Insights into vase-shaped microfossil diversity and Neoproterozoic biostratigraphy in light of recent Brazilian discoveries

Abstract

Vase-shaped microfossils (VSMs) occur in dolostone clasts within conglomerates, breccias, and diamictites of the Neoproterozoic Urucum Formation, Jacadigo Group, southwest Brazil. Although their taphonomic history is distinct from those of other VSM assemblages, morphometric comparison of Urucum fossils with five others described previously from North America and Europe show that two of the Urucum species—the long-necked Limeta lageniformis Morais, Fairchild, and Lahr in Morais et al., 2017 and the funnel-necked Palaeoamphora urucumense Morais et al., 2017—occur in the Kwagunt and Callison Lake assemblages, as does Pakupaku kabin Riedman, Porter, and Calver, 2017 recently described from the Togari Group, Tasmania. Obelix rootsii (Cohen, Irvine, and Strauss, 2017) new combination, previously known only from the Callison Lake Formation, is documented here from the Kwagunt Formation. In addition, Trigonocyrillium horodyskii (Bloeser, 1985) and Bonniea dacruchares Porter, Meisterfeld, and Knoll, 2003, first described from the Kwagunt assemblage, have now been found in the Urucum Formation. In light of this survey, 16 of the 18 validly described VSM species are now known to occur in the Kwagunt Formation and 13 in the Callison Lake Formation, with 12 of them shared by both formations. The fact that the Urucum VSM assemblage exhibits six of seven species in common with the Kwagunt Formation—L. lageniformis, P. urucumense, Cycliocyrillium simplex Porter, Meisterfeld, and Knoll, 2003, C. torquata Porter, Meisterfeld, and Knoll, 2003, B. dacruchares Porter, Meisterfeld, and Knoll, 2003, and T. horodyskii (Bloeser, 1985)—and all but the last of these in common with the Callison Lake Formation supports correlation of these three assemblages and indicates that the source of the fossiliferous clasts within the Urucum Formation may well have been a now-vanished late Tonian carbonate platform.UUID: http://zoobank.org/ac0becd6-29ff-4491-80fa-0291730fba65

Free and kerogen‐bound biomarkers from late Tonian sedimentary rocks record abundant eukaryotes in mid‐Neoproterozoic marine communities

“…Ciliates are a class of heterotrophic eukaryotic protists that are phylogenetically distinct from the abundant testate ameba (preserved as vase‐shaped microfossils; VSMs) found within the Chuar Group and other late Tonian paleoenvironments (Porter & Knoll, ; Porter et al, ; Strauss, Rooney, Macdonald, Brandon, & Knoll, ). It should be noted that in relation to the diverse distribution of VSM species recovered from the Chuar Group (which is the only Tonian environment where the majority of known VSM species ( n = 8) have been recovered), the Visingsö Group hosts less abundant VSM occurrences (Morais et al, ; Riedman et al, ). The lower VSM microfossil abundance and diversity, together with the substantially lower gammacerane content and lower S/H ratios, suggests that eukaryotic heterotrophy was possibly suppressed in the Visingsö paleoenvironments compared with the Chuar Group.…”

An emerging paradigm for the origin and evolution of shelled amoebae, integrating advances from molecular phylogenetics, morphology and paleontology

“…(33,34,35) The Tonian period also received new descriptions from different locations around the globe. (36,37,38,39,40) The additional findings led to the current taxonomic status of the Neoproterozoic VSMs, which have a total of 14 described genera. At least five taxa have been confidently described for 8 locations distributed around the globe.…”

“…This solidity of the data has even allowed a current discussion about using Cycliocyrillium simplex as a fossil index of the Tonian period. (40) The findings in the fossil record point to a solid biological affinity with the Arcellinida. The Arcellinida in turn received phylogenomic treatment and their main phylogenetic structures were unveiled.…”

“…VSMs occur in fossiliferous layers that are very difficult to interpret. In addition to intrinsic antiquity, it is still not very well established what exactly were the taphonomic conditions to which the different microfossils were subjected, as discussed above and reviewed by Morais et al (40) In the first indepth study of the VSMs from the Chuar group, there is a discussion as to whether the environment was a shallow area of the sea, or it could be an estuarine region with a strong inhuence of fresh water from river discharge. (28) However, the current consensus among geologists and paleobiologists is that all fossil layers where VSMs were found are testimonies to marine environments.…”

Evolution: Ancient Fossilized Amoebae Find Their Home in the Tree

“…Pie charts at each node indicate probabilities of test composition: organic-walled (orange), calcareous (white) and agglutinated with foreign particles (purple). Age constraints for A and B from [11,18,19]; for D and E from [11,18], and for C and G from [8][9][10]. There are no direct age constraints on F. Specimens in A, B, and F are from the Urucum Formation of Brazil [6] (images courtesy of Luana Morais), and C-E, G are from the Kwagunt Formation, Chuar Group, Grand Canyon, Arizona [5].…”