Scale microfossils from the mid-Neoproterozoic Fifteenmile Group, Yukon Territory

Abstract

Microscopic phosphatic scales are found in limestones and cherts from the 812–717 million year old Fifteenmile Group of the Yukon Territory. These enigmatic microfossils, which to date have not been identified in any other locality, display a diversity of intricate morphologies. Here we describe six new genera containing 17 new species of scale microfossils obtained from macerated limestone. We also revise existing taxa described originally from chert thin sections and now additionally freed from limestone by acid dissolution. New taxa described here are:Archaeoxybaphon serratacapacisn. sp.,Archeoxybaphon serratapusillan. sp.,Paleoscutula inornatan. gen. n. sp.,Paleoscutula serratan. gen. n. sp.,Paleoscutula convocationisn. gen n. sp.,Hexacatillus allmoniin. gen. n. sp.,Hexacatillus retetantillusn. sp.,Quadrireticulum allisoniaen. gen. n. sp.,Quadrireticulum palmaspinosumn. gen. n. sp.,Circidentatus pistricisn. gen. n. sp.,Circidentatus variodentatusn. gen. n. sp.,Ospercapatera awramikiin. gen. n. sp.,Circitorquis soccusn. gen. n. sp.,Paleohexadictyon alexandraen. sp.,Paleomegasquama arctoan. sp.,Petasisquama petasusn. sp., andThorakidictyon circireticulumn. gen. n. sp. Taxa described or amended here areCharacodictyon skolopiumAllison and Hilgert, 1986,Paleohexadictyon myriotrematumAllison and Hilgert, 1986,Archeoxybaphon polykeramoides(Allison and Hilgert, 1986) emend.,Paleohexadictyon litosum(Allison and Hilgert, 1986) emend., andThorakidictyon myriocanthum(Allison and Hilgert, 1986) n. comb. Many eukaryotic clades include species with surficial scales but none provides a close morphological analog to the Fifteenmile scales. Nonetheless, comparative and functional morphology suggest that the diversification of heavily armored and morphologically complex cell-coverings records a changing ecological landscape in Neoproterozoic seas.