Spec Dinosauria: Tyrannosauroidea

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(fig. 1) Nian, Smilotyrannus sinensis and Shantank,Ceronychoides gravis (Eastern Asia)
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The mere mention of “meat-eating dinosaur” conjures up mental images of the bloodthirsty tyrannosaurs, the most infamous of the large carnivorous dinosaurs to us puny humans. Mounted skeletons of the infamous Tyrannosaurus rex, the terror of the Late Cretaceous, are a guaranteed drawcard to any museum gallery. For the spexplorer, the prospect of seeing living, breathing tyrannosaurs is both a thrilling and fearful prospect. It is thus, difficult to decide whether to be relieved or disappointed upon discovering that most of Spec's tyrannosaurs are small, fluffy critters not much bigger than a large dog.
Tyrannosauroids are highly specialized basal coelurosaurs, easily recognized by their disproportionately large heads and tiny forelimbs. They have invested nearly all their firepower into their teeth and jaws, resulting in big, boxy skulls powered by massive musculature. Certain skull-bones have fused together, leading to a trade-off of facial flexibility in exchange for greater strength. The curved, serrated teeth are extremely broad when viewed in cross-section (as opposed to the flat blades most other predatory theropods). To support such a huge head, the neck is short and extremely well muscled. The arms are greatly reduced in size, having at most only two functional digits, while the hind limbs are large and powerful. All of Spec’s living tyrannosaurs belong to the family Errosauridae, which are notable for their furry adult-coats, fused metatarsals and rear-facing pubes.
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HISTORY
ERROSAURIDAE (extant Spec tyrannosaurs)
ERROSAURINAE (Striders, khinners, Oakelies, and bruisers)
Striders
The khinner
Courours
Oakelies
Bruisers
SMILOTYRANNINAE (Sabre-tyrants)
The imperial sabre-tyrant
The raalo
The thunderbird
The nian
NOTOTYRANNINAE (Cazadins)
Cazadins
The deseado dancer
The cazarrino
The dwarf cazadin
HISTORYEdit
Tyrannosauroids probably arose from small coelurosaurian ancestors towards the end of the Jurassic Period with the fragmentary Stokesosaurus being a possible early member of this clade. The earliest well-known primitive tyrannosauroid is the Early Cretaceous Eotyrannus from Britain, a sleek 5-meter predator with relatively long forelimbs. During the Late Cretaceous, the familiar short-armed giants of the family Tyrannosauridae were the dominant large carnivores throughout the Northern Hemisphere, producing such well-known forms as Tyrannosaurus and Tarbosaurus.
On Spec, the tyrannosaurids (including the genus Tyrannosaurus) continued to thrive up until 55 million years ago. From then onwards, the 14-metre long terrors become increasingly rare, replaced by smaller forms in the 3-9 meter range. The sudden rise of global temperatures at the start of Spec’s Cenozoic Era may have created several factors that brought about this shrinkage. The dense forests that blanketed much of the Eocene world may have restricted the movement of larger animals while the tyrannosaurs’ favored hadrosaur prey was beginning to experiment with smaller, fast-running forms.
By the Late Eocene, a few giant tyrannosaurids remained in North America, presumably sustained by the herds of colossal ceratopsids that roamed across that continent. Not surprisingly, when Brontoceratops and its kin vanished at the start of the Oligocene, so to did the old-style tyrannosaurids, but by then a wide range of smaller, more bizarre tyrannosauroids had evolved. Phobotyrannids were pug-snouted, robust creatures with huge teeth, their faces and bodies adorned with numerous spines and hornlets. At the opposite end of the spectrum were the graceful bactyrannids with their slender-builds and narrow skulls. Nestled in amongst this motley crew of killers were some small, fluffy cursorial predators, the first errosaurids.
True errosaurids were well established throughout the Northern Hemisphere by the end of the Oligocene. An earlier find from Europe strongly hints at the group's origins, among the many superb fossil finds of the mid-Eocene Messel Shales are three exquisitely preserved specimens of the little tyrannosaurid Saltotyrannus. At just over a meter in length, this creature resembled a hatchling Tyrannosaurus with long, slender legs and the fluffy chick-down that would normally be lost in adulthood. However, the level of bone-ossification proves these specimens to be adults, as if the eggs found in the body cavity of one specimen weren’t enough. It would seem that a freak, neotonous mutation had created a hatchling-like tyrannosaur that retained it’s small size and insulatory covering into maturity, producing a diminutive predator that was well suited to the dense tropical jungles of Eocene Europe. These small, fluffy killers almost certainly gave rise to the first errosaurids during the Oligocene.
ERROSAURIDAE (extant Spec tyrannosaurs)Edit
All living tyrannosauroids belong to a single, but very diverse lineage, the Errosauridae that contains over thirty living species. Immediately noticeable on any errosaurid are the furry protofeathers that cover almost the entire body. Beneath this fluffy-coat are a suite of adaptations that have allowed the errosaurs to become the most highly cursorial of all living theropods - these dinosaurs can not only move fast but can maintain pursuit over considerable distances.
The three metatarsal bones become fused, greatly strengthening the foot. The craniofacial air-sac system is very well developed, helping to keep the animal cool during lengthy physical exertions. The pelvic girdle is odd in that the pubis is bent slightly backwards, but does not lie against the ileum as in raptors and therizinosaurs. Such a configuration is superficially similar to the ancient Triassic dinosaur Herrerasaurus. A likely explanation for this feature is, once again, linked to the dinosaurs’ running abilities. In the conventional saurischian pelvis of earlier tyrannosaurs (where the pubis juts forwards), there was a potential mechanical problem where the leg came dangerously close to the pubis and the associated musculature, limiting the amount of room in which the limb may be safely swung forwards.
Hip bones
(fig. 2) Pelvis of the Cretaceous tyrannosaurid Tyrannosaurus (left) alongside that of the errosaurid Smilotyrannus (right).
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However, swinging the pubis all the way back to the ileum as in a deinonychosaur’s pelvis would have created another problem. Most predatory theropods rest in a horizontal pose with the body supported on the end of the forward-facing pubis. Deinonychosaurs, with their aft-directed pubes are required to sit in a more upright posture that, thanks to their lightweight skulls, is not a problem. A tyrannosaur’s massive skull on the other hand would impose a terrible burden on the spine if it sat in this position for a prolonged period. Perhaps the errosaurs’ slightly aft-facing pubis forms a compromise that increases stride-distance while allowing the animal to sit horizontally.
The errosaurids can be divided into three subfamilies: the small, generalized errosaurines, the ultragracile two-toed nototyrannines and the hulking, sabre-toothed smilotyrannines.
ERROSAURINAE (Striders, khinners, Oakelies, and bruisers)Edit
Errosaurus
Most of the Errosaurids' current diversity resides within Errosaurinae, a group of long-legged predators similar to the ancestral errosaurid. They are generally small animals, rarely over two meters long. However, their bone crushing bites more than makes up for their lack of size.
With only a few notable exceptions, the errosaurines are small cursorial predators. The North American strider is a perfect example of the group, being quite small and slight, with a coat of insulating plumage and atrophied arms. These little tyrannosaurs range across the northern prairies of North America, where they hunt singly for small game or occasionally gather together to hunt therizinosaurs.
StridersEdit
Striders have a distinctly heterodont dentition, with a series of conical front teeth for grasping prey followed by rows of backward-curved serrated teeth adapted for slicing flesh. One of these predators will catch small prey with its front teeth, getting a firm grip before throwing its head back and transferring the animal to its slicing rear teeth, which funnel food into the gullet.
STRIDER2
Taiga striders (Errosaurus arahorni) are ubiquitous on the steppes of northern Eurasia. Pursuit-predators of surpassing skill, these eight-meter-long errosaurs hunt the formosicorn herds, running a hapless yale to exhaustion before ripping the animal apart with powerful tyrannosaurian jaws. Ealines are the principal prey of the striders, leaving larger orths and catoblepids to pack-hunting draks and giant sabre-tyrants.
The khinnerEdit
Khinner The khinner is a small and swift errosaurid that lives in Mongolia and northeastern China. Preferring smaller prey than their cousins, the striders, khinners generallyStrider target mammals and birds as food, although they will often gather into packs and attack therizinosaurs during times of famine.
CouroursEdit
While courours are the dominant small-game predators on grasslands across North America, they are by no means the only carnivores in that habitat. The oakely, or American khinner, is the second-largest predator of the North American prairie, the cougar to the courour's coyote.
OakeliesEdit
Oakelies are solitary pursuit predators, running down game such as virosaurs and young hmungos and killing with a quick bite to the spine. Oakelies also may scavenge from buffalo-bill kills, though these relatively puny errosaurs are careful to keep well out of the way of the massive sabre-tyrants.
Oakely
Oakelies are roughly twice the size of their Mongolian cousins, and, as with many tyrannosaur species, females are larger than males, often reaching lengths of four meters. This size disparity reflects the oaklies' nesting behavior, with the female rearing and protecting her chicks without help from her mate.
BruisersEdit
Bruisers (Contusisaurus sp.) are the bull terriers of the errosaurs, powerful brutes that compress all the power and ferocity of their distant Cretaceous ancestors into frame only a few meters long. Having split off soon after the errosaurs evolved their downy coats, bruisers developed in the direction of scavengers. Like the hyenas of home-Earth, bruisers are squat, compact predators, with powerful jaws, bone-crushing teeth, and a keen sense of smell. Pliocene fossils indicate bruisers once lived as far South as India, but today they are restricted to the northern forests and taiga of Eurasia and North America.
BRUISER
A forest bruiser is a powerful, 1.8 meter-long hunter-scavenger that tracks prey and carrion through the dim recesses of Eurasia's northern forest, mostly by dint of its excellent senses of hearing and smell. Carrion, even in advanced decay, can be quickly dispatched with a bruiser's bone-crushing teeth, and live animals fare little better against these snapping jaws. Although not capable of fast sprints, bruisers are tenacious in their pursuit of prey, and may track a wounded animal for days.
Siberianbruiser
Larger than the forest bruiser, the Siberian bruiser is still smaller than most of the taiga's predators. This ferocious hunter-scavenger's small size, however (never longer than two meters) belies a formidable bellicosity.
Like all bruisers, the Siberian is heavily built and squat, with short legs and powerful head and neck muscles powering huge bone-crushing teeth. Siberians, more social than their forest-dwelling cousins, will gather into packs that track hunting striders. The more fleet-footed errosaurs having made their kill, the bruisers will rush in screeching, teeth gnashing, and drive their foes from their prey. The bruisers then settle down to apart the carcass, and jaws capable of exerting 3,000 pounds per square inch of force to bear on their dinner soon reduce a formosicorn skeleton to a bloody smear in the grass, leaving few scraps for smaller scavengers. When forced to actively hunt, bruisers are capable of cooperative behavior of surprising complexity, usually picking an old or sick member of a herd and bringing it down with bites to the feet.
SMILOTYRANNINAE (Sabre-tyrants)Edit
The sabre-tyrants of Spec are arguably the most famous of this world's fauna. With their elongated, canine-like teeth, these immense predators roam throughout North America and Eurasia, preying upon the largest herbivores. These teeth are a comparatively recent phenomenon and are a specialized adaptation used to bring down giant polar therizinosaurs. Not only do these aggressive herbivores possess wicked claws (making a stand-up fight against one a suicidal prospect), but their flesh is also covered in a dense layer of feathers and thick, fat-laden skin. A conventionally toothed tyrannosaur going in for the kill against one of these brutes would likely end up with a mouthful of fluff and lard plus one very ticked-off therizinosaur looking down at him.
The smilotyrannines thus abandoned the massive chomping techniques of their ancestors in exchange for a more refined and precise armor-piercing attack aimed at strategically disabling its prey rather than crunching it with one bite. The first maxillary teeth became greatly elongated and narrower, becoming graceful stabbing blades. A single bite would easily drive these sabres through a therizinosaur's hide, leaving deep wounds that would severely weaken the animal through shock and blood-loss. A sabre-tyrant attack thus involves one or two quick hit-and-run strikes followed by a more leisurely final deathblow once the prey has been sufficiently weakened.
Despite their impressive appearance, the elongated teeth are quite fragile and are frequently broken, but the tyrannosaurs have one huge advantage over their extinct HE(Home-Earth) mammalian counterparts - their sabres grow back. If a Home-Earth sabre-toothed cat broke its canines, it was a very sorry kitty indeed. However, the loss of a sabre for a smilotyrannine is of little consequence since its teeth are continually replaced throughout it's life and it can, if healthy, scrape out a living through scavenging or driving draks from their kills in the weeks needed for the new sabres to erupt and grow.
Clade Smilotyranninae reached its apex during the Pleistocene, producing such forms as Smilotyrannus horridus , a giant to rival even the famed Tyrannosaurus rex (although it has been suggested that these were simply giant morphs of living species). Now, the smilotyrannines occupy the top-predator niches across the northern reaches of both Eurasia and North America and are restricted to a single genus, Smilotyrannus
The imperial sabre-tyrantEdit
The vast, wind-swept plains of the Arctic Circle are home to only a few hardy creatures, but one of the few animals that manage to survive here is a true monster.
The imperial sabre-tyrant, at over ten meters in length, is the largest terrestrial carnivore on the planet, uncomfortably reminiscent of such lost giants as Tyrannosaurus and Giganotosaurus. Unlike its warm-weather predecessors, however, the imperial sabre-tyrant is a denizen of the deep Arctic. Living in this land of ice is a remnant of the last Ice Age, a massive predator of the only prey large enough to support it, the arctotitan.
Logotyrant
The sabre-tyrant is one of the few remaining examples of its kind, and has not changed appreciably since the Pleistocene. This massive predator is a runner, not as fast as its smaller cousins, the striders, but easily fast enough to pursue the lumbering arctotians. A sabre-tyrant relies both on strength and agility to combat these heavily armed therizinosaurs. Long legs sweep the body out of reach of the herbivore's manual talons, a thick neck pushes the blunt-snouted face toward the prey's unprotected flank, and teeth as long as a man's arm slice past the thick layers of feathers and blubber to the steaming muscle below.
Sabre-tyrants are masters of the bleed-to-death hunting strategy employed by their extinct cousins, the tyrannosaurids, as well as their closest RL counterparts, the saber-toothed cats. Their incredibly long fangs, coupled with the typical tyrannosaurian battery of D-cross-sectioned scooping teeth at the front, and slicing, steak-knife teeth toward the rear, create a flesh-cutting machine that can gouge huge chunks out of muscle, slice tough tendons apart, and rip a vertebral column to splinters. A sabre-tyrant will inflict the worst damage it can upon its victim, then dash back to safety and wait for the hapless creature to expire from blood loss before returning to feed.
Sabre-tyrants are not particularly social and, indeed, their ferocious territorial instincts keep them separated almost all year. The single exception to their normal aggressive behavior takes place during the spring mating season, when the males range about looking for prospective brides. Courting is brief and the suitor, in mortal dread of being devoured by his lady, departs as soon as possible. The female lays her clutch of 4-6 eggs soon after in a volcano-shaped mound and incubates them with fermenting vegetable matter. The tiny, helpless chicks hatch quickly, and the doting mother takes excellent care of her children. Sabre-tyrant mothers often carry their progeny around in their mouths, carefully spitting the chicks into some secluded pile of brush before going off to hunt. She will continue to care for the chicks all through their first winter, finally leaving them to fend for themselves as the Arctic's brief spring passes. They must then set off to establish their own territories, never to see their parent again.
Smilotyranbw
For all their prowess in the hunt, sabre-tyrants are a dying breed. They are almost completely specialized upon the arctotians for their food, and the end of the Ice Age has seen a drastic reduction of the giant herbivores' tundra habitat. The imperial sabre-tyrant can now only be found on the icy plains around the Arctic Circle, in both Siberia and northern Canada (although fossils indicate they once ranged as far south as France). Without doubt, it is the lack of human intervention that has saved these magnificent predators from the fate of the sabertoothed cats of our own timeline.
URAALO
The raaloEdit
The raalo is a medium-sized saber tyrant that lives in the northern Fennoscandia and westernmost parts of Russia. During the summer, raalos live alone or in pairs, but during the winter they gather together into small packs. Though raalos are only 6-7 meters (the female is always larger) long, they can bring down full-grown mooras and dorsas . During the summer, the raalo gathers fat to the base of its tail.
Thunderbird
The thunderbirdEdit
The thunderbird (Smilotyrannus brontus) is the largest carnivore of the forests of the Pacific Northwest. A somewhat primitive smilotyrannine, the thunderbird is considered by most to be a late-surviving member of a larger group of Ice Age predators. Camouflaged plumage, large maw and short legs aid the thunderbird in running quickly through forests.
Smiloprof
Smilotyranchase
The nianEdit
Smilotyrannus sinensis, the nian, is a smaller but relatively more robust than the imperial sabre tyrant. Like its larger cousin, the nian is a solitary hunter. While nians usually live close to the polar circle, sometimes they may wander off far enough south to prey on shambla young.
NOTOTYRANNINAE (Cazadins)Edit
Soon after the first errosaurids migrated to South America, a new group emerged on the continent. Fuzzy, diminutive errosaurids migrated into South America only about five million years ago, during the Pliocene, and at the present time, this group dominates the small predator guild of the neotropics.
Ironically, these predators did not grow to become the Tyrannosaurus-like monsters as did the smilotyrannines of Asia and North America. Rather, the Neotropical errosaurids competed for the niche and eventually lost to another group of near arctic predators, the boreonychids. Thus, these deinonychosaurs occupy the all of the large predator niches in South America, while the tyrannosaurs are relegated to the small, running-predator niches that are have traditionally belonged to the deionychosaurs.
As a rule, nototyrannines posses less plumage than their northern cousins (indeed, some are almost bald), and most are extremely gracile, with very long legs and a stiffened tail. However, the most obvious distinguishing feature between the two groups is the nototyrannines' toes (or lack thereof). All members of the clade Notovenatorinae posses only the two outer toes of the foot, the inner toe and the hallux being atrophied to mere slivers of bone, invisible beneath layers of skin and muscle. These creatures also tend to run on the very tips of their toes, giving them a distinctive, ostrich-like gait.
South America is a continent of strange wonders, with giant armored turtles, lanky pachas, and tiny, fleet-footed tyrannosaurs. Of these last, the meter-long white cazadin is the most common, a ubiquitous small predator of the pampas.
CazadinsEdit
Cazadins range from just south of the Amazon to Patagonia, and eat a variety of small dinosaurs, mammals, reptiles, and invertebrates. These solitary predators have even been observed to eat poisonous snakes, strangling the reptiles with their powerful feet before biting off the head. During the mating season, male cazadins develop a yellow tinge to their head and neck feathers, while their brow ridges turn blue and their tiny, atrophied arms flush red. This trait has earned the South American tyrannosaurs their generic name.
Tyrann
The deseado dancer
The deseado dancer is medium sized cazadin and rather large by South American standards. These agile dinosaurs live in small pockets across southern South America. Solitary cazadins hunt a wide variety of prey, from mammals to viriosaurs to young dinoceratopsians.
Ddancer
The cazarrino
At 50kg, the cazarrino (Notovenator pictus) is a typical South American cazadin. The behavior of the cazarinnos is no so typical, however, as these little hunters travel in packs of up to ten indivduals. Cazarrino packs hunt the fleet-footed viriosaurs of the pampas, running old or sick herdmembers to exhaustion before dispatching their prey with a powerful bite to neck.
Tyran
The dwarf cazadin
A close relative of the cazarrino, (‘’Notovenator agressimus’’), the dwarf cazadin lives along the montane streams of the southern Andes. Dwarf cazadins have a pronounced taste for fish, and are most often seen hunting along fast-moving rivers, although the little tyrannosaurs will readily pursue birds or mammals.
Errosaurusagressimus