What's the biggest dinosaur ever? Not Seismosaurus, the "earth shaker reptile," though he may have been 150 feet long — the longest animal ever. Not Ultrasaurus, the huge brachiosaur known from just a few bones found in Utah and thought to be as tall as a 6 story building, and as heavy as 10 bull elephants — more than 50 tons and nearly 100 feet long.

No, the new champion biggest dinosaur is Argentinosaurus and I think you can guess where it was found. To be exact, it was found in 1987 beside a road in the badlands near Plaza Huincul. That's a city in Nequen Province of Patagonia in north central Argentina.

The first bone found of Argentinosaurus was discovered by a local rancher on his land, and he thought it was a fossil tree branch. Scientists identified it as the shin bone of a dinosaur. This one bone was as tall as my 11-year old daughter, Erica: five feet high.

For the past several summers, Dr. Rodolfo Coria from the Plaza Huincul Museum has been leading excavations to uncover more of the giant dinosaur. He has dug up several backbones and each one is five feet high by five feet wide, and a ton in weight! They are the largest backbones known from any animal. He's also found part of the hips and ribs and last month, a tiny bit of the lower jaw.

From the bones he has found so far, Dr. Coria can estimate the size of Argentinosaurus — 110 feet long and 100 tons. That's as heavy as 20 bull elephants and as long as 3 school buses. In 1993 he named the dinosaur the Argentinosaurus.

The sandstone, full of large pebbles, in which the bones are fossilized indicates that the animal died and was buried in a fast-flowing stream that spread its bones over an area the size of a football field. The rock containing the bones is hard and Dr. Coria needs to use air-powered drills to chop away at the rock surrounding the fossils.

He always leaves a lot of rock around the bone to protect it while in the field. Then, as in most fossil digs, he "jackets" the bones with strips of burlap or cloth soaked in plaster. This hardens over the fossil to make a strong cast for shipping the bone back to his museum. In the museum workshop, Dr. Coria carefully chips away the remaining the rock from around the bone using tiny dentist's tools. The age of the rock around the bone is 90 million years. Fossil wood found in the area suggests that these giant plant eaters fed on the branches of the evergreen trees that lived in the ancient forest that stood in what is now a windy scrub land.

My daughter, Rebecca, aged 14 and I visited the Argentinosaurus dig site this spring (1995) with Dr. Coria. He also took us to another nearby site where he has found the largest meat-eater ever, even bigger than T. rex! This dinosaur isn't officially named yet, but will be "Giganotosaurus," the giant of the south. It was heavier and longer than T. rex, more than 45 feet long!