The 20th century in ichnology refers to advances made between the years
1900 and
1999 in the scientific study of
trace fossils, the
preserved record of the behavior and
physiological processes of ancient life forms, especially
fossil footprints. Significant fossil trackway discoveries began almost immediately after the start of the 20th century with the 1900 discovery at
Ipolytarnoc, Hungary of a wide variety of
bird and
mammal footprints left behind during the early
Miocene.[1] Not long after, fossil Iguanodon footprints were discovered in
Sussex, England, a discovery that probably served as the inspiration for
Sir Arthur Conan Doyle's The Lost World.[2]
Several enduring mysteries from the
19th century continued to vex ichnologists, like the identity of the Chirotherium trackmaker. Renowned paleontologist
Franz von Nopcsa attributed the
ichnogenus to the
prosauropoddinosaurPlateosaurus, despite an apparent mismatch between its number of toes (4) and the preserved digit traces of Chirotherium (5). Von Nopcsa explained the discrepancy by arguing that one of the impressions in the Chirotherium tracks was left by a soft tissue structure that did not fossilize.[3] However, it was
Wolfgang Soergel who correctly hypothesized that Chirotherium was produced by a
distant relative of modern
crocodilians. Using only its footprints as a guide he reconstructed the life appearance of the Chirotherium trackmaker. Decades later paleontologists described an animal named Ticinosuchus which precisely fulfilled Soergel's predictions. Ticinosuchus or a close relative seems to have been the true Chirotherium trackmaker.[4]
During the 20th century, many significant fossil trackway discoveries were made
in the western United States. In the
1930s and
1940s,
Roland T. Bird discovered the tracks of large
sauropod and
theropod dinosaurs
in Texas. He excavated a major section of the track ways on behalf of the
American Museum of Natural History. This was the first large scale excavation of fossil footprints in history.[5] In the
1950sLee Stokes reported unusual footprints he interpreted as the first known
pterosaur tracks.[6] This attribution would be controversial much of the rest of the century but has since been vindicated.[7] The dinosaur footprints of
Dinosaur Ridgein Colorado were also discovered and studied in the 20th century.[8]
The advent of the
dinosaur renaissance and the publication by
R. McNeil Alexander of a formula which could reconstruct their running speed based on data from fossil trackways brought renewed interest and prestige to ichnology during the late 20th century.[9] This led to several
symposia on the subject of vertebrate trace fossils. In
1986 such a conference dedicated to dinosaur footprints was held
in New Mexico.[10] Roughly a decade later renowned German ichnologist
Heinrich Haubold organized a conference dedicated to the more ancient footprints of the
Paleozoic Era. This gathering has been regarded as a turning point in the study of tracks of that age.[11]
Luis Dollo matched the foot of Iguanodon bernissartensis with a purported Iguanodon footprint in "the first attempt to match these tracks with a particular species of the genus".[16]
Harold Broderick described the three-toed Middle Jurassic dinosaur footprints that had first been discovered during the 1890s at England's Yorkshire coast.[19]
90 million year old Cretaceous dinosaur footprints were discovered in New Jersey but were accidentally destroyed during an attempt at excavating them.[12]
Barnum Brown discovered the Centrosaurus apertus specimen AMNH 5351. Randy Moore has described the skeleton as the most complete Brown ever discovered.[22]
Charles Whitney Gilmore began collecting and studying the Carboniferous and Permian-aged footprint fossils of the Grand Canyon area on behalf of the
Smithsonian. He also constructed an outdoor exhibit about the tracks at
Hermit Trail.[23]
Renovations to
Oak Hill, the historical home of
US PresidentJames Monroe, led to the discovery of fossil dinosaur footprints when workers repaved the properties walkways with
Lower Jurassic stone. The preserved tracks included Grallator and Eubrontes prints ranging in length from 13 to 33 cm (5 to 13 in).[12] Other local footprints included the tracks of a crocodilian-like animal, Batrachopus. The tracks originated in the
Midland Formation.[27]
Baron Franz von Nopsca published a "seminal" work on fossil amphibian and reptile tracks.[3] He hypothesized that Plateosaurus was the Chirotherium trackmaker. Although Plateosaurus has only four hind toes and Chirotherium tracks have five impressions, Nopsca followed
Willruth's argument that the "thumb" of Chirotherium was composed only of
soft tissue and would have left no skeletal record.[28] He also named the large Late Jurassic theropod fossils discovered at Cabo Mondego, Portugal Eutynichnium lusitanicum. However, this name lacks validity because Nopsca did not formally describe it or designate a
type specimen.~154~
Wolfgang Soergel interpreted the Chirotherium trackmaker as a
pseudosuchian related to, but much larger than, Euparkeria.[28] He noted that the bulk of the animal's weight was born by its hindlimbs.[30]
German geologist
Adolf Bachofen-Echt reported the first scientifically recognized dinosaur tracks from
Croatia. These three-toed tracks were preserved on the
Brioni Islands and
Bachofen-Echt thought they were made by Iguanodon.~218~
Charles Gilmore described the Paleocene amphibian tracks from the Fort Union Formation of Montana. He named the new ichnospecies Ammobatrachus montanensis for the tracks. He observed that these were the first Paleocene fossil footprints to be documented in the scientific literature.[18]
Potential Paleocene mammal footprints were reported from
Alberta.[18]
Teilhard de Chardin and C. C. Young reported the discovery of dinosaur footprints in Shanxi Province, China. These were the first scientifically documented dinosaur footprints in the country's history.[33]
Bradford Willard discovered a new ichnogenus
Devonian-aged trace fossils in Pennsylvania that he named Paramphibius because he thought the trackmaker was a transitional form between
fishes and
tetrapods. He named a new taxon, the
Ichthyopoda to classify this creature.[34]
Roland T. Bird discovered a new Early Jurassic dinosaur tracksite in the
Moenave Formation of northwestern
Arizona. Although the site's location would be lost, Bird's photographs would help
Dinosaur National Monument paleontologist Scott Madsen, and friend Keith Becker, relocate the site decades later.[37]
Late: An expansion of the Nevada State Prison was built over the Pleistocene fossil footprints that had been discovered there. However, some specimens had been collected before and are now curated by the
Nevada State Museum.[39]
Maurice Mehl erected the new ichnogenus Ignotornis for some bird tracks preserved in the Dakota Group near
Golden, Colorado. These were the first scientifically documented
Mesozoic bird footprints.[40] The bird in question as interpreted as a "small
shorebird or
wader".[41] The site would eventually be heavily collected and all of its tracks were presumed removed.[40]
Edward Branson and Maurice Mehl named a new kind of Late Triassic dinosaur footprint discovered in the
Popo Agie Formation of western Wyoming. The new ichnogenus and species was named Agialopus wyomingensis.[43]
The
Dinosaur Ridge dinosaur tracksite was discovered near
Denver, Colorado. Tracks include those made by ornithopods and theropods. Some of the ornithopod tracks seem to have been left by individuals traveling together and are thus evidence for social behavior.[47] Further, these ornithopods seem to have traveled predominantly on all fours, unlike most ornithopod tracks, which were made by bipeds.[48]
The New York Times reported that
Barnum Brown had discovered the fossil footprints of a huge and unknown kind of dinosaur in a Wyoming coal mine. Brown's claim was simply a "publicity stunt" aimed at attracting funding.[49] However, Brown's report attracted the attention of a coal mine operator from the
Cedaredge, Colorado area named Charlie States, who reported large dinosaur footprints spaced five meters apart in his mine, the Red Mountain Mine.[50] Brown and his assistant Roland Bird oversaw an "ambitious" excavation of the purported giant's tracks. After three weeks of 24-hour labor on the part of the miners and the development of specialized equipment to extract the specimen, a 17-foot long slab of track-bearing rock was taken from the mine and shipped to the
American Museum of Natural History in
New York City.[51]
More Late Triassic dinosaur footprints were discovered near Gettysburg. These tracks ranged from chicken-sized to 15 cm (5.9 in) in length.[44]
Kenneth Caster conclusively demonstrated that unusual fossil tracks from the Solnhofen lithographic limestone variously attributed to creatures like Archaeopteryx, little dinosaurs, or pterosaurs were actually made by
horseshoe crabs, as specimens had been found literally "dead in their tracks".[52] Similar fossils in the United States had been attributed to a transitional form between fishes and tetrapods by Bradford Willard earlier in the 1930s.[34]
Brown published a description of the dinosaur tracks with the purported giant stride length. He tried to keep up his charade of there being an undiscovered mystery dinosaur by downplaying "the obvious
hadrosaurian affinity of the tracks".~???NA220-221~
Nash bought the Massachusetts property where he discovered dinosaur footprints. He would begin excavating and selling the dinosaur footprints on his land and the property would come to be known as
Nash Dinosaur Land.[45]
Lionel F. Brady began experimenting with living arthropods to help determine which sorts of arthropods may have produced various ancient trace fossils.[53]
Sumner Anderson reported the presence of small carnivorous dinosaur footprints between 15 and 20 cm in length preserved in the Early Cretaceous
Lakota Formation at two different sites in
South Dakota.[54]
Earl L. Poole of the
Public Museum and Art Gallery discovered a new Late Triassic dinosaur track site at a quarry near
Schwenksville, Pennsylvania.[44] The dozens of tracks preserved there were mostly left by
chicken-sized dinosaurs, but about a "half dozen" of them were left by turkey-sized trackmakers.[55] Poole ascribed these tracks to the ichnogenus Anchisauripus. One footprint was left by a dinosaur with about the same body mass as a
horse.[45] This site is now known as the
Squirrel Hill Quarry.[44]
1940s
Frank Peabody performed "extensive" research on Early Triassic fossil footprints.[56]
Roland T. Bird oversaw the excavation of sauropod and theropod tracks from the
Paluxy River in Texas. This was the first large-scale dinosaur track excavation in history.[57]
Frank Peabody studied the early
Pliocene fossil amphibian footprints of the
Sierra Nevada Mountains of
California. He found them to be almost identical to the tracks of their descendants. This was his first major contribution to ichnology.[58]
Robert Chaffee reported the presence of a tracksite from Wyoming preserving the footprints of a
camel-like
even-toed ungulate and a
rhinoceros-like odd-toed ungulate in the Oligocene-aged
White River Beds. He noted that only two other Oligocene fossil tracks were known and neither had been described.[62] Chaffee attributed one of these, a partial print preserved in the
Yale Peabody Museum, to a
brontothere.[63]
F. E. Peabody published a study of the amphibian and reptile tracks preserved in the Triassic Moenkopi Formation. Lockley and Hunt would later regard this paper as "a classic" in the field.[64]
1950s
A rock hound named Al Look "embellished" Barnum Brown's mystery dinosaur hoax, informally naming the creature "Xosaurus". He also reported having encountered another dinosaur trackway with a similarly long stride as Brown's original specimen. This trackway supposedly recorded the huge mystery dinosaur stepping on a crocodile-like reptile.[66]
Albert de Lapparent and others restudied the large Late Jurassic theropod tracks of Cabo Mondego.[24] They thought the tracks were made by Megalosaurus.[67]
Henry Faul and Wayne Roberts reported the presence of Early Jurassic fossil footprints in Colorado's
Navajo Sandstone. These tracks were probably left by an evolutionary precursor to mammals.[6]
Wilhelm Bock reinterpreted the footprints discovered in the Squirrel Hill Quarry as Grallator and non-dinosaurian
archosaur tracks. He also described the ichnospecies Anchisauripus gwynnedensis for a dinosaur track discovered in the
North Pennsylvania Railroad tunnel near
Gwynned. These tracks are now thought to belong to Atreipus, however.[45]
A French ichnologist named
Lessertisseur erected the ichnogenus Megalosauripus. He attributed the Cabo Mondego tracks to a
megalosaurid.[70] He also named the ichnogenus Tyrannosauripus, but as both ichnogenera lacked type species and type specimens these taxonomic names were invalid.[71]
M. F. Farmer published the locations of many track sites in northern Arizona.[72]
Lee Stokes erected the new ichnogenus Pteraichnus for fossil footprints discovered in the Morrison Formation of Utah that he thought were left by pterosaurs.[6]
Oskar Kuhn named the new Early Cretaceous theropod ichnogenus and species Buckeburgichnus maximus from Germany. It is notable in its preservation of a large
hallux impression.[74]
August 3rd:Albert de Lapparent and
Robert Lafitte stumbled on some fossil footprints left by a large bipedal dinosaur in the
Festningen Sandstone at
Isfjorden, Svalbard.[76] The researchers suspected that the tracks were made by a
carnosaur. At 78 degrees of latitude north, these were the highest latitude dinosaur tracks known in the world, up from the previous record of 56 degrees.[77]
A
geologist named
H. D. Curry working for the
Shell Oil Company discovered a slab of rock preserving high quality three-toed mammal footprints in Utah's
Strawberry Canyon. The trackmakers were probably Eocene relatives of modern
tapirs and
horses. Curry donated the so-called "Strawberry Slab" to the Smithsonian Institution.[78]
Albert de Lapparent reinterpreted the dinosaur tracks from Spitzbergen. Although mentioning their initial impression that the tracks were carnosaurian, he concluded that the tracks were probably left by Iguanodon instead, due to their lack of claw marks, rounded toe prints, and general similarity to the feet of Iguanodon bernissartensis.[77]
Panin and
Avram published research on
Miocene fossil bird and mammal tracks from the vicinity of the
Carpathian Mountains of
Romania. They attributed the local bird footprints to four different families, the
anatids,
ardeids,
charadriids, and
gruids. Contemporary mammalian trackmakers included
artiodactyls,
cats,
dogs, and
relatives of modern elephants. The latter of these left behind one thoroughly trampled site with an area of more than 100 sq m. The researchers erected several new ichnotaxa for the tracks they studied and similar tracks would later be discovered elsewhere in Europe.[79]
The first dinosaur footprints known from Israel were discovered.[80]
A large pseudosuchian named Tichinosuchus was named for remains found in Swiss Triassic rocks. It had the right size and anatomy to account for the Chirotherium tracks of Europe and is considered the most likely trackmaker.[82]
de Raaf,
Beets, and
Kortenbout van der Sluijs reported the presence of a large number of well-preserved web-footed bird tracks from
Oligocene rocks in Spain.[83] The high percentage of the fossil trails being oriented in the same direction suggests that this deposit records evidence for flocking in these ancient birds. This is extraordinary because evidence for social behavior in fossil bird footprints is very uncommon.[32]
March: A coal miner working near
Hayden, Colorado hit his head on the natural cast of a dinosaur footprint while in pursuit of a run-away coal cart. The impact injured his spinal cord, leading to his death 10 days later.[85]
1970s
Mid: Dinosaur tracks of the ichnogenera Atreipus and Grallator were discovered in a quarry that straddles the Virginia-
North Carolina border. These may be the oldest dinosaur tracks known in the eastern United States.[86]
Late: The publication of a formula capable of inferring the life speeds of dinosaurs from their fossil trackways brought further attention to Barnum Brown's claim of having discovered the tracks of a mystery dinosaur with an abnormally long stride length. Scientists instantly recognized the footprints as belonging to a duck-billed hadrosaur rather than some completely unknown dinosaur, but the validity of the trackway's stride length proved controversial.
Dale Russell and
Pierre Beland accepted Brown's measurement and calculated the trackmaker as moving at 27 kilometers an hour.
Tony Thulborn argued that a footprint left by another dinosaur obscured a track left by the original trackmaker roughly halfway between the prints composing the supposedly enormous stride. This implied that the trackmaker's stride was only half the claimed size and it was probably only traveling at about 8.5 kilometers an hour.[66]
Leonard Wills and
Bill Sarjeant reported potential dinosaur footprints from Triassic rocks in
Nottinghamshire and
Worcestershire. Ichnotaxa reported included Coelurosaurichnus, Otozoum, and Swinertonichnus. The rocks were of uncertain age at the time of the authors writing and are now known to have been Lower Triassic.[87] Dinosaur tracks dating to the Early Triassic would be anomalous as their skeletal remains are not known until later in the period.[88] Not surprisingly, the dinosaurian status of the tracks reported by Wills and Sarjeant have been disputed.[87]
Haubold formally named the German ichnospecies Metatetrapous valdensis from Germany's Wealden Beds. The discovery may represent fossil
ankylosaur footprints.[89]
de Clercq and Holst published on the Upper Oligocene bird tracks of
Lucerne, Switzerland. The researchers attributed the tracks to
rails.[90]
Vialov classified fossil bird footprints as members of the ichno order Avipedia.[93]
David Webb studied the fossil footprints left by ancient camels and determined that even these ancient forms shared modern camels' "pacing gait", where the animal moves both legs on one side of the body at the same time, unlike most mammals which move hindlimbs and forelimbs from the opposite sides of the body in each step. Webb argued that the energetic efficiency of the pacing gait enabled camels' success in desert and prairie environments where significant distances may separate food and water sources.[94]
Paul Olsen and
Robert F. Salvia discovered dinosaur Late Triassic footprints in the
Stockton Formation of
Nyack Beach State Park, New York. The tracks included 12–15 cm (4.5–6 in) long Grallator tracks. Possible Atreipus tracks were also found there. The regions's non-dinosaurian tracks included Apatopus, Brachychirotherium, Chirotherium, and Rhynchosauroides.[95]
Justin Delair and
A. B. Lander reported the presence of three parallel dinosaur trackways in the Roach Stone of Herston, England.
A significant Permian-aged fossil tracksite in the
Cedar Mesa Sandstone of Utah was inundated following the creation of the
Glen Canyon Dam. This tracksite preserved an apparent predator-prey interaction wherein the trail left by a small amphibian or reptile vanished at the point where it intersected with the trail left by a large carnivorous proto-mammal. Fortunately for ichnologists, plaster casts of the trackways and photographs remain available for study.[96]
Kaever and de Lapparent named the new ichnogenus and species Elephanotpides barkhausensis for the poorly preserved tracks of a large quadrupedal dinosaur discovered near Barkhausen, Germany. The trackmaker was probably a sauropod.[97]
Heinberg describes
Ancorichnus, a non-marine burrowing animal.[98]
Bill Sarjeant described the five-toed Middle Jurassic footprints discovered by C. Pooley and named it Pooleyichnus burfordensis in his honor.[100] Sarjeant proposed that this unusual track may have been made by a mammal.[101]
A large tracksite preserved in the late Eocene
Vieja Group of Texas was first studied in a
University of Texas research program.
Robert E. Weems was informed of, and began researching, a Late Triassic reptile track site in a quarry near
Culpeper, Virginia.[102]
Leon Pales described the Pleistocene human footprints of France's Niaux cave complex. This paper has been considered "one of the most comprehensive studies of cave footprints ever published."[17]
R. McNeil Alexander published a formula for inferring the speeds of dinosaurs from their fossil trackways.[72]
Russell and Beland examined Brown's claim to have discovered the tracks of a running dinosaur.[104]
Several hundred Late Triassic dinosaur footprints were reported from the vicinity of Cardiff, Wales.[105] This report was made by
M. E. Tucker and
T. P. Burchette.[106]
Marc Edwards and others reported the dinosaur footprints discovered in Spitzbergen in 1978. Only two footprints were discovered at the site, which was an exposure of the Helvetiafjellet Formation. The researchers interpreted the tracks as carnosaur footprints, but now they are thought to have been left by
iguanodontids.[108]
Stokes observed that tracks left by close evolutionary relatives of mammals were common and widespread in the Navajo Sandstone. He found such tracksites in Colorado,
Idaho, and Utah.[109] He reported many new sites in the Navajo formation.[92]
Ismael Ferrusquia-Villafranca and others reported the discovery of the first dinosaurs tracks to be scientifically documented in Mexico.[110]
Carme Lompart reported the presence of Late Cretaceous dinosaur tracks in the
Ager Valley of Spain, near the country's border with France.[112]
Marc Weidmann and
Manfred Reichel published a "lengthy" review of the Oligocene to Miocene aged bird tracks found in Switzerland's "Molasse" rock.[90] They reported the presence of tracks left by one kind of
duck, two kinds of
herons, one kind of
perching bird, and four kinds of
waders.[113] Weidmann and Reichel devoted intense effort to classifying these tracks based on previous schemes devised by scholars like Avram, Panin, and Vialov for other bird track sites.[93] They also worked diligently to discern the tracks' positions within the stratigraphic column.[114]
A nine meter long Pleistocene
bear trackway was reported from
Lake County, Oregon. The tracks themselves were about 40 cm long, suggesting a trackmaker roughly the size of a large modern bear. These tracks may have been left by an Arctotherium.[117]
Olsen argued that the ichnogenera Grallator, Anchisauripus, and Eubrontes actually represent a growth series.[69]
Walter P. Coombs, Jr. interpreted some unusual Eubrontes tracks from Dinosaur State Park of
Rocky Hill, Connecticut as traces left by a swimming theropod because the tracks only preserved impressions from the tips of the animal's toes as if the rest of its body weight was supported by water.[118]
Demathieu and Haubold described the new Early Triassic ichnogenus and species Isochirotherium archaem from Germany. As only the hind prints are preserved in this trackway it may represent the oldest evidence in the world for the existence of animals with bipedal gaits. However, while intriguing, their remains the possibility that the track maker was a quadruped and its foreprints eroded away before the trail was discovered.[121]
Demathieu and
Marc Weidmann described a new Triassic fossil tracksite from Switzerland called the
Vieux Emosson tracksite.[122]
Geology student Jeff Pittman recognized that the "potholes" hindering excavation equipment traffic through a gypsum mine in southeastern Arkansas were actually sauropod dinosaur footprint.[123]
Hartmut Haubold published the
Saurierfahrten.[124] Haubold was a German ichnologist, and the Saurierfahrten a specialist's handbook for identifying Carboniferous and Permian fossil footprints. It was the only publication of its type in the world at the time and only available in German.[125]
Paul Olsen and
Peter Galton argued that Ellenberger had oversplit the Late Triassic and Early Jurassic ichnotaxa he studied and that many of the kinds of tracks he regarded as distinct were the tracks previously described in eastern North America.[126]
J. E. Andrews and J. D. Hudson reported the first dinosaur tracks to be scientifically documented in Scotland. The tracks are three-toed and preserved in the Middle Jurassic
Leate Shale.~144~
George Demathieu and others described an Oligocene bird and mammal track site from southeastern France. Three different mammalian ichnotaxa were present. One was an artiodactyl track they named Bifidipes velox. The second was the largest of the three, Ronzotherichnus, was apparently left by the rhinoceros Ronzotherium. A
creodont or early carnivoran left behind the third kind of tracks, which the researchers named Sarcotherichnus enigmaticus. They named the bird tracks at the site Pulchravipes magnificus.[84]
Kevin Padian and Paul Olsen reinterpreted the supposed pterosaur tracks named Pteraichnus from the Morrison Formation of Utah as crocodilian tracks.[120]
Luis Aguirrezabala reported the presence of nine parallel trails left by Hypsilophodon or one of its close relatives in Lower Cretaceous rocks of
La Rioja, Spain. This tracksite is now known as the Valdevajes site.[127]
An international symposium for paleontologists performing research on "Dinosaur Tracks and Traces" was held in New Mexico.[128] The gathering was a success and "led to the rejuvenation and maturing of the discipline of dinosaur ichnology".[129]
Paul Ensom reported dinosaur tracks from the Purbeck Limestone of Dorset, England.[131]
Lockley disputed
Robert T. Bakker's hypothesis that an Early Cretaceous sauropod trackway from the Davenport Ranch, Texas area preserves evidence that sauropods traveled in herds with the young surrounded by the adults to protect them from predators. Instead, Lockley interpreted this trackway as a herd of sauropods traveling through a narrow area, with the young following the adults.[132]
Lockley and Hunt began studying the dinosaur tracks of the Dakota Group at the
Alameda Parkway site, which is now called
Dinosaur Ridge.[133]
Lockley described the ichnogenus Caririchnium. This publication was also the first detailed treatment of the Dakota Group's trace fossil record in the scientific literature.[134]
Robert E. Weems published the results of his research into the Late Triassic reptile tracksite near
Culpeper, Virginia. Among the fossil footprints he found there were the dinosaur ichnogenera Agrestipus, Grallator, Gregaripus, and Kayentapus.[102]
Harald von Walter and
Ralf Werneberg reported the discovery of body impressions left behind by
diplocaulid amphibians in the Rotliegende of the Thuringian Forest area. The assemblage includes the body impression of several individuals, all no more than a few centimeters in length.~46~ The authors named these traces Hermundurichnus fornicatus.[135]
Lockley and Hunt rediscovered fossil bird footprints in the Dakota Group near Golden Colorado.[136] Among the specimens recovered was the first in the world to preserve dinosaur and bird footprints together.[137]
Lockley reported the first observation in the Dakota Group of dinosaur footprints with preserved skin impressions.[134]
W. A. S Sargeant and
J. A. Wilson reported the presence of Eocene mammal footprints in Texas.[138]
R. Santamaria,
G. Lopez, and
M. L. Casanovas-Cladellas reported an Oligocene mammal track site discovered near
Agramunt, Spain. This tracksite preserved four new ichnospecies, three of which were in new ichnogenera. First was a new species of Bothriodontipus, which was made by the pig-like animal Bothriodon or a close relative. The researchers new ichnogenera were Creodontipus and Plagiolophustipus.[84] They classified two of their new ichnospecies in Creodontipus, an ichnogenus they fittingly attributed to creodonts. They attributed Plagiolophustipus to tapir-like animals distantly related to horses.[139]
Jeff Pittman proved that the sauropod tracks he recognized in an Arkansas
gypsum mine were actually at the same level of the geologic column as the Glen Rose Formation sauropod tracks of Texas.[140]
Farlow, Pittman, and Hawthorne described the ichnogenus Brontopodus.[60]
April: A quarry worker named Robert Clore blasting stone near Culpeper, Virginia uncovered a new Late Triassic reptile tracksite.[141] Weems began studying the site that same year, and reported the presence of 4,000 individual tracks. The local tracks included the dinosaur ichnogenera Grallator and Kayentapus. Other tracks may have been left by
aetosaurs.[142]
Ryszard Fuglewicz and others reported fossil trackways from the
Holy Cross Mountains of
Poland that may be the oldest Triassic trackways in Europe. They reported tracksites at six different positions within a stratigraphic series in several distinct paleoenvironments including river channels and floodplains. The ichnogenera they identified in these tracksites included Brachychirotherium, Capitosauroides, Isochirotherium, Rhynchosauroides, and Synaptichnium.[143]
C. Lancis and
A. Estevez reported the presence of early Pliocene tracks preserved near
Alicante, Spain. Among the mammals who left their mark here were members of the horse family and bears.[148]
Farlow observed that sauropod trackways could be categorized as either being "narrow-gauge" or "wide-gauge".[149]
Mid November: Lockley and Hunt's research group at the University of Colorado undertook one of the few major dinosaur footprint excavations in history in order to expand the exposed track-bearing surface at Dinosaur Ridge for an outdoor interpretive center.[150]
Lockley and dos Santos described the
Kimmeridgian-aged
Avelino quarry tracksite near
Lisbon, Portugal, the first scientifically documented sauropod dinosaur tracksite in Europe to contain well-preserved tracks of the animals' front feet. All of the trackmakers seem to have been juveniles.[153]
Meyer reported the first scientifically documented Late Jurassic dinosaur footprints from Switzerland. These tracks were discovered near the town of
Lommiswil.[154]
Claude Guerin and George Demathieu described the new ichnospecies Dicerotichnus laetoliensis. This ichnospecies was left behind by a late Pliocene rhinoceros of fairly modern build, possibly from the genus Diceros. Its tracks are preserved at the same site known for its ancient
hominid tracks.[84]
A non-technical article in the Spanish magazine Blanco y Negro discussed the wide variety of Miocene tracks preserved at
Salinas de Anana, Spain.[155]
Lockley and Hunt introduced the idea of
ichnofacies to the scientific literature. They described and named the Brontopodus ichnofacies based on sauropod tracksites in Texas.~NA210~[citation needed]
A new tracksite was discovered in
Toadstool Park area of Nebraska's
Oglala National Grassland.[156] Eleven different trackmakers have been documented here, including camels, carnivorans, ducks, rhinoceroses, and shorebirds.[157]
Lockley and others argued that Deltapodus was probably not left by a sauropod because the hind prints had only three toes and the tracks themselves were preserved in an environment where sauropod tracks are not generally found.~135~ Instead they concluded it was more likely to be the tracks of a
thyreophoran, possibly a
stegosaur.[159]
A cave enthusiast near
Fatima, Portugal looked down on a quarry from a high ridge and noticed that its floor was covered in sauropod footprints.[160] The site included the longest known dinosaur trails at the time. The individual tracks are the largest sauropod prints known from the Middle Jurassic and include the largest foreprints of any known sauropod track type.[161]
Lockley, Hunt, and Meyer defined the Brontopodus ichnofacies.
Galopim published The Battle of Carenque, a book describing the successful efforts of Portuguese conservationists to save the home of the world's longest dinosaur trackway from being destroyed by freeway construction.[162]
Bill Sarjeant and Wann Langston published a monograph on the late Eocene track site from the Vieja Group of Texas. The tracks preserved there indicate a fauna including six kinds of bird, two kinds of invertebrate, nineteen mammal species, and two kinds of turtle.[164]
Hunt, Lockley, and Lucas reported the existence of a fossil trackway preserving an apparent act of predation of a
pelycosaur upon a small reptile.[29]
Lockley, Hunt, and Meyer proposed the idea of vertebrate
ichnofacies.[25]
Lockley and Hunt defined the Brontopodus and Caririchnium ichnofacies.[134]
Iwan Stossel reported the oldest known fossil vertebrate footprints in Europe to the scientific literature.[165] The tracks were preserved in the
Mid-
Late Devonian
Valentia Slate of
Valentia Island, which lies off the southwestern coast of
Ireland. Roughly 150 tracks were present in an 8 meter long trail left behind by an early tetrapod.[166]
David Scarboro and
Maurice Tucker reported the discovery of a fossil trail probably left by a
temnospondyl amphibian about 1.5 meters long walking through a delta during the Middle Carboniferous. The find is one of the largest Carboniferous fossil trackways in all of Europe.[167]
Jean-Michel Mazin and others described the first scientifically documented pterosaur fossils from Europe. These tracks were preserved in a Late Jurassic limestone in
Crayssac, France.[168] The pterosaurs that left these footprints seem to have been in the sparrow to sea gull size range. These tracks have played a "pivotal" role in confirming that various unusual and controversial trace fossils reported around the world really were made by pterosaurs after all.[169]
April: Fabio Dalla Vecchia and one of his students were arrested while mapping dinosaur footprints in Croatia and inadvertently following the tracks into a military zone. They were tried and subsequently fined their trial expenses and released.[170]
Koenigswald, Walders, and Sander described a 30,000- to 20,000-year-old Pleistocene fossil mammal track site from
Bottrop, Germany. Local trackmakers included
bison, horses,
cave lions,
reindeer, and wolves.[171]
Price argued that scholars generally underestimated how long ago humanity first domesticated horses based on a
Bronze Age tracksite in Sweden.[172]
Phylis Jackson argued that the pedal anatomy of
Anglo-Saxon and
Celtic peoples are so distinct that these populations can be distinguished based on feet alone going all the way back to the
Neolithic.[173] Celtic people have narrower feet while Anglo-Saxon feet are broader.[174]
Fuentes Vidarte reported the oldest known bird tracks in the world from the Berriasian Wealden Beds of the Villar del Rio, Spain.[145]
Fabio Dalla Vecchia returned to Croatia and finished mapping the dinosaur footprints with Croatian geologist
Igor Vlahovic.[175]
Fabio Dalla Vecchia and Marco Rustioni reported a Miocene mammal tracksite in the
Conglomerato di Osoppo in
Udine Province, Italy. Across its 100 square meter area the track site preserved the footprints of three different kinds of large mammal.[79]
The first international workshop on Paleozoic footprint fossils, presided over by Hartmut Haubold was held in Germany.[128] The symposium was such a success that it is regarded as a turning point in the history of Paleozoic vertebrate ichnology.[129]
Avanzini,
van den Dreissche and
Keppens concluded that the tracks preserved at Lavini de Marco in Italy were cemented through chemical processes trigger by the rapid evaporation of water from the carbonate track-bearing substrate and speculated that similar circumstances may have preserved tracks in carbonates at other sites and different positions in the stratigraphic column.[176]
Meyer reported that the Late Jurassic dinosaur tracks discovered near Lommiswil, Switzerland were actually part of a gigantic megatracksite. This was the first report of a dinosaur megatracksite in Europe.[177]
Wright and others re-examined the Purbeckopus pentadactylus tracks from Dorset, England and concluded that not only were they pterosaur tracks, but they were among the largest known pterosaur tracks in the fossil record.[81]
Tuner and Anton attributed Miocene cat footprints found at Salinas de Anana, Spain to the genus Pseudaelurus. These tracks may in fact be the oldest known cat footprints in the world.[155]
Phylis Jackson published further research on the use of pedal anatomy and footprints to distinguish different groups of people.[173]
Lockley, dos Santos, and Hunt found the purported hypsilophodont tracks of the Spanish Valdavajes tracksite similar to the Late Jurassic ichnogenus Dinehichnus that has been attributed to
dryosaurids.[127]
Lopez-Martinez and others noted the presence of sauropod and ornithopod tracks near the
K-T Boundary in the
Tremp Formation of northeastern Spain. The presence of tracks so close to the Cretaceous-Tertiary suggests that the dinosaur died out rapidly rather than gradually.[179]
^Lockley and Hunt (1995); "Parallel Trackways and Dinosaur Herds", pages 196–197 and "The Dinosaur Freeway", page 209.
^Lockley and Hunt (1995); For role of the dinosaur renaissance, see "Preface", page xvi. For paleontologists' need for data following the publication of Alexander's formula, see "The Case of the 'Mystery Dinosaur'", page 221.
Lockley, Martin G.; Hunt, Adrian (1995). Dinosaur Tracks and Other Fossil Footprints of the Western United States. Columbia University Press. p. 338.
ISBN978-0231079266.
Lockley, Martin G.; Meyer, C. A. (2000). Dinosaur Tracks and other fossil footprints of Europe. New York: Columbia University Press.
ISBN0-231-10710-2.
Moore, Randy (2014). Dinosaurs by the Decades: A Chronology of the Dinosaur in Science and Popular Culture. Santa Barbara: Greenwood. p. 472.
ISBN978-0-313-39364-8.
The 20th century in ichnology refers to advances made between the years
1900 and
1999 in the scientific study of
trace fossils, the
preserved record of the behavior and
physiological processes of ancient life forms, especially
fossil footprints. Significant fossil trackway discoveries began almost immediately after the start of the 20th century with the 1900 discovery at
Ipolytarnoc, Hungary of a wide variety of
bird and
mammal footprints left behind during the early
Miocene.[1] Not long after, fossil Iguanodon footprints were discovered in
Sussex, England, a discovery that probably served as the inspiration for
Sir Arthur Conan Doyle's The Lost World.[2]
Several enduring mysteries from the
19th century continued to vex ichnologists, like the identity of the Chirotherium trackmaker. Renowned paleontologist
Franz von Nopcsa attributed the
ichnogenus to the
prosauropoddinosaurPlateosaurus, despite an apparent mismatch between its number of toes (4) and the preserved digit traces of Chirotherium (5). Von Nopcsa explained the discrepancy by arguing that one of the impressions in the Chirotherium tracks was left by a soft tissue structure that did not fossilize.[3] However, it was
Wolfgang Soergel who correctly hypothesized that Chirotherium was produced by a
distant relative of modern
crocodilians. Using only its footprints as a guide he reconstructed the life appearance of the Chirotherium trackmaker. Decades later paleontologists described an animal named Ticinosuchus which precisely fulfilled Soergel's predictions. Ticinosuchus or a close relative seems to have been the true Chirotherium trackmaker.[4]
During the 20th century, many significant fossil trackway discoveries were made
in the western United States. In the
1930s and
1940s,
Roland T. Bird discovered the tracks of large
sauropod and
theropod dinosaurs
in Texas. He excavated a major section of the track ways on behalf of the
American Museum of Natural History. This was the first large scale excavation of fossil footprints in history.[5] In the
1950sLee Stokes reported unusual footprints he interpreted as the first known
pterosaur tracks.[6] This attribution would be controversial much of the rest of the century but has since been vindicated.[7] The dinosaur footprints of
Dinosaur Ridgein Colorado were also discovered and studied in the 20th century.[8]
The advent of the
dinosaur renaissance and the publication by
R. McNeil Alexander of a formula which could reconstruct their running speed based on data from fossil trackways brought renewed interest and prestige to ichnology during the late 20th century.[9] This led to several
symposia on the subject of vertebrate trace fossils. In
1986 such a conference dedicated to dinosaur footprints was held
in New Mexico.[10] Roughly a decade later renowned German ichnologist
Heinrich Haubold organized a conference dedicated to the more ancient footprints of the
Paleozoic Era. This gathering has been regarded as a turning point in the study of tracks of that age.[11]
Luis Dollo matched the foot of Iguanodon bernissartensis with a purported Iguanodon footprint in "the first attempt to match these tracks with a particular species of the genus".[16]
Harold Broderick described the three-toed Middle Jurassic dinosaur footprints that had first been discovered during the 1890s at England's Yorkshire coast.[19]
90 million year old Cretaceous dinosaur footprints were discovered in New Jersey but were accidentally destroyed during an attempt at excavating them.[12]
Barnum Brown discovered the Centrosaurus apertus specimen AMNH 5351. Randy Moore has described the skeleton as the most complete Brown ever discovered.[22]
Charles Whitney Gilmore began collecting and studying the Carboniferous and Permian-aged footprint fossils of the Grand Canyon area on behalf of the
Smithsonian. He also constructed an outdoor exhibit about the tracks at
Hermit Trail.[23]
Renovations to
Oak Hill, the historical home of
US PresidentJames Monroe, led to the discovery of fossil dinosaur footprints when workers repaved the properties walkways with
Lower Jurassic stone. The preserved tracks included Grallator and Eubrontes prints ranging in length from 13 to 33 cm (5 to 13 in).[12] Other local footprints included the tracks of a crocodilian-like animal, Batrachopus. The tracks originated in the
Midland Formation.[27]
Baron Franz von Nopsca published a "seminal" work on fossil amphibian and reptile tracks.[3] He hypothesized that Plateosaurus was the Chirotherium trackmaker. Although Plateosaurus has only four hind toes and Chirotherium tracks have five impressions, Nopsca followed
Willruth's argument that the "thumb" of Chirotherium was composed only of
soft tissue and would have left no skeletal record.[28] He also named the large Late Jurassic theropod fossils discovered at Cabo Mondego, Portugal Eutynichnium lusitanicum. However, this name lacks validity because Nopsca did not formally describe it or designate a
type specimen.~154~
Wolfgang Soergel interpreted the Chirotherium trackmaker as a
pseudosuchian related to, but much larger than, Euparkeria.[28] He noted that the bulk of the animal's weight was born by its hindlimbs.[30]
German geologist
Adolf Bachofen-Echt reported the first scientifically recognized dinosaur tracks from
Croatia. These three-toed tracks were preserved on the
Brioni Islands and
Bachofen-Echt thought they were made by Iguanodon.~218~
Charles Gilmore described the Paleocene amphibian tracks from the Fort Union Formation of Montana. He named the new ichnospecies Ammobatrachus montanensis for the tracks. He observed that these were the first Paleocene fossil footprints to be documented in the scientific literature.[18]
Potential Paleocene mammal footprints were reported from
Alberta.[18]
Teilhard de Chardin and C. C. Young reported the discovery of dinosaur footprints in Shanxi Province, China. These were the first scientifically documented dinosaur footprints in the country's history.[33]
Bradford Willard discovered a new ichnogenus
Devonian-aged trace fossils in Pennsylvania that he named Paramphibius because he thought the trackmaker was a transitional form between
fishes and
tetrapods. He named a new taxon, the
Ichthyopoda to classify this creature.[34]
Roland T. Bird discovered a new Early Jurassic dinosaur tracksite in the
Moenave Formation of northwestern
Arizona. Although the site's location would be lost, Bird's photographs would help
Dinosaur National Monument paleontologist Scott Madsen, and friend Keith Becker, relocate the site decades later.[37]
Late: An expansion of the Nevada State Prison was built over the Pleistocene fossil footprints that had been discovered there. However, some specimens had been collected before and are now curated by the
Nevada State Museum.[39]
Maurice Mehl erected the new ichnogenus Ignotornis for some bird tracks preserved in the Dakota Group near
Golden, Colorado. These were the first scientifically documented
Mesozoic bird footprints.[40] The bird in question as interpreted as a "small
shorebird or
wader".[41] The site would eventually be heavily collected and all of its tracks were presumed removed.[40]
Edward Branson and Maurice Mehl named a new kind of Late Triassic dinosaur footprint discovered in the
Popo Agie Formation of western Wyoming. The new ichnogenus and species was named Agialopus wyomingensis.[43]
The
Dinosaur Ridge dinosaur tracksite was discovered near
Denver, Colorado. Tracks include those made by ornithopods and theropods. Some of the ornithopod tracks seem to have been left by individuals traveling together and are thus evidence for social behavior.[47] Further, these ornithopods seem to have traveled predominantly on all fours, unlike most ornithopod tracks, which were made by bipeds.[48]
The New York Times reported that
Barnum Brown had discovered the fossil footprints of a huge and unknown kind of dinosaur in a Wyoming coal mine. Brown's claim was simply a "publicity stunt" aimed at attracting funding.[49] However, Brown's report attracted the attention of a coal mine operator from the
Cedaredge, Colorado area named Charlie States, who reported large dinosaur footprints spaced five meters apart in his mine, the Red Mountain Mine.[50] Brown and his assistant Roland Bird oversaw an "ambitious" excavation of the purported giant's tracks. After three weeks of 24-hour labor on the part of the miners and the development of specialized equipment to extract the specimen, a 17-foot long slab of track-bearing rock was taken from the mine and shipped to the
American Museum of Natural History in
New York City.[51]
More Late Triassic dinosaur footprints were discovered near Gettysburg. These tracks ranged from chicken-sized to 15 cm (5.9 in) in length.[44]
Kenneth Caster conclusively demonstrated that unusual fossil tracks from the Solnhofen lithographic limestone variously attributed to creatures like Archaeopteryx, little dinosaurs, or pterosaurs were actually made by
horseshoe crabs, as specimens had been found literally "dead in their tracks".[52] Similar fossils in the United States had been attributed to a transitional form between fishes and tetrapods by Bradford Willard earlier in the 1930s.[34]
Brown published a description of the dinosaur tracks with the purported giant stride length. He tried to keep up his charade of there being an undiscovered mystery dinosaur by downplaying "the obvious
hadrosaurian affinity of the tracks".~???NA220-221~
Nash bought the Massachusetts property where he discovered dinosaur footprints. He would begin excavating and selling the dinosaur footprints on his land and the property would come to be known as
Nash Dinosaur Land.[45]
Lionel F. Brady began experimenting with living arthropods to help determine which sorts of arthropods may have produced various ancient trace fossils.[53]
Sumner Anderson reported the presence of small carnivorous dinosaur footprints between 15 and 20 cm in length preserved in the Early Cretaceous
Lakota Formation at two different sites in
South Dakota.[54]
Earl L. Poole of the
Public Museum and Art Gallery discovered a new Late Triassic dinosaur track site at a quarry near
Schwenksville, Pennsylvania.[44] The dozens of tracks preserved there were mostly left by
chicken-sized dinosaurs, but about a "half dozen" of them were left by turkey-sized trackmakers.[55] Poole ascribed these tracks to the ichnogenus Anchisauripus. One footprint was left by a dinosaur with about the same body mass as a
horse.[45] This site is now known as the
Squirrel Hill Quarry.[44]
1940s
Frank Peabody performed "extensive" research on Early Triassic fossil footprints.[56]
Roland T. Bird oversaw the excavation of sauropod and theropod tracks from the
Paluxy River in Texas. This was the first large-scale dinosaur track excavation in history.[57]
Frank Peabody studied the early
Pliocene fossil amphibian footprints of the
Sierra Nevada Mountains of
California. He found them to be almost identical to the tracks of their descendants. This was his first major contribution to ichnology.[58]
Robert Chaffee reported the presence of a tracksite from Wyoming preserving the footprints of a
camel-like
even-toed ungulate and a
rhinoceros-like odd-toed ungulate in the Oligocene-aged
White River Beds. He noted that only two other Oligocene fossil tracks were known and neither had been described.[62] Chaffee attributed one of these, a partial print preserved in the
Yale Peabody Museum, to a
brontothere.[63]
F. E. Peabody published a study of the amphibian and reptile tracks preserved in the Triassic Moenkopi Formation. Lockley and Hunt would later regard this paper as "a classic" in the field.[64]
1950s
A rock hound named Al Look "embellished" Barnum Brown's mystery dinosaur hoax, informally naming the creature "Xosaurus". He also reported having encountered another dinosaur trackway with a similarly long stride as Brown's original specimen. This trackway supposedly recorded the huge mystery dinosaur stepping on a crocodile-like reptile.[66]
Albert de Lapparent and others restudied the large Late Jurassic theropod tracks of Cabo Mondego.[24] They thought the tracks were made by Megalosaurus.[67]
Henry Faul and Wayne Roberts reported the presence of Early Jurassic fossil footprints in Colorado's
Navajo Sandstone. These tracks were probably left by an evolutionary precursor to mammals.[6]
Wilhelm Bock reinterpreted the footprints discovered in the Squirrel Hill Quarry as Grallator and non-dinosaurian
archosaur tracks. He also described the ichnospecies Anchisauripus gwynnedensis for a dinosaur track discovered in the
North Pennsylvania Railroad tunnel near
Gwynned. These tracks are now thought to belong to Atreipus, however.[45]
A French ichnologist named
Lessertisseur erected the ichnogenus Megalosauripus. He attributed the Cabo Mondego tracks to a
megalosaurid.[70] He also named the ichnogenus Tyrannosauripus, but as both ichnogenera lacked type species and type specimens these taxonomic names were invalid.[71]
M. F. Farmer published the locations of many track sites in northern Arizona.[72]
Lee Stokes erected the new ichnogenus Pteraichnus for fossil footprints discovered in the Morrison Formation of Utah that he thought were left by pterosaurs.[6]
Oskar Kuhn named the new Early Cretaceous theropod ichnogenus and species Buckeburgichnus maximus from Germany. It is notable in its preservation of a large
hallux impression.[74]
August 3rd:Albert de Lapparent and
Robert Lafitte stumbled on some fossil footprints left by a large bipedal dinosaur in the
Festningen Sandstone at
Isfjorden, Svalbard.[76] The researchers suspected that the tracks were made by a
carnosaur. At 78 degrees of latitude north, these were the highest latitude dinosaur tracks known in the world, up from the previous record of 56 degrees.[77]
A
geologist named
H. D. Curry working for the
Shell Oil Company discovered a slab of rock preserving high quality three-toed mammal footprints in Utah's
Strawberry Canyon. The trackmakers were probably Eocene relatives of modern
tapirs and
horses. Curry donated the so-called "Strawberry Slab" to the Smithsonian Institution.[78]
Albert de Lapparent reinterpreted the dinosaur tracks from Spitzbergen. Although mentioning their initial impression that the tracks were carnosaurian, he concluded that the tracks were probably left by Iguanodon instead, due to their lack of claw marks, rounded toe prints, and general similarity to the feet of Iguanodon bernissartensis.[77]
Panin and
Avram published research on
Miocene fossil bird and mammal tracks from the vicinity of the
Carpathian Mountains of
Romania. They attributed the local bird footprints to four different families, the
anatids,
ardeids,
charadriids, and
gruids. Contemporary mammalian trackmakers included
artiodactyls,
cats,
dogs, and
relatives of modern elephants. The latter of these left behind one thoroughly trampled site with an area of more than 100 sq m. The researchers erected several new ichnotaxa for the tracks they studied and similar tracks would later be discovered elsewhere in Europe.[79]
The first dinosaur footprints known from Israel were discovered.[80]
A large pseudosuchian named Tichinosuchus was named for remains found in Swiss Triassic rocks. It had the right size and anatomy to account for the Chirotherium tracks of Europe and is considered the most likely trackmaker.[82]
de Raaf,
Beets, and
Kortenbout van der Sluijs reported the presence of a large number of well-preserved web-footed bird tracks from
Oligocene rocks in Spain.[83] The high percentage of the fossil trails being oriented in the same direction suggests that this deposit records evidence for flocking in these ancient birds. This is extraordinary because evidence for social behavior in fossil bird footprints is very uncommon.[32]
March: A coal miner working near
Hayden, Colorado hit his head on the natural cast of a dinosaur footprint while in pursuit of a run-away coal cart. The impact injured his spinal cord, leading to his death 10 days later.[85]
1970s
Mid: Dinosaur tracks of the ichnogenera Atreipus and Grallator were discovered in a quarry that straddles the Virginia-
North Carolina border. These may be the oldest dinosaur tracks known in the eastern United States.[86]
Late: The publication of a formula capable of inferring the life speeds of dinosaurs from their fossil trackways brought further attention to Barnum Brown's claim of having discovered the tracks of a mystery dinosaur with an abnormally long stride length. Scientists instantly recognized the footprints as belonging to a duck-billed hadrosaur rather than some completely unknown dinosaur, but the validity of the trackway's stride length proved controversial.
Dale Russell and
Pierre Beland accepted Brown's measurement and calculated the trackmaker as moving at 27 kilometers an hour.
Tony Thulborn argued that a footprint left by another dinosaur obscured a track left by the original trackmaker roughly halfway between the prints composing the supposedly enormous stride. This implied that the trackmaker's stride was only half the claimed size and it was probably only traveling at about 8.5 kilometers an hour.[66]
Leonard Wills and
Bill Sarjeant reported potential dinosaur footprints from Triassic rocks in
Nottinghamshire and
Worcestershire. Ichnotaxa reported included Coelurosaurichnus, Otozoum, and Swinertonichnus. The rocks were of uncertain age at the time of the authors writing and are now known to have been Lower Triassic.[87] Dinosaur tracks dating to the Early Triassic would be anomalous as their skeletal remains are not known until later in the period.[88] Not surprisingly, the dinosaurian status of the tracks reported by Wills and Sarjeant have been disputed.[87]
Haubold formally named the German ichnospecies Metatetrapous valdensis from Germany's Wealden Beds. The discovery may represent fossil
ankylosaur footprints.[89]
de Clercq and Holst published on the Upper Oligocene bird tracks of
Lucerne, Switzerland. The researchers attributed the tracks to
rails.[90]
Vialov classified fossil bird footprints as members of the ichno order Avipedia.[93]
David Webb studied the fossil footprints left by ancient camels and determined that even these ancient forms shared modern camels' "pacing gait", where the animal moves both legs on one side of the body at the same time, unlike most mammals which move hindlimbs and forelimbs from the opposite sides of the body in each step. Webb argued that the energetic efficiency of the pacing gait enabled camels' success in desert and prairie environments where significant distances may separate food and water sources.[94]
Paul Olsen and
Robert F. Salvia discovered dinosaur Late Triassic footprints in the
Stockton Formation of
Nyack Beach State Park, New York. The tracks included 12–15 cm (4.5–6 in) long Grallator tracks. Possible Atreipus tracks were also found there. The regions's non-dinosaurian tracks included Apatopus, Brachychirotherium, Chirotherium, and Rhynchosauroides.[95]
Justin Delair and
A. B. Lander reported the presence of three parallel dinosaur trackways in the Roach Stone of Herston, England.
A significant Permian-aged fossil tracksite in the
Cedar Mesa Sandstone of Utah was inundated following the creation of the
Glen Canyon Dam. This tracksite preserved an apparent predator-prey interaction wherein the trail left by a small amphibian or reptile vanished at the point where it intersected with the trail left by a large carnivorous proto-mammal. Fortunately for ichnologists, plaster casts of the trackways and photographs remain available for study.[96]
Kaever and de Lapparent named the new ichnogenus and species Elephanotpides barkhausensis for the poorly preserved tracks of a large quadrupedal dinosaur discovered near Barkhausen, Germany. The trackmaker was probably a sauropod.[97]
Heinberg describes
Ancorichnus, a non-marine burrowing animal.[98]
Bill Sarjeant described the five-toed Middle Jurassic footprints discovered by C. Pooley and named it Pooleyichnus burfordensis in his honor.[100] Sarjeant proposed that this unusual track may have been made by a mammal.[101]
A large tracksite preserved in the late Eocene
Vieja Group of Texas was first studied in a
University of Texas research program.
Robert E. Weems was informed of, and began researching, a Late Triassic reptile track site in a quarry near
Culpeper, Virginia.[102]
Leon Pales described the Pleistocene human footprints of France's Niaux cave complex. This paper has been considered "one of the most comprehensive studies of cave footprints ever published."[17]
R. McNeil Alexander published a formula for inferring the speeds of dinosaurs from their fossil trackways.[72]
Russell and Beland examined Brown's claim to have discovered the tracks of a running dinosaur.[104]
Several hundred Late Triassic dinosaur footprints were reported from the vicinity of Cardiff, Wales.[105] This report was made by
M. E. Tucker and
T. P. Burchette.[106]
Marc Edwards and others reported the dinosaur footprints discovered in Spitzbergen in 1978. Only two footprints were discovered at the site, which was an exposure of the Helvetiafjellet Formation. The researchers interpreted the tracks as carnosaur footprints, but now they are thought to have been left by
iguanodontids.[108]
Stokes observed that tracks left by close evolutionary relatives of mammals were common and widespread in the Navajo Sandstone. He found such tracksites in Colorado,
Idaho, and Utah.[109] He reported many new sites in the Navajo formation.[92]
Ismael Ferrusquia-Villafranca and others reported the discovery of the first dinosaurs tracks to be scientifically documented in Mexico.[110]
Carme Lompart reported the presence of Late Cretaceous dinosaur tracks in the
Ager Valley of Spain, near the country's border with France.[112]
Marc Weidmann and
Manfred Reichel published a "lengthy" review of the Oligocene to Miocene aged bird tracks found in Switzerland's "Molasse" rock.[90] They reported the presence of tracks left by one kind of
duck, two kinds of
herons, one kind of
perching bird, and four kinds of
waders.[113] Weidmann and Reichel devoted intense effort to classifying these tracks based on previous schemes devised by scholars like Avram, Panin, and Vialov for other bird track sites.[93] They also worked diligently to discern the tracks' positions within the stratigraphic column.[114]
A nine meter long Pleistocene
bear trackway was reported from
Lake County, Oregon. The tracks themselves were about 40 cm long, suggesting a trackmaker roughly the size of a large modern bear. These tracks may have been left by an Arctotherium.[117]
Olsen argued that the ichnogenera Grallator, Anchisauripus, and Eubrontes actually represent a growth series.[69]
Walter P. Coombs, Jr. interpreted some unusual Eubrontes tracks from Dinosaur State Park of
Rocky Hill, Connecticut as traces left by a swimming theropod because the tracks only preserved impressions from the tips of the animal's toes as if the rest of its body weight was supported by water.[118]
Demathieu and Haubold described the new Early Triassic ichnogenus and species Isochirotherium archaem from Germany. As only the hind prints are preserved in this trackway it may represent the oldest evidence in the world for the existence of animals with bipedal gaits. However, while intriguing, their remains the possibility that the track maker was a quadruped and its foreprints eroded away before the trail was discovered.[121]
Demathieu and
Marc Weidmann described a new Triassic fossil tracksite from Switzerland called the
Vieux Emosson tracksite.[122]
Geology student Jeff Pittman recognized that the "potholes" hindering excavation equipment traffic through a gypsum mine in southeastern Arkansas were actually sauropod dinosaur footprint.[123]
Hartmut Haubold published the
Saurierfahrten.[124] Haubold was a German ichnologist, and the Saurierfahrten a specialist's handbook for identifying Carboniferous and Permian fossil footprints. It was the only publication of its type in the world at the time and only available in German.[125]
Paul Olsen and
Peter Galton argued that Ellenberger had oversplit the Late Triassic and Early Jurassic ichnotaxa he studied and that many of the kinds of tracks he regarded as distinct were the tracks previously described in eastern North America.[126]
J. E. Andrews and J. D. Hudson reported the first dinosaur tracks to be scientifically documented in Scotland. The tracks are three-toed and preserved in the Middle Jurassic
Leate Shale.~144~
George Demathieu and others described an Oligocene bird and mammal track site from southeastern France. Three different mammalian ichnotaxa were present. One was an artiodactyl track they named Bifidipes velox. The second was the largest of the three, Ronzotherichnus, was apparently left by the rhinoceros Ronzotherium. A
creodont or early carnivoran left behind the third kind of tracks, which the researchers named Sarcotherichnus enigmaticus. They named the bird tracks at the site Pulchravipes magnificus.[84]
Kevin Padian and Paul Olsen reinterpreted the supposed pterosaur tracks named Pteraichnus from the Morrison Formation of Utah as crocodilian tracks.[120]
Luis Aguirrezabala reported the presence of nine parallel trails left by Hypsilophodon or one of its close relatives in Lower Cretaceous rocks of
La Rioja, Spain. This tracksite is now known as the Valdevajes site.[127]
An international symposium for paleontologists performing research on "Dinosaur Tracks and Traces" was held in New Mexico.[128] The gathering was a success and "led to the rejuvenation and maturing of the discipline of dinosaur ichnology".[129]
Paul Ensom reported dinosaur tracks from the Purbeck Limestone of Dorset, England.[131]
Lockley disputed
Robert T. Bakker's hypothesis that an Early Cretaceous sauropod trackway from the Davenport Ranch, Texas area preserves evidence that sauropods traveled in herds with the young surrounded by the adults to protect them from predators. Instead, Lockley interpreted this trackway as a herd of sauropods traveling through a narrow area, with the young following the adults.[132]
Lockley and Hunt began studying the dinosaur tracks of the Dakota Group at the
Alameda Parkway site, which is now called
Dinosaur Ridge.[133]
Lockley described the ichnogenus Caririchnium. This publication was also the first detailed treatment of the Dakota Group's trace fossil record in the scientific literature.[134]
Robert E. Weems published the results of his research into the Late Triassic reptile tracksite near
Culpeper, Virginia. Among the fossil footprints he found there were the dinosaur ichnogenera Agrestipus, Grallator, Gregaripus, and Kayentapus.[102]
Harald von Walter and
Ralf Werneberg reported the discovery of body impressions left behind by
diplocaulid amphibians in the Rotliegende of the Thuringian Forest area. The assemblage includes the body impression of several individuals, all no more than a few centimeters in length.~46~ The authors named these traces Hermundurichnus fornicatus.[135]
Lockley and Hunt rediscovered fossil bird footprints in the Dakota Group near Golden Colorado.[136] Among the specimens recovered was the first in the world to preserve dinosaur and bird footprints together.[137]
Lockley reported the first observation in the Dakota Group of dinosaur footprints with preserved skin impressions.[134]
W. A. S Sargeant and
J. A. Wilson reported the presence of Eocene mammal footprints in Texas.[138]
R. Santamaria,
G. Lopez, and
M. L. Casanovas-Cladellas reported an Oligocene mammal track site discovered near
Agramunt, Spain. This tracksite preserved four new ichnospecies, three of which were in new ichnogenera. First was a new species of Bothriodontipus, which was made by the pig-like animal Bothriodon or a close relative. The researchers new ichnogenera were Creodontipus and Plagiolophustipus.[84] They classified two of their new ichnospecies in Creodontipus, an ichnogenus they fittingly attributed to creodonts. They attributed Plagiolophustipus to tapir-like animals distantly related to horses.[139]
Jeff Pittman proved that the sauropod tracks he recognized in an Arkansas
gypsum mine were actually at the same level of the geologic column as the Glen Rose Formation sauropod tracks of Texas.[140]
Farlow, Pittman, and Hawthorne described the ichnogenus Brontopodus.[60]
April: A quarry worker named Robert Clore blasting stone near Culpeper, Virginia uncovered a new Late Triassic reptile tracksite.[141] Weems began studying the site that same year, and reported the presence of 4,000 individual tracks. The local tracks included the dinosaur ichnogenera Grallator and Kayentapus. Other tracks may have been left by
aetosaurs.[142]
Ryszard Fuglewicz and others reported fossil trackways from the
Holy Cross Mountains of
Poland that may be the oldest Triassic trackways in Europe. They reported tracksites at six different positions within a stratigraphic series in several distinct paleoenvironments including river channels and floodplains. The ichnogenera they identified in these tracksites included Brachychirotherium, Capitosauroides, Isochirotherium, Rhynchosauroides, and Synaptichnium.[143]
C. Lancis and
A. Estevez reported the presence of early Pliocene tracks preserved near
Alicante, Spain. Among the mammals who left their mark here were members of the horse family and bears.[148]
Farlow observed that sauropod trackways could be categorized as either being "narrow-gauge" or "wide-gauge".[149]
Mid November: Lockley and Hunt's research group at the University of Colorado undertook one of the few major dinosaur footprint excavations in history in order to expand the exposed track-bearing surface at Dinosaur Ridge for an outdoor interpretive center.[150]
Lockley and dos Santos described the
Kimmeridgian-aged
Avelino quarry tracksite near
Lisbon, Portugal, the first scientifically documented sauropod dinosaur tracksite in Europe to contain well-preserved tracks of the animals' front feet. All of the trackmakers seem to have been juveniles.[153]
Meyer reported the first scientifically documented Late Jurassic dinosaur footprints from Switzerland. These tracks were discovered near the town of
Lommiswil.[154]
Claude Guerin and George Demathieu described the new ichnospecies Dicerotichnus laetoliensis. This ichnospecies was left behind by a late Pliocene rhinoceros of fairly modern build, possibly from the genus Diceros. Its tracks are preserved at the same site known for its ancient
hominid tracks.[84]
A non-technical article in the Spanish magazine Blanco y Negro discussed the wide variety of Miocene tracks preserved at
Salinas de Anana, Spain.[155]
Lockley and Hunt introduced the idea of
ichnofacies to the scientific literature. They described and named the Brontopodus ichnofacies based on sauropod tracksites in Texas.~NA210~[citation needed]
A new tracksite was discovered in
Toadstool Park area of Nebraska's
Oglala National Grassland.[156] Eleven different trackmakers have been documented here, including camels, carnivorans, ducks, rhinoceroses, and shorebirds.[157]
Lockley and others argued that Deltapodus was probably not left by a sauropod because the hind prints had only three toes and the tracks themselves were preserved in an environment where sauropod tracks are not generally found.~135~ Instead they concluded it was more likely to be the tracks of a
thyreophoran, possibly a
stegosaur.[159]
A cave enthusiast near
Fatima, Portugal looked down on a quarry from a high ridge and noticed that its floor was covered in sauropod footprints.[160] The site included the longest known dinosaur trails at the time. The individual tracks are the largest sauropod prints known from the Middle Jurassic and include the largest foreprints of any known sauropod track type.[161]
Lockley, Hunt, and Meyer defined the Brontopodus ichnofacies.
Galopim published The Battle of Carenque, a book describing the successful efforts of Portuguese conservationists to save the home of the world's longest dinosaur trackway from being destroyed by freeway construction.[162]
Bill Sarjeant and Wann Langston published a monograph on the late Eocene track site from the Vieja Group of Texas. The tracks preserved there indicate a fauna including six kinds of bird, two kinds of invertebrate, nineteen mammal species, and two kinds of turtle.[164]
Hunt, Lockley, and Lucas reported the existence of a fossil trackway preserving an apparent act of predation of a
pelycosaur upon a small reptile.[29]
Lockley, Hunt, and Meyer proposed the idea of vertebrate
ichnofacies.[25]
Lockley and Hunt defined the Brontopodus and Caririchnium ichnofacies.[134]
Iwan Stossel reported the oldest known fossil vertebrate footprints in Europe to the scientific literature.[165] The tracks were preserved in the
Mid-
Late Devonian
Valentia Slate of
Valentia Island, which lies off the southwestern coast of
Ireland. Roughly 150 tracks were present in an 8 meter long trail left behind by an early tetrapod.[166]
David Scarboro and
Maurice Tucker reported the discovery of a fossil trail probably left by a
temnospondyl amphibian about 1.5 meters long walking through a delta during the Middle Carboniferous. The find is one of the largest Carboniferous fossil trackways in all of Europe.[167]
Jean-Michel Mazin and others described the first scientifically documented pterosaur fossils from Europe. These tracks were preserved in a Late Jurassic limestone in
Crayssac, France.[168] The pterosaurs that left these footprints seem to have been in the sparrow to sea gull size range. These tracks have played a "pivotal" role in confirming that various unusual and controversial trace fossils reported around the world really were made by pterosaurs after all.[169]
April: Fabio Dalla Vecchia and one of his students were arrested while mapping dinosaur footprints in Croatia and inadvertently following the tracks into a military zone. They were tried and subsequently fined their trial expenses and released.[170]
Koenigswald, Walders, and Sander described a 30,000- to 20,000-year-old Pleistocene fossil mammal track site from
Bottrop, Germany. Local trackmakers included
bison, horses,
cave lions,
reindeer, and wolves.[171]
Price argued that scholars generally underestimated how long ago humanity first domesticated horses based on a
Bronze Age tracksite in Sweden.[172]
Phylis Jackson argued that the pedal anatomy of
Anglo-Saxon and
Celtic peoples are so distinct that these populations can be distinguished based on feet alone going all the way back to the
Neolithic.[173] Celtic people have narrower feet while Anglo-Saxon feet are broader.[174]
Fuentes Vidarte reported the oldest known bird tracks in the world from the Berriasian Wealden Beds of the Villar del Rio, Spain.[145]
Fabio Dalla Vecchia returned to Croatia and finished mapping the dinosaur footprints with Croatian geologist
Igor Vlahovic.[175]
Fabio Dalla Vecchia and Marco Rustioni reported a Miocene mammal tracksite in the
Conglomerato di Osoppo in
Udine Province, Italy. Across its 100 square meter area the track site preserved the footprints of three different kinds of large mammal.[79]
The first international workshop on Paleozoic footprint fossils, presided over by Hartmut Haubold was held in Germany.[128] The symposium was such a success that it is regarded as a turning point in the history of Paleozoic vertebrate ichnology.[129]
Avanzini,
van den Dreissche and
Keppens concluded that the tracks preserved at Lavini de Marco in Italy were cemented through chemical processes trigger by the rapid evaporation of water from the carbonate track-bearing substrate and speculated that similar circumstances may have preserved tracks in carbonates at other sites and different positions in the stratigraphic column.[176]
Meyer reported that the Late Jurassic dinosaur tracks discovered near Lommiswil, Switzerland were actually part of a gigantic megatracksite. This was the first report of a dinosaur megatracksite in Europe.[177]
Wright and others re-examined the Purbeckopus pentadactylus tracks from Dorset, England and concluded that not only were they pterosaur tracks, but they were among the largest known pterosaur tracks in the fossil record.[81]
Tuner and Anton attributed Miocene cat footprints found at Salinas de Anana, Spain to the genus Pseudaelurus. These tracks may in fact be the oldest known cat footprints in the world.[155]
Phylis Jackson published further research on the use of pedal anatomy and footprints to distinguish different groups of people.[173]
Lockley, dos Santos, and Hunt found the purported hypsilophodont tracks of the Spanish Valdavajes tracksite similar to the Late Jurassic ichnogenus Dinehichnus that has been attributed to
dryosaurids.[127]
Lopez-Martinez and others noted the presence of sauropod and ornithopod tracks near the
K-T Boundary in the
Tremp Formation of northeastern Spain. The presence of tracks so close to the Cretaceous-Tertiary suggests that the dinosaur died out rapidly rather than gradually.[179]
^Lockley and Hunt (1995); "Parallel Trackways and Dinosaur Herds", pages 196–197 and "The Dinosaur Freeway", page 209.
^Lockley and Hunt (1995); For role of the dinosaur renaissance, see "Preface", page xvi. For paleontologists' need for data following the publication of Alexander's formula, see "The Case of the 'Mystery Dinosaur'", page 221.
Lockley, Martin G.; Hunt, Adrian (1995). Dinosaur Tracks and Other Fossil Footprints of the Western United States. Columbia University Press. p. 338.
ISBN978-0231079266.
Lockley, Martin G.; Meyer, C. A. (2000). Dinosaur Tracks and other fossil footprints of Europe. New York: Columbia University Press.
ISBN0-231-10710-2.
Moore, Randy (2014). Dinosaurs by the Decades: A Chronology of the Dinosaur in Science and Popular Culture. Santa Barbara: Greenwood. p. 472.
ISBN978-0-313-39364-8.