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TitleThe Psammichnites-Taphrhelminthopsis conundrum: implications for calibrating the Cambrian explosion
AuthorMángano, M G; Buatois, L A; MacNaughton, R BORCID logo; Jensen, S; Gougeon, R; Marcos, A; Meek, D; Piñuela, L; García-Ramos, J C
SourceEarth-Science Reviews vol. 227, 103971, 2022 p. 1-20,
Alt SeriesNatural Resources Canada, Contribution Series 20210382
Mediapaper; digital; on-line
File formatpdf; html
AreaAsturias; Spain
Lat/Long WENS -6.1833 -6.1667 43.5667 43.5500
Subjectspaleontology; Science and Technology; Nature and Environment; systematic paleontology; taxonomy; evolution; trace fossils; ichnofossils; ichnology; marine environments; bedrock geology; lithology; sedimentary rocks; sandstones; fossil morphology; paleogeography; Taphrhelminthopsis; Psammichnites; Cambrian Explosion; Phanerozoic; Paleozoic; Cambrian
Illustrationstables; location maps; geoscientific sketch maps; photographs
ProgramGEM-GeoNorth: Geo-mapping for Energy and Minerals GEM Program Coordination
Released2022 03 05
AbstractTaphrhelminthopsis was originally introduced for trace fossils with a bilobate lower surface recorded in post-Paleozoic deep-marine deposits but has more recently been reinterpreted convincingly as a preservational variant of Scolicia. However, Taphrhelminthopsis has also been used for Cambrian shallow-marine trace fossils, whose taxonomic affinity remains elusive. This practice was introduced with the erection of Taphrhelminthopsis circularis Crimes et al., 1977, based on specimens from lower Cambrian strata of Asturias, Spain, that have a bilobate morphology with a median furrow and a tendency to form a roughly circular course. Taphrhelminthopsis circularis subsequently has been recorded in many lower Cambrian successions worldwide. No information on toponomy was provided in the original description, which has complicated the reevaluation of this ichnotaxon. Reanalysis of the type specimen and study of additional material at the type locality demonstrate that Taphrhelminthopsis circularis occurs on the tops of sandstone layers, with a convex-upward bilobate structure, representing a preservational and behavioral variant of Psammichnites, in agreement with earlier tentative proposals. The presence in some material of a sinuous axial furrow, which is regarded as diagnostic of Psammichnites gigas, argues for synonymization of Taphrhelminthopsis circularis with that ichnospecies. However, to underscore potentially significant preservational and behavioral variability, we refer to this form as Psammichnites gigas circularis. We also discuss the relationships between Psammichnites and other trace fossils commonly recorded from Cambrian shallow-marine strata under a wide variety of names, including Archaeonassa fossulata, Arcuatichnus wimani, Helminthoida crassa, Helminthoida miocenica, Multilaqueichnus ganluonensis, Multilaqueichnus meishucunensis, Nereites saltensis, Parapsammichnites pretzeliformis, Plagiogmus arcuatus, Sellaulichnus meishucunensis, Taphrhelminthoida dailyi, Taphrhelminthopsis nelsoni, and Taphrhelminthopsis minimus. We recommend reassigning Plagiogmus arcuatus to Psammichnites gigas arcuatus, acknowledging the distinctive 'ladder-trail' ornament found on its lower surface but also its overall similarity to Psammichnites gigas, as recognized by previous workers. Additionally we recommend applying the designation Psammichnites gigas gigas to specimens of Psammichnites gigas characterized by high convexity, a straight to sinuous axial ridge or groove, and a straight, sinuous, or curved path, and lacking a 'ladder-trail' ornament. Documenting the multiple preservational variants of Cambrian Psammichnites is important to estimate ichnodiversity levels accurately during the Cambrian explosion and to enhance the value of this ichnotaxon for stratigraphic correlation.
Summary(Plain Language Summary, not published)
This manuscript reports a new of a type of fossilized animal burrow from the Cambrian Period of Earth's history. This type of burrow has been given the Latin name Taphrhelminthopsis circularis. The report is based in part upon a visit by some of the authors to the site in Spain where this type of burrow was first documented. It is also based on a review of previously published examples. The study shows this burrow to be a variant of another named kind of fossil burrow, called Psammichnites gigas. These types of burrows are found only in Cambrian-aged rocks, and so are useful for determining the ages of rock strata. This includes strata in northwestern Canada that are being studied during GEM-GeoNorth.

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