17 feet (5 m)
1 ton (900 kilos)
When it lived:
Late Cretaceous - 60-65 MYA
was a small, but extremely dangerous little tyrannosaur. Its
head was about the length of an adult man's arm, but it housed a pair
of large, forward-looking eyes that provided excellent binocular
vision and depth perception. It could easily spot distant prey, then
lunge forward, taking long, fast strides with its powerful hind legs.
It was very agile and could abruptly change direction. It was
also fast and it has been estimated that he could run up to 30
kilometers an in short spurts. A victim would have found it very
difficult to escape.
Nanotyrannus could grab its prey with its powerful
jaws, sinking his curved eyeteeth into the body of his surprised
victim. Like all tyrannosaurs, it had two very small front legs; they
were finished off by two fingers that had strong claws. He and may
have his arms and fingers to position the food for eating. Then again,
the carnivore versus scavenger debate lingers on so it is possible
that he fed on carrion, dead animals.
Nanotyrannus is known
from a single skull and jaw. The skull was originally thought to be
that of an
Albertosaurus, but significant differences were noticed years
after it had been prepared and stored on a museum shelf. The skull was
re-prepared, studied and re-described by Dr. Robert Baker.
Nanotyrannus had the honor of being the first dinosaur to be CAT
scanned. The skull is now housed at the Cleveland Museum of
Some paleontologists believe that Nanotyrannus is a juvenile
Tyrannosaurus rex, partly because some of the skull bones are
not fused, indicating an immature animal. A few paleontologists have
suggested it may be a type of huge
dromaeosaur (raptor). Nanotyrannus are the most primitive tyrannosaur. Its wedge-shaped skull, narrow
beak, large orbits, forward-pointing parasphenoid, and infratemporal
fenestra without any large rostral process of the quadratojugal and
squamosal make it the most troodont-like and most ornithomimid-like tyrannosaur
so far discovered.
Those that argue that Nanotyrannus is a different species
point out that Nanotyrannus had slim and razor-like teeth that
were great for slicing through flesh. Tyrannosaurus rex,
by contrast, has teeth like railroad spikes—larger and rounder for
piercing and puncturing prey and biting through bones.
In the fall of 1997, the Leonard and Arlene Zerbst family discovered a
dinosaur fossil on their ranch in Niobrara County, Wyoming. The ranch
is part of the Lance Creek fossil bed, where the fossils of many
dinosaurs from the Late Cretaceous Period have been found. The
following April 1998, it was excavated by the Black Hills Institute
It was named by the Zerbsts "Kelsey" after their three-year old
granddaughter, Kelsey Ann. Kelsey is one of the three
most complete Triceratops horridus skeletons known to science.
Kelsey is on display at the Children's Museum of Indianapolis.
What makes Kelsey particularly interesting is that among its bones
there were more than twenty Nanotyrannus teeth. This raised
interesting questions. Since so many shed, or broken, "Nano"
teeth were discovered with one skeleton, it seems unlikely that all
came from the same individual. It seems more probable that
Triceratops was attacked by a packs of Nanotyrannus.
Or did Kelsey die of natural causes and the Nanotyrannus just
happen along to scavenge on the already dead Triceratops?
Kelsey's discovery and preparation may
help resolve the debate as to the true identification of
Nanotyrannus since some researchers have maintained that this small
carnivore is, in fact, a juvenile Tyrannosaurus rex. Since no
juvenile or infant T. rex teeth have been discovered, some
scientists have suggested that the more primitive dentition of
Nanotyrannus lancensis is in reality that of a baby or juvenile
T. rex. However with Kelsey's remains, a very small, 3/8 inch long
crown of a tooth was discovered that has characteristics consistent
with a baby Tyrannosaurus rex tooth. If this preliminary
identification holds true, it may help prove Nanotyrannus as a
valid genus. The possibility that a "Nany-pack" used hunting
strategies very different from those of the small family-group hunting
strategy postulated for Tyrannosaurus rex may bolster the
argument for assigning Nanotyrannus its own genus.
In June 2001, Michael Henderson, Curator of Earth Sciences at the
Burpee Museum, led a dinosaur fossil hunting expedition to Montana's
Badlands. Volunteer dinosaur hunters Bill Harrison and Carol
Tuck discovered a six-inch-long toe jutting out of the base of a
20-foot cliff face. From there, they noticed a cross section of a
lower limb, and lower down, a foot and pelvis, which implied that
there was a significant portion of the skeleton within the cliff.
Henderson removed the toe and foot bone, marked the site, and returned
nearly one year later in May 2002 with permits, shovels, and
volunteers. They eventually unearthed a dinosaur they named, "Jane,"
after a museum benefactor.
Over the next three years, as fossil workers carefully
extracted each of Jane’s 145-plus bones from their field jackets.
Henderson examined them and compared them to the bones of tyrannosaur
specimens held in museums across North America. At first, it seemed that Jane’s skeleton had a number of features that
looked different from those of an adult T. rex. But as Henderson
surveyed juvenile tyrannosaurid dinosaurs at other museums, he
discovered that they had many of these same features.
One of the features that initially set Jane apart from T. rex is what
scientists call “tooth count.” With a total of 72 teeth, Jane has 12
more than the typical adult T. rex. However, after examining dozens of
dinosaur jaws and discussing his findings with his colleagues,
Henderson became convinced that T. rex lost teeth as it reached
And, of course, there was Jane’s diminutive size. Just half the size
of an adult T. rex, Jane could either be a full-grown small dinosaur
or a half-grown big dinosaur.
Furthermore, the new specimen is definitely not a
juvenile, said Henderson, "It has a couple of fused vertebrae and the
three pelvic bones are fused into one bone, which would only occur in
Then, one day, Henderson received an unexpected visit from Dr. Greg
Erickson, a paleobiologist from Florida State University. Erickson had
discovered a way to count growth rings inside of dinosaur bones to
tell how old they were when they died. Henderson supplied him with a
piece of Jane’s shinbone and, within a few months, Erickson had
determined that, at the time of death, Jane was 11 years old—and still
growing. He concluded that rather than being an adult
Nanotyrannus, Jane is a juvenile Tyrannosaurus rex.
In any event, the discovery is a major accomplishment for a
small museum. The discovery is the Burpee Museum's first major
dinosaur find. The museum was established in 1941 as a Works
Progress Administration project. It operated on a meager budget for
many years. It received a generous donation in the late 1990’s,
which it used to open a new paleontology wing in 1999. Since
that year the museum has held an annual paleontology festival, where
the world’s leading scientists give lectures on fossils.
The true type of
Nanotyrannus lancensis was based on an isolated skull found by
Charles Gilmore in Montana during 1942. The skull was low with a long
and narrow snout and has similar features to that of T. rex. It also had a stereoscopic view.
It was not found in in association with any other tyrannosaurid
In 1988, it was extensively examined by paleontologists M.
Williams, R. Bakker, and P. J. Currie. The examination was so
extensive that it even included a CAT-scan. They concluded that
Nanotyrannus was not a juvenile Tyrannosaurus rex, but a
different species. Other paleontologists disagree.
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