The Ceratopsid family is divided in two subfamilies: the three-horned/long-frilled one and the single-horned/short-frilled one. note 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.
- As a whole, Centrosaurs - Styracosaurs - Pachyrhinosaurs - Chasmosaurs might be considered the predecessors of Triceratops. The latter was elephant-sized, lived 70-65 million years ago just before the mass-extinction and shared its world with the mythical Tyrannosaurus rex; the former were rhino-sized or only a bit larger, lived 80-70 million years ago, and had to be pleased with its humbler relatives (Albertosaurus, Gorgosaurus, and Daspletosaurus). If you see a battle between a tyrannosaurid and a ceratopsid in some CGI documentary, expect to see more frequently Triceratops instead of the less-gigantic CentroStyracoPachyrhinoChasmosaurs and other less-known contemporaries, like Anchiceratops and Arrhinoceratops. The first one was very Chasmosaurus-like with a similar angular frill but entirely smooth laterally and entirely tubercled at its top. The second has a similar ornamentation but a shorter frill. Anchiceratops ("almost-'Ceratops'", see below) is nonetheless abundant in fossil record, while Arrhinoceratops is a rarer find; when discovered was initially thought to lack the nasal horn, hence its prefix arrhino which means no horns on the nose. Anchiceratops shouldn't be confused with Anchisaurus, an ancestral sauropod-relative famous for being the first-found North-American dinosaur — and according to some, the real inspirer of the character of Dino, the Flintstones' pet dinosaur.
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.
- There were other ceratopsids related with 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 affinites (it was probably a basal centrosaurine), whose name means Avas horned face: its discoverer named it from his wifes 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. Described in the 2000s, 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 one (rather than a proper horn), and two hook-like tubercles on its frill-top like a Centrosaurus.
- Well, its 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.
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), but with shorter frill-spikes and longer nasal horn, one of the longest among all ceratopsids. Diabloceratops ("devil horned-face") and Machairaceratops ("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. While 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 productors who chose to show it in Jurassic World: Fallen Kingdom together with other more famous dinosaurs. Slightly before all these ones was described a more normal-looking ceratopsid, Eotriceratops ("dawn Triceratops", not to be confused with "Eoceratops"): extimated 11 meters long, it is one of the biggest ceratopsid known so far, as large as the largest Triceratopses.
- 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 its 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.