Identifying Track Makers By Scarlett Hunt The importance of fossil trackways to palaeontology is noted in this quote from Lockley & Hunt:
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By Scarlett Hunt
“Every tetrapod animal can potentially make hundreds of thousands, even millions, of tracks in a lifetime, whereas it only has one skeleton consisting of a few hundred bones.”
Dinosaur Ridge, Colorado
palaeontologists whether the trackmaker moved bipedally
(two-legged), quadrapedally (four-legged) or
with a combination of both.
prints in pairs. Each print alternates -usually from left to right.
They make tend to make very narrow trackways which may
appear to be in a straight line.
If there are predominantly hind prints but a few front prints, the animal is considered a facultative biped, meaning that it usually walked on its back legs but was able to walk on all four when it chose.
When only hind prints are visible the animal is considered an obligate biped, meaning that it walked on only its back legs.
The manus and pes prints of quadrupedal dinosaur tracks usually have different sizes and shapes. The rear prints are larger and broader in shape than the front. Trackways show the front print slightly in front of the back print on each side of the trackway.
The front foot of a quadruped animal is called the manus, whereas the back foot is called the pes.
In Clayton Lake State Park, Oklahoma approximately 500 footprints of iguanodonts are remarkably preserved . The three-toed footprints indicate that the animal usually walked bipedally but occasionally leaned forward to walk on all fours. The tracks are easily recognized because of their square heels and lack of claw marks.
Site in Eastern Utah NOTE: A theropod track is perpendicular to the sauropod trackway
Footprint anatomy and characteristics are used to differentiate between possible track makers.
According to the author of www.palaeo.gly.bris.ac.uk /Palaeofiles/Tracks/Report9, “The stature and build of the legs and feet will affect the area over which pressure is exerted. Wider feet will have a “snowshoe” effect and therefore leave less of an impression. Column-like legs with compact feet will carry the mass of the body over a smaller area. This will exert a high pressure and produce a more profound disturbance of the substrate.”
The soft tissue of an animal’s foot can greatly affect the shape of a print. It can be entirely different from what you would expect to find based on the skeleton alone. For example, Robert Bakker speculated that duckbilled hadrosaurs had plump paws similar to a camel’s foot. This would produce a webbed footprint.
PROBLEM: One mystery is why the front prints show only blunt digits marks, whereas skeletal remains of sauropod front feet include a large pointed claw. Glenn Kuban speculates that perhaps the single claw was held in an elevated position or else the claw was tucked within the fleshy pad at the front of the foot.
Size is another consideration when examining dinosaur footprints. Obviously, the size of the footprint is relative to the size of the foot which made it.
Sauropods. Up to 80 cm in length.
Stegosaur. Five-fingered manus prints 21 cm in length, associated with three-toed foot prints. Only stegosaurs are known to have had this combination of five fingers/ three toes.
Wintonopus latomorum ("Foot from Winton"). Ornithopod tracks ranging from 3 to 27 cm (averaging 7-8 cm) in length
Megalosauropus broomensis. Large theropod tracks 53 cm in length, from a creature perhaps 9 to 10 metres in body length.
the identity of a track maker.
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”.
When counting phalanges (bones) in the digits, they are numbered from the palm of the hand outward.
Small Allosaurus Hand
Small Raptor Foot
Each finger or toe is also part of a phalangeal formula for the hand or foot. For example 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”.
Animation of the foot order of a preserved sauropod trackway.
Fossilized tracks can show significant anatomical features. Details of skin texture, claws, skin creases and tail marks are sometimes preserved in the fossil record.
Fossils of Anomoepushave been found in Holyoke, Massachusetts, and New Jersey, USA. The tracks were named by E. B. Hitchcock in 1848.
NOTE: The tail drag below & the front prints at the far left.
“The only way to demonstrate conclusively that any one species of dinosaur was responsible for a particular type of footprint is to discover the skeleton of the animal preserved at the end of its fossil trackway.” (Thulborn, 1990).
Dinosaurs with tridactyl feet tended to produce three-toed footprints, those with slender feet tended to produce narrow footprints, and so on. In other words, it may be assumed that each footprint is a reasonably faithful impression of the foot that made it. The obvious way to discover which sort of dinosaur was responsible for a trackway is simply to match up the footprints with dinosaur feet of the most appropriate shape and size. Such matching up of dinosaur footprints against dinosaur feet has long been standard practice (see diagram).
Sometimes the fossil footprint is compared directly to an actual foot skeleton; alternatively, one may work from the evidence of the footprint alone, attempting to visualize the shape of the foot that might have produced it. On occasion, it is useful to follow the reverse procedure, by predicting what sort of footprint would be produced by a particular foot skeleton. This last exercise entails something more than laying out the foot bones on a sheet of paper and tracing round them with a pencil. Instead it is necessary to arrange (or at least envisage) the foot bones in a life-like attitude, with the bases of the digits lifted from the substrate and the metapodium inclined up and backwards. Then, when they are projected on to the horizontal plane, these inclined elements will appear properly foreshortened, as they would be in an actual footprint.
Eubrontes giganteus tracks is at Dinosaur State Park in Rocky Hill, CT
Using Alexander’s equation, the follow speeds were calculated by R. A. Thulborn (1982, University of Queensland, Australia):
Sauropodamorphs to 5 km/h
(same as person walking)
Stegosaurs and ankylosaurs to 6-8 km/h
Most sauropods walked 12-17 km/h,
max. of 20-30 km/h
Large theropods and ornithopods to 20 km/h
Ceratopsians to 25 km/h
Small theropods, ornithopods to 40km/h
Ornithomimids to 60 km/h
People are estimated to run up to 23 km/h
(fast sprinting speed)
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
Palaeontologists look for evidence of sophisticated social behaviour in trackways and for evidence of interaction between animals. Unfortunately patterns of movement in groups or individuals is very speculative at best.
Other critics point out that the paces are rather small and show unhurried gaits. They concede that the carnosaur may have been stalking the sauropods from a distance, or more likely was simply using the same path at a different time.
In Davenport Ranch, 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 inferred that the bulls or senior cows may have guarded the young.
Martin Lockley speculated from tracks that large sauropods led their herds and walked in a staggered or spearhead formation.
Palaeontologists try to reconstruct food chains and ecological systems from trackway evidence.
“Tracks should provide a more valid census of a living community than remains at the majority of skeletal sites.” (Lockley, 1986)
Palaeontologists have tried to make a census of the community by counting tracks. Tracks have been identified as belonging to Dimetrodon, Varanops, Gilmoreichnus, an animal from the family Araeoscelis, and a temnospondyl amphibian (cacops?),
Because of the regular spacing of tracks of the same type of animal many believe that these tracks are the oldest evidence of herding behaviour in animals. They suggest that the tracks indicate a “follow the leader” pattern of movement.
In Brule, Nova Scotia palaeontologists have found evidence of a primitive conifer forest ecosystem from the Permian Period (285 MA). Animal tracks meander along the forest floor between fossilized Walchia stumps found in their original growth positions.
Thulborn & Wade 1989
The impact and effects of variables need to be considered carefully: nature of the substrate; erosion & weathering; infillings; laminations; kinematics & irregular movements; unconformities & hiatuses; undertracks; and rock change.
Sauropod footprint from the Islet of Fenoliga, Istria.
In “An Overview of Dinosaur Tracking” Kuban states that “When a track is made on very soft substrate, some sediment may slump back into the print. This phenomenon, called mud-collapse or mud back-flow, often distorts and reduces track features. Digit marks may become mere slits. Soft sediment can also result in undertracks. If the substrate is very firm, portions of the foot may record only lightly, if at all.”
Tracks in Courtedoux, Switzerlandof at least 14 sauropods and two tracks of a carnivor.
A three-dimensional computer reconstruction (top) shows a theropod foot at three stages in creation of a deep track, moving right to left. A photograph of a deep Greenlandic footprint is shown below it.Image: Stephen Gatesy, Brown University
Erosion can distort or blur track features or even obliterate them. It can also create depressions of its own which can be mistaken for fossil tracks.
An overlying layer may be scoured away with some remains trapped in some of the track depressions. This may exhibit little or no topographical relief.
“Increasing speed will alter the angle at which the foot contacts the ground and affect the force with which the foot strikes the substrate…
A foot print is usually made in three phases, termed touch-down, weight-bearing and kick-off. (Thulborn & Wade, 1989).
Many animals perform a small rotation of their feet during the progress of a footfall (Phil L. Manning, pers.comm.). This rotation, within the print, will naturally obscure some of the finer details of the foot structure. However, if recognized it may tell us a great deal about the trackmaker’s locomotion.”
This three-dimensional computer image reconstructs theropod foot movements through sloppy mud. Penetration through the ground surface is shown in red. The first toe, which is not reversed as in modern birds, creates a rearward pointing furrow (a,b) as it plunges down and forward. The sole of the foot leaves an impression at the back of the track (c) because it is not lifted as the foot sinks. All toes converge below the surface and emerge together from the front of the track (d). Image: Stephen Gatesy, Brown University
Undertracks can occur when tracks are made upon other previously laid tracks.
Rock change may destroy evidence of tracks.
A hiatus is a geological period of time without deposition containing fossils. No trackways are formed.
Paleontologists will continue to painstakingly examine evidence from the past in order to reconstruct and describe it for others. They will skillfully examine direct evidence, make interpretations, consider the affects of variables, and may encounter monumental problems along the way. In the future we may see more importance placed upon Ichnology (the study of trace fossils) and on the identification of species from their tracks.