centrosaurinae – Page 2 – Nix Illustration

Ceratopsian Month #14 – Wendiceratops pinhornensis

Wendiceratops (“Wendy’s horned face”) was one of the older known centrosaurs, living about 79 million years ago in Alberta, Canada – but it had a slightly higher position in the evolutionary tree than more basal forms like Xenoceratops, indicating just how incredibly quickly the early ceratopsids diversified.

Partial remains of several individuals have been found, representing both adults and juveniles, with an estimated full size of around 6m long (19′8″).

It had forward-curving frill spikes, similar to those of its close relative Sinoceratops, and a large nose horn. The size of its brow horns are unknown, so the ones seen in this reconstruction are based on the fairly well-developed horns of other similarly-aged centrosaurs.

Ceratopsian Month #13 – Sinoceratops zhuchengensis

Sinoceratops (“Chinese horned face”) was the first and only ceratopsid known from China, and possibly also the only one known from the entirety of Asia – depending on whether Turanoceratops counts as a true ceratopsid or not.

Discovered in the Shandong province, it dates to about 73 million years ago and was one of the larger centrosaurs at an estimated length of at least 6m (19′8″).

It had a well-developed nose horn and highly reduced brow horns, and forward-curving spikes around the edge of its frill that gave it a crown-like appearance. Uniquely for a ceratopsid, it also had some protruding bumps just below the spikes, creating a second row of ornamentation.

The presence of Sinoceratops in China shows that at least one lineage of centrosaurs dispersed across to Asia in the Late Cretaceous, but they seem to have been quite rare animals on that side of Beringia. While other dinosaur groups such as hadrosaurs and tyrannosaurs seemed to do just fine on both continents, something prevented the ceratopsids from being nearly as prolific as their North American relatives.

Ceratopsian Month #12 – Albertaceratops nesmoi

As its name suggests, Albertaceratops (“Alberta horned face”) was discovered in Alberta, Canada. Living around 77 million years ago, it’s known from an almost complete skull and would have had an estimated full body length of about 5.8m (19′).

It had fairly long brow horns and a boss-like nasal horn, similar to the arrangement in Xenoceratops, with a pair of large curving hook-shaped spikes at the top of its frill.

Some similar fossil remains found in Montana, USA, were attributed to Albertaceratops, but later studies showed that they actually belonged to a completely different ceratopsid – a chasmosaur eventually named as Medusaceratops.

[2018 update: Medusaceratops wasn’t actually a chasmosaur, but a centrosaur closely related to Albertaceratops!]

Ceratopsian Month #11 – Xenoceratops foremostensis

Xenoceratops (“alien horned face”) was one of the earliest centrosaurs known from Canada, discovered in Alberta and dating to about 80-78 million years ago – very similar in age to the more southern Diabloceratops.

It’s estimated to have been around 6m long (19′8″), and although the known fragmentary fossil material doesn’t include much of its face, there’s evidence of it having fairly long brown horns and a long low boss-like nasal horn.

It a had a pair of forward-pointing knobs and a pair of large spikes at the top of its frill, but the exact number and arrangement of the rest of its ornamentation isn’t clear. This particular image is based on Scott Hartman’s “best guess” Xenoceratops skeletal, but other reconstructions vary.

Ceratopsian Month #10 – Nasutoceratops titusi

The second centrosaur discovered in the southern portion of Laramidia, Nasutoceratops (“large-nosed horned face”) lived 75 million years ago in Utah, USA. It would have measured around 4.8m long (15′8″), and had very long horns, curving out to the sides and then twisting forwards into a shape that convergently resembles those of modern cattle.

It appears to have been part of a unique side branch of the early centrosaurs known as the Nasutoceratopsini, which had long brow horns, small nose horns, and only modestly decorated frills compared to their other relatives. This group also includes representatives from further north such as Avaceratops and several other still-unnamed specimens.

Its snout was short and deep, with an unusually huge nasal cavity – even for a ceratopsid – and shows evidence of pneumatic air sacs. Skin impressions were also found around its left shoulder, showing a pattern of 1cm (0.4″) hexagonal scales surrounded by smaller triangular scales.

Ceratopsian Month #09 – Diabloceratops eatoni

At this point in ceratopsian evolution we’ve reached the ceratopsids – the big, elaborately horned and frilled group that includes famous names like Triceratops and Styracosaurus. First evolving from their smaller North American ancestors around 90-80 million years ago, these dinosaurs rapidly diversified and developed a huge variety of different head ornamentations during the last 20 million years or so of the Cretaceous.

Here the family tree gets a little more complicated, with two major subdivisions of the ceratopsids splitting off from a common ancestor: the centrosaurs and the chasmosaurs. We’ll be focusing on the centrosaurs to start off, and moving on to chasmosaurs later in the month.