Megalania

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Megalania
Temporal range: Pleistocene, 1.5–0.05  Ma
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Varanus priscus Melbourne Museum.jpg
Megalania skeletal reconstruction on Melbourne Museum steps
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Varanidae
Genus: Varanus
Species:
†V. priscus
Binomial name
†Varanus priscus
Owen, 1859 [1]
Synonyms
  • Megalania prisca(Owen, 1859)
  • Notiosaurus dentatusOwen, 1884
  • Varanus dirusde Vis, 1889
  • Varanus warburtonensisZeitz, 1899

Megalania (Varanus priscus) is an extinct species of giant monitor lizard, [1] part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, reaching an estimated length of 3.5 to 7 metres (11.5 – 23 ft), and weighing between 97–1,940 kg (214–4,277 lb), but the fragmentary nature of known remains make estimates highly uncertain.

Megalania is thought to have had a similar ecology to the living Komodo dragon (Varanus komodoensis). The youngest fossil remains of giant monitor lizards in Australia date to around 50,000 years ago. [2] The first indigenous settlers of Australia might have encountered megalania, [3] and been a factor in megalania's extinction. [4] [2] [5] While originally megalania was considered to be the only member of the titular genus "Megalania", today it is considered a member of the genus Varanus, being closely related to other Australian monitor lizards.

Taxonomy

Illustration of the original dorsal and cervical vertebrae, 1859 Megalania.jpg
Illustration of the original dorsal and cervical vertebrae, 1859

Sir Richard Owen described the first known remains of megalania in 1859, from three vertebrae amongst a collection of primarily marsupial bones purchased by the British Museum, collected from the bed of a tributary of the Condamine River, west of Moreton Bay in eastern Australia. The name "Megalania prisca" was coined in the paper by Owen to mean "ancient great roamer"; the name was chosen "in reference to the terrestrial nature of the great Saurian". [1] Owen used a modification of the Greek word ἠλαίνω ēlainō ("I roam"). The close similarity to the Latin word: lania (feminine form of "butcher") has resulted in numerous taxonomic and popular descriptions of "Megalania" mistranslating the name as "ancient giant butcher." "Megalania" is no longer considered a valid genus, with many authors preferring to consider it a junior synonym of Varanus , [6] [7] which encompasses all living monitor lizards. As the genera "Megalania" and Varanus are respectively feminine and masculine in gender, the specific names agree: prisca (feminine) and priscus (masculine). [8]

Megalania is included within Varanus because its morphology suggests that it is more closely related to some species of Varanus than others, so excluding V. priscus from Varanus renders the latter genus an unnatural grouping. Ralph Molnar noted in 2004 that, even if every species of the genus Varanus were divided into groups currently designated as subgenera, V. priscus would still be classified in the genus Varanus, because this is the current subgenus name, as well as genus name, for all Australian monitors. Unless other Australian monitor species were each also classified their own exclusive genera, "Megalania" would not be a valid genus name. However, Molnar noted that "megalania" is suitable for use as a vernacular, rather than scientific name, for the species Varanus priscus. [8]

Phylogeny

ZOJ 448 f5.gif

Several studies have attempted to establish the phylogenetic position of megalania within the Varanidae. An affinity with the perentie (Varanus giganteus), Australia's largest living lizard, has been suggested based on skull-roof morphology. [10] The most recent comprehensive study [9] proposes a sister-taxon relationship with the large Komodo dragon (Varanus komodoensis) based on neurocranial similarities, with the lace monitor (Varanus varius) as the closest living Australian relative. Conversely, the perentie is considered more closely related to Gould's monitor and the Argus monitor.

Size

Two size estimations of megalania compared to extant monitor lizards and a human Extant Monitor lizards-Megalania SIZE.png
Two size estimations of megalania compared to extant monitor lizards and a human

The lack of complete or nearly complete fossil skeletons has made it difficult to determine the exact dimensions of megalania. [7] Early estimates placed the length of the largest individuals at 7 m (23 ft), with a maximum weight of approximately 600–620 kg (1,320–1,370 lb). [11] In 2002, Stephen Wroe considerably downsized megalania, suggesting a maximum length of 4.5 m (15 ft) and a weight of 331 kg (730 lb) with averages of 3.5 m (11 ft) and 97–158 kg (214–348 lb), [12] decrying the earlier maximum length estimate of 7 m (23 ft) as exaggerations based on flawed methods. In 2009, however Wroe joined other researchers in raising the estimate to at least 5.5 m (18 ft) and 575 kg (1,268 lb). [13]

In a book published in 2004, Ralph Molnar determined a range of potential sizes for megalania, made by scaling up from dorsal vertebrae, after he determined a relationship between dorsal vertebrae width and total body length. If it had a long, thin tail like the lace monitor, then it would have reached a length of 7.9 m (26 ft), while if its tail-to-body proportions were more similar to that of the Komodo dragon, then a length around 7 m (23 ft) is more likely. Taking the maximal 7 m (23 ft) length, he estimated a weight of 1,940 kg (4,280 lb), with a leaner 320 kg (710 lb) being average. [7]

Palaeobiology

Life restoration Varanus priscus.png
Life restoration

Megalania is the largest terrestrial lizard known to have existed. Judging from its size, it would have fed mostly upon medium- to large-sized animals, including any of the giant marsupials such as Diprotodon , along with other reptiles and small mammals, as well as birds and their eggs and chicks.[ citation needed ] It had heavily built limbs and body, a large skull complete with a small crest between the eyes, and a jaw full of serrated, blade-like teeth. [8]

Some scientists regard with skepticism the contention that megalania was the only, or even principal, predator of the Australian Pleistocene megafauna. [14] They note that the marsupial lion (Thylacoleo carnifex) has been implicated with the butchery of very large Pleistocene mammals, while megalania has not.[ citation needed ] In addition, they note that megalania fossils are extremely uncommon, in contrast to T. carnifex's wide distribution across Australian Pleistocene deposits. Quinkana , a genus of terrestrial crocodiles that grew up to 6 m and was present until around 40,000 years ago, has also been marked as another apex predator of Australian megafauna.

Komodo dragons, megalania's closest relative, are known to have evolved in Australia before spreading to their current range in Indonesia, as fossil evidence from Queensland has implied. [15] [16] If one were to reconstruct the ecosystems that existed before the arrival of the humans on Australia, reintroducing Komodo dragons as an ecological proxy of megalania to the continent has been suggested. [17]

A study published in 2009 using Wroe's earlier size estimates and an analysis of 18 closely related lizard species estimated a sprinting speed of 2.6–3 m/s (9.4–10.8 km/h). This speed is comparable to that of the extant freshwater crocodile (Crocodylus johnstoni). [18]

The scales of megalania would possibly be similar to those of their extant relatives, possessing a honeycomb microstructure and both durable and resilient to water evaporation. [19]

Venom

Hypothetical megalania skull, at the Museum of Science, Boston Varanus priscus skull.jpg
Hypothetical megalania skull, at the Museum of Science, Boston

Along with other varanid lizards, such as the Komodo dragon and the Nile monitor, megalania belongs to the proposed clade Toxicofera, which contains all known reptile clades possessing toxin-secreting oral glands, as well as their close venomous and nonvenomous relatives, including Iguania, Anguimorpha, and snakes. [20] [21] [22] Closely related varanids use a potent venom found in glands inside the jaw. The venom in these lizards have been shown to be a haemotoxin. The venom would act as an anticoagulant and would greatly increase the bleeding the prey received from its wounds. This would rapidly decrease the prey's blood pressure and lead to systemic shock. Being a member of Anguimorpha, megalania may have been venomous and if so, would be the largest venomous vertebrate known. [13]

Extinction

The youngest remains of the species date to the Late Pleistocene, with the youngest remains possibly referrable to the species being a large osteoderm dating to approximately 50,000 years ago from the Mount Etna Caves National Park in central-eastern Queensland. [2] A study examined the morphology of nine closely related extant varanid lizards and then allometrically scaled and compared them to V. priscus, found that the musculature of the limbs, posture, muscular mass, and possible muscular composition of the animal would most likely have been inefficient when attempting to outrun the early human settlers who colonised Australia during that time. [4] Considering many other species of Australian megafauna went extinct around the same time, either due to human predation or being outcompeted by them, the same can be assumed for megalania.

Confrontations between megalania and early Aboriginal Australians may have inspired tales of fearsome creatures such as the whowie. [7]

Related Research Articles

<span class="mw-page-title-main">Komodo dragon</span> Largest living species of lizard

The Komodo dragon, also known as the Komodo monitor, is a member of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo, Rinca, Flores, and Gili Motang. It is the largest extant species of lizard, growing to a maximum length of 3 m (9.8 ft), and weighing up to 70 kg (150 lb).

<span class="mw-page-title-main">Varanidae</span> Family of lizards

The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). Varanus includes the Komodo dragon, crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the earless monitor lizard and Chinese crocodile lizard. The oldest members of the family are known from the Late Cretaceous of Mongolia.

<span class="mw-page-title-main">Monitor lizard</span> Genus of reptiles

Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recognized.

<span class="mw-page-title-main">Australian megafauna</span> Large animals in Australia, past and present era

The term Australian megafauna refers to the megafauna in Australia during the Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, and the roles of human and climatic factors in their extinction are contested.

<span class="mw-page-title-main">Perentie</span> Species of lizard

The perentie is a species of monitor lizard. It is one of the largest living lizards on earth, after the Komodo dragon, Asian water monitor, and the Crocodile monitor. Found west of the Great Dividing Range in the arid areas of Australia, it is rarely seen, because of its shyness and the remoteness of much of its range from human habitation. The species is considered to be a least-concern species according to the International Union for Conservation of Nature.

<span class="mw-page-title-main">Desert monitor</span> Species of lizard

The desert monitor is a species of monitor lizard of the order Squamata found living throughout North Africa and Central and South Asia. The desert monitor is carnivorous, feeding on a wide range of vertebrates and invertebrates.

<span class="mw-page-title-main">Asian water monitor</span> Species of lizard

The Asian water monitor is a large varanid lizard native to South and Southeast Asia. It is one of the most common monitor lizards in Asia, ranging from coastal northeast India, Bangladesh, Sri Lanka, mainland Southeast Asia, and southern China to Indonesian islands where it lives close to water. It is listed as Least Concern on the IUCN Red List. It was described by Laurenti in 1768 and is among the largest squamates in the world.

<span class="mw-page-title-main">Lace monitor</span> Species of lizard

The lace monitor, also known as the tree goanna, is a member of the monitor lizard family native to eastern Australia. A large lizard, it can reach 2 metres (6.6 ft) in total length and 14 kilograms (31 lb) in weight. The lace monitor is considered to be a least-concern species according to the International Union for Conservation of Nature.

<span class="mw-page-title-main">Sand goanna</span> Species of lizard

The sand goanna, also known commonly as Gould's monitor, the racehorse goanna, and the sand monitor, is a species of large Australian monitor lizard in the family Varanidae.

<i>Varanus salvadorii</i> Species of lizard

The crocodile monitor, also known as the Papuan monitor or Salvadori's monitor, is a species of monitor lizard endemic to New Guinea. It is the largest monitor lizard in New Guinea and is one of the longest lizards, verified at up to 255 cm (100 in). Its tail is exceptionally long, with some specimens having been claimed to exceed the length of the Komodo dragon, however less massive.

<span class="mw-page-title-main">Persistence hunting</span> Hunting until the prey animal can no longer flee

Persistence hunting, also known as endurance hunting or long-distance hunting is a variant of pursuit predation in which a predator will bring down a prey item via indirect means, such as exhaustion, heat illness or injury. Hunters of this type will typically display adaptions for distance running, such as longer legs, temperature regulation, and specialized cardiovascular systems.

<i>Quinkana</i> Extinct genus of reptiles

Quinkana is an extinct genus of mekosuchine crocodylians that lived in Australia from about 28 million to about 10,000 years ago. Most attributed specimens have been found in Queensland. It is speculated to have been one of the top predators of Pleistocene Australia.

<i>Ninjemys</i> Extinct genus of turtle

Ninjemys oweni is an extinct large meiolaniid stem-turtle from Pleistocene Queensland and possibly New South Wales (Australia). It overall resembled its relative, Meiolania, save that the largest pair of horns on its head stuck out to the sides, rather than point backwards, the larger scales at the back of its skull and the tail club which is made up of only two tail rings rather than four. With a shell length of approximately 1 m it is a large turtle and among the largest meiolaniids. Ninjemys is primarily known from a well preserved skull and associated tail armor, which were initially thought to have belonged to the giant monitor lizard Megalania.

<span class="mw-page-title-main">Varanoidea</span> Superfamily of reptiles

Varanoidea is a superfamily of lizards, including the well-known family Varanidae. Also included in the Varanoidea are the Lanthanotidae, and the extinct Palaeovaranidae.

<span class="mw-page-title-main">Anguimorpha</span> Order of lizards

The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to Varanus and Anguis than Scincus. These lizards, along with iguanians and snakes, constitute the proposed "venom clade" Toxicofera of all venomous reptiles.

<i>Varanus <span style="font-style:normal;">(</span>Hapturosaurus<span style="font-style:normal;">)</span></i> Subgenus of reptiles

Hapturosaurus, sometimes known as the tree monitors, is a subgenus of lizards, consisting of slender-bodied arboreal monitor lizards mostly found in the tropical rainforests of Indonesia and Papua New Guinea.

Varanus hooijeri is an extinct species of medium-sized monitor lizard found in Liang Bua on Flores and possibly also Sumba, dating to the Late Pleistocene and Holocene.

<i>Varanus <span style="font-style:normal;">(</span>Varanus<span style="font-style:normal;">)</span></i> Subgenus of reptiles

Varanus, commonly known as true monitors, is one of the 11 subgenera of the genus Varanus. All of its species are found in the Australasian realm, among which are the world's largest lizards.

References

  1. 1 2 3 Owen R. (1859). "Description of Some Remains of a Gigantic Land-Lizard (Megalania Prisca, Owen) from Australia". Philosophical Transactions of the Royal Society of London. 149: 43–48. doi:10.1098/rstl.1859.0002. JSTOR   108688.
  2. 1 2 3 Price, Gilbert J.; Louys, Julien; Cramb, Jonathan; Feng, Yue-xing; Zhao, Jian-xin; Hocknull, Scott A.; Webb, Gregory E.; Nguyen, Ai Duc; Joannes-Boyau, Renaud (2015-10-01). "Temporal overlap of humans and giant lizards (Varanidae; Squamata) in Pleistocene Australia". Quaternary Science Reviews. 125: 98–105. Bibcode:2015QSRv..125...98P. doi:10.1016/j.quascirev.2015.08.013.
  3. ↑ Hideaki Kato (2021). 図解大事典 絶滅動物. 新星出版社. p. 229. ISBN   9784405073432.
  4. 1 2 Dick, Taylor J. M.; Clemente, Christofer J. (2016-02-18). "How to build your dragon: scaling of muscle architecture from the world's smallest to the world's largest monitor lizard". Frontiers in Zoology. 13: 8. doi: 10.1186/s12983-016-0141-5 . ISSN   1742-9994. PMC   4758084 . PMID   26893606.
  5. ↑ "Wildfacts - Megalania, giant ripper lizard". BBC. 2008. Archived from the original on 2011-12-27. Retrieved 2012-03-22.
  6. ↑ Lydekker R. (1888). Catalog of the fossil Reptilia in the British Museum (Natural History) Cromwell Road S.W. Pt. 1: The Orders Ornithosauria, Crocodilia, Squamata, Rhynchocephalia, and Proterosauria. London: The Trustees. Cited in Molnar RE (2004). "The long and honorable history of monitors and their kin". In King, Ruth Allen; Pianka, Eric R.; King, Dennis (eds.). Varanoid lizards of the world. Bloomington: Indiana University Press. p. 45. ISBN   978-0-253-34366-6.)
  7. 1 2 3 4 Molnar, Ralph E. (2004). Dragons in the dust: the paleobiology of the giant monitor lizard Megalania. Bloomington: Indiana University Press. ISBN   978-0-253-34374-1.
  8. 1 2 3 Molnar RE (2004). "History of monitors and their kin". In King, Ruth Allen; Pianka, Eric R.; King, Dennis (eds.). Varanoid lizards of the world. Bloomington: Indiana University Press. p. 588. ISBN   978-0-253-34366-6.
  9. 1 2 Head, JJ.; Barrett, PM.; Rayfield, EJ. (2009). "Neurocranial osteology and systematic relationships of Varanus (Megalania) prisca Owen, 1859 (Squamata: Varanidae)". Zoological Journal of the Linnean Society . 155 (2): 445–457. doi: 10.1111/j.1096-3642.2008.00448.x .
  10. ↑ Lee MSY (1996). "Possible affinities between Varanus giganteus and Megalania prisca". Memoirs of the Queensland Museum. 39: 232.
  11. ↑ Hecht, M. (1975). "The morphology and relationships of the largest known terrestrial lizard, Megalania prisca Owen, from the Pleistocene of Australia". Proceedings of the Royal Society of Victoria. 87: 239–250.
  12. ↑ Wroe, S. (2002). "A review of terrestrial mammalian and reptilian carnivore ecology in Australian fossil faunas, and factors influencing their diversity: the myth of reptilian domination and its broader ramifications". Australian Journal of Zoology. 50: 1–24. doi:10.1071/zo01053. Archived from the original on 2013-01-03. Retrieved 2012-03-22.
  13. 1 2 Fry, B.; Wroe, S.; Teeuwisse, W.; Van Osch, M. J. P.; Moreno, K.; Ingle, J.; McHenry, C.; Ferrara, T.; Clausen, P.; Scheib, H.; Winter, K. L.; Greisman, L.; Roelants, K.; Van Der Weerd, L.; Clemente, C. J.; Giannakis, E.; Hodgson, W. C.; Luz, S.; Martelli, P.; Krishnasamy, K.; Kochva, E.; Kwok, H. F.; Scanlon, D.; Karas, J.; Citron, D. M.; Goldstein, E. J. C.; McNaughtan, J. E.; Norman, J. A.; et al. (2009). "A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus". PNAS. 106 (22): 8969–74. Bibcode:2009PNAS..106.8969F. doi: 10.1073/pnas.0810883106 . PMC   2690028 . PMID   19451641.
  14. ↑ Wroe S, Myers TJ, Wells RT & Gillespie, A (1999). "Estimating the weight of the Pleistocene marsupial lion, Thylacoleo carnifex (Thylacoleonidae : Marsupialia): implications for the ecomorphology of a marsupial super-predator and hypotheses of impoverishment of Australian marsupial carnivore faunas". Australian Journal of Zoology. 47 (5): 489–498. doi:10.1071/ZO99006.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ↑ Hocknull SA, Piper PJ, van den Bergh GD, Due RA, Morwood MJ, Kurniawan I (2009). "Dragon's Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae)". PLOS ONE. 4 (9): e7241. Bibcode:2009PLoSO...4.7241H. doi: 10.1371/journal.pone.0007241 . PMC   2748693 . PMID   19789642.
  16. ↑ "Australia was 'hothouse' for killer lizards". Australian Broadcasting Corporation. 30 September 2009. Retrieved 30 September 2009.
  17. ↑ Flannery T (1994). The Future Eaters. Grove Press. pp. 384–5. ISBN   0-8021-3943-4.
  18. ↑ Clemente CJ, Thompson GG, Withers PC (2009). "Evolutionary relationships of sprint speed in Australian varanid lizards". Journal of Zoology. 278 (4): 270–280. doi: 10.1111/j.1469-7998.2009.00559.x .
  19. ↑ Bucklitsch, Yannick; Böhme, Wolfgang; Koch, André (2016-08-17). "Scale Morphology and Micro-Structure of Monitor Lizards (Squamata: Varanidae: Varanus spp.) and their Allies: Implications for Systematics, Ecology, and Conservation". Zootaxa. 4153 (1): 1–192. doi:10.11646/zootaxa.4153.1.1. ISSN   1175-5334. PMID   27615821.
  20. ↑ Vidal, Nicholas; Hedges, S. Blair (2009). "The molecular evolutionary tree of lizards, snakes, and amphisbaenians". Comptes Rendus Biologies. 332 (2–3): 129–139. doi:10.1016/j.crvi.2008.07.010. PMID   19281946. S2CID   23137302.
  21. ↑ Fry, B.; Vidal, Nicolas; Norman, Janette A.; Vonk, Freek J.; Scheib, Holger; Ramjan, S. F. Ryan; Kuruppu, Sanjaya; Fung, Kim; Blair Hedges, S.; Richardson, Michael K.; Hodgson, Wayne. C.; Ignjatovic, Vera; Summerhayes, Robyn; Kochva, Elazar; et al. (February 2006). "Early evolution of the venom system in lizards and snakes". Nature. 439 (7076): 584–588. Bibcode:2006Natur.439..584F. doi:10.1038/nature04328. PMID   16292255. S2CID   4386245.
  22. ↑ Barry C (2009). "Komodo Dragons Kill With Venom, Researchers Find". National Geographic News. Archived from the original on May 21, 2009. Retrieved 2012-03-22.
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