Ancient cousin of Triceratops highlights turnover among horned dinosaurs

May 31, 2013 by Eric Gershon
Ancient cousin of Triceratops highlights turnover among horned dinosaurs

(Phys.org) —The earliest known cousin of Triceratops and Torosaurus—the best-known horned dinosaurs—has been identified based on fossils from north central Montana, further underscoring the diversity of large, plant-eating horned dinosaurs among the fauna of western North America 66 to 80 million years ago.

By now, remains of at least 18 closely related dinosaurs from the region have been identified as , and Yale researcher Nicholas Longrich expects others will be discovered.

"We keep finding new species, because cerotopsids—horned dinosaurs—evolved so rapidly," said Longrich, the postdoctoral researcher who identified the latest addition to the family, Judiceratops tigris. "These species show up for just a couple million years, or even a far shorter time, before another species replaces it. As you move up into younger rocks or down into older rocks, you get new species and no longer see the old ones. There was a lot of turnover."

Longrich reports the details of his research in a paper published in the spring edition of the Bulletin of the Peabody Museum of Natural History.

Identified by analysis of skull fragments belonging to four previously collected specimens in the Peabody's collection, Judiceratops lived during the late , about 78 million years ago, or 12 million years before the more familiar Triceratops and Torosaurus. Judiceratops is the earliest known member of the chasmosaurines, a group of horned dinosaurs characterized by an enlarged frill on the back of the skull. It does not appear to be a direct ancestor of and , Longrich said.

Judiceratops was likely a large plant-eating dinosaur that fed on low-growing vegetation, such as , like other members of its family. It had two large horns over the brow and a smaller horn on its nose.

The three-horned Judiceratops differs from all other in the shape and arrangement of the on the edge of the frill, which are large and triangular toward the front, and low and blunt toward the back.

The ornate frills might have been a way for the dinosaurs to attract mates and intimidate rivals, Longrich speculates, as some birds (modern dinosaurs) do through elaborate plumage or song.

"These are very bold, conspicuous display structures," Longrich said of the frills, which might also have served a defensive purpose.

The name Judiceratops tigris refers to the site where the fossils were found—in the Judith River Formation of Hill County, Montana, northwest of Havre—and to the Greek words "ceras" (horn) and "ops" (face). Tigris is a nod to the Princeton researchers who originally found the fossils and eventually gave them to the Peabody Museum at Yale. (The tiger is Princeton's mascot.) The age of the river formation, combined with radiometric dating, helped determine Judiceratops' age.

In recent years Longrich has identified several previously unrecognized dinosaur and lizard species—including the Obamadon, Mojoceratops, and Leptorhynchos—generally through close examination of overlooked fossils in existing museum collections.

Explore further: Scientists seek more tombs at ancient Greek site

Related Stories

Newly discovered dinosaur likely father of Triceratops

Jan 31, 2011

Triceratops and Torosaurus have long been considered the kings of the horned dinosaurs. But a new discovery traces the giants' family tree further back in time, when a newly discovered species appears to ha ...

Primitive birds shared dinosaurs' fate

Sep 19, 2011

A new study puts an end to the longstanding debate about how archaic birds went extinct, suggesting they were virtually wiped out by the same meteorite impact that put an end to dinosaurs 65 million years ...

Meet Xenoceratops: Canada's newest horned dinosaur

Nov 08, 2012

Scientists have named a new species of horned dinosaur (ceratopsian) from Alberta, Canada. Xenoceratops foremostensis (Zee-NO-Sare-ah-tops) was identified from fossils originally collected in 1958. Approximately 20 feet l ...

New bony-skulled dinosaur species discovered in Texas

Apr 19, 2010

Paleontologists have discovered a new species of dinosaur with a softball-sized lump of solid bone on top of its skull, according to a paper published in the April issue of the journal Cretaceous Research.

Recommended for you

Laser from plane discovers Roman goldmines in Spain

Nov 20, 2014

Las Médulas in León is considered to be the largest opencast goldmine of the Roman Empire, but the search for this metal extended many kilometres further south-east to the Erica river valley. Thanks to ...

Ancient New Zealand 'Dawn Whale' identified

Nov 18, 2014

University of Otago palaeontologists are rewriting the history of New Zealand's ancient whales by describing a previously unknown genus of fossil baleen whales and two species within it.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

philw1776
1 / 5 (1) May 31, 2013
The high rate of speciation and brief existence is reminiscent of hominid evolution the last few million years. Far more #s of horned dinos and species.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.