Mr. Three Horn. . . except not.
The Ceratopsid family is divided in two subfamilies: the three-horned/long-frilled one and the single-horned/short-frilled one. note The ceratopsid of the image pertains to the first subfamily. Among three-horned/long-frilled ceratopsids you'll see Chasmosaurus, Pentaceratops & Torosaurus more often; less-frequently, Arrhinoceratops & Anchiceratops. About the single-horned kinds, other than the multi-spiked Styracosaurus the chances are to meet Monoclonius or Centrosaurus (which could actually be the same animal). Since the 1990s/2000s the no-horned Pachyrhinosaurus has also become a frequent sight. Some of them have even made occasional apparitions in fictional media other than in documentaries. The animal of the image is Titanoceratops.
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Non-Stock Ceratopsids
Small Unicorn-Dinosaurs: Avaceratops
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"Brachyceratops"
- There were other ceratopsids related to Styracosaurus other than Centrosaurus and "Monoclonius": for example, “Brachyceratops” ("short horned-face"). Found in the early XX century, it is known only from juveniles, and like “Monoclonius”, could just be a young stage of another ceratopsid. On the other hand, Avaceratops found in 1986 is a valid animal despite its small size — 3 m long, one of the smallest known members of the true ceratopsid family. This was a horned dinosaur of uncertain affinities (it was probably a basal centrosaurine), whose name means “Ava’s horned face”: its discoverer named it from his wife’s name. Even though resembles a miniature "Monoclonius", Avaceratops actually has a thing that makes it very similar to Triceratops: a round tubercled frill with no openings in it.
Horns from Canada: Albertaceratops
- Described in 2007, Albertaceratops ("Alberta horned face", originally confused with the similar Medusaceratops) was also probably a basal centrosaurine, but with a thing that surprised scientists: it had long frontal horns just like chasmosaurines like Triceratops, but also a small relief on its nose (rather than a proper horn), and two hook-like tubercles on its frill-top like a Centrosaurus.
Dawn Horns: "Eoceratops"
- One fragmentary ceratopsid which was often confused with Chasmosaurus in the past is "Eoceratops" ("dawn horned face"): this one was indeed one of the first true ceratopsids, living the same time of Chasmosaurus proper. A deceptively chasmosaurine-looking ceratopsian found in the late 1990s that roamed North America well before the others (in Middle Cretaceous) was actually more primitive to be a true ceratopsid, Zuniceratops.
Horned Hairdos: Einiosaurus & Achelousaurus
- Well, it’s true: ceratopsids have really bizarre hairdos. The most astonishing is, needless to say, that of Styracosaurus, with its multiple “horns” protruding from the frill. But some relatives made even their frontal horn a very odd-looking thing: for example, Einiosaurus procurvicornis. Discovered in 1994, it was initially believed a new Styracosaurus species, but with only two terminal spikes on its shield. The strange thing here is the nasal horn: strongly curved, thickened and pointing forwards (Einiosaurus procurvicornis means "buffalo-lizard with the horn curving forwards"), as the animal could signal its target like a pointer dog… more realistically, its shape could have been for ornamental purpose. Another related ceratopsid was also described in 1994: Achelousaurus ("Achelous lizard)": very similar of Pachyrhinosaurus, it shared with the latter the same thickened nose, but had a longer couple of frill-spikes and a less-complex frill than the pachyrhinosaur. Together, Einiosaurus and Achelousaurus are among the closest relatives of Pachyrhinosaurus, and they together make what is believed the most-recent & advanced centrosaurine subgroup: the Pachyrhinosaurini, while the most-recent & advanced chasmosaurine subgroup is the Triceratopsini (below).
An Unexpected Variety
- As recently as The New '10s, many new ceratopsid species have been described, with various frill-shapes, and the classification of the whole family has strongly improved since that. Rubeosaurus, for example, was very similar to Styracosaurus (and originally considered a species of the latter just like Einiosaurus above— some scientists still consider them to be the same), but with shorter frill-spikes and longer nasal horn, one of the longest among all ceratopsids. Diabloceratops ("devil horned-face") and Machairoceratops ("sword-horned face") coupled the pair of long frontal horns with two long frill-spikes, while the nose-horn was almost missing. Nasutoceratops ("nosed horned face") had long curved brow-horns and a prominent hornless nose, incidentally similar to the ancestral "missing link" Zuniceratops. One of the most spectacular is Kosmoceratops: similar to Chasmosaurus, it shows an entire set of curved hooks protruding from the frill-top like a fanciful fringe.
Asian Horned Dinosaur: Sinoceratops
- Sinoceratops ("Chinese horned face") was very similar to Centrosaurus; even though incomplete, it's the only confirmed ceratopsid found in Asia to date, and has even captured in 2018 the interest of the Jurassic Park producers who chose to show it in Jurassic World: Fallen Kingdom together with other more famous dinosaurs (initially the filmmakers thought about the more-known Pachyrhinosaurus in the role). With this exposure, it could even become a rare-stock dinosaur in the future. The same could happen about Nasutoceratops mentioned in the section above, chosen in 2022 by the Jurassic Park team as one of the new added dinosaurs within Jurassic World: Dominion.
The End Of The Line: The Triceratopsini
- For a long time, it was generally thought that Triceratops and its close relative Torosaurus were the last surviving ceratopsids, the only ones still around at the very end of the Cretaceous. As is usual with such things, recent discoveries have proven that this isn't true. All of these ceratopsians, however, belong to a group called the Triceratopsini, consisting of Triceratops and its very closest relatives. Since they were all very similar and lived at the same time, they can only be told apart by small details of their skulls. Ojoceratops was almost identical to Triceratops, but had a distinct squared-off frill not found in any of its relatives. It also lived farther south in what is now Texas and New Mexico. Even more similar to Triceratops was Eotriceratops, from Colorado and Montana. Although its name means "dawn Triceratops", and that dinosaur is often thought to be descended from it, the oldest fossils of Triceratops and Eotriceratops are about the same age, suggesting that they instead shared a common ancestor. Eotriceratops was also remarkable for its size— at 9 m long and weighing 8 tons, it was the second-largest ceratopsian ever, with only Triceratops itself being bigger.
Two-horned Trike?: Nedoceratops
- Triceratops, Torosaurus, Ojoceratops, and Eotriceratops were all fairly similar to each other: but there were also two members of the Triceratopsini that took things in a different direction. Nedoceratops hatcheri was unique in that it completely lost its nasal horn (indeed it was originally named "Diceratops", "two-horned face") and had odd pairs of small holes on each side of its frill unseen in other ceratopsids. However, it's also possible that it was simply an unusual Triceratops fossil. Regaliceratops ("royal horned face") was a "long-frilled" ceratopsid seemingly in the process of evolving into a "short-frilled" one, complete with a long nose horn and pointed frill-spikes like a crown (hence the name), resembling a Styracosaurus. In fact, it bears also a resemblance to the classic depiction of Agathaumas (see below).
Illustrious Unknowns: Ceratops & Agathaumas
- Who knows which is the official prototype of the Ceratopsid family? Well… just Ceratops. More precisely, Ceratops montanus ("mountain-living horned face"). Found by Marsh during the Bone Wars, it was his first horned dino, but has left only a fragmentary skull. Despite being the first Ceratopsid to be discovered, it's seen as largely insignificant simply because those fossils are so fragmentary that it would be impossible to ever confidently identify any more complete skeleton as belonging to Ceratops. It could be Chasmosaurus or something else, and has been largely ignored by everyone. Not the same about "Agathaumas sylvestris" (meaning "great wonder of the forests"). This animal was also found during the “wars”, this time by Cope; only some pieces of skeleton are known but not skulls, and since non-cranial remains are not diagnostic enough, Agathaumas is impossible to describe. Many suspect it’s only a Triceratops individual. And yet, it has had a famous appearance in the 1925 movie version of "The Lost World" (one of the first apparition of dinosaurs in cinema), in which it was portrayed with a Triceratops look. That apparition made it rather popular at the time, but now has got quite forgotten except among old-movies lovers.
