Designation is controversial: Eitheror
Megalania prisca Owen, 1859
Varanus priscus (Owen, 1859)
Megalania prisca or
Varanus priscus) is an extinct giant
goanna or monitor lizard. They were part of a megafaunal assemblage
that inhabited southern
Australia during the Pleistocene. The youngest
fossil remains date to around 50,000 years ago. The first
aboriginal settlers of
Australia might have encountered them and been
a factor in their extinction.
3.2 Possible Parthenogenesis
Illustration of the original dorsal and cervical vertebrae, 1859
Megalania prisca was coined in 1859 by Sir
Richard Owen to
mean "ancient great roamer"; the name was chosen "in reference to the
terrestrial nature of the great Saurian". 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.
Owen introduced the genus
Megalania to accommodate the species
Megalania prisca. Its status as a valid genus remains controversial,
with many authors preferring to consider it a junior synonym of
Varanus, which encompasses all living monitor lizards. As the
gender of the genera
Varanus are respectively feminine
and masculine, the specific name prisca (fem.)/priscus (masc.) follows
Megalania is included as a synonym of
Varanus by many
researchers due to the relationships of the many
Varanus species; M.
prisca is closely related to other Australian monitors classified as
Varanus, so excluding M. prisca 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
Several studies have attempted to establish the phylogenetic position
of megalania within the Varanidae. An affinity with the perentie,
Australia's largest living lizard, has been suggested based on
skull-roof morphology. The most recent comprehensive study
proposes a sister-taxon relationship with the
Komodo dragon based on
neurocranial similarities, with the lace monitor as the closest living
Australian relative. Conversely, the perentie is considered more
closely related to the Gould's and argus monitors.
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. 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). 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). decrying the earlier maximum length estimate
of 7 m (23 ft) as exaggerations based on flawed methods.
However, in 2009, Wroe, along with other researchers revised upwards
their estimates to at least 5.5 m (18 ft) and 575 kg
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
Varanus varius), then it would have reached a length of 7.9
metres (26 ft), while if its tail-to-body proportions were more
similar to that of the
Komodo dragon (
Varanus komodoensis), then a
length of 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)
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 like Diprotodon
along with other reptiles and small mammals, as well as birds and
their eggs and chicks. It had heavily built limbs and
body and a large skull complete with a small crest in between the
eyes, and a jaw full of serrated blade-like teeth.
Some scientists regard with skepticism the contention that Megalania
was the only, or even principal, predator of the Australian
Pleistocene megafauna. They note that the "marsupial lion"
(Thylacoleo carnifex) has been implicated with the butchery of very
Pleistocene mammals, while
Megalania has not. In addition, they
Megalania fossils are extremely uncommon, in contrast to
Thylacoleo carnifex with its wide distribution across Australian
Pleistocene deposits. Quinkana, a genus of terrestrial crocodile that
grew up to 6m and was present until around 40,000 years ago, has also
been marked as another apex predator of Australian megafauna.
It has been suggested that, if one were to reconstruct the ecosystems
that existed before the arrival of the humans on Australia, it would
be desirable to introduce Komodo dragons to represent megalania.
A study published in 2009 utilizing 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
The scales of megalania would possibly be similar to that of their
extant relatives possessing a honey comb micro structure and be
durable and resilient to water evaporation.
Megalania skull, at Museum of Science, Boston
Along with other varanid lizards, such as the
Komodo dragon and the
lace monitor, megalania belongs to the proposed clade Toxicofera,
which contains all known reptile clades possessing toxin-secreting
oral glands, as well as their close, non-venomous relatives, including
Iguania, Anguimorpha, and Serpentes. Closely related
varanids use a potent venom found in glands inside the jaw. The venom
in these lizards have been shown to be a hemotoxin. 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.
One of the assumed closely related species to megalania are the Komodo
dragons. A recent finding was that they are one of the few large
animals to actually exhibit parthenogenesis, asexual reproduction.
Recent paleontological analysis using accelerator mass spectrometry
(AMS) 14C dating of known fossils shows megalania to have been alive
Pleistocene epoch 50,000 years ago. An affiliate hypothesis to
these datings is that anthropogenic extirpation was the cause of the
downfall of megalania and other
Australian megafauna in the similar
vein as to how a large factor of the extinction of the northern
hemisphere’s megafauna at the end of the
Pleistocene epoch was
caused by early humans. In addition a research study which examined
the morphology of nine closely related extant varanid lizards and then
allometrically scaled and compared it to v. prisca found that the
musculature of the limbs, posture, muscular mass, and possible
muscular composition of the animal would most likely be inefficient to
outrun the early humans settlers that would colonize
that time period. This, in coordination with other megafauna that
lived at that time such as quinkana and Thylacoleo carnifex, and
possible climate change could have led to the species
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