The earliest paleolimulid and its attributed ichnofossils from the Lower Mississippian (Tournaisian) Horton Bluff Formation of Blue Beach, Nova Scotia, Canada
Lerner, Allan J; Lucas, Spencer G.; Mansky, Chris F.
published: May 1, 2016
ArtNo. ESP155028002004, Price: 29.00 €
We document two specimens that are assigned to Paleolimulus woodae n. sp. from the Lower Mississippian Horton Bluff Formation of Blue Beach, Nova Scotia, Canada. Specific characters of this Paleolimulus include posteromarginal facets that each extend between the genal area and a triangular-shaped termination, free lobe pleurae each with the posterior margin developed into a later- ally directed distal spine, and a thoracetron axial column with three prominent rings at the anterior and a weakly divided posterior. These are the first xiphosurid fossils known from the Tournaisian of North America and they come from a poorly-sampled interval known as Romer's gap. This is the earliest record of the suborder Limulina, the family Paleolimulidae and the genus Paleolimulus. Paleolimulus is thus extended downward from the Middle Pennsylvanian (Desmoinesian) deposits of Mazon Creek, Illinois. Paleolimulus is shown to have had a biostratigraphic range (Tournaisian – Leonardian) that essentially spanned the entire Carboniferous and Early Permian. We also document from the Horton Bluff Formation an ichnoassemblage containing Selenichnites cf.rossendalensis and Protolimulus cf.eriensis. This ichnoassemblage was likely produced by Paleolimulus woodae individuals of various ontogenetic stages in a nearshore, marginal marine setting. The morphological variation within this ichnoassemblage suggests that a preservational continuum exists withSelenichnites andProtolimulusas end members along a taphoseries. Protolimulus is likely the senior synonym of Selenichnites, but is in need of review.