ceratopsinae

Chasmosaurinae

Chasmosaurinae (also sometimes Ceratopsinae) includes, as described before, ceratopsids with prominent brow horns, short nose horns, long squamosals, and a projection in the front of the nasal fenestra. Chasmosaurines tend to larger than centrosaurines, and are the only ceratopsid group known to have made it to the end of the Mesozoic. More derived members tend to have smaller parietal fenestrae (those big holes in the frill).

Chasmosaurinae: For convenience, these are all listed alphabetically.

Taxon or Taxa:		Time/Place:	Comments:
Agujaceratops mariscalensis Lucas, Sullivan, and Hunt, 2006 (originally Chasmosaurus mariscalensis [Lehman, 1989])		late Campanian (LK) of Texas	Originally assigned to Chasmosaurus, this species has been difficult to place because it is very similar to Pentaceratops in some ways (although its frill is somewhat shorter and more erect than that of Pentaceratops), and was found far from the classic Chasmosaurus stomping grounds. Like Pentaceratops, there is a deep indentation on the rear bar of the frill. To be on the safe side, it was given its own genus.
Anchiceratops ornatus Brown, 1914		late Campanian (LK) of Alberta	Anchiceratops is rather modest in frill, especially when compared to the "chasmosaurinids". It has moderately-sized windows, with six short projections on the rear of the frill and two distinctive knobs of bone on the top surface of the frill, near the rear edge. There is an excellent postcranial skeleton that has long been assigned to this genus, although this is unsupportable based on the present body of knowledge. The skeleton has features suggestive of a semi-aquatic hippo-like lifestyle.
Arrhinoceratops brachyops Parks, 1925		late Campanian (LK) of Alberta	Arrhinoceratops is based on a skull from an old individual, which overall is similar to that of Triceratops. While the name claims this animal has no nose horn, it does have one.
Chasmosaurus: Lambe, 1914 (originally Protorosaurus Lambe, 1914)	C. belli (type) (Lambe, 1902 [originally Monoclonius])	early late Campanian (LK) of Alberta	C. belli was a common Judithian dinosaur, known for its unimposing brow horns. Chasmosaurus as a whole also has large epoccipitals (nodules of bone on the frill) at the top corners of the frill.
	C. irvinensis Holmes, Forster, Ryan, and Shepherd, 2001	early late Campanian (LK) of Alberta	From the uppermost "Judithian" comes this species. It is known from three skulls; distinctive features include no brow horns, a broad snout, smaller parietal fenestrae than other Chasmosaurus species, and an unusual configuration of epoccipitals (there appears to be 10, with the middle 8 flattened, curved forward and up, and fused to each other at the edges, forming a funky serrated leading edge to the back of the frill).
	C. russelli Sternberg, 1940	late middle Campanian (LK) of Alberta	C. russelli closely resembles C. belli, but has a Y-shaped rear parietal bar, and has three large epoccipitals along the rear bar of the frill. It also is larger and often has a large nasal horn. It too may fall within the variation of the type species.
Coahuilaceratops magnacuerna Loewen, Sampson, Lund, Farke, Aguillón-Martínez, de Leon, Rodríguez-de la Rosa, Getty, and Eberth, 2010		late Campanian (LK) of Mexico	Coahuilaceratops is the first named ceratopsian from Mexico. It is known from partial remains of at least two individuals (an adult and juvenile) from a bonebed, and is notable for its large thick brow horns. What is known of the frill suggests something on the lines of Agujaceratops or Pentaceratops, except with a couple of low knobs on the midline bar. It may be related to Anchiceratops and Arrhinoceratops.
Eotriceratops xerinsularis Wu X., Brinkman, Eberth, and Braman, 2007		middle Maastrichtian (LK) of Alberta	Eotriceratops is based on a partial skull and vertebrae from high in the Horseshoe Canyon Formation. The skull is quite a bit like that of Triceratops, except the frill is much thinner (unfortunately, it's not complete).
Medusaceratops lokii Ryan, Russell, and Hartman, 2010		middle Campanian (LK) of Montana	Well, this one had the community fooled for a while; the material it is based on was thought to belong to Albertaceratops, bearing as it does ostentatious parietal ornaments, albeit not quite the same. Albertaceratops had two grand Cape Buffalo-ish objects at the end of its frill, while Medusaceratops had a set of serial projecting curves or tabs, something like a series of breaking waves. Medusaceratops is the oldest named chasmosaurine
Mojoceratops perifania Longrich, 2010 (?Eoceratops)		late middle Campanian (LK) of Alberta	Mojoceratops is a good idea that is unfortunately stuck between two dictums: naming taxa from informative specimens, and remaining beholden to prior taxonomy. You see, Mojoceratops is intended to represent the long-horned Chasmosaurus specimens. In and of itself, this is a good thing, because those specimens were always ringers when stuck with other Chasmosaurus specimens. The problem is that there have already been two attempts to name long-horned chasmosaurs from the same rocks, and both have problems. The first was Eoceratops canadensis, which Lawrence Lambe had named back in 1902 as a species of Monoclonius. By 1915 he'd thought better of it, and came up with Eoceratops. The problem with the holotype is it belonged to a juvenile individual and is only partially complete, for the purposes of our exercise missing the parietal. The parietal is pretty much the only thing that really tells these animals apart at this time, with Mojoceratops having a Y-shaped bar sort of halfway between Agujaceratops and Chasmosaurus russelli. The second was C. kaiseni by Barnum Brown in 1933. This specimen would seem to be ideal, except for the fact it too is more or less absent the parietal. This fact was not appreciated until recently, when it was found that the specimen's parietal is actually made of plaster and modeled after Chamosaurus. So, now we have another long-horned chasmosaur, but this time it has the whole parietal, and as mentioned it's rather different from the parietals of contemporary chasmosaurines. Once it was decided to give the skull a new name, three options arose: resurrect Eoceratops, create a new genus with type species kaiseni, or make an entirely new taxon. You can make an argument for any of the three; personally, I dislike the Eoceratops argument the most because it relies on the least complete specimen and the one from a juvenile. I lean to the second, as the type of C. kaiseni does still have some parietal occipitals, and they don't quite fit Chasmosaurus, but they do look like Mojoceratops, but I digress. If you do opt to ignore the other two for the purposes of nomenclature, then what? The description of Mojoceratops opted to declare the others nomina dubia and assigned the specimens as provisionally Mojoceratops.
Nedoceratops hatcheri Ukrainsky, 2007 (Hatcher, 1905 [species name after Lull, 1905 (originally Diceratops)]) (?Triceratops)		late Maastrichtian (LK) of Wyoming	Nedoceratops (under the guise of Diceratops) was long considered to be a Triceratops individual, albeit a poorly preserved and probably pathological individual. It has since been reinterpreted as a close relative of Triceratops, but not the same, as shown by the small parietal windows. This animal may have descended from a close ancestor of Triceratops, or it might be the skull that spans the Triceratops-Torosaurus growth gap, if indeed they are the same thing. The name Diceratops is preoccupied by a hymenopteran insect (think wasps, bees, and ants) (Foerster, 1868; ironic since the researcher who brought this dinosaur back is named Forster [Cathy]), necessitating the change. Thus, a new name was required. Fittingly for the "two-horned-face," two names were published, one being Diceratus (Mateus, 2008), and the other being Nedoceratops, which had been missed by the English-speaking world until January 2009. Nedoceratops predates Diceratus, though, so that's the one that gets used.
Ojoceratops fowleri Sullivan and Lucas, 2010		early-middle Maastrichtian (LK) of New Mexico	Ojoceratops is based on a squamosal and known from a variety of skull elements. It appears to be distinct but some of its features are poorly known because of the incompleteness of the remains.
Pentaceratops sternbergi Osborn, 1923		early late Campanian (LK) of New Mexico	A large chasmosaurine with a large skull relative to that large body, Pentaceratops has one of the most impressive frills of any ceratopsid. Its frill is large and long but contains wide windows, and has an indentation on the midline, like those of Chasmosaurus russelli and Agujaceratops, which has two large epoccipitals projecting in and forward, and two smaller ones projecting down and over the frill for a very short distance. It holds the individual record for longest head for a land animal (one new specimen is over three meters long), but Torosaurus as a whole appears to show a longer average head.
Tatankaceratops sacrisonorum Ott and Larson 2010		late Maastrichtian (LK) of South Dakota	Tatankaceratops is a mini-ceratopsid, perhaps a meter long, but described as having mature features and differing from Triceratops young of that approximate size. There's something about it that I can't put my finger on; actually, there's something a bit like "Monoclonius" recurvicornis. Go figure.
Triceratops: Marsh, 1889 (?Nedoceratops, Torosaurus)	T. horridus (type) (Marsh, 1889 [originally Ceratops])	late Maastrichtian (LK) of Wyoming, Montana, S. Dakota, Colorado, Alberta, and Saskatchewan	Triceratops is easily within the top five of most famous dinosaurs. Its combination of large size, bony frill, and long, powerful brow horns has impressed itself upon generations of children, and its contemporary Tyrannosaurus rex provides high drama from the contest of the most powerful predator versus the most powerful herbivore. Its brow horns were well over a meter in length when sheathed with horn, and a row of epoccipitals around the outside of the solid, window-less frill would have given this animal a jagged-looking head. Although the frill was more likely for display than for defense (and could have had additional functions like thermoregulation, or even directing of sound to the ears), the horns would have been excellent defensive weapons, especially when powered by the elephant-sized animal. The horns may also have had thermoregulatory capabilities. At one time the overall shortness of the frill led many workers to classify Triceratops as a "short-frilled" ceratopsid, but it is more likely that the frill is actually secondarily shortened, with typically long chasmosaurine squamosals. At one time over fifteen species had been named, but most of these were later shown to be based either on variations within that which would be expected in a gregarious animal, including differences between sexes and ages, or preservational problems. Of the two commonly accepted species, T. prorsus is the more common species in northern faunas (and there may be more species in the relatively poorly-known Canadian material), while T. horridus is more common in more southerly formations. Over fifty skulls are known, but no complete skeletons have been found; all mounted Triceratops skeletons are composites. For example, the mount at the Science Museum of Minnesota, which is the world's largest Triceratops mount, is based on two similarly-sized individuals. Triceratops was the most common dinosaur of the Lancian age (as you can probably find out from any paleontologist who works in rocks of the latest Cretaceous of Montana, Wyoming, South Dakota, etc.), and may have been one of the very last to go extinct at the end of the Mesozoic. So, of course: the Triceratops-Torosaurus thing. 2010 has seen the publication of a study proposing that Torosaurus is the adult form of Triceratops. Under this hypothesis, the frill undergoes extensive remodeling to go from the familiar bone collar of Triceratops to the great fan-like thing adorning Torosaurus. It's an interesting concept, but I'm not convinced. Were they breeding before they acquired all of their adult characteristics? If so, why bother to go to the trouble of having the adult characteristics in the first place? (especially considering there would be no other chasmosaurine taxa around to create confusion come breeding and necessitate distinct characteristics.) Knowing that Triceratops is known from dozens of museum specimens and anecdotal reports of hundreds of specimens in the field, while Torosaurus is known from around a dozen skulls, it would give Triceratops a rather odd demographic structure: it's not rare for most individuals of a species to die young, but to have many of them reach "teenager" stage and then die, with only a few making it to adults, would be interesting. Finally, there is the frustration of not having much in the way of bridging the Triceratops-Torosaurus leap, except maybe Nedoceratops.
	T. prorsus Marsh, 1890
Torosaurus: Marsh, 1891 (?Triceratops)	T. latus (type) Marsh, 1891	late Maastrichtian (LK) of Wyoming, Montana, S. Dakota, and Saskatchewan	Torosaurus owns the distinction of having the one of the longest heads of any known land animal, sometimes the size of a compact car. Obviously a very large chasmosaurine, it was a less common contemporary of Triceratops. Because ceratopsid postcrania are so similar, and because complete Triceratops remains have not yet been discovered, some Triceratops mounts may incorporate Torosaurus material. Seven skulls are known for T. latus, although none of them is complete (it's a big weirdly-shaped object with a thin frill, after all). The frill is V-shaped, as opposed to the rounder, stockier frills of Triceratops and Nedoceratops. There appears to be a second species of Torosaurus in the known material, T. utahensis, which has a shorter frill. It is best known from more southern localities.
	T. utahensis (Gilmore, 1946 [originally Arrhinoceratops])	late Maastrichtian (LK) of Utah, Colorado, and Texas

Chasmosaurinae i.s.:

Taxon or Taxa:		Time/Place:	Comments:
?"Bison" alticornis (N.D.) Marsh, 1887		late Maastrichtian (LK) of Wyoming	This usually forgotten name is what Marsh initially named what possibly are remains (two horn cores) of Triceratops, thinking they came from a bison. It is now probable that they came from a chasmosaurine, but which one produced them is not discernable.
Polyonax mortuarius (N.D.) Cope, 1874		late Maastrichtian (LK) of Colorado	Polyonax is based on horn fragments and vertebrae. Not surprisingly, it is very obscure.
"Triceratops":	"T." galeus (N.D.) Marsh, 1889	late Maastrichtian (LK) of Colorado	This is an indeterminate chasmosaurine based on a nasal horn core.
	"T." ingens (N.D.) Lull, 1915	late Maastrichtian (LK) of Wyoming	"T." ingens is based on a partial skull and postcranium, neither of which allow it to be positively assigned to Triceratops proper.
	"T." sulcatus (N.D.) Marsh, 1890	late Maastrichtian (LK) of Wyoming	This animal is based on a partial skull.

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