Greg McDonald

A new, geologically old record of the extinct camelid Camelops in Utah

Historical Biology, 2026

The extinct camelid Camelops hesternus, a prominent member of the late Pleistocene fauna of weste... more The extinct camelid Camelops hesternus, a prominent member of the late Pleistocene fauna of western North America, was among the megafauna that became extinct at the end of the Pleistocene. The recovery of a tibia of an adult Camelops from a gravel pit near Vernal, Uintah County, Utah, adds to the 10 records of the species previously documented in Utah. Only a few radiocarbon dates are available for Camelops, so the radiocarbon date of the Vernal specimen at 28,750 ± 190 rcy (33,760-32,225 cal year), while not close in time to the North American megafaunal extinct event, is the oldest radiocarbon date for the species and aids documenting its geographical distribution in time prior to its extinction.

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Babcock and McDonald 2025 A gentle giant Thomas Jefferson's ground sloth

Open Access Government, 2025

A gentle giant: Thomas Jefferson's ground sloth openaccessgovernment.org/article/a-gentle-giant-t... more A gentle giant: Thomas Jefferson's ground sloth openaccessgovernment.org/article/a-gentle-giant-thomas-jeffersons-ground-sloth/198484 Reconstructed skeleton of a 2.1-m-tall giant ground sloth, Megalonyx jeffersonii from Holmes County, Ohio, US, mounted in 1896 (A); a 25-cm-long claw core from the right rear foot (B); and detail of the upper part of the right femur showing slices presumably made using a flint knife by a North American Palaeo-Indian approximately 13,100 years ago (C).

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Babcock and McDonald 2025 A gentle giant Thomas Jefferson's ground sloth

A gentle giant: Thomas Jefferson's ground sloth openaccessgovernment.org/article/a-gentle-giant-t... more A gentle giant: Thomas Jefferson's ground sloth openaccessgovernment.org/article/a-gentle-giant-thomas-jeffersons-ground-sloth/198484 Reconstructed skeleton of a 2.1-m-tall giant ground sloth, Megalonyx jeffersonii from Holmes County, Ohio, US, mounted in 1896 (A); a 25-cm-long claw core from the right rear foot (B); and detail of the upper part of the right femur showing slices presumably made using a flint knife by a North American Palaeo-Indian approximately 13,100 years ago (C).

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FIRST RECORD OF THE GROUND SLOTH NOTHROTHERIOPS (XENARTHRA: NOTHROTHERIIDAE) FROM THE CENTRAL MISSISSIPPI RIVER DRAINAGE IN ARKANSAS

New Mexico Museum of Natural History and Science Bulletin , 2025

The discovery of a posterior portion of a cranium represents the first record of the small extinc... more The discovery of a posterior portion of a cranium represents the first record of the small extinct ground sloth, Nothrotheriops, from the central Mississippi River in Arkansas. This discovery fills a geographic gap in the distribution of the genus between records to the east in Florida and to the
west in Texas and Oklahoma. As most fossil taxa recovered from this area are considered Rancholabrean in age, the presence of Nothrotheriops is unexpected as all previous records of this taxon in the eastern
United States are from the Irvingtonian. While the exact age of the sloth cannot be determined, it is most likely late Irvingtonian to early Rancholabrean in age

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A new record of the extinct ground sloth Megalonyx jeffersonii from Kansas and review of the history of the genus in the state

Transactions of the Kansas Academy of Science, 2025

The recovery of a partial skull comprised mostly of the braincase of the extinct sloth, Megalonyx... more The recovery of a partial skull comprised mostly of the braincase of the extinct sloth, Megalonyx jeffersonii from Hays, Ellis County, Kansas provides a better understanding of the distribution of this species in Kansas and on the Great Plains in general. While the age of the skull could not be determined by radiocarbon dating, its presence in the Peoria loess narrows the age of the specimen to the late Wisconsian, most likely the Last Glacial Maximum between 21,000-and 12,000-years BP. The sloth specimen is among the few vertebrate remains directly recovered from the Peoria loess.

format_quoteThe new discovery of M. jeffersonii in Hays, Kansas integrates knowledge of species distribution and paleoecology during the late Pleistocene.format_quote

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The Woodland Muskox Bootherium bombifrons (Artiodactyla, Bovidae) from Hebron, Licking County, Ohio, USA and its Paleoecology in the Great Lakes Region

by Greg McDonald and David Dyer

Ohio Journal of Science, 2024

The braincase with horn cores of a male, extinct woodland muskox (Bootherium bombifrons) was reco... more 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 analyzed, and its pollen record was used to reconstruct changes in the region's late Pleistocene paleoecology, which was barren landscape immediately following deglaciation. This transitioned to a spruce-dominated forest, and finally a deciduous forest. While most previous records of Bootherium have been associated with spruce-dominated habitat, the Hebron muskox lived in an environment with forests dominated by deciduous trees with only minor amounts of spruce. A paleoclimatic model-based on multiple records of Bootherium-indicates the wide distribution of the species south of the maximum continental ice sheets was due to its lesser cold tolerance and higher warm temperature tolerance than the modern muskox. Based on 2 averaged direct AMS radiocarbon measurements on the muskox skull, its age is 11,086 ± 18 radiocarbon years (13,093 to 12,926 calendar years BP) making it the youngest radiocarbon dated individual of Bootherium bombifrons. This date suggests the eventual extinction of the species may be related to the decline of its preferred habitat as climates changed at the end of the Pleistocene.

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Pollen and non-pollen palynomorph depositional patterns in Kaziranga National Park, India: Implications for palaeoecology and palaeoherbivory analysis

The Holocene, Dec 6, 2023

The main aim of this study is to produce a modern analog for pollen and non-pollen palynomorphs (... more 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 variation was observed with respect to the coprophilous fungal spores present in the palynoassemblage. Canonical correspondence analysis (CCA) analysis of pollen data reveals the presence of five significantly different vegetation types, while the nonpollen palynomorphs are relatively similar in relation to the different vegetation types. The long-term association of the wildlife and their impact on different vegetation types is one of the main reasons for the variation seen in the depositional pattern in the assemblage. The openland area is one of the most important areas for wildlife in the KNP as indicated by the presence of marker pollen and coprophilous fungal spores in the palynoassemblages. Coprophilous fungal spores were most abundant in this vegetation type reflecting the higher density of herbivores. The representation of pollen and coprophilous fungal spores from the swamp samples reflected the overall composition of all vegetation types existing in the KNP. This data can be utilized as a baseline for the interpretation of paleoecological and paleoherbivory studies in other parts of the Indian subcontinent as well as its potential application at a global level

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Hagerman Fossil Beds

Natural History, 1998

Focuses on the fossil beds in the town of Hagerman in south-central Idaho. Information on the exc... more

Pollen and non-pollen palynomorph depositional patterns in Kaziranga National Park, India: Implications for palaeoecology and palaeoherbivory analysis

by Eline N van Asperen and Greg McDonald

The Holocene, 2024

The main aim of this study is to produce a modern analog for pollen and non-pollen palynomorphs (... more 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 variation was observed with respect to the coprophilous fungal spores present in the palynoassemblage. Canonical correspondence analysis (CCA) analysis of pollen data reveals the presence of five significantly different vegetation types, while the nonpollen palynomorphs are relatively similar in relation to the different vegetation types. The long-term association of the wildlife and their impact on different vegetation types is one of the main reasons for the variation seen in the depositional pattern in the assemblage. The openland area is one of the most important areas for wildlife in the KNP as indicated by the presence of marker pollen and coprophilous fungal spores in the palynoassemblages. Coprophilous fungal spores were most abundant in this vegetation type reflecting the higher density of herbivores. The representation of pollen and coprophilous fungal spores from the swamp samples reflected the overall composition of all vegetation types existing in the KNP. This data can be utilized as a baseline for the interpretation of paleoecological and paleoherbivory studies in other parts of the Indian subcontinent as well as its potential application at a global level

format_quotePollen and fungal spore data establish a baseline for paleoecological studies across the Indian subcontinent, with potential global applications.format_quote

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Occurrence of the ground sloth Nothrotheriops (Xenarthra, Folivora) in the Late Pleistocene of Uruguay: new information on its dietary and habitat preferences based on stable isotope analysis

Journal of Mammalian Evolution, 2023

Sloths represent one of the most successful South American clades that reached North America duri... more 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 to the Pleistocene/Holocene transition in the Americas, but Nothrotheriops is the only genus in the family recorded in North America. Recently, femora with characteristic nothrothere morphology were recovered from Santa Fe, Argentina, and assigned to Nothrotheriops, thus greatly expanding the geographic distribution of this taxon. In Uruguay, records of Quaternary Nothrotheriidae are scarce, and previous reports are limited to the genus Nothrotherium. In this work, we describe a humerus from Arroyo del Vizcaíno (AdV), a ~30 ka site located in southern Uruguay, and assign it to the nothrotheriid Nothrotheriops sp. We also discuss several specimens from Uruguay originally assigned to Nothrotherium, which upon reexamination can be tentatively reassigned to Nothrotheriops sp. Furthermore, we employ stable isotope analysis to explore the climatic and dietary preferences of this taxon in South America. The new records are consistent with the materials reported from Argentina, thus providing new knowledge of the geographic distribution of the taxon, as well as its climatic and dietary preferences. Stable isotope results showed δ 13 C values consistent with diets based mainly on C 3 plants, similar to those published for N. shastensis in North America.

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Occurrence of the ground sloth Nothrotheriops (Xenarthra, Folivora) in the Late Pleistocene of Uruguay: new information on its dietary and habitat preferences based on stable isotope analysis

by Greg McDonald, Luciano Varela, and Raúl Vezzosi

Journal of Mammalian Evolution, 2023

Sloths represent one of the most successful South American clades that reached North America duri... more 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 to the Pleistocene/Holocene transition in the Americas, but Nothrotheriops is the only genus in the family recorded in North America. Recently, femora with characteristic nothrothere morphology were recovered from Santa Fe, Argentina, and assigned to Nothrotheriops, thus greatly expanding the geographic distribution of this taxon. In Uruguay, records of Quaternary Nothrotheriidae are scarce, and previous reports are limited to the genus Nothrotherium. In this work, we describe a humerus from Arroyo del Vizcaíno (AdV), a ~30 ka site located in southern Uruguay, and assign it to the nothrotheriid Nothrotheriops sp. We also discuss several specimens from Uruguay originally assigned to Nothrotherium, which upon reexamination can be tentatively reassigned to Nothrotheriops sp. Furthermore, we employ stable isotope analysis to explore the climatic and dietary preferences of this taxon in South America. The new records are consistent with the materials reported from Argentina, thus providing new knowledge of the geographic distribution of the taxon, as well as its climatic and dietary preferences. Stable isotope results showed δ 13 C values consistent with diets based mainly on C 3 plants, similar to those published for N. shastensis in North America.

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Late Pleistocene (Rancholabrean) Mammalian Assemblage from Paw Paw Cove, Tilghman Island, Maryland

by Ralph Eshelman and Greg McDonald

A small but significant assemblage of Late Pleistocene mammals was recovered from an eroding shor... more 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 site. An accelerator mass spectrometry date obtained from an organic stratum below the loess at the same location suggests that this small fossil assemblage is approximately 21,000 years old. Identifiable taxa include four extinct species, Castoroides sp. (giant beaver), Equus sp. (horse), Tapirus veroensis (Vero tapir), and Mammut americanum (American mastodon), along with Canis cf. C. latrans (coyote), and Cervus elaphus (wapiti). Significantly, the tapir and giant beaver are the first records for Maryland, and the tapir is the first record from the Coastal Plain of the Chesapeake region of Delaware, Maryland, and Virginia. The provisiona...

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Paleobiology of Jefferson’s Ground Sloth (Megalonyx jeffersonii) derived from three contemporaneous, ontogenetically distinct individuals recovered from Southwestern Iowa, U.S.A

Journal of Vertebrate Paleontology, 2022

Although known from more than 180 sites in North America, sites with records of multiple Megalony... more 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 skeletons (ca. 50%, NISP, 123) known. An intermingled sub-adult (ca. 25%, NISP, 63) represents a comparatively complete skeleton for this ontogenetic stage. A third individual, an infant known only from both scapulae (NISP 2), is commingled with sub-adult remains. Scapula sizes indicate that the two juveniles were 50 and 30% of the adult&#39;s size. Differential bone preservation and pattern of scatter shows that the adult decomposed lying on its left side and the remains were partially scavenged. Multiple taphonomic proxies demonstrate that the skeletons were subaerially exposed for a limited period, but fluvial transport was not a factor. These individuals, preserved in the same low-energy microstratigraphic unit, apparently died concurrently and probably represent a Megalonyx social unit. Using mammal body size to estimate life history, the estimated average lifespan for M. jeffersonii was around 19 years; gestation time was about 14 months; the interbirth interval was approximately 3 years; and sexual maturation occurred at around 6.5 years. OSL analysis indicates that the sloths were deposited about 106,000 years ago (MIS substage 5ec). Paleoenvironmental proxies suggest an interglacial environment of open woodland along a stream with marshes, like the environment in southwest Iowa today.

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Paleobiology of Jefferson's Ground Sloth (Megalonyx jeffersonii) derived from three contemporaneous, ontogenetically distinct individuals recovered from Southwestern Iowa, U.S.A

by Greg McDonald, Holmes A Semken, Jr., Russell Graham, Andrew Clack, Adel Haj, Sarah Horgen, and James Theler

Journal of Vertebrate Paleontoloyg, 2022

Although known from more than 180 sites in North America, sites with records of multiple Megalony... more 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 skeletons (ca. 50%, NISP, 123) known. An intermingled sub-adult (ca. 25%, NISP, 63) represents a comparatively complete skeleton for this ontogenetic stage. A third individual, an infant known only from both scapulae (NISP 2), is commingled with sub-adult remains. Scapula sizes indicate that the two juveniles were 50 and 30% of the adult's size. Differential bone preservation and pattern of scatter shows that the adult decomposed lying on its left side and the remains were partially scavenged. Multiple taphonomic proxies demonstrate that the skeletons were subaerially exposed for a limited period, but fluvial transport was not a factor. These individuals, preserved in the same low-energy microstratigraphic unit, apparently died concurrently and probably represent a Megalonyx social unit. Using mammal body size to estimate life history, the estimated average lifespan for M. jeffersonii was around 19 years; gestation time was about 14 months; the interbirth interval was approximately 3 years; and sexual maturation occurred at around 6.5 years. OSL analysis indicates that the sloths were deposited about 106,000 years ago (MIS substage 5ec). Paleoenvironmental proxies suggest an interglacial environment of open woodland along a stream with marshes, like the environment in southwest Iowa today.

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Reexamination of the Relationship of Pseudoprepotherium hoffstetter, 1961, to the Mylodont Ground Sloths (Xenarthra) from the Miocene of Northern South America

Revista Geológica de América Central, Aug 7, 2020

We present a review of the Miocene mylodont sloths described from the Urumaco Formation, Venezuel... more We present a review of the Miocene mylodont sloths described from the Urumaco Formation, Venezuela, and the Villavieja 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 Pseudoprepotherium confusum to be sufficiently different from the type of Pseudoprepotherium venezuelanum, that it merits a distinct genus, Magdalenabradys. We include in this new genus post-cranial material formerly assigned to Bolivatherium urumaquensis as a new species, Magdalenabradys kolossiaia. Comparison of Mirandabradys, first described from the late Miocene, Urumaco Formation of Venezuela, and its included species with the holotype of Pseudoprepotherium indicates they are the same genus, and Mirandabradys is considered a junior synonym. Three species of Pseudoprepotherium are recognized: the genotypic species, P. venezuelanum from the Río Yuca Formation, P. socorrensis from the Socorro Formation and P. urumaquensis, from the Urumaco Formation. We propose that based on the poor preservation and incompleteness of the type material that Mirandabradys zabasi is not a valid species and should be considered a nomen dubium

Coprophilous and non-coprophilous fungal spores of Bos mutus modern dung from the Indian Himalaya: Implications to temperate paleoherbivory and paleoecological analysis

Review of Palaeobotany and Palynology

Abstract Fungal spores preserved on dung of wild yak (Bos mutus) from the higher Himalayan region... more Abstract Fungal spores preserved on dung of wild yak (Bos mutus) from the higher Himalayan region of India were studied in order to understand the differences in their diversity and abundance in summer and winter. A total of 19 coprophilous and non-coprophilous fungal spore types were recovered from the dung samples. The diversity of the fungal spores in both seasons was almost similar, but the overall frequency of the coprophilous fungi in the winter samples was relatively lower compared to the summer samples. Clumping of the coprophilous fungi, Sporormiella, Saccobolus, and Cercophora, was observed regularly in the assemblage, indicating that the dung was the primary food source for these fungal spores. Non-coprophilous fungi such as Glomus, Pleospora, and Tetraploa are also consistently recovered in the assemblage. Multivariate principal component analysis (PCA) applied to the coprophilous and non-coprophilous fungal frequency data indicated significant variation in summer and winter fungal types. Such differences in modern dung samples can serve as a baseline for the interpretation of coprolites of megafauna and provide insights into their ecology and extinction. Complementing paleoherbivory analysis, these baseline data can also be applied to the examination of sedimentary soil profiles to determine the presence and abundance of coprophilous fungi as a reflection of the former presence of megafauna in the region during the Quaternary. Such studies can also provide information on the relationship between the plants and animals in relation to the development of agro-pastoralism in the region.

Late Miocene to Late Pliocene (Hemphillian to Blancan) Borophagine Canids (Mammalia: Carnivora) from Idaho

Western North American Naturalist

Abstract. While borophagine canids are known from numerous Tertiary faunas across North America, ... more Abstract. 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 Idaho are Epicyon haydeni from the early Hemphillian Star Valley fauna and Borophagus pugnator from the late Clarendonian / early Hemphillian Poison Creek Formation. Borophagus secundus is present in the late Hemphillian Chalk Hills Formation, and 2 species are present in the Blancan Glenns Ferry Formation: (1) B. hilli in the early Blancan Hagerman local fauna and (2) the terminal taxon of the subfamily, B. diversidens, in the late Blancan Grand View local fauna.

A monodominant late-Pleistocene megafauna locality from Santa Elena, Ecuador: Insight on the biology and behavior of giant ground sloths

Palaeogeography, Palaeoclimatology, Palaeoecology

Abstract Extinct giant ground sloths are a common taxon in New World Quaternary deposits, but rel... more Abstract Extinct giant ground sloths are a common taxon in New World Quaternary deposits, but relatively little is known about individual species' behavior or social structure. In this paper, we investigate the development of the late-Pleistocene locality Tanque Loma on the southwest coast of Ecuador, which preserves remains of at least 22 individuals of the giant ground sloth, Eremotherium laurillardi in asphaltic sediments. Multiple lines of evidence suggest that these sloths may have congregated and died in a mass mortality event in a marshy riparian habitat. Such evidence includes (1) a dense, laterally-extensive, bonebed-style accumulation; (2) a multigenerational age structure with adult and large juvenile individuals well-represented; (3) sediments suggestive of a low-energy anoxic aquatic environment; and (4) the presence of abundant plant material consistent with digested fodder representing coprolites or gut contents of E. laurillardi. Taking observations from modern megafaunal ecosystems as an analogue, we suggest that this death event could have resulted from drought and/or disease stemming from the contamination of the wallow, paralleling situations observed among hippopotamus populations in watering holes on the present-day African savannah.

Nothrotheriops Shastensis (Sinclair, 1905) from Actun Lak: First Record of Nothrotheridae (Mammalia, Xenarthra, Pilosa) from Belize

Ameghiniana, 2014

Sloth remains recovered from Actun Lak, Cayo District, Belize, during archaeological excavations ... more Sloth remains recovered from Actun Lak, Cayo District, Belize, during archaeological excavations by the Pacbitun Regional Archaeological Project include numerous though mainly fragmentary elements. Among the identifiable remains are a lower molariform tooth and several elements of the manus and pes. Although no complete cranial and long bone postcranial remains are available, the sloth is confidently assigned to the nothrotheriid species Nothrotheriops shastensis (Sinclair). This is the most southern certain record of the North American genus Nothrotheriops Hoffstetter and the first record of a nothrotheriid from Central America. Based on our knowledge of the species’ diet and habitat preference from dry caves in the southwestern United States, its presence in Belize has paleoecological and biogeographic implications. The Belize remains clearly indicate that sloth diversity in northern Central America was greater than previously suspected. They also suggest that a greater variety of habitats existed in this region during the Pleistocene, and that vegetation communities underwent more dramatic changes during this interval than previously thought.

First record of Meizonyx salvadorensis (Mammalia: Xenarthra: Pilosa) from the late Pleistocene of Mexico and its evolutionary implications

The megalonychid sloth Meizonyx salvadorensis was previously known only from the holotype mandibl... more 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 implications of this new record. The specimen consists of an associated skull and mandible, and parts of the postcranial skeleton, recovered from the Sistema Huautla cave complex located in the Sierra Mazateca, a part of the Sierra Madre Oriental del Sur, east of Huautla de Jiménez, in the state of Oaxaca, Mexico. Two phylogenetic analyses were carried out utilizing maximum parsimony and Bayesian approaches, and included the new material within the data matrix used for previous studies of members of Megalonychidae. The phylogenetic hypothesis obtained from the Bayesian analysis indicates the closest relationship of Meizonyx salvadorensis is to Xibalb...

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