Eotriceratops

[triceratops83]

I was just wondering, with Nedoceratops, Ojoceratops, and Tatankaceratops all being thought of as synonyms of Triceratops, as well as the whole Torosaurus debate, why Eotriceratops is not considered a species of Triceratops. I read somewhere, that naturally, Greg Paul has tried to lump them together without support from other palaeontologists. Could Eotriceratops xerinsularis be an early form of Triceratops?

[Sim]

It has also been suggested that Ojoceratops is a synonym of the contemporary Eotriceratops, and that this animal is ancestral to Triceratops.

[stargatedalek]

Is it possible Eotriceratops was a "super-adult" Triceratops? If we work on the assumption Torosaurus was a close if not nearly direct ancestor of Triceratops could the positioning of the brow horns and blunter snout horn be features retained from Torosaurus?

All of this based on a reconstructed skull, since annoyingly I can't find any credible sources on how much is really known.

[soft tissue]

it's known from earlier strata than any known Triceratops, so probably isn't a hypermature adult. it is a basal triceratopsinin, and likely closely related to the direct ancestor of Triceratops (Wu et al., 2007]).

[CAWCarcharo]

According to some sources; Eotriceratops xerinsularis is bigger than Triceratops horridus and could be an older Adult Triceratops horridus from an early population of Triceratops horridus as Eotriceratops xerinsularis was dated to 70.6 to 66.043 Ma and Triceratops horridus is found around the same time and Eotriceratops xerinsularis was found in Alberta and Triceratops horridus remains have also been found in Alberta, so it is most likely that Eotriceratops xerinsularis is an old Adult Triceratops horridus though it apparently has the characteristically distinguishing features of the projection process above and behind the Nostril bone, a broader fenestra interpraemaxillaris lower level portion, elongated bases to the episquamosals, a proportionally elongated snout and some other minor Morphological features that differ it from Triceratops horridus. Interestingly though, I have to note that if we consider that the larger Eotriceratops xerinsularis evolved into the smaller Triceratops horridus and that in turn evolved into Triceratops prorsus; isn't there a strange correlation of Triceratopsini Dinosauria dwarfing from Species to Species in a 4.557 Ma time period?

[Dinoguy2]

According to some sources; Eotriceratops xerinsularis is bigger than Triceratops horridus and could be an older Adult Triceratops horridus from an early population of Triceratops horridus as Eotriceratops xerinsularis was dated to 70.6 to 66.043 Ma and Triceratops horridus is found around the same time and Eotriceratops xerinsularis was found in Alberta and Triceratops horridus remains have also been found in Alberta, so it is most likely that Eotriceratops xerinsularis is an old Adult Triceratops horridus though it apparently has the characteristically distinguishing features of the projection process above and behind the Nostril bone, a broader fenestra interpraemaxillaris lower level portion, elongated bases to the episquamosals, a proportionally elongated snout and some other minor Morphological features that differ it from Triceratops horridus. Interestingly though, I have to note that if we consider that the larger Eotriceratops xerinsularis evolved into the smaller Triceratops horridus and that in turn evolved into Triceratops prorsus; isn't there a strange correlation of Triceratopsini Dinosauria dwarfing from Species to Species in a 4.557 Ma time period?

I think you're taking the "bigger than" T. horridus factoid way too far. Note that we only have one specimen of Eotriceratops, and it is ever so slightly larger than the largest known T. horridus specimen. Furthermore, the largest known Triceratopsin specimen of all time is a T. prorsus (MWC 584), which is the last species, though it's not much different in size from the Eotriceratops. T. horridus, the middle species, seems slightly smaller on average, but that's probably only due to its much larger sample size dragging down the median.

If you actually look at all these skulls, rather than simply comparing numbers, you will see that they're all actually about the same size, with slightly longer or shorter frills. So there isn't any "dwarfing" going on, just slight variation in shape and size between individuals and differences in skull proportions between species.



Looking only at the absolute largest known sizes, we have the earliest species, Eotriceratops,

[CAWCarcharo]

What you also have to consider is that MWC 7584 isn't a complete Specimen as the Skull doesn't have the Posterior of the Frill preserved so the size could be inaccurate and there are T. horridus Specimens that are as big or even slightly larger than some T. prorsus and vice versa; but fair enough on your point. But additionally, the Eotriceratops xerinsularis Holotype isn't complete or largely complete in key anatomical areas but it is proportionally larger that Triceratops.

https://www.researchgate.net/publication/233569630_A_new_ceratopsid_dinosaur_Ornithischia_from_the_uppermost_Horseshoe_Canyon_Formation_Upper_Maastrichtian_Alberta_Canada