Filed under: Uncategorized | Tags: folklore, latin, literature, lizards, reptiles, science, top ten
One of my secret, silly passions in life is the history of biology, and from that rich and varied history, one of my favorite parts is the medieval bestiary. For those of you who have never seen one, a bestiary was a richly illustrated textbook somewhere between Animal Planet and Sunday School. Illustrations of animals would be accompanied by text that described, in greater or lesser detail, their natural history, and what religious lessons could be drawn from these animals and their lives: Pelicans, for example, said to feed their young on their own blood, represented the incredible mercy and self-sacrifice of Christ, while serpents, of any kind, generally represented the devil.
Now, medieval bestiaries were written by monks, who very rarely got into the fresh air, and while they might have been fairly familiar with the habits of common barnyard dogs and cats, they had to take a little license and a lot of faith when describing animals they had never seen; like crocodiles, elephants and giraffes. Understandably, they didn’t always get things right: while we might, today, associate the giraffe with the fabulous camelopard, it’s a far cry from its description today, and no one has yet found a living unicorn or (my personal favorite) bonnacon.
That being said, sometimes natural history has a way of sneaking back on you and asserting itself in the strangest of medieval legends. Take the following passage from Isidore of Seville (my very rough translation follows, and better classicists than me are invited to tell me that I have failed).
Amphisbaena dicta, eo quod duo capita habeat, unum in loco suo, alterum in cauda, currens ex utroque capite, tractu corporis circulato. Haec sola serpentium frigori se committit […] Cuius oculi lucent veluti lucernae.
Etymologies, Book 12
It is said of the Amphisbaena that it is a serpent with two heads, one in its proper place, the other on the tail. It can run in the direction of either head, moving its body in a circular motion. This is the only snake able to live in the cold. His eyes shine like lamps.
Like I said, I’m no classicist, and the translation is a pretty rough one. (I know enough to get the gist of a text, not enough to stake my life on knowing what it says.) But, what’s interesting is that there’s a real-life beast called an amphisbaenian, named after the mythological monster.
And while they don’t look exactly like their medieval counterparts, they are more similar than you might think. We’re going to take a look at one particularly unique member of the group. So, by all means, read on to find out more. Continue reading
Filed under: Uncategorized | Tags: crocodiles, Gavialis, reptiles, Tomistoma, top ten
Okay, so fair warning — this post might get very long, since it’s all about the group that I am currently studying. And while I’m passionate to ramble about reptiles for thousand-word posts, when it comes to today’s subject, I’m good to ramble for, well, years probably. But, well, it wouldn’t be fair to list off a group of remarkable reptiles without including at least one crocodilian, and, of course, I picked the world’s most unique crocodile as my subject of study.
Crocodiles really are my favorite animals. People will tell you that they’re living fossils and that they have remained unchanged since the Jurassic, and while that’s sort-of true in that there’s a generalized ‘croc-shape’ that crocodiles tend to fall back on (and there certainly aren’t as many around as there used to be), it ignores the incredible fossil diversity of crocodiles through time. There are crocodiles that became terrestrial herbivores and crocodiles that took to an exclusively marine life and crocodiles that evolved mammal-life teeth and crocodiles that grew to forty feet. The ancestors of crocodiles were lithe, upright little predators with long legs who lived only on land, while the more typical crocodilian niche was occupied by their close-relatives: phytosaurs … which looked pretty much like a modern croc, except that they had their nostrils between their eyes.
See, look, I knew I would digress. The point is that crocodilian diversity is amazing, and even if they aren’t as diverse as they once were, their current diversity is amazing: from the five-foot long dwarf caiman of South America to Nile Crocodiles who live in marginal environments on the edge of the Sahara and their fossil diversity is beyond incredible. Their closest living relatives are birds, and, depending on who you ask, they might be very closely related to turtles. They differ from birds, though, in the morphology of their ankle — while bird ankle joints allow for a very limited front-back flexion, crocodile ankles, like yours, can rotate. This has some pretty interesting implications for their gait: basically it allows them to adopt a variety of different walking stances — they can walk upright like a mammal, sprawl like a lizard and can even gallop. The crocodilian biology database has a really fantastic page with videos of all the exciting forms of croc locomotion.
Look, I’m digressing again. At this rate, we’ll never get to my remarkable crocodilian. Why don’t you just read on to find out what he is, before I get completely distracted. Continue reading
Filed under: Uncategorized | Tags: lizards, reptiles, science, snakes, top ten
I will admit that I am a sucker for snakes. They’re fascinating, they’re venomous (at least some), they’re beautiful, they’re diverse, they’ve invaded a huge variety of habitats and occupy a surprisingly large niche space, they have a great mythological association; basically, snakes are pretty darned cool animals, and they managed this huge extent of awesome all without legs. I actually gave a presentation in my evolutionary developmental biology class yesterday on how snakes lost their legs, and while I might blog that later, this post is yet another entry in my remarkable reptiles countdown.
And so, today’s post starts with a reminder that snakes aren’t the only lizards that have lost their legs. In fact, leg loss seems to be a common thing in lizards, from the very primitive to the derived. From amphisbaenians to blind lizards to skinks, legless lizards come in all shapes, sizes and phylogenetic contexts. Really, it’s pretty amazing that this trait has evolved so many times over so many groups. It’s a trait that, in legless lizards, at least, seems to have evolved in conjunction with a burrowing lifestyle, although there’s still some pretty heated scientific controversy over whether the earliest snakes lost their limbs in order to become better swimmers or better burrowers (although the developmental and genetic context for that loss is actually pretty well understood; ask me about that sometime).
The lizard above is one of my favorite legless lizards, and it’s a pretty good representative of what a standard-issue legless lizard looks like. He has eyelids and ear openings, unlike a snake, and is a substrate-burrowing insect-eater. (I have to admit, though, his scientific name does tickle my fancy: it literally translates to ‘snake-lizard without legs.’) So, if this boy is ordinary what kind of a legless monster would earn his place on my countdown? Read on to find out about a different kind of legless lizard… Continue reading
Sorry about the late blogging: I work on Wednesdays, and come home late, so the blog takes a bit of a back-seat priority. But, never fear: I still have, uh, forty minutes to write out a blog entry on my eighth remarkable reptile.
So, what do you get if you cross a cobra with a colugo?
|Cobra + Colugo = ?|
The answer, of course, is today’s featured reptile. Read on to find out … Continue reading
Today, we’re staying in snakes, but we’re going to look at the evolution of a really hot-sauce characteristic in the group: venom. Venom is probably the reason that people have such an irrational fear of snakes, and is also one of the most intriguing of the features found in snakes. Of course, there are other venomous reptiles — the beaded lizards and gila monsters are the best-known venomous lizards, and venom has been implicated as one of the reasons, in addition to massive bacterial load, that the bite of komodo dragons is so devastating (Incidentally, if anyone wants to buy me a pet gila monster, I wouldn’t say no.)
Snakes use their venom for both prey capture and defense — it’s utility in each is fairly obvious: as a defensive mechanism, it is enormously effective in deterring a would-be attacker by killing them or causing fairly excruciating pain, while in prey capture, venom subdues the prey and begins the digestion process in the snake. Both uses are very well-documented in venomous snakes, but the question remains: which came first, the chicken or the egg? Or, in this case, what is the primary purpose of venom? What did it evolve for? And if one of those functions disappears, will there still be selection pressure to produce venom?
To answer this question, we’re turning to a fascinating group of snakes: the sea snakes. Snakes make up about eighty percent of marine reptile life (the other twenty percent consists of sea turtles and the saltwater crocodile). The true sea snakes, or Hydrophines, make up the majority of that salt-water snake diversity. These animals are highly specialized, with salt-excreting glands, paddle tails, and, most importantly for our purposes, an incredibly strong neurotoxic venom. The vast majority of these snakes are fish hunters, which accounts for the potency of their venom — in order to subdue fish prey, and to keep it from being stolen or swimming away, their venom has to be very fast-acting indeed. So, while these snakes are, for the most part docile, they are far from harmless and can easily kill an adult human.
The olive sea snake, shown above, is a pretty typical Hydrophine snake. So, why do sea snakes make my remarkable reptiles list? And what do they have to do with venom evolution? To find out the answer to that question, read on. Continue reading
Filed under: Uncategorized | Tags: pets, reptiles, science, snakes, top ten
I have always been a fan of island biogeography and one of my big passions in biology are the weird things that animals do on islands. From giant flightless birds to enormous tortoises to pygmy elephants, the variety of life on islands never ceases to amaze me. And while the science has its practical uses, beyond initial wonderment and amazement, from predicting alpine responses to climate change to managing wildlife preserves, my fascination with islands still stems primarily from their wondrous diversity of life.
(Incidentally, if this description of a fascinating science has piqued your interest at all, may I recommend David Quammen’s The Song of the Dodo to you? It’s a really remarkable, well-written look at the scope of the science, and its practical implications, and while I may hold reservations about some of his assertions, it’s still a very good book.)
And so, we start my look at remarkable reptiles with one species that really exemplifies the magnificent and diverse beauty of islands — the common boa, Boa constrictor.
The subspecies that you’re probably familiar with is the one sold in pet stores across the world; the Colombian red-tailed boa, a locality specimen of B. c. imperator. With their charming disposition and fairly impressive size of up to about nine feet, they are an instantly recognizable snake. But, just in case you’ve never seen one, here’s a picture of one of these mainland beauties:
So, if you’re interested in what these beauties do when they get onto islands, read more after the jump. Continue reading