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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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Varanus komodoensis (Pliocene, Australia).A. Modern V. komodoensis skull in dorsal view (NNM 17504). B. QMF 874, right maxilla in lateral view. C. QMF 42105, partial right maxilla in dorsal view. D. QMF 42105, right maxilla in dorsal view. E. QMF 25392, complete left supraorbital in dorsal view. F. QMF 53956, partial parietal in dorsal view. G–H. QMF 42156, right quadrate in anterior and lateral views. I–J. QMF 870+871, partial left dentary in lingual view, J illustrating the tooth loci. Abbreviations: mcrst, dorsal maxillary crest; pmp, premaxillary-maxillary aperture; pms, premaxilla-maxilla suture; sym, dentary symphysis; mg, Meckalian groove. Dashed line represents broken edge of maxilla. Scale bar = 5 cm.
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pone-0007241-g002: Varanus komodoensis (Pliocene, Australia).A. Modern V. komodoensis skull in dorsal view (NNM 17504). B. QMF 874, right maxilla in lateral view. C. QMF 42105, partial right maxilla in dorsal view. D. QMF 42105, right maxilla in dorsal view. E. QMF 25392, complete left supraorbital in dorsal view. F. QMF 53956, partial parietal in dorsal view. G–H. QMF 42156, right quadrate in anterior and lateral views. I–J. QMF 870+871, partial left dentary in lingual view, J illustrating the tooth loci. Abbreviations: mcrst, dorsal maxillary crest; pmp, premaxillary-maxillary aperture; pms, premaxilla-maxilla suture; sym, dentary symphysis; mg, Meckalian groove. Dashed line represents broken edge of maxilla. Scale bar = 5 cm.

Mentions: Fossil specimens from Pliocene and Pleistocene-aged sites in Australia (Table 1) were identified as belonging to Varanus komodoensis on the basis of the following combination of unique cranial and post-cranial characteristics. Overall similar size and proportions of all preserved skeletal elements. Maxilla contributes to the labial margin of the premaxillary-maxillary aperture (pmp). Maxillary margin of the pmp shallow. Premaxillary-maxillary suture faces antero-lingually. Angulate maxillary crest. Labio-lingually compressed, closely-set recurved and serrated dentition both on maxillae and dentaries. At least 12 tooth loci in dentary. Parietal with distinct supratemporal crests, with fronto-parietal suture interlocking. Humerus stockier than all other members of Varanus, except V. prisca.


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. Modern V. komodoensis skull in dorsal view (NNM 17504). B. QMF 874, right maxilla in lateral view. C. QMF 42105, partial right maxilla in dorsal view. D. QMF 42105, right maxilla in dorsal view. E. QMF 25392, complete left supraorbital in dorsal view. F. QMF 53956, partial parietal in dorsal view. G–H. QMF 42156, right quadrate in anterior and lateral views. I–J. QMF 870+871, partial left dentary in lingual view, J illustrating the tooth loci. Abbreviations: mcrst, dorsal maxillary crest; pmp, premaxillary-maxillary aperture; pms, premaxilla-maxilla suture; sym, dentary symphysis; mg, Meckalian groove. Dashed line represents broken edge of maxilla. Scale bar = 5 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0007241-g002: Varanus komodoensis (Pliocene, Australia).A. Modern V. komodoensis skull in dorsal view (NNM 17504). B. QMF 874, right maxilla in lateral view. C. QMF 42105, partial right maxilla in dorsal view. D. QMF 42105, right maxilla in dorsal view. E. QMF 25392, complete left supraorbital in dorsal view. F. QMF 53956, partial parietal in dorsal view. G–H. QMF 42156, right quadrate in anterior and lateral views. I–J. QMF 870+871, partial left dentary in lingual view, J illustrating the tooth loci. Abbreviations: mcrst, dorsal maxillary crest; pmp, premaxillary-maxillary aperture; pms, premaxilla-maxilla suture; sym, dentary symphysis; mg, Meckalian groove. Dashed line represents broken edge of maxilla. Scale bar = 5 cm.
Mentions: Fossil specimens from Pliocene and Pleistocene-aged sites in Australia (Table 1) were identified as belonging to Varanus komodoensis on the basis of the following combination of unique cranial and post-cranial characteristics. Overall similar size and proportions of all preserved skeletal elements. Maxilla contributes to the labial margin of the premaxillary-maxillary aperture (pmp). Maxillary margin of the pmp shallow. Premaxillary-maxillary suture faces antero-lingually. Angulate maxillary crest. Labio-lingually compressed, closely-set recurved and serrated dentition both on maxillae and dentaries. At least 12 tooth loci in dentary. Parietal with distinct supratemporal crests, with fronto-parietal suture interlocking. Humerus stockier than all other members of Varanus, except V. prisca.

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