The Late Triassic sauropod track reconrd comes into focus: Old legacies and new paradigms
Martin G. Lockley, Joanna L. Wright, Adrian P. Hunt, and Spencer G. Lucas
Vertebrate tracks assigned to the ichnogenera Tetrasauropus and Pseudotetrasauropus (cf. Otozoum) have traditionally been attributed to robust and gracile prosauropods, respectively. Based on track morphology, we propose that the former ichnogenus (Tetrasauropus), as represented in the uppermost Triassic (Norian-Rhaetian) of western North America, and other regions, can be attributed to the Sauropoda. The suggestion that sauropod tracks exist in the Upper Triassic is no longer at variance with the body fossil record, as it was until recently. Previous failure to attribute Tesrasauropus to the Sauropoda provides a good example of the reluctance of ichnologists to make interpretations that do not concur with the skeletal record. While such caution is advisable in the still-specialized and immature science of vertebrate ichnology, it may also lead us to misinterpret important, even abundant, ichnological evidence that is easily accessible. Hindsight has revealed many other instances of the predictive potential of ichnology, and the reluctance of mainstream paleontology to accept predictions that have not been absolutely confirmed by osteological evidence.
Parallel evolutionary trends towards larger size in theropod tracks (e.g., Grallator), prosauropod tracks (Pseudoterrasauropu and Otozoum) and presumed sauropod tracks (Tetrasauropus and Brontopdus, or Brontopodus-like ichnotaxa) suggest that the interpretations proposed here are the most parsimonious and internally consistent. They indicate a convergent unfolding of evolution among all saurischian clades during the Late Triassic into the Jurassic.
- Lockley, Martin G.; Wright, Joanna L.; Hunt, Adrian P.; Lucas, Spencer G., 2001, The Late Triassic sauropod track reconrd comes into focus: Old legacies and new paradigms, in: Geology of the Llano Estacado, Lucas, Spencer G.; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 52nd Field Conference, pp. 181-190.