No, this isn't an archival autopsy photo from Roswell, though it might as well be. It's actually an legless, lungless amphibian recently discovered in the Madeira River basin in Brazil. Nicknamed the "trouser snake", scientists knew of atretochoana eiselti only from two preserved specimens in a Vienna museum until 2011 when a living eiselti was discovered in Brazil. Unlike it's closest relatives, this particular species doesn't use lungs but a series of capillaries capable of gas exchange that course through its epidermis. It also has several muscles in its head unknown to any other organism on earth.
In case atretochoana isn't exactly the trouser snake you were looking for, here are few more examples I found online:
Thanks to BSD reader Richard for finding the real trouser snake and passing it along.