Hubbry Logo
AndrewsarchusAndrewsarchusMain
Open search
Andrewsarchus
Community hub
Andrewsarchus
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Andrewsarchus
Andrewsarchus
Andrewsarchus
View on Wikipedia
from Wikipedia

Andrewsarchus
Temporal range: Middle Eocene, 47.8–37.71 Ma
Holotype skull of A. mongoliensis, held at the American Museum of Natural History
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Clade: Cetancodontamorpha
Family: †Andrewsarchidae
Szalay & Gould, 1966[2]
Genus: †Andrewsarchus
Osborn, 1924[1]
Type species
†Andrewsarchus mongoliensis
Osborn, 1924
Other species
  • †Andrewsarchus crassum
    Ding et al., 1977[3]
Synonyms
Genus synonymy
Species synonymy
  • A. mongoliensis
      • Paratriisodon henanensis
        Chow, 1959[5]
      • Paratriisodon gigas
        Chow, Li, & Chang, 1973[6]

Andrewsarchus (/ˌændruːˈsɑːrkəs/), meaning "Andrews' ruler", is an extinct genus of artiodactyl that lived during the Middle Eocene in what is now China. The genus was first described by Henry Fairfield Osborn in 1924 with the type species A. mongoliensis based on a largely complete cranium. A second species, A. crassum, was described in 1977 based on teeth. A mandible, formerly described as Paratriisodon, does probably belong to Andrewsarchus as well. The genus has been historically placed in the families Mesonychidae or Arctocyonidae, or was considered to be a close relative of whales. It is now regarded as the sole member of its own family, Andrewsarchidae, and may have been related to entelodonts. Fossils of Andrewsarchus have been recovered from the Middle Eocene Irdin Manha, Lushi and Dongjun Formations of Inner Mongolia, each dated to the Irdinmanhan Asian land mammal age (Lutetian–Bartonian stages, 48–38 million years ago).

Andrewsarchus has historically been reputed as the largest terrestrial, carnivorous mammal given its skull length of 83.4 cm (32.8 in), though its overall body size was probably overestimated due to inaccurate comparisons with mesonychids, and it did not have the meat-slicing carnassial teeth of a hypercarnivore. Its incisors are arranged in a semicircle, similar to entelodonts, with the second rivalling the canine in size. The premolars are again similar to entelodonts in having a single cusp. The crowns of the molars are wrinkled, suggesting it was omnivorous or a scavenger. Unlike many modern scavengers, a reduced sagittal crest and flat mandibular fossa suggest that Andrewsarchus likely had a fairly weak bite force.

Taxonomy

[edit]

Early history

[edit]

The holotype of Andrewsarchus mongoliensis is a mostly complete cranium (specimen number AMNH-VP 20135).[7] It was recovered from the lower Irdin Manha Formation of Inner Mongolia during a 1923 palaeontological expedition conducted by the American Museum of Natural History of New York.[1][8] Its discoverer was Kan Chuen-pao,[9] also known as "Buckshot"[10], a local man who trained at the AMNH and became assistant to the expedition's lead paleontologist, Walter Granger. Granger initially identified the fossil as the skull of an Entelodon.[10] A drawing of the skull was sent to the museum, where it was identified by William Diller Matthew as belonging to "the primitive Creodonta of the family Mesonychidae".[1] The specimen itself arrived at the museum and was described by Osborn in 1924. Its generic name honours Roy Chapman Andrews, the leader of the expedition, with the Ancient Greek archos (ἀρχός, "ruler") added to his surname.[1]

A second species of Andrewsarchus, A. crassum, was named by Ding Suyin and colleagues in 1977 on the basis of IVPP V5101,[11] a pair of teeth (the second and third lower premolars) recovered from the Dongjun Formation of Guangxi.[5][12]

Illustrated holotype skull of A. mongoliensis

In the 1957, Zhou Mingzhen and colleagues recovered a mandible, a fragmentary maxilla and several isolated teeth from the Lushi Formation of Henan, China, which correlates to the Irdin Manha Formation. The maxilla belonged to a skull that was crushed beyond recognition; it is likely from the same individual as the mandible.[4] Zhou described it in 1959 as Paratriisodon henanensis, and assigned it to Arctocyonidae. He further classified it as part of the subfamily Triisodontinae (now the family Triisodontidae) based on close similarities of the molars and premolars to those of Triisodon.[4] A second species, P. gigas, was named by Zhou and colleagues in 1973 for a molar also from the Lushi Formation. Three molars and an incisor from the Irdin Manha Formation were later referred to P. gigas.[13] Comparisons between the two genera were drawn as far back as 1969, when Frederick Szalay suggested that they either evolved from the same arctocyonid ancestors or that they were an example of convergent evolution.[14] Paratriisodon was first properly synonymised with Andrewsarchus by Leigh Van Valen in 1978, who did so without explanation.[15] Regardless, their synonymy was upheld by Maureen O'Leary in 1998, based on similarities between the molars and premolars of the two genera and their comparable body sizes.[5]

Classification

[edit]
Holotype skull cast of A. mongoliensis as seen from below

Andrewsarchus was initially regarded as a mesonychid,[1] and Paratriisodon as an arctocyonid.[13] In 1995, the former became the sole member of its own subfamily, Andrewsarchinae, within Mesonychia.[16] The subfamily was elevated to family level by Philip D. Gingerich in 1998, who tentatively assigned Paratriisodon to it.[17] In 1988, Donald Prothero and colleagues recovered Andrewsarchus as the sister taxon to whales.[18] It has since been recovered as a more basal member of Cetancodontamorpha, most closely related to entelodonts, hippos and whales.[19][20] In 2023, Yu and colleagues conducted a phylogenetic analysis of ungulates, with a particular focus on entelodontid artiodactyls. Andrewsarchus was recovered as part of a clade consisting of itself, Achaenodon, Erlianhyus, Protentelodon, Wutuhyus and Entelodontidae. It was found to be most closely related to Achaenodon and Erlianhyus, with which it formed a polytomy. A cladogram based on their phylogeny is reproduced below:[19]

Artiodactyla

Description

[edit]
Life restoration of the head of A. mongoliensis

When first describing Andrewsarchus, Osborn believed it to be the largest terrestrial, carnivorous mammal. Based on the length of the A. mongoliensis holotype skull, and using the proportions of Mesonyx, he estimated a total body length of 3.82 m (12.5 ft) and a body height of 1.89 m (6.2 ft).[1] However, considering cranial and dental similarities with entelodonts, Frederick Szalay and Stephen Jay Gould proposed that it had proportions less like mesonychids and more like them, and thus that Osborn's estimates were likely inaccurate.[2]

Skull

[edit]

The holotype skull of Andrewsarchus has a total length of 83.4 cm (2.74 ft), and is 56 cm (1.84 ft) wide at the zygomatic arches. The snout is greatly elongated, measuring one-and-a-half times the length of the basicranium,[1] and the portion of the snout in front of the canines resembles that of entelodonts.[2] Unlike entelodonts, however, the postorbital bar is incomplete.[19] The sagittal crest is reduced, and the mandibular fossa is relatively flat. Together, these attributes suggest a weak temporalis muscle and a fairly weak bite force. The hard palate is long and narrow.[2] The mandibular fossa is also offset laterally and ventrally from the basicranium, similar to the condition seen in mesonychids.[21] The mandible itself is long and shallow, characterised by a straight and relatively shallow horizontal ramus.[4] The masseteric fossa, the depression on the mandible to which the masseter attaches, is shallow. Symphyseal contact between the two mandibles is limited.[2]

Dentition

[edit]
Skull of Andrewsarchus compared to those of Mesonyx, an Alaskan brown bear and a wolf

The holotype cranium of Andrewsarchus demonstrates the typical placental tooth formula, of three incisors, one canine, four premolars and three molars per side,[2] though it is not clear whether the same applies to the mandible. The upper incisors are arranged in a semicircle in front of the canines, a trait that is shared with entelodonts. The second incisor is enlarged, and is almost the size of the canines.[2] This is partly because, while the canines were originally described as being "of enormous size",[1] they are relatively small in proportion to the rest of the dentition.[2] The upper premolars are elongate and consist of a single cusp, resembling those of entelodonts. The fourth premolar retains the protocone, though in a vestigial form.[1] Their roots are not confluent and lack a dentine platform, which are both likely to be adaptations to prolong the tooth's functional life after crown abrasion. The first molar is the smallest. The second is the widest, but has been heavily worn since fossilisation. The third has largely avoided that wear. The premolars and molars have wrinkled crowns, similar to the condition seen in suids and other omnivorous artiodactyls.[2] The tooth structure of the mandible (IVPP V5101) is difficult to determine, as nearly all are worn or broken. All of the right mandible's teeth are preserved save for the first premolar, which is instead preserved on the left mandible. The lower canine and the first premolar both point forwards.[2] The third molar is large, with talonids that have two cusps.[4]

Diet

[edit]

In his paper describing Andrewsarchus, Osborn suggested that it may have been omnivorous based on comparisons with entelodonts.[1] This conclusion was supported by Szalay and Gould, who use the heavily wrinkled crowns of the molars and premolars as supporting evidence,[2] as well as the close phylogenetic relationship between Andrewsarchus and entelodonts.[19][20] R. M. Joeckel, in 1990, suggested that it was likely an "omnivore-scavenger", and that it was an ecological analogue to entelodonts.[22] Lars Werdelin further suggested that it was a scavenger, or that it might have preyed on brontotheres.[23]

Palaeoecology

[edit]
Palaeogeography of Europe and Asia during the Middle Eocene with possible artiodactyl and perissodactyl dispersal routes

For much of the Eocene, a hothouse climate with humid, tropical environments with consistently high precipitations prevailed. Modern mammalian orders including the Perissodactyla, Artiodactyla and Primates (or the suborder Euprimates) appeared already by the Early Eocene, diversifying rapidly and developing dentitions specialized for folivory. The omnivorous forms mostly either switched to folivorous diets or went extinct by the Middle Eocene (Lutetian–Bartonian, 48–38 million years ago) along with the archaic "condylarths". By the Late Eocene (Priabonian, 38–34 million years ago), most of the ungulate form dentitions shifted from bunodont cusps to cutting ridges (i.e. lophs) for folivorous diets.[24][25]

The Irdin Manha Formation, from which the holotype of Andrewsarchus was recovered, consists of Irdinmanhan strata dated to the Middle Eocene.[26] Andrewsarchus mongoliensis comes from the IM-1 locality, dated to the lower Irdinmanhan,[27] from which the hyaenodontine Propterodon, the mesonychid Harpagolestes, at least three unnamed mesonychids,[2] the artiodactyl Erlianhyus,[28] the perissodactyls Deperetella and Lophialetes, the omomyid Tarkops, the glirian Gomphos, the rodent Tamquammys, and various indeterminate glirians are also known.[26][27] The Lushi Formation, from which the Paratriisodon henanensis specimen was recovered, was deposited at around the same time as the Irdin Manha Formation. The mesonychid Mesonyx, the pantodont Eudinoceras, the dichobunid Dichobune, the helohyid Gobiohyus, the brontotheres Rhinotitan and Microtitan, the perissodactyls Amynodon and Lophialetes, the ctenodactylid Tsinlingomys, and the lagomorph Lushilagus have been identified from the Lushi Formation.[29] The Dongjun Formation, from which A. crassum originates, is similarly Middle Eocene.[30] It preserves the nimravid Eusmilus, the anthracotheriid Probrachyodus, the pantodont Eudinoceras, the brontotheres Metatelmatherium and cf. Protitan, the deperetellids Deperetella and Teleolophus, the hyracodontid Forstercooperia, the rhinocerotids Ilianodon and Prohyracodon, and the amynodonts Amynodon, Gigantamynodon and Paramnyodon.[31]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Andrewsarchus

View on Grokipedia
from Grokipedia
Andrewsarchus mongoliensis is an extinct of large artiodactyl mammal that lived during the Middle Eocene epoch, approximately 45 million years ago, in what is now , . Known solely from a single enormous , it represents one of the most enigmatic large mammals of the , with its body size, locomotion, and inferred largely from cranial morphology and phylogenetic comparisons. The , measuring 834 mm in basal length and 560 mm in zygomatic width, is the largest known for any terrestrial carnivorous mammal, leading to initial estimates of a body length exceeding 3.8 meters and shoulder height around 1.9 meters, though these remain speculative without a complete . The specimen was discovered in 1923 by Kan Chuen Pao during the Third Central Asiatic Expedition of the , led by , in the Irdin Manha Formation of the . Named Andrewsarchus mongoliensis in honor of Andrews, it was formally described by in 1924, who classified it as a giant mesonychid—a group of wolf-like, hoofed carnivores—based on its robust and elongated , declaring it the largest terrestrial mammalian predator known at the time. The teeth, featuring large, shearing and robust molars, suggested a hypercarnivorous diet akin to that of modern large canids or felids, with comparisons drawn to the Eocene mesonychid Harpagolestes uintensis, whose skull was only half the size. Subsequent phylogenetic analyses, incorporating morphological data from basal ungulates, have reclassified Andrewsarchus outside and within Artiodactyla (even-toed ungulates), positioning it as a basal member closely related to entelodonts—pig-like omnivores known for their powerful jaws and scavenging habits. This revised affinity implies Andrewsarchus may have been omnivorous rather than strictly carnivorous, potentially scavenging or consuming tough vegetation alongside meat, similar to later entelodonts like and Dinohyus, to which Osborn himself noted superficial resemblances. Its placement near the base of Artiodactyla also aligns it distantly with modern groups such as and cetaceans, highlighting the diverse early radiation of even-toed ungulates in Eocene . Despite its iconic status in , the scarcity of fossils continues to fuel debate over its precise ecology and whether additional material might reveal a more pig-like or mesonychid-like form.

Discovery and Taxonomy

Discovery and Naming

The specimen of Andrewsarchus, a nearly complete cataloged as AMNH-VP 20135, was discovered in the spring of 1923 during the second year of the Central Asiatic Expeditions (1922–1925) led by for the . The find was made by Kan Chuen Pao, a young paleontological assistant, at a locality in the Irdin Manha Formation, , , a region known as the Valley of the Jewels for its rich deposits of and . Andrews himself described the upon initial identification as that of a "gigantic beast," sparking immediate excitement among the expedition team for its unprecedented size. In 1924, formally named the genus and species Andrewsarchus mongoliensis in a publication for the American Museum Novitates, honoring the expedition's leader (with "archus" derived from the Greek for "leader" or "chief"). Osborn described the type specimen as the cranium of a large from the Irdin Manha Formation, emphasizing its status as "the largest terrestrial which has thus far been discovered in any part of the world," with a basal length exceeding 83 cm—surpassing even the skulls of modern Alaskan brown bears. The description highlighted the elongated facial region and full eutherian , positioning it within early 20th-century understandings of mammalian during these landmark expeditions. A second species, A. crassum, was named in 1977 by Ding Suyin and colleagues based on isolated teeth (a second and first molar, IVPP V5101) from the Dongjun Formation in , . However, this assignment has been considered tentative due to the fragmentary nature of the material, with some researchers suggesting synonymy with other taxa such as Paratriisodon. The genus indicates a Middle Eocene temporal range (approximately 48–37 Ma) across these Asian formations.

Classification

Upon its initial description, Andrewsarchus was classified within the family by , who interpreted it as a giant wolf-like terrestrial predator based on the robust carnivorous and overall skull proportions of the specimen. This placement positioned it among other mesonychids, a group of Eocene carnivorans thought to represent primitive ungulate-like mammals with predatory adaptations. Subsequent analysis led to its reclassification into a distinct family, Andrewsarchidae, erected by Frederick S. Szalay and in recognition of its unique dental morphology, including enlarged premolars and specialized that deviated from typical mesonychid patterns. This revision sparked debates regarding its broader affinities, with some researchers proposing (even-toed ) relationships due to shared features like the astragalus morphology, while others suggested perissodactyl (odd-toed ) links based on cranial robusticity. Contemporary phylogenetic assessments have firmly relocated Andrewsarchus to the basal , a encompassing , cetaceans (whales), and hippopotamids, excluding mesonychid affinities. A 2023 analysis incorporating extensive morphological data from taxa positioned it as a close relative to entelodonts, Achaenodon, and Erlianhyus within this group, supported by shared synapomorphies in the auditory bulla and postcranial elements. Key ongoing debates center on its exclusion from true mesonychids, reinforced by the recognition that mesonychians lack close ties to cetacean origins, and its potential role in illuminating diversification toward even-toed ungulates and secondarily aquatic whales. The includes two : the A. mongoliensis from the Irdin Manha Formation and A. crassum from the Dongjun Formation. Cranial evidence underpins these revisions, with the elongated, low-roofed skull of Andrewsarchus exhibiting convergent hypercarnivorous traits—such as a narrow snout and robust zygomatic arches—comparable to those in other Eocene mammals like the hyaenodontid Hyaenodon, though differing in ungulate-specific features like the inflated mastoid process.

Physical Description

Skull

The holotype skull of Andrewsarchus mongoliensis (AMNH 20135), discovered in the Irdin Manha Formation of Inner Mongolia, represents the sole fossil specimen known for the genus and consists of an isolated upper cranium without the mandible. This specimen measures 83.4 cm in basal length from the premaxilla to the occipital condyles and 56 cm in maximum width across the zygomatic arches. The snout is markedly elongated, accounting for more than 50% of the total skull length, with the orbits positioned posteriorly and laterally, separated by the broad base of the rostrum. Structurally, the skull exhibits massive, flaring zygomatic arches that provide extensive attachment surfaces for the jaw adductor musculature, contributing to its overall robust appearance. The is reduced in height, and the temporal lines are weakly developed, indicating comparatively lower leverage and a potentially weaker bite force relative to the skull's size when compared to other large carnivorans. Large temporal fenestrae nonetheless suggest substantial space for muscle accommodation. The is notably broad and flat, differing from the narrower configuration in mesonychids but similar to that in basal , and the basicranium is short and elevated, with a small braincase. Osborn's initial description used these proportions to extrapolate overall body form, estimating a massive terrestrial predator akin to scaled-up mesonychids. The is preserved as a well-ossified but incomplete cranium, with no associated postcranial , limiting direct insights into body size but allowing for comparative analyses of cranial architecture. Recent studies have highlighted the skull's suitability for regression models estimating body mass in taxa known only from cranial material, underscoring its implications for understanding Eocene mammalian , though without detailed internal imaging like CT scans to further elucidate braincase volume relative to inferred body scale.

Dentition and Body Reconstruction

The dentition of Andrewsarchus mongoliensis follows the typical placental mammal of 44 teeth (3/3 , 1/1 canines, 4/4 premolars, 3/3 molars), exhibiting heterodonty adapted for a mix of piercing, shearing, and grinding functions. The upper form a semicircular arrangement, with the second incisor (i2) greatly enlarged and approaching the canine in size for enhanced gripping, while the third (i3) is considerably smaller. Canines are robust and pointed, though the uppers are not preserved in the ; premolars are generally single-cusped for shearing, with p1 featuring a simple cone, p2 a single cone on a bifanged root, p3 a double cone with a rudimentary third fang and prominent protocone but no deuterocone, and p4 enlarged and molariform with a tritocone and three fangs. Unlike carnassials in true carnivorans, these premolars lack specialized slicing adaptations. The molars are bunodont with wrinkled crowns, prominent proto- and tritocones, and rudimentary or worn deuterocones (e.g., on m2 and m3), indicating potential for crushing or grinding vegetation alongside meat. Body reconstructions of Andrewsarchus rely entirely on the isolated skull (AMNH 20135), as no postcranial elements are known, leading to significant uncertainty in overall form and proportions. Osborn's original reconstruction scaled the animal to mesonychid relatives like Mesonyx obtusidens, yielding estimates of 3.82 m total length (snout to pelvis) and 1.89 m shoulder height, implying a mass around 1,000 kg based on comparisons to large extant carnivores such as Ursus arctos. Subsequent revisions using allometric scaling from skull dimensions and entelodont relatives have lowered mass estimates to 600–900 kg, accounting for more conservative body builds and avoiding overextrapolation from the exceptionally large cranium. Recent phylogenetic analyses (as of 2023) place Andrewsarchus as a basal sister to a including Achaenodon and Erlianhyus, supporting inferences of a bulkier, entelodont-like structure. Debates on Andrewsarchus' body form contrast early depictions of a slender, long-legged ungulate-like predator with modern inferences of a bulkier, entelodont-like structure featuring robust limbs for scavenging rather than pursuit. Without postcrania, proportions are inferred from close relatives such as entelodonts (e.g., , with a comparably massive but documented bulky and shorter limbs), suggesting Andrewsarchus may have had a hippo-like massiveness rather than agility. These uncertainties stem from the single specimen, which risks size overestimation if atypical, and highlight the challenges in reconstructing a known solely from cranial material.

Paleobiology

Diet

The diet of Andrewsarchus has been inferred as omnivorous or scavenging rather than strictly hypercarnivorous, based on the of its and cranial features that parallel those of known omnivorous mammals. The enlarged, shearing premolars were adapted for tearing flesh, while the bunodont molars with wrinkled crowns facilitated grinding of plant material, , or other tough substances, indicating a versatile feeding strategy. Dental morphology and presumed wear patterns further support a mixed diet, with the lack of extreme specialization in the teeth suggesting consumption of both and vegetable matter, possibly including carrion as a primary protein source. Comparisons with entelodonts, which exhibit similar cranial and dental traits, point to opportunistic feeding behaviors, including scavenging and occasional predation on available resources. The jaw mechanics of Andrewsarchus, characterized by a reduced and flat mandibular fossa, indicate relatively weak bite force unsuitable for routine bone-crushing or overpowering large live prey, limiting it to softer or already compromised foods. This aligns with interpretations of entelodonts as non-apex predators capable of exploiting carcasses or juveniles of large herbivores, such as brontotheres, through tearing rather than crushing.

Habitat and Ecology

Fossils of Andrewsarchus have been recovered primarily from the Irdin Manha Formation in , , with additional material from the Lushi Formation in Province and the Dongjun Formation in Province, all dated to the Middle Eocene (approximately 47–38 million years ago). The paleoenvironment of these formations during the Middle Eocene featured a humid subtropical to , characterized by warm temperatures and abundant that supported diverse ecosystems including forests, rivers, and lakes. records from the Erlian Basin indicate a rich vegetation assemblage dominated by subtropical and temperate trees such as cycads, pines, and other arboreal taxa, reflecting a wet, forested landscape during the Eocene Climatic Optimum, though with emerging signs of seasonal variability by the Irdinmanhan stage. Andrewsarchus coexisted with a diverse assemblage in the Irdin Manha Formation, including brontotheres such as Metatitan, early perissodactyls like Forstercooperia, (e.g., ctenodactyloids and other small mammals), and (e.g., adapiforms), suggesting a competitive with varied herbivorous and omnivorous niches amid post-Cretaceous recovery. The rarity of Andrewsarchus fossils—known primarily from a single and isolated teeth—likely indicates either a low or limited preservation potential in this fluvial-lacustrine setting. Recent 2023 analyses correlate the Irdin Manha Formation with the Irdinmanhan stage and the underlying Arshanto Formation with the Arshantan stage, highlighting climate warming trends during the Middle Eocene that influenced vegetation shifts toward more open woodlands while maintaining overall humidity. In this context, Andrewsarchus probably occupied a mid-to-upper as an omnivore-scavenger, analogous to entelodonts, exploiting carrion and plant matter in a recovering .

References

  1. https://www.amnh.org/explore/news-blogs/andrewsarchus-prehistoric-mammal
  2. https://www.researchgate.net/publication/369722316_A_new_entelodont_Artiodactyla_Mammalia_from_the_late_Eocene_of_China_and_its_phylogenetic_implications
  3. https://digitallibrary.amnh.org/bitstreams/33d2e3c2-a69e-4e4b-a7a0-d459eb8fc1ec/download
  4. https://scienceblogs.com/tetrapodzoology/2009/08/13/mesonychians-part-iii-andrewsa
  5. https://digitallibrary.amnh.org/items/011b33cb-d709-457c-bd6b-064b42beb19e
  6. https://digitallibrary.amnh.org/items/e3701a9c-bf9b-434e-93d0-94ad405a4c83
  7. https://pmc.ncbi.nlm.nih.gov/articles/PMC8883515/
  8. https://www.pnas.org/doi/10.1073/pnas.251548698
  9. https://doi.org/10.1080/14772019.2023.2189436
  10. https://www.cambridge.org/core/journals/paleobiology/article/abs/functional-interpretation-of-the-masticatory-system-and-paleoecology-of-entelodonts/AA93EAF3364DE90DBE058577D6022C35
  11. https://www.cambridge.org/core/services/aop-cambridge-core/content/view/AA93EAF3364DE90DBE058577D6022C35/S0094837300010198a.pdf/functional_interpretation_of_the_masticatory_system_and_paleoecology_of_entelodonts.pdf
  12. https://digitallibrary.amnh.org/server/api/core/bitstreams/cfb9e495-c70f-4fd6-ad80-20dee7b880c3/content
  13. http://davidtwamley.com/wp-content/uploads/2023/06/Andrewsarchus-essay.pdf
  14. https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1171452/full
  15. https://bioone.org/journals/american-museum-novitates/volume-2018/issue-3914/3914.1/Biostratigraphy-and-Diversity-of-Paleogene-Perissodactyls-from-the-Erlian-Basin/10.1206/3914.1.full
  16. https://bioone.org/journals/acta-palaeontologica-polonica/volume-61/issue-4/app.00292.2016/Small-Mammal-Fauna-from-Wulanhuxiu-Nei-Mongol-China-Implies-the/10.4202/app.00292.2016.full
Add your contribution
Related Hubs
User Avatar
No comments yet.