Smallest fossil Triceratops yields clues to growth of huge dinosaur (cont.)

snuggly within protective bones not yet fused, so as to allow further brain growth. In the adult, the brain, about the shape and size of a small sweet potato, was completely encased in fused bones. The relative position of the bones of the braincase as the animal matured recapitulates the cranial evolution of Triceratops from a more basal ancestor, such as Protoceratops.
"The baby skull shows us how the bones that make up the skull actually grew and fit together, because we see the sutures and sutural surfaces, which were completely obliterated in the adults," he said.
Because of the good condition of the bones, which show no gnawing, Goodwin thinks the baby died and the skull was buried before it could be scavenged or the bones eroded away along an ancient stream.
"It's an incredible specimen, with beautiful preservation," he said. Goodwin and Horner also have made casts of the skull for the American Museum of Natural History and for Montana's Museum of the Rockies.

Goodwin continues his excavations in Montana, concentrating on the dinosaurs of the Lower Hell Creek Formation that are slightly older than the T. rex and Triceratops fossils from the Upper Hell Creek Formation. His coauthors on the new paper are William A. Clemens, a UC Berkeley professor of Integrative Biology and Museum of Paleontology emeritus curator, who opened up the Montana area for fossil exploration more than 30 years ago; field colleague Horner of the Museum of the Rockies at Montana State University in Bozeman; and Kevin Padian, UC Berkeley professor of Integrative Biology and Museum of Paleontology curator.

Note: The baby Triceratops skull is the cover article in the March issue of the Journal of Vertebrate Paleontology: Goodwin, M.B., W.A. Clemens, J.R. Horner, and K. Padian. 2006. The smallest known Triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny. Journal of Vertebrate Paleontology 26(1):103-112.

May, 2006