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Troodon

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

                     iTroodon

                             Conservation status

   Extinct (fossil)
            Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Saurischia
   Suborder:   Theropoda
   Infraorder: Coelurosauria
   Family:     Troodontidae
   Genus:      Troodon

                                Binomial name

   Troodon formosus
   Leidy, 1856

                                  Synonyms

     * Polydontosaurus Gilmore, 1932
     * Stenonychosaurus Sternberg, 1932
     * Pectinodon Carpenter, 1982

   Troodon was a relatively small, bird-like dinosaur from the Late
   Cretaceous Period (75-65 mya). Discovered in 1855, it was among the
   first dinosaurs found in North America. It is believed to have been one
   of the most intelligent dinosaurs.

Characteristics

   This small dinosaur was around 2 m (6.5 ft) in length, 1 m (3 ft) tall,
   and weighed 60 kg (130 lb). Its eyes were large (perhaps suggesting
   nocturnal activity) and slightly forward facing, giving Troodon some
   depth perception.

   Troodon (pronounced "Tro-odon") is Greek for "wounding tooth",
   referring to the dinosaur's serrated teeth (although these may actually
   have been adapted for herbivorous feeding, see below). Its diet
   consisted of smaller animals, including mammals and perhaps a
   significant amount of plant material as well.

   Troodon had long 'arms' that folded back like a bird's and its 'hands'
   possessed partially opposable thumbs. It had large, sickle-shaped claws
   on its second toes, which were raised off the ground when running. This
   claw is common in the group Maniraptora, to which Troodon belongs.

   Troodon had one of the largest known brains of any dinosaur, relative
   to its body mass (comparable to modern birds). Eggs have also been
   discovered, in nests.

Distribution

   Troodon is known from the Judith River Formation of Montana, the Judith
   River Group of Alberta, the Horseshoe Canyon Formation of Alberta, the
   North Slope of Alaska and in the famous Hell Creek Formation of the
   USA. There is some evidence that Troodon favored cooler climates, as it
   seems to have been particularly abundant in northern areas and during
   cooler intervals, such as the Early Maastrichtian. It seems unlikely
   that all of these fossils, which come from localities hundreds or
   thousands of miles apart, separated by millions of years of time,
   represent a single species of Troodon. However, further study and more
   fossils are needed to determine how many species of Troodon existed.

Biology

   Troodon had very long, slender limbs, suggesting that the animal was
   able to move quite quickly. Although originally thought to have been a
   predator, there is some evidence that Troodon may either have been an
   omnivore or a herbivore. The jaws met in a broad, U-shaped symphysis
   similar to that of an iguana and the teeth were leaf-like, bearing
   large serrations like those of herbivorous dinosaurs. In addition, the
   teeth were short but broad, with wear facets on their sides. In these
   respects Troodon was again more like plant eating dinosaurs than
   carnivores such as Dromaeosauridae. A specimen of Troodon is known from
   Montana, sitting atop a clutch of eggs.

History

   Head and neck of Dale Russell's Troodon sculpture, from the Natural
   History Museum, London.
   Enlarge
   Head and neck of Dale Russell's Troodon sculpture, from the Natural
   History Museum, London.

   Troodon was originally spelled Troödon (with a diaeresis) by Joseph
   Leidy in 1856, which was officially amended to its current status by
   Sauvage in 1876.

   The Troodon tooth was originally classified as a "lacertian" ( lizard)
   by Leidy, but re-assigned as a megalosaurid dinosaur by Nopsca in 1901
   (Megalosauridae having historically been a wastebin taxon for most
   carnivorous dinosaurs). In 1924, Gilmore suggested that the tooth
   belonged to the herbivorous pachycephalosaur Stegoceras, and that
   Stegoceras was in fact a junior synonym of Troodon (the similarity of
   troodontid teeth to those of herbivorous dinosaurs continues to lead
   many paleontologists to believe that these animals were omnivores). In
   1945, Charles Hazelius Sternberg rejected the possibility that Troodon
   was a pachycephalosaur due to its stronger similarity to the teeth of
   other carnivorous dinosaurs.

   The first specimen of Troodon that was not a tooth, then referred to
   its own genus (Stenonychosaurus), was named by Sternberg in 1932, based
   on a foot, fragments of a hand, and some caudal vertebrae from Alberta.
   A remarkable feature of these remains was the enlarged claw on the
   second toe, which is now recognized as characteristic of
   Deinonychosauria. Sternberg initially classified Stenonychosaurus as a
   member of the family Coeluridae. Later, Sternberg (1951) speculated
   that since Stenonychosaurus had a "very peculiar pes" and Troodon
   "equally unusual teeth", they may be closely related. Unfortunately, no
   comparable specimens were available at that time to test the idea.

   A more complete skeleton of Stenonychosaurus was described by Dale
   Russell in 1969, which eventually formed the scientific foundation for
   a famous life-sized sculpture of Stenonychosaurus accompanied by its
   fictional, human-like descendant, the "dinosauroid". Stenonychosaurus
   became a well-known theropod in the 1980s, when the feet and braincase
   were described in more detail. Phil Currie, reviewing the known
   Troodontidae in 1987, reclassified Stenonychosaurus inequalis as a
   junior synonym of Troodon formosus. This synonymy has been widely
   adopted by other paleontologists, and therefore all of the specimens
   once called Stenonychosaurus are now referred to as Troodon in the
   recent scientific literature.

Classification

   The type specimen of Troodon has caused problems with classification,
   as the entire genus is based only on a single tooth from the Judith
   River Formation. Since the discovery of the original tooth, postcranial
   material from a related animal were given the name Stenonychosaurus.
   More complete remains of Stenonychosaurus convinced most
   paleontologists that it in fact was the same animal as the original
   tooth, so the name Stenonychosaurus was replaced with its senior
   synonym, Troodon. Other genera, including Polyodontosaurus and
   Pectinodon, have also been assigned to Troodon based on the assumption
   that this particular tooth type is limited to only a single type of
   dinosaur. For this reason, the future of the name Troodon itself is
   dubious--in similar situations, genera based on teeth have been
   abandoned in favour of names based on better remains. Familiar names
   like Deinodon and Trachodon have been abandoned in this way, and
   further research may require Troodon be replaced with Stenonychosaurus.
   In a chapter of the 2005 book Dinosaur Provincial Park, Phil Currie
   (one of the leading experts on North American troodontids) resurrects
   the type species of Stenonychosaurus (S. inequalis) within the genus
   Troodon as Troodon inequalis (Currie, 2005).

The "Dinosauroid"

   In 1982, paleontologist Dale Russell, curator of vertebrate fossils at
   the National Museum of Canada in Ottawa, speculated on how evolution
   would have proceeded if the troodonts had survived the extincton of the
   dinosaurs. Russell speculated that a species like Troodon would have
   grown smarter and taken on a human-like appearance. Russell partnered
   with taxidermist and artist Ron Sequin and together they made a model
   of what a derived, intelligent Troodon would look like, naming their
   fantasy creation a " Dinosauroid" (Russell & Séguin, 1982). While a few
   paleontologists, such as David Norman (1985) and Cristiano dal Sasso
   (2004) have regarded this as a plausible line of reasoning, others,
   such as Gregory S. Paul (1988) and Thomas R. Holtz Jr., consider it
   "suspiciously human" (Paul, 1988) and argue that a large-brained,
   highly intelligent troodontid would retain a more standard theropod
   body plan. Darren Naish has suggested the ground hornbill as a better
   model for a hominid-mimicking terrestrial theropod.

   In 1997, an episode of Star Trek: Voyager featured humans encountering
   a humanoid-reptilian alien species called the Voth, who were eventually
   discovered to be the descendants of intelligant dinosaurs who had fled
   Earth for a distant corner of the galaxy when threatened with mass
   extinction. , .

In popular culture

   Troodon also featured in ITV's Prehistoric Park in 2006. It was shown
   as a highly intelligent scavenger.

   Troodon are shown in two episodes Dinosaur Planet. In one, a pack of
   dwarf Troodon make "friends" with a Pyroraptor, in another, a pack of
   Troodon attack a flock of Orodromeus.

   Troodon also featured in Science Channel's Dino Lab 2006.
   Retrieved from " http://en.wikipedia.org/wiki/Troodon"
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   with only minor checks and changes (see www.wikipedia.org for details
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