20th century in ichnology

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. 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".
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 prosauropod dinosaur "Plateosaurus", 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. 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.
During the 20th century, many significant fossil trackway discoveries were made in the western United States. In the 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. In the Lee Stokes reported unusual footprints he interpreted as the first known pterosaur tracks. This attribution would be controversial much of the rest of the century but has since been vindicated. The dinosaur footprints of Dinosaur Ridge in Colorado were also discovered and studied in the 20th century.
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. 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. 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.
1900s.
1900
1902
1903
1904
1905
1906
1908
1909
1910s.
1910
1913
c. 1914
1914
1915
1915-1916
1918
1920s.
c. 1920
1923
1924
1925
1926
1927
1928
1929
1930s.
1931
1932
1933
1936
1937
1938
c. 1939
1939
1940s.
1940
1941
1943
1944
1947
1948
1950s.
1951
1952
1953
1954
1955
1957
1958
1959
1960s.
1960
1962
1963
1965
1966
1967
1968
1969
1970s.
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980s.
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990s.
1990
1991
1992
1993
1994
1995
1996
1997
1998