In reality, fairy rings are the result of the natural tendency of mycelium (the underground "spreading" portion of the organism) to spread out in a ring shape.
Think of the mycelium like a radar blip, slowly moving outwards in an ever-expanding circle. The only above ground signs of the movement are an early ring-shaped change in the color of the surrounding ground and grass (due to the decay of older mycelium, which releases nutrients into the soil) and a late "bloom" of the cap (basidiocarp) - the spore releasing fruiting body of the fungus.
These basidiocarps, which we call mushrooms, grow from the rings of mycelium, release spores in a circular fashion, perpetuating the fairy ring.
I stumbled on this fairy ring just a couple of weeks ago, just outside of the student union at FSU. I ran around campus (and back into the publications office) trying to find a camera while Heather waited patiently in the car.
I think it is Chlorophyllum molybdites, one of the species found in this area that tends to grow in rings. Chlorophyllum is poisonous, and causes much confusion [and indigestion] among its human and animal consumers:
Of the mushrooms generally considered poisonous, the one far most often consumed is Chlorophyllum molybdites. It is large and meaty; it resembles a generally choice edible, Lepiota (Chlorophylium) rachodes, it tastes good; and it grows in lawns and parks. Chlorophyllum molybdites quickly rewards the unwary with gastric distress, vomiting, and diarrhea lasting several hours.
Hopefully this week I'll be able to get back to the dinosaur/body temp discussion; it's been a crazy few weeks between the newspaper, tests, papers and labs.