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How were they formed?
Where can they be found?
The Project Scope - The Purpose of This Webpage
Naming Prints
Interpreting the Prints
Glossary of Ichnological and Geological Terms
Conclusion

How were they formed?
How and why were the footprints of dinosaurs from the Eastern North America preserved?  Fortunately during the separation of the tectonic plates that made up the large continent Pangea, the Appalachian mountain range provided the rock and sediments that filled in this rift basin.  This action caused the formation of large mudflats that continued to accumulate sediments, throughout the Triassic and early Jurassic period, and formed what is called the Newark basin.  Over 30 million years of accumulating sediments (and basalt layers) formed this basin which can exceed more than 7 kilometers in certain areas.  The relatively fast accumulation of sediments allowed for the preservation of footprints, trackways, and in very few cases bones.

But footprints and trackways are only preserved under special conditions.  When the mud is too wet the footprint is formed but quickly fills in (mud collapse).  If anything is preserved it's thin and most likely deformed.  If the mud is too dry the track is faint and barely detectable.  However, not only does the mud have to be the proper consistency, a layer of biofilm (algae - also referred to as biolamination) has to be present or the foot of the dinosaur would not have cleanly separated from the mud.  A muddy foot does not leave distinguishable tracks.  But under the proper conditions a print would have been formed, then the following events have to take place to preserve it.  The mud has to dry out then the footprint has to be filled in by the accumulating sediments.  Given enough time and pressure (from the weight of sediments or basalt above) the rock lithicates and the sediments solidify.  When the rock is split a natural imprint (impression, negative relief, or mold) on the bottom layer and a natural cast (positive relief) from the top layer of sediments is revealed.

It is my belief (and I might be wrong) that without the biolamination the rock will not cleanly separate if the sediments below and above the track layer are too similar.  Sometimes the footprint is so well preserved that the scales of the foot are easily seen.  Some dinosaurs were also heavy enough to deform layers of sediment below the surface; such impressions are called "undertracks" or "ghost prints" because they reside under the original track layer.  Although it seems that very specific conditions must be met in order for a print to be conserved, one most consider the number of prints one creature could have created during its lifetime.  In fact most prints are found in a few strata (layers) within the almost 7 km of sediments deposited over 30 million years.  It's very common to find a productive layer (strata) containing prints because only at that time were the conditions right to preserve prints.  Interestingly is the large slab of prints housed by the Rutgers Geology Museum where the same species left many prints but they differ in the depth of the print.  Perhaps they were left by the same creature but at days or weeks apart as the mud was drying out.  For a more extensive look into how they where formed click here.

Where can they be found?
Footprints and trackways can be found anywhere accumulating sediments formed, preserved, and where the strata can be cleaved apart.  Footprints are not limited to only the Triassic and Jurassic periods.  Although the focus of this project is within a 30 million year time span from the Triassic to early Jurassic (235 to 204 million years ago or mya), the "Dinosaur Footprints and Trackways From Various Locations" webpage has samples of footprints from various locations around the world from the early Permian period to the Cretaceous period (295 to 65 mya).  And needless to say, footprints are not limited to only dinosaurs.  Trackways from insects, reptiles, amphibians, worms, and trilobites from a wide range of periods and in almost all continents are the fossil traces left by creatures.  So vast is the science of Ichnology that this project has been narrowed down to a manageable focus on vertebrate ichnology of the East coast of North America.

The Project Scope - The Purpose of This Webpage
That leads us to our project scope.  This project is devoted to the study of prints from the Triassic and Jurassic periods of the East coast of North America.  Below I've taken a chart created by Paul E. Olsen & Emma C. Rainforth, Dept. of Earth and Environmental Sciences, Columbia University and linked the formations below to a formation specific webpage.  The system created allows the cataloging of the prints found by formation.  In addition, fauna specific webpages will be created so that one can establish relationships regarding the age span (during what periods does the fauna appear and end), location span (which formations or States can the prints be found in), trending size changes (are the prints getting larger over time?), etc.  Eventually, by expanding the scope of this project, prints from the East coast of North America can be compared to similar prints found around the world.

Formations of the North East Coast "Central Atlantic Margin Rift System Late Triassic" Paul E. Olsen & Emma C. Rainforth Dept. of Earth and Environmental Sciences Columbia University
PERIOD	AGE (starts mya)	Deerfield(MA)	Hartford(CT)	Newark(NJ)	Gettysburg(PA)	Gettysburg& Culpeper(MD)
Early Jurassic Early Triassic	Sinemurian (203.5) Hettangian (208.0) Rhaetian (209.5) Norian (223.4) Carnian (235.0)	Turners Falls Fm Deerfield Bt Fall River Beds Fm not present Sugar Loaf Fm not present	Portland Fm Hampden Bt E Berlin Fm Holyoke Bt Shuttle Meadow Fm Talcott Bt New Haven Fm not present	Boonton Fm Hook Mt Bt Towaco Fm Preakness Bt Feltville Fm Orange Mt Bt Passaic Fm Lockatong Fm Stockton Fm	Booton Fm Hook Mt Bt Towaco Fm Preakness Bt Feltville Fm 1 Orange Mt Bt 2 Passaic Fm 3 Lockatong Fm 4 Stockton Fm 5	not present* not present* not present* not present* not present* Tibbstown/Catharpin Creek Formations Bull Run Fm* (Gettysburg Fm*) Manassas Sandstone not present*

1 - Pottstown or Upper Brunswick Shale, 2 - Jacksonwald Basalt, 3 - Perkasie-upper or Lansdale-lower Shales, 4 - Gwynedd Shales, 5 - Norristown Shales
* - I'm working on identifying the current names of the formations in MD

Late Triassic - Early Jurassic Dinosaur Ichnofaunas, Eastern North America and Southern Africa

Emma C. Rainforth, Dept. of Earth and Environmental Sciences, Columbia University

Naming Prints
Unfortunately where bones are found footprints are not typically present, and where footprints are found bones aren't.  It is an extremely rare occurrence to find the remains of a dinosaur and the creature's last steps.  Hence, footprints are given separate names because we can never be exactly sure what species could have formed them.  There are a few cases where scientists have agreed on which (type of) dinosaur may have left the footprints.  But typically scientists are hesitant to do so.

Interpreting the Prints
But can anything be learned from the tracks or are we just collecting fossils to fill our shelves?  Well if you're fortunate to find a trackway, one could learn a few things about the creature.  One can determine easily if the creature walked on two feet (bipedal motion) or four feet (quadrupedal motion).  The front foot of a quadruped is called the manus, whereas the back foot is called the pes.  Quadrupedal dinosaurs seemingly walked like most diagonal walkers do nowadays, by moving the right manus and left pes at about the same time, alternating with the left manus and right pes.  Trackways show the manus print slightly in front of the pes print on each side of the trackway.

The posture of the creature can also be determined, whether it walked with a sprawling gait, semi-erect posture, or erect posture.  The sprawling gait is an indication of a primitive posture and consists of having the limbs extended away from the body.  This posture creates a sinuous motion of the body during walking.  Modern lizards have this posture and can move very fast.  However, the sinuous motion of the body alternately collapses the lung on each side, preventing breathing during running.  That is why lizards have to stop completely and pant after they run, even though they risk capture.  Crocodiles have a semi-erect posture (sometimes called semi-improved).  When moving slowly, their posture is sprawling, but when they run, their body straightens out and they pull their legs nearly under their body.  When they carry their bodies more nearly erect, they are said to exhibit a "high walk".  In this posture the lungs can still operate.  Some crocodiles are even capable of galloping.  Galloping is the fastest type of longer term quadrupedal motion in which all four feet are off the ground simultaneously during one phase of the step cycle.  The erect posture (often called fully improved) is where the limbs are held directly under the body.  This allows easy breathing while running.  And most importantly, the erect posture allows for full-time bipedal motion, thus freeing the hands for grasping.  more to be said on direction of prints, herding, ghost or underprints, varying walking or running speeds and the effect on the print left behind, etc. the Triassic/Jurassic sandpit
Here's a great 5 minute video with Stephen Gatesy, Martin Lockley, and Emma Rainforth
High Bandwidth from AMNH video © 2005     Dial-up (56K) from AMNH video © 2005

Glossary of Ichnological and Geological Terms
For your convenience here is a link to a glossary of ichonological and geological terms. Glossary

Conclusion
The science of ichnology is quite vast covering all fossils (not including bones or teeth) left behind from any living creature.  This would include footprints and trackways, tail drags, insect burrows or borings, tooth marks (gnawings), eggs and nests, gastroliths (gizzard stones), and coprolites (dung).  It is also irrespective of time or location.  Thus again a reason to focus this project to a specific area.

PLEASE NOTE: I would be very interested if you have a photo of a footprint or trackway from the Newark Supergroup: MA, CT, NY, NJ, PA, MD, VA, NC, or SC.  Or from Europe: France, Portugal, Spain, or Africa.  Please e-mail me a high quality photograph and some information about the footprint.  To verify authenticity I will need at a minimum the formation it was found in, the town where it was found (be as specific as you wish), the year it was found, and the size of the footprint (or place a coin or ruler in the picture).  A photo of a pretty print is useless to this webpage unless I know where it came from and where it best fits on this page.  Photos from museums will also be useful but let me know which museum owns it.  When I get the chance I will post your photos on this webpage.  If you give me your first name or nickname (for credit) I'll post it with the photograph.  THANKS!!!

Note the T-Rex foot, the three toes in front and the claw in the back of the foot (dew claw or hallux) (AMNH). Notice a different T-Rex foot lifting off the ground but the claws are driven into the ground and hooking up (AMNH). Note the ??? foot, the three toes in front and the hallux on the side of the foot (AMNH). Note the Duckbill dino foot, the three toes in front (AMNH). Note the ??? foot, the four toes in front and the hallux lower on foot (AMNH).

Henry standing next to a Eubrontes trackway from the AMNH. A close-up of two Eubrontes prints. The full Eubrontes trackway.

A Hadrasaur trackway from the AMNH. A close-up of a Hadrasaur print. A replica of a portion of the Paluxy trackway (AMNH).

Photos for fun click here

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