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.
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.
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)).
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).
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.
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
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]
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…
- Stupidly large snakes, the story so far
- Scolecophidians: seriously strange serpents
- Side-stabbing stiletto snakes
- Terrestrial elapids, take 2
- Why do some snakes have horns?
- Close encounters with the Father of Death
- Not two, not three, but FOUR anacondas
- The tiniest snakes
- “What was that cute little Mexican snake?”, and other musings…
- Snake 195 mm long eats centipede 140 mm long. Centipede too big. Snake dies.
- Micropechis ikaheka, the Small-eyed snake
- Help identify the snake. Please.
- Monster pythons of the Everglades: Inside Nature’s Giants series 2, part II
Refs – -
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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.
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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.