by scarlett hunt

By Scarlett Hunt

For many years palaeontologists focused on finding bones.

The problem is that a dinosaur has only one skeleton. The skeleton has a few hundred bones and that’s it: some get washed away, others get eaten & some rot before they can turn into fossils.

But…

The same dinosaur can make hundreds of thousands of footprints in its lifetime. So palaeontologists have millions of possible footprints out there waiting to be discovered.

Just finding the footprint is not enough.

Palaeontologists try to figure out which type of dinosaur made the footprints. Then they try to find out extra information about the dinosaur from examining its tracks.

Here are some tips for identifying a dinosaur by its footprints.

The size of the footprint is close to the size of the foot which made it. Some sauropod tracks are over a metre long and are as deep as bathtubs. One of the smallest theropod tracks ever found is from Nova Scotia.

www.ourworld.compuserve.comwww.ldeo.columbia.edu

REPRINT FROM DINOSAUR TRACKS by TONY THULBORN Chapman & Hall, 1990

The shape of the footprint is similar to the shape of the foot which made it.

Palaeontologsts will sometimes place pictures of bones over top of a picture of the footprint to help identify it.

Scientists use Roman Numerals to count fingers and toes. They are numbered from the inside to the outside. For example your thumb would be “I” and baby finger would be “V”.

Each finger or toe is also part of a phalangeal formula for the hand or foot. A human hand is “2,3,3,3,3” because the thumb has 2 bones and each other finger has 3. A theropod foot has the formula “3,4,5”.

Small Raptor FootSmall Allosaurus Hand

Number of toes (digits) helps palaeontologists tell who the track maker was.

Sometimes not all the toes make a mark in the footprint.

Most two-legged (bipedal) dinosaurs actually had 4 toes on each foot. One, called the hallux, was small and held up in the air. Hallux marks rarely show up in a footprint.

The soft parts of an animal’s foot can change the shape of a footrpint. For example, Robert Bakker thinks that duckbilled hadrosaurs had plump paws and would have a “webbed” footprint.

Dinosaur tracks known from Broome, Western Australia:

Each kind of dinosaur had different shapes of feet so they made different shapes of footprints.

Footprints can tell us whether the animal walked on

2 legs, 4 legs or switched back & forth

Two-legged (bipedal) dinosaur trackways contain similarly sized and shaped prints in pairs. Each print switches from left to right. They usually make very narrow trackways which appear to be in a straight line.

The feet of a four-legged (quadrupedal) animal are different sizes and shapes. The front foot is called the manus. The back foot is called the pes. The pes (back) prints are larger and wider in shape than the manus (front) prints. The front print is usually slightly in front of the back print on each side of the trackway.

By studying dinosaur footprints, palaeontologists now know that quadrupedal dinosaurs walked diagonally. Trackways show the front (manus) print slightly in front of the back (pes) print on each side of the trackway.

Animation of the foot order of a preserved sauropod trackway.

www.projectexploration.org/ jobaria/Rearing4.html

Quadrupeds tend to walk in a palm-first (plantigrade) manner. Their toes are usually blurry. Bipeds usually walk in a toe-first

(digitgrade) manner. These tracks have easy-to-see toes.

•Chart taken from: “An Overview of Dinosaur Tracking” by Glen Kuban

Fossilized tracks can show skin texture, claws and skin creases. The clearest footprints are those made on slightly wet ground. The muddier the ground was when the footprint was made, the fuzzier the footprint is.

In Davenport Ranch in Texas, tracks of 24 apatosaurus are preserved in a group. The largest prints are on the outside while the smaller prints are in the middle of the group. Robert Bakker thinks that the bulls or senior cows may have guarded the young. From looking at tracks, Martin Lockley believes that large sauropods led their herds and walked in a staggered (or spearhead) formation.

Palaeontologists examine patterns in footprint tracks. They try to figure out if the dinosaur was alone, with a group of the same kind of dinosaurs, or was being followed by someone else.

Site in Eastern Utah NOTE: A theropod track is perpendicular to the sauropod trackway

Dinosaur Ridge is geographically located west of Denver, Colorado

The figure below is taken from Fossil Footprints of the Dinosaur Ridge Area. This new map of the main Dinosaur Ridge tracksite was completed in December 1994, by Dr. Martin Lockley of the University of Colorado at Denver. The map shows many more tracks (335) and trackways (at least 37) than on previous maps. Ornithopod (e.g. Iguanodon) tracks are shown in blue; theropod (e.g. Coelurus) tracks are shown in red. Also shown is a trackway orientation diagram for all trackways and arrows marking the travel directions of small- and large ornithopods. This main tracksite marks where planned new construction will upgrade viewing and teaching facilties at the site, which is now surrounded by a protective fence. This tracksite is located on the east side of Dinosaur Ridge -- see the track symbol on the area map

R. McNeil Alexander discovered that dinosaur hip height equals 4 times the foot print length. He then figured out

how to calculate a dinosaur’s speed by measuring only its footprints.

V= 0.25*(stride length)1.67*(leg length)

-1.17*(gravitational constant)0.5

Locality Est. Leg Length Speed (km/hr) Gait

large theropod 2.0 8 walk

small theropod 1.0 13 run

large sauropod 3.0 3.6 walk

small sauropod 1.5 4.0 walk

ornithopods 0.14-1.6 15.5-17.3 run

small theropods 0.13-0.22 11-12.6 run

small theropods 1.0 30-40 fast run

human runner 1.1 36 sprint

race horse 1.6 61.2 fast run

ostrich 1.5 54 fast run

According to Professor Paul Eric Olsen in his lecture notes on www.ldeo.columbia.edu

On-line calculator for determining dinosaur speeds on the University

of Sheffield, England webpage: www.shef.ac.uk/~es/DINOC01/ dinocal1.html

Thulborn, 1990

By looking at footprints, palaeontologists can tell a lot about the animal who made the tracks. However, there will always be some guessing because no one has ever found a footprint with a dinosaur’s foot bones still in it.

Image: Stephen Gatesy, Brown University