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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 sivalensis (Pliocene, India).A–B. NNM 17504, modern Varanus komodoensis humerus. C–D. NHMR 40819, distal humerus in dorsal (C) and ventral (D) views. E–I. NHMR 740, posterior dorsal vertebra compared with modern V. komodoensis (white) in anterior (E–F), left lateral (G–H) and dorsal (I) views. J–N. NHMR 739, anterior dorsal compared with modern V. komodoensis (white) in left lateral (J–K), anterior (L–M) and posterior (N) views. Scale bar = 1 cm.
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pone-0007241-g007: Varanus sivalensis (Pliocene, India).A–B. NNM 17504, modern Varanus komodoensis humerus. C–D. NHMR 40819, distal humerus in dorsal (C) and ventral (D) views. E–I. NHMR 740, posterior dorsal vertebra compared with modern V. komodoensis (white) in anterior (E–F), left lateral (G–H) and dorsal (I) views. J–N. NHMR 739, anterior dorsal compared with modern V. komodoensis (white) in left lateral (J–K), anterior (L–M) and posterior (N) views. Scale bar = 1 cm.

Mentions: Three specimens were previously described to represent Varanus sivalensis [23]–[25], a distal humerus and two dorsal vertebrae (anterior and mid-dorsal vertebrae). Whether these three specimens represent a single taxon (V. sivalensis) will depend on the discovery of more fossil specimens referable to this taxon. The humerus is morphologically distinct from Varanus komodoensis to warrant its unique taxonomic status; however, the two referred dorsal vertebrae fall within the variation of modern and fossil V. salvator. Therefore, it is unlikely that these three specimens represent the same taxon.


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 sivalensis (Pliocene, India).A–B. NNM 17504, modern Varanus komodoensis humerus. C–D. NHMR 40819, distal humerus in dorsal (C) and ventral (D) views. E–I. NHMR 740, posterior dorsal vertebra compared with modern V. komodoensis (white) in anterior (E–F), left lateral (G–H) and dorsal (I) views. J–N. NHMR 739, anterior dorsal compared with modern V. komodoensis (white) in left lateral (J–K), anterior (L–M) and posterior (N) views. Scale bar = 1 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0007241-g007: Varanus sivalensis (Pliocene, India).A–B. NNM 17504, modern Varanus komodoensis humerus. C–D. NHMR 40819, distal humerus in dorsal (C) and ventral (D) views. E–I. NHMR 740, posterior dorsal vertebra compared with modern V. komodoensis (white) in anterior (E–F), left lateral (G–H) and dorsal (I) views. J–N. NHMR 739, anterior dorsal compared with modern V. komodoensis (white) in left lateral (J–K), anterior (L–M) and posterior (N) views. Scale bar = 1 cm.
Mentions: Three specimens were previously described to represent Varanus sivalensis [23]–[25], a distal humerus and two dorsal vertebrae (anterior and mid-dorsal vertebrae). Whether these three specimens represent a single taxon (V. sivalensis) will depend on the discovery of more fossil specimens referable to this taxon. The humerus is morphologically distinct from Varanus komodoensis to warrant its unique taxonomic status; however, the two referred dorsal vertebrae fall within the variation of modern and fossil V. salvator. Therefore, it is unlikely that these three specimens represent the same taxon.

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