Tag Archives for snakes

Friday mystery object #508 answer

Last week I gave you a St Patrick’s themed mystery object in the form of this snake:

It was a really difficult ask – the skin is faded and the specimen has been chopped into several pieces, making identification very tricky. I did provide a clue with the location of where this specimen is from, to offer a little help in narrowing down the possibilities (it’s from Venezuela).

Unfortunately, as Adam Yates spotted, I managed to leave in another more obvious clue that I thought I’d removed – the name of the species, which appears in the photo of the full specimen. I cropped the image in WordPress, not realising that if you click on it the original uncropped image opens. Not my finest moment!

However, specimen identifications need to be taken with a pinch of salt until they’re verified, so let’s do that as best we can.

The side view of the head of this specimen gives a useful clue that Adam picked up on:

It has a sensory pit between the eye and the nostril, indicating that this is a type of Pit Viper, which does help reduce the options from around 50 Venezeulan snake species to around 15 or so. It’s also consistent with the identification of Bothrops venezuelensis Sandner-Montilla, 1952.

Most of the other Pit Vipers are fairly distinct from this specimen in terms of colour and pattern, but there are a couple of members of the Genus Bothrops (the Lanceheads) that are similar to this.

You may just be able to see a hint of a stripe behind the eye that terminates just above the last scale above the mouth, which can be useful in distinguishing between B. atrox (where the stripe touches the last three scales over the mouth) and B. asper (where it just touches that last scale as we see here), but this feature is less relaibe for B. venezuelensis, which can be distinguished from the other two species by having a more rounded rostrum:

This specimen’s rostrum (snout) is a little pointy, but for a type of snake called a Lancehead, you expect them to be very pointy. Of course this specimen is a little imperfectly prepared, so the rostrum shape may be misleading. As a result, I’d be a bit unwilling to differentiate between B. asper and B. venezuelensis based on the images.

What we do know is that this was certainly a venomous snake, since it bit a farm labourer working on a hacienda who required two doses of antivenom, but they thankfully survived. I suspect that this is why the head is separated, since the snake was killed and presumably identified to assist with administration to the appropriate antivenom.

This specimen is one of several from the same collector, who I plan to talk about more in future posts, since we have great information about a fascinating life.

Friday mystery object #508

This Friday we’re gearing up for the St. Patrick’s weekend here in Ireland, so it seems only appropriate to have a snake for you to have a go at identifying:

It’s not an easy one, so if you need a clue to help narrow down the options, I can confirm that this specimen is most definitely not Irish and is in fact from a bit further afield.

Big thanks to our Terrestrial Zoology Curator Emma for sharing these photos.

I look forward to seeing how you do with this tricky St. Patrick’s themed mystery object!

Friday mystery object #373 answer

Last week I gave you this pretty cool skull to have a go at identifying:

 

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As everyone recognised, it’s the skull of a snake. I think that’s clear from those extremely long quadrate bones (highlighted in purple in the top view), with which the lower jaw articulates to allow a huge gape for swallowing prey whole. However, there are a lot of snakes out there – around 3,600 species, which means there are lots of possibilities for the species that this particular skull belongs to.

The side view allows us to rule out quite a few possibilities, since it’s clear from the teeth that this isn’t one of the front-fanged snakes (vipers and elapids).

PICT0082

Rattlesnake skull, with its big front fangs.

The light construction of the skull suggests it’s not one of the constricting snakes, which have much more robust skulls for dealing with the forces generated by the struggles of relatively large prey.

PICT0159

Python skull, with a robust construction for wrangling prey.

The teeth are quite small and although there are a couple of slightly longer ones in the tooth row, they hardly count as real fangs at a paltry 3mm long. So we’re probably dealing with one of the ‘non-venomous’ colubrid snakes (many of these are actually venomous, but lack the appropriate tools to deliver that venom through human skin).

Of course, there are still well over a thousand possible species in the Colubridae – but this is where you have to start ruling out possibilities by comparing the specimen against species that are common and widespread, to begin the process of narrowing down the options.

Since this specimen is in the Museum in Ireland, Europe is a good place to start looking for likely candidates (Ireland itself being famously devoid of native snakes). There is a rather old (published in 1913), but still very useful reference called The Snakes of Europe, by G. A. Boulenger which has a section on identifying species based on their skulls.

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Fig. 6—Skull of Tropidonotus natrix. (From British Museum Catalogue of Snakes). Illustration from The Snakes of Europe, by G. A. Boulenger, 1913

If you take a look through, it quickly becomes apparent that there is one species that matches the mystery object very closely – even to the position of the slightly larger teeth. It’s a species that has an interesting defense mechanism that jennifermacaire referred to:

…The closest skull I could find is from a snake that likes to roll over and play dead…

This is a fascinating behaviour seen in several snake species, but Jennifer is correct that it is seen in the species that this skull is from – the European Grass snake Natrix sp.

Of course, the story then gets more complicated again, since a couple of subspecies of Grass snake have been elevated to species in the last few years. The Iberian subspecies Natrix natrix astreptophora was recognised as N. astreptophora in 2016 and the subspecies N. n. helvetica found west of the Rhine (including in the UK) was updated to N. helvetica in 2017.

These studies were based on genetics and I’ve yet to see any way of differentiating between these species using skeletal features, so for now the best I can say about this specimen is that it’s Natrix sp. I hope you enjoyed that little slither into the world of snakes, which seems to have opened a bit of a can of worms…

 

 

Friday mystery object #281 answer

Last week I asked for your opinion on this mystery object:

mystery281

It had originally been identified as Boa constrictor and then reidentified as Green Anaconda, but I didn’t believe either of those options.

There was some activity in the comments, from the initial observation that it’s a snake from Wood, to Andy Mills’ suggestion of Python, with palfreyman1414 and Daniel Jones and Daniel Calleri’s discussing how to tell whether it’s a boid or pythonid.

In fact, palfreyman1414 did some sterling work tracking down characteristics to help distinguish between these commonly confused groups, with this handy comment:

“The postfrontal bone, usually present, borders the orbit behind, rarely also above, and in the pythons a supraorbital bone is intercalated between it and the prefrontal bone.”

And..

“Boids are, however, distinguished from the pythons in that none has postfrontal bones or premaxillary teeth”

The character of the presence or absence of teeth in the premaxilla (the frontmost bone of the upper jaw in the midline of the skull) is particularly useful, although it’s not unusual for the premaxilla to fall out of snake skulls.

The postfrontal character is a bit less obvious and I’m not fully convinced by it – not because there isn’t an extra bone in the pythons compared to the boas (there is), it’s just whether it’s a postfrontal, a supraorbital or a post orbital. That depends on the reference you read. To help get an idea of the bits we’re talking about, I’ve highlighted them here (purple for premaxilla, pink for the bit missing in boids, call them what you like):

mystery281_bones

It’s probably worth mentioning that Anacondas are members of the boid family, so it’s clear that this specimen is a pythonid rather than a boid. But that doesn’t tell us what species it is (if you want to see a Boa constrictor skull there’s a video of one here).

Comparing overall skull shapes in snakes is not very effective, since the skull is very loosely articulated to allow it to deform when swallowing large prey, so when mounted they can be very variable in shape. Because of this you need to compare the shapes of the various bones that make up the skull to narrow it down.

There is a very helpful image resource called BioLib that has validated photos of skulls amongst other images, so it’s well worth checking out. Trawling through I didn’t manage to find a species with the same shapes in the nasals, prefrontals, frontals, parietals and supratemporal – but I did discover a specimen photo by Jean-Christophe Thiel that fit (not to mention a previous mystery object) – so I’m fairly confident that this is a Royal Python Python regius (Shaw, 1802).

Many thanks to everyone for their comments – it’s been a fun challenge where I know I’ve learned an awful lot. I hope you have too!

Friday mystery object #197 answer

On Friday I gave you this skull to identify:

mystery197

As I suspected, it wasn’t too much of a challenge. Jake got in quick with the suggestion of a Sri Lankan Python, with Gina Allnatt, Kevin and Rhina Duque-Thues all agreeing with a generic Python sp. identification. Nicola Newton also suggested Python, but she was of the opinion that it was probably a Royal Python or Carpet Python on the basis of the size.

I agree with Nicola and think that this is most likely the skull of a Royal (or Ball) Python Python regius (Shaw, 1802), based on the size of the specimen and the shape of the supratemporal and frontal bones compared to other Pythons I was able to find images for (if you don’t know which bones I mean you can see what I mean on a handy annotated picture of a Python skull from the Digimorph website).

Pet ball python - normal phase, probably an import (rescue). By Mokele

The skull is one of several similar specimens from the old King’s College teaching collection, so it’s a pretty good bet that the skulls came from either research animals or pets. The Royal Python is a fairly small African Python that is commonly sold as a pet because it has a mild temperament – so that helps offer a bit of support for the identification, although what’s really needed is a detailed identification key for Python skulls or access to good comparative material.

The lack of good resources for identifying the skulls of snakes is a bit frustrating. After working with bird and mammal skulls, where there are some amazing resources like Skullsite and the Mammalian Crania Photographic Archive I’m still searching for something similar for reptiles. Perhaps the Deep Scaly Project will deliver the goods one day… here’s hoping!