H. Gregory McDonald

BLM - The Bureau of Land Management Lakewood Colorado (Retired)

The main aim of this study is to produce a modern analog for pollen and non-pollen palynomorphs (NPPs) preserved in soil in relation to the different vegetation types and herbivore impact in the Kaziranga National Park (KNP). The pollen data obtained reflects both the extant vegetation types in each habitat as well as landuse, but some site-by-site...

The braincase with horn cores of a male, extinct woodland muskox (Bootherium bombifrons) was recovered from a wetland near Hebron, Licking County, Ohio, in 1995. The fossil remains were preserved in sediments associated with a pro-glacial lake on the eastern margin of the Scioto lobe of the Laurentide ice sheet. An 853 cm long sediment core was ana...

The sloths that dispersed into Central and North America were most likely derived from tropical taxa, as indicated by their high occlusal surface area (OSA) in comparison with body mass, as in South American tropical species. Relative muzzle width and hypsodonty indices were used to infer the dietary adaptation of several Late Pleistocene/Early Hol...

We present the first record of the Shasta ground sloth (Nothrotheriops shastensis) for the eastern Great Basin. The single right upper second molariform was recovered from the back dirt pile of archaeological test pits excavated during the 1960s and 1970s in Smith Creek Cave, northern Snake Range, White Pine County, Nevada. The precise age of the s...

Late Pleistocene sloths were widely distributed and present in a diversity of habitats in South, Central, and North America and some Caribbean Islands. Late Pleistocene sloths include 27 genera in four families Megatheriidae, Megalonychidae, Mylodontidae, and Nothrotheriidae. There is no consensus on the number of valid species. Some sloths have wi...

The Occlusal Surface Area index together with the body mass contribute to better understanding the paleoecology and evolution of the giant sloths in the Americas. The giant sloths from southern South America probably had higher levels of fermentation/lower metabolic requirements, whereas the tropical taxa had higher metabolic requirements. The slot...

Three indices estimated from measurements of the humerus and ulna were used to suggest possible ecological habits of eight extinct giant sloths from the Late Pleistocene of the Brazilian Intertropical Region. To make these inferences, data from extant primates and xenarthras representing suspensory, climbing and digging forms were compared. The res...

Sloths represent one of the most successful South American clades that reached North America during the Great American Biotic Interchange (GABI). At least four families are known from the Pleistocene of North America: Mylodontidae, Megalonychidae, Megatheriidae, and Nothrotheriidae. Members of the Nothrotheriidae are known from the Middle Miocene t...

While the North American mylodont sloth, Parmylodon harlani, has been identified in multiple localities in Mexico, most of these records are from the southern part of the country. Consequently, there is a large geographic gap between its distribution in Mexico and the more northern records of the species in the United States. The recovery of the re...

Bone fragments embedded in a rib of a mastodon (Mammut americanum) from the Manis site, Washington, were digitally excavated and refit to reconstruct an object that is thin and broad, has smooth, shaped faces that converge to sharp lateral edges, and has a plano-convex cross section. These characteristics are consistent with the object being a huma...

Although known from more than 180 sites in North America, sites with records of multiple Megalonyx elements and individuals are rare. The Tarkio site in southwestern Iowa is unique with three contemporaneous individuals at different stages of development. Among these is one of the largest (ca. 1286 kg) and most complete adult Megalonyx jeffersonii...

Previously, the earliest fossils of flamingos in North America referable to modern taxa were known from the late Miocene (Clarendonian and Hemphillian). The recovery of a distal tibiotarsus and tarsometatarsus morphologically similar to the modern genera, Phoenicopterus and Phoenicoparrus, from early Miocene (Hemingfordian) deposits in Southern Cal...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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,...

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,...

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,...

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,...

Pollen frequencies data generated from Yak (Bos mutus) dung samples. (XLSX)

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Pleistocene Lake Bonneville created many classic examples of lacustrine shoreline landforms, which preserve a wide variety of vertebrate fossils. _is _eld guide provides a review of the published literature for a sampling of the lake’s world-class localities. _is guide also provides a brief overview of modern Great Salt Lake and its microbialites r...

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...

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...

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...

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...

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...