On Friday I gave you this image and asked you to identify what it is:
I am pleased to say that it led you a merry chase before we got to the correct answer – but very well done to Debi, Jim and especially Woolgatherer for getting there! It is indeed a rattlesnake (Crotalus horridus) skull seen from a dorsal view.
If I had shown it from a lateral view I don’t think there would have been much difficulty working it out:
As it was, this was a tricky one – snake skulls are highly derived structures, particularly in the Viperidae, the family to which the rattlesnake belongs. The adaptations of the skull are all about prey capture and feeding, after all, snakes can’t immobilise their prey using their limbs.
Rattlesnakes are a type of pit-viper (subfamily Crotalinae), which is a name that refers to a pit-shaped heat detecting organ beneath the eye. These snakes have two pairs of hollow hinged fangs (click the image above and look closely to see the double fangs), which act like hypodermic syringes for injecting powerful toxins (which vary in composition according to distribution). The skull is very reduced and lightweight in its structure, partly to aid in striking but also to facilitate feeding. In fact the difficulty that many people had in identifying this skull lies in the odd shape of the jaw hinge. By having the hinge so far back on the skull, the snake can open its mouth really wide. Moreover, the quadrate provides an additional point of articulation with the lower jaw – a “double hinge” that allows one side of the unfused lower jaw to be pushed forward at a time whilst swallowing. This motion “walks” the food down the throat, ratcheted in on the strongly backwards curved teeth of one side of the lower jaw at a time. Since the lower jaw is unfused the mouth can also open wider laterally – enabling the snake to swallow prey far bigger than its head.