21. Much more commonly, it contains trace fossils , especially the tetrapod footprints of " Chirotherium ". 22. Trace fossils have been found in the Willwood Formation.23. Most trace fossils are burrows of molluscs or arthropods. 24. Most trace fossils are usually readily identified by reference to similar phenomena in modern environments. 25. Also found in the Owl Rock are trace fossils of cylindrical burrows and fossils of ostracodes. 26. Tetrapod footprints, worm trails and the burrows made by clams and arthropods are all trace fossils . 27. Trace fossils can also provide insight into behavior.28. The second floor holds a variety of invertebrates, trace fossils , minerals, and exhibits on local geology. 29. The only known fossils from this time period is the tube-shaped trace fossil " Skolithos ". 30. The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates as well as trace fossils of invertebrates.
