Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 4 (9), e7241

Dragon's Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae)

Affiliations

Dragon's Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae)

Scott A Hocknull et al. PLoS One.

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.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Morphometric measurements.
A. Pre-postzygapophysis length. B. Centrum length. C. Cotylar width. D. Post-postzygapophysis width. E. Pre-prezygapophysis width. F. Tooth crown height. G. Tooth base length. H. Diaphysis width (humerus). I. Distal condyle width (humerus).
Figure 2
Figure 2. 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.
Figure 3
Figure 3. Varanus komodoensis (Neogene, Australia).
A–B, E–G. Pliocene V. komodoensis (Australia)A–B. QMF 53955, partial left humerus in dorsal view showing position of insertion for the latissimus dorsi (lat dors). C–D. Left and right humerus of a modern V. komodoensis (NNM 17504). E–F. QMF 53954, partial right humerus in ventral and dorsal views, showing the position of the ectepicondyle (ect). G. QMF 866, partial scapulocoracoid. H–P. Pleistocene V. komodoensis (Australia). H–I. QMF 54605, partial left maxilla in lingual and labial views. J. QMF 54606, partial right quadrate in anterior view. K. QMF 54607, supraoccipital bone in posterior view. L. QMF 54608, proximal left tibia. M. QMF 54604, ulna diaphysis. N–P. QMF 1418, proximal mid-caudal in cranial, oblique lateral and dorsal views. Scale bar = 1 cm.
Figure 4
Figure 4. 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.
Figure 5
Figure 5. Varanus komodoensis (Pleistocene, Flores).
A–B. Sacral vertebrae from modern (A) and fossil (LB558a) V. komodoensis in anterior view. C. Articulated dorsal vertebrae (LB19/20-9-04) in dorsal view. D. Cervical vertebra (LB517b) in dorsal view. E. Four isolated teeth (LB04 unreg) in lingual view. F–H. Ulna diaphysis (LB-447a/16.8.04) in medial (F), cranial (G) and lateral (H) views. I. Radius diaphysis (LB-28.7.03) in medial view. Scale bar = 1 cm.
Figure 6
Figure 6. Varanus sp. cf. V. komodoensis and V. salvator (Pleistocene, Java).
A–F. V. sp. cf. V. komodoensis. Anterior dorsal vertebra (CD 6392) compared with modern V. komodoensis in anterior (A–B), dorsal (C–D) and left lateral view (E–F). G–K. V. salvator. G–I. CD 8873, mid-dorsal vertebra, compared with modern V. komodoensis in dorsal (G–H) and anterior (H–I) views. J–K. CD 216, sacral vertebra, compared with modern V. komodoensis in anterior view. Scale bar = 1 cm.
Figure 7
Figure 7. 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.
Figure 8
Figure 8. Varanus sp. nov. (Pleistocene, Timor).
A–F. Mid-dorsal vertebra (CV Raebia 1) compared with modern V. komodoensis in anterior (A–B), left lateral (C–D), dorsal (E–F) views. G–L. Anterior caudal vertebra (CV Raebia 2) compared with modern V. komodoensis in anterior (G–H), dorsal (I–J) and oblique posterior (K–L) views. M–R. Sacral vertebra (CV Raebia 3) compared with modern V. komodoensis in anterior (M–N), dorsal (O–P) and ventral (Q–R) views. S. QMF 8968, sacral vertebra of Varanus prisca in anterior view.
Figure 9
Figure 9. Palaeogeography and chronology of giant varanids.
Schematic diagram illustrating the proposed taxonomy, chronology and dispersal sequence of giant varanids from mainland Australia to the Indonesian islands of Timor, Flores and Java during the Pliocene-Pleistocene.

Similar articles

See all similar articles

Cited by 9 PubMed Central articles

See all "Cited by" articles

References

    1. Owen R. Description of some remains of a gigantic land-lizard (Megalania prisca, Owen) from Australia. Philosophical Transactions of the Royal Society of London. 1859;149:43–48.
    1. Molnar RE. Indiana: Indiana University Press.; 2004. Dragons in the Dust: The palaeobiology of the Giant Monitor Lizard Megalania.210
    1. Auffenberg W. Gainesville FL: University Press of Florida.; 1981. The Behavioural Ecology of the Komodo Monitor.406
    1. Pianka ER. Evolution of body-size: Varanid lizards as a model system. American Naturalist. 1995;146(3):398–414.
    1. Christian A, Garland Scaling of Limb Proportions in Monitor Lizards (Squamata: Varanidae). Journal of Herpetology. 1996;30(2):219–230.

Publication types

Feedback