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Dragon's paradise lost: palaeobiogeography, evolution and extinction of the largest-ever terrestrial lizards (Varanidae).

Hock SA, Piper PJ, van den Bergh GD, Due RA, Morwood MJ, Kurniawan I - PLoS ONE (2009)

Bottom Line: Giant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene.Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor.The events over the last two millennia now threaten its future survival.

View Article: PubMed Central - PubMed

Affiliation: Geosciences, Queensland Museum, Brisbane, Queensland, Australia. scott.hock@qm.qld.gov.au

ABSTRACT

Background: The largest living lizard species, Varanus komodoensis Ouwens 1912, is vulnerable to extinction, being restricted to a few isolated islands in eastern Indonesia, between Java and Australia, where it is the dominant terrestrial carnivore. Understanding how large-bodied varanids responded to past environmental change underpins long-term management of V. komodoensis populations.

Methodology/principal findings: We reconstruct the palaeobiogeography of Neogene giant varanids and identify a new (unnamed) species from the island of Timor. Our data reject the long-held perception that V. komodoensis became a giant because of insular evolution or as a specialist hunter of pygmy Stegodon. Phyletic giantism, coupled with a westward dispersal from mainland Australia, provides the most parsimonious explanation for the palaeodistribution of V. komodoensis and the newly identified species of giant varanid from Timor. Pliocene giant varanid fossils from Australia are morphologically referable to V. komodoensis suggesting an ultimate origin for V. komodoensis on mainland Australia (>3.8 million years ago). Varanus komodoensis body size has remained stable over the last 900,000 years (ka) on Flores, a time marked by major faunal turnovers, extinction of the island's megafauna, the arrival of early hominids by 880 ka, co-existence with Homo floresiensis, and the arrival of modern humans by 10 ka. Within the last 2000 years their populations have contracted severely.

Conclusions/significance: Giant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene. Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor. The events over the last two millennia now threaten its future survival.

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Related in: MedlinePlus

Varanus komodoensis (Pliocene, Australia).A–F. QMF 42104, posterior dorsal vertebra compared with modern V. komodoensis (white), in anterior (A–B), posterior (C–D) and left lateral (E–F) views. G–L. QMF 42096, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (G–H), posterior (I–J) and right lateral (K–L) views. M–R. QMF 42102, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (M–N), posterior (O–P) and left lateral (Q–R) views. S–V. QMF 23684, cervical vertebra compared with modern V. komodoensis (white), in left lateral (S–T) and anterior (U–V) views. W–X. QMF 23686, anterior dorsal vertebra compared with modern V. komodoensis (white) in anterior view. Scale bar = 1 cm.
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pone-0007241-g004: Varanus komodoensis (Pliocene, Australia).A–F. QMF 42104, posterior dorsal vertebra compared with modern V. komodoensis (white), in anterior (A–B), posterior (C–D) and left lateral (E–F) views. G–L. QMF 42096, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (G–H), posterior (I–J) and right lateral (K–L) views. M–R. QMF 42102, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (M–N), posterior (O–P) and left lateral (Q–R) views. S–V. QMF 23684, cervical vertebra compared with modern V. komodoensis (white), in left lateral (S–T) and anterior (U–V) views. W–X. QMF 23686, anterior dorsal vertebra compared with modern V. komodoensis (white) in anterior view. Scale bar = 1 cm.

Mentions: A right (QMF 53955) and a left (QMF 53954) humerus, both missing the proximal and distal-most epiphyses are of similar size and morphology to V. komodoensis. The humeri of V. priscus and V. komodoensis are stocky and robust when compared to humeri found in all other members of Varanus. Both fossil humeri indicate a stout humerus with broad proximal and distal epiphyses. When comparing the maximum diaphyseal width of the two specimens with species of extant and fossil Varanus, both specimens fall within the size range of V. komodoensis and outside that of small and large Varanus prisca (Figure S3).


Dragon's paradise lost: palaeobiogeography, evolution and extinction of the largest-ever terrestrial lizards (Varanidae).

Hock SA, Piper PJ, van den Bergh GD, Due RA, Morwood MJ, Kurniawan I - PLoS ONE (2009)

Varanus komodoensis (Pliocene, Australia).A–F. QMF 42104, posterior dorsal vertebra compared with modern V. komodoensis (white), in anterior (A–B), posterior (C–D) and left lateral (E–F) views. G–L. QMF 42096, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (G–H), posterior (I–J) and right lateral (K–L) views. M–R. QMF 42102, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (M–N), posterior (O–P) and left lateral (Q–R) views. S–V. QMF 23684, cervical vertebra compared with modern V. komodoensis (white), in left lateral (S–T) and anterior (U–V) views. W–X. QMF 23686, anterior dorsal vertebra compared with modern V. komodoensis (white) in anterior view. Scale bar = 1 cm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2748693&req=5

pone-0007241-g004: Varanus komodoensis (Pliocene, Australia).A–F. QMF 42104, posterior dorsal vertebra compared with modern V. komodoensis (white), in anterior (A–B), posterior (C–D) and left lateral (E–F) views. G–L. QMF 42096, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (G–H), posterior (I–J) and right lateral (K–L) views. M–R. QMF 42102, mid-dorsal vertebra compared with modern V. komodoensis (white), in anterior (M–N), posterior (O–P) and left lateral (Q–R) views. S–V. QMF 23684, cervical vertebra compared with modern V. komodoensis (white), in left lateral (S–T) and anterior (U–V) views. W–X. QMF 23686, anterior dorsal vertebra compared with modern V. komodoensis (white) in anterior view. Scale bar = 1 cm.
Mentions: A right (QMF 53955) and a left (QMF 53954) humerus, both missing the proximal and distal-most epiphyses are of similar size and morphology to V. komodoensis. The humeri of V. priscus and V. komodoensis are stocky and robust when compared to humeri found in all other members of Varanus. Both fossil humeri indicate a stout humerus with broad proximal and distal epiphyses. When comparing the maximum diaphyseal width of the two specimens with species of extant and fossil Varanus, both specimens fall within the size range of V. komodoensis and outside that of small and large Varanus prisca (Figure S3).

Bottom Line: Giant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene.Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor.The events over the last two millennia now threaten its future survival.

View Article: PubMed Central - PubMed

Affiliation: Geosciences, Queensland Museum, Brisbane, Queensland, Australia. scott.hock@qm.qld.gov.au

ABSTRACT

Background: The largest living lizard species, Varanus komodoensis Ouwens 1912, is vulnerable to extinction, being restricted to a few isolated islands in eastern Indonesia, between Java and Australia, where it is the dominant terrestrial carnivore. Understanding how large-bodied varanids responded to past environmental change underpins long-term management of V. komodoensis populations.

Methodology/principal findings: We reconstruct the palaeobiogeography of Neogene giant varanids and identify a new (unnamed) species from the island of Timor. Our data reject the long-held perception that V. komodoensis became a giant because of insular evolution or as a specialist hunter of pygmy Stegodon. Phyletic giantism, coupled with a westward dispersal from mainland Australia, provides the most parsimonious explanation for the palaeodistribution of V. komodoensis and the newly identified species of giant varanid from Timor. Pliocene giant varanid fossils from Australia are morphologically referable to V. komodoensis suggesting an ultimate origin for V. komodoensis on mainland Australia (>3.8 million years ago). Varanus komodoensis body size has remained stable over the last 900,000 years (ka) on Flores, a time marked by major faunal turnovers, extinction of the island's megafauna, the arrival of early hominids by 880 ka, co-existence with Homo floresiensis, and the arrival of modern humans by 10 ka. Within the last 2000 years their populations have contracted severely.

Conclusions/significance: Giant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene. Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor. The events over the last two millennia now threaten its future survival.

Show MeSH
Related in: MedlinePlus