Diggin’ dinos
Enigmatic structures in Australian rocks may be the filled-in remains of world’s oldest dinosaur burrows
By Sid Perkins
Three enigmatic structures embedded in 106-million-year-old Australian rocks may be the remains of dinosaur burrows that were filled in by an ancient flood, a new study suggests. If that’s true, these fossils represent the oldest known dinosaur burrows and the first found outside North America.
The purported burrows sit within three meters of each other in now-hardened material that was laid down as sandy sediment along a stream bank near what is now Australia’s southern coast, says Anthony Martin, a paleontologist at Emory University in Atlanta who described the fossils online and in an upcoming Cretaceous Research. Recent erosion has erased much of two of the structures, but what remains of the largest one is remarkably similar to the remains of dinosaur burrows discovered in North America a few years ago (SN: 10/27/07, p. 259).
The largest of the remaining structures is a 2.1-meter-long, stomach-shaped clump of rock with a narrow, slightly curved protrusion and appears to represent a complete burrow. The broad end of the clump is 1 meter long and 40 centimeters wide, and its lowermost 30 centimeters is composed of large pebbles, Martin says. The rest of the structure, including the protrusion, is made of coarse-grained sandstone. Because the clump is embedded in a different material, a fine-grained sandstone, Martin suggests that it represents a chamber that once was open but was then filled with material washed in by two separate floods.