A current depiction of an adult Tyrannosarurus rex
MEET THE TYRANT LIZARDS!
When you say the word dinosaur to the average person, he might mention one of those big, lumbering herbivores like Brontosaurus or the slightly smaller Hadrosaurs (a.k.a “Duck Billed Dinosaurs”). She might even talk about Triceratops with its prominent horns or the Stegosaurs with their strange spinal “fins.” But ask anyone, and the most frequently mentioned name is Tyrannosaurus rex.
And with good reason. Thanks in great part to the six films in the Jurassic Park and Jurassic World franchises not to mention the numerous Walking With Dinosaur “documentaries” of the 90’s and early 2000’s, many hundreds of millions of people across the globe have an image of the fleet-footed, roaring beast that relentlessly hunts its victims--there’s simply no escaping this nine-ton monster with the steak-knife teeth.
While much of what we hear and see in the lore about T. rex is based on a certain amount of factual evidence, there’s a great deal that’s either wrong (in the case of the Hollywood movies) or missing (in the BBC and Discovery Channel shows)--including the fact that T. rex sported primitive feathers and had anatomical features that we now associate with birds such as a three-toed foot like a vulture or hawk, “hollow” bones, and a wishbone. Further, this remarkable beast was only one member--and one of the last--of a fairly extended family of Tyrannosaurs (the Tyrannosauroidea) that includes smaller dinosaurs like Guanlong and Dilong who thrived millions of years before T. rex. as well as its nearly contemporary smaller 2-ton cousin Albertosaurus.
Have fun exploring the many links on this page. You’ll find articles, illustrations, and videos that will give you a sense of the current state of research regarding this most remarkable beast and its always fascinating relatives.
GEOGRAPHY: LOCATION, LOCATION, LOCATION
Before we look at some of the remarkable ancestors of Tyrannosaurus rex, let’s get a sense of what the world looked like before and during his reign.
Approximately 252 million years ago, the Earth underwent an extraordinary extinction event. “Many geologists and paleontologists contend that the Permian extinction occurred over the course of 15 million years during the latter part of the Permian Period (299 million to 252 million years ago). However, others claim that the extinction interval was much more rapid, lasting only about 200,000 years, with the bulk of the species loss occurring over a 20,000-year span near the end of the period. The Permian extinction was characterized by the elimination of over 95 percent of marine and 70 percent of terrestrial species.” (Encyclopaedia Britannica, 2019; John P. Rafferty, Editor.) The causes remain ambiguous, though these are the most often mentioned: Temperature crises as the continents began to pull apart; alteration of the carbon cycle; population explosion of methane-producing microbes; volcanic activity in what is currently Siberia; a comet or asteroid strike. Whether one or all of these instigated the great die-off, the world was left open to whole new groups of animals, including the dinosaurs.
The Paleozoic Era was over; the Mesozoic had begun, an Era divided into three distinct Periods: the Triassic, the Jurassic, and the Cretaceous.
The earliest dinosaurs emerged around 230 million years ago during the Triassic; many of them were bipedal, and several of those species would eventually evolve--around 165 million years ago (during the middle Jurassic)--into the great carnivorous bipeds that make up the Tyrannosaur family, of which Tyrannosaurus rex is but one, late-blooming member.
All well and good; but what kind of world did these animals live on?
What you have below are a series of maps. To get a larger image, just click on the picture. As you can readily see, the land masses of the planet were moving around greatly--splitting and converging just as they are today. Just as we experience earthquakes and volcanoes, so the dinosaurs would have been familiar with these catastrophic upheavals as well. And, also like today, the shifting continents would change everything from ocean currents and temperatures to atmospheric composition, which in turn would alter the evolution of plant and animal life. So when we say the earliest members of the Tyrannosaur lineage--like Kileskus, Proceratosaurus, and Guanlong--lived between 167 and 160 million years ago, we must realize that the planet was geographically and geologically quite different from the planet that T. rex roamed on 68 to 66 million years ago.
THE EARLY CRETACEOUS (approx. 140 million years ago)
NORTH AMERICA approximately 100 million years ago
THE LATE CRETACEOUS PERIOD
66 MILLION YEARS AGO--when the comet hit
Below you’ll find 22 of the relatives of T. rex--a number that continues to grow because each year new members of the Tyrannosaur family are described. Further, it’s important to note that a number of these species lived concurrently, often on the same continent, and just as often separately on different land masses. So, as they used to say on television newscasts, "stay tuned"; what we think we know today about numbers and morphology may be (will be?) upturned tomorrow. As already cited, probably the greatest example of our changing understanding of this lineage was the discovery that all tyrannosaurs bore feathers at some point (or for the entirety) of their lifetimes. When the original Jurassic Park films were released in the early-to-mid-1990s--the same time the remodeled dinosaur halls opened at the American Museum of Natural History--no one knew that. A mere twenty years later, it’s all about the feathers--not to mention the strange headcrests on basal tyrannosaurs. Who knows what the next twenty years will bring?
Tyrannosauroidea (meaning ‘tyrant lizard forms’) is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus rex itself. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe, Asia, South America and Australia. (Paleontology World)
Dating from the Middle Jurassic Period, Kileskus is a contender for one of the earliest tyrannosaurs. The partial skull remains have revealed the presence of a crest that rose up from the snout. Beyond this the only thing that can be said about Kileskus is that it appears to belong in a basal position of the Proceratosauridae, the group thought to belong alongside the earliest tyrannosaurs.
NOTE: The Proceratosauridae are a branch of the Tyrannosauroidea Super Family. They lived from approximately 165 Mya (Jurassic) to 120 Mya (Cretaceous). As you will read and see in the following links, there are differences of opinion regarding exactly where to place some species:
Proceratosaurus is a genus of small-sized (~3 metres (9.8 ft) long) carnivorous theropod dinosaur from the Middle Jurassic of England. It was originally thought to be an ancestor of Ceratosaurus, due to the similar small crest on its snout. Now, however, it is considered a coelurosaur, specifically one of the earliest known members of Tyrannosauroidea, the clade of basal relatives of the tyrannosaurs. The type specimen is held in the London Museum of Natural History and was recovered in 1910 at Minchinhampton while excavating for a reservoir. Minchinhampton an ancient market town on a hilltop, 4 miles (6.4 km) south south-east of Stroud, Gloucestershire, England, in the Cotswolds.
Named from the Chinese words guan, meaning 'crown', and long, meaning 'dragon,’ in reference to its flashy head-crest, Guanlong is the most elaborate of any known theropod dinosaur. The species name comes from the Chinese word wucai meaning 'five colours' and refers to the multi-hued rocks at Wucaiwan, the badlands where the fossils were found. Guanlong wucaii is one of the most primitive tyrannosaurs known. It hunted its prey 95 million years before T. rex lived. According to the Australian Museum, the name is pronounced GWON-long woo-kay-eye.
Yutyrannus (meaning "feathered tyrant") is a genus of tyrannosauroid dinosaurs which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali—all found in the rock beds of Liaoning Province—are currently the largest-known dinosaur specimens that preserve direct evidence of feathers (as of 2019).
Sinotyrannus (meaning "Chinese tyrant") is a genus of large basal proceratosaurid dinosaur, a relative of tyrannosaurids which flourished in North America and Asia during the Jurassic and early Cretaceous periods. Sinotyrannus is known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Though it is not much younger than primitive tyrannosauroids such as Dilong, it is similar in size to later forms such as Tyrannosaurus. It was much larger than contemporary tyrannosauroids; reaching a total estimated length of 9–10 m (30–33 ft), it is the largest known theropod from the Jiufotang Formation.
Dilong (which means 'emperor dragon') is a genus of basal tyrannosauroid dinosaur. The only species is Dilong paradoxus. It is from the Lower Cretaceous Yixian Formation near Lujiatun, Beipiao, in the western Liaoning province of China. It lived about 126 million years ago. This small, earlier relative of Tyrannosaurus rex was the first tyrannosaur found with direct evidence for feathers. Dilong paradoxus is one of the smallest tyrannosaurs known, reaching only about two metres in length, and had an unusual Y-shaped skull crest (two ridges running along its snout). Unlike later tyrannosaurs, most early tyrannosaurs such as Dilong had three fingers and relatively long arms.
Dating back around one-hundred and fifty-two million years ago, Stokesosaurus is one of the earliest representatives of the tyrannosaur lineage, being only slightly later than Guanlong. At up to four meters long, Stokesosaurus resembled the juvenile forms of later tyrannosaurids, and was a fleet-footed predator relying upon speed to catch prey. Stokesosaurus possibly remained at these smaller sizes because other larger predators such as Allosaurus were dominant at the time.
Eotyrannus lengi (meaning "dawn tyrant") is a species of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. The etymology of the generic name refers to the animals classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.
Xiongguanlong ("Grand Pass dragon") is a genus of tyrannosauroid dinosaur that lived in the Early Cretaceous of what is now China. The type species is X. baimoensis (White Ghost Castle), described online in 2009 by a group of researchers from China and the United States, and formally published in January 2010. The genus name refers to the city of Jiayuguan, a city in northwestern China. The specific name is derived from bai mo, "white ghost", after the "white ghost castle", a rock formation near the fossil site. The fossils include a skull, vertebrae, a right ilium and the right femur. The rocks it was found in are from the Aptian to Albian stages of the Cretaceous, between 125 and 100 million years ago.
THEN: Classic 1897 painting of DRYPTOSAURUS by Charles R. Knight
NOW: A more recent depiction of DRYPTOSAURUS by webartist Durbed
DRYPTOSAURUS with proto-feathers
Dryptosaurus is a genus of tyrannosauroid that lived approximately 67 million years ago during the latter part of the Cretaceous period in what is now New Jersey. Dryptosaurus was a large, bipedal, ground-dwelling carnivore, that could grow up to 7.5 m (25 ft) long. Although largely unknown now outside of academic circles, a famous painting of the genus by Charles R. Knight made it one of the more widely known dinosaurs of its time, in spite of its poor fossil record. First described by Edward Drinker Cope in 1866 and later renamed by Othniel C. Marsh in 1877, Dryptosaurus is among the first theropod dinosaurs known to science.
Bistahieversor (meaning "Bistahi destroyer") is a genus of tyrannosaurid dinosaur. Bistahieversor existed in the Late Cretaceous Hunter Wash member of the Kirtland Formation (New Mexico), which has been dated to 74.55 ± 0.29 Mya. The name Bistahieversor comes from the Navajo Bistahí, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness where it was found, and eversor, meaning "destroyer." The skull of Bistahieversor has many features that are considered primitive for the Tyrannosaurid group, but most importantly, a noticeable depth that is lacking in other, and later, tyrannosaurid species. This is significant because it was once thought that only the later and more advanced tyrannosaurids, like Tyrannosaurus itself, had deeper snouts. Bistahieversor was also joined by the tyrannosaurid Teratophoneus (see further description of this dinosaur below on this page), another of its kind that seems to have been restricted to the Southern US even though it also lived during the Campanian. Both Bistahieversor and Teratophoneus display more basal tyrannosaurid morphology, and both are known only from the southern area of what was once called Laramidia. This was the western half of North America that was separated from the eastern half by the Western Interior Seaway. Rising sea levels combined with mountain ranges being pushed up could have isolated the southern tyrannosaurids from the North, causing the retention of the more basal features seen in Bistahieversor, so late in the geological timescale.
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