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Spec Dinosauria: Hadrosauria

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Dhadrhead

INTRODUCTION

Among the plant-eating dinosaurs, the hadrosauroids or "duckbills" must rank as one of the all-time great success stories. Appearing no later than the Aptian, they rapidly diversified and spread across the globe. Spared from annihilation at the close of the Mesozoic, they continued to spread and diversify past what would have been the K/Pg boundary, producing a host of weird forms during the Paleogene.

Despite suffering a number of setbacks as the Cenozoic progressed, they remain today as the preeminent terrestrial mega herbivores on Spec and are found across the hotter zones of all landmasses except Australasia and Madagascar.

BIOLOGY & FEATURES

Hadrosauroids are highly derived ornithopods notable for their expanded beak (giving the characteristic "duckbilled" appearance). They are renown for their intensive dental batteries with up to 1,600 teeth in densely packed rows. These teeth are being continually replenished, giving the hadrosaur an effective grinding surface throughout its life. This makes the duckbills' tooth batteries supremely efficient processors of plant matter.

They also have a reduction in the number of wrist bones and have lost digit I. Ossified neural tendons along their spines often attain a degree and complexity unknown in an other tetrapods. Their crania are intensively pnuematicised, giving them a great degree of respiratory moisture savings and also wonderful vocal calls. Hadrosauroids are also among the most powerful animals for their size of either timeline. Pound for pound, their skeletons, tendons and muscles can generate enormous forces.

HISTORY

The most fascinating thing about these characteristics is that they may have been independently arrived at by the two major hadrosauroid clades. The two surviving clades are quite distinct, possibly separated by as much as 120 million years. That such a high degree of similarity occurred indicates similar pressures from different lineages to convergent but not necessarily the same ends.

The fortunes of Hadrosauroids seemed to have waned somewhat during the Maastrichian and Paleocene. However, the latter Paleogene and much of the Neogene saw them take a good portion of the world by storm. Many archaic Hadrosauroid lines either arose or whittled away; to be replaced with essentially modern forms. The vast majority of the Ceratopsids and Ankylosaurids along with many other strange lines such as most of the Eurolophia also retreated to extinction. Though it should be noted that some relics of the previously mentioned groups still thirve to this very day. However, they are shadows of their former glory when compared to the vast majority of hadrosaurs that are present in the world of Spec.

The late Pliocene and Pleistocene Ice Ages have been detrimental for the hadrosauroids. Wonderful, ever replacing grinding teeth and complex gastrointestinal systems virtually unparalleled by critters of either time-line do not make up for a complete lack of insulatory integument. Today hadrosauroids are mostly limited to hot tropics, though some species can be found in in cooler subtropics or even make migrations up high altitudes during the summer seasons.

ALLOHADRIDAE

This is a recently discovered group of hadrosaurs found only in Asia, which retain some characteristics to their saurolophine ancestors. As of now, only one species is known from the group, that being the Chuanlong.

Chuanlong (Allohadros magnificus)

ALLOHADROS-0

Chuanlong, Allohadros magnificus (Eastern Asia)

Also known as the enigmatic chuanlong, the chuanlong (Allohadros magnificus) is a recently-discovered herbivore that lives deep within the forests of eastern Asia. Known only from a single skin and observations gleaned from a Specbiologist from a boat on the Yangzi.

The chuanlong was at first assumed to be a formosicorn ungulapede, but examination of the head (unfortunately, the nature of the tell-tale hooves were not recorded) leads one to believe that this dinosaur belong to the more basal hadrosauroid clan. In fact, the chuanlong bears a striking resemblance to the shamblas and hmungos of Eurasia and North America.

Perhaps this cryptic herbivore is the descendant of the Miocene migration that brought the shambla to the Old World. If so, the chuanlong is descended from a hitherto unknown branch of the hadrosauroid tree, for it exhibits a number of unique features, such as an inflatable nasal pouch and a series of bony scutes along its back.

Without better specimens, it is impossible to know whether the chuanlong is an aberrant neohadrosaur, an aberrant ungulaped, or something else altogether.
Chuanlong forest

A chuanlong in the forests of China

NEOHADROSAURIA

Neohadrosauria (Hmungos, galumphs, torgs, snufflelumps, singers and grasbucks)

Hadrosauridae consisted of two major groups, the flat-headed Saurolophinae and the hollow-crested Lambeosaurinae. The latter died out sometime near the end of the Eocene, except in Asia where the handful of species, the famous being the massive Sauropodimimus giganticus, hung on through the Oligocene, however, a small species of lambeosaurine from Japan managed to thrive in isolation to this very day. With the possible exception of a few undescribed species of lambeosaurinae. The saurolophines survived, however, and as the global forest fragmented, these dinosaurs radiated and spread onto the grasslands and became grazers. The first of these animals had evolved in the forests as small creatures superficially similar to today's singers, but when the forests began to recede, some left their traditional modes of life. When the Miocene arrived and grasses spread across the continents of Earth, these grazing hadrosaurids began their golden age. The large grazing neohadrosaurs have changed little since this time, and are still the largest herbivores in the Americas, while the North American neohadrosarus are the undisputed kings in North America, their South American kin, though still large, are overshadowed in size by the massive pseudosauropods. (although in Eurasia they have been largely replaced by ungulapedes).

UNGULAPEDIA

Ungulapedia (Palaeungulapedes, saurolopes, cirafs, hornmeisters, and formosicorns)

With about 150 species worldwide, the ungulaped hadrosaurs are a major herbivore clade of the Old World. Ungulapeds are found throughout Africa and the warmer parts of Asia. Their origins are unclear, but some evidence ties them to Tethyshadros insularis and Telmatosaurus transsylvanicus from the end-Cretaceous of Europe, one of the minor groups of Hadrosauridae.

Brian Choo, Daniel Bensen and David Marjanovic


                                              ,=NEOHADROSAURIA
                              ,=Hadrosaurinae=|
              ,=Euhadrosauria=|               `?~Allohadros magnificus (Chuanlong)
              |               |
              |               `=†Lambeosaurinae=†Sauropodimimus

=Hadrosauridae=|

              |
              | ,=†Telmatosaurus
              `=|
                `=UNGULAPEDIA

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