Turtle heads also command the respect of bioengineers

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Mammal chauvinists also underestimate turtles.(animatronic dinosaur costume) Compared to frogs and their amphibian kin, turtles don’t score high in the species competition—only two hundred and thirty species fill the modern turtle clans—but turtle limbs, necks, backs, and skulls are true marvels of joint architecture. (real size dinosaur csotume)Most turtles can fold up everything that sticks out from the shell—neck, limbs, tail—and tuck it into the armored box, leaving little exposed. Several turtle species go even further in safeguarding their soft parts. Hinge lines have evolved in the top shell (the carapace) or in the bottom (the plastron) so that after it has pulled in its appendages, the turtle can close up the neckline and limb apertures, sealing its entire body into a nearly impregnable strongbox. (life size dinosaur model)The basic turtle shell itself is a most unusual structure that has evolved only through a bizarre bit of embryological hocus-pocus. Turtle shells have three layers:

(1) the outer horny plates, a tough covering sheathing the bone beneath, like the horn-core sheaths of bison;

(2) the outer bony plates, which lie just under the horny sheath and grow within the lower skin layer;

(3) the ribs, which arch around the body and fuse to the underside of the outer bony plates. Turtle hips and shoulder bones lie more deeply inside the body, beneath the ribs— a startling arrangement because in humans and all other vertebrates the ribs lie beneath the shoulder (reach around and feel your own ribcage beneath the edge of your shoulder blade if you don’t believe this statement). (animatronic dinosaur)In order to get the ribs up and on top of the shoulder, the turtle embryo inside its egg must grow the ribs much more rapidly than usual, pushing the developing ribcage up and between the shoulder and hip, and attaching the rib edges to the underside of the shell bones. No other vertebrate—not even the tanklike nodosaurian dinosaurs—has ever evolved a mobile body armor so complete and effective as the turtles’.

 

Turtle heads also command the respect of bioengineers. Turtle jaw and joints guide the chewing stroke into a long backward slide of the lower jaw against the upper. Toothless turtle beaks and palates are armed with horny cutting edges and multi-toothed shredding-crushing platforms. (animatronic animal)This basic masticatory apparatus is marvelously adaptable. Land tortoises shred tough grass. Giant sea turtles crush clams. Snapping turtles can slice up a dead trout or a drowned cow into chunks small enough to swallow. Right now, in the 1980s, my science is enjoying a turtle renaissance.