Article: Asteroid and ophiuroid trace fossils from the Lower Cretaceous of Chile
C. M. Bell
Abundant asterozoan trace fossils in the Lower Cretaceous Apeleg Formation of southern Chile were produced by the infilling of traces made by asteroids and ophiuroids on a muddy surface. Most are preserved as hypichnial ridges formed as casts on the bottom of fine-grained sandstone laminae. Star-shaped Asteriacites lumbricalis are interpreted as the infillings of shallow excavations made by asteroids. Hook-shaped and sinuous ridges of the newly defined ichnogenus and ichnospecies Ophioichnus aysenensis are interpreted as the casts of imprints made by the walking action of the arms of ophiuroids. Deposition probably took place in an offshore tide-swept marine shelf environment. In life the animals formed an assemblage equivalent to echinoderm aggregations on the modern sea floor.