So, you’re a lungfish. You’re minding your own business, searching for snails and other tasty morsels in the warm, murky water of a tropical lowland lake that will, in some 340 million years, be in eastern Iowa. Your long but plump body—an aquatic sausage with teensy fins—swims through the shallows, past what looks like a large rock. It is not a rock. It’s a six-foot-long giant in this ancient ecosystem: a muscular menace that might be mistaken for an overbuilt crocodile with the head of a T. rex. With its…
