Bedding Planes

ichnology: the field of deciphering animal traces, tracks, and trails

Lasso Trail. to right: A half-billion years ago, just after the Cambrian evolutionary explosion, an unknown animal left behind this looping trace in Spanish sandstone. The details of the trackway provide “a phantom image of the animal,” says Adolf Seilacher. “It moved through the sediment like a submarine, being connected with the sediment surface only by a narrow snorkel.” During locomotion, this snorkel swayed to and fro, leaving behind a zigzag pattern down the middle of the track (just barely visible here, between the two parallel lines of the "track."


in the past....

Shrimp Burrow Jungle. to left: A tapestry from the Triassic period, this cast of a limestone bedding plane from central Italy shows the burrows created by mole shrimp more than 200 million years ago.

Modern species of mole shrimp create similar tunnels by using their strong legs to dig several meters below the seafloor. Where three tunnels meet, the shrimp excavate an expanded junction where they can somersault or change direction. Other wider sections may be used for storing or processing food, says Seilacher.

---from Richard Monastersky, “A Billion Years of Beauty”

on a “Fossil Art” exhibit of animal traces in stone created by paleontologist Adolf Seilacher, Yale University Peabody Museum of Natural History, 1998.

cf. Science News 154 (Dec. 19+26, 1998), pp. 298-400. Photos by Jens Rydell (Lasso) and William K. Sacco (Shrimp).



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