How Dinosaur Footprints Preserve Behavior

At Lark Quarry in central Queensland, Australia, more than 3,300 dinosaur footprints are packed onto a single rock surface, most of them pointed in the same direction, as if a crowd of small animals had all moved through the same spot around the same time. No skeleton was involved in reconstructing that scene. A layer of hardened mud, roughly 95 million years old, recorded something a bone never can: an animal in motion. This article explains how paleontologists read speed, gait, and group behavior directly out of ancient footprints, and why that evidence has to be handled with more caution than it usually gets credit for.

Why footprints are trace fossils, not body fossils

Dinosaur footprints belong to a category of fossils called ichnofossils, or trace fossils — fossils that preserve evidence of what an organism did rather than the organism's actual body. The scientific study of these traces is called ichnology, a term that covers footprints, trackways, burrows, nests, and even fossilized dung (coprolites). A dinosaur skeleton tells you what an animal was built like. A trackway tells you what it was doing on one particular day of its life.

The process that turns a footprint into a fossil is more fragile than most people assume. An animal has to step into sediment soft enough to hold a clear impression, typically damp mud, fine sand, or volcanic ash, but not so soft that the print collapses back on itself. That impression then has to avoid destruction long enough to be covered by a new layer of sediment, whether from a flood, a windblown dust layer, or a slow buildup of lake mud. Only after burial does the slow chemical process of lithification turn the sediment into rock, locking the impression in place. Skip any one of those steps and the print simply disappears, which is part of why intact trackways are far rarer than isolated bones, even though millions of dinosaurs must have left billions of footprints over roughly 165 million years of dinosaur history.

Because a trackway is a physical record of an animal actually moving, it can answer a different set of questions than a skeleton can. A femur can tell an anatomist how an animal's hip joint was built and roughly how it should have walked in theory. A trackway shows how it actually walked, on a specific day, on a specific patch of ground. That distinction matters because bone structure sets a range of possible movement, but only footprints show which part of that range an animal actually used, and whether it was walking alone or traveling with others.

Ichnologists also use a separate naming system for trace fossils, called ichnotaxa, rather than assigning tracks directly to a body-fossil species. A track gets its own scientific name, like Brontopodus for the broad, rounded sauropod prints found across Texas trackway sites, independent of which specific dinosaur genus made it. That separation exists precisely because a footprint's shape depends on foot anatomy and how weight was distributed across it, not on the full skeleton, so more than one dinosaur species can, in principle, leave a nearly identical track.

Calculating speed from stride length and hip height

The best-known biomechanical tool for estimating dinosaur speed from footprints comes from a 1976 paper by British zoologist R. McNeill Alexander, published in Nature. Alexander noticed that when he plotted speed against stride length for a wide range of living animals, humans, horses, small rodents called jirds, elephants, and ostriches, the relationship followed a consistent mathematical pattern once he accounted for each animal's hip height. He worked out this relationship in part by observing his own children walking and running on a beach, then confirmed the pattern held across species of very different sizes.

Alexander's formula expresses speed as a function of the Froude number, a physics concept that compares the momentum of a moving body to the pull of gravity acting on it, originally developed for ship-hull design in the 19th century. Applied to walking animals, it captures the basic physical fact that a longer stride relative to leg length means an animal was moving faster relative to its own size, whether that animal is a two-meter-tall ostrich or a twelve-meter-long sauropod. The formula is commonly written as v = 0.25 × g^0.5 × SL^1.67 × h^-1.17, where v is speed, g is gravitational acceleration, SL is stride length measured directly from the trackway, and h is hip height, which cannot be measured directly from a footprint alone and instead has to be estimated.

That estimation step is where most of the uncertainty in dinosaur speed calculations creeps in. Ichnologists commonly approximate hip height as roughly four times the footprint length, a rule derived from proportions in living animals and confirmed where possible against dinosaurs whose foot size and hip height are both known from complete skeletons. Because that multiplier is an average drawn from modern analogues, not a fixed law, the resulting speed estimate always carries a margin of error, and Alexander himself later cautioned against treating the output as a precise number rather than a reasonable range.

Alexander derived his speed formula in part by measuring how stride length scaled with speed in his own children walking and running along a beach in Norfolk, England, then confirmed the same mathematical relationship held across animals ranging from small rodents to elephants before applying it to dinosaur trackways.

Can a single footprint really tell you how fast a dinosaur was moving?

No. A single isolated print shows foot shape and size, not speed, because speed calculations depend on stride length, the distance between two successive footprints from the same foot. A full trackway with several consecutive steps is required, since even one wrong stride measurement or a stretch where the animal briefly stopped can distort a single-stride estimate. Ichnologists generally average measurements across multiple strides in a trackway before reporting a speed range, and even then present it as an estimate rather than an exact figure.

Why does a wider spacing between footprints mean faster movement?

A longer stride relative to an animal's leg length reflects greater forward momentum per step, the same relationship that makes a person's running stride visibly longer than their walking stride. Alexander's formula converts that ratio into an estimated speed by comparing it to the Froude number pattern observed consistently across living land animals of vastly different sizes, from small mammals to elephants.

What footprint depth and shape reveal about the ground itself

Speed is not the only information locked into a trackway. The depth of a footprint and the way sediment was pushed up and out around its edges can indicate how firm or waterlogged the ground was at the moment the animal walked across it. A print that sinks deep with sediment squeezed up into a raised rim around the edge suggests soft, saturated mud, while a shallow, crisp print with minimal displacement points to firmer ground. Ichnologists sometimes describe this displacement pattern using the term "extramorphological features," a way of separating what the substrate did to the print's shape from what the animal's actual foot anatomy contributed.

This matters because the same dinosaur can leave visibly different-looking tracks on different substrates, which is part of why matching a footprint to a specific species purely by outline is so unreliable. A print made in thick, wet mud can look proportionally wider and less detailed than a crisp track left by the same species walking across firmer, sandier ground minutes later. Paleontologists studying a trackway site have to account for substrate variation across a single bedding surface before drawing conclusions about the animals that made the tracks, since a change in footprint shape halfway across a site might reflect a change in mud consistency rather than a different species entirely.

Overlapping trackways, where one trail physically crosses and disturbs another, provide a rough timeline of events on a single surface. The trackway that shows disturbance from a crossing print is, by definition, the older one, since a fresh footprint disrupts whatever impression was already there, while a trackway laid down afterward simply overlays undisturbed ground. At sites with many crossing trails, like Dinosaur Ridge west of Denver, Colorado, ranked by paleontologists as one of the most significant dinosaur tracksites in North America, researchers can use these overlaps to reconstruct which animals moved through an area first and roughly how much time separated different visits, especially where distinct sediment layers separate different trackway events entirely.

Dinosaur Ridge preserves mostly Iguanodon-like footprints likely made by an ornithopod dinosaur, along with theropod tracks, crocodilian tracks, and prints from bird-like ornithomimid dinosaurs, all within the same Dakota Hogback rock formation. The variety at a single site like this illustrates a broader point: a trackway surface is essentially a snapshot of everything that crossed a particular patch of ground during whatever window of time the sediment stayed soft enough to record footprints, which can range from hours to years depending on local conditions.

Trackway feature	What it can indicate	Documented example
Stride length and spacing	Approximate walking or running speed, via Alexander's formula	Speed estimates published for Winton Formation trackways, Queensland
Print depth and sediment displacement	Substrate firmness (firm, waterlogged, or partially dried) at time of formation	Extramorphological variation documented across single bedding surfaces
Multiple parallel trackways, same direction	Possible group or herd movement among same-species individuals	Davenport Ranch, Texas — 23 sauropod trackways moving in parallel
Overlapping trackways	Relative sequence of which animal passed first	Cross-cutting trails at multi-species sites like Dinosaur Ridge, Colorado
Size-graded parallel trails	Possible age-structured group movement (juveniles alongside adults)	Interpreted at some sauropod trackway sites by paleontologist Martin Lockley

Different features of a single trackway can each answer a different question about the animals that made it, from how fast they moved to whether they were traveling as a group.

Group behavior evidence from Texas sauropod trackways

Some of the strongest documented evidence for group movement in dinosaurs comes from trackway sites in central Texas, studied extensively by fossil collector and paleontologist Roland T. Bird beginning in the late 1930s. Bird documented sauropod trackways at several sites in the region, including the Paluxy River near Glen Rose, where the "Main Tracklayer" of the Glen Rose Formation preserves both broad sauropod trackways, formally classified as the ichnogenus Brontopodus, and far more numerous three-toed theropod tracks, likely left by large carnivorous dinosaurs walking the same shoreline.

A separate site Bird documented in the early 1940s, Davenport Ranch in Bandera County, Texas, produced a more striking pattern: 23 individual sauropod trackways, all oriented in the same direction, moving roughly parallel to one another across the same bedding surface. Bird interpreted this as evidence the animals had passed through as a coordinated group rather than as unrelated individuals who happened to cross the same terrain at different times. Later analysis by paleontologist Martin Lockley added a further detail: at Davenport Ranch, smaller trackways appeared to be positioned within or alongside the larger ones, a spatial pattern Lockley compared to modern elephant herds, in which younger animals often travel flanked or shielded by larger adults rather than scattered randomly through the group.

Parallel trackways moving in a consistent direction, at similar stride lengths and therefore similar implied speeds, remain the strongest physical evidence paleontologists have for gregarious, or group-living, behavior in specific dinosaur lineages, particularly among sauropods and some hadrosaurs. That said, this kind of evidence has an honest limitation: parallel trackways alone cannot fully rule out the possibility that multiple individuals independently chose the same easy, low-resistance path across a floodplain or along a shoreline, arriving at different times but leaving trails that look coordinated in hindsight. What strengthens the herding interpretation at sites like Davenport Ranch is the combination of consistent direction, consistent spacing between trackways, and the size-graded pattern Lockley described, three independent lines of evidence pointing the same way rather than one ambiguous signal.

At Davenport Ranch in Texas, paleontologist Roland T. Bird documented 23 separate sauropod trackways all moving in the same direction across a single surface, one of the earliest and most-cited physical evidence sets for herd movement in any dinosaur group.

The Lark Quarry reinterpretation, and why trackway science self-corrects

Lark Quarry in Queensland, Australia, has long been cited as the best physical evidence of a dinosaur stampede, with more than 3,300 footprints from small, mostly bipedal dinosaurs recorded moving in a single direction, historically interpreted as a panicked reaction to a large predator whose tracks cross the same surface. That original interpretation, developed and published in the 1970s and 1980s, made the site one of the most frequently cited pieces of dinosaur behavioral evidence anywhere in the world.

More recent work has substantially revised that story. A 2013 study by University of Queensland researchers Anthony Romilio and Steven Salisbury used detailed 3D laser and photogrammetric scanning of the tracksite and concluded the larger trackway long attributed to a stalking predator was more likely made by a plant-eating ornithopod, not a carnivorous theropod, and that it was laid down before, not during, the movement of the smaller animals. Follow-up analysis has gone further, proposing the smaller trackways may reflect animals swimming or wading across a river channel rather than fleeing in a panicked run across open ground, with some of the "footprints" possibly representing claw-drag marks left by buoyant animals whose feet only occasionally touched the bottom.

This reinterpretation is a useful case study in how trace fossil evidence works, and where it can go wrong. A trackway records physical contact between a foot and a surface, but it does not record intent, emotion, or context on its own, those have to be inferred from patterns like direction, spacing, depth consistency, and how the tracks relate to other trackways and sedimentary layers on the same surface. The original "stampede" reading was a reasonable interpretation of the visible pattern at the time, but it relied on assumptions about which trackway came first and what the larger tracks represented, assumptions that better imaging technology was eventually able to test and revise. Lark Quarry was designated Dinosaur Stampede National Monument by the Australian government under its original interpretation, and while the "stampede" name has stuck as a place name, the scientific literature since 2013 treats the underlying story with considerably more caution than the name implies.

Does the Lark Quarry reinterpretation mean the site is no longer scientifically important?

No, it means the opposite. The site remains one of the densest, best-documented dinosaur trackway surfaces in the world regardless of which specific behavioral story explains it, and the fact that new imaging technology was able to revise the original interpretation demonstrates the field actively testing and correcting itself rather than treating early conclusions as fixed. Both the original stampede hypothesis and the 2013 reinterpretation were published through peer review, which is how ichnology, like any observational science, is supposed to work.

Why trace fossils complement bone evidence, they don't replace it

Footprints have a well-documented blind spot: they usually cannot identify the exact species that made them with full certainty. Foot anatomy tends to be conserved across related dinosaur groups, meaning several different theropod species, for example, could plausibly produce very similar three-toed tracks, especially once substrate variation is factored in. This is precisely why ichnotaxa exist as a separate classification system rather than every trackway simply being assigned to whichever body-fossil species seems most likely, an assignment that would often be an educated guess dressed up as a fact.

The most reliable species-to-track matches come from rare cases where a trackway is found in direct stratigraphic association with body fossils of a specific animal, or in even rarer cases, where a trackway appears to end at or begin near a skeleton, though even these situations require careful interpretation rather than automatic assumption. Absent that kind of direct association, ichnologists describe trackways using anatomical features of the print itself, toe count, claw marks, relative digit proportions, and heel pad shape, and assign them to an ichnogenus and ichnospecies that describes the track, not necessarily a single known dinosaur genus.

This is also why trace fossils and body fossils genuinely need each other rather than one making the other redundant. A skeleton establishes what an animal's foot, hip, and leg anatomy allowed it to do in principle. A trackway shows what a population of animals actually did with that anatomy on a given day, whether they walked, ran, waded, or traveled in a coordinated group. Combining both evidence types, as researchers do when comparing footprint proportions against known skeletal foot anatomy from the same rock formation and time period, produces a far more complete picture than either fossil type could deliver alone. For readers curious about how the fossil record more broadly gets pieced together into a timeline, it helps to also understand how paleontologists date dinosaur fossils, since a trackway's behavioral story only means something once researchers know roughly when in the Mesozoic it happened. Diet evidence, covered in how we know what dinosaurs ate, works through a similarly indirect chain of physical clues, stomach contents, tooth wear, and coprolites standing in for direct observation the same way footprints stand in for direct observation of movement. And just as footprints are rare because they depend on a fragile, multi-step preservation process, dinosaur eggs are rare fossils for closely related reasons involving fragile original material and a narrow preservation window.

What paleontologists still can't tell from a trackway

It is worth being explicit about the limits of this kind of evidence, since trackway interpretations are sometimes reported with more confidence than the underlying data supports. Speed estimates from Alexander's formula carry a real margin of error because hip height has to be approximated from footprint size rather than measured directly, and different researchers applying slightly different hip-height multipliers to the same trackway can produce noticeably different speed ranges. Herding interpretations from parallel trackways are strong when supported by multiple independent lines of evidence, consistent direction, consistent spacing, and size-graded positioning, as at Davenport Ranch, but weaker when based on parallel direction alone, since animals independently following the same easy terrain can produce a superficially similar pattern.

Species identification from footprints alone remains the single biggest limitation, and the Lark Quarry case shows how even well-studied, frequently cited trackway sites can have their basic behavioral story revised once better imaging technology becomes available. None of this makes trackway evidence unreliable, every observational science, from astronomy to genetics, revises specific conclusions as tools improve while keeping its overall methods intact. It does mean that a responsible reading of any single trackway story should include the honest caveat that a footprint records a physical event with a fair amount of certainty, while the specific behavioral narrative built around that footprint carries more uncertainty and is the part most likely to be revised by future research.

The takeaway

A dinosaur trackway captures something a skeleton never can: proof that a specific animal moved across a specific patch of ground on a specific day, whether walking, running, fleeing, or traveling alongside others of its kind. Sites like Davenport Ranch and the Paluxy River trackways in Texas, and Dinosaur Ridge in Colorado, remain some of paleontology's best physical evidence that reconstructing dinosaur behavior doesn't always start with a bone. At the same time, the Lark Quarry story is a useful reminder that trackway interpretations are hypotheses built on physical patterns, tested and sometimes overturned as better tools come along, not fixed facts frozen in the rock alongside the footprints themselves.

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Read next:

• How Paleontologists Date Dinosaur Fossils
• How We Know What Dinosaurs Ate
• Why Dinosaur Eggs Are Rare Fossils

FAQ

Q: What makes a dinosaur footprint a trace fossil instead of a body fossil?

A trace fossil, or ichnofossil, preserves evidence of an organism's activity, such as a footprint, burrow, or trackway, rather than the organism's actual body. Footprints form when an animal steps into sediment soft enough to hold an impression, which then has to be buried by additional sediment layers before erosion or another animal's passage destroys it.

Q: How do paleontologists estimate a dinosaur's speed from footprints?

They measure stride length directly from a trackway and estimate hip height from footprint size, commonly using roughly four times footprint length as an approximation, then apply a biomechanical formula developed by zoologist R. McNeill Alexander in a 1976 paper published in Nature. The result is reported as an estimated speed range rather than an exact figure, since the hip-height approximation introduces margin of error.

Q: What is the significance of the Lark Quarry trackway site in Australia?

Lark Quarry preserves more than 3,300 footprints from small dinosaurs on a single surface, originally interpreted in the 1970s and 1980s as evidence of a predator-triggered stampede. A 2013 University of Queensland study using 3D scanning revised that interpretation, concluding the larger tracks were more likely left by a plant-eating dinosaur before the smaller trackways formed, with later work proposing the smaller animals may have been wading or swimming rather than fleeing.

Q: Can footprints identify exactly which dinosaur species made them?

Rarely with full certainty. Many related dinosaur species can produce similarly shaped footprints, particularly among closely related theropods, so trace fossils are classified using a separate naming system called ichnotaxa rather than being directly assigned to a specific dinosaur genus, unless a trackway is found in direct association with body fossils of a known species.

Q: What evidence do trackways provide for dinosaur herding behavior?

The strongest documented evidence comes from sites with multiple parallel trackways moving in the same direction at consistent spacing, such as the Davenport Ranch site in Texas, where paleontologist Roland T. Bird documented 23 sauropod trackways moving together. Researcher Martin Lockley later noted a size-graded pattern at the same site, with smaller trackways positioned alongside larger ones, a spatial arrangement he compared to how young elephants travel within modern herds.

Q: Why is footprint depth useful information beyond just showing the shape of a foot?

Footprint depth and the way sediment displaced around a print's edges indicate how firm, waterlogged, or dry the ground was at the moment an animal walked across it. This substrate information can also explain why footprints from the same species look different across a single site, since ground conditions, not anatomy, often account for the variation.