Name: Varanus
priscus
Phonetic: Vah-ran-us priss-cuss.
Named By: Varanus was established by Blasius Merrem
in 1820. The species Varanus priscus was originally named as
Megalania prisca by Richard Owen in 1859.
Synonyms: Megalania prisca.
Classification: Chordata, Reptilia, Squamata,
Platynota, Varanoidea, Varanidae.
Species: V. priscus (type).
Diet: Carnivore.
Size: Estimated between 4.5 and 7 meters
long, sometimes estimated being slightly bigger at up to 8 meters
long, depending upon similarity to other large lizards.
Known locations: Australia.
Time period: Pleistocene.
Fossil representation: Scattered and incomplete
remains.
The giant goanna
For
roughly one hundred and fifty years Varanus priscus
went by the name of
Megalania prisca, however modern interpretations
of this ancient
lizard mostly concur that it is actually a species of the current
Varanus genus of monitor lizards that we know
today. Because it has
appeared in many books, websites and television shows under the older
name in the past, most people still refer to it as Megalania.
Normally when a genus is absorbed into another to create a new
species, the original species epithet is used, but Megalania
is a
feminine term whereas Varanus is a masculine one.
As such instead of
becoming Varanus prisca as would usually happen,
the species name had
to altered to become Varanus priscus instead.
Palaeontologists
have been trying to identify the closest living relative of this giant
monitor lizard since it was first discovered and similarities between
it and living monitor lizards were established even before it was moved
into the same family as them. Today the largest monitor in Australia
is the Perentie (Varanus giganteus), but most
consider the Lace
monitor (Varanus varius) to be a better
analogy. Still another
contender for similar ecological niche is the Komodo dragon (Varanus
komodoensis) that is currently the largest known monitor
lizard.
Because
Varanus priscus remains are still largely
incomplete, reconstructions
and size estimates are based upon comparisons to other monitor
lizards. Unfortunately not only are there different methods of
comparison, different monitors have different body proportions, all
things that have resulted in a range of sizes. Stephen Wroe
established in 2002 that this lizard could range between three and
half and four and a half meters, but a conflicting study by Ralph
Molnar in 2004 propositioned that Varanus priscus
(still known as
Megalania) could grow between seven and eight
meters long. Molnar’s
results depended upon comparison to a Komodo dragon for seven meters,
and a Lace monitor for just under eight, although the latter has a
proportionately longer tail relative to its body size.
Hunting and position in the
ecosystem
The
ecosystems of Pleistocene Australia had animals that were very
different to the rest of the world thanks mostly to the continents
isolation. Here there were a number of large flightless birds that
were similar to others that had long gone extinct upon other
continents. One of the largest animal groups were marsupial mammals,
already rare in other parts of the world and represented by giant
wombats like Diprotodon
and Phascolonus, and giant Kangaroos like
Procoptodon,
all of which would have been valid prey animals for a
large meat eater like Varanus priscus. The
mammals would have been
especially susceptible to attacks from a large mouthed, sharp,
serrated toothed predator which could have done a lot of damage to
their soft unarmoured bodies. However there was also competition for
the position of apex predator with other predators including the
terrestrial crocodile Quinkana
which may have rivalled Varanus priscus
in size, and the marsupial lion Thylacoleo.
Varanus
priscus was not just a big lizard, it had a very robust
construction, especially the skull that could withstand a lot of
stress and punishment. We also know that living monitor lizards,
especially larger species have very tough scales that have often been
described as being similar to chainmail. Varanus priscus
also
probably didn’t have to rely upon its mouth to attack animals as others
like the Komodo dragon have been observed using their tails to knock
prey animals off their feet so that they can’t run away.
One
area where Varanus priscus fell short however was
running speed, as
although monitor lizards are very quick to accelerate, they cannot
match dedicated runners in a flat race once they have got up to speed.
This means that Varanus priscus would typically
have to operate in a
very narrow window of opportunity when prey was just close enough to
attack without giving it time to escape. This suggests that its
behaviour would be centred on the use of using ambush tactics such as
lurking in the undergrowth and staying near game trails and watering
holes like other predators do in order to maximise their chances of
coming into contact with prey. Of course just like some monitor
lizards do today, Varanus priscus may have also
actively sought out
carrion, or even driven other predators like Thylacoleo
from their
kills.
The
most important sense for monitor lizards is that of smell, and this
can be seen in the way that they frequently flick out their tongues.
Every time the tongue shoots out it picks up scent particles in the
air of its surface which then get tasted by an organ in the snout when
the tongue is flicked out. The tongue is also forked so that when
one prong picks up a greater coating of particles than the other the
lizard knows which direction to turn in. The lizard then follows the
scent till it finds the source which can be anything from a carcass to
a sick or injured animal. In the case of the latter the excellent
vision then comes into use, although living monitor lizards seem to
be most suited to seeing in daylight conditions. Varanus
priscus
would have likely displayed this tracking behaviour, but on scale
that saw it hunting the other megafauna alive at that time.
Although
direct evidence is lacking, Varanus priscus is
generally thought to
have been able to use venom from glands that would have been in the
lower jaw. This is based upon research concerning the Komodo dragon
by the University of Melbourne that began in 2005. Wild Komodo
dragons have long been presumed to have a toxic bite from the number of
bacteria strains that have been sampled from the saliva of wild
specimens that are notably absent from those living in captivity.
It’s possible that this bacteria living in the mouth of wild Komodo
dragons is the result of them feeding from carcasses where bacteria
such as E. coli are present. CAT Scanning of
Komodo dragon heads
confirmed the presence of internal organs in the lower jaws that later
removal and study revealed to be venom glands. Venom from these
glands that contains agents that prevent the blood from clotting as
well as causing other problems such as muscle paralysis passes
through pores in the mouth to mix with the saliva. As the Komodo
dragons teeth puncture and tear the flesh of their prey, the venom
mixes into the wound so that not only does the prey suffer massive
blood loss from the damage of the bite, it also has to contend with
the effects of the venom on top of that.
It’s
still impossible to be absolutely certain if Varanus priscus
also had
this venom producing ability, but so far it seems that all other
members of the Varanus genus alive today also have
these venom glands.
By relation to these other species it would actually be unusual if
Varanus priscus did not have venom glands, and if
it did indeed have
them it would possibly be the largest venomous animal ever to have
existed. Utilising venom in its hunting would also make it a much
more effective predator of the large Australian megafauna from giant
wombats like Diprotodon, to possibly even large
flightless birds like
Genyornis.
Varanus priscus/Megalania
prisca
in cryptozoology
As
far as science is currently concerned Varanus priscus
exists only in
the fossil record, and died out at around the time of most of the
other large Australian megafauna. Despite this there are still
occasional sightings of both huge lizards and large animals like cattle
that have been completely butchered and torn apart coming from the
Australian outback. Reports are also known from nearby New Guinea of
similar large monitor lizards.
Critics
of these stories often point out a number of theories as to why it
is impossible for giant monitor lizards to still be alive. One is
that Australia today has a far more arid climate than what it had
during the Pleistocene, and that the large mammals that Varanus
Priscus preyed upon are no longer present. Some critics
also claim
that people who claim to have seen giant monitor lizards are simply
misinterpreting animals like crocodiles or even inanimate objects such
as logs. Critics often also accuse witnesses of making the story up,
although grounds for this accusation must always be established on a
case by case basis. One of the most popular theories against large
monitor lizards being alive is that they are so huge it should be
impossible for them to hide. Another is that it takes a population of
several individuals for a species to survive which means that not just
one but several giant lizards should be being seen. These are all
valid points that should be seriously considered, however there is
another set of theories that counter these ideas.
First
is that while most of Australia is arid grassland and desert, there
are extensive areas of lush forest and swamps that cover areas that are
larger than some small countries. With most of the Australian
population living in built up areas of relatively small size, these
outback areas are not often explored, and parts remain unknown to
this day. Also when people describe the creature that they see they
usually use the term ‘goanna’ (in Australia monitor lizards are
more commonly called goannas) and not only insist that they are
seeing a goanna and not a croc, but that the lizard was moving.
Animals that could support a large monitor lizard also exist in the
form of kangaroos, buffalo, and domestically sourced animals like
cattle and horses.
Perhaps
most frightening of all these possibilities is the observation of how
females of the related Komodo dragon that have not had any contact with
males, still lay eggs that are fertile enough for a young komodo
dragon to hatch out. Assuming Varanus priscus as
a very closely
related animal had the ability to lay eggs by parthenogenesis
(without sexual reproduction), this species would not need a large
population to survive, just a few females. This is something that
could also be key to their survival since large predatory animals do
not normally have large populations as to avoid exhausting the
available prey in an ecosystem. Additionally wild monitor lizards
known to exist, including the large Perentie (Varanus
giganteus)
usually exhibit shy behaviour around humans, often retreating when
they detect them.
Despite
all this there is still currently no direct evidence for the continued
existence of Varanus priscus, and without a body
or exceptionally
conclusive video or photographic evidence it will continue to be
regarded as an extinct reptile. But as the saying goes, absence of
evidence is not evidence of absence, and many of the creatures we
know today were once regarded as not possibly being real. One of the
best examples of this is that of the gorilla, an animal that was once
considered by science to be a mythical creature that only existed in
African folklore until one was actually shot and documented. The
potential for the existence for large monitor lizards in Australia
exists, but this does not necessarily mean that they are surviving
examples of Varanus priscus.
Further reading
- Description of Some Remains of a Gigantic Land-Lizard (Megalania
Prisca, Owen) from Australia - Philosophical Transactions of
the Royal
Society of London - Richard Owen - 1859.
- 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. - M. Hecht -
1975.
- Rebuilding a giant lizard. - In Clayton, Georgina; Archer, Michael.
Vertebrate zoogeography & evolution in Australasia: (animals in
space and time). Carlisle, W.A.: Hesperian Press - T. Rich & B.
Hall - 1984.
- Possible affinities between Varanus giganteus and
Megalania prisca. -
Memoirs of the Queensland Museum 39: 232. - M. S. Y. Lee - 1996.
- 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. - S. Wroe - 2002.
- Megafaunal extinction in the late Quaternary and the global overkill
hypothesis - Alcheringa 28: 291–33 - S. Wroe, J. Field, R. Fullagar
& L. S. Jermiin - 2004.
- Neurocranial osteology and systematic relationships of Varanus
(Megalania) prisca Owen, 1859
(Squamata: Varanidae). - Zoological
Journal of the Linnean Society 155: 445–457. - J. J. Head, P. M. Barret
& E. J. Rayfield - 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. - Bryan G. Fry, Stephen Wroe, Wouter Teeuwisse, Matthias
J. P. van Osch, Karen Moreno, Janette Ingle, Colin McHenry, Toni
Ferrara, Phillip Clausen, Holger Scheib, Kelly L. Winter, Laura
Greismana, Kim Roelants, Louise van der Weerd, Christofer J. Clemente,
Eleni Giannakis, Wayne C. Hodgson, Sonja Luz, Paolo Martelli,
Karthiyani Krishnasamy, Elazar Kochva, Hang Fai Kwok, Denis Scanlon,
John Karas, Diane M. Citron, Ellie J. C. Goldstein, Judith E.
Mcnaughtan & Janette A. Norman - 2009.
- Temporal overlap of humans and giant lizards (Varanidae; Squamata) in
Pleistocene Australia. - Quaternary Science Reviews. 125: 98–105. -
Gilbert J. Price, Julien Louys, Jonathan Cramb, Yue-xing Feng, Jian-xin
Zhao, Scott A. Hocknull, Gregory E. Webb, Ai Duc Nguyen &
Renaud Joannes-Boyau - 2015.