Tag: ceratopsian

Ceratopsian Month #19 – Coronosaurus brinkmani

Coronosaurus (“crowned lizard”) was a very close relative of Centrosaurus – so close, in fact, that it was originally named as a second species of Centrosaurus itself, before being recognized as a separate genus a few years later.

Living around 77 million years ago, it was a medium-sized centrosaur about 5m long (16′4″). Multiple specimens are known from two bone beds in Alberta, Canada, with different ages represented. Juvenile Coronosaurus skulls looked very similar to juvenile Centrosaurus, only developing their own distinct ornamentation as they matured. 

It had a slightly backwards-pointing nose horn, brow horns that curved out to the sides, and a pair of downward-curving frill spikes. Uniquely among all known ceratopsians, it also had large irregular masses of short spikelets at the top of its frill forming a distinctive “crown”.

Ceratopsian Month #18 – Centrosaurus apertus

Centrosaurus (“pointy lizard”) lends its name to the entire centrosaur group of ceratopsids – and also to a major branch within the centrosaur evolutionary tree, the Centrosaurini.

Known from Alberta, Cananda, around 76-75 million years ago, it grew up to about 6m long (19′8″) and is known from a huge number of fossils from thousands of individuals in gigantic bonebeds. These seem to represent enormous herds, making Centrosaurus one of of the most common dinosaurs in the region at the time.

It had a single large horn on its nose, which started off pointing backwards as a juvenile and changed shape as it grew, gradually hooking forwards. Two especially long spikes at the top of its frill curved strongly downwards, while its brow horns were reduced to small points.

Skin impressions are also known from one specimen, preserving a region around the right hip and upper leg, showing a pattern of small polygonal scales interspersed with larger rounded scales.

Ceratopsian Month #17 – Pachyrhinosaurus canadensis

Pachyrhinosaurus (“thick-nosed lizard”) has become one of the more recognizable ceratopsian names in the last couple of decades, but its remains have actually been known for over 70 years, first discovered in the mid-1940s.

Three different species have been named within the genus, all living about 74-69 million years ago in Alberta, Canada, and Alaska, USA. The type species P. canadensis dates to roughly the middle of that time span, at an age of around 71 million years.

It was one of the largest of the centrosaurs, with the biggest specimens estimated to have measured up to 8m long (26′). Thousands of fossils have been found in a bone bed that seems to represent a mass mortality event – possibly a herd caught in a flash flood – with ages ranging from juveniles to adults.

Rather than horns, Pachyrhinosaurus had huge flattened bosses on its skull, which nearly grew together into a single large mass in both P. canandensis and the younger species P. perotorum. The older species P. lakustai instead had more separated bosses and a “unicorn horn” on its forehead.

(I’m also hardly the first person to speculate about fluffy pachyrhinosaurs, but since they lived in a chilly Arctic environment it’s certainly an interesting possibility.)

Ceratopsian Month #16 – Achelousaurus horneri

Achelousaurus (“Achelous lizard”) seems to have been a transitional form among the Pachyrhinosaurini. While slightly more basal members like Einiosaurus had well-developed nose horns, and the later Pachyrhinosaurus had enormous flattened nasal bosses, Achelousaurus was somewhere in-between.

Living in Montana, USA, about 74 million years ago, it reached sizes of about 6m long (19′8″). Instead of horns, rough patches of bone on its skull supported bosses over its snout and eyes, which in life would have been covered by thick layers of keratinous skin.

Unlike adults, juveniles had small brow horns with bony cores which gradually developed into full bosses as they grew. It’s possible that the bosses of mature individuals were used for headbutting or ramming behaviors.

Ceratopsian Month #15 – Einiosaurus procurvicornis

Einiosaurus (“buffalo lizard”) was part of a branch of the centrosaurs known as the Pachyrhinosaurini, a group with especially elaborate nose ornamentation.

Living about 74 million years ago in Montana, USA, it’s known from hundreds of bones representing over fifteen different individuals of varying ages. It had little-to-no brow horns, and two long spikes at the top of its frill – but also one of the most unusual-looking nose horns of all the ceratopsids, curving strongly forward and downward into a large hooked shape.

The juvenile remains show evidence of very rapid growth during their first few years of life, only starting to slow down around age 3-5, suggesting that was the point they began to reach reproductive maturity. The largest specimens are estimated to have measured about 4.5m long (14′9″), although they appear to have been subadults who still hadn’t quite reached their full size.

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.