The Cambrian (Sunwaptan, Furongian) agnostoid arthropod Lotagnostus Whitehouse, 1936, in Laurentian and Avalonian North America: systematics and biostratigraphic significance.

摘要

Restudy of type and other material shows that the Cambrian (Sunwaptan, Furongian) agnostoid arthropod Lotagnostus americanus (Billings, 1860), far from being distributed globally, can be identified with confidence only at its type locality of Quebec. As such, it is ill-suited as an index for international correlation. Lotagnostus obscurus Palmer, 1955, from Nevada is not a synonym of L . americanus and is most similar to other effaced species from Australia. Sclerites from Avalonian Canada are represented by perhaps as many as two species, one of which is L . germanus (Matthew, 1901), and the other is similar to the type species, L. trisectus (Salter, 1864). However, loss of information due to compaction makes L. trisectus difficult to interpret in its type region of Avalonian Britain, and possible occurrences in other areas are therefore questionable at best. At the current state of knowledge, this species name should not be applied outside of Avalonian Britain. Aside from L . obscurus , which may possibly appear in slightly older strata, all Laurentian occurrences are confined to Upper Sunwaptan successions. Most are in the Illaenurus and Prosaukia pyrene zones, although review of material assigned to L. hedini (Troedsson, 1937) in western Newfoundland suggests that this species may occur, albeit questionably, only in the basal Skullrockian Phylacterus saylesi Fauna; indeterminate species occur in the Keithia schucherti Fauna in the latter region. Occurrences in Avalonian Canada are all from the upper Peltura Zone, and are likely somewhat younger (Saukiella junia Subzone and correlatives) than those in Laurentian successions.