Dinovember 2016, Day 5

How many species do you see here, one or two? And are they Triceratops or not?

Name: Torosaurus latus
Meaning: the intended etymology is not totally clear, but it probably means 'wide perforated reptile', in reference to the broad frill and large openings in it; Torosaurus does NOT mean, as is often translated, 'bull reptile'
Time: Late Cretaceous, c 66 million years ago
Place: Western US and Saskatchewan
Size: about 7-9 metres (23-29.5 feet) long; weighed probably 8-13 tonnes (8.8-14.3 tons)
Type of Dinosaur: triceratopsin chasmosaurine (advanced three-horned 'long-frilled' horned dinosaur)

You may be familiar with Torosaurus because of their role in the famous BBC speculative documentary Walking With Dinosaurs in the episode that focused on the extinction of the nonavian dinosaurs (although Torosaurus seem to have already disappeared shortly before the final extinction), or more likely because of the debate over the last few years as to whether Torosaurus are a distinct animal or just the fully-mature form of Triceratops, and the absolutely awful pop-science 'journalism' that blatantly misleads with clickbaity headlines and shows a profound lack of even attempting to understand questions of classification associated with that debate.

While there's too much to say about that for me to cover it here, I'll just say the evidence really seems to be on the side of 'Torosaurus are their own unique taxon, but are closely related to Triceratops,' rather than 'Torosaurus are just old adult Triceratops' - as I said, there's a lot involved here and if you want to know more, look it up! There's a lot to read about it.

In this drawing, I feature two Torosaurus, and you can see that even within Torosaurus, classification could be questionable. Notice the differences between these individuals; the one at the front is based on ANSP 15192 while the bigger one at the back is based on the huge Museum of the Rockies specimens. The horns are shaped considerably differently, especially the nose horn - pointy and forward-angled in ANSP 15192, as opposed to a massive, low, blunted boss on the MOR skulls. Details of the brow horns, frill, and snout differ too, and I've heard that despite their size the MOR Torosaurus show signs of still having a fair bit of growing up to do. Even though it's well known that details like horn and frill shape can vary a lot between individual horned dinosaurs, something about the MOR specimens in comparison with many other Torosaurus latus makes me think we might be looking at a two different species here.

Anyway, this has gone on long enough for what is supposed to be a quick picture-led post. tl;dr: Torosaurus probably aren't the same as Triceratops, and some of the specimens called Torosaurus latus might be something else.

Come back tomorrow for... SAUROPODS! FINALLY!