Re: Titanoceratops, giant ceratopsian from New Mexico

[tholtz@geol.umd.edu]

> From: Ben Creisler
> bh480@scn.edu
>
> In case this new advance publication paper has not been
> mentioned yet:
>
> Nicholas R. Longrich (2010)
> Titanoceratops ouranous, a giant horned dinosaur from the
> Late Campanian of New Mexico.
> Cretaceous Research (advance online publication)
> doi:10.1016/j.cretres.2010.12.007
[snip}

> At the end of the Cretaceous, 65.5 million years ago, the
> giant ceratopsids Triceratops and Torosaurus dominated
> North America's dinosaur fauna. The origins of these
> giant ceratopsids, the Triceratopsini, are poorly
> understood. This paper describes Titanoceratops ouranos,
> a giant ceratopsid from the late Campanian (73-74 Ma) of
> New Mexico, and the earliest known triceratopsin. The
> holotype was previously interpreted as an aberrant and
> exceptionally large specimen of Pentaceratops sternbergi,
> but the animal does not show the diagnostic features of
> Pentaceratops. Instead, cladistic analysis shows that
> Titanoceratops is the sister taxon of a clade formed by
> Eotriceratops, Triceratops, and Torosaurus. With an
> estimated mass of 6.5 tons, Titanoceratops is the largest
> dinosaur known from the Campanian of North America, and
> rivaled Triceratops in size. The recognition of
> Titanoceratops suggests that giant chasmosaurines evolved
> once, among the Triceratopsini, and that the group
> evolved large size five million years earlier than
> previously thought. The giant horned dinosaurs probably
> originated in the southern part of the North American
> continent during the Campanian but only became widespread
> during the Maastrichtian.

The specimen in question is the tremendous Oklahoma Museum of Natural
History skeleton labeled as (and frill restored after) Pentaceratops.

Cool paper. But I disagree that this is the largest North American
Campanian dinosaur: several hadrosaurids of this stage ("Lambeosaurus"
laticaudus, Hypsibema, Parrosaurus, etc.) indicate HUGE duckbills.

Interesting, though, that you get triceratopsin giants in the same region
in which some awfully large robust tyrannosaurines were present...