Tyrannosaurus rex, the ‘Tyrant Lizard King’, was the thesis-statement of theropod evolution. Discovered in 1905, by Barnum Brown, and named by his mentor, Professor Henry Osborn, T. rex was among the very last dinosaurs to evolve. Exceeding forty feet and six tons, it was the largest of the fleet-footed, strong- jawed tyrannosaurs, it was a super-predator evolved specifically to kill large prey in a single strike. With its firepower focused solely in the massive head, T. rex’ jaws were a biological weapon of mass destruction seen only in the likes of the dromaeosaur sickle-claws or the fangs of saber-toothed cats – present in an animal the size of a large elephant. Known from barely a dozen partial skeletons, and a varied assortment of bones, T. rex was a monster of such terrifying proportion that it continues to exist to this day in the half-life of popular culture, sixty million years after it’s own extinction. Casts of the specimens listed below, are on display all over the world. KING OF THE TYRANT LIZARDS Despite the discovery of larger theropods – the carcharodont carnosaurs and the derived megalosaur, Spinosaurus - T. rex remains the single most destructive predatory force that ever evolved on land. In spite of its great size, T. rex retained adaptations for speed similar to its ostrich-mimic relatives. It also had forward-facing eyes, giving it advanced binocular vision, and was the largest-brained of all dinosaurs. It was its jaws, however, that truly separated the T. rex from the field. Tyrannosaurs in general, but most particularly, T. rex itself, represented the most powerful biters in terrestrial Earth history, The wide, heavily reinforced skull boasting jaw and neck muscles nearly as powerful as its legs, with recent studies indicating bite forces approaching seven tons – totally eclipsing the bite forces of even other theropods, (see graph). And as opposed to the slashing blades of the narrow-skulled, carcharodont, Giganotosaurus, T. rex’ banana-thick teeth, arranged like a bladed ice-cream scoop, actually bit OUT huge chunks of flesh. This massive bite, combined with its thick, muscular, shock- absorbing neck, gave the Tyrannosaurus an attack similar to the modern white shark – an especially devilish variation of the theropod attack and retreat strategy - a massively destructive first strike that left its target incapacitated or dead – a necessary adaptation considering the large and dangerous horned dinosaurs that comprised the bulk of its prey. Dated speculation that T. rex was a pure scavenger never really deserved serious consideration, but researcher, Jack Horner recently revived the idea, mostly as a publicity stunt, capitalizing on the concurrent boom in public interest in dinosaurs, ushered in by Jurassic Park, as Horner wrote in his own book that he doesn’t believe T. rex was an obligate scavenger, and only says so in order to deliberately stir debate – and, of course, grant funds. BITE FORCE OF T. REX (Pounds/Newtons) CHALLENGERS FOR THE TITLE T. rex had plenty of competition in the ‘big and terrible’ category. As it turns out, almost every branch of theropod dinosaurs produced individuals in the same size class as T. rex. Torvosaurus tanneri was a forty-foot megalosaur, and Allosaurus amplexis was a similarly large Jurassic allosaur. Two contenders in particular, however, have emerged as the top threats to the title of King of the Dinosaurs. First, is the giant carcharodont carnosaur, Giganotosaurus carolini (along with its close relatives, Carcharodontosaurus, Mapusaurus, and Tyrannotitan) (Page 16), and the other is Spinosaurus aegyptiacus (page 17). But while both of these species likely exceeded T. rex’ largest size (although there was certainly overlap between them), T. rex was a much more advanced, much more powerfully armed animal. One look at the skull of T. rex compared to any large spinosaur (see illustrations) clearly demonstrates that it would be ridiculous for a spinosaur to snap a T. rex’ neck the way it did in Jurassic Park 3 – a battle would likely be more like an alligator snapping the head off a stork. Giganotosaurus, on the other hand, itself a big game hunter, was a more worthy challenge to T. rex’ throne. T. REX VS SUCHIMIMUS But the massive straight razor jaw of the carnosaur, (Spinosaur) designed to attack large, slow sauropods, lacked the one-shot kill-power of a rex jaw – necessary to kill fast, dangerous ceratopsians. And while Giganotosaurus would certainly be capable of inflicting a fatal injury on a rex (which Spinosaurus likely could not), the pairing would be like a muscular pit-bull versus a German Shepard (see Illustrations, photos) GIGANOTOSAURUS (Carcharodont) TYRANNOTITAN (Carcharodont) T. REX CMN 9380, HOLOTYPE: THE FIRST REX Holotype - CMN 9380 (11.9 m, 5.7 tons): This was the first substantial remains of T. rex ever described. In truth, another specimen, named ‘Dynamosaurus’ was found earlier, but ‘Tyrannosaurs rex’ was described first, earning the species the name, ‘Tyrant Lizard King’. It was on this fragmentary skeleton that Charles Knight based his first famous T. rex mural, incorrectly placing the eye too far forward due to incomplete skull bones - a trait translated into popular culture as Knight’s image became enshrined in paleo art, and was the basis for famous cinematic T. rex, like Ray Harryhausen’s Gwangi, and the King Kong T. rex. ‘Gwangi’ is a good example of the thick-boned ‘robust’ morph, particularly visible in the skull and vertebra. AMNH 5027: THE FACE OF T. REX AMNH 5027 (11.8m, 5.7 tons): For nearly a century this specimen WAS the face of T. rex, the basis for Charles R. Knight’s second, most famous T. rex mural, and, in fact, it was researcher/artist, Gregory Paul’s skeletal illustration of this particular specimen (see illustration) that eventually became the Jurassic Park T. rex. The mount at the American Museum of Natural History – a gracile morph - has been combined with the legs and arms of the robust-morph Holotype, to create the world’s first full skeleton of T. rex – albeit a paste-up Frankenstein version made of mixed parts. NOTE: While 5027 is a gracile morph, it is still one of the top four or five largest T. rex ever found, indicating that the robust morph was not necessarily the largest in terms of sheer size, as two of the top four largest specimens are gracile. NOTE: Ironically, while 5027 is the face of T. rex, it is one of the specimens being considered as a second species: Tyrannosaurus x. BHI 3033: STAN BHI 3033 (11.8m, 5.6 tons): ‘Stan’ is a large gracile morph, with a particularly large skull, all the more intimidating for the fact that the teeth have partially slid from their sockets, giving Stan a horrific ‘fanged’ appearance. Stan’s large head, perhaps indicates that the gracile morph – male or female – certainly was no less a formidable predator, and might, in fact, have done the bulk of the hunting, just like the lighter, faster modern lioness do today, with the larger male lion only lending its extra strength and bulk when necessary. If tyrannosaurs pair-bonded like many modern birds, a pack of two parents and offspring could have functioned in much the same way. All this is speculative, but Stan is another example that the gracile morph is maintained, even at full maturity and large size, as opposed to being a factor of age. FMNH PR2081: SUE: BIGGEST T. REX OF ALL FMNH PR2081 (Formerly BHI 2033) (12.3m, 6.1 tons): Sue is the largest, most complete T. rex in the world – a thickly boned, massive monster, just as famous for the legal wrangling behind it’s ownership and sale (which actually sent researcher Peter Larson from the Black Hills Institute to prison). While complete, Sue is a little bit crushed from top to bottom – particularly its skull - giving mounted casts the impression the animal was more squat and ungainly than it actually was. As the largest T. rex, Sue would have scaled about the same as the type specimen of Giganotosaurus, although would have been several feet shorter (see illustration page 2). And while there have been several reports of even larger T. rex discovered, these have all either been in error, or refer to extremely fragmentary remains, and all indications are that Sue represents the upward size limit for T. rex. LACM 2345: SAMSON MOR 555: WANKLE REX LACM 2345 (12.2m, 6 tons): Samson is another large MOR 555 (11.6m, 5.4 tons) “Wankle’’s Rex” named robust morph – often described as ‘large as Sue’, but after discoverer, Kathy Wankle, is a good example of while it is only a biscuit shorter, and taller at the hip, the gracile morph – a scrawny, scarecrow of a T. rex the fellow standing in front of the skeleton below (with that leads one to wonder if it might have simply a T. the disturbingly visible bald spot), is yours truly, and to rex version of a ninety-pound weakling. On the other my eye, Samson is not nearly as massive as Sue. It hand, that’s just compared to a massive rex like Sue, is, however, a good-looking, mostly non-crushed as MOR 555 is still a large animal. No skeletal skeleton (unlike the distorted, albeit complete remains drawings exist, but photographs show a widely spaced of Sue), and might be the second or third largest T. ischium bone consistent with other gracile morphs rex, next to Peck’s Rex (page 9). (page 13), a possible indication that a gracile bone structure was a way to keep weight down, while maximizing body cavity space for laying eggs.