Dinosauria

Myriad differences exist between the respective biotas of Spec and Home-Earth, but the first glaring distinction to impress itself upon a visitor would be the dinosaurs. Spec's dinosaurs are wildly diverse, with species ranging from tiny hummingbirds to massive gihugrongos and rapacious sabre-tyrants. Descriptions of the dinosaurs of Spec takes up the bulk of this book.
Dinosaurs evolved during the middle or early Triassic, between 230 and 250 million years ago, as part of a larger radiation of archosaurs. These "ruling reptiles" that are today represented by dinosaurs and crocodilians, both born almost directly after the Permian extinction had wiped out virtually all life on Earth. There were a few million years of confusion, but by the end of the Triassic, dinosaurs had emerged over the reptiles, mammals, and other archosaurs as the dominant terrestrial vertebrates. Dinosaurs quickly diversified and today, they occupy a wide range of forms – a much wider range than the mammals of our home timeline enjoy.
Dinosaurs are split into two principal groupings, the Saurischia (including among others sauropods and theropods, which in turn include birds) and the somewhat less diverse Ornithischia (including ceratopsians, ornithopods, and ankylosaurs). Saurischians are the more plesiomorphic of these two groups (most similar to the common dinosaur ancestor), and usually retain superficially lizard-like hips, with the pubis (one of the three bones in the hips) pointing down or slightly forward, although many saurischians (including most maniraptors, such as birds) have hips that are swept back. The ornthischians also evolved swept-back hips, probably as an adaptation to accommodate larger, plant-digesting guts. Over the eons, both groups have experimented with carnivory, omnivory, and herbivory, but it is still safe to say that many saurischians are predators while many ornithischians eat plants.
Today, saurischians are the more widespread and diverse of the two branches of Dinosauria. The sauropods, an ancient group of huge, long-necked saurischian plant-eaters, are still present in the warm parts of the Old World, although they are much reduced, and the abelisauroid predators roam the same areas in pretty high diversity. For the most part, however, modern saurischians are coelurosaurs, two-legged and feathered. Apart from a few basal representatives like the Australian cedunasaurs, the tyrannosaurs, and the manticorant, most modern coelurosaurs are birdlike maniraptors. Maniraptors have proved wildly successful in the world of Spec, running the gamut from lumbering therizinosaur over fearsome drak to soaring bird.
The most successful maniraptoran clade, the birds (Aves), has strayed so far from its ancestors that Linnaean taxonomy has taken it out of Dinosauria and given it a class of its own, on par with mammals, "reptiles", and amphibians. However, now that Linnaean taxonomy has largely been abandoned, birds' obvious descent from dinosaurs clearly places them within the dinosaurian group Maniraptora. On the Specworld, this relationship is easier to see than in our home timeline, with many of the intermediate forms surviving to the present day (see the Maniraptora introduction). Aves is far more diverse in Spec than in our home timeline, including many taxa found only on Spec. A number of ancient bird lineages, such as the enantiornithians and the toothed ichthyornithids survive to the present day, and are joined by many familiar avian groups (ducks, penguins, and others), as well as number of odd groups like the bunglebirds and carpos.
The other dinosaurian group, Ornithischia, is not as widespread as Saurischia, but still quite successful. Most basal ornithischians have gone extinct, and though a few ankylosaur lineages still survive in and around Australia, all of the remainder are either ceratopsians such as †Triceratops or ornithopods such as †Iguanodon. Ceratopsia suffered heavy losses in the early Tertiary and is today represented only by the caenoceratopians, a group which ranges in size from one pig to two elephants, and in geography from Africa to South America. Far more common than the caenoceratopians, however, are the ornithopods, which live on every continent but Antarctica.
Ornithopods are split into two great taxa, the iguanodontians and the antarctornithopods. The divergence between these two occurred far back in the Mesozoic, with both groups evolving from small, bipedal herbivores. Iguanodontians quickly spread across the world and evolved into a wide range of forms, both small (†Dryosaurus, †Gasparinisaura) and huge (†Edmontosaurus, †Muttaburrasaurus). These creatures continue to thrive to the present day, as, among others, hmungos thundering across North America, saurolopes sweeping through the plains of Africa, and dendrosaurs swinging about the trees of Australia. Somewhat less successful, but still widespread and diverse, are the antarctornithopods. These creatures evolved from generalized basal ornithopods like †Leaellynasaura of the Early Cretaceous of Australia, and today they are still mostly restricted to the southern hemisphere. In Australia, especially, antarctornithopods are dominant, both in the herbivore niches (Euclasauria) and the predator guilds (Rhynchoraptoria). The generalized viriosaurs of the Americas are also antarctornithopods, splitting from their Australian cousins some time in the very early Cenozoic, walking to South America from Australia via Antarctica. Together, the two ornithopod groups occupy most of the herbivore niches of Spec.

In the 230+ million years of their evolution, dinosaurs have conquered the land, the air, and the sea. They live on every continent as well on nearly every island of any size (as birds). In their species-count, in their diversity of form, and in their sheer biomass, the dinosaurs of Spec are the unquestioned rulers of the earth.

SAURISCHIA

TITANOSAURIA (Grassbags, mokeles, and gihugrongos) The big, the superhuge, and the gihugrongous!

ABELISAUROIDEA (Moloks, kagrus, and the cain) Fearsome predators with scaly hides

NOASAURIDAE (Cains and kagrus)

CEDUNASAURIA (Cedunasaurs, chimerasaurs, and warriguls) Australian critters ranging from predators to high-browsing herbivores

TYRANNOSAUROIDEA (Sabre-tyrants, bruisers, and cazadins) Small to huge feathery predators

ARCHAEOPLUMIA (Manticorants and archaeplumes) Small, rare African and Indian predators

MANIRAPTORA (Draks, ducks, etc.) Birds and near-birds

THERIZINOSAURIA (Yandos, lammoxes, arctotitans, and hornclaws) Bipedal, heavily plumaged herbivores
OVIRAPTOROSAURIA (Vulgures, gollums, hogbirds, nostriches, and seedcrackers) A few relics of a strange clade
TROODONTIDAE (Nandrakes) The pathetic remnants of a once worldwide group
DEINONYCHOSAURIA (Mattiraptors, hesperonychids, draks, ninjas, and arbros) Bipedal predators with hyperextendable inner toes

RAHONAVIDAE (Bureaucratbirds and stefs) Madagascar's not-quite-deinonychosaurs

ALVAREZSAURIDAE (Alvies) Just as weird now as they were then

XENORNITHES (Bunglebirds and carpos) Good climbers and strange fliers

ENANTIORNITHES (Avisaurs, tweeties, etc.) 'Opposite birds'

HESPERORNITHES (Sea parrots, seaguins, and archers) Toothed, mostly flightless seabirds

ICHTHYORNITHIDAE (Baygulls, toothauks, surfbirds, and harpies) Toothed birds of air and sea

NEORNITHES (Ducks, penguins, gobblers, etc.) Mostly familiar birds

ORNITHISCHIA
CAENOCERATOPIA (Sunhorns, undaurs, etc.) Quadrupedal browsers

VIRIOSAURIA (Viris, kranili, and levipodes) A diverse group of basal ornithopods
EUCLASAURIA (Brush-runners, chlorosaurs, euclasaurs, and tanamisaurs) Australia's dominant herbivores

RHYNCHORAPTORIA (Anklebiters and rhynchoraptors) An endemic Australian lineage of omnivorous and carnivorous ornithopods

VANGUARDIDAE (Vanguards) Armoured herbivores of America
LATICANATIDAE (Duckgongs) Aquatic and semi-aquatic herbivores
PSEUDOSAUROPODA (False-sauropods) Huge, long-necked ornithopods convergently similar to sauropods

NEODRYOSAURIA (Hypsies, Malagasy hypsies, honkers, dendrosaurs, and piggy-beaks) A mixed collection of small herbivorous species from Australia and Madagascar

HADROSAURIA (Hmungos, kirin, etc.) Extremely diverse group of mid-sized to elephantine quadrupedal herbivores

NEOHADROSAURIA (Hmungos, singers, etc.) The North American hadrosaurs

UNGULAPEDIA (Saurolopes, hornmeisters, etc.) The hooved hadrosaurs of the Old World

FORMOSICORNIDAE (Orths, kirin, etc.) European grazers and browsers

ANKYLOSAURIA (Dreadnaughts and pyoros) Armoured herbivores of Australasia

Daniel Bensen and David Marjanović

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