This ode to turtlenecks was great! But it was missing something very important: actual turtle necks.
Turtlenecks resemble actual turtle necks.
Turtles do this nifty thing where they can pull their heads into their shells. The skin on their neck is loose to accommodate this anatomical quirk and takes on a folded-collar-like appearance when their necks are partially retracted. Remember this when you don your sweaters this season.
Some turtles fold their neck to the side.
There are two extant suborders of turtles: Cryptodira and Pleurodira. Cryptodira (lit: hidden neck) pull their necks straight into their shell, but Pleurodira (such as the handsome fellow shown above) retract their heads partway before folding them off to the side. Pleurodira are commonly found in the southern hemisphere, so it's unlikely you'll run into a side-necked turtle in the United States unless it's someone's pet.
Common snapping turtles have long necks.
Left: A snapping turtle with its neck partially retracted. Right: A snapping turtle with its neck extended. Basically, common snapping turtles usually kept their heads close to their bodies in the hopes of surprising prey by that wander in range of their snap. Don't be fooled; their necks are typically as long as the length of their shell, and they can twist them backwards if they're so inclined. That's why the best place to hold a snapping turtle is by the back shell near the tail (and never by the tail!) so you're not in range of its neck and powerful jaws.
Alligator snappers have short(er) necks.
Which, of course, means they can't surprise their prey by suddenly lunging quite as effectively as their common snapper cousins. To make up for their short necks, alligator snappers have a worm-like appendage in their mouths that they use to lure their prey closer. When they're hungry, they sit in the mud with their mouths wide open and wriggle their tongues. It's like fishing, and it's pretty damn effective.
