexico is the second verified record of this extinct genus from the state. This specimen is Blancan in age, but we cannot constrain the age within the Blancan due to the lack of an as...
Article
Full-text available
A reevaluation of the late Miocene (early late Hemphillian) megalonychid fossils found at San Gerardo de Limoncito, Coto Brus Valley, Costa Rica is presented. These specimens which had previously been referred to Pliometanastes cf. P. protistus, based on a partial mandible and associated teeth material are now considered to belong to the genus Zaca...
Article
Full-text available
A reevaluation of the late Miocene (early late Hemphillian) megalonychid fossils found at San Gerardo de Limoncito, Coto Brus Valley, Costa Rica is presented. These specimens which had previously been referred to Pliometanastes cf. P. protistus, based on a partial mandible and associated teeth material are now considered to belong to the genus Zaca...
Article
Full-text available
Modern feces samples of the endangered red panda (Ailurus fulgens) were examined using multiproxy analysis to characterize the dietary patterns in their natural habitat in India. An abundance of Bambusoideae phytoliths and leaves (macrobotanical remains) provide direct evidence of their primary dietary plants. In contrast, Bambusoideae pollen is sp...
Article
Full-text available
McDonald HG 2021. Yukon to the Yucatan: Habitat partitioning in North American Late Pleistocene ground sloths (Xenarthra, Pilosa). Journal of Palaeosciences 70(2021): 237-251. The late Pleistocene mammalian fauna of North America included seven genera of ground sloth, representing four families. This cohort of megaherbivores had an extensive geogra...
Article
Mylodontidae (Mammalia, Xenarthra) is a family of ground sloths widely distributed in the South American fossil record, with members also present in Central and North America. Within the Mylodontidae, Lestodon armatus is the largest species, with an estimated body mass of more than three tonnes. This work focuses on the enlarged lower caniniforms o...
Article
Full-text available
Dental and craniomandibular data have been predominantly used to infer relationships among mylodontid ground sloths. Recent studies indicate the osteology of the manus also provides useful data to test phylogenetic relationships in mylodontine mylodontids. Here we provide new comparative data from the study of the manus of a member of the Scelidoth...
Article
We report here a new record of a megalonychid sloth from a late Pleistocene mammal assemblage from Cueva de Iglesitas (Mi.50), Caracas, Venezuela. This new site, the first with a Pleistocene fauna found in the vicinity of Caracas, is in a pristine geological and stratigraphic area and preserves previously untouched sediments containing fossils that...
Article
Although recognized as one of the most significant cultural transformations in North America, the reintroduction of the horse to the continent after AD 1492 has been rarely addressed by archaeological science. A key contributing factor behind this limited study is the apparent absence of equine skeletal remains from early historic archaeological co...
Article
Full-text available
The megalonychid sloth Meizonyx salvadorensis was previously known only from the holotype mandible from El Salvador. Here, we describe the first record of M. salvadorensis from the late Pleistocene of Mexico, examine its relationship to other members of the family Megalonychidae and discuss the palaeobiogeographical and palaeoecological implication...
Article
Full-text available
While borophagine canids are known from numerous Tertiary faunas across North America, they have not been well documented from the Tertiary faunas of Idaho. Five species represented by 2 genera are now known from Idaho faunas ranging from the latest Clarendonian / earliest Hemphillian to the late Blancan. The earliest records of borophagines in Ida...
Article
Full-text available
We present a review of the Miocene mylodont sloths described from the Urumaco Formation, Venezuela, and the Villa-vieja Formation, Colombia, and reexamine their phylogenetic relationships to the holotype of Pseudoprepotherium from the Río Yuca Formation, Venezuela. Based on our analysis we propose a number of taxonomic changes and consider Pseudopr...
Chapter
Full-text available
Great Salt Lake (GSL), Utah, is the largest lake in the Great Basin and one of the primary migratory stops for many species of birds in North America. Located at Rozel Point, on the north arm of the lake, are natural tar seeps that have formed on the former lake bed resulting from the migration of oil to the surface along fault lines. Once the petr...
Article
Full-text available
Large-scale changes in global climate at the end of the Pleistocene significantly impacted ecosystems across North America. However, the pace and scale of biotic turnover in response to both the Younger Dryas cold period and subsequent Holocene rapid warming have been challenging to assess because of the scarcity of well dated fossil and pollen rec...
Article
Living sloths represent two distinct lineages of small-sized mammals that independently evolved arboreality from terrestrial ancestors. The six extant species are the survivors of an evolutionary radiation marked by the extinction of large terrestrial forms at the end of the Quaternary. Until now sloth evolutionary history has mainly been reconstru...
Article
Full-text available
The study reports the micro-and macrobotanical remains on wild Yak dung, providing evidence for understanding the diet, habitat, and ecology of extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths. Other associated non-arboreal and arboreal taxa namely, Cyperacaeae,...
Article
Full-text available
The study reports the micro-and macrobotanical remains on wild Yak dung, providing evidence for understanding the diet, habitat, and ecology of extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths. Other associated non-arboreal and arboreal taxa namely, Cyperacaeae,...
Article
Full-text available
The study reports the micro-and macrobotanical remains on wild Yak dung, providing evidence for understanding the diet, habitat, and ecology of extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths. Other associated non-arboreal and arboreal taxa namely, Cyperacaeae,...
Article
The study reports the micro-and macrobotanical remains on wild Yak dung, providing evidence for understanding the diet, habitat, and ecology of extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths. Other associated non-arboreal and arboreal taxa namely, Cyperacaeae,...
Data
Pollen frequencies data generated from Yak (Bos mutus) dung samples. (XLSX)
Article
Full-text available
Stable isotope analysis of the first fossilized Eremotherium laurillardi remains from Belize offers valuable insights into the conditions within which this individual lived and its ability to adapt to the increasing aridity of the Last Glacial Maximum (LGM). Cathodoluminescence (CL) microscopy was used to identify chemical alteration of the tooth d...
Article
Full-text available
Stable isotope analysis of the first fossilized Eremotherium laurillardi remains from Belize offers valuable insights into the conditions within which this individual lived and its ability to adapt to the increasing aridity of the Last Glacial Maximum (LGM). Cathodoluminescence (CL) microscopy was used to identify chemical alteration of the tooth d...
Article
Stable isotope analysis of the first fossilized Eremotherium laurillardi remains from Belize offers valuable insights into the conditions within which this individual lived and its ability to adapt to the increasing aridity of the Last Glacial Maximum (LGM). Cathodoluminescence (CL) microscopy was used to identify chemical alteration of the tooth d...
Article
Pollen and non-pollen palynomorph analyses of 16 summer and winter dung samples of two endangered deer species, Sangai (Rucervus eldii eldii M'clelland) and Hog deer (Axis porcinus Zimmermann) from Keibul Lamjao National Park of Manipur, northeast India, was undertaken to examine the dietary preferences of these species in relation to the vegetatio...
Article
Full-text available
The presence of osteoderms in the skin of some extinct sloths and in cingulates (armadillos, pampatheres, and glyptodonts) has often been considered a pleisomorphic character of the Xenarthra. While osteoderms are known from the earliest cingulates, they are absent in most sloths including the two extant taxa and only appear late in their fossil re...
Article
The first record of the Jefferson ground sloth, Megalonyx jeffersonii, in New York is reported. The specimen consists of a partial synsacrum recovered from a peat deposit near Newburgh, Orange County. Compared to other synsacra of Megalonyx, the number of vertebrae is anomalous with one less caudal vertebra than expected. Stable isotope analysis of...
Article
Sloths, like other xenarthrans, are an extremely interesting group of mammals that, after a long history of evolution and diversification in South America, became established on islands in the Caribbean and later reached North America during the Great American Biotic Interchange. In all three regions, they were part of the impressive Pleistocene me...
Preprint
Full-text available
The study present to document the micro and macrobotanical remain on wild Yak dung to understand the diet, habitat, and ecology in relation to determining possible ecological relationships with extant and extinct megaherbivores. Grasses are the primary diet of the yak as indicated by the abundance of grass pollen and phytoliths, though it is obviou...
Chapter
Full-text available
Today, the United States Department of the Interior manages 500 million acres of surface land, about one-fifth of the land in the United States. Since enactment of the Antiquities Act in 1906, historic and scientifi c resources collected on public land have remained government property, held in trust for the people of the United States. As a result...
Article
A small but significant assemblage of Late Pleistocene mammals was recovered from an eroding shoreline at Paw Paw Cove, located on the Chesapeake Bay side of Tilghman Island, Talbot County, Maryland. Additionally, Clovis-age (11,050–10,800 radiocarbon [14C] years before present) artifacts were found in a lag deposit beneath a loess deposit at the s...
Article
Full-text available
A previous study reported the fusion of spinous processes of thoracic vertebrae one and two in the ground sloth Glossotherium, proposing an injury or a congenital deformation as possible causes. In this paper we examined members of four families of Pleistocene sloths (Mylodontidae, Megatheriidae, Nothrotheriidae and Megalonychidae) to document the...
Article
Predator-prey interactions revealed by vertebrate trace fossils are extremely rare. We present footprint evidence from White Sands National Monument in New Mexico for the association of sloth and human trackways. Geologically, the sloth and human trackways were made contemporaneously, and the sloth trackways show evidence of evasion and defensive b...
Article
Full-text available
Predator-prey interactions revealed by vertebrate trace fossils are extremely rare. We present footprint evidence from White Sands National Monument in New Mexico for the association of sloth and human trackways. Geologically, the sloth and human trackways were made contemporaneously, and the sloth trackways show evidence of evasion and defensive b...
Article
Full-text available
Predator-prey interactions revealed by vertebrate trace fossils are extremely rare. We present footprint evidence from White Sands National Monument in New Mexico for the association of sloth and human trackways. Geologically, the sloth and human trackways were made contemporaneously, and the sloth trackways show evidence of evasion and defensive b...
Article
Here we describe two new megalonychid sloths from the late Miocene of the Urumaco Formation (Falc�on State, Venezuela), Urumacocnus urbanii gen. et. sp. nov. and Pattersonocnus diazgameroi gen. et sp. nov. The recovery of these distinct taxa greatly improves our understanding of sloth diversity in the late Miocene of northern South America. A phylo...
Book
Few animals spark the imagination as much as the sabertooth cat Smilodon. With their incredibly long canines, which hung like fangs past their jaws, these ferocious predators were first encountered by humans when our species entered the Americas. We can only imagine what ice age humans felt when they were confronted by a wild cat larger than a Sibe...
Article
Pleistocene Lake Bonneville created many classic examples of lacustrine shoreline landforms, which preserve a wide variety of vertebrate fossils. This field guide provides a review of the published literature for a sampling of the lake’s world-class localities. This guide also provides a brief overview of modern Great Salt Lake and its microbialite...
Article
A new genus and species of megalonychid sloth, Zacatzontli tecolotlanensis n. gen. n. sp., is described from the late Hemphillian of Jalisco, Mexico. Comparison and analysis of the type specimen, a mandible, with other megalonychid sloths shows a closer relationship to South American taxa than those from North America or the Caribbean. This suggest...
Article
Fungal spores, especially those of coprophilous fungi, are present in dung middens of Rhinoceros unicornis (greater one-horned rhinoceros) in both forest and grassland areas of the Kaziranga National Park, India. The presence of copro-philous fungi on rhino dung, chiefly Sporormiella, Saccobolus, Ascodesmis, Cercophora, and Sordaria, is documented...
Article
The remains of the Columbian Mammoth, Mammuthus columbi, are reported from four localities in Guatemala based on seven dental records. These localities are widely separated and include one specimen from Río La Pasión, Sayaxché, Departamento de Petén in the northern part of the country, one specimen from Chinautla, Departamento de Guatemala in the s...
Article
A new genus and species of late Pleistocene megalonychid sloth, Nohochichak xibalbahkah, gen. et sp. nov., is described from Hoyo Negro, a chamber in the Sac Actun cave system, Quintana Roo, Mexico. Phylogenetic analysis indicates that this new sloth is most closely related to Meizonyx salvadorensis from the middle Pleistocene of El Salvador, and t...
Article
Full-text available
We report a new genus and species of sloth, based on a partial mandible and associated femur, from the early Miocene of Venezuela. Baraguatherium takumara, gen. et sp. nov., represents the earliest member of the Mylodontoidea recognized from northern South America. Phylogenetically and morphologically, Baraguatherium possesses some plesiomorphic ch...
Article
The Greater One-horned Rhino of India is an endangered species. We investigate the pollen and non-pollen palynomorphs preserved in rhino dung collected from a communal rhino dung midden in Kaziranga National Park to document the vegetation composition and dietary habits of this rhino. The palynodata reflects the dominance of nonarboreals over arbor...
Article
Geological explorations of the basal beds of the Río Yuca Formation (Tucupido region, Portuguesa State, western Venezuela) resulted in the recognition of a new vertebrate assemblage that includes eight taxa: the toxodont cf. Adinotherium, a Peltephilidae armadillo, the freshwaters fishes Platysilurus and Phractocephalus, the caiman Purussaurus, an...
Article
Full-text available
Among the South American animals that entered North America following the establishment of the Panamanian land bridge were members of the family Erethizontidae. The early fossil record of this group in North America is sparse and so the discovery of fossil porcupines from the Middle Pleistocene (Irvingtonian) fauna of El Golfo de Santa Clara, Sonor...
Article
Full-text available
In most folivorans, the premaxilla is loosely attached to the maxilla, so that it is often missing in otherwise very well-preserved fossil skulls. Despite its infrequent preservation in sloths, the premaxilla has been shown to have phylogenetically significant variation among the taxa that do preserve the element. In the family Megalonychidae, the...
Article
Multimodality imaging, including computed tomography (CT) and digital radiography, was utilized to examine a fossilized hemimandible of a probable female Hagerman horse (Equus simplicidens) with a large, ventrally located, osseous deformation. Utilizing comparative pathology to the modern day horse, it was determined that the most likely etiology o...
Conference Paper
Full-text available
Every year, well-meaning researchers are reprimanded or issued citations for failing to seek the required permissions to work on public land. Permitting is required by law and may involve several steps including environmental review, and because this involves a variety of officials, there is a certain amount of time involved in issuing the permit....
Article
Full-text available
The gross morphology of the axial postcranium of Thalassocnus is presented here, completing the description of the skeleton of the genus. Thalassocnus is characterized by a low spinous process on C7, a cranially shifted position of the diaphragmatic vertebra, a great number of caudal vertebrae, the morphology of their transverse processes, and the...
Article
A partial skeleton of an elk-moose, Cervalces scotti, was excavated at a depth of about 5 m below the surface near Chippewa Lake, Medina County, OH. A total of 44 bones and bone fragments were recovered from a male animal judged to be between 4.5 and 5.5 years old, based on comparison with Alces americanus and Cervus elaphus. Bone from the Cervalce...