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Afossil track orichnite (Greek "ιχνιον" (ichnion) – a track, trace or footstep) is a fossilizedfootprint. This is a type oftrace fossil. Afossil trackway is a sequence of fossil tracks left by a single organism. Over the years, many ichnites have been found, around the world, giving important clues about the behaviour (and foot structure and stride) of the animals that made them. For instance, multiple ichnites of a single species, close together, suggest 'herd' or 'pack' behaviour of that species.
Combinations of footprints of different species provide clues about the interactions of those species. Even a set of footprints of a single animal gives important clues, as to whether it wasbipedal orquadrupedal. In this way, it has been suggested that somepterosaurs, when on the ground, used their forelimbs in an unexpected quadrupedal action.
Special conditions are required, in order to preserve a footprint made in soft ground (such as analluvial plain or a formativesedimentary deposit). A possible scenario is a sea or lake shore that became dried out to a firm mud in hot, dry conditions, received the footprints (because it would only have been partially hardened and the animal would have been heavy) and then became silted over in a flash storm.
The first ichnite found was in 1800 in Massachusetts, US, by a farmer named Pliny Moody, who found 1-foot (31 cm) long fossilized footprints. They were thought by Harvard and Yale scholars to be from "Noah's Raven".[1]
A famous group of ichnites was found in a limestone quarry atArdley, 20 km Northeast ofOxford,England, in 1997. They were thought to have been made byMegalosaurus and possiblyCetiosaurus. There are replicas of some of these footprints, set across the lawn ofOxford University Museum of Natural History (OUMNH).
A creature namedCheirotherium was, for a long time and still may be, only known from its fossilized trail. Its footprints were first found in 1834, inThuringia,Germany, dating from the LateTriassicPeriod.
The largest known dinosaur footprints, belonging tosauropods and dating from the earlyCretaceous were found to the north ofBroome on theDampier Peninsula,Western Australia, with some footprints measuring 1.7 m.[2][3] The 3D digital documentation of tracks has the benefit of being able to examine ichnite in detail remotely and distribute the data to colleagues and other interested personnel.[4]
Many fossil trackways were made bydinosaurs, earlytetrapods, and otherquadrupeds andbipeds on land. Marine organisms also made many ancient trackways (such as the trails oftrilobites andeurypterids likeHibbertopterus).
Some basic fossil trackway types:
The majority of fossil trackways arefoot impressions on land, or subsurface water, but other types of creatures will leave distinctive impressions. Examples of creatures supported, or partially supported, in awater environment are known. The fossil "millipede-type" genusArthropleura left its multi-legged/feet trackways on land.
Some of the earliest trackways for human ancestors have been discovered inTanzania.[6] TheLaetoli trackway is famous for thehominin footprints preserved involcanic ash. After the footprints were made in powdery ash, soft rain cemented the ash layer intotuff, preserving the prints.[6] The hominid prints were produced by three individuals, one walking in the footprints of the other, making the original tracks difficult to discover. As the tracks lead in the same direction, they might have been produced by a group – but there is nothing else to support the common reconstruction of a nuclear family visiting the waterhole together.
InSouth Africa, two ancient trackways have been found containing footprints, one at Langebaan and one at Nahoon. Both trackways occur in calcareous eolianites or hardened sand dunes. At Nahoon, trackways of at least five species of vertebrates, including three hominid footprints, are preserved as casts.[7] The prints atLangebaan are the oldest human footprints, dated to approximately 117,000 years old.[8]
Twenty six human fossil trackways have been found in the Willandra Lakes area adjacent to Lake Garnpung, consisting of 563 human footprints from 19,000 to 20,000 years ago.[9]
The earliest land creatures (actually land-marine coastal-riverine-marshland) left some of the first terrestrial trackways. They range from tetrapods to proto-reptilians and others.
A possible first connection of a trackway with the vertebrate that left it was published by Drs. Sebastian Voigt and David Berman and Amy Henrici in the 12 September 2007 issue ofJournal of Vertebrate Paleontology. The paleontologists who made the connection were aided by unusually detailed trackways left in fine-grainedLower Permian mud of the Tambach Formation in central Germany, together with exceptionally complete fossilised skeletons in the same 290-million-year-old strata. They matched the two most common trackways with the two most common fossils, two reptile-like herbivores known asDiadectes absitus (with the trackway pseudonymIchniotherium cottae) andOrobates pabsti (with the trackway pseudonym ofOrobates pabsti).[10]
The Permo-Carboniferous ofPrince Edward Island, Canada contains trackways of tetrapods and stem-reptiles.[11] Macrofloral andpalynological information help date them.
Ireland hosts late MiddleDevonian tetrapod trackways at three sites onValentia Island within the Valentia Slate Formation.[12][13]
The earliest fossil trackway of primitive tetrapods in Australia occurs in theGenoa River Gorge, Victoria, dating from theDevonian 350 million years ago.[14]
Dinosaurs lived on the continents beforegrasses evolved (the "Age of the Grasses" evolved with the "Age of the Mammals"); the dinosaurs lived in theTriassic,Jurassic, andCretaceous and left many trackways, both from plant-eaters and the meat-eaters, in various layers of mud and sand.
With scientific analysis, dinosaur specialists are now analyzing tracks for thewalking-speeds, orsprint-running speeds for all categories of dinosaurs, even to the large plant eaters, but especially the faster 3-toed meat hunters.Evidence ofherding, as well aspack hunting are also being investigated.
In north-central Namibia there is a dinosaur trackway in sandstone on what is now the private farmOtjihaenamparero. Larger footprints are of aceratosauria and smaller ones ofsyntarsus. The prints are believed to be around 190 million years old.[15][16]
In the Lower Zimbabwe Rift Valley there is a trackway in 140 Ma rose-colouredsandstone of Chewore Area. The small footprint size, with bothmanus andpes, implies that it is a trackway of a juvenile, a probablecarnosaur.[17]
The western regions of North America, especially the western border of theWestern Interior Seaway, are common for dinosaur trackways.Wyoming has dinosaur trackways from the Late Cretaceous, 65 ma.[18] (A model example of this 3-toed Wyoming trackway was made for presentation.)[19]
In theUnited States,dinosaur footprints and trackways are found in theGlen Rose Formation, the most famous of these being thePaluxy River site inDinosaur Valley State Park. These were the firstsauropoda footprints scientifically documented, and were designated a USNational Natural Landmark in 1969. Some are as large as about 3 feet across. The prints are thought to have been preserved originally in atidal flat or alagoon.[20] There are tracks from two types of dinosaur. The first type of tracks are from asauropod and were made by an animal of 30 to 50 feet in length, perhaps abrachiosaurid such asPleurocoelus,[20] and the second tracks by atheropoda, an animal of 20 to 30 feet in length, perhaps anAcrocanthosaurus. A variety of scenarios was proposed to explain the tracks, but most likely represent twelve sauropods "probably as a herd, followed somewhat later by three theropods that may or may not have been stalking – but that certainly were not attacking."[20]
Other examples include:
The Gansu dinosaur trackway located in the Liujiazia National Dinosaur Geopark in Yanguoxia, China contains hundreds of tracks including 245 dinosaur, 350 theropod, 364 sauropod and 628 ornithopod tracks among others.[22]
ThePhu Pha Man National Park inThailand contains one of the oldest dinosaur tracks to have been discovered inAsia.[23] Discovered in January 2024, paleontologists from theDepartment of Mineral Resources have dated the tracks to around 225–220 million years old (the late Triassic period).[24] The track contains traces of a variety of dinosaurs including theropods, sauropods, and archosaurs.[25]
TheLark Quarry Trackway inQueensland contains three-toed tracks made by a herd ofornithopod dinosaurs crossing a river. It was once believed they respresented a large predator chasing a mixed flock of small ornithopods and theropods, but this was contested in 2011.[26]
In aBathonianlimestone quarry site atArdley, Oxfordshire more than 40 sets of footprints, with some trackways reaching up to 180 metres in length, were discovered in 1997. These prints are largely only preserved in replicas and photographic records due to quarrying and subsequent restoration.Theropod tracks have been tentatively assigned to theichnogenusMegalosauripus, possibly fromMegalosaurus. The sauropod tracks could be grouped intowide-gauge trackways, associated with earlytitanosauria orbrachiosauridae, andnarrow-gauge ones, possibly from Cetiosaurus or a basaldiplodocoid.[27]In 2024 at nearby Dewars Farm Quarry,[28] five new extensiveMiddle Jurassic trackways dating back about 166 Ma were discovered, with evidence of more in the neighbourhood. The longest continuous trackway measured more than 150 metres. Four of the trackways were made by largesauropods, most likely againCetiosaurus. The fifth one was identified as made by the carnivoroustheropodMegalosaurus, based on its distinctive three-toed feet with claws. One area of the site shows the carnivore and herbivore tracks crossing over, suggesting the predator followed up on the steps of the sauropod.[29][30]
Mammal trackways are among the least common trackways. Mammals were not often in mud, or riverine environments; they were more often in forestlands or grasslands. Thus the earlier tetrapods or proto-tetrapods would yield the most fossil trackways. TheWalchia forest ofBrule, Nova Scotia has an example of anin situ Walchia forest, and tetrapod trackways that extended over some period of time through the forest area.
A recentmarsupial trackway site in the Colac district of Australia (west of Colac) contains marsupial trackways as well as kangaroo and wallaby tracks.[33]
Dinosaur trackways:
Early Tetrapods:
Australia
