World’s smallest reptile (and amniote) described: a VERY tiny chameleon

January 29, 2021 • 9:15 am

A new paper in Scientific Reports, which you can access below, describes the world’s smallest known reptile, a miniscule chameleon found in a small area of Madagascar, and named Brookesia nana. Indeed, it’s the smallest of all known amniotes, a group that includes reptiles, birds, and mammals. Two individuals of this species these were caught in 2012—a male and a female—and were just described as members of the new species.

First, a photo, just to show you how small it is. Below is an adult male, the “holotype” specimen (the one preserved individual used to characterize and represent the entire species). It sits comfortably atop a fingertip.

Photo by Frank Glaw, the paper’s first author

The size of this bad boy: its snout-to-vent length is 13.5 mm (0.53 inches!), and total length including the tail is 21.6 mm (0.85 inches). It’s about half an inch long: get out a ruler to see how small that really is! The female specimen, captured around the same time, is a bit bigger: 19.2 mm snout-vent length and 28.9 mm total (0.76 inches and 1.13 inches, respectively).  Here are a few more pictures of both specimens (sadly, they killed both individuals to preserve them):

Caption from paper: Brookesia nana sp. nov. in life. (A–C) male holotype (ZSM 1660/2012). (D, E) female paratype (UADBA-R/FGZC 3752).

Click on the screenshot below to see the paper, or get the pdf here. The full reference is at the bottom, and there’s a short popular precis at IFL Science.

The species resides in a group (“clade”) of other miniature chameleons in the genus, with none longer than 30 mm total. The species name nana comes from the same Greek-Latin root that gives us “nano”, meaning “small.” The authors also did DNA analysis to place the species within its group, but we needn’t go into that, as the results are useful only to herpetologists.

The interesting thing about this species, as well as its relatives, is that they’re tiny and also extremely geographically restricted. They’re all found in montane (“mountainous”) rainforest. Here’s a distribution map of the related species in Madagascar, and you can see that no species was found outside of a range of about 100 km (60 miles). B. nana (yellow star) was found in only one place, and there may be very few individuals in the species. Most of the species are likely to be endangered: the authors note that the habitat of B. nana (now in a supposedly “protected area”) is being nibbled away by human depredation through slash-and-burn agriculture. If these things can breed in captivity, they might get a few in, for Madagascar is known for the loss of endemic species due to human disturbance.

(From paper): Map of northern Madagascar, showing the distribution of species of the subgenus Evoluticauda (known as Brookesia minima group) in this region (only showing records verified by molecular data5,10,14). Note that B. dentata, B. exarmata, and B. ramanantsoai occur further south and are not included in the map. Orange (dry forest) and green (rainforest) show remaining primary vegetation in 2003–2006.

All of the relatives of B. nana have females that are larger than the males, which is unusual for reptiles.  B. nana, like its relatives, is an insect eater, and is probably arboreal (lives in trees), though the latter isn’t clear from the paper, for collecting information isn’t detailed.

A few other features of this group deserve mention. Unlike many chameleons, they lack head ornaments and spines or tubercules on their backs.  Why? We don’t know.  We also have no idea why individuals are so small, as their habitats don’t seem to particularly favor the evolution of miniaturization. It’s possible, but unlikely, that the two individuals they found happen to be extraordinarily small specimens, and not close to the species average. However, that would be a remarkable coincidence since they were found several days apart and were both sexually mature.

[Addendum by GCM: Brookesia nana may not be the world’s smallest lizard species, although it’s at least close. Reptiles have fairly indeterminate growth, so with a sample size of one of each sex, it’s hard to know what the maximum size is. I know a gecko species from the British Virgin Islands that has a maximum snout-vent length of 16 mm in males and 18 mm in females; I don’t know the species’ minimum size at sexual maturity. Body size in lizards is often reported as the maximum size known, which of course has problems as a statistic because it’s dependent on the outliers. To overcome this, Tom Schoener, in his studies of body size evolution and ecology of West Indian anoles, used to report the mean of the largest third of the sample as his body size statistic. With a sample of 1 per sex, this can’t yet be usefully done for the new species.]

One trait that may be comprehensible is the relatively large genitals of male B. nana. Like all lizards and snakes, males have a “hemipenis”, or bifurcated penis. Individuals mate by using only one of the two sides in each mating, alternating between matings. Because the female of this species is larger than the male by a substantial amount, nearly 50% (again, we don’t know why this disparity exists), the male has to have a relatively longer equipment to transfer sperm to the female.   Here’s the male with the right hemipenis sticking out:

And closeups of the extruded left hemipenis, which is itself bifurcated. So we have the tiniest reptile known, one smaller than any other amniote, but also a well-endowed one. It’s ineffably cute (blunt snout, big eyes—all the traits that appeal to humans in baby animals), but also endangered. Right now we know very little about its ecology and behavior, though we know where it sits phylogenetically within its group of relatives. And we may not know a lot more before the species goes extinct.

h/t: Ursula, Greg

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Glaw, F., Köhler, J., Hawlitschek, O. et al. 2021. Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons. Sci Rep 11, 2522. https://doi.org/10.1038/s41598-020-80955-1

22 thoughts on “World’s smallest reptile (and amniote) described: a VERY tiny chameleon

  1. Well, that is pretty cool. One worries about their habitat though.
    I thought it not unusual for females to be larger than males, when it comes to reptiles. Larger size of females being an adaptation for being able to put resources into eggs.

    1. It’s not unusual for females to be larger than males, probably for the reason you cite. But equally (?) it’s not unusual for males to be larger than females, particularly where males indulge in interpersonal violence to compete for access to the females. Examples – pretty much any domesticated animal that I can think of.
      The relatively unusual state is that of humans, where males and females are of approximately the same size – give or take 20% differences.

      1. In reptiles, it really depends upon the taxon. In the group that I work on (Phrynosoma), for instance, females are all larger, but in a sister taxon (Sceloporus) it’s the males. Seems to depend upon whether fecundity selection predominates or not – or, as you point out, if there is male-male intrasexual selection (i.e. Anolis).

  2. Is this the formal publication of the ultra-miniature Malagasy chameleon which appeared, fingertip mounted, in an Attenborough documentary a couple of years ago?

    1. No, that was a different species. Attenborough showed either B. minima or B. tuberculata (I’m not sure), both of which are substantially larger than B. nana.

  3. And closeups of the extruded left hemipenis, which is itself bifurcated.

    I’m assuming that the bulbous mass at the root of hemipenis is not the testis, since most “reptiles” I’ve made any study of mount their testes internally. Being “cold-blooded” (well, endothermic – body temperature managed by manipulation of their environment), they don’t have the need for ventilation and cooling which ectothermic (“warm-blooded”) organisms often have.
    Pesky dinosaurs, throwing a spanner into the workings of that piece of theory.

    1. Didn’t you cross endo- and ectothermic definitions? In greek, Endo means internal, and ecto means external.

  4. “…sadly, they killed both individuals to preserve them” – what the [bleep]! This reminds me of a school trip to the Bishop Museum in elementary school. The guide showed us a stuffed yellow bird that was the last of its kind ever seen in the wild – and they killed it in order to study it and confirm that it was what they thought it was and it was the last ever seen EVER! I wanted to scream, but I was a very well-behaved child and just stared darts at him. (I guess it wasn’t his fault; just being the bearer of bad news.) Sigh.

    1. I still run into that today with endangered insects and professional researchers who still feel it their right to collect voucher specimens for their collection. I’;ve wished to throttle some on occasion.
      Of course decades ago, the culture was quite callous about this thing. There is the classic tale of the Northern elephant seal, which was hunted very close to extinction for oil. It was thought to be extinct, in fact, but in the 1800s a small isolated population was discovered on an island. A museum expedition was immediately dispatched to collect several specimens, with the understanding that since these were the last of their kind one better collect some before they were all gone!
      Fortunately, they hung on and later became protected. Now they have rebounded in numbers.

      1. The classic example of this sort of thing is the Great Auk – the last survivors were all, as far as I know, killed for museum collections. Museums were setting high prices for specimens by this point, which accelerated the process.

    2. I had the same reaction. And then I wondered if it was “stuffed” and if so, amazed at the taxidermist’s skill. I don’t know if there are other ways of preserving that is easier for such a small animal, but it didn’t seem to have the look of a specimen that resided in a bottle of formaldehyde.

    3. I know. I would hope that, in the modern world, they could at least get DNA from the creatures and perhaps digitally store the genome so that, in the fullness of time, perhaps some much more benign (and plausible) Jurassic Park type scenario might be carried out.

  5. I actually caught a Brookesia during the daytime on my Madagascar trip – was very proud of myself, they’re hard to find. Can’t remember the species and my field notes aren’t accessible right now – not B. nana, though. The guide took us out jacklighting at night for them, when you can find them sleeping on branches above the leaf litter, but even then, they’e difficult to see – we only caught one that night.

  6. From dinosaurs to this…the marvels of size differentiation that evolution creates hurts the brain. Thanks for this interesting post of a most astonishing and adorable chameleon.

  7. What a cute little guy! Why are these tiny ones so cute so often?
    Although this is the smallest amniote indeed, there are even smaller vertebrates.
    I think the smallest vertebrate is the tiny frog Paedophryne amauensis, also impossibly cute.
    https://www.amphibianfact.com/wp-content/uploads/2019/05/Paedophryne-Amauensis-Pictures.jpg
    I regularly see tiny geckos of comparable size here, but I guess they are babies though, and are bigger when adult.

    1. The couple who lived in my little house before me in Palo Alto in the 70s had two iguanas. One day they were found under the broiler with some chicken. They survived, with a little loss of back skin.

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