Prehistoric Life/Dinosaurs/Hadrosaurs

All began with a duckbill: Hadrosaurus

• Surprise: “hadrosaur” not only means one precise group of related dinosaurs, it also indicates a single genus of duckbill: Hadrosaurus. But its importance is almost-entirely historical. The very first dinosaur ever identified as such in America (and outside Europe) from more remains than simple isolated teeth (year 1858), like most early discoveries Hadrosaurus has a generic-meaning name, “heavy lizard”; and, oddly for an US dinosaurs, was found in New Jersey – since dino-discovers in Eagle Land began in the East Coast while the upcoming “Bone-Wars” were “fought” in the West, one could say about a veritable Dino-Rush. Hadrosaurus was already recognized as an Iguanodon relative, but the latter was still depicted as totally-quadrupedal at the time. Hadrosaurus remains, though very incomplete, cleary showed an at least partly bipedal creature. Joseph Leidy (its namer) was the first paleontologist to have described a dinosaur in the classic upright posture: a revolutionary idea at the time, which became more popular later, expecially after the countless portraits of another guy, guess what. Hadrosaurus has also the distinction to have been the first dinosaur ever mounted in a museum. However, the original bipedal posture has changed from upright to horizontal since the 1970s. Sadly, Hadrosaurus skull was pratically unknown, so Leidy didn’t understand to be in front of “the first duckbill discovered”. Despite this, some books have portrayed Hadrosaurus with a bump-nosed head for some reason. Actually, Hadrosaurus is so incomplete that it could be a synonym of another kind of hadrosaur, thoogh a recent study seems not to agree. It was Edward Cope and Othniel Marsh who first described hadrosaurs as “duck”-headed animals. Cope described the popular “Trachodon” (now Anatotitan), Marsh a much more obscure animal, Claosaurus, a fragmentary animal which is worth of note both because was one third long than most other hadrosaurs, and because is perhaps the most primitive North American duckbill. After its description, Claosaurus was involved in the incredible "Trachodon"/Anatosaurus/Edmontosaurus/Anatotitan taxonomic tangle.

A decayed nobleman: Kritosaurus and Gryposaurus

• However, 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, one of the most historically relevant has been Kritosaurus. In old books, it used to be shown as one of the prototypical hadrosaurs, along with “Anatosaurus”, Parasaurolophus, Corythosaurus, and Saurolophus, and their skulls were often shown together making a sorta Five Hadro Band. This “band” has also appeared once in cinema: in 1940, the “Rite of Spring” of Fantasia portrayed all but one member, but the missing one was Saurolophus, not Kritosaurus. More precisely, the kritosaur is the one with the bulged-nose: this sort of Roman-nose has often been cited as the origin of its name, “noble lizard” (though the real meaning of “krito” is uncertain). Then, Science Marches On hit hard our Kritosaurus. Recent studies made since the 1990s showed that its first skull with the classic bulge actually pertained to another duckbill, the much more obscure Gryposaurus (incidentally its name, “Griffin lizard”, is also a reference to this nasal relief). To worsen things, Kritosaurus has revealed to be a wastebasket-taxon, and most of its former remains are now of uncertain attribution. Today, we even don’t know if it had really the classic bump on its nose, and “Kritosaurus” has now become a poorly-known genus just like Hadrosaurus. To compensate, Gryposaurus (found in 1910 but ignored for decades) has taken the heritage of this “decayed gentleman” and has become the new “bulge-nosed hadrosaur”, along with other two new discovered hadrosaurs known only from their skull: the Native American-sounding Anasazisaurus and Naashoibitosaurus. Also note that some “Kritosaurus” remains have been described in South America, but they too are scant and almost certainly not from this genus. A valid South American hadrosaur (though just as scanty) is Secernosaurus.

USA and China make peace: Saurolophus, Prosaurolophus, and Brachylophosaurus

• In general, Late Cretaceous dinosaurs are very similar in Western North-America and Eastern Asia. This because these landmasses were uned at the time by a stripe of dryland where today is the Bering Strait. This means that dinosaurs at the time could wander from one continent to another. Nonetheless, Asian and North American dinosaurs are usually classified as distinct genera (see Tyrannosaurus rex and Tarbosaurus bataar for example). But there is also an exception: Saurolophus is perhaps the only dinosaur whose North American and Asian remains are always classified in the same genus, though to distinct species. First discovered in North America during the aforementioned “Canadian dino-rush”, Saurolophus has left few fossils in Alberta, but much more have been then discovered near China during the Russian dinosaur-hunt in Mongolia (at the time Mongolia was under URSS influence) which followed the first American one led by Andrews in the 1920s. Saurolophus still remains today the most abundant duckbill from Asia. However, its North American species has also been important initially. Think about Parasaurolophus: discovered soon after Saurolophus, its name just means “near Saurolophus”. Indeed, both dinosaurs were superficially similar, with a bony “horn” pointing backward from the rear-end of their skull. But that of Saurolophus was far shorter, more pointed, and made by solid bone, not hollow like that of “Para”. There is also a third similarly-named hadrosaur, Prosaurolophus, which means “before Saurolophus”. Still another is Brachylophosaurus, (“short crested lizard”). Indeed, “loph-” is a common particle among hadrosaurian names (and theropodian as well: think about “Dilophosaurus”…); this is indeed the Greek for crest. These two last examples are small, primitive North American hadrosaurs found some years after Saurolophus but with incospicuous crests similarly to Maiasaura. In spite of having left abundant remains, their modest appearance make them a rare sight in media. ^[1]. Talking about the more familiar Saurolophus and Parasaurolophus, the two “horned” duckbills tend often to be confused each other by non-specialists - and their similar names don’t exactly help to resolve the mixup, too. The main example is seen in the Land Before Time: Ducky, the hadrosaurian member of the Five-Man Band of dinosaurs, has a clearly Saurolophus-like crest, and yet has been labeled Parasaurolophus. Astonishingly Saurolophus (and Prosaurolophus and Brachylophosaurus as well) were closer to crestless hadrosaurs like Edmontosaurus than to Parasaurolophus! Just like Edmontosaurus, Saurolophus has often been depicted in paleo-art with a speculative, inflatable, frog-like air-sac on their snout, but this is not demostrated.

Frisbee players...: Hypacrosaurus and Olorotitan

• If you see a “frisbee”-crested hadrosaur in books or documentaries, be not sure it’s a Corythosaurus. The latter had indeed a twin called Hypacrosaurus, with a similar crest though fairly-smaller. Sadly, since some (possibly female) Corythosaurus also have a rather low crest, this doesn’t help us so much to separate the two; the most sure trait to to it is to watch the taller neural spines of Hypacrosaurus in a mount. Not surprisingly, Hypacrosaurus has been confused with Corythosaurus or even Lambeosaurus (see further) in the past, and to complicate matters, some juvenile remains from these three animals were even labeled as a genus on its own, "Procheneosaurus"! However, in the nineties, a nidification site in North America full of Hypacrosaurus nests and hatchlings has been discovered, analogue, to the classic Maiasaura; this find has made Hypacrosaurus a more well-known duckbill. Meanwhile, two brand new flat-crested hadrosaurs were found near the Amur which divides Russia from China: Amurosaurus and the spectacular hatchet-crested Olorotitan.

…and trumpet players: Charonosaurus

• On the other hand, 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. 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.

The biggest. Or maybe not: Lambeosaurus and Shantungosaurus

• Even though is often passed off, hadrosaurs were the biggest non-sauropodian dinosaurs. The most massive species were taller, longer and heavier than even the larger ceratopsians, stegosaurs, or ankylosaurs. And though not necessarily taller/longer, thanks to their massive bodies, they were heavier than giant theropods like Tyrannosaurus or even Spinosaurus itself! But which kind was the record-holder? Traditionally, two hadrosaurs have contended the record: North-American Lambeosaurus and Chinese Shantungosaurus. Lambeosaurus is probably the most striking-looking among North-American hadrosaurs, but is usually unseen in fiction unlike, to say, Parasaurolophus or Corythosaurus. And yet, it has one of the richest fossil record among all hadrosaurs (unlike the very rare Parasaurolophus), with two distinct species described plus a third putative one. Overall, Lambeosaurus was similar to Corythosaurus with a flat, vertical crest with the same hollow spaces. However, the most known species’s crest was taller, narrower, more rectangular, and with a secondary point raising backwards: a sort of “glove” with the “thumb” placed at 90° in respect to the main body (it is possible though, that only males did have that secondary point). The other confirmed species had a more rounded crest without the secondary point, but was spectacularly big and pointed slighty forwards. The third possible species, even though poorly-known, has the distinction to be the biggest North American hadrosaur known so far (15m/50ft of length), while the two confirmed species were “only” 10 m long, the same size of most hadrosaurs. Significantly, the normal-sized Lambeosauruses have classically been oversized in books, to match the biggest one. Lambeosaurus has also given its name to its own hadrosaurian subgroup, Lambeosaurines aka hollow-crested duckbills: Parasaurolophus and Corythosaurus are, thus, lambeosaurines. Discovered in the 1970s, Shantungosaurus was a crestless hadrosaur quite similar to Edmontosaurus, but with the same size of the controversial “giant Lambeosaurus (15 m/50 ft long). Unlike the latter, these gigantic remains are confirmed to pertain to the genus; and yet, Shantungosaurus has traditionally not received so much attention, even in books. Recently discovered incomplete Shantungosaurus remains seem to show an even larger animal (16 m), possibly the largest creature to have ever walked the Earth on two legs. This specimen was initially thought to be its own taxon, "Zhuchengosaurus".

All began with a duckbill 2: Mandschurosaurus, Tsintaosaurus, and Bactrosaurus

• 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. Nicknamed the “unicorn dinosaur” because of its high, pointed crest on its head, Tsintaosaurus was found in the 1940s and thus is one of the “classic” Chinese dinosaurs. It also has had one of the most tormented Science Marches On stories among all dinosaurs. Initially was described from fragmentary remains that seemed to show that horn-thing upon its head; then, scientists took it away in the 1990s, thinking it actually was a misplaced piece from the rest of its skull; but a recently discovered complete skull shows Tsintaosaurus really does deserves the “unicorn” title. Some other Asian hadrosaurs were much more generically-looking: for example, Bactrosaurus, one of the smallest hadrosaurs known – only 6 m long. Discovered in China and in Russia, Bactrosaurus is also one of the earliest hadrosaurs, without any crest on its head, and still rather Iguanodon-like in look – remember hadrosaurs are just very specialized iguanodontians phylogenetically speaking. The legacy with Iguanodon is confirmed by Probactrosaurus, an Early Cretaceous ornithopod which was still not a proper hadrosaur, but was going to become such. Also Asian, it was so similar-looking to Bactrosaurus to give a concrete clue about hadrosaurs’ ancestry (its name just means “before Bactrosaurus).

1. ↑ Even though Brachylophosaurus has recently given us some spectacular fossils which might make it more widely-known: among these, a true “mummy”, just like Edmontosaurus