Dinosaur Frills
In his article about the newly discovered horned dinosaur, avaceratops, “Fossils Found of Small Type of Dinosaurs” (Dec. 19), Thomas H. Mauch II states that “previously discovered specimens (of horned dinosaurs) all had a pair of large openings” in their frills. This is not true, as the most famous horned dinosaur, the great triceratops, had a solid frill with no holes.
It is true that all the previously known Judith River formation ceratopsians (horned dinosaurs) had holes in their frills. Triceratops was one of the very last dinosaurs. Avaceratops looks very much like a juvenile triceratops, but that is unlikely. More likely is that avaceratops is the direct ancestor of triceratops.
DAVID A. LATHRAP
San Diego
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