This is the third volume (second supplement) to the series, Geology of the Grand Canyon: An Annotated Bibliography with An Annotated Catalogue of Grand Canyon Type Fossils. The first two volumes were published in 1983 and 1984, respectively, as Geological Society of America Microform Publications 13 and 14. The current volume cites references published as late as September, 1987, but by no means does this imply that the bibliography or lists of new fossil taxa are comprehensive to that date. This work is very much an ongoing project.
Of special note in Volume 3 is the inclusion of a third part, “An annotated Bibliography of the World Literature on the Grand canyon Type Fossil Chuaria circularis Walcott, 1899, an Index Fossil for the Late Proterozoic” This bibliography was prepared as a separate publication. However, it is apparent from reading the very recent literature (see particularly Sun, 1987) that Chuaria should not be relied upon as an infallible index fossil for the late Proterozoic. The fossil is somewhat unreliable not because of poor stratigraphie resolution, but that it is difficult to identify on morphological characters alone. Instead, the assemblage of Chuaria Walcott, 1899, and Tawuia Hofmann, 1979, are regarded as a reliable index fossil assemblage when they occur together (Sun, 1987). Chuaria (and itc many synonyms) has had such a remarkable research history, since as early as 1876, found worldwide, that it seems appropriate to present this bibliography in its historical context as one of a particularly enigmatic Grand Canyon Type Fossil. Chuaria clearly was known to science a century before the associated Tawuia was described by Hofmann (in Hofmann 6 Aitken, 1979). Recent research on these taxa has burgeoned in the world literature. Their biologic affinities are known with reasonable certainty, but we are still pretty much at a loss to satisfactorily describe Chuaria taxonomically even though it is one of the few