''Valley of the T. rex'' is a Discovery Channel documentary, featuring paleontologist Jack Horner, that aired on September 10, 2001. The program shows Horner with his digging team as they travel to

Hell Creek Formation The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation stretches over portions of ...

in search for

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s, while also following Horner as he presents his view of the

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur ''

Tyrannosaurus rex ''Tyrannosaurus'' is a genus of large theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosaurus'' live ...

'' as a scavenger rather than a predator, as it is often portrayed in popular culture.

Plot

The program shows Horner and his digging team as they travel to the

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

, United States, and dig up dinosaurs. The program also follows Horner as he presents arguments for his case of ''Tyrannosaurus'' as a scavenger. Horner argues that there is not the slightest evidence that ''Tyrannosaurus'' hunted its own prey. Instead, Horner believe the evidence should be clear that ''Tyrannosaurus'' was a scavenger, lamenting that "no one likes that idea". Some of Horner's arguments for a scavenger-only ''Tyrannosaurus'' are: *Forelimbs: ''Tyrannosaurus''‘s short forelimbs seem like they could not hold on to struggling prey. Horner argues that predators have well developed forelimbs with

claws A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

to hold prey down while the jaws do the killing, while ''Tyrannosaurus'' could not use its forelimbs for much more than to "scratch its belly". Horner believes the upper arm of ''Tyrannosaurus'' would have been embedded in muscle, and not externally visible in life. If ''Tyrannosaurus'' stumbled and fell while trying to run, the small forelimbs would not be enough to brake the fall, and it would get fatal injures. *Speed: Horner argues that ''Tyrannosaurus'' must have been too slow to chase down prey, and also points out that some specimens of ''Tyrannosaurus'' have longer

thigh In human anatomy, the thigh is the area between the hip ( pelvis) and the knee. Anatomically, it is part of the lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of ...

bones than

shinbone The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

s. According to Horner, this is not the case in fast-running animals like '' Saurornitholestes'', which have longer shinbones than thighbones. Horner describes ''Tyrannosaurus'' as "either a really slow runner, or just a walker." *Brain and senses: Horner suggests that ''Tyrannosaurus'' had a poorly-developed sense of sight, and would not be a good predator. Its huge

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex ( ...

indicates "a tremendous sense of smell", used to find carcasses. *Jaws and teeth: ''Tyrannosaurus'' had powerful

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

s and robust teeth. Horner argues that ''Tyrannosaurus'' used them for crushing

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

s, as modern scavengers like hyenas do to feed on marrow when the flesh of carcass has rotted away. Predators teeth are normally thin and sharp for slicing flesh. ''Tyrannosaurus'' becomes depicted as Horner imagines it: a big, slow-moving animal, traveling across the landscape in search of a carcass. Horner thinks ''Tyrannosaurus'' would have a repulsive look: A dark body, a red head, and it would give off a terrible smell. This would help it frighten away other meateaters, like

dromaeosaurs Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

, from carcasses. His description of T. rex is "big, nasty, and stinky."

About the program

*When Horner examines the anatomy of ''Tyrannosaurus'' in the program, he mostly use the specimen MOR 555 ("Wankel Rex") as reference. This specimen was found by Kathy Wankel in 1988, and was the first specimen of the genus with a well-preserved forelimb. *The program features Horner and his team as they dig up 5 new ''Tyrannosaurus'' specimens. *The computer animation in the program was made by Meteor Studios. Some of the animations are taken from one of Discovery Channel's other programs about

s, '' When Dinosaurs Roamed America''.

Criticism

Since ''Valley of the T. rex'' was shown on television, it has been met by criticism. Many of the arguments Horner uses to support his case have been examined by other

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s, who do not agree that they conclusively show that ''Tyrannosaurus'' was an obligate scavenger.Holtz T.R.jr. "A critical re-appraisal of the obligate scavenging hypothesis for Tyrannosaurus rex and other tyrant dinosaurs", in Tanke D.H., Carpenter K & Skrepnick M.W. ''Mesozoic Vertebrate Life'' ( Indiana University Press, 2001), p. 370-396. As for ''Tyrannosaurus''‘s short forelimbs, it has been pointed out that predators like

wolves The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly un ...

and

hyenas Hyenas, or hyaenas (from Ancient Greek , ), are feliform carnivoran mammals of the family Hyaenidae . With only four extant species (each in its own genus), it is the fifth-smallest family in the Carnivora and one of the smallest in the cla ...

do not use their front legs to take down prey. Moreover,

, like ''Tyrannosaurus'', have jaws and teeth to crush bone, yet they use it to hunt their own prey. In the program, Horner measures the leg bones of MOR 1128, or "G-rex", one of the skeletons which were shown in the program as it was dug up. The narrator says that "G-rex" was found in a rock layer 90 meters below where "Wankelrex" was found, and Horner says "G-rex" are thought to be 3 million years older than other known specimens (like "Wankelrex"). Horner also says that "G-rex" have thighbone and shinbone of equal length, while "Wankelrex", have longer thighbone than

. Horner argues it is an indication that ''Tyrannosaurus'' over time lost the ability to run and evolved to more specialization as a walking scavenger. It has been argued by Garner, however, that the shinbone of "Wankelrex" are restored from broken fragments,
http://www.cmnh.org/dinoarch/2001Sep/msg00522.html
'. making it inappropriate as reference in comparative morphology. Also, according to other reports, "G-rex" also had longer thighbone (1.26 meters)Larson P.L., "Variation and Sexual Dimorphism in Tyrannosaurus rex", in Larson P.L. & Carpenter K, ''Tyrannosaurus rex, the Tyrant King'' (Indiana University Press, 2008), p. 103-130. than shinbone (1.12 meters).Horner J.R. & Padian K. (2004)
"Age and growth dynamics of Tyrannosaurus rex"
''

Proceedings of the Royal Society of London B ''Proceedings of the Royal Society'' is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: * Series A: for papers in physical sciences and mathematics. * Series B: for papers in life s ...

'' 271(1551): p. 1875-1880. Holtz also points out that longer thighbones than shinbones is a condition also found in horses, which are fast running animals. A shorter shinbone might be compensated by a relatively long

metatarsus The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

, which is seen both in horses and tyrannosaurids. Other scientists have argued that ''Tyrannosaurus'' could have had a well-developed sense of sight with

binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...

, typical of a predator,Stevens K.A. (2006)
"Binocular vision in theropod dinosaurs"
, ''Journal of Vertebrate Paleontology'' 26(2): p. 321-330. and a well-developed sense of smell in ''Tyrannosaurus'' could have been used for hunting, rather than just finding carcasses. Evidences for a predatory lifestyle in ''Tyrannosaurus'' includes discoveries of skeletons from herbivorous dinosaurs like '' Edmontosaurus'' and ''

Triceratops ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is one ...

'', with evidence of healed bitemarks on them, indicating they survived attacks from big predators, possibly ''Tyrannosaurus''.

References

{{reflist

External links

Clips from ''Valley of the T. rex''
Documentary films about dinosaurs Discovery Channel original programming 2001 television specials Films about Tyrannosaurus