Dinosaurs »Dinosaur Anatomy
How do scientists know what the dinosaurs
looked like? No-one can say for sure, but there are some
lines of evidence in the fossil
record, and from studies of modern animals. Putting it all
together is like the detective work in solving a difficult
murder case.When you see a colour painting, or an animation,
of a dinosaur as a living animal, this has been based on
a series of steps in reconstruction:
• The skeleton is rebuilt from
the bones that are extracted from the rock.
• The muscles can be laid on with some confidence,
since each end of the muscle is fixed into the bone,
and marks may be seen on the fossil bones.
• Other soft parts, like the guts, eyeballs,
tongue, and so on can be added partly by guesswork,
and comparison with living animals.
The skin texture may be reconstructed precisely,
since impressions of dinosaur skin have been fossilized.
There are even a few rare cases of organic preservation
of dinosaur skin.
• The colour is entirely
guesswork. Was Tyrannosaurus blue with yellow spots,
or maybe you like red stripes? Colours are based
on modern animals, and a bit of inspired imagination
by the scientists and artists.
Tyrannosaur teeth were uneven, which placed
most of the force of the bite on just a
few teeth at a time, giving them more penetrating
power.When a number of teeth penetrated
the fibers, then the tyrannosaur just tore
on the dotted line.
Dinosaur skin is amazing. We do have some
preserved skin impressions. Most of them
show polygonal scales in different groupings. Duckbills had a background of small scales
with patches of larger scales every now
The patches were bigger and more common on the back. On
the crest the impression was more like a rooster’s
comb. Horned dinosaurs had similar scales, but a little
larger. Instead of the patches that duckbills had, for a
change of pattern the horned dinosaurs had large rounded
scales with a rosette of polygonal scales making the change
back to the basic pattern.The big round scales were more
common on the back and sides. Long-necks like Seismosaurus
had large scales, about 2-3 cm, with small bumps, about
2 mm, all over them. They also had a fringe down the back
that stood up and were tall thin triangles. Dinosaurs could
have bony scales like the bumpy ones on alligators. They
could be scattered almost anywhere, but were more common
on the back and sides. In the Stegosaurus,
some of them formed huge plates that went down the back,
and even the spikes on the tail were these bony scales.
In the Ankylosaurs, they formed a “shell” over
the whole body. In the horned dinosaurs, they attached to
the skull and formed the ornate horns of the frills. Some
dinosaurs even appear to have had feathers!
Duckbill Dinosaur Skin Impression
Horned Dinosaur Skin Impression
Stegosaurus Tail Spike
Stegosaurus Back Plate
The horned dinosaurs were from North America. There were
two major types; the centrosaurines,
and the chasmosaurines,
The centrosaurines generally had a big nose horn, although
some just had a “nasal boss”.
They had more ornate frills than the chasmosaurines. The
chasmosaurine generally had the frontal horns (brow horns)
as the major horns. The chasmosaurines had a hollow cup
at the base of the frontal horns that must have given them
a nice clacking sound when they fought with each other.
Some of the skulls have holes in the bones that look like
they were made by fighting with other horned dinosaurs.
The horn had a bone core covered with chitin - like your
fingernails. Cow Horn in cross section, showing the bone
core and the chitinous sheath.
Chasmosaurine Frontal Horns.
Here are castings of two dinosaur brains. The one on
the right is a Maiasaurua
and the pictures on the left are a Tyrannosaurus.
Wes cut a cow skull in half so that you can see where the
brain would be. The cow brain is much bigger than any dinosaur
brain. We have even bigger brains and feel that intelligence
is very important. Dinosaurs did amazingly well with their
little brains and never had to worry about global thermonuclear
war or MAD - Mutual Assured Destruction.
Of course, they couldn’t know about the comet that
was on a path leading to a collision with the earth. After
all, their best astrophysicist had a brain the size of a
Dinosaurs must have eaten something, and a lot
of it. It is fairly easy to imagine that Tyrannosaurs ate
other dinosaurs - and anything else that they
wanted. But what did the plant-eating dinosaurs
eat? Plants have been evolving for millions
of years. When most of the dinosaurs lived,
there were no grasses. Early in the age of
dinosaurs there were no plants with flowers,
but cycads seem to have been common. Cycad
seeds would have been good and cycad trunks
have a lot of starch in them . Some
people eat cycads today. Another tree that
was common was the Ginkgo. Ginkgo
leaves are edible and the seeds are considered a delicacy
in China. There is some evidence from gut contents
and droppings that duckbills ate conifers -
like Christmas trees.
Claws, like horns, have a bony core with a hard chitin
sheath. Some claws allowed the predatory dinosaurs to tear
into the flesh of their victims. Claws could also have been
used to hold down prey while the dinosaur used its powerful
jaws and serrated teeth to rip off large chunks of flesh.
The foot seen at the left is from a small tyrannosaur. The
claw in the middle is the killing claw from the back leg
Raptor. It was used to rip a long deep gash
in another animal, like a kick boxer with a switch-blade.
The sharp curved claw of the Allosaurus
was a meat hook. It allowed the Allosaurus, seen on the
right to grab and hold on to another animal.
The large vertebra has a hole in the side. That
is the opening to the air space in side of the
vertebra. In many dinosaurs the back
bone is hollow.
This hollow space made the bones lighter. The
back bone allows the body to bend while forming
a strong support for the body.
A whip-tailed Seismosaurus
could possibly thrash a predator even approaching from the
front. Poor Allosaur.
One estimate based on Diplodocus is that
the tip of the tail could exceed the speed of sound. It
would have generated a sonic boom when it was whipped. So
much energy would be in the whip and released as a boom
that it would have been as loud as the blast of
a 16-inch gun from a battleship! Seismosaur is
even bigger - about 50% bigger. That is at least double
the power! Besides being a weapon, the sound may
have been used to communicate with other Seismosaurs.
If you know that a big animal can make loud trumpeting
sounds from its head, what does that tell you about its
behavior? Why would a dinosaur need to have this peculiar
feature? You can find answers by looking at modern animals
that share similar features. An elephant makes loud trumpeting
sounds through its trunk. Elephants use these sounds for
two main reasons; to communicate with other members of its
herd and to warn away its enemies. Scientists who study
elephants have found that there are many different sounds
they make to communicate different things. There
are sounds of warning, sounds of fear, and sounds for excitement,
happiness and sadness. Many paleontologists think
used its ability to make sounds in much the same way as