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Obscure and attractive monitor lizards to know and love

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Varanid portraits.

Everybody loves monitor lizards, or varanids. And there is so much to learn about, and to appreciate, in these remarkable, charismatic, complex, sophisticated lizards that scientists across many disciplines are being encouraged to study them and – lo – to make remarkable discoveries. In recent months we’ve seen the discovery of a mammal-like rate of blood flow to varanid limb bones (Seymour et al. 2011), further documentation of ‘tail-assisted foraging’ (Patanant 2012), the demonstration of rapid, sophisticated coordination between jaw gaping and neck and forelimb movement during prey-grabbing (Montuelle et al. 2012a, b), and the recognition that varanids possess a unidirectional system of breathing (Schachner et al. 2013). What seems to be the first documented human death caused by varanid oral toxins – the death was that of a 55 year old woman, bitten by a Bengalese monitor Varanus bengalensis – was also published just a few weeks ago (Vikrant & Verma 2013). Yet more amazing stuff on varanids is due to hit the presses soon.

Charismatic Water monitor (V. salvator). Image by Tony Gamble, used with permission.

Varanids have been covered a few times here at Tet Zoo, but never in appropriate depth (see the links below). Of course, what I’d really like to do is produce a huge series of articles that covers the entire radiation in all of its glory, but I’ve learnt from bitter experience that finishing long multi-part reviews of that sort is tremendously difficult, if not impossible. Dammit, if only there wasn’t all that non-blogging stuff I have to do. Anyway, with all of the above in mind, here’s another article in which I look at just a few species.

Monitors: more and more and more

Blue-spotted tree monitor (V. macraei), one of many newly recognised monitors named in recent years (this one was named in 2001). Image by Tony Gamble, used with permission.

For no special reason other than that I find them neat, I focus this time round on several fairly obscure monitors from Indonesia and Australasia. There’s a huge amount of diversity and complexity in the monitors of this region, with recent work showing that we’ve seriously underestimated the taxonomic and phylogenetic diversity of these lizards. New species are described on a regular basis, and morphological and molecular investigations have both shown that many ‘species’ are actually species complexes, sometimes containing lineages that are not especially closely related.

As I’ve said on Tet Zoo before, I can certainly remember a time (I was born in the 1970s) when people said that there were “about 25” living monitor species. Within recent years, we’ve seen that figure creep up to 50 and beyond, then to 60 and 70 and beyond. Current lists recognise about 72, but this will continue to escalate given that distinct lineages await naming in species complexes like the water monitors, mangrove monitors, Timor monitors and banded tree monitors. As many as “10 as yet undescribed new species” might exist in the current concept of the Australian spotted tree monitor V. scalaris alone, according to some workers (L. Smith, in Jennings & Pianka 2004), for example.

Dumeril’s monitor

Dumeril's monitor in profile: note nostril position and the large nuchal scutes. Image by Darren Naish.

We start with the extremely poorly known but odd and perhaps highly specialised Dumeril’s monitor V. dumerilii, a widespread SE Asian varanid known from Thailand, Burma, the Malayan Peninsula, Borneo, Sumatra and some smaller islands. A single specimen has also been reported from Java and uncertainly remains over the distribution of the species towards the east and north (Bennett 2004). This animal is unmistakeable: creamish transverse bands separate dark brown, mottled areas on the dorsal surface and black temporal stripes extend from behind the eyes and along the neck. Hatchlings combine glossy black with bright orange or yellow crossbands and a vividly coloured head. Vague suggestions have been made that this patterning might represent cobra mimicry (Bennett 1994) but this hypothesis requires testing. It’s a reasonably large monitor, reaching 1.25 m in total at most (1.5 m has been widely claimed but may be erroneous).

Observational data on wild Dumeril’s monitor is few and far between. The species is said to be sedentary, well able to climb, but also keen to take to water. In fact, an association with coastal mangroves and an apparent fondness of crabs suggest that it’s well adapted for aquatic foraging: Krebs (1979) considered it a crab specialist. This idea is consistent with some aspects of this varanid’s anatomy. Its skull is relatively flat and broad (features generally consistent with a lifestyle that involves swimming, or foraging between rocks), its nostrils are located well away from the tip of the snout, its teeth are blunt and peg-like [UPDATE: apparently this is not true! More later], and it possesses nasal valves that allows it to close its nostrils when submerged. Its tail is laterally compressed, too. Some observers talk of Dumeril’s monitors emptying their lungs and walking along the bottoms of streams and even taking to the sea to escape harassment from dogs (Bennett 1994, Steel 1996).

Captive Dumeril's monitor, photographed by Katerina Zareva; licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Rough-necked monitor (V. rudicollis), one of the weirdest members of Varanidae. Mertens considered it distinct enough for its own subgenus, Dendrovaranus. Photo by Darren Naish.

Large, irregularly positioned scales cover the dorsal surface of its neck. [Image above by Katerina Zareva, EERC Sofia Zoo.]  These superficially recall those present in the Rough-necked monitor V. rudicollis and both species have been confused on occasion (see Sprackland 1993). Both appear to be members of the same varanid clade (the one that also includes water monitors and mangrove monitors in most – but not all – phylogenies), but they’re not especially close (Ast 2001, Vidal et al. 2012, Pyron et al. 2013).

On the subject of phylogeny: for all their fame and attraction as research subjects, surprisingly little has been done on varanid phylogeny since Jennifer Ast’s paper of 2001. Most studies that look at phylogenetic patterns use her tree. Nothing wrong with that, but more studies would be good. You’ll note that I’m citing Pyron et al.’s (2013) gigantic study of lizard phylogeny, of course. Collar et al. (2011) also produced a novel varanid phylogeny but it doesn’t include the species discussed in this article. I should also make honorary mentions of Conrad et al. (2012), Vidal et al. (2012) and Welton et al. (2014).

Timor monitors: extralimital odatrians

Varanus timorensis in profile; image by Darren Naish.

Moving on, here’s a portrait of a Timor monitor V. timorensis, another very poorly known, small monitor (total length up to 60 cm), this time marked dorsally with transversely arranged ocelli arranged in bands. The tail is round in cross-section. It’s a climbing animal of tropical forests, threatened by the clearing for agriculture of its habitat. As goes distribution, the Timor monitor is probably endemic to Timor and a few of the tiny islands nearby (Savu, Roti and Semau). However, when named by John Gray in 1831 it was regarded as a tremendously widespread animal that occurred from the Lesser Sundas eastwards to New Guinea and then south to northern Australia. Gray thought that V. scalaris, now regarded as a separate species and sometimes called the Australian spotted tree monitor, was conspecific with the Timor monitor – a mess that wasn’t really sorted out until 2001 or so. Even with V. scalaris out of the mix, it still seems that ‘V. timorensis’ is a composite: the populations of Timor and the nearby islands are fairly variable and cryptic species are probably present. The population from Roti was named V. auffenbergi in 1999 (Sprackland 1999) and has variously been termed the Peacock monitor or Auffenberg’s monitor.

Australian spotted tree monitor (V. scalaris); image (c) Stephen Zozaya, used with permission.

The Timor monitor has always been of special interest since it seems to be one of the so-called odatrians, a monitor group otherwise considered unique to Australia. DNA-based studies find V. timorensis to be especially close to Mitchell’s water monitor V. mitchelli and the Rusty monitor V. semiremex, with V. scalaris, the Black-headed monitor V. tristis and others as more distant relatives (Ast 2001, Vidal et al. 2012, Pyron et al. 2013). Whatever, it’s deeply nested within the otherwise Australian Odatria.

Map of Wallacean region (with grey regions showing the areas exposed during periods of low sea level present during the Pleistocene), showing Wallace, Weber and Lydekker lines. This is a cropped version of a larger diagram produced by Maximilian Dörrbecker (Chumwa); licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

If this is correct, it means that the Timor monitor belongs to a lineage that dispersed out of Australia and crossed Weber’s Line, but not Wallace’s Line [adjacent image by Maximilian Dörrbecker (Chumwa)]. This is not really a big deal given the strong Australian influence of the fauna in this region anyway, especially given that other monitors – the Komodo dragon V. komodoensis for one – have crossed Weber’s Line too. That’s right: remember that the Komodo dragon belongs to an ancestrally Australasian clade and must have dispersed out of Australia at some point in post-Miocene times (see links below for more on this) (Hocknull et al. 2009). Oh, yes, GIVE UP on the thoroughly wrong idea that Komodo dragons are anachronistic or in any way ancient. They’re a young evolutionary event, as are most living monitors, it seems.


Ast's (2001) varanid phylogeny again, with body size plotted (from Gould & MacFadden 2004). The Komodo dragon is NOT an 'island giant': it was already giant before it moved to Komodo.

Incidentally, large varanid vertebrae from Timor might demonstrate the former presence of the Komodo dragon on the island and show that it used Timor as a ‘stepping stone’ in migrating between Australia and the Lesser Sunda islands (Hooijer 1972, Arida & Böhme 2010). Alternatively, those vertebrae from Timor might be from something new and unnamed (Hocknull et al. 2009).

Anyway, the odatrian radiation seemingly occurred rapidly, and recently (as in, since the Oligocene: Jennings & Pianka 2004, Vidal et al. 2012), in which case members of the Timor monitor lineage presumably dispersed over-water during the Miocene, Pliocene or Pleistocene. So, question: were overwater dispersal events common in monitor history (and do they explain the occurrences of all those populations of prasinoids and so on on satellite islands around New Guinea and Australia?), or were they rare, with satellite island populations instead owing their distribution to the use of Pleistocene landbridges? It’s going to take a lot of work to figure any of this out…

Pointy head and peachy throat

Let’s move away from the odatrians for now. Below, we see a portrait of V. jobiensis, sometimes called the Peachthroat or Peach-throated monitor. Molecular studies indicate that the Peachthroat is a member of the water monitor clade (Ast 2001, Pyron et al. 2013) (Euprepiosaurus, if we use the varanid ‘subgenera’ as clade labels), perhaps closest to the recently recognised Black-backed mangrove monitor V. yuwonoi of the Moluccan Islands (named in 1998) and Blue-tailed monitor V. doreanus of New Guinea (named in 1874 but mostly ignored until 1994, when it was revalidated). Vidal et al. (2012) found V. jobiensis and V. doreanus to be part of a mangrove monitor clade that is separate from the water monitor clade.

Varanus jobiensis in profile, image by Darren Naish.

The Peachthroat is a mid-sized, slender varanid (up to 1.2 m long in total) native to New Guinea and various of the surrounding islands, namely Yapen, Biak, Salawati and Weigeo. It was named in 1932 as a subspecies of Mangrove monitor V. indicus (as were so many other varanid taxa). In 1951, Robert Mertens – the ‘father’ of modern varanid taxonomy – described the new species V. karlschmidti (sometimes called Schmidt’s monitor, and named for Chicago-based herpetologist Karl Schmidt). It later turned out that the type specimen of V. jobiensis is a juvenile of the same taxon as V. karlschmidti, rendering the latter a junior synonym of the former (Böhme 1991).

V. jobiensis has a very angular-looking head; it’s mostly blackish dorsally, with numerous small, light spots arranged in bands, and bluish or turquoise vertical bands of spots are arranged on the tail. Most remarkable is its pinkish, reddish or orange throat, displayed prominently in wild animals and likely serving an important signalling function. It seems to be a forest-dwelling species that takes readily to trees but it’s also been reported foraging along stream edges, apparently for fish or crustaceans. Insects make up the bulk of its diet. The idea has been proposed that V. jobiensis might contain unrecognised diversity and that new taxa will eventually be named for some of the populations currently included within it (Philipp et al. 2004).

Image by Tony Gamble, used with permission.

As usual, my aim in this article was to cover a whole lot more material – in particular I was really hoping to cover the prasinoids, the strongly arboreal, prehensile-tailed tree monitors of New Guinea and the surrounds, a group I’ve written about a long time ago (Naish 1998a, b) and really want to revisit. At least, however, the several species covered here belong to various of the varanid clades that inhabit tropical SE Asia, the Wallacean region and Australasia. It’s a tangled, complex but fascinating story of numerous lineages. More varanids (including those prasinoids) in future. Until then, heed the advice in the adjacent image (kindly provided by Tony Gamble).

Thanks indeed – once again – to Tony Gamble and Stephen Zozaya (who blogs at Saurian Obsessions) for their help in providing images.

For previous articles on varanids and other platynotan lizards, see…

Refs – -

Arida, E. & Böhme, W. 2010. The origin of Varanus: when fossils, morphology, and molecules alone are never enough. Biawak 4 (4), 117-124.

Ast, J. C. 2001. Mitochondrial DNA evidence and evolution in Varanoidea (Squamata). Cladistics 17, 211-226.

Bennett, D. 1994. Dumeril’s monitor lizard (Varanus dumerilii). The Reptilian Magazine 3 (3), 35-37.

- . 2004. Varanus dumerilii. In Pianka, E. R., King, D. R. & King, R. A. (eds) Varanoid Lizards of the World. Indiana University Press (Bloomington & Indianapolis), pp. 172-175.

Böhme, W. 1991. New findings on the hemipenial morphology of monitor lizards and their systematic implications. Mertensiella 2, 42-49.

Collar, D. C., Schulte, J. A., & Losos, J. B. 2011. Evolution of extreme body size disparity in monitor lizards (Varanus). Evolution 65, 2664-2680.

Conrad, J. L., Balcarcel, A. M. & Mehling, C. M. 2012. Earliest example of a giant monitor lizard (Varanus, Varanidae, Squamata). PLoS ONE 7 (8), e41767

Gould, G. C. & MacFadden, B. J. 2004. Gigantism, dwarfism, and Cope’s rule: “nothing in evolution makes sense without a phylogeny”. Bulletin of the American Museum of Natural History 285, 219-237.

Hocknull, S. A., Piper, P. J., van den Bergh, G. D., Due, R. A., Morwood, M. J. & Kurniawan, I. 2009. Dragon’s paradise lost: palaeobiogeography, evolution and extinction of the largest-ever terrestrial lizards (Varanidae). PLoS ONE 4(9): e7241. doi:10.1371/journal.pone.0007241

Hooijer, D. A. 1972. Varanus (Reptilia, Sauria) from the Pleistocene of Timor. Zoologische Mededelingen Museum Leiden 47, 445-447.

Jennings, W. B. & Pianka, E. R. 2004. Tempo and timing of the Australian Varanus radiation. In Pianka, E. R., King, D. R. & King, R. A. (eds) Varanoid Lizards of the World. Indiana University Press (Bloomington & Indianapolis), pp. 77-87.

Krebs, U. 1979. Der Dumeril-Waren (Varanus dumerili), ein spezialisierter Krabbenfresser? Salamandra 15, 146-157.

Montuelle, S. J., Herrel, A., Libourel, P.-A., Daillie, S. & Bels, V. L. 2012a. Prey capture in lizards: differences in head-neck-forelimb coordination. Biological Journal of the Linnean Society 105, 607-622.

- ., Herrel, A., Libourel, P.-A., Daillie, S. & Bels, V. L. 2012b. Flexibility in locomotor–feeding integration during prey capture in varanid lizards: effects of prey size and velocity. The Journal of Experimental Biology 215, 3823-3835.

Naish, D. 1998a. All-new tree monitors – part 1. Mainly About Animals 37, 7-10.

- . 1998b. All-new tree monitors – part 2. Mainly About Animals 38, 5-7.

Patanant, K. C. 2012. Heads you lose, tails you win: notes on a tail-assisted foraging behavior in Varanus (Odatria) kingorum. Biawak 6 (2), 74-77.

Philipp, K. M., Ziegler, T. & Böhme, W. 2004. Varanus jobiensis. In Pianka, E. R., King, D. R. & King, R. A. (eds) Varanoid Lizards of the World. Indiana University Press (Bloomington & Indianapolis), pp. 189-192.

Pyron, R. A., Burbrink, F. T. & Wiens, J. J. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evolutionary Biology 2013, 13:93 doi:10.1186/1471-2148-13-93

Schachner, E. R., Cieri, R. L., Butler, J. P. & Farmer, C. G. 2013. Unidirectional pulmonary airflow patterns in the savannah monitor lizard. Nature doi:10.1038/nature12871

Seymour, R. S., Smith, S. L., White, C. R., Henderson, D. M. & Schwarz-Wings, D. 2013. Blood flow to long bones indicates activity metabolism in mammals, reptiles and dinosaurs. Proceedings of the Royal Society, B doi:10.1098/rspb.2011.0968

Sprackland, R. G. 1993. The taxonomic status of the monitor lizard Varanus dumerilii heteropholis Boulenger, 1892 (Reptilia: Varanidae). The Sarawak Museum Journal 44, 113-121.

- . 1999. A new species of Monitor (Squamata: Varanidae) from Indonesia. Reptile Hobbyist 4 (6), 20-27.

Steel, R. 1996. Living Dragons: A Natural History of the World’s Monitor Lizards. Blandford, London.

Vidal, N., Marin, J., Sassi, J., Battistuzzi, F. U., Donnellan, S., Fitch, A. J., Fry, B. G., Vonk, F. J., Rodriguez de la Vega, R. C., Couloux, A. & Hedges, S. B. 2012. Molecular evidence for an Asian origin of monitor lizards followed by Tertiary dispersals to Africa and Australasia. Biology Letters 8, 853-855.

Vikrant, S. & Verma, B. S. 2013. Monitor lizard bite-induced acute kidney injury – a case report. Renal Failure DOI: 10.3109/0886022X.2013.868223

Welton, L. J., Wood, P. L., Oaks, J. R., Siler, C. D. & Brown, R. M. 2014. Fossil-calibrated phylogeny and historical biogeography of Southeast Asian water monitors (Varanus salvator Complex). Molecular Phylogenetics and Evolution

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Gigantala 8:02 pm 02/12/2014

    Incidently, occuring as recently as it did, is there any validity to claims that monitors systematically replaced terrestrial australian mekosuchines? Especially given the co-existence between monitors and Mekosuchus itself?

    Link to this
  2. 2. imhennessy 10:34 pm 02/12/2014

    The banded tail of the Australian spotted tree monitor got me wondering about monitors’ relationship to iguanas, which got me looking at Wikipedia and using a well known search engine to track down images of cladograms.

    The bad news first: is a bit of a mess, even describing Prognathodon (a mosasaur, I’m told) as a varanoid.

    The good news, though, is that Darren’s cladograms are much favored by Google over those of a certain heretical author who writes on the topics of pterosaurs and reptile evolution.

    I really enjoyed the article (and the WikiHole I dug for myself), and will tentatively conclude that the banding is convergent, most likely camouflage.


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  3. 3. imhennessy 10:54 pm 02/12/2014

    Or, I could look at the tabs of pictures I opened…. And see lots of monitors and iguanas… and both Beaded Lizards and Gila Monsters with banded tails…

    The few skink pictures I found didn’t give me much to go on, and the tails of the Anguinae all seem to short to offer much chance of banding.

    Suffice to say, I should just be asking if it’s been studied.


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  4. 4. John Harshman 12:59 am 02/13/2014

    A bit off the subject, but what’s the current range of thought on the relationships among varanids, snakes, and mosasaurs?

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  5. 5. BonesBehaviours 7:20 am 02/13/2014

    Please explain tail assisted foraging. Is this at all related to old dragon images in which they use their tail in prey capture?

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  6. 6. naishd 7:21 am 02/13/2014

    Looking forward to answering these questions at length (others may well beat me to it, hint hint. There’s lot of interest in global squamate phylogeny these days), but it will be a while before I can get round to them.

    The ‘are mosasaurs close to varanoids’ question is a perennial favourite: there’s some very brief coverage of it in this Tet Zoo article from 2012.

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  7. 7. naishd 7:24 am 02/13/2014

    Tail-assisted foraging: the animals stick their tails into crevices and use the tail to push or guide arthropods out of the crevice and towards the mouth. Biawak is open-access: check out the article yourself here.

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  8. 8. BonesBehaviours 7:26 am 02/13/2014

    If Komodo dragons are not island giants, and there were giant tortoises in South America (and bigger tortoises have larger fat deposits to aid survival when drifting,) are any ectothermic reptiles island giants?

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  9. 9. BonesBehaviours 7:27 am 02/13/2014

    Thanks, Darren. Of course such behaviour reminds us of how we use our fingers.

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  10. 10. Sordes 8:36 am 02/13/2014

    I think it depends on your definition of “giant”. Of course there are various reptiles which evolved unusual big sizes on islands, but only compared to their next relatives and really giant in overall size. There are even more if you count many sadly recently extinct species. Examples of very large island species would be for example the giant Gallotia species of the Canary Islands, which includes froms known from subfossil remains which were more than a metre in length. Other examples would be Macroscincus coctei from the Capverde Islands or Hoplodactylus delcourti from New Zealand. However there are also many cases of island dwarfism. The populations of Meiolania (as it seems, many different species) which populated many islands like New Caledonia at least locally in early historic times, were “only” around the size of medium-sized Galapagos turtles or even smaller, quite in contrast to their giant relatives on Mainland Australia. There are also boids and some other snakes which evolved smaller sizes on islands.

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  11. 11. naishd 9:00 am 02/13/2014

    Briefly (I’ll try and come back to this later), island gigantism is known in many lizards and snakes but – as Markus says – it’s relative and does not necessarily involve ‘true’ ‘giants’. It’s been studied in varanids, by the way – island-endemic forms of various goannas and other monitors are larger, on average, than their mainland relatives. The big, dark Rosenberg’s monitors of Kangaroo Island come to mind.

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  12. 12. Sordes 9:44 am 02/13/2014

    It´s notable that komodo dragons show signs of “island dwarfism”, as they differ in size on different islands, with the smallest komodo dragons on the smallest islands, what seems to be related with prey abundance. Ref:

    Jessop, T. S., Madsen, T., Sumner, J., Rudiharto, H., Phillips, J. A. and Ciofi, C. 2006.
    Maximum body size among insular Komodo dragon populations covaries with large
    prey density. / Oikos 112: 422/429.

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  13. 13. Tayo Bethel 12:05 pm 02/13/2014


    Might that explain how the giant Australianrelative of the Komodo dragon grew so large–higher prey density?

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  14. 14. ectodysplasin 6:28 pm 02/13/2014

    Have to wonder whether V. timorensis and V. jobiensis are really that “obscure.” Both species are widely traded on the exotic pet market and readily bred in captivity.

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  15. 15. naishd 6:42 pm 02/13/2014

    I think we can all agree that ‘obscurity’ is a pretty subjective concept :) I did a straw poll among (non-herp-focused) colleagues and none (n = 5) had heard of these species.

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  16. 16. JoseD 7:32 pm 02/13/2014


    “Thanks, Darren. Of course such behaviour reminds us of how we use our fingers.”

    Varanids do that too ( ).

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  17. 17. naishd 7:44 pm 02/13/2014

    In the Squamozoic, there are the grabwarans. Inspired by…

    Mendyk, R. W. & Horn, H.-G. 2011. Skilled forelimb movements and extractive foraging in the arboreal monitor lizard Varanus beccarii (Doria, 1874). Herpetological Review 42, 343–349.

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  18. 18. Yodelling Cyclist 7:48 pm 02/13/2014

    A few years ago I attended a talk given by a keeper at Chester Zoo, where she commented that their komodo dragons were fairly calm, docile creatures which were fairly relaxed with their keepers, whilst their crocdile tree monitors were hugely aggressive, vicious individuals who would “ambush” (her word, not elaborated on) keepers trying to feed them/clean the cage.

    I love crocodile tree monitors. They may well be the most beautifully evil looking animals I’ve ever seen close up (including great whites and emus). Plus staggering claws.

    How many evolutionary radiations have the varanids enjoyed? I know that Palaeosaniwa, for example, was one of the largest predators in its environment (cue mandatory musing about the K-Pg event, lack of a true squamozoic and why we have had mosasaurs part II – this time we’re here to stay – yet) so were there any other honking great varanid lizards in the paleogene, or were they as badly hit in the K-Pg as, supposedly everything else was? When did we lose varanids from the New World (and Europe)? Are there any indications of any post-Cretaceous marine monitors?

    Too many questions I guess, but would be fascinated by some knowledgeable answers if any of the pros have the time.

    Seriously cool group, excellent post from Darren, and, as ever, still hoping to get the grant to breed niloticus into a mosasaur.

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  19. 19. SciaticPain 8:40 pm 02/13/2014

    All this talk about islands/reptiles reminded me of Socotra, an island off of Yemen in the Indian Ocean. Historical records mention giant lizards, crocodiles and snakes- all of which have since vanished with no known fossil/skeletal record -but does allude to a possible lost fauna dominated by big herpes.

    Given that parthenogenesis has been documented in komodos, this does beg the question in my mind that maybe other monitors might have the ability given monitor richness in South-east Asia and penchant for island hopping,

    Duane Nash

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  20. 20. ectodysplasin 9:33 pm 02/13/2014

    A few years ago I attended a talk given by a keeper at Chester Zoo, where she commented that their komodo dragons were fairly calm, docile creatures which were fairly relaxed with their keepers, whilst their crocdile tree monitors were hugely aggressive, vicious individuals who would “ambush” (her word, not elaborated on) keepers trying to feed them/clean the cage.

    A friend of mine did some herpwork at a zoo for a while and had the same general opinion. Komodos are giant scaly pupy dogs. Croc monitors are the varanid equivalent of Jurassic Park’s velociraptors….they open doors, hide in ambush, and bite zookeepers in the face.

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  21. 21. Yodelling Cyclist 9:36 pm 02/13/2014

    ectodysplasin: Open doors

    Eeeek! Is this comic hyperbole, or are you serious?

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  22. 22. ectodysplasin 9:46 pm 02/13/2014

    also @YC:

    this time we’re here to stay – yet) so were there any other honking great varanid lizards in the paleogene

    There are various large monitors from Africa and the Indian subcontinent throughout the Cenozoic. The obvious taxon is V. sivalensis from the Pliocene of Pakistan, which is approximately V. komodoensis-sized. There are other “large” monitors of ~60cm+ SVL (e.g. V. amnhophilis from the Miocene of Greece) but nothing in the Paleocene or Eocene as far as we currently know. This could, of course, change with better sampling.

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  23. 23. ectodysplasin 9:47 pm 02/13/2014


    Eeeek! Is this comic hyperbole, or are you serious?

    They’re apparently good at getting out of enclosures. So, yes, I’m serious.

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  24. 24. Tayo Bethel 11:59 pm 02/13/2014

    Just how flexible and prehensileare varanid hands and lizard hands in general?

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  25. 25. naishd 3:54 am 02/14/2014

    Thanks for great comments – I think more and more people these days are excited and intrigued by the amazing world of varanids. Keep up with Biawak, the newsletter of the International Varanid Interest Group – it’s OA and all issues are downloadable here – for hot varanid news.

    Some responses to questions. Did Australasian varanids ‘replace’ mekosuchine crocs (comment¬¬ # 1): this has certainly been inferred or suggested, but (so far as I know) there isn’t any work that really supports it. Note that it’s based, in part, on suggestions that mekosuchines like Mekosuchus and Trilophosuchus were vaguely goanna-like in ecology and perhaps capable of climbing – this is controversial and doubted, and perhaps these mekosuchines were more like other crocs (especially Osteolaemus, the African dwarf crocs) in ecology and behaviour. In any case, there is such substantial overlap between mekosuchines and varanids that I’m sceptical of ideas about any sort of replacement. Molecular clocks and fossils indicate that varanids were on Australia from the start of the Miocene at least, whereas mekosuchines persisted to the Pleistocene and perhaps Holocene – even New Caledonia was home to both mekosuchines and varanids until a few thousand years ago, apparently. In other words, there was co-existence of the two for more than 20 million years. Why did mekosuchines decline and die off? I don’t know, but I suspect it was a gradual event linked to the Neogene shift towards drier, more monotonous environments.

    On the relationships between the major lizard groups (comments # 2 and 3): views on the shape of the lizard tree have changed substantially in recent years. Based on anatomical characters, experts have generally preferred the following tree structure: (Iguania + (Gekkota + (Scincomorpha + Anguimorpha))) or something similar, with Iguania obviously including iguanas, agamas and chameleons, and Anguimorpha including alligator lizards, varanids and their relatives. According to this view, iguanas and monitors are thus well apart and any particular similarities (not shared by squamates in general) would be convergences. Molecular studies, however, now suggest a very different tree: (Gekkota + (skinks and cordylids etc + (teiids, lacertids and amphisbaenians + (snakes + (iguanians + anguimorphs))))). According to these results, iguanians and anguimorphs are actually close relatives! However, even within this view, there are lots of iguanian and anguimorph lineages that put distance between iguanas and varanids so, again, they are not that close. Features like bold vertical tail stripes are best interpreted as convergent ones that have evolved independently on numerous occasions within squamates. Hope this helps!

    More answers coming…

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  26. 26. Jerzy v. 3.0. 6:59 am 02/14/2014

    Together with Sivalik giant tortoises, I wonder if giant varaninds of mainland Asia were wiped out by early hominids?

    Before well-established megafauna extinction, there could be an earlier wave of extinction caused by Homo erectus and related hominids. They could wipe out directly giant varanids, tortoises, chalicotheres and cause competitive extinction of saber-toothed cats.

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  27. 27. Jerzy v. 3.0. 7:01 am 02/14/2014

    And why V. macraei and related have so crazy bright colors?

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  28. 28. Heteromeles 10:23 am 02/14/2014

    @26: Jerzy, is there evidence of a megafaunal extinction associated with any Homo taxa other than Homo sapiens sapiens? I didn’t know that was the case.

    I’ve semi-joked before that you can trace the line of megafaunal extinction as the range of Homo erectus/antecessor/et al. The idea is that our ancestors hunted in a low-impact enough way that animals in the habitats they invaded were able to coevolve with them and their gradually improving hunting techniques over about 100,000 years, rather than going extinct over 10,000 years or less. After all, until the last 3,000 or even 300 years, southern Asia had quite a diverse megafauna, on par with Africa. It’s when you get into northern Eurasia, Australia, and the Americas (outside the known range of H. erectus and its confreres) that you start seeing major megafaunal extinctions.

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  29. 29. Halbred 12:43 pm 02/14/2014

    Hold up, time out.

    Chameleons are iguanians? I guess I’d never thought about it.

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  30. 30. Jurassosaurus 1:10 pm 02/14/2014


    Yep. They are typically grouped as sister taxa to agamids. The resemblance is pretty prevalent when you look at their faces.

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  31. 31. vdinets 2:03 pm 02/14/2014

    For any large taxon, you can usually find examples of both island gigantism and island dwarfism. Think bee hummingbird, island scrub-jay, pygmy elephants, beach vole, etc.

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  32. 32. Zoovolunteer 2:43 pm 02/14/2014

    Re varanids using their hands – at Bristol Zoo they have designed an enrichment device for their V.prasinus consisting of a drilled log hanging vertically from a wire with holes that contain food items. The monitors have to jump onto the log and hang on while reaching in to dig out the treats (usually wax worms, pinkies or the like. They only get it ocaisionaly so they do not get bored, but it is a major activity boost for them. Unfortunately captive reptiles all too often do not get the same level of care for their mental health as endothermic animals do, but monitors and crocodilians would certainly benefit from this kind of stimulation.

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  33. 33. LeeB 1 4:35 pm 02/14/2014

    It has been suggested that earlier hominids were responsible for the extinction of giant tortoises in Africa; they occur in Africa in the Miocene and Pliocene and then die out whereas they continue to occur in Madagascar which presumably had a similar climate.
    You could also wonder if they were responsible for some of the earlier Pleistocene extinctions in Africa such as giant Theropithecus baboons and very large open country pigs in the genera Metridiochoerus and Kolpochoerus.
    If the pigs dug burrows like the living warthogs they may have been vulnerable to being dug or smoked out of their burrows.


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  34. 34. naishd 6:51 pm 02/14/2014

    I post on behalf of a frustrated David Marjanović, currently unable to login to SciAm…

    Anyway, questions in the comments:

    “When did we lose varanids from the New World (and Europe)?”

    Their disappearance from Europe can be entirely blamed on the climate; they were still present in eastern Austria (Pannonian plain) 8 Ma ago.

    “Are there any indications of any post-Cretaceous marine monitors?”

    I don’t know any, do you?

    Also, molecular trees don’t always find iguanians and anguimorphs as sister-groups; at least as often it’s snakes + iguanians, and the internodes between all three are always scarily short. I don’t think any purely molecular analysis has yet found snakes + anguimorphs, but I think that’s going to happen at some point.

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  35. 35. BilBy 7:04 pm 02/14/2014

    @LeeB1 – do you have a reference for human-induced giant tortoise extinction in Africa please?
    Warthogs don’t dig burrows, only improve existing ones, dug by other beasts – aardvarks dig deep and occasionally complex burrows.

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  36. 36. LeeB 1 7:38 pm 02/14/2014

    Bilby, have a look at the book Palaeontology and Geology of Laetoli:Human evolution in context:volume 2; Fossil hominins and the associated fauna; chapter 17 is on tortoises.
    This chapter is available on line with only the occasional missing page.
    It suggests the late Pliocene extinction of giant tortoises was possibly associated with the appearance of early hominins and stone tool using behaviours at 2.6 MYA.

    This seems plausible because giant tortoises would be vulnerable to having their shells smashed open by stone tools.
    Certainly as humans spread to other continents the giant tortoises all rapidly became extinct.

    And even if warthogs don’t dig their own burrows they regularly occupy them; and giant pigs in large burrows would be easy for early hominids to gain access to.


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  37. 37. LeeB 1 10:05 pm 02/14/2014

    The second half of this:
    also discusses the role of hominids in killing giant tortoises starting in Africa and working forwards from there as they spread around the world.


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  38. 38. BilBy 5:00 am 02/15/2014

    Thanks LeeB 1. I was under the impression that Africa was still seen as the ‘happy anomaly’ in that humans had little influence on extinctions e.g. J.T. Faith(2014)Earth-Science Reviews 128 105–121. No mention of tortoises in that paper though.

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  39. 39. Jerzy v. 3.0. 6:40 am 02/15/2014

    I also wonder about chalicotheres.

    All these extinct animals have in common a character which I call “monsterness”. They are big and build compact with short legs, unable to run at speed, but relying on passive or active defense. This is effective against other animals, but was powerless against hominids which developed weapons allowing attack from distance. Even as simple as sharp stones, wooden spears and fire. Extinctions are disproportionately biased towards compact animals. Animals which survived are different: mostly thin, longer-legged, and able to outrun humans.

    Curiously, the same general shape is seen by fantastic creatures in traditional horror films. They are always huge, lumbering, massive and armoured. Maybe human subconsiousness still keeps a special interest in such creatures? “Godzilla” is essentially a replay of how early hominids would view an encounter with giant pig, tortoise or varanid.

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  40. 40. LeeB 1 4:25 pm 02/15/2014

    that is a good paper for demonstrating the magnitude of late pleistocene extinctions in Africa.
    However whenever people suggest that there has been a climate change leading to a loss of grassland (or in other areas steppe tundra)and a replacement with bush or forest and that this led to the extinction of animals I am always inclined to remember that the removal of large animals from grasslands leads to the grasslands being colonised by shrubs and trees.
    The animals keep the trees and shrubs out by grazing or trampling them; in the case of very large mammals they push over trees to get access to their leaves or bark.

    You don’t even have to make the animals extinct to do this; just severely limiting their number will do.
    Changes to the vegetation in yellowstone national park when wolves were hunted out and deer populations exploded and the reverse changes when wolves were reintroduced and deer populations decreased again show this.

    And severely hunting the largest megafauna which have the greatest effect on the vegetation leads to changes in the plants which then effect the numbers and distribution of smaller animals which then further affects the vegetation cover in a cascading effect.

    So I am sceptical of studies which link climate change to extinction where the climate change is measured by vegetation changes that mimic those produced by crashing the numbers of animals present.

    And the paper’s noting that in Africa there had been a series of earlier extinctions throughout the Pleistocene is correct; I just wonder if the earlier extinctions had been of animals that were more susceptible to hunting or competition with hominids.

    The difference between Pleistocene and pre-Pleistocene extinctions is that the latter did not result in a loss of megaherbivore diversity; species were replaced by other species in similar niches, whereas late Pleistocene extinctions were of species that were not replaced resulting in the depauperate faunas we have today.
    What this paper does show well is that even the modern African faunas of a few hundred years ago were depauperate compared to those of the late Pleistocene.


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  41. 41. Assama 4:37 pm 02/15/2014

    Dear all,

    My first comment on that wonderful blog that I have been reading for years (many thanks to Darren for the nice reading materials).

    Kolpochoerus and Metridiochoerus are not really extinct as the extant genera Hylochoerus and Phacochoerus are derived respectively derived from the latter genera. Only some of their species are extinct, and interestingly for this discussion, mostly the biggest ones (notably K. olduvaiensis, K. paiceae, K. majus and M. compactus that were probably not good at avoiding our fellow ancestors.

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  42. 42. Assama 4:40 pm 02/15/2014

    Sorry for the formatting mistake (I tried).

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  43. 43. Heteromeles 5:05 pm 02/15/2014

    @LeeB: I get the point you’re making, but I’d caution that we’ve got to be even more careful than that.

    One big example is fire. If we’re going to posit that Homo erectus grade hominids hunted with fire, then we’ve got them transforming the landscape in a way that looks a lot like what browsers do–with tell-tale ash instead of dung, of course. If instead we’re going to talk about cryptic hominid hunting that preferentially takes out the biggest species and leaves the smallest behind, then we’re saying a lot about their toolkit and prey preferences, and what we’re saying doesn’t exactly make sense. Specialist elephant hunters? Really? Even today, there are a lot more human rabbit hunters than elephant hunters, and most rabbits aren’t threatened with extinction or extinct.

    The upshot is that I think we’re still not thinking it through completely, although I don’t have a good answer. So far as I know, the evidence suggests that, when let loose on a continent and equipped with stone tools, Homo sapiens sapiens takes 5,000-10,000 years to get eliminate the “monster” megafauna. This is what happened in both Australia and the Americas, and it was just argued in Kolbert’s The Sixth Extinction that it’s what we did to Neanderthals.

    In terms of extirpation, this is an extremely slow process. Heck, today most conservation programs would be *glad* if they could be guaranteed of keeping a large mammal species from going extinct for the next 5,000 years.

    The upshot is that if we’re the baby-faced killers we’re claimed to be, we’re not very good at it. I’m not saying we’re guiltless in megafaunal extinctions, but I do think we’re missing quite so critical part of the explanation. Do we really believe that one or two mammoth kills per lifetime would be enough to doom a species? Perhaps we rarely killed them directly, but we did something else, like appropriating their resources and depriving them of habitat, that caused their decline and ultimate extinction.

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  44. 44. LeeB 1 5:38 pm 02/15/2014

    Interesting isn’t it.

    Whatever we did, when we turn up on a continent the megafauna are on borrowed time.

    We hunt at a distance, we light fires, we add the ecology of fear to large mammals that previously were more or less immune to predation as adults, we lower the amount of available mid size prey so predation pressure of other carnivores is increased on the remaining prey animals, we do wildly crazy things like hunting huge dangerous animals just to show off and gain status even when the big animals have become rare and we have to really go out of our way to find them; we can predict where they may occur and can follow their trails so we can find them even when they are rare.
    Basically we disrupt the environment in so many ways.
    And the presence of large mammals on offshore islands when they have completely disappeared across entire continents and the only difference is that we were on the continents and not on the islands shows that we are the responsible agent.

    The other really fascinating thing though is looking at just how diverse the megafauna was across the world before the Pleistocene extinctions began; the Pleistocene is really the only period where you can look at this diversity on a global scale and try to look for patterns.


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  45. 45. BrianL 5:59 am 02/16/2014

    The megafauna of the late Pleistocene seems well-documented, but I do wonder if there are areas out there about which their megafauna we know but very little? The only ones that readily come to mind for me are New Guinea and the Lesser Antilles. For the latter, the presence of *Amblyrhiza* (is it Pleistocene though?) plus the rich megafauna of the Greater Antilles suggest surprises may be lurking there. Perhaps western Africa too? The Sahara region? Am I overlooking any other area? What do we know and what can we infer about the megafauna of these regions?

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  46. 46. Heteromeles 10:21 am 02/16/2014

    @LeeB: Yeah, all that high efficiency hunting stuff. So why did it apparently take thousands of years for modern humans to kill everything that couldn’t run away from us? Why not centuries? That’s the part I don’t get.

    Later in archeological history, there’s good records of, IIRC, Indians on Catalina permanently overfishing an abalone population and shifted to other fish and shellfish, and it didn’t take very long–a century or two, again IIRC. Granted the Americas are continents and Catalina’s a small island, but people reached Chile (Monteverde site) within about 3,000 years of crossing Beringia. If it’s a matter of people entering an area and killing off the megafauna within a century or two, then aren’t we looking at a 3,000 year extinction event, not a 5,000-10,000 year event? That’s a non-trivial time gap, too. Two thousand years ago was the height of the Roman empire, 80-100 generations, and 7,000 years ago was about the time the Black Sea reflooded. A lot should have changed in that time, and yet it didn’t.

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  47. 47. Tayo Bethel 3:01 pm 02/16/2014

    I’m of the opinion that implicating early hominidsin the extinction of all megafauna is a bit of a mistake. Or at least, citing them as the direct cause is a mistake. Hunting very large animals is very dangerous even today–ask any big game hunter. So why would a family group of, say, Homoe rectus go after mammoth herds consistently enough to cause extinction? Alien diseases seem to be a far more likely candidatefor suchmassive die-offs, possibly carried not only by humans but by other African immigrants as well.

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  48. 48. LeeB 1 4:04 pm 02/16/2014

    BrianL, the northern quarter of Australia where they have just described Kukaodonta robusta, the thibetan plateau and the ethiopian highlands are areas that have not had much study of late Pleistocene faunas.
    Also the tropical north of the South American continent is just starting to get intensive study with the Venezuelan tar pits beginning to be looked at.
    And there are still offshore islands like Socotra which are probably going to prove interesting when studied palaeontologically.

    Heteromeles, I suspect that the extinction at any one location may be on the order of a century or less to crash the megafauna population, and a couple more centuries to find and destroy the remnant animals.
    But on a continental scale the first people could go anywhere and probably colonised the environments with the most prey and that were the easiest for them to move around in, and just moved on when prey became scarce.
    They must have eaten really well.
    Extreme high altitudes, semideserts and thickly forested areas were probably entered later as population pressures grew.
    But I am not sure that any extinction event took 5000 years or so; there may be problems with the dating of sites.

    Tayo Bethal, of course big game hunting is dangerous, yet not only modern humans but some of our related species definitely did engage in it.
    And the danger of modern african and south asian large mammals may be because they have got used to humans as predators; they are the survivers.
    Naive large mammals on other continents may not have recognised us as predators and may have been curious about us rather than aggressive to us.
    And being able to kill large relatively slow prey from a distance in open country definitely gave us an edge.

    I have problems with a hyperdisease killing everything; the diversity of megafauna was too great for a single disease, including marsupials, edentates, south american ungulates, proboscidians, and large flightless birds.
    The idea of human hunting and destruction of the habitat by fire seems to work better for me because these are activities we know that humans engaged in.
    And humans do seem to have a habit of overhunting when they enter a new habitat.

    I’m from New Zealand and this just seems obvious from here given the local history as new groups of people arrive; history repeats itself.


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  49. 49. Heteromeles 6:26 pm 02/16/2014

    @LeeB: That makes sense, that your model is the global moa hunt.

    I’m not quite so sure, because little evidence for the deep time paleoindiansin the Americas suggested that they moved pretty quickly and spread throughout the Americas before the mass extinction started. For example, they genotyped the skeleton of a Clovis child from western Montana. The interesting thing is that the skeleton is closer genetically to Central and South American Indians than it is to those Indians currently living in the area.

    There’s also at least some archeological evidence that Siberian mammoth hunters didn’t kill a lot of mammoths, and when they did, they were mostly going after the ivory for tool use.

    P. Nikolskiy and V. Pitulko. Evidence from the Yana Paleolithic site, Arctic Siberia, yields clues to the riddle of mammoth hunting. Journal of Archaeological Science. Published online June 5, 2013. doi:10.1016/j.jas.2013.05.020.

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  50. 50. vdinets 11:56 pm 02/16/2014

    A common flaw in studies of ancient mammoth hunting is that the absence of mammoth bones at archaeological sites is interpreted as the evidence of lack of hunting. But in reality mammoth bones are simply too heavy to carry home from the kill site. It is reasonable to assume that mammoths were butchered where killed, and only meat was carried back.

    There are, of course, exceptions: one culture in Eastern Europe built entire houses of mammoth bones.

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  51. 51. Jerzy v. 3.0. 5:06 am 02/17/2014

    There is literally only a handful of Pleistocene specimens known from the whole New Guinea. Who knows what fascinating fauna lived there during the Pleistocene?

    Highlands of SE Asia may be another understudied region, there are many living species with limited range today.

    There are simulations, that wiping out megafauna did not need intensive hunting, see eg.
    Alroy J. A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction. Science. 2001 Jun 8;292(5523):1893-6.

    Which is similar to the modern situation. Brown bear, wisent, aurochs, moose and beaver were wiped out in most of Europe, although they were marginal game and did not leave very numerous archeological finds directly pointing to hunting. At the same time, some more intensively hunted species survived, like red deer, roe deer and hare. I guess paleontologist in 10,000 time would argue that mammal extinction in industrial Europe was not caused by man.

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  52. 52. Chabier G. 5:46 am 02/17/2014

    Megafaunal extinctions should be caused not only by overhunting, but also by general changes in the environment, now we know ancient hunter-gatherers were not passive Nature users as previously thought. Australian Aborigines and Native Americans really changed vegetation, by means of an extensive use of fire,in order to favourish useful plants or favourite game animals. The way of life of the Timbisha Shoshone in the Death Valley is paradigmatic. Many species could be affected by habitat change, even having never been hunted, and biggest, low ratio breeders, should be the most sensible.

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  53. 53. John Scanlon FCD 11:58 am 02/17/2014

    LeeB 1, I was thinking “What is this Kukaodonta robusta of which one speaks?” so looked it up: Brian Mackness’s 2010 new genus (Alcheringa 34:455-469) for a long- but poorly-known former Euowenia species, originally described by Devis.
    Also wondered about the etymology of the generic name… Oh dear: “a combination of the Greek ‘kukaos’, meaning circle,
    and ‘donta’, meaning tooth, [...] given to denote the characteristic sub-circular P3 of this genus.” Apart from the grammatically dodgy ending, somebody misread lambda as ‘A’. I suspect OCR may have been involved.
    It’s not now possible to point out the error to Mackness, who died very recently, with a PhD thesis unsubmitted but said to be nearly finished. [Creepy, creepy man. Raping children is bad.]

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  54. 54. LeeB 1 4:22 pm 02/17/2014


    I didn’t know anything about him.
    He does sound like very bad news.
    And the name is stuffed up.

    Regarding the species, it’s distribution is interesting being found on both the east and west sides of Australia at the northern margins of where Pleistocene fossils have been found in Australia.
    It looks like it occurred in the tropical north of Australia; it would be interesting to know what else occurred with it.
    Diprotodon did, because it has been found in the far north of West Australia.
    It would be interesting to know if any Sthenurine kangaroos occurred up there, if they did they are probably going to be new species.
    Likewise did Palorchestes or any other of the megafauna.
    We need some good Pleistocene faunas described from Cape York Peninsula, Arnhemland and the Kimberleys.


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