Diprotodon
Diprotodon | |
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Diprotodon skeleton cast, MNHN, Paris | |
Illustration of a female Diprotodon with joey and sulphur-crested cockatoo | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Infraclass: | Marsupialia |
Order: | Diprotodontia |
Family: | †Diprotodontidae |
Genus: | †Diprotodon |
Type species | |
Diprotodon optatum Owen, 1838
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Synonyms[1] | |
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Diprotodon (
Diprotodon is the largest-known marsupial to have ever lived, it greatly exceeds the size of its closest living relatives
It is the only marsupial and metatherian that is known to have made seasonal migrations. Large herds, usually of females, seem to have marched through a wide range of habitats to find food and water, walking at around 6 km/h (3.7 mph). Diprotodon may have formed polygynous societies, possibly using its powerful incisors to fight for mates or fend off predators, such as the largest-known marsupial carnivore Thylacoleo carnifex. Being a marsupial, the mother may have raised her joey in a pouch on her belly, probably with one of these facing backwards, as in wombats.
Diprotodon went extinct about 40,000 years ago during the
Research history
In 1830, farmer George Ranken found a diverse fossil assemblage while exploring Wellington Caves, New South Wales, Australia.[2] This was the first major site of extinct Australian megafauna. Remains of Diprotodon were excavated when Ranken later returned as part of a formal expedition that was headed by explorer Major Thomas Mitchell.[3]
At the time these massive fossils were discovered, it was generally thought they were remains of rhinos, elephants, hippos, or dugongs. They fossils were not formally described until Mitchell took them in 1837 to his former colleague English naturalist Richard Owen while in England publishing his journal.[3] In 1838, while studying a piece of a right mandible with an incisor, Owen compared the tooth to those of wombats and hippos; he wrote to Mitchell designating it as a new genus Diprotodon. Mitchell published the correspondence in his journal.[4] Owen formally described Diprotodon in Volume 2 without mentioning a species; in Volume 1, however, he listed the name Diprotodon optatum, making that the type species.[5] Diprotodon means "two protruding front teeth" in Ancient Greek[3] and optatum is Latin for "desire" or "wish".[6] It was the first-ever Australian fossil mammal to be described.[a][3] In 1844, Owen replaced the name D. optatum with "D. australis".[8] Owen only once used the name optatum and the acceptance of its apparent replacement "australis" has historically varied widely[5] but optatum is now standard.[1]
In 1843, Mitchell was sent more Diprotodon fossils from the recently settled Darling Downs and relayed them to Owen. Owen, having interpreted the incisors as tusks, as well as comparing the flattening (anteroposterior compression) of the femur to the condition in elephants and rhinos, and the raised ridges of the molar to the grinding surfaces of elephant teeth, believed Diprotodon was an elephant related to or synonymous with Mastodon or Deinotherium. Later that year, he formally synonymised Diprotodon with Deinotherium as Dinotherium Australe,[9] which he recanted in 1844 after German naturalist Ludwig Leichhardt pointed out that the incisors clearly belong to a marsupial.[10] Owen still classified the molars from Wellington as Mastodon australis and continued to describe Diprotodon as likely elephantine.[8] In 1847, a nearly complete skull and skeleton was recovered from the Darling Downs, the latter confirming this characterisation.[10] The massive skeleton attracted a large audience while on public display in Sydney.[b] Leichhardt believed the animal was aquatic and in 1844, he said it might still be alive in an undiscovered tropical area nearer the interior but as the European land exploration of Australia progressed, he became certain it was extinct.[11] Owen later become the foremost authority of Australian palaeontology of his time, mostly working with marsupials.[7]
Huge assemblages of mostly complete Diprotodon fossils have been unearthed in dry lakes and riverbeds;[1] the largest assemblage came from Lake Callabonna, South Australia.[12] Fossils were first noticed here by an aboriginal stockman working on a sheep property to the east. The owners, the Ragless brothers, notified the South Australian Museum, which hired Australian geologist Henry Hurst, who reported an enormous wealth of fossil material and was paid £250 in 1893 to excavate the site. Hurst found up to 360 Diprotodon individuals over a few acres; excavation was restarted in the 1970s and more were uncovered. American palaeontologist Richard H. Tedford said multiple herds of these animals had at different times become stuck in mud while crossing bodies of water while water levels were low during dry seasons.[13]
In addition to D. optatum, several other species were erected in the 19th century, often from single specimens, on the basis of subtle anatomical variations.[1] Among the variations was size difference: adult Diprotodon specimens have two distinct size ranges. In their 1975 review of Australian fossil mammals, Australian palaeontologists J. A. Mahoney and William David Lindsay Ride did not ascribe this to sexual dimorphism because males and females of modern wombat and koala species—its closest living relatives—are skeletally indistinguishable,[c] so they assumed the same would have been true for extinct relatives, including Diprotodon.[16] These other species are:
- D. annextans was erected in 1861 by Irish palaeontologist Frederick McCoy based on some teeth and a partial mandible found near Colac, Victoria; the name may be a typo of annectens, which means linking or joining, because he characterised the species as combining traits from Diprotodon and Nototherium;[17]
- D. minorwas erected in 1862 by
- D. longiceps was erected in 1865 by McCoy as a replacement for "D. annextans";[20]
- D. bennettii was erected in 1873 by German naturalist Gerard Krefft based on a nearly complete mandible collected by naturalists George Bennet and Georgina King near Gowrie, New South Wales;[21] and
- D. loderi was erected in 1873 by Krefft based on a partial palate collected by Andrew Loder near Murrurundi, New South Wales.[20]
In 2008, Australian palaeontologist Gilbert Price opted to recognise only one species D. optatum based most-notably on a lack of dental differences among these supposed species, and said it was likely Diprotodon was indeed sexually dimorphic, with the male probably being the larger form.[1]
Classification
Phylogeny
Diprotodon is a marsupial in the
In 1872, American mammalogist
Below is the Diprotodontoidea family tree according to Australian palaeontologists Karen H. Black and Brian Mackness, 1999 (top),[29] and Vombatiformes family tree according to Beck et al. 2020 (bottom):[24]
Diprotodontoidea
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Vombatiformes |
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Evolution
Diprotodontidae is the most diverse family in Vombatomorphia; it was better adapted to the spreading dry, open landscapes over the last tens of millions of years than other groups in the infraorder, living or extinct.[31] Diprotodon has been found in every Australian state, making it the most-widespread Australian megafauna in the fossil record.[e][33] The oldest vombatomorph (and vombatiform) is Mukupirna, which was identified in 2020 from Oligocene deposits of the South Australian Namba Formation dating to 26–25 million years ago. The group probably evolved much earlier; Mukupirna was already differentiated as a closer relative to wombats than other vombatiformes, and attained a massive size of roughly 150 kg (330 lb), whereas the last common ancestor of vombatiformes was probably a small, 1–5.5 kg (2.2–12.1 lb) creature.[24]
Both diprotodontines and zygomaturines were both apparently quite diverse over the
In general, there is poor resolution on the ages of Australian fossil sites. While the
Description
Skull
Diprotodon has a long, narrow skull.
The
A sagittal crest extends across the midline of the skull from the supraoccipital—the top of the occipital bone—to the region between the eyes on the top of the head. The orbit (eye socket) is small and vertically oval-shaped. The nasal bones slightly curve upwards until near their endpoint, where they begin to curve down, giving the bones a somewhat S-shaped profile. Like many marsupials, most of the nasal septum is made of bone rather than cartilage. The nose would have been quite mobile. The height of the skull from the peak of the occipital bone to the end of the nasals is strikingly almost uniform; the end of the nasals is the tallest point. The zygomatic arch (cheek bone) is strong and deep as in kangaroos but unlike those of koalas and wombats, and extends all the way from the supraoccipital.[40]
Jaws
As in kangaroos and wombats, there is a gap between the jointing of the
As in other marsupials, the
Teeth
The
The incisors are scalpriform (chisel-like). Like those of wombats and rodents, the first incisors in both jaws continuously grew throughout the animal's life but the other two upper incisors did not. This combination is not seen in any living marsupial. The cross-section of the upper incisors is circular. In one old male specimen, the first upper incisor measures 280 mm (11 in) of which 220 mm (8.5 in) is within the tooth socket; the second is 100 mm (4 in) and 25 mm (1 in) is in the socket; and the exposed part of the third is 66 mm (2.6 in). The first incisor is convex and curves outwards but the other two are concave.[45] The lower incisor has a faint upward curve but is otherwise straight and has an oval cross-section. In the same old male specimen, the lower incisor measures 250 mm (10 in), of which 2⁄3 is inside the socket.[46]
The premolars and molars are
Vertebrae
Diprotodon had five cervical (neck) vertebrae. The atlas, the first cervical (C1), has a pair of deep cavities for insertion of the occipital condyles. The diaphophyses of the atlas, an upward-angled projection on either the side of the vertebra, are relatively short and thick, and resemble those of wombats and koalas. The articular surface of the axis (C2), the part that joints to another vertebra, is slightly concave on the front side and flat on the back side. As in kangaroos, the axis has a low subtriangular hypophysis projecting vertically from the underside of the vertebra and a proportionally long odontoid—a projection from the axis which fits into the atlas—but the neural spine, which projects vertically the topside of the vertebra, is more forwards. The remaining cervicals lack a hypophysis. As in kangaroos, C3 and C4 have a shorter and more-compressed neural spine, which is supported by a low ridge along its midline in the front and the back. The neural spine of C5 is narrower but thicker, and is supported by stronger-but-shorter ridges.[49]
Diprotodon probably had 13
Like most marsupials, Diprotodon likely had six lumbar vertebrae.[g] They retain a proportionally tall neural arch but not the diapophyses, though L1 can retain a small protuberance on one side where a diapophysis would be in a dorsal vertebra; this has been documented in kangaroos and other mammals. The length of each vertebra increases along the series so the lumbar series may have bent downward.[53]
Like other marsupials, Diprotodon had two
Limbs
Girdles
The general proportions of the
Unlike other marsupials, the
Long bones
Unlike those of most marsupials, the humerus of Diprotodon is almost straight rather than S-shaped, and the trochlea of the humerus at the elbow joint is not perforated. The ridges for muscle attachments are poorly developed, which seems to have been compensated for by the powerful forearms. Similarly, the condyles where the radius and ulna (the forearm bones) connect maintain their rounded shape and are quite-similarly sized, and unusually reminiscent of the condyles between the femur and the tibia and fibula in the leg of a kangaroo.[57]
Like elephants, the femur of Diprotodon is straight and compressed anteroposteriorly (from headside to tailside). The walls of the femur are prodigiously thickened, strongly constricting the medullary cavity where the bone marrow is located. The proximal end (part closest to the hip joint) is notably long, broad, and deep. The femoral head projects up far from the greater trochanter. As in kangaroos, the greater trochanter is split into two lobes. The femoral neck is roughly the same diameter as the femoral head. Also as in kangaroos, the condyle for the fibula is excavated out but the condyle for the tibia is well-rounded and hemispherical. Like those of many other marsupials, the tibia is twisted and the tibial malleolus (on the ankle) is reduced.[58]
Paws
Diprotodon has five digits on either paw. Like other plantigrade walkers, where the paws were flat on the ground, the wrist and ankle would have been largely rigid and inflexible.[59][60] The digits are proportionally weak so the paws probably had a lot of padding.[35] Similarly, the digits do not seem to have been much engaged in weight bearing.[60][61]
The forepaw was strong and the shape of the wrist bones is quite similar to those of kangaroos. Like other vombatiformes, the
The digits of the hindpaws turn inwards from the ankle at 130 degrees. The
Size
Diprotodon is the largest-known marsupial to ever have lived.[30] In life, adult Diprotodon could have reached 160–180 cm (5 ft 3 in – 5 ft 11 in) at the shoulders and 275–340 cm (9–11 ft) from head to tail.[63] Accounting for cartilaginous intervertebral discs, Diprotodon may have been 20% longer than reconstructed skeletons, exceeding 400 cm (13 ft 1 in).[64]
As researchers were formulating predictive body-mass equations for fossil species, efforts were largely constrained to
In 2003, Australian palaeontologist Stephen Wroe and colleagues took a more-sophisticated approach to body mass than Murray's estimate. They made a regression between the minimum circumference of the femora and humeri of 18 quadrupedal marsupials and 32 placentals against body mass, and then inputted 17 Diprotodon long bones into their predictive model. The results ranged from 2,272–3,417 kg (5,009–7,533 lb), for a mean of 2,786 kg (6,142 lb), though Wroe said reconstructing the weight of extinct creatures that far outweighed living counterparts[h] is problematic. For comparison, an American bison they used in their study weighed 1,179 kg (2,599 lb) and a hippo weighed 1,950 kg (4,300 lb).[64]
Paleobiology
Diet
Like modern megaherbivores, most evidently the
The molars of Diprotodon are a simple bilophodont shape. Kangaroos use their bilophodont teeth to grind tender, low-fibre plants as a browser as well as grass as a grazer. Kangaroos that predominantly graze have specialised molars to resist the abrasiveness of grass but such adaptations are not exhibited in Diprotodon, which may have had a mixed diet similar to that of a browsing wallaby. It may also have chewed like wallabies, beginning with a vertical crunch before grinding transversely, as opposed to wombats, which only grind transversely. Similarly to many large ungulates (hoofed mammals), the jaws of Diprotodon were better suited for crushing rather than grinding, which would have permitted it to process vegetation in bulk.[42]
In 2016, Australian biologists Alana Sharpe and Thomas Rich estimated the maximum-possible
Migration and sociality
In 2017, by measuring the strontium isotope ratio (87Sr/86Sr) at various points along the Diprotodon incisor QMF3452 from the Darling Downs, and matching those ratios to the ratios of sites across that region, Price and colleagues determined Diprotodon made seasonal migrations, probably in search of food or watering holes. This individual appears to have been following the Condamine River and, while apparently keeping to the Darling Downs during the three years this tooth had been growing, it would have been annually making a 200 km (120 mi) northwest-southeast round trip. This trek parallels the mammalian mass migrations of modern-day East Africa.[72]
Diprotodon is the only identified
Diprotodon apparently moved in large herds. Possible fossilised herds, which are most-commonly unearthed in south-eastern Australia, seem to be mostly or entirely female, and sometimes travelled with juveniles. Such sexual segregation is normally seen in polygynous species; it is a common social organisation among modern megaherbivores involving an entirely female herd save for their young and the dominant male, with which the herd exclusinvely breeds.[1] Similarly, the skull is adapted to handling much-higher stresses than that which resulted from bite alone so Diprotodon may have subjected its teeth or jaws to more-strenuous activities than chewing, such as fighting other Diprotodon for mates or fending off predators, using the incisors.[38] Like modern red and grey kangaroos, which also sexually segregate, bachelor herds of Diprotodon seem to have been less tolerant to drought conditions than female herds due to their larger size and nutritional requirements.[1]
Gait
The locomotion of an extinct animal can be inferred using
At Lake Callabonna, the single Diprotodon responsible for the impressions had an average stride length of 1,500 mm (4 ft 11 in), trackway width of 430 mm (1 ft 5 in), and track dimensions 295 mm × 202 mm (11.6 in × 8.0 in) in length x width. The gleno-acetabular length—the distance between the shoulders and pelvis—could have been about 1,125 mm (3 ft 8 in); assuming a hip height of 900 mm (2 ft 11 in), the maker of these tracks was probably moving at around 6.3 km/h (3.9 mph).[73]
The single Diprotodon responsible for the impressions at the volcanic plain had an average stride length of 1,310 mm (4 ft 4 in), trackway width of 660 mm (2 ft 2 in), and pes length of 450 mm (1 ft 6 in). The gleno-acetabular length may have been about 1,080 mm (3 ft 7 in) and assuming a hip height of 830 mm (2 ft 9 in), the maker of the tracks was probably moving at around 5.5 km/h (3.4 mph). Its posture was much-more-sprawled than the example from Callabonna, aligning more with what might be expected of Zygomaturus. The animal may have been a female carrying a large joey in her pouch, the added weight on the stomach altering the gait. The first trackway continues for 62.8 m (206 ft) in a south-easterly direction towards a palaeo-lake. The animal seems to have hesitated while stepping down from the first
Life history
The marsupial
Based on the relationship between female body size and life history in kangaroos, a 1,000 kg (2,200 lb) Diprotodon female would have gestated for six-to-eight weeks, and given birth to a single 5 g (0.18 oz) joey. Given its massive size, Diprotodon may not have sat down to give birth as do smaller marsupials, possibly standing instead. Like koalas and wombats, the pouch may have faced backwards so the joey could crawl down across its mother's abdomen to enter and attach itself to a teat until it could see—perhaps 260 days—and
In large kangaroos, females usually reach sexual maturity and enter oestrus soon after weaning, and males need double the time to reach sexual maturity. A similar pattern could have been exhibited in Diprotodon. Assuming a lifespan of up to 50 years, a female Diprotodon could have given birth eight times.[76]
Palaeoecology
Diprotodon was present across the entire Australian continent by the Late Pleistocene,
The continent-wide distribution of Diprotodon indicates herds trekked across almost any habitat, much like modern African elephants south of the Sahara.[1] Diprotodon was a member of a diverse assemblage of megafauna that were endemic to Pleistocene Australia; these also included the thylacine, modern kangaroos, sthenurines (giant short-faced kangaroos), a diversity of modern and giant koala and wombat species,[34] the tapir-like Palorchestes, the giant turtle Meiolania, and the giant bird Genyornis.[77] Diprotodon coexisted with the diprotodontid Zygomaturus trilobus, which appears to have remained in the forests, whereas Diprotodon foraged the expanding grasslands and woodlands. Other contemporaneous dipotodontids (Hulitherium, Z. nimborensia, and Maokopia) were insular forms that were restricted to the forests of New Guinea.[34]
Predation
Due to its massive size, Diprotodon would have been a tough adversary for native carnivores. It contended with the largest-known marsupial predator
The largest predators of Australia were reptiles, most notably the saltwater crocodile, the now-extinct crocodiles Paludirex and Quinkana, and the giant lizard megalania (Varanus priscus). At 7 m (23 ft) in length, megalania was the largest carnivore of Pleistocene Australia.[77]
Extinction
As part of the
At the time Roberts et al. published their paper, the earliest evidence of human activity in Australia was 56±4 thousand years old, which is close to their calculated date for the megafauna extinction; they hypothesised human hunting had eradicated the last megafauna within about 10,000 years of coexistence. Human hunting had earlier been blamed for the extinction of North American and
In 2005, American geologist Gifford Miller noticed fire abruptly becomes more common about 45,000 years ago; he ascribed this increase to aboriginal fire-stick farmers, who would have regularly started controlled burns to clear highly productive forests and grasslands. Miller said this radically altered the vegetational landscape and promulgated the expanse of the modern-day fire-resilient scrub at the expense of the megafauna.[84][85] Subsequent studies had difficulty firmly linking controlled burns with major ecological collapse.[82][86][87] The frequency of fire could have also increased as a consequence of megafaunal extinction because total plant consumption rapidly fell, leading to faster fuel buildup.[88]
In 2017, the human-occupied Madjedbebe rock shelter on the northern Australian coast was dated to about 65,000 years ago, which if correct would mean humans and megafauna had coexisted for over 20,000 years.[89] Other authors have considered this dating questionable.[90] In the 2010s, several ecological studies were published in support of major drought conditions coinciding with the final megafaunal extinctions.[91][92][93][94][95] Their demise may have been the result of a combination of climatic change, human hunting, and human-driven landscape changes.[80]
Cultural significance
Fossil evidence
Despite the role the first Aboriginal Australians are speculated to have had in the extinction of Diprotodon and other mammalian megafauna in Australia, there is little evidence humans used them at all in the 20,000 years of coexistence. No fossils of mammalian megafauna suggestive of human butchery or cooking have been found.[k][97]
In 1984, Gail Paton discovered an upper-right Diprotodon incisor (2I) bearing 28 visible cut marks in Spring Creek, south-western Victoria; Ron Vanderwald and Richard Fullager studied the incisor, which was split in half longitudinally, seemingly while the bone was still fresh but it was glued together before Vanderwald and Fullager could inspect it. Each piece measures 40 cm (16 in) in length. The marks are aligned in a straight line, and measure 0.91–4.1 mm (0.036–0.161 in) in length, 0.14–0.8 mm (0.0055–0.0315 in) in width, and 0.02–0.24 mm (0.00079–0.00945 in) in depth. They determined it was inconsistent with bite marks from scavenging Thylacoleo or mice, and concluded it was incised by humans with flint as a counting system or a random doodle.[98] This specimen became one of the most-cited pieces of evidence humans and megafauna directly interacted until a 2020 re-analysis by Australian palaeoanthropologist Michelle Langley identified the engraver as most-likely a tiger quoll.[97]
In 2016, Australian archaeologist Giles Hamm and colleagues unearthed a partial right radius belonging to a young Diprotodon in the Warratyi rock shelter. Because it lacks carnivore damage and the rock shelter is up a sheer face Diprotodon is unlikely to have climbed, they said humans were responsible for taking the bone to the site.[99]
Mythology
When the first massive fossils in Australia were dug up, it was not clear what animals they might have represented because there were no serious scientists on the continent. Local residents guessed some may have been the remains of rhinos or elephants. European settlers, the most-vocal of whom was Reverend John Dunmore Lang, forwarded these fossils as evidence of the Genesis flood narrative. Aboriginal Australians also attempted to fit the finds into their own religious ideas, quickly associating Diprotodon with the bunyip, a large, carnivorous, lake monster. Many ethnologists and palaeontologists of the time believed the bunyip to be a tribal memory of the lumbering giant creature that probably frequented marshlands, though at the time it was uncertain whether Diprotodon and other megafauna were still extant because the Australian continent had not yet been fully explored by Europeans. Scientific investigation into the bunyip was stigmatised after a purported bunyip skull was sensationalised in 1846, and was put on display at the Australian Museum. The following year, however, Owen recognised it as the skull of a foal, and was surprised the burgeoning Australian scientific community could have erred so egregiously.[3]
In 1892, Canadian geologist Henry Yorke Lyell Brown reported Aboriginal Australians identified Diprotodon fossils from Lake Eyre as those of the Rainbow Serpent, which he thought was a giant, bottom-dwelling fish. This notion became somewhat popularised after English geologist John Walter Gregory, who believed the god was a horned, scaly creature, conjectured it was a chimaera of Diprotodon—which he believed had a horn—and a crocodile. Later workers continued to report some link between the Rainbow Serpent and either Diprotodon or crocodiles.[100]
These kinds of suppositions are not testable and require stories to survive in oral tradition for tens of thousands of years.[100] If Pleistocene megafauna are the basis of some aboriginal mythology, it is unclear if the stories were based on the creatures when they were alive or their fossils being discovered long after their extinction.[101]
Rock art representations
Aboriginal Australians decorated caves with paintings and drawings of several creatures but the identities of the subjects are often unclear. In 1907, Australian anthropologist
See also
Notes
- ^ Owen, and other naturalists of the time would use Diprotodon, and the other unusual extinct creatures of Wellington Cave and the Australian continent to deconstruct progressive creationist arguments that claimed God created certain forms to exist in certain environments and time periods, based on the fossils of modern animals such as hyenas and rhinos, which are found only in Africa but were being unearthed in every other continent. This was confounded by Diprotodon and more of Owen's taxa because they were found nowhere else, and more-typical animals were not found in Australia either, despite the Australian climate's similarity to that of Africa. Owen disagreed with Charles Darwin's theory of natural selection.[7]
- ^ The specimen was collected by R. B. Turner at Kings Creek, Queensland, and was taken to Sydney in 1847 to be sold at auction. Leichhardt attempted to buy it for the new Australian Museum but Scottish entrepreneur Benjamin Boyd outbuid him at £50. After being examined by Leichhardt, English geologist Reverend William Branwhite Clarke, and curator William Sheridan Wall, it was shipped to England but the ship was wrecked off the Sussex coast. Only the skull was saved; it was taken to Owen.[10]
- ^ Because joeys develop mostly outside the mother's womb, female marsupials do not require the adaptations to the skeleton placentals need to survive gestation and childbirth, equating to few or no skeletal differences between males and females.[1] In modern wombats, the female can be slightly but insignificantly larger than the male.[14] In koalas, males can be 50% larger than females.[15]
- ^ In 1868, Owen classified all marsupials (living or extinct) into either the orders Polyprotodontia (characterised by multiple pairs of mandibular incisors) or Diprotodontia (a single pair of mandibular incisors). The name Diprotodontia does not derive from Diprotodon.[22] Marsupialia is divided into several orders, of which Diprotodontia is the largest.[23]
- ^ This does not necessarily indicate its dominance among Australian megafauna because the bones of Diprotodon are enormous and incredibly robust, and are thus far more likely to fossilise and be discovered than those of other megafauna.[32]
- ^ They were unsure if it was appropriate to classify the Nelson Bay material into a new species based on the size and temporal difference, so they tentatively designated them as D. ?optatum.[30]
- ^ Wombats have four lumbar vertebrae and koalas have five.[52]
- ^ A bull red kangaroo, the largest living marsupial, can weigh 22–85 kg (49–187 lb).[67]
- Finite element analysis considers the skull's section modulus—an object's ability to resist bending—but the material properties of marsupial skulls are not well studied. Sharpe and Rich used what they considered a typical Young's modulus and Poisson's ratio for a mammalian skull—respectively 20 GPa (2,900,000 psi) and 0.3—and unsafely assumed these properties were uniform across the entire skull. This likely would have made their model skull stiffer than the real thing.[38]
- ^ Metatheria includes marsupials and all therian mammals more closely related to marsupials than placentals.
- ^ The only potential direct evidence of human and mammalian megafauna interaction (that has not yet been revised) is a tibial fragment with a single notch belonging to either Sthenurus or Protemnodon (short faced kangaroos), identified in 1980 by Australian zoologist Michael Archer and colleagues in Mammoth Cave, Western Australia.[96]
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External links
- "Megafauna". Australian Museum.
- "3D model of the skull of Diprotodon". phenome10k.org.
Further reading
- Clode, D. (2009). Prehistoric Giants: The megafauna of Australia. Museum Victoria. ISBN 978-0-9803813-2-0.
- Mahoney, J. A.; Ride, W. D. L. (1975). "Index to the genera and species described from Australia and New Guinea from 1838 to 1968" (PDF). Western Australian Museum Special Publication (6): 87. Archived (PDF) from the original on 10 September 2014.
- Owen, R. (1870). Restoration of an extinct elephantine marsupial (Diprotodon australis). Taylor and Francis.
- Vickers-Rich, P.; Monaghan, J. M.; Baird, R. F.; Rich, T. H., eds. (1991). Vertebrate palaeontology of Australasia. Pioneer Design Studio in cooperation with the Monash University Publications Committee. ISBN 9780909674366.