July 12, 2005

Museum of the Earth opens exhibit that brings ocean fossils to life

On July 15, the Museum of the Earth at the Paleontological Research Institution (PRI), which is affiliated with Cornell University, will open a new exhibit on ammonoids, prehistoric sea animals that first appeared in the fossil record 400 million years ago, survived four major extinctions and died out with the dinosaurs 65 million years ago.

The exhibit, which will last into September, is the second in an ongoing rotation of temporary exhibits at the museum.

"This is the most ambitious temporary exhibit we've had yet since the museum opened in 2003," said Pete St. John, the museum's exhibits manager. The exhibit will draw on PRI's large collection of ammonoid fossils, one of the largest in the country.

Many experts point to squids as ammonoids' closest modern relative, though the fossils more closely resemble the shelled nautilus in appearance.

With few direct records of the soft parts of these animals, researchers must make informed guesses into what these animals looked like and how they behaved based on the fossil record and by looking at modern cephalopods, including the squid, octopus and nautilus. The exhibit aims to show the fossilized animal in three dimensions and to bring them to life in people's minds.

"One of the goals is to create a living history," said St. John. "We'd like the exhibit to say, here's how this animal might have been, based on all we know from the fossil record."

The earliest written records of ammonoid fossils are from Roman times, and both Hindu and Native American cultures view the fossils as sacred. Native Americans believe the fossils carry healing powers. Until the nautilus was discovered in the early 1700s, no one had any idea what the ammonoids were.

"Paleontology works by comparing fossils with things that are alive today, so if we hadn't found the nautilus, we would never know what this was," said Warren Allmon, director of PRI, which runs the Museum of the Earth and signed an affiliation agreement with Cornell in 2004.

Before the discovery of the nautilus, ammonoids were thought to be coiled petrified snakes, and during medieval times snakes' heads were often carved into the fossils. The name "ammon-oid" comes from the Egyptian god Ammon, who was often represented with coiled ram's horns.

The fossils are amazingly diverse, often coiled with chambers, but they also can have spiked, straight or looping shells and range in size from smaller than a golf ball to 5 feet across.

People often use the names ammonites and ammonoids interchangeably, but technically ammonites are a subgroup of a larger grouping of ammonoids.

Based on a model of the nautilus, one interactive exhibit will show and explain how ammonoids may have drawn gases from the water into their shells to adjust their buoyancy as they rose and sank in the water. Like cephalopods today, they likely moved by water jet propulsion.

A timeline will show how ammonoids started in the Devonian era and barely survived four major extinctions that spanned the end of the Devonian through the Mesozoic eras.

"They were evolutionarily volatile," said Allmon, noting that a few species of ammonoids may have survived each period, but those few quickly adapted and spread until the next extinction struck. "They evolved like crazy, but species also went extinct rapidly, and they just barely snuck through each extinction."

No one knows exactly why ammonoids died out 65 million years ago, but some scientists believe that their demise may be related to their young, which floated among plankton after hatching. Nautilus hatchlings crawl along the ocean floor. Whatever killed the dinosaurs -- possibly a comet that crashed to Earth and kicked up dust and water vapor into the atmosphere -- may have inhibited photosynthesis and killed plankton that provided refuge for ammonoid young.

At the exhibit, a video will show the nautilus. Nearby, a family tree interspersed with actual fossil specimens will have artistic renditions hanging above. Another wall will describe ammonoid biology, including what ammonoids ate, what preyed on them, why their shells were shaped the way they were and how they moved. A 12-by-20-foot mural will depict the ecology of life in the seas of the late Jurassic period, when ammonoids swam in massive predatory schools.

"The mural is about both the food that they ate and the food they became," said local artist Dan Burgevin, who was commissioned to paint the mural. Burgevin was well-suited to paint this mural; he is also a fossil collector and an amateur paleontologist with a lifelong fascination for such prehistoric creatures as ammonoids.

The Museum of the Earth is located at 1259 Trumansburg Road (Route 96), just north of Ithaca.