Tetrapod Zoology

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Regular readers will know that I like covering obscure animals… with luck, really obscure animals. The problem with such animals is that nice images hardly ever – sometimes never – exist. When they do exist, they’re protected by copyright and are unavailable for use on a blog. I’m therefore eternally grateful when people are able (and kind enough) to send me photos of an obscure animal, and are able to give me permission to use them. Recently, herpetologist Kate Jackson of Whitman College, Washington, was kind enough to provide the photos you see here. Oh. My. God.

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It’s Bothrolycus ater: an extremely obscure African snake that (ahem, drumroll) may never have been photographed live before. Yes, this could well be a world first.

One of the first books I always check when wanting to know more about obscure snakes is Chris Mattison’s The Encyclopedia of Snakes (Mattison 1998). Of this taxon, he states “A small snake about which almost nothing appears to be known” (p. 211). That’s it. Not encouraging. Incidentally, I discovered a few weeks ago that Chris Mattison used to live about five minutes away from my house here in Southampton. Anyway… after a bit of research I discovered that – despite its obscure status – Bothrolycus really isn’t that poorly known, and in fact it certainly should be better known that it is. Why? Read on.

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A few sources reveal that the name ‘Günther’s black snake’ is sometimes used for this species. Named by Albert Günther in 1874, it’s from central Africa: its range certainly includes Cameroon, Gabon, Equatorial Guinea and Republic of Congo (Trape 1985, Lasso et al. 2002, Pauwels et al. 2006); Günther (1874) originally described it from Cameroon. The individual you see in the photos here was encountered by Kate in the Republic of Congo this year (in an area about to be strip-mined for iron ore) [adjacent image, by G. H. Ford, is from Günther's initial description. The chameleons are members of the taxon Brookesia. They shouldn't be there Rhampholeon]. Said by some authors (notably Georges Boulenger) to be semi-aquatic (I really don’t know if this is accurate), it’s an inhabitant of montane and sub-montane forest, and some studies indicate that it may be moderately common in some places. It’s smooth-scaled (Moore & Jackson 2010) and can reach just over 41 cm. In adults, the blackish head is flecked with white, but in juveniles the top of the head and nape is cream-coloured (Loveridge 1936).

Notable sexual dimorphism

I was surprised to learn that Bothrolycus has sometimes been cited as one of the only snakes where sexual dimorphism is obvious: Schmidt (1923) regarded the difference in size between the sexes as being “unusually pronounced” and “quite exceptional” while Davis (1936) noted that it was (to his knowledge) the only snake where males and females consistently exhibit different scale counts: the former exhibiting 17 and the latter 19 on the “anterior part of the body”. Boulenger (1919) was the first author to bring attention to this presence of obvious dimorphism.

So far as I can tell from the literature, at least one snake originally described as a distinct species – Pseudoboodon albopunctatus Anderson, 1901 – later turned out to be the same thing as Bothrolycus. This wasn’t realised initially as the holotype of P. albopunctatus represented the different sex from the B. ater holotype (I’m not 100% sure about this: please let me know if you know otherwise) [image of P. albopunctatus holotype below, from Anderson (1901). Compare it with the images of B. ater: note the pale spots on the labial scales and the pit in front of the eye]. Anyway, since these early studies were published, sexual dimorphism in snakes has become better known, and is now understood to be quite widespread (in body size, mass and relative head size, for example: Shine (1991)).

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Nevertheless, given the apparently distinct – and historically significant (if you like) – sexual dimorphism of Bothrolycus, I’m really surprised that it’s as obscure and little-mentioned as it is.

Good riddance to the bloated monster that is ‘Colubridae’ of tradition

What sort of snake is Bothrolycus? Dowling (1969), McDowell (1987), Lawson et al. (2005) and Zaher (2009) listed this taxon as part of the colubrid clade Boodontinae (also spelt Boaedontinae by some authors). It was included among the boodontines because its hemipenial morphology is pretty similar to that of other taxa included in this group: the organs are slightly bilobed with centrolineal, bifurcating sulci spermatici and longitudinal rows of medium-sized spines that are usually connected by wavy, spinulate ridges (Zaher 1999). Yes, to be an expert on snake phylogeny and diversity, you have to be intimately familiar with male snake genitalia. And that’s not such a bad thing; these paired organs (termed hemipenes; singular = hemipenis) really are neat (by which I mean: weird, fascinating and even beautiful… in a not-at-all-erotic kind of way).

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An alternative position for Bothrolycus was supported by both Zaher et al. (2009) and Kelly et al. (2009). In two, independent analyses of the enormous group of caenophidian snakes that includes the viperids, elapids, the ‘colubrids’ of tradition and all of their relatives, both sets of authors recognised numerous new or ‘new’ ‘family’ level clades and proposed new taxonomies. Among the ‘new’ groups that both teams recognised is Lamprophiidae, a group diagnosed by hemipenial characters* and regarded (due to molecular data) as part of Elapoidea, a group first named by Pinou et al. (2004) for the Atractaspis + Elapidae clade (Atractaspis includes the burrowing asps or mole vipers, previously covered on Tet Zoo here). Bothrolycus wasn’t included in either molecular analysis (obviously, there isn’t that much material of it kicking around for analysis), but both teams listed it as a lamprophiid [the adjacent simplified phylogeny, which roughly reflects the phylogeny recovered by Zaher et al. (2009), depicts the sister-clades Elapoidea (shown containing only Elapidae and Lamprophiidae) and Colubroidea (shown containing Natricidae, Colubridae, Pseudoxenodontidae and Dipsadidae) as the youngest major clades].

* Specifically “Sulcus spermaticus centrifugal and dividing on the mid-region of the hemipenial body” (p. 137). Kelly et al. (2009) used the term ‘African nocturnal snakes’ for lamprophiids.

As well as Atractaspis and elapids, Lawson et al. (2005) included the groups Psammophiidae and Lamprophiidae within Elapoidea, and this was supported by Kelly et al. (2009) and Zaher et al. (2009). Lamprophiidae seems to consist of two clades – Lamprophiinae and Pseudoxyrhophiinae – but, because the pseudoxyrhophiines might actually be closer to psammophiids than to lamprophiines, there are doubts over the monophyly of Lamprophiidae. Within lamprophiids, Bothrolycus might be a lamprophiine (Zaher et al. 2009).

As you might have noticed, discussing these groups is difficult because the names – and the taxa concerned – are, shall we say, somewhat obscure, and ideally you’d need to introduce the animals before discussing their possible positions within phylogeny. And, sorry, but I ain’t doing that right now (I will do it, happily, providing I can get images). Hopefully you’ll get something out of this and be as happy as I am that all those snakes previously lumped together in ‘Colubridae’ are getting sorted out.

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Actually… one other point on this subject. Many of the ‘new’ names used in this discussion (as in, Psammophiidae, Lamprophiidae and Pseudoxyrhophiinae) are not new* at all (hence the scare quotes), but became unfamiliar to non-specialists after they were unceremoniously absorbed into Colubridae sensu lato during the Great Lumping Phase of the 1970s. Lamprophiidae, for example, was published in 1843 (as Lamprophes), Psammophiidae in 1845, and Pseudoxyrhophiinae in 1975. In a way, the recognition of a massively inclusive but virtually undefined Colubridae was lazy and damaging, but I’m sure that those who supported it (the likes of Dowling & Duellman (1978)) regarded it as a tidy solution to a more messy alternative (e.g,, the ‘multi-family’ taxonomy proposed by Underwood (1967)). And, by the way, these snakes aren’t necessarily obscure if you live in Europe: the Montpellier snakes (Malpolon) – familiar to anyone who knows the European herpetofauna – are part of Psammophiidae [adjacent image of Malpolon monspessulanus by Jeroen Speybroeck, from wikipedia].

* Though some are. Kelly et al. (2009) proposed the new elapoid clade Prosymnidae.

The big deal about Bothrolycus

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One thing makes Bothrolycus a particularly weird snake, and it’s not its sexual dimorphism or position within phylogeny. It’s the presence of unusual openings on the side of the face, located just in front of the eyes and referred to by Anderson (1901) as elongate deep loreal pits. You should be able to make them out in Kate’s photos [adjacent closeup © K. Jackson]. If you know snakes, you’ll doubtless be thinking of the facial pits well known for being present in vipers, pythons and boas (they were mentioned recently in the article on the Inside Nature’s Giants python episode). These pits house thermoreceptors, and allow the snakes the detect heat sources (typically, warm-bodied prey animals).

So – do the pits in Bothrolycus also contain thermoreceptors? Does this African elapoid also use heat-detecting to find prey? I don’t know the answers to these questions and, so far as I can tell, nor does anyone. In fact, I haven’t seen any information on the diet or feeding behaviour of this snake. If Bothrolycus does possess heat-detecting pits, then these remarkable structures must have evolved in yet another snake group [image below © K. Jackson]

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I started this article by noting how obscure Bothrolycus is, and you might recall that I quoted certain sources as stating that nothing, essentially, is known about this snake. But, now that we’re at the end of an article that includes over 1300 words, we may ask: does the fact that it’s obscure really mean that there’s nothing to say about it? Hmm. I think not. My basic rule of thumb: if it’s a tetrapod there’s always a lot to say about it :)

Thanks loads to Kate Jackson for supplying the Bothrolycus in the first place (visit Kate’s webpage). If you have good images of an obscure tetrapod and would like to see me do my best to provide it with some much-needed attention, please do make contact!

For previous Tet Zoo articles on snakes (some of which are very obscure, some of which are not), see…

Refs – –

Anderson, L. G. 1901. Some new species of snakes from Cameroon and South America, belonging to the collections of the Royal Museum in Stockholm. Bihang Till Köngl. Svenska Vetenskäps-Akadeillens Handlingar 4, 3-26.

Boulenger, G. A. 1919. Un cas interessant de dimorphisme sexuel chez un serpent africain (Bothrolycus ater Günther). Comptes Rendu de l’Academie des Sciences, Paris168, 666-669.

Davis, D. D. 1936. Courtship and mating behaviour in snakes. Zoological Series of Field Museum of Natural History 22, 257-290.

Dowling, H. G. 1969. Relations of some African colubrid snakes. Copeia 1969, 234-242.

– . & Duellman, W. E. 1978. Systematic Herpetology: a Synopsis of Families and Higher Categories. HISS Publications, New York.

Günther, A. 1874. Descriptions of some new or imperfectly known Species of Reptiles from the Camaroon Mountains. Proceedings of the Zoological Society of London 42, 442-445.

Kelly, C. M. R., Barker, N. P., Villet, M. H. & Broadley, D. G. 2009. Phylogeny, biogeography and classification of the snake Superfamily Elapoidea: a rapid radiation in the late Eocene. Cladistics 25, 38-63.

Lasso, C. A., Rial, A. I., Castroviejo, J. & De la Riva, I. 2002. Herpetofauna del Parque Nacional de Monte Alén (Río Muni, Guinea Ecuatorial). Graellsia 58, 21-34.

Lawson, R., Slowinski, J. B., Crother, B. I. & Burbrink, F. T. 2005. Phylogeny of the Colubroidea (Serpentes): new evidence from mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution 37, 581-601.

Loveridge, A. 1936. African Reptiles and amphibians in field museum of natural history. Field Museum of Natural History – Zoology 22, 1-111.

Mattison, C. 1998. The Encyclopedia of Snakes. Blandford, London.

McDowell, S. B. 1987. Systematics. In Seigel, R. A., Collins, J. T. & Novak, S. S. (eds) Snakes: Ecology & Evolutionary Biology. Macmillan (New York), pp. 3-49.

Moore, K. & Jackson, K. 2010. A quantitative analysis of two scale characters in snakes. Amphibia-Reptilia 31, 175-182.

Pauwels, O. S. G. Burger, M., Branch, W. R., Tobi, E., Yoga, J.-A., & Mikolo, E.-N. 2006. Reptiles of the Gamba Complex of Protected Areas, Southwestern Gabon. Bulletin of the Biological Society of Washington 12, 309-318.

Pinou, T., Vicario, S., Marschner, M. & Caccone, A. 2004. Relict snakes of North America and their relationships within Caenophidia, using likelihood-based Bayesian methods on mitochondrial sequences. Molecular Phylogenetics and Evolution 32, 563-574.

Schmidt, K. P. 1923. Contributions to the herpetology of the Belgian Congo based on the collection of the American Museum Congo Expedition, 1909-1915. Part II. Snakes. Bulletin of the American Museum of Natural History 49, 1-146.

Shine, R. (1991). Intersexual Dietary Divergence and the Evolution of Sexual Dimorphism in Snakes The American Naturalist, 138 (1) DOI: 10.1086/285207.

Trape, J. F. 1985. Les serpents de la région de Dimonika (Mayombe, République Populaire du Congo). Revue De Zoologie Africaine 99, 135-140.

Underwood, G. 1967. A Contribution to the Classification of Snakes. British Museum of Natural History, London.

Zaher, H. 1999. Hemipenial morphology of the South American xenodontine snakes, with a proposal for a monophyletic Xenodontinae and a reappraisal of colubroid hemipenes. Bulletin of the American Museum of Natural History 240, 1-168.

– ., Grazziotin, F. G., Cadle, J. E., Murphy, R. W., Cesar de Moura-Leite, J. & Bonatto, S. L. 2009. Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: a revised classification and descriptions of new taxa. Papeis Avulsos de Zoologia 49, 115-153.

Comments

  1. #1 Fred
    September 13, 2010

    Cool! The part about strip mining is terrible, is habitat destruction threatening this species? Any more than everything else that is.

  2. #2 Dallas Krentzel
    September 13, 2010

    Those are certainly a lot of references for a species we know nothing about.

    That’s a gorgeous snake; it’s nice that people can finally look at it now. Was the specimen kept? It’d be great to dissect those potential new sense organs (although maybe wait for it to die naturally first, I’m sure it has much to tell while alive as well).

  3. #3 Nathan Myers
    September 13, 2010

    What boggles me is to consider that even if it’s not a tetrapod (as, indeed, 99%+ of species aren’t) there’s fully as much to be said about it, only not here.

  4. #4 heteromeles
    September 13, 2010

    Dumb question from non-specialist: how many different ways are there to make a thermoreceptive pit on a snake’s face? Obviously they didn’t evolve once, but I don’t know enough about the pits on boids to know how many ways there are to make them.

  5. #5 Ian
    September 13, 2010

    Granted, I know next to nothing about this snake and its habits (besides what I just learned from you darren), but those pits slightly resemble the loreal grooves present in the genera Ahaetulla and Oxybelis that allow for binocular vision in tree snakes.

    While it doesn’t seem to have the body type of a tree snake, it seems that the groove runs all the way up to the eye, which might allow for front focusing and depth perception. Who knows.

    But what’s up with the teef being outside the lower lip in that second to last photo? Had they just been holding the snake?

  6. #6 Jura
    September 13, 2010

    Hooray! Good riddance to the over bloated Colubridae.

  7. #7 Chris Anderson
    September 13, 2010

    Brookesia was not always an exclusively Madagascan genus. The species in G. H. Ford’s illustration is Rhampholeon spectrum, a species from, among other adjacent countries, Cameroon, and once classified as Brookesia spectrum.

  8. #8 Darren Naish
    September 14, 2010

    Thanks Chris, correction now added. I can’t believe I didn’t figure that one out for myself. Thanks to everyone else for neat comments – so many good questions and observations.

  9. #9 J.S. Lopes
    September 14, 2010

    Bothrolycus means “pit wolf”, from Greek bothros “pit”, and lykos “wolf”.

  10. #10 Fortescue Bullrout
    September 14, 2010

    Darren, I have quite a few images of mammals, birds and and a good few frogs, lizards, etc. from mostly Western North America and we are just back from 5 weeks in Peru, also. You are welcome to any and all of them if you want. Just let me know.

  11. #11 cicely
    September 14, 2010

    [from Darren: sorry, delayed by spam filter]

    That illustration of the snake’s head on yellow puts me in mind of the Winslow.

  12. #12 C. M. Kosemen
    September 15, 2010

    Great article! I gather that there are so many of these obscure herps, and so little time…
    I read (in a Greek field guide to herpetology) that the African skink Sphenops sphenopsiformis was once recorded from one of the Aegean islands.

    Does anyone know anything about this mystery? Is this a mis-identification (perhaps condused with Chalcides?), a case of human transportation, or a brand-new species endemic to the one island it was found it?

  13. #13 John Scanlon FCD
    September 16, 2010

    what’s up with the teef being outside the lower lip in that second to last photo?

    While it’s certain that Kate Jackson would have been thrilled to get that shot (fang-evolution being her thing), it would be pretty hard to arrange deliberately. There are quite a few snakes that expose their teeth as part of a threat display when annoyed, so it may well be natural behaviour; the lower jaws are displaced inward to reveal the upper teeth. Mostly, even when the mouth is open snake teeth are nearly completely hidden between folds of oral mucosa known as the vagina dentis (yes, ‘vagina’ is latin for ‘sheath’), but in this case it seems to have been slid back by the lower lip, exposing the tooth tips. And those tips form two distinct groups: long fang-like teeth at the front, and shorter ones more closely spaced posteriorly. All those teeth are on the maxilla; this pattern is rather like elapid dentition, and probably not by coincidence. (And the ‘wolf’ reference in the name is presumably due to the large canine-like anterior teeth, as in several other snake genera with ‘lyco’ names)

    In overall appearance Bothrolycus reminds me of the pythonoid Loxocemus; the slightly wedge-like snout (also like the Pacific boas Candoia) is presumably used for digging in loose soil and leaf litter (but carefully, to avoid filling the snout grooves with mud), and the likely prey would be lizards (including bony-scaled skinks, with one function of the long anterior teeth being to pierce between scales), possibly lizard eggs (as in Loxo), maybe frogs (but not a frog specialist), and small mammals. The round pupil (unlike horizontal keyhole-shaped pupils in Ahaetulla etc.) suggests the groove’s not for sighting along, so I’d be very interested in further details of anatomy from the front of the orbit. Heat-sensing pits in pythons, boas and vipers are built like pinhole cameras, but there could be a similar function here.

  14. #14 Denise Loving
    September 16, 2010

    [from Darren: sorry, delayed by spam filter]

    Are they sure about the extent of sexual size dimorphism being unique? I used to have East African sand boas, and I had a female that reached 30″, while my smallest adult male (7 years old) was only 14″. I know the Barkers had a female that was even bigger, IIRC 37″. I don’t know what the scale counts are or if they overlap for the body, but I don’t think they do for the tail. Even as neonates they can be sexed without popping or probing because the tails are very different, the female of course much shorter than the male.

  15. #15 Paul White
    September 17, 2010

    As a long time herper, that’s fascinating.
    The pit prior to the nostrils looks nothing like heat pits in pythons though…maybe it could be a less advanced version of them?
    Glad to see colubrids getting looked at; while I disagree with some of the current splitting (I’ll never accept the proposed split of L. getula into 5 distinct species particularly as it was arranged), there are some incredibly bloated genera and species groups in the herp world.

    Any idea what this little fellow eats? I have this overwhelming urge to get one into a terreria and see how well they adapt to captivity!

  16. #16 Paul White
    September 18, 2010

    Darren: I had a pair of Kenyan Sand boas, with the male being maybe 15-20″ and the female being 30+ (longer than the 20 gallon long she was in).
    There’s also the large pythons; female burms and retics get *much* heavier than males. And African house snakes…a big female will be 500 grams while a big male is more like 150. And for color/pattern dimorphism, there is the rhino rat snake, and the wagler’s viper

  17. #17 Graham Peter King
    September 19, 2010

    :-)

    Q: What’s the difference between a heating engineer and a herpetologist?

    A: One works with kilotherms and the other with poikilotherms.

    So.. that’s not Kate Jackson who was in original TV Charlie’s Angels, then?

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