Take a whiff of mustard or wasabi and you’ll be hit with a familiar burning sensation. That’s the result of chemicals in these pungent foods hitting a protein called TRPA1, a molecular alarm that warns us about irritating substances. The same protein does a similar job in other animals, but rattlesnakes and vipers have put their version of TRPA1 to a more impressive and murderous purpose. They use it to sense the body heat of their prey.
Pit vipers are famed for their ability to detect the infrared radiation given off by warm-blooded prey, and none more so than the western diamondback rattlesnake. Its skills are so accurate that it can detect its prey at distances of up to a metre, and strike at objects just 0.2C warmer than the surrounding temperature. Against such abilities, darkness is no defence.
Like all pit vipers, the rattlesnake’s sixth sense depends on two innocuous pits located between their eyes and their nostrils. With two pits on either side of its head, the snake can even ‘see’ heat in stereo. Each pit is a hollow chamber with a thin membrane stretched across it, which acts as an “infrared antenna”. It is loaded with blood vessels, energy-harvesting mitochondria and dense clusters of nerves. The nerves connect with the visual parts of the snake’s brain, allowing it to match up images of both heat and light. So far, so clear, but until now, no one knew how the membranes actually worked.
Elena Gracheva and Nicolas Ingolia, from the University of California, San Francisco, have solved the mystery but it wasn’t easy. Rattlesnakes don’t give up their secrets readily. Their genes have rarely been sequenced and, in what must be the understatement of the year, Gracheva and Ingolia describe them as “genetically intractable” and “inconvenient subjects for physiological and behavioural studies”. To translate: if you’re looking for a model animal to work with, you’re probably better off with fruit flies and zebrafish than a four-foot serpent with a deadly bite.
Snakes have been around for nearly 100 million years and scientists have found many fossils of extinct species. But this astonishing specimen is different. This serpent is Sanajeh indicus. It is sitting in a dinosaur nest and its coils surround three eggs and the body of a hatchling.
There are many reasons to think that this prehistoric tableau represented a predator caught in the act of hunting, rather than a mash-up of unconnected players thrown together by chance. The snake is perfectly posed, with its head resting atop a coil and its body encircling a crushed egg. All the pieces are very well preserved and very little of the snake, the dinosaur or the crushed egg have been deformed. All of this suggests that the animals were caught unawares and quickly buried in sediment.
The hatchling in question is a baby sauropod part of the dinosaur lineage that included the largest land animals of all time. It was probably a titanosaur, and being in India, that narrows things down to two known species – Isisaurus and Jainosaurus. The adults were formidable animals, 20-25 metres in length and protected by bony armour running down their backs. But even the largest dinosaurs must have hatched out of a small egg, and at that point, they were vulnerable. The hatchling that Sanajeh was about to dispatch was just 50 centimetres long, while the snake itself was measured 3.5 metres.
Despite this size discrepancy, the hatchling would still have been a substantial mouthful. Most modern snakes wouldn’t have any problem with that. Their lower jaws can unhinge to give them a massive gape and their flexible skulls are made of bones that can move against each other.
Sanajeh was halfway towards developing these specialisations. It didn’t have the fixed skulls and narrow gapes of the most primitive of modern snakes, nor could its maw open quite as wide as today’s record-breakers. Nonetheless, it could certainly swallow a sauropod infant and that ability earned Sanajeh inidcus its name. The words are Sanskrit for “ancient gape from the Indus”.
This is sure to be one of the most amazing scientific images of the year. You’re looking at vertebrae from two species of snake. The smaller model on the left belongs to the anaconda, a giant serpent that can grow to 7 metres in length and weigh as much as 45kg. It’s arguably the largest snake alive, so just think about how big the owner of the fossilised vertebra on the right would have been! There’s a good reason why this new discovery – the largest snake that ever slithered – has been named Titanoboa.
Titanoboa cerrejonesis is new to science and was discovered by a team of North American scientists led by Jason Head at the University of Toronto. It’s the latest fossil to emerge from Colombia’s Cerrejon coal mine, one of the world’s largest open-pit mines and an unexpected bonanza of prehistoric reptile fossils.
The giant serpent is closely related to today’s boas and anacondas, snakes that kill their prey with suffocating coils. Living boas come in various sizes, but their similar proportions gave Head the data he needed to work out how big Titanoboa actually was. The backbones of boas are similar enough that, with help from a computer, you can tell where any individual vertebra sits down the length of the snake by looking at its shape. And you can take an accurate stab at the length of the entire snake based on the size of each vertebra – all members have the same number of segments, and their size is proportional to the animal’s length.
Titanoboa‘s fossilised vertebra showed that it was a whopping 13 metres (42 feet) long. By comparison, the largest verifiable record for a living snake belongs to a 10-metre-long reticulated python, and that was probably a striking exception. Large population surveys of reticulated pythons have failed to find individuals longer than 6 metres. By contrast, Head’s team analysed vertebrae from eight different specimens of Titanoboa and found that all of them were roughly the same size. A length of 13 metres was fairly ordinary for this extraordinary serpent. Not quite Jormungandr, but amazing nonetheless.