A giant duck with 1,000 teeth in the mouth.
The hadrosaurs commonly shown in media are usually North-American. Other than the four most known kinds, aka Parasaurolophus, Edmontosaurus, Maiasaura, and Corythosaurus (the animal of the image), other "duck-billed dinosaurs" that have been quite common are: Hadrosaurus (the official but fragmentary prototype of the family), Kritosaurus (whose portrayals actually are based upon another relative, Gryposaurus), Saurolophus (often confused but not-related with Parasaurolophus), and Lambeosaurus (this one may get confused with Corythosaurus). All them have even made occasional apparitions in films, novels, and TV programs. Since the 1990s Hypacrosaurus has also began to show up with a certain frequency. Among Asian kinds the gigantic Shantungosaurus and the "unicorn" Tsintaosaurus are those most portrayed, together with the Asian species of Saurolophus.
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North & South American Hadrosaurs
Bone-Wars Duckbills: Claosaurus
- After Leidy described Hadrosaurus in 1858 as a generic Iguanodon-like animal, then Edward Cope and Othniel Marsh described for the first time hadrosaurians as “duck”-headed dinosaurs in the following 1870s/1880s. Cope described the popular “Trachodon copei” (and also the enigmatic Pteropelyx and the teeth of "Cionodon" and "Diclonius"); Marsh a much more obscure animal than the "trachodont": Claosaurus agilis, a fragmentary animal which is worth of note both because was one third long than most other hadrosaurs, and because it was traditionally believed the most primitive North American duckbill. After its description, Claosaurus agilis ("agile broken lizard", because of its incompleteness and its slenderness) was involved in the incredible "Trachodon"/Anatosaurus/Edmontosaurus/"Anatotitan" taxonomic tangle, and today is often regarded as a close hadrosaur-ancestor but still not a proper hadrosaur.
The Lophus Family: Prosaurolophus
- “Loph-” is a common particle among hadrosaurian names (and theropodian as well: think about “Dilophosaurus”…); this is indeed the Greek for crest. Other than Saurolophus and Parasaurolophus, there is also a third similarly-named hadrosaur, Prosaurolophus, which means “before Saurolophus” (and was probably related with it). Another is Brachylophosaurus (“short crested lizard”, maybe closer to Maiasaura), and still another is the small Lophorhothon ("crested nose"). The latter was once thought a juvenile Prosaurolophus; today is generally regarded as a pre-hadrosaur like Claosaurus. The first two examples are small, primitive North American true hadrosaurs found some years after Saurolophus but with inconspicuous crests similarly to Maiasaura. From North America come other two very recent and interesting discoveries (both belonging to the "hollow-crest" subfamily of hadrosaurs): Angulomastacator (lit. "angular chewer") with its curious jaws curving below, maybe to better take vegetation on the ground; and Velafrons (lit. "sail front") which looks rather like the Asian Olorotitan.
Headbutting Hadrosaurs?: Brachylophosaurus
- Despite having left abundant remains, their comparatively modest appearance makes Prosaurolophus & Brachylophosaurus rare sights in media — even though Brachylophosaurus has recently given us some spectacular fossils which might make it more widely-known: among these, a true “mummy” (named "Leonardo"), just like Edmontosaurus. Some scientists have hypothesized that Brachylophosaurus and Maiasaura used their thickened cranial crest for headbutting their rivals, a bit like what has traditionally been said about pachycephalosaurians: like the latter, this hyp is not demonstrated — even though some hadrosaurian ribs fractured and then hailed could be a possible proof of this behavior.
The Heirs of Kritosaurus
- Most hadrosaurs have been described in Alberta at the beginning of the XX century, in the second memorable “Dino-Rush” led in North-America. Among them, other than Parasaurolophus, Corythosaurus, Saurolophus, and Kritosaurus, there's one that has traditionally been ignored for decades by media: Gryposaurus notabilis ("noble hooked lizard"; not "noble griffin lizard" as usually said). Found in 1910, it owes its name from its hump-like nose: but its bumped skull was before the 1990s mostly attributed to the genus Kritosaurus. After that date, it was confirmed that the skull belonged to it instead. Other two new discovered hadrosaurs in western USA also show bumped heads, the Native American-sounding Anasazisaurus and Naashoibitosaurus, both known from only their skulls.
Emigrating in South America: Secernosaurus
- Some “Kritosaurus” remains have been described in South America, but they belong to the genus Huallasaurus, described in 2022. These remains were once believed to be from the animal that was for long time the only surely-valid South American hadrosaur: Secernosaurus ("separated lizard"), a small primitive duckbill which is likely a migrant of North American origins. This one and Huallasaurus could have been among of the favorite prey for the famous bull-horned Carnotaurus. The secernosaur has been portrayed as a carnotaur prey in illustrations. Another South American hadrosaur described in 2017 owes its name from famous Argentinian paleontologist José Bonaparte, Bonapartesaurus. All three genera belong to the same hadrosaur subgroup, the Kritosaurines, and arguably shared a common North American ancestor.
Asian & European Hadrosaurs
Manchurian Dinosaur: Mandschurosaurus
- Everywhere seems to have started with a large ornithopod. We have Hadrosaurus in the USA, Iguanodon in Europe; and what about China? Here, the role was assumed by a little-known hadrosaur, Mandschurosaurus - “Mandschuria” is the German graphy for Manchuria, the northern Chinese region where the find was made in 1930. This is not a mere case however: remember ornithopods were the “antelopes” of their time... and we know well antelopes are the most numerous large mammals in Africa. Then, several others followed: the most debated has been Tsintaosaurus spinorhinus ("spine-nosed lizard from Tsing-tao", the capital city of Shandong). See Stock Dinosaurs (Ornithischian Dinosaurs) for it.
Beetween Russia and China: Olorotitan
- Some hadrosaurs traditionally considered similar to Corythosaurus are known from Asia: Barsboldia (named after Mongolian scientist Rinchen Barsbold, and recently reclassified as more related to Edmontosaurus than to Corythosaurus), Jaxartosaurus (from the Jaxartes river in Central Asia, a Corythosaurus relative but maybe too basal to have already developed a prominent crest), and Nipponosaurus ("Japanese lizard"), the latest two being found in the ex-Soviet Union. The formerly-largest country in the world has surprisingly left few dinosaurs compared with USA, Canada and China: many of them are hadrosaurs. In the 1990s-2000s, two brand new crested hadrosaurs were found near the Amur river which divides Russia from China: the meaningfully-named Amurosaurus and the spectacular hatchet-crested Olorotitan ("titanic swan": a clear reference to Anatotitan the "titanic duck"). While the amurosaur's crest is not known from fossils, Olorotitan revealed a totally new kind of crest, reminiscent of an upright axe pointing backwards. Olorotitan, together with Secernosaurus above and Telmatosaurus below, shows up in 2022' BBC documentary Prehistoric Planet. Similar olorotitan-looking appendages were later found in other dinosaurs of the Hadrosauridae, for example the North American Velafrons ("sail-front") and, more recently, even in the classic allegedly "unicorn duckbill" Tsintaosaurus.
Parasaurolophus of the East: Charonosaurus
- If you see a “trumpet”-crested hadrosaur in books or documentaries, be sure it’s a Parasaurolophus… unless you’re watching a work made after year 2000. Indeed, in that year a very Parasaurolophus-like hadrosaur was discovered in the same Amur site cited above: Charonosaurus ("Charon lizard"). This one was also bigger than its North-American cousin… only, its skull is incomplete, with only the base of the crest preserved; the shape of the remaining crest is only a guess. Nonetheless, the discover of the “Amur hadrosaurs” has enhanced our knowledge of duckbills in general. Before that, the Asian were considered generally more primitive than the North-American ones. As we know their Asian counterparts, this is not true anymore. Among the latter, also described in the 2000s were the Saurolophus-like Kerberosaurus, the Corythosaurus-like Sahaliyania, and Wulagasaurus.
From Central Asia: Bactrosaurus
- Some other Asian hadrosaurs or pre-hadrosaurs were much more generically-looking than Tsintaosaurus or Saurolophus: for example, Bactrosaurus ("lizard from Bactria", an ancient Central Asian region), one of the smallest duckbills known – only 6 m long. Discovered in China and in Russia, Bactrosaurus is traditionally regarded as one of the earliest lambeosaurine hadrosaurs because of its tall neural spines, or a middle-way between crested and crestless hadrosaurs. It had any crest on its head, and was still rather Iguanodon-like in look apart from the flatter beak – remember hadrosaurs are just very specialized iguanodontians phylogenetically speaking. But recent research has re-classified the bactrosaur outside Hadrosaurids proper. Some suspected it had small thumbspikes like those of other two pre-hadrosaurs, Ouranosaurus and Probactrosaurus (see just below).
Hadrosaur or Iguanodont?: Probactrosaurus
- The bactrosaur's legacy with Iguanodon is confirmed by Probactrosaurus, an Early Cretaceous ornithopod which, like Bactrosaurus was still not a proper hadrosaur, but was going to become such. Also Asian, it was very similar-looking to Bactrosaurus apart for a more rounded, less flattened muzzle, to the point to have given in The '70s a concrete clue about hadrosaurs’ ancestry (its name just means “before Bactrosaurus", because was slightly earlier than it but lived about in the same places). A very primitive hadrosaur or hadrosauroid from China is Gilmoreosaurus, which was smaller and slimmer than most hadrosaurs - recalling the North American Claosaurus. Other more fragmentary Asian duckbills include Arstanosaurus (once often confused with a ceratopsian) and Microhadrosaurus, lit. "small Hadrosaurus": once believed the smallest hadrosaur, but today it's known its fossils are juveniles.
Ancient Mediterranean: Telmatosaurus
- While most Asian dinosaurs are known from China and/or Mongolia, several duckbills or pre-duckbills were found in unusual countries such as the former USSR, ex. Bactrosaurus, Jaxartosaurus, and Aralosaurus (found next to the drying Aral Sea), and even in Japan (Nipponosaurus). Nippon or Nihon is the proper name of Japan, but actually Nipponosaurus was dug out in the Russian island of Sakhalin, but at the time of its finding (1934) this island was Japanese. Dinosaurs from actual Japan have been discovered only since the 1980s, and officially named only since the 1990s, ex. the theropods Wakinosaurus and Fukuiraptor, and the yet-undescribed hadrosaur "Hironosaurus". But there are also few hadrosaurs that have been found in Europe. The traditionally most-known is Telmatosaurus; another more fragmentary is Orthomerus. A smallish animal known from incomplete fossils, Telmatosaurus ("marsh-living lizard") is one of the several dinosaurs discovered in Late-Cretaceous Central Europe from France to Romania, along with Struthiosaurus, Magyarosaurus, Rhabdodon, and the primitive flightless bird Balaur. At the time most Europe was covered by the ancient inner-ocean Tethys (considered the ancestor of the Mediterranean, Black, and Caspian Seas), and small islands were the only pieces of dryland Telmatosaurus could have lived on. How it was able to reach these islands from Asia is still a mystery.
In Southern Europe: Tethyshadros
- In year 2009 the ornithopod Tethyshadros insularis ("island-dwelling hadrosaur from Tethys") was found in Northern Italy, precisely near the border with Slovenia (in the northernmost part of the former Yugoslavia); this is now the most complete European duckbill, even though Telmatosaurus appears more widespread in European fossil sites. Recent research, however, put even these two dinosaurs slightly outside the Hadrosaur crown group. In 2021 new findings about Tethyshadros have been described in the same location between Italy and Slovenia. Other two recently found duckbills in Spain, Koutalisaurus and Pararhabdodon, seem real hadrosaurs, maybe related with Tsintaosaurus.
