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Spec Dinosauria: Tyrannosauroidea

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Dtyrahead


Chase

(fig. 1) Nian, Smilotyrannus sinensis and Shantak,Ceronychoides gravis (Eastern Asia)

INTRODUCTION

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 wolf; a relief to those expecting the worst, but a disappointment for those who have fond memories of watching Jurassic Park in their youth. However, the some species of tyrannosaur still retain the great size of their giant ancestors.

Tyrannosauroids are highly specialized 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.

HISTORY

Tyrannosauroids arose from small basal coelurosaurian ancestors in the Middle Jurassic period with the fragmentary Proceratosaurus of the Middle Jurassic being the very earliest known member of this family. It too was swiftly joined by other tyrannosauroids, such as its close relations Guanlong of China and Kileskus of Siberia. These early forms also were the first tyrannosauroids to experiment with head ornamentation; thin, singular crests running the length of the skull akin to those of the unrelated Monolophosaurus. Stokesosaurus of the Late Jurassic was another early member of this superfamily, as was the tiny Aviatyrannis of Portugal. A later well-known primitive tyrannosauroid is the Early Cretaceous Eotyrannus from Britain, a sleek 5-meter predator with relatively long forelimbs. For most of their evolution, this was the norm for tyrannosaurs, and such forms as the gigantic nine-to-ten-meter Yutyrannus and Sinotyrannus were perfect examples of this. During the Late Cretaceous, some 80 million years ago, the familiar short-armed giants of the family Tyrannosauridae would become the dominant large carnivores throughout the Northern Hemisphere when their carnosaurian rivals died out, producing such well-known forms as Tyrannosaurus and Tarbosaurus as well as strange forms such as the pursuit predators like Alioramus and Qianzhousaurus.

In Spec, the large 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, however, there were exceptions to the rule. 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.

At this very time, India made its first land contact with Asia and debarked its freight of endemic Gondwanan animals. Some seem not to have survived the competition with the northern fauna; for example, abelisaurs have so far not been found in sediments between 55 and 25 million years in age in India or elsewhere in the Northern continents. Others however, had no competition. They immediately spread to Asia, North America, and then Europe. Among those are the Ranidae (the "real true frogs") and the extinct Carcharodontosauridae.

These on average, humungous predators possessed fearsome thumb claws and long snouts lined with with narrow, triangular, finely serrated teeth- ideal equipment for dispatching the extra-huge titanosaurs and ceratopsians of the time. Perhaps more importantly, they were adapted to ambushing, much like the smaller deinonychosaurs. This hunting method worked very well in the dense rainforests that blankets much of the Eocene world; tyrannosaurs on the other hand, were and are specialists for long-distance pursuit.

By the Late Eocene, a few giant tyrannosaurids remained in North America, presumably sustained by the herds of colossal ceratopsids, most notably the massive chasmosaurines, that roamed across that continent. Not surprisingly, when Brontoceratops and its kin, this applies to only the chasmosaurs in North America that went extinct, but their centrosaur cousins managed to fare better despite suffering heavy losses during that time period, though they too eventually suffered the same fate of their chasmosaurinae relatives, vanished at the start of the Oligocene, so to did the old-style tyrannosaurids, with the last known genus dying out about 30 million years ago. Their Eurasian relatives seemed to hold on out for a while longer than the tyrannosaurs native to North America, sustaining themselves on the ceratopsians and gigantic lambeosaurs that roamed Eurasia from the Cretaceous to the Oligocene epoch. However, a recent in depth analysis revealed that the Eurasian tyrannosaurs, most were more specialized in hunting the massive lambeosaurs in the area, most notably Sauropodimimus. When the giant lambeosaurs and most of the ceratopsidae had vanished at the end of the Oligocene, the larger tyrannosaurs in the area suffered the same fate as their North American relatives.

However, during the Eocene and Oligocene epochs, a wide range of smaller, more bizarre tyrannosauroids had evolved. Such examples included the massive Ceratotyrannids with their robust skulls decorated with hornlets, the most famous example being Lainosaurus benseni. Phobotyrannids were pug-snouted, robust creatures with huge teeth, their faces and bodies adorned with numerous spines and hornlets. Bactyrannids, which were on the opposite ends of the spectrum, were graceful predators with their slender-builds and narrow skulls. Nestled in amongst this motley crew of killers were some small, fluffy cursorial predators; the first errosaurids. Errosaurus borealis is one such example. These evolved around the time when the massive chasmosaurs went extinct and when hadrosaurs were starting to evolve in to smaller and more agile forms like Procurvihadrus specensis. While the ceratotyrannts and phobotyrannts eventually became extinct during the Miocene epoch, the bactyrannids managed to hold out until the end of the Pliocene epoch with the last of their members, most notably Probactyrannus gracilis, finally succumbing to the effects of climate change. Around of the same time when the Pleistocene epoch had begun.
Protoerrosaurus borealis

Errosaurus borealis, an extinct member of the Errosauridae dating back to the Oligocene Epoch.

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 nanus and the small Errosaurus borealis from Oligocene epoch deposits in western Canada. At just over a meter in length, Saltotyrannus nanus 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 (though the mutation theory is now debatable since the discovery of the primitive Chinese tyrannosauroid Yutyrannus). Whatever the case, these small, fluffy killers almost certainly gave rise to the first errosaurids during the Oligocene.

ERROSAURIDAE (extant Spec tyrannosaurs)

All living tyrannosauroids belong to a single, but very diverse lineage, the Errosauridae that contains over thirty living species in Spec. 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 illium 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).

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 notovenatorines and the hulking, sabre-toothed smilotyrannines.

ERROSAURINAE (Striders, Khinners and Oakelies)

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 bite 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.  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.

North American Strider (Errosaurus errornis)

Errosaurus
With only a few notable exceptions, the most if not all members errosaurines are small cursorial predators. The North American strider (Errosaurus errornis) 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 to the forests of Appalachia, where they hunt singly for small game or occasionally gather together to hunt therizinosaurs. Measuring up to five feet long (1.7 meters), they are of average size for a strider. Though it should be noted that these
Strider
Striders of all species 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.

Taiga Strider (Errosaurus arahorni)

STRIDER2

The largest of the striders, taiga striders (Errosaurus arahorni) are ubiquitous on the steppes of northern Eurasia. Pursuit-predators of surpassing skill, these six-meter-long giants even hunt the formosicorn herds of therizinosaurs, running a hapless yale or panha to exhaustion before ripping the animal apart with powerful tyrannosaurian jaws. Ealines and smaller therzinosaurs are the principal prey of the striders, leaving larger orths, catoblepids, dorsas, mooras and arctotitans to pack-hunting draks and giant sabre-tyrants.

King Strider (Errosaurus rex)

The second largest species of the genus, Errosaurus, and named after the most famous species of dinosaur, Tyrannosaurus rex, the King Strider can be found roaming areas of Western North America and even as far north of Canada. Ironically in the same locations that the iconic Tyrannosaurus rex was unearthed in as well. Solitary creatures by nature, these small but vicious creatures are known for being extremely territorial, even driving the larger species of draks away, but the large sabre-tyrants away. Another reason why this species is named after Tyrannosaurus rex is their bone crushing bite. While most species of the Errosaurinae family have a bone crushing bite, the King Strider is one of the few species that has perfected the art of bone crushing bite. Even giving the likes of the bruisers are run for their money. And just like the ancient iconic beast, females are larger and more agressive than the males.

Elessar's Strider (Errosaurus elessari)

The third largest of the Errosaurus genus, just behind the Tagia Strider and the King Stider, the Elessar's Strider is only one of two member of the Errosaurus sp. which can be found roaming Eurasia, also one of the top predators but not the largest in the area. They aren't found anywhere in Asia at all, you are more likely to find one in Eurasia. Growing up to lengths of up to nine feet long, it specializes in smaller animals and birds in the area, if they prefer to hunt solitary while it should be noted that these are pack animals by nature, some species will lead solitary lives. The Elessar's strider is named after the character of Aragon from the Lord of the Rings by J.R.R. Tolkein and they live up to their reputation with their behavior and appearance. Tall and covered in patches of gray and white feathers, these small but fearless carnivores will often work together in packs to bring down larger prey, the various species of ungulipede and therizinosaur which are common through out Europe.

Sonoran Strider (Errosaurus saguarorex)

The biggest killer of the North American deserts is the noble Sonoran Strider. Moving gracefully between cacti and scrub, it preys upon anything that cannot run away fast enough. Small draks and rubybacks are taken, as are the mammals which are run down or dug  out of their nests. Nevertheless, the hardy strider will not disdain unmice if the opportunity presents itself.

Ripper (Errosaurus eviscerator)

Also known known as the Scandinavian Strider, this species of strider is the only one of its kind that thrives exclusively in Europe, where as other members of its kind are known to occur throughout Eurasia. The ripper can be seen stalking herds of Cuinocco, usually as multiple members will wait to pick off a young, old or sick individual. Healthy members of the herd pose too much of a challenge for them.

Yarper (Errosaurus latransoides)

The second species of errosaur which can be found in the Flame Forest is the Yarper. A 1.5 m long errosaur weighing 8 kgs. Hunting in a speckled dun and red ochre coat, it preys on the abundant dogbunnies and other smaller creatures in the Flame Forest. However, roughly 75 percent of this strider's diet is dogbunnies. If the option of live prey is unavailable, the creature will resort to scavenging of larger carcasses. 

Rama-akilla (Errobestia lupines)

The pack hunters of Nepal region, the Rama-akilla (Errobestia lupinus), are new found species of coyote-sized errosaur, the only one in the region, which are coyote-sized and merciless at attacking and killing the local herbivores in packs. They are tender parents, and intensely social, only killing when necessary, and avoiding humans at the slightest provocation. These are the only species of strider in Southeastern Asia, and these small creatures fulfill the rule of the pantherbulls, which surprisngly are abesnt from the region most likely due to competition from other smaller pack hunting carnivores like the draks. 

Wendigo (Paraerrosaurs marjanovici)

One of two species of strider which can be found in the flame forest is smaller and more heavy than the yarper.  While the Yarper goes after the dog bunnies in the area, the Wendigo goes after prey like juvenile draks, bruisers and birds. In a series of events that mirror the relationships between the two species of rhynchoraptor from Australia, jagdpanther and strumtiger to be more specific, the Wendigo and Yarper seem to have a deep rooted hatred for the species and will go to violent lengths to remove each other from the environment. Despite this deep-rooted hatred for the two species, observations have shown that they will occasionally work together to bring down larger prey, most notably the larger therizinosaurs in the area and the migratory ungulipedes, the very few native to North America, that will pass through the area during their migration.

Khinner (Errosauroides mongoliensis)

Khinner
The khinner (Errosauroides mongoliensis) is a small and swift errosaurid, growing up to lengths of 10 feet long, that lives in Mongolia and northeastern China. Preferring smaller prey than their cousins, the striders, khinners generally target mammals and birds as food, although they will often gather into packs and attack therizinosaurs during times of famine. They appear to be more agile than their relatives, the Oakeley.

Queen Khinner (Errosauroides regina)

Also known as the American Khinner, this agile, but medium sized errosaur grows up to lengths of about 15 feet long, a little bit larger than its Asian relative, and it is the top predator in Southern North America. Since this is a recently discovered predator, not much of its behavior is known at the moment. However, one of the most recognizable traits about its that it specializes in hunting the singers in the area; more particularly the Valley Singer, Starry Singer and the Painted Singer. Its only major compeition in that area are draks, striders and another species of tyrannosaurs which can be seen native in the area.

Courour (Errosauroides canadiensis

With only a few notable exceptions such as the Volleur, which is still undergoing observations, most errosaurids are small, cursorial predators. The courour (Errosauroides canadiensis) is a perfect example of these smaller predators, being of lesser size (around 2.5 meters) and with a relatively slight built, and like all errosaurids, adorned 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, (possibly ceratopsians, but this issue is still under debate) and singers. This niche also brings them into occasional competition with the smaller North American Strider, which hunts much of the same prey. Analogous to the Home-Earth coyote as the North American Strider is to a Home-Earth fox, the Courour is as much as scavenger as it is a predator, and having a wider range of prey to choose from than the North American Strider, is better able to expand its resource base when food is scarce.

Oakeley (Errosauroides anniae)

Oakely
While courours are the dominant small-game predators on grasslands across North America, they are by no means the only carnivore 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.  

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.

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 4 meters.  This size disparity reflects the oaklies' nesting behavior, with the female rearing and protecting her chicks without help from her mate.

Buluc Chabtan (Chabtanotyrannus horendus

The enigmatic mystery of the Central American Tyrannosaur has been solved! Growing up to 15 feet long and standing as tall as man, the Buluc Chabtan is the only known species of tyrannosaur that inhabits the Central American rainforests. With a lithe, agile body and long slender legs, it uses them to chase down prey, most notably the viriosaurs. As of now, the only compeition it faces is from the larger dromaeosaurs native to this region and to South America.

CONTUSISAURINAE (Bruisers)

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 several 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.

Forest Bruiser (Contusisaurus belligerans)

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.
Grendel (Contusisaurus belligerans grendeli)

Being a subspecies of the forest bruiser native to Britain, Reports of Grendels reached spexplorers early on, and were certainly greatly exaggerated. The Grendels of Spec are bruisers, powerful tyrannosaurs that most often scavenge. However, Grendels are more predatory than their continental relatives, and more aquatic. The plumage is black and iridescent green, and the tiny, sunken red arms give the misleading impression of having been ripped out of their sockets. Females are dramatically larger than males. Growing up to 3 meters in length (a giant by bruiser standards), a solitary Grendel is more than a match for pretty much anything it encounters. Amphibious tendencies mean that these tyrannosaurs do not disdain water, and regularly stride out into the surf to hunt ammonites, which are crushed with massively powerful jaws. Fish and seabirds are also taken, and a jarrk rookery is heaven on earth for a Grendel. However, the dinosaurs remain relatively poor swimmers, and they will often give up after their prey slides into the sea. It will even prey on the ungulipedes that inhabit the island, most notably the Cuinocco and the Dwarf Orth.

Nevertheless, Grendels are not restricted to the coast. They regularly migrate away into Britain's dark oak forests, shrouded in mist and cloaked in gloom. There, where the trees are pillars and the branches a green ceiling, can be found the legendary "Hall of Heorot" of Spec, where creatures of the shade make a living, far removed from their sun-loving relatives of the Golden Afternoon.

Siberian Bruiser (Contusisaurus ferox)

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 rip 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.

Oni (Contusisaurus ferox japonicus)

Also known as Japanese Bruisers, these subspecies of Bruisers can be found in the Islands of Japan when it became seperated from the rest of Asia. Half the size of their mainland relatives due to the demands of island living, these species of Bruisers specialize in hunting the island hadrosaurs in the area.

SMILOTYRANNINAE (Smilotyrannus sp.)

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. Sabre-tyrants communicate with low near-infra-sound growling, something you're as likely to feel as hear,

Their origin is, again, thought to be connected to the carcharodontosaurs. While those hulks were superbly adapted to sawing chunks of meat out of a large body, they were unable to process bones. Tyrannosaurs, on the other hand, mean business when they bite. Coprolites of †Tyrannosaurus already contain fragmented bones, and †Triceratops skeletons have been found with scratches that indicate a †Tyrannosaurus made sure it had scraped all meat off the bones. This efficient prey processing allowed fairly large tyrannosaurs that specialized towards scavenging to coexist with the mighty carcharodontosaurs. Indeed, such tyrannosaurs, the Smilotyrannidae, evolved soon after the carcharodontosaurs had taken over the northern hemisphere; late Eocene strata on all three northern continents have yielded the distinctive thick teeth of smilotyrannids.

When the carcharodontosaurids died out in the Miocene, some smilotyrannids took over their role.

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 the recently extinct 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.

While the massive Smilotyrannus horridus patrolled the vast snow-blankets areas of Eurasia during the Pleistocene Ice, another terrifying creature patrolled the snow coated forests of Canada and Alaska, all the way down to the Pacific Northwest. Smilotyrannus silvensis, an massive extinct species of Sabre-Tyrant which roamed North America. Also referred to as the Northern Sabre-Tyrant, Smilotyrannus silvensis often roamed the vast frigdid areas in search of prey, most notably the vast amounts of therizinosaurs and possibly ceratopsians (this is due to a controversy going on in the scientific field at the moment) with gapping maw of massive teeth, roughly around the same size of the iconic Tyrannosaurus rex. The reasons on why this nightmarish beast went extinct are mostly due to climate change, change in the environment and competition from other sabre-tyrants, most notably the Thunderbird (Smilotyrannus brontus) and Buffalo Bill (Smilotyrannus billi). On a interesting note, a recently unearthed specimen of a mummified Smilotyrannus silvensis revealed that its feather coloring was vastly different when juxtaposed with the living sabretyrants and more akin to a forest bruiser. Unlike the traditional brown feathered coat with patches of grey and black, Smilotyrannus silvensis had a grey feathered coat with patches of white and black on it, most likely helping it blend in with its environment. 

Imperial Sabre-Tyrant (Smilotyrannus imperator)

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 therizinosaurs which are common sight in the area, and possibly the specialized arctic ceratopsians which travel in the hundreds. This is still under debate due to some skeptics in the research field.

Logotyrant

The imperial sabre-tyrant (Smilotyrannus imperator) is one of the few remaining examples of its kind, and has not changed appreciably since the Pleistocene. This massive 10.5 meter long predator is a runner, not as fast as its smaller cousins, the striders, but easily fast enough to pursue the lumbering arctotitans and the ceratopsians if it occasionally wonders into areas of southeastern Asia, they have been known to do this, but rarely. A sabre-tyrant relies both on strength and agility to combat these heavily armed therizinosaurs and cenoceratopsians, most notably the furciceratopids. 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.    

In the case of the furciceratopids, these represent a challenge due to their sharp two-foot horn made of solid bone and covered in keratin which can wound or even kill an imperial sabre-tyrant with no problem. As such, like their ancestors such as Tyrannosaurus before them, imperial sabre-tyrants often hunt ceratopsians by "ceratops-tipping", using their robust, crested heads to ram the furciceratopids and knock them over. In the attempt to rise to their feet, the cenoceratopsians are left vulnerable and the sabre-tyrant then quickly dispatches its victim by biting the throat or belly before backing off to let shock, disembowlement, and blood loss do the rest. Also much like Tyrannosaurus, the sabre-tyrant has a habit of decapitating cenoceratopsians to access the succulent and nutritious neck muscles.    

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.
Smilotyranbw
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.

For all their prowess in the hunt, sabre-tyrants are a dying breed. They are almost completely specialized upon the arctotitans 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.

Buffalo-Bill (Smilotyrannus billi)

The Buffalo-Bill (Smilotyrannus billi) is the largest carnivore of the Great Plains region of North America. With such a wide range of area at its disposal, it comes as no surprise that these 10-meter long monsters have a massive variety of prey items to choose from: hadrosaurs, therizinosaurs, viriosaurs, vanguards, draks, birds and mammals. Upon looking at it, it would be easily mistaken for some species of Thunderbird. However, unlike its Pacific Northwestern relative, the legs are longer and more slender than the thunderbird; a particular reason why the Buffalo-Bill more widespread throughout North America when compared to the thunderbird. A major reason for these longer legs is to run great distances in this area known for having a large area of grass.

The Buffalo-Bill is considered to be a bit of a controversial member of the sabre-tyrants. When they were rediscovered, they were thought to be either a subspecies of thunderbird or imperial sabre tyrant subspecies which made its way to North America during the Pleistocene epoch. However, a recent DNA analysis between all members of the genus Smilotyrannus confirmed that the buffalo-bill is a valid genus, but that is not the thing that the DNA analysis revealed. It also revealed that all members of the Sabre-Tyrants can trace their ancestry back to Asia and during the Eocene-Oligocene extinction event when most of the larger tyrannosaurs had vanished and the carcharodontosaurs went extinct. In North America, they were already gone when the massive herds of ceratopsians like Brontoceratops robustus had vanished. In Asia, they managed to hold on for a while until the extinction of the giant lambeosaur Sauropodimimus giganticus before they too suffered the same fate.

Unlike most species of Sabre-Tyrant which specialize in dealing with hunting and killing therizinosaurs, the Buffalo-Bill specializes in hadrosaurs, most notably the giant hmungos which march across the great plains and the smaller, but agile singers and the Yata, one of two members of the Ungulapedia which can be found in North America, as well. However, as mentioned earlier, they will prey on both the therizinosaurs during the time when the great hmungos make their journey down to warmer South America. Only a full-grown adult hmungo, which is in healthy condition, is safe from the being preyed on by these monsters. An adult Buffalo-Bill would think twice before attacking a massive 49 foot long, 10 ton fortress of flesh and tendons. If that fails, they hmungo will rely on its muscular tail to deliver nasty blow to its attacker, powerful enough to inflect damage on even the healthiest of Buffalo-Bills. While some really on their size for protection, the smaller viriosaurs while rely on speed to get away from the Buffalo Bill. Some other species, like the therizinosaurs, which in habit the Great Plains, will stand and fight with long claws. There are reports of Buffalo-Bills being killed by a careless error while hunting these heavily armed giants.

With very few forested areas and so much grassland as far as the eye can see, some wonder how this massive carnivore is so successful; especially when its habits are nothing like its prehistoric ancestors, or its modern day Eurasian cousins. Well, the answer was revealed from an event that revealed this behavior thanks to assistance of famed Tyrannosaur experts Phillip J. Currie from the University of Alberta, Sue Hendrickson, the woman who discovered the famous Tyrannosaurus "Sue" and Thomas Holtz from the University of Maryland. The following is in the words of Hendrickson who she and all of her colleges survived the encounter:

"On that day, all was peaceful and clam, the only sounds being the buzzing of insects and trumpeting bellows of hmungos en route to the warm southern grasslands of North America from their nesting grounds near the arctic, with a few species of singers and vanguards following the massive hadrosaurs. We were originally assigned to this area to observe the ceratopsians after Jack Horner, John Scannella and Denver Fowler's (they were accompaning us from Montana State University) reports of some sort of american ceratopsian were proven correct after all, they were in Canada observing the ceratopsians in that area while famous Chinese paleontologist Xu Xing was leading his students to observe some of the newly discovered fauna on the islands of Java and Sumatra. This day seemed so peaceful and so tranquil that nothing seemed out of the ordinary, but I had gut feeling that something was wrong. Holtz and Currie shared my same views as well. Little did I know my thought were to be proven correct."

"With out a warning, the tranquil feeling was interrupted by a horrific earsplitting roar and out of the tall grass charged a massive Buffalo-Bill out of the endless sea of green, straight towards the migrating hmungos. Chaos had completey erupted in that moment and the massive hadrosaurs knew it. The hmungos started to sound out and alarming bellow as they all ran for their lives, the same thing could be seen with the singers, vanguards, therizinosaurs and a currently unnamed species of drak as well. After realizing that an adult hmungo wouldn't be worth getting injured, one Buffalo Bill decided that a juvenile hmungo was the perfect target for its meal. After a minute or two chasing the small hmungo, another Buffalo-Bill rose up from the grass and had killed the helpless creature with one bite and then dropping its lifeless corpse to the floor. Fortunately, our explorers who were accompanying us survived and made it back in one piece. After discussing the terrifying experience with Dr. Horner, Horner, Holtz, Currie and I came to the realization that these species of Sabre Tyrant hunt in pairs; the male leading the charge into the herd while the larger female lies in wait for the prey to obliviously run into its gaping maw and then meet a quick, but gruesome end. I also remember Dr. Fowler stating the following, 'Well I'll be damned, that kid from the east coast was right about the Buffalo-Bill hunting in pairs.'"

Raalo (Smilotyrannus lapponensis)

URAALO
The raalo (Smilotyrannus lapponensis) 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 6.5 meters (the female is always larger) long, they can bring down full-grown mooras, dorsas and cuinoccos. During the summer, the raalo gathers fat to the base of its tail, which will be used during the long, hard winter months.

Thunderbird (Smilotyrannus brontus)

Thunderbird
The thunderbird (Smilotyrannus brontus) is the largest carnivore of the forests of the North America, most notably in the Pacific Northwest and Western United States, growing up to lengths of 8.5 meters long. They specialize in hunting the vanguards, viriosaurs, therizinosaurs, and hadrosaurs that inhabit the area. Though not as big as the imperial sabre-tyrant, it is still an intimidating and ferocious predator. 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. Interestingly, their diets depend on their distribution, they kill therizinosaurs in the north (Southern Alaska to British Columbia) and hadrosaurs in the south (British Columbia to Northern California).
Thunder2

Picture of the Thunderbird, one of the largest predators of Spec's North America, resting, notice the shorter legs. All credit for the artwork goes to Christopher Srnka.

Nian (Smilotyrannus sinensis)

Smiloprof
The nian (Smilotyrannus sinensis), is a smaller, growing up to lengths of 7 meters long, 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. The Nian can be found through out the colder parts of Asia.
Smilotyranchase

NOTOTYRANNINAE (Cazadins, Dancers and Cazarrinos)

When the first grasslands appeared in North America in the Miocene, singers and jackalopes took advantage of this new habitat, evolving adaptations of teeth and jaw musculature to grass-eating, as well as adaptations to fast, energy-saving locomotion to follow the rainfalls and to stay away from predators in the cover-poor landscape. This is, however, not a problem for a sufficiently fast and endurant errosaurid, such as a cazadin.

Soon after the first errosaurids migrated to South America during the Great American Interchange, 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 nearctic predators, the boreonychids. Thus, these deinonychosaurs occupy the most 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, notovenatorines 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 notovenatorines' 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.

Cazadins can still be found in the prairies of southern North America, but their diversity is greatest in South America which they first reached 3 million years ago and found empty of competition, the last noasaurs having died out a few hundred thousand years before.

Cazadin (Papillotyrannus pauli)

Tyrann
Cazadins (Papillotyrannus pauli) also known as White Cazadins range from just south of the Amazon to Patagonia, and eat a variety of smaller 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.

Deseado Dancer (Papillotyrannus rancori)

Ddancer
The deseado dancer (Papillotyrannus rancori) is medium sized cazadin and rather large by South American standards, growing up to lengths of 3.5 meters long. 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.

Cazarrino (Notovenator pictus)

Tyran
At 50kg and 3 meters long, 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 individuals. Cazarrino packs hunt the fleet-footed viriosaurs of the Pampas, running old or sick herd members to exhaustion before dispatching their prey with a powerful bite to the neck.

Dwarf Cazadin (Notovenator agressimus)

Errosaurusagressimus

A close relative of the cazarrino, (Notovenator agressimus), the dwarf cazadin lives along the montane streams of the southern Andes. Growing up to lengths of 75 centimeters long, 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.

Atacama Cazarrio (Notovenator atacamas)

Errosaurusfulminis

Atacama Cazarrio, Notovenator atacamas (Atacama Desert)

A native to the Atacama Desert, this species has evolved from the Cazarrino (Notovenator pictus), though it has since lost the pack-hunting tendancy. though it will gather in large groups for such occasions as the beaching of a large-bodied marine animal, N. atacamas is predominantly a solitary creature, coming together only to mate. This Errosaur is capable of both conventional running and hopping. No tests have been conducted thus far on the species to determine which is more energy efficient...though this researcher theorizes that it is similar to RL's kangaroos. They specialize in dispatching the small viriosaurs, therizinosaurs and dinoceratopsians which inhabit this area.

- Daniel Bensen , Matti Aumala, Brian Choo and David Namen

                                                        ,=E. erronis (Strider)  E.aragorni (Tagia Strider) & E. grandis (Siberian strider) 
                                          , =Errosaurus=|                                          |            
                                        ,=|
                                        | |              ,=E. mongoliensis (Khinner)
                                        | `=Errosauroides|
                                        |                `=E. anniae (Oakely
                         ,=Errosaurinae=|
                         |              |              ,=C. ferox (Siberian bruiser)
                         |              `Contusisaurus=|
                         |                             `=C. belligerans (Forest bruiser)
                       ,=|
                       | |                                 ,=S. imperator (Sabre-tyrant)
                       | |                                 |
                       | |                               ,=| ,=S. billi (Buffalo bill)
                       | |                               | `=|
                       | |                               |   `=S. brontus (Thunderbird)
                       | `=Smilotyranninae=Smilotyrannus=|
                       |                                 | ,=S. lapponensis (Raalo)
                       |                                 `=|
                       |                                   `=S. sinensis (Chinese sabre-tyrant/ Nian)
=Tyrannosauroidea=Errosauridae=|
                       |                               ,=N. pictus (Cazarrino)
                       |                 ,=Notovenator=|
                       |                 |             `=N. agressimus (Dwarf cazadin)
                       `=Notovenatorinae=|
                                         |                 ,=P. pauli (cazadin)
                                         `=Papillotyrannus=| 
                                                           `=P. rancori (Deseado dancer)

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