how did turtles get their shell?
In a study to be published Thursday, scientists report on the discovery of a missing-link species — Odontochelys semitestacea, for “”toothed, half-shell turtle”” — whose outer shell emerged directly from the ribs and backbone and not from the skin, as some have argued. The find also suggests that turtles originated in water rather than on land, and pushes back the group’s first known appearance on Earth by some 10 million years. Since the era of dinosaurs, which roamed the planet until 65 million years ago, turtles have looked pretty much the way they do today. They sport an armor-like upper shell, known as a carapace, connected to a softer lower part, called a plastron. But in the absence of hard evidence, scientists argued since the early 1800s over exactly how this reptilian mobile home came into being. One school of thought said the shell evolved from skin. According to this theory, small bony plates called osteoderms — like those found on crocodiles — broadened in size to form
