Arctotherium

Arctotherium Temporal range: Late Pliocene-Early Holocene (Uquian-Lujanian) ~2.588–0.010  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Life restoration of A. bonariense
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Ursidae
Subfamily:	Tremarctinae
Genus:	† Arctotherium Bravard, 1857
Type species
†Arctotherium bonariense Gervais, 1852
Species
A. angustidensGervais & Ameghino, 1880 A. bonarienseGervais, 1852 (type) A. tarijenseAmeghino, 1902 A. vetustumAmeghino, 1885 A. wingeiAmeghino, 1902
Synonyms
Genus synonymy PararctotheriumAmeghino, 1904 Species synonymy A. angustidens: Arctotherium latidensBravard, 1857 A. bonariense: Arctodus bonariensisPerea and Ubilla, 2001 Arctotherium bonaerense? Pararctotherium enectumAmeghino, 1904 Ursus bonariensisGervais, 1852 A. tarijense: Pararctotherium pamparumAmeghino, 1904 A. wingei: Arctotherium brasiliensisLund, 1804 Arctotherium brasilienseLund, 1838 ? Panthera balamoides ? Stinnesbeck, 2019

Arctotherium ("bear beast") is an extinct genus of the Pleistocene short-faced bears endemic to Central and South America. ^[1] Arctotherium migrated from North America to South America during the Great American Interchange, following the formation of the Isthmus of Panama during the late Pliocene. The genus consists of one early giant form, A. angustidens, and several succeeding smaller species, which were within the size range of modern bears. ^[2] Arctotherium was adapted to open and mixed habitat. ^[3] They are genetically closer to the spectacled bear (Tremarctos ornatus), than to Arctodus of North America, implying the two extinct forms evolved large size in a convergent manner. ^[4]

Evolution

Tremarctinae

Arctotherium is part of the Tremarctinae subfamily of bears, otherwise known as the short faced bears, which also includes Arctodus (North American short faced bears) and Tremarctos (the Floridian and modern spectacled bear). Tremarctinae originate with their common ancestor, Plionarctos, ^[4] in the Middle Hemphillian (earliest Late Miocene, ~10 Ma) of North America; Plionarctos is last recorded in the early Blancan (Early Pliocene, ~3.3 Ma). Around the Miocene-Pliocene boundary (~5 Ma) Tremarctines, along with other ursids, experienced an explosive radiation in diversity, as C4 vegetation (grasses) and open habitats dominated, the world experienced a major temperature drop and increased seasonality, and a faunal turnover which extinguished 60–70% of all Eurasian faunal genera, and 70–80% of North American genera. ^[5]

Correspondingly, recent genetic studies suggest that the mean divergence dates for Arctotherium, Arctodus and Tremarctos was 4.8 Ma, and between Arctotherium and Tremarctos at 4.1 Ma. ^[4] Notably, all three genera are first recorded from the Blancan (Late Pliocene) of North America, with the first possible record of Arctotherium sp. being a tooth found in the Cuscatlán Formation of El Salvador, dated to the latest Pliocene (2.588 Ma). ^[6]

South America

The oldest dated confirmed remains of Arctotherium in South America are those of the gigantic A. angustidens from Buenos Aires, Argentina. What the evolutionary history of Arctotherium was beforehand, particularly regarding its sudden significant size, is unclear. A. angustidens remains have been dated to between 1Ma to 0.7 Ma of the Pleistocene, which corresponds with the Ensenadan period (although the younger dates are uncertain). ^{[2] [7]}

A. angustidens went extinct at the start of the Lujanian (~700,000 years ago), replaced by medium-sized Arctotherium species. The first recorded successor species was A. vetustum (Middle Pleistocene), then shortly thereafter by the more robustly built A. bonariense (Middle / Late Pleistocene), along with A. tarijense (Middle Pleistocene to the Early Holocene). While the smallest but most widespread species, A. wingei, is only confirmed from the Late Pleistocene and Early Holocene, the species' more tropical disposition is thought to greatly limit fossilisation. That, along with A. wingei's more ancestral position in Arctotherium, suggests an origin in the Middle Pleistocene.

Within Arctotherium, two clades are thought to exist- A. bonariense and A. tarijense have been described as the most derived species of the genus, ^{[1] [8]} whilst A. vetustum and A. wingei are regarded the most archaic, even more so than A. angustidens. ^[1] Of these successor species, A. tarijense and A. wingei are by far the most successful when taking into account temporal & geographic range, and the frequency of fossil finds. ^[9] A separate Andean form of Arctotherium is also suggested to have existed at the end of the Pleistocene, consisting of the type A. wingei specimen from Tarija and an Argentine Andean individual, in contrast with the larger and more robust Brazilian A. wingei specimens. ^[10]

Curiously, while Arctotherium's known species dramatically shrank in size after A. angustidens, Arctodus underwent the opposite transformation, transitioning from the medium-sized A. pristinus to the gigantic A. simus by the end of the Pleistocene. ^[2] Except for an extraordinarily large specimen of A. angustidens, the largest specimens of A. simus and A. angustidens are said to be comparable to one another, ^{[11] [12]} and match the absolute upper size limit (~1000kg) of a terrestrial carnivore (based on the more restrictive energy base for a carnivorous diet). ^{[13] [14] [15]}

Cladogram

Below is a cladogram exploring the relationships between species of Arctotherium. ^{[1] [8]}

	Tremarctos
	A. vetustum A. wingei A. angustidens A. bonariense A. tarijense

Description

Taxonomy

The last short-faced bear, and the ecological successor of A. wingei, is the spectacled bear.

Arctotherium was named by Hermann Burmeister in 1879. Tremarctinae (and therefore Arctotherium) appeared to have disproportionately shorter snouts compared to most modern bears, hence the name "short-faced" was given to them. This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with ursine bears; Arctotherium had a deeper but not a shorter face than most living bears. ^[12] To differentiate between the species size can sometimes help, but cranial and dental features need to be examined for a definite identification. ^[16] The upper canine is very similar between species of Arctotherium, differing mainly in size. The canine of A. wingei is the smallest among the species. The lower canine of A. wingei presents two enamel ridges as in A. angustidens and A. tarijense, while in A. vetustum and A. bonariense there are three ridges. In A. vetustum, the distal ridge is very small and the mesial ridge is small, while in A. angustidens and A. tarijense both ridges are large. ^[17]

The shape of the elbow joint suggests the possibility of semi-arboreal locomotion for Arctodus sp ., Arctotherium bonariense, and A. wingei, but the size of the elbow joint does not. As the medial epicondyle is particularly expanded in these species, it is likely that (as for the giant panda) the fossil Arctodus and Arctotherium retained this feature in relation to their higher degree of forelimb dexterity. As these genera convergently evolved towards an increased body size, this high degree of proximal dexterity may have been advantageous for a scavenging lifestyle, ^[4] and therefore retained in the Tremarctinae lineage in spite of size evolution. ^[18]

Size

Arctotherium species ranged between a variety of sizes, both between species and individuals of the same species. ^[2] The sole remaining Tremarctine bear, the spectacled bear, exhibits strong sexual dimorphism, with adult males being 30%–50% larger than females. ^[10] Phylogenetic bracketing, along with Arctotherium's ability to exploit a variety of resource rich/poor environments and niches, can help explain Arctotherium's morphological diversity.

Various attempts to calculate each species' body mass have been made; for example, a 2006 study calculated the mean weight of two species, A. bonariense at ~110 kg (243 lb) (hypothetical typical weight range = 106–122 kg (234–269 lb)), and A. tarijense at ~139 kg (306 lb) (102–189 kg (225–417 lb)). ^{[19] [20]}

According to a 2009 study, the weight ranges for Arctotherium were calculated as follows- A. wingei at 51 kg-150 kg, A. vetustum at 102–300 kg (225–661 lb), A. tarijense at 135–400 kg (298–882 lb), A. bonariense between 171–500 kg (377–1,102 lb), and A. angustidens at 412–1,200 kg (908–2,646 lb). The study considered each end figure as the maximum hypothetical weight. ^[11] Further studies calculated an A. tarijense specimen's weight (MACN 971) at 231 kg (509 lb), ^[8] and A. wingei specimens from the Brazilian intertropical region at ~83 kg (183 lb). ^[21]

An extraordinarily large specimen of A. angustidens recovered in 2011 from Buenos Aires shows an individual estimated, using the humerus, to weigh between 983 and 2,042 kg (2,167 and 4,502 lb). However, the authors consider the upper limit as improbable, and say that 1,588 to 1,749 kg (3,501 to 3,856 lb) is more likely. An estimated standing height for this A. angustidens individual is between 3.4 and 4.3 m (11 and 14 ft). It would still make the species the largest bear ever found, and contender for the largest carnivorous land mammal known. ^[2]

Distribution and habitat

class=notpageimage|

Distribution map of Arctotherium

Legend: Arctotherium sp. A. angustidens. A. bonariense A. tarijense

A. vetustum A. wingei

Almost all Arctotherium species appear to be largely restricted to the Southern Cone, particularly Argentina, with the richest records being in the Buenos Aires Province. ^[10] The exceptions are the Tarija formation in southern Bolivia where three species have been recovered, ^[9] a possible record of A. vetustum in Brazil, ^[1] unassigned Arctotherium sp. postcranial remains from Rio Grande do Sul, ^[22] a Blancan-age unassigned Arctotherium tooth from El Salvador, ^[6] and A. wingei, which almost exclusively inhabited a more northern range. ^[9]

By the Late Pleistocene, A. tarijense held domain over the open and semi-arid Pampas and Patagonian habitats east of the Andes, inhabiting Argentina, Patagonian Chile, ^{[23] [24]} southern Bolivia, and Uruguay, ^[25] although A. bonariense may have also been contemporary in Late Pleistocene Uruguay. ^[26] A. tarijense has been described as having a very low density of fossil material in Patagonia. ^[24]

On the other hand, A. wingei spanned across the northern, more mixed/forested and tropical parts of the continent, ^[27] throughout the tropical savanna forests of Brazil to Bolivia, ^{[17] [28]} Venezuela, ^[9] and into North America (Belize and the Yucatán Peninsula, Mexico). ^[29]

Paleobiology

Relationship with other bears

Tremarctos does not appear in the South American fossil record until the Holocene, ^[30] suggesting that the extant spectacled bear descends from an independent, later dispersal event from North America to that of Arctotherium, ^{[4] [12] [31]} possibly after A. wingei became extinct in the Americas. ^[29] The modern spectacled bear may have hybridised with Arctotherium as they migrated southwards into South America. ^[32] However, the ranges of the spectacled bear, a specialist of highland Andean forests, and the more open adapted Arctotherium, could have co-existed in South America. ^[9]

Interaction with humans

The remains of A. wingei in the Hoyo Negro of the Yucatán appear to be in association with human remains. ^[33]

Paleoecology

Late Pliocene & Early Pleistocene

The oldest known specimen of Arctotherium consists of a baby tooth (dp4 molar) found in the Río Tomayate locality of Cuscatlán Formation of El Salvador, along with a partial Borophagus skull, dated to the latest Pliocene (2.588 Ma). The archaic form and size of the tooth is closest to A. angustidens, however as only one other baby tooth has been recovered from Arctotherium (A. tarijense), the tooth was only confidently assigned at the genus level as Arctotherium sp. ^[6]

Arctotherium only reappears in the fossil record 1 million years ago as A. angustidens, from the Buenos Aires province of Argentina. A. angustidens is the only known species of Arctotherium from the Early Pleistocene. ^{[2] [6]}

The first recorded Arctotherium specimens in South America occur alongside the earliest known South American records of several other carnivorans: the sabre-toothed cats Smilodon and Homotherium , the puma (Puma concolor), the jaguar (Panthera onca), some large 25–35 kg (55–77 lb) canids, and several smaller (<15 kg (33 lb)) mustelids, canids, felids and mephitids. ^{[4] [34]}

The North American carnivorans that invaded South America, including short-faced bears and Smilodon , probably quickly adopted the predatory niches formerly occupied by the native typical South American groups such as metatherian sparassodonts and phorusracids that had largely gone extinct shortly prior to their arrival. ^[2]

A. angustidens

In the Ensenadan, A. angustidens was only rivalled in size by Smilodon populator , with Theriodictis platensis , Canis gezi, ^[35] Protocyon scagliorum, Panthera onca and pumas rounding out the predator guild in the Early Pleistocene Argentina. The extinction of the scavenger-niche specialist procyonid Chapalmalania during this faunal turnover event is hypothesized as being the gateway for A. angustidens' gigantism. ^{[4] [20]} Using carbon isotopes, A. angustidens' diet has been posited to be omnivorous with a preference towards large quantities of meat. ^{[20] [36]} Beyond the scavenging of mega-herbivore carcasses, the type of tooth wear present amongst A. angustidens specimens, in addition to the frequency of broken teeth from most specimens (especially at older ages), suggests the active predation of large vertebrates, including but not limited to horses, tapirs, camelids, macraucheniids, glyptodonts, giant ground sloths, toxodontids, and gomphotheres by A. angustidens. ^{[36] [24]} Of the dentition known from later Arctotherium species, only one specimen of A. bonariense exhibits the same cracked teeth which A. angustidens had, although extreme wear of the occlusal molar surface is common throughout the genus. ^[36] Moreover, pathologies found on a huge specimen of A. angustidens, being multiple deep injuries which had long healed despite infection, ^[2] demonstrate a lifestyle of conflict.

Three A. angustidens individuals were discovered in a paleoburrow together (postulated to have been a mother with adolescent cubs), ^[37] which opens the possibility that A. angustidens lived in family groups. A. tarijense and A. wingei are also hypothesized to have utilised dens. ^[38] In contrast with the spectacled bear's tropical and temperate habitat, Pleistocene Argentina's seasonal and often harsh climate suggests quasi-hibernation would have been an effective strategy for survival, as ursine bears do today. ^[37] A. angustidens is thought to have reoccupied caves excavated by Xenarthra, such as the mylodonts Glossotherium and Scelidotherium , and the pampatheriid Pampatherium . ^[39] As suitable paleoburrows are rare before the Great American Interchange, it has been suggested that predation and competition for dens by the newly arrived eutherian carnivores, especially by A. angustidens, increased the rate of xenarthran cave excavations. ^[38] The evolution of highly-modified spiny osteoderms in Pleistocene-era Glyptodon has been attributed to the arrival of large carnivorans such as A. angustidens in South America. ^[40]

Middle Pleistocene onwards

Camelids inhabiting semi-arid plains, such as this Lama guanicoe , would have been favoured prey items and habitat for several southern species of Arctotherium.

It has been suggested that as a diverse carnivore guild became established in South America, the Arctotherium genus began to revert to more classic ursid diets as the ecosystem matured in the Middle Pleistocene. ^{[12] [41]} After A. angustidens became extinct, two forms begin to appear in the fossil record. The A. bonariense / A. tarijense species complex was composed of adaptable, cosmopolitan omnivores, ^[8] whereas A. vetustum & A. wingei were largely herbivorous. ^[2] However, as A. vetustum and A. wingei are the most archaic species of Arctotherium, their lineage must have existed before the emergence of A. angustidens in the Enseadan period of the Early Pleistocene. ^[1]

A. bonariense is believed to have convergently evolved several adaptations with Arctodus simus and Agriotherium / Huracan , such as proportionally longer limbs, very large body size, short broad rostrums, premasseteric fossa on the mandible, and possible carnassial shears. ^[42] Additionally, the diet of A. wingei was not necessarily orthodox, with carnivory likely peaking in times of resource instability. ^[21] For example, several bite marks on recovered fossils of herbivores, such as Glossotherium and Equus , are suggested to have been inflicted by scavenging short-faced bears across Lujanian South America. ^{[20] [43]}

A. bonariense & A. tarijense

A. bonariense and A. tarijense had a typical prey weight of 100 kg (220 lb), with a maximum of 300 kg (661 lb). ^[19] A. tarijense competed against Smilodon populator , giant jaguars ( Panthera onca mesembrina ), pumas, Lycalopex, Cerdocyon, Conepatus, Didelphis, and Dusicyon avus in Late Pleistocene Argentina, ^{[44] [45]} occasionally hunting camelids and horses as a supplement to scavenging, smaller prey and herbivory. ^[41] A. tarijense was highly carnivorous, with scavenging likely making up a considerable portion of its diet. ^[46] Although carnivory increased the further south Arctotherium lived, carbon isotopes suggest that A. tarijense's prey weight limit peaked at 300 kg, leaving the (subadult and younger) mega-mammals, such as the gomphotheres, giant ground sloths, and toxodontids, to Smilodon populator and giant jaguars. ^[19] Smilodon fatalis , Arctotherium bonariense, Canis nehringi, maned wolves, and humans would have also joined this predator guild at various stages of the Lujanian. ^{[19] [44] [47]} However, a fragmented Arctotherium c.f. tarijense tooth from Baño Nuevo-1 cave in southern Chile preserves cavities, which could be interpreted as a consequence of consuming carbohydrate-rich foods such as fruit or honey. A further microwear analysis attempt of the tooth in 2015 was complicated by hard plant and bone consumption causing similar damage to teeth in omnivores. ^[24]

A. vetustum & A. wingei

Tropical savanna forests and grasslands, such as the modern Cerrado, would have supplanted the Amazon as the dominant biome of Pleistocene South America, and stretched into Central America. This was A. wingei's preferred habitat.

Along with clues from various teeth of A. wingei, ^{[12] [17]} carbon isotope studies suggest that A. wingei, at least in the Brazilian intertropical region, were highly herbivorous, specialising in C3 vegetative matter such as fruits and leaves. ^{[21] [48]} This is not to diminish potential carnivory in A. wingei, as the same study pointed to isotope spikes indicating the consumption of the ground sloth Nothrotheriummaquinense (hypothesized as a preference for younger individuals and opportunistic scavenging), and A. wingei itself, which could represent cannibalism for juveniles or cubs, as observed in American black bears and polar bears. ^[21] According to a 2021 study, the maximum prey for A. wingei would be around its own bodyweight (~83 kg (183 lb)). ^[21]

In the low-density savanna forests of the Brazilian intertropical region, ^[49] A. wingei, pumas and jaguars played a supporting role to the (also likely solitary) Smilodon populator 's dominance of the regional predator guild, avoiding competition with Protocyon troglodytes in more open savanna. ^{[21] [48] [50]} Being smaller and more herbivorous, A. wingei would have also likely competed with other smaller carnivorans present in the BIR, such as jaguarundi, Lycalopex , Chrysocyon , Cerdocyon , Theriodictis , Speothos , Nasua , Procyon , Eira , Conepatus , Galictis , and Leopardus. ^[17] Additionally, as dire wolves (Aenocyon dirus) and Smilodon fatalis inhabited north-western South America, and were joined by American lions, grey wolves and coyotes in Central America, ^{[51] [52] [29] [53]} A. wingei would have been a member of various predator guilds across the species' range. A. wingei's association with Protocyon in the terminal Pleistocene of the Yucatán, another animal previously thought to be endemic to South America, suggests a complex relationship of faunal interchange long after the Great American Interchange. ^[29]

Paleo-ecological reconstructions

Although mostly herbivorous, the modern spectacled bear is on occasion an active predator. The spectacled bear has several hunting techniques- principally, the bear surprises or overpowers its prey, mounts its back, and consumes the immobilised animal while still alive, pinning the prey with its weight, large paws and long claws. Alternatively, the bear pursues the prey into rough terrain, hillsides, or precipices, provoking its fall and/or death. After death, the prey is dragged to a safe place (usually a nest over a tree, or a forested area) and consumed, leaving only skeletal remains. These behaviours have been suggested as Arctotherium's hunting strategies as well. ^[36] However, although the spectacled bear is capable of climbing trees, Arctotherium is thought to be non-arboreal. ^{[18] [37]}

Extinction

The last known records of Arctotherium are an ambiguous find of A. bonariense from Uruguay (cf./aff, either ~36,900 or ~14,485 BP of the Sopas Formation, ^[54] A. tarijense at 10,345 BP in the Cueva Del Puma, Patagonia, Chile, ^[24] and A. wingei at 12,850 BP in the Sistema Sac Actun (Yucatán), Mexico, ^[29] with a possible record of 9,000 BP in Muaco, Venezuela. ^[9]

Globally, in the Quaternary Extinction Event, extinction favoured 'conservative morphologies' in ursid body plans, such as those found in the T. ornatus . ^[2]

References

1. Soibelzon, L.H.; Tonni, E.P.; Bond, M. (2005). "The fossil record of South American short-faced bears (Ursidae, Tremarctinae)". Journal of South American Earth Sciences . 20 (1–2): 105–113. Bibcode:2005JSAES..20..105S. doi:10.1016/j.jsames.2005.07.005 . Retrieved 2019-02-21.
2. Soibelzon, L.H.; Schubert, B.W. (2011). "The Largest Known Bear, Arctotherium angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears". Journal of Paleontology . 85 (1): 69–75. CiteSeerX   10.1.1.870.2014 . doi:10.1666/10-037.1. S2CID   129585554.
3. Meloro, Carlo; de Oliveira, Alessandro Marques (2019-03-01). "Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils". Journal of Mammalian Evolution. 26 (1): 133–146. doi: 10.1007/s10914-017-9413-x . ISSN   1573-7055. S2CID   25839635.
4. Mitchell, K. J.; Bray, S. C.; Bover, P.; Soibelzon, L.; Schubert, B. W.; Prevosti, F.; Prieto, A.; Martin, F.; Austin & Alan Cooper, J. J. (2016). "Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America". Biology Letters . 12 (4): 20160062. doi:10.1098/rsbl.2016.0062. PMC   4881349 . PMID   27095265.
5. Krause, Johannes; Unger, Tina; Noçon, Aline; Malaspinas, Anna-Sapfo; Kolokotronis, Sergios-Orestis; Stiller, Mathias; Soibelzon, Leopoldo; Spriggs, Helen; Dear, Paul H.; Briggs, Adrian W.; Bray, Sarah CE (2008-07-28). "Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene-Pliocene boundary". BMC Evolutionary Biology. 8 (1): 220. Bibcode:2008BMCEE...8..220K. doi: 10.1186/1471-2148-8-220 . ISSN   1471-2148. PMC   2518930 . PMID   18662376.
6. Soibelzon, L.H.; Romero, M.R.; Huziel Aguilar, D.; Tartarini, V.B. (2008). "A Blancan (Pliocene) short-faced bear from El Salvador and its implications for Tremarctines in South America". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen . 250: 1–8. doi:10.1127/0077-7749/2008/0250-0001 . Retrieved 2019-02-21.
7. "Remains of 700,000-year-old giant bear found in Argentina's San Pedro". The Week. Retrieved 2022-02-07.
8. Arnaudo, Maria Eugenia; Bona, Paula; Soibelzon, Leopoldo Hector; Schubert, Blaine W. (December 2016). "Anatomical study of the auditory region of Arctotherium tarijense (Ursidae, Tremarctinae), an extinct short-faced bear from the Pleistocene of South America". Journal of Anatomy. 229 (6): 825–837. doi:10.1111/joa.12525. ISSN   0021-8782. PMC   5108154 . PMID   27460048.
9. Soibelzon, L.H.; Rincón, A.D. (2007). "The fossil record of the short-faced bears (Ursidae, Tremarctinae) from Venezuela. Systematic, biogeographic, and paleoecological implications". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen . 244 (3): 287–298. CiteSeerX   10.1.1.827.6635 . doi:10.1127/0077-7749/2007/0244-0287.
10. García-López, Daniel; Ortiz, Pablo; Madozzo Jaén, M.; Moyano, M. (2008-12-12). "First Record of Arctotherium (Ursidae, Tremarctinae) in Northwestern Argentina and its Paleobiogeographic Significance". Journal of Vertebrate Paleontology. 28 (4): 1232–1237. Bibcode:2008JVPal..28.1232L. doi:10.1671/0272-4634-28.4.1232. hdl: 11336/79528 . S2CID   86213882.
11. Soibelzon, Leopoldo; Tarantini, V.B. (2009-01-01). "Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae)". Revista del Museo Argentino de Ciencias Naturales. Nueva Serie. 11: 243–254. doi: 10.22179/REVMACN.11.263 .
12. Figueirido, Borja; Soibelzon, Leopoldo H. (2009-08-19). "Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics: Palaeoecology in extinct tremarctines". Lethaia. 43 (2): 209–222. doi:10.1111/j.1502-3931.2009.00184.x.
13. Carbone, Chris; Teacher, Amber; Rowcliffe, J. Marcus (2007-01-16). "The Costs of Carnivory". PLOS Biology. 5 (2): e22. doi: 10.1371/journal.pbio.0050022 . ISSN   1545-7885. PMC   1769424 . PMID   17227145.
14. Smith, Felisa A.; Boyer, Alison G.; Brown, James H.; Costa, Daniel P.; Dayan, Tamar; Ernest, S. K. Morgan; Evans, Alistair R.; Fortelius, Mikael; Gittleman, John L.; Hamilton, Marcus J.; Harding, Larisa E.; Lintulaakso, Kari; Lyons, S. Kathleen; McCain, Christy; Okie, Jordan G. (2010-11-26). "The Evolution of Maximum Body Size of Terrestrial Mammals". Science. 330 (6008): 1216–1219. Bibcode:2010Sci...330.1216S. doi:10.1126/science.1194830. ISSN   0036-8075. PMID   21109666.
15. Emslie, Steven D.; Czaplewski, Nicholas J. (1985-11-15). "A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology". Contributions in Science. 371: 1–12. doi: 10.5962/p.226835 . S2CID   133986793.
16. Pereira, Alexsander Trevisan (18 May 2021). "Ursidae (Mammalia, Carnivora) do Pleistoceno do Rio Grande do Sul, Brasil" (PDF). Federal University of Santa Catarina.
17. Rodrigues, Shirlley; Avilla, Leonardo S.; Soibelzon, Leopoldo H.; Bernardes, Camila (2014-11-28). "Late Pleistocene carnivores (Carnivora: Mammalia) from a cave sedimentary deposit in northern Brazil". Anais da Academia Brasileira de Ciências. 86 (4): 1641–1655. doi: 10.1590/0001-3765201420140314 . hdl: 11336/9084 . ISSN   0001-3765. PMID   25590705. S2CID   3358820.
18. Meloro, Carlo; de Oliveira, Alessandro Marques (2019-03-01). "Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils". Journal of Mammalian Evolution. 26 (1): 133–146. doi: 10.1007/s10914-017-9413-x . ISSN   1573-7055. S2CID   25839635.
19. Prevosti, Francisco; Vizcaíno, Sergio (2006-09-01). "Paleoecology of the large carnivore guild from the Late Pleistocene of Argentina". Acta Palaeontologica Polonica. 51: 407–422.
20. Chichkoyan, Karina; Figueirido, Borja; Belinchón, Margarita; Lanata, José; Moigne, Anne-Marie; Martínez-Navarro, Bienvenido (2017-05-09). "Direct evidence of megamammal-carnivore interaction decoded from bone marks in historical fossil collections from the Pampean region". PeerJ. 5: e3117. doi: 10.7717/peerj.3117 . PMC   5426367 . PMID   28503369.
21. Dantas, Mário André Trindade; Bernardes, Camila; Asevedo, Lidiane; Rabito Pansani, Thaís; De Melo França, Lucas; Santos De Aragão, Wilcilene; Da Silva Santos, Franciely; Cravo, Elisa; Ximenes, Celso (2021-06-07). "Isotopic palaeoecology (δ13C) of three faunivores from Late Pleistocene of the Brazilian intertropical region". Historical Biology. 34 (3): 507–514. Bibcode:2022HBio...34..507D. doi:10.1080/08912963.2021.1933468. ISSN   0891-2963. S2CID   236272572.
22. Trevisan, Alexsander; Ribeiro, Ana Maria; Da-Rosa, Átila Augusto Stock; Hadler, Patrícia (20 September 2023). "Ursidae (Mammalia, Carnivora) from the Quaternary of western Rio Grande do Sul, Brazil: Taxonomical, stratigraphic, and chronological aspects". Quaternary International . 668: 14–26. Bibcode:2023QuInt.668...14T. doi:10.1016/j.quaint.2023.06.013 . Retrieved 27 March 2024– via Elsevier Science Direct.
23. Prevosti, F.J.; Soibelzon, L.H.; Prieto, A.; San Román, M.; Morello, F. (2003). "The Southernmost bear: Pararctotherium (Carnivora, Ursidae, Tremarctinae) in the latest Pleistocene of Southern Patagonia, Chile". Journal of Vertebrate Paleontology . 23 (3): 709–712. doi:10.1671/0272-4634(2003)023[0709:TSBPCU]2.0.CO;2. S2CID   86116001 . Retrieved 2019-02-21.
24. López Mendoza, Patricio; Mena, Francisco; Bostelmann, Enrique (2015-07-22). "Presence of Arctotherium (Carnivora, Ursidae, Tremarctinae) in a pre-cultural level of Baño Nuevo-1 cave (Central Patagonia, Chile)". Estudios Geológicos. 71 (2): 41–367. doi: 10.3989/egeol.42011.357 .
25. Ubilla, Martín; Rinderknecht, Andrés; Corona, Andrea; Perea, Daniel (June 2018). "Mammals in Last 30 to 7 ka Interval (Late Pleistocene-Early Holocene) in Southern Uruguay (Santa Lucía River Basin): Last Occurrences, Climate, and Biogeography". Journal of Mammalian Evolution. 25 (2): 291–300. doi:10.1007/s10914-017-9380-2. ISSN   1064-7554. S2CID   254697032.
26. Corona, Andrea; Perea, Daniel; Toriño, Pablo; Goso, Cesar (2012). "Taphonomy, sedimentology and chronology of a fossiliferous outcrop from the continental Pleistocene of Uruguay". Revista Mexicana de Ciencias Geológicas. 29 (2): 514–525 – via ResearchGate.
27. "Figura 5. Distribución inferida de algunos mamíferos grandes y..." ResearchGate. Retrieved 2022-02-11.
28. Trajano, E.; Ferrarezzi, H. (1995). "A Fossil Bear from Northeastern Brazil, with a Phylogenetic Analysis of the South American Extinct Tremarctinae (Ursidae)". Journal of Vertebrate Paleontology. 14 (4): 552–561. Bibcode:1995JVPal..14..552T. doi:10.1080/02724634.1995.10011577. ISSN   0272-4634. JSTOR   4523593.
29. Schubert, B. W.; Chatters, J. C.; Arroyo-Cabrales, J.; Samuels, J. X.; Soibelzon, L. H.; Prevosti, F. J.; Widga, C.; Nava, A.; Rissolo, D.; Erreguerena, P. L. (2019). "Yucatán carnivorans shed light on the Great American Biotic Interchange". Biology Letters. 15 (5): 20190148. doi:10.1098/rsbl.2019.0148. PMC   6548739 . PMID   31039726. 20190148.
30. "Access Suspended". bioone.org. doi:10.2192/08gr017r1.1. S2CID   86731722 . Retrieved 2022-02-05.
31. Prevosti, Francisco J.; Soibelzon, Leopoldo H.; Prieto, Alfredo; Roman, Manuel San; Morello, Flavia (2003). "The Southernmost Bear: Pararctotherium (Carnivora, Ursidae, Tremarctinae) in the Latest Pleistocene of Southern Patagonia, Chile". Journal of Vertebrate Paleontology. 23 (3): 709–712. doi:10.1671/0272-4634(2003)023[0709:TSBPCU]2.0.CO;2. ISSN   0272-4634. JSTOR   4524368. S2CID   86116001.
32. Salis, Alexander T.; Gower, Graham; Schubert, Blaine W.; Soibelzon, Leopoldo H.; Heiniger, Holly; Prieto, Alfredo; Prevosti, Francisco J.; Meachen, Julie; Cooper, Alan; Mitchell, Kieren J. (2021-03-10). "Ancient genomes reveal hybridisation between extinct short-faced bears and the extant spectacled bear (Tremarctos ornatus)": 2021.02.05.429853. doi:10.1101/2021.02.05.429853. S2CID   231885176.{{cite journal}}: Cite journal requires |journal= (help)
33. Arroyo-Cabrales, J. (2016). "North American ursid (mammalia: ursidae) defaunation from Pleistocene to recent". Cranium. 33 (1): 51–56. OCLC   1227719621.
34. Chimento, Nicolas; Dondas, Alejandro (2018-09-01). "First Record of Puma concolor (Mammalia, Felidae) in the Early-Middle Pleistocene of South America". Journal of Mammalian Evolution. 25 (3): 381–389. doi:10.1007/s10914-017-9385-x. S2CID   16249074.
35. Prevosti, Francisco J. (2010). "Phylogeny of the large extinct South American Canids (Mammalia, Carnivora, Canidae) using a "total evidence" approach". Cladistics. 26 (5): 456–481. doi: 10.1111/j.1096-0031.2009.00298.x . ISSN   1096-0031. PMID   34875763. S2CID   86650539.
36. Soibelzon, Leopoldo H.; Grinspan, Gustavo A.; Bocherens, Hervé; Acosta, Walter G.; Jones, Washington; Blanco, Ernesto R.; Prevosti, Francisco (November 2014). "South American giant short-faced bear (Arctotherium angustidens) diet: evidence from pathology, morphology, stable isotopes, and biomechanics". Journal of Paleontology. 88 (6): 1240–1250. Bibcode:2014JPal...88.1240S. doi:10.1666/13-143. hdl: 11336/34149 . ISSN   0022-3360. S2CID   54869873.
37. Fowler, Nicholas L.; Spady, Thomas J.; Wang, Guiming; Leopold, Bruce D.; Belant, Jerrold L. (October 2021). "Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae". Mammal Review. 51 (4): 465–481. doi:10.1111/mam.12246. ISSN   0305-1838. S2CID   233847639.
38. Soibelzon, Leopoldo H.; Pomi, Lucas H.; Tonni, Eduardo P.; Rodriguez, Sergio; Dondas, Alejandro (2009-09-01). "First report of a South American short-faced bears' den (Arctotherium angustidens): palaeobiological and palaeoecological implications". Alcheringa: An Australasian Journal of Palaeontology. 33 (3): 211–222. Bibcode:2009Alch...33..211S. doi:10.1080/03115510902844418. ISSN   0311-5518. S2CID   55636895.
39. Dondas, Alejandro; Isla, Federico I.; Carballido, José L. (December 2009). "Paleocaves exhumed from the Miramar Formation (Ensenadan Stage-age, Pleistocene), Mar del Plata, Argentina". Quaternary International. 210 (1–2): 44–50. Bibcode:2009QuInt.210...44D. doi:10.1016/j.quaint.2009.07.001.
40. Zurita, Alfredo Eduardo; Soibelzon, Leopoldo Hector; Soibelzon, Esteban; Gasparini, Germán Mariano; Cenizo, Marcos Martín; Arzani, Héctor (2010-01-01). "Accessory protection structures in Glyptodon Owen (Xenarthra, Cingulata, Glyptodontidae)". Annales de Paléontologie. 96 (1): 1–11. Bibcode:2010AnPal..96....1Z. doi:10.1016/j.annpal.2010.01.001. ISSN   0753-3969.
41. Prevosti, Francisco J. (November 2012). "The mammalian predator guild of the Southern Patagonia during the late Pleistocene: ecomorphology, taphonomy and stable isotopes". Quaternary International. 279–280: 386. Bibcode:2012QuInt.279S.386P. doi:10.1016/j.quaint.2012.08.1204.
42. Sorkin, B. (March 2006). "Ecomorphology of the giant short-faced bears Agriotherium and Arctodus". Historical Biology. 18 (1): 1–20. Bibcode:2006HBio...18....1S. doi:10.1080/08912960500476366. ISSN   0891-2963.
43. Avilla, Leonardo Santos; Machado, Helena; Araujo-Junior, Herminio Ismael de; Mothe, Dimila; Rotti, Alline; Oliveira, Karoliny de; Maldonado, Victoria; Figueiredo, Ana Maria Graciano; Kinoshita, Angela; Baffa, Oswaldo (2018-11-20). "Pleistocene EQUUS (Equidae: Mammalia) from Northern Brazil: Evidence of Scavenger Behavior by Ursids on South American Horses". Ameghiniana. 55 (5): 517–530. doi:10.5710/AMGH.05.07.2018.3069. ISSN   1851-8044. S2CID   134160124.
44. Fariña, Richard A.; Czerwonogora, Ada; Giacomo, Mariana Di (March 2014). "Splendid oddness: revisiting the curious trophic relationships of South American Pleistocene mammals and their abundance". Anais da Academia Brasileira de Ciências. 86 (1): 311–331. doi: 10.1590/0001-3765201420120010 . ISSN   0001-3765. PMID   24676170.
45. Prieto, Alfredo; Labarca, Rafael; Victor, Sierpe (2010-06-01). "New evidence of the sabertooth cat Smilodon (carnivora: Machairodontinae) in the Late Pleistocene of Southern Chilean Patagonia". Revista Chilena de Historia Natural. 83 (2): 299–307. doi: 10.4067/S0716-078X2010000200010 .
46. Prevosti, Francisco J.; Martin, Fabiana M. (14 August 2013). "Paleoecology of the mammalian predator guild of Southern Patagonia during the latest Pleistocene: Ecomorphology, stable isotopes, and taphonomy". Quaternary International . 305: 74–84. doi:10.1016/j.quaint.2012.12.039 . Retrieved 5 November 2024– via Elsevier Science Direct.
47. Manzuetti, Aldo; Perea, Daniel; Ubilla, Martín; Rinderknecht, Andrés (2018-01-15). "First record of Smilodon fatalis Leidy, 1868 (Felidae, Machairodontinae) in the extra-Andean region of South America (late Pleistocene, Sopas Formation), Uruguay: Taxonomic and paleobiogeographic implications". Quaternary Science Reviews. 180: 57–62. Bibcode:2018QSRv..180...57M. doi:10.1016/j.quascirev.2017.11.024. ISSN   0277-3791.
48. Dantas, Mário; Cozzuol, Mario (2016-07-27), The Brazilian Intertropical Fauna from 60 to About 10 ka B.P.: Taxonomy, Dating, Diet, and Paleoenvironments, Springer, pp. 207–226, ISBN   978-3-319-39998-0 , retrieved 2022-02-08
49. Pansani, Thaís; Muniz, Fellipe; Cherkinsky, Alexander; Pacheco, Mirian; Dantas, Mário (2019-10-01). "Isotopic paleoecology (δ13C, δ18O) of Late Quaternary megafauna from Mato Grosso do Sul and Bahia States, Brazil". Quaternary Science Reviews. 221: 105864. Bibcode:2019QSRv..22105864P. doi:10.1016/j.quascirev.2019.105864. S2CID   202200336.
50. Dantas, Mário André Trindade; Araujo, Andre Vieira de; Silva, Laís Alves; Cherkinsky, Alexander (2022-01-01). "Panthera onca (Linnaeus, 1758) from the late Pleistocene of Brazilian Intertropical Region: taxonomy, habitat, isotopic diet composition, and isotopic niche overlap with extinct faunivores". Journal of South American Earth Sciences. 113: 103666. Bibcode:2022JSAES.11303666D. doi:10.1016/j.jsames.2021.103666. ISSN   0895-9811. S2CID   244836031.
51. "Figure 5. Geographic distribution of Panthera atrox in North America..." ResearchGate. Retrieved 2022-02-15.
52. Hody, James W.; Kays, Roland (2018-05-22). "Mapping the expansion of coyotes (Canis latrans) across North and Central America". ZooKeys (759): 81–97. Bibcode:2018ZooK..759...81H. doi: 10.3897/zookeys.759.15149 . ISSN   1313-2970. PMC   5974007 . PMID   29861647.
53. "Figure 2: Extinct (†) species geographic ranges in the Americas at..." ResearchGate. Retrieved 2022-02-18.
54. Ubilla, Martín; Corona, Andrea; Rinderknecht, Andrés; Perea, Daniel; Verde, Mariano (2016-07-27), Marine Isotope Stage 3 (MIS 3) and Continental Beds from Northern Uruguay (Sopas Formation): Paleontology, Chronology, and Climate, Springer, pp. 183–205, ISBN   978-3-319-39998-0 , retrieved 2022-02-17