Ceratopsian Month #31 – Triceratops horridus
Of course we’re ending this month with the most famous of the ceratopsians, the dinosaur superstar Triceratops (“three-horned face”).
Dating to the very end of the Cretaceous, between 68 and 66 million years ago, it was the most common ceratopsid in North America at the time, ranging from Alberta, Canada down to Colorado, USA. Two different species are currently recognized within the genus – T. horridus in the older part of that time range, and T. prorsus in the younger rock layers.
It was one of the very largest ceratopsians, with the biggest individuals reaching sizes of about 7.9-9m (26’-29’6”). Many fossil remains have been found, representing growth stages from juveniles to adults (with Torosaurus speculated to represent the most fully mature individuals), and a lot of variation in exact horn and frill shape is seen between different skulls. One specimen nicknamed “Yoshi’s trike” had some of the longest brow horns of any ceratopsid, with the bony cores alone measuring 1.15m long (3′9″).
Unusually for a chasmosaur, it had a very short and solid frill with no weight-reducing holes, suggesting the structure served a much more defensive role than in other ceratopsids. Damage to the frill bones in some specimens appears to have been caused by other Triceratops, giving support to the popular depiction of these dinosaurs locking horns in fights.
Tooth-marks from the equally-famous Tyrannosaurus have also been found on Triceratops bones. Not all of these predator-prey encounters were fatal, however, with some specimens showing evidence of healing around the damaged areas.
Fossilized skin impressions show that Triceratops was scaly – but with scales unlike those of any other known dinosaur, showing large polygonal scales interspersed with even bigger knobbly scales with odd “nipple-shaped” conical projections in their centers. It’s possible that the “nipples” may have supported larger structures (as I’ve illustrated above), but unfortunately no official scientific description of this skin has been published yet and details about it are vague.
And with this final entry, here’s the chasmosaur evolutionary tree:
