More Like this

1. Low drilling percentage in Norian benthic assemblages from the Southern Italian Alps and the role of specialized durophages during the Late Triassic

   https://doi.org/https://doi.org/10.1016/j.palaeo.2018.06.034  

   Tackett, LS (January 2019, Palaeogeography, palaeoclimatology, palaeoecology)

   Drillholes represent one of the clearest lines of evidence for predation of benthic invertebrates in the fossil record and are frequently used as a primary proxy for predation intensity in the fossil record. Drillholes are abundant in the late Cretaceous and Cenozoic, but their occurrence is patchy in older deposits of the Mesozoic. The inconsistent record of drillholes in pre-Cretaceous deposits of Mesozoic age are problematic for interpretations of predation-prey dynamics and adaptive radiations, and the role of taphonomy or diagenesis have not been resolved. Here we present drilling percentages for assemblages of well-preserved shelly benthic invertebrates (mainly comprised of bivalves and rare gastropods) from the upper Norian (Upper Triassic) in northern Italy in order to compare these values with reported drilling percentages from the Carnian San Cassiano Formation, a rare Triassic sedimentary unit that has yielded many drilled fossils. The Norian fossil deposits reported here are comparable to those of the San Cassiano in terms of depositional environment, preservation, and region, and can be reasonably compared to the drilling percentage of fossils from the San Cassiano. The sampled deposits are collected from marly limestone horizons in the Argillite di Riva di Solto in the Southern Italian Alps, deposited in the Lombardian Basin, and which are interbedded with shale units containing well-preserved fish and arthropod fossils, enabling a correlation between paleoecological structure of the shelly benthos and the demersal-pelagic predator diversity. Over four hundred bivalve fossils yielded a drilling percentage of 0.24% (1/406), which is typical for fossil assemblages of this age, but the single occurrence of a drillhole in this study is in marked contrast to the many drilled specimens reported from the San Cassiano Formation deposit in Italy. The drilled specimen (with complete drillhole) was an infaunal bivalve and no incomplete drillholes were observed in other specimens. Thus, drilling percentages for the Triassic are consistently low, but present, suggesting that drilling predation was an ecologically minimal influence to benthic communities and unlikely to have driven the significant ecological changes observed in benthic communities during the Late Triassic. Although drilling predation occurred during the Late Triassic, we present an updated database of specialized durophagous predators (including fishes, sharks, and reptiles) that are likely to have been more ecologically influential on benthic communities during the Norian Stage, fishes in particular. 

   more » « less
2. Fossil eggshell diversity of the Mussentuchit Member, Cedar Mountain Formation, Utah

   https://doi.org/10.1371/journal.pone.0314689  

   Hedge, Joshua; Tucker, Ryan T; Makovicky, Peter J; Zanno, Lindsay E (February 2025, PLOS ONE)

   Claessens, Leon (Ed.)

   The first fossil eggshell from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation was described over fifty years ago. In the half-century since, oodiversity of this rock unit has been limited to a single, taxonomically unstable ootaxon, currently formulated asMacroelongatoolithus carlylei. Recently, there has been a renewed effort to recover and describe the macrofauna of the Mussentuchit; however, these advances are limited to the body fossil record. Here, we examine the range of eggshells present in the Mussentuchit Member and assess the preserved biodiversity they represent. Gross morphological and microstructural inspection reveals a greater diversity of eggshells than previously described. We identify six ootaxa: three Elongatoolithidae oogenera (Macroelongatoolithus,Undulatoolithus,Continuoolithus), eggs laid by oviraptorosaur dinosaurs; two oospecies ofSpheroolithuslaid by ornithopod dinosaurs; andMycomorphoolithus kohringi, laid by a crocodylomorph. The diversity of Elongatoolithidae in the Mussentuchit requires a co-occurrence of at least three putative oviraptorosaurs, the oldest such phenomenon in North America. The occurrence of the crocodylomorph oogenusMycomorphoolithusis the first recognized occurrence outside of Europe, and the youngest yet documented. This new ooassemblage is more representative of the known paleobiodiversity of Cenomanian-age strata of Western North America and complements the body fossil record in improving our understanding of this crucial—yet poorly documented—timeslice within the broader evolution of the Cretaceous Western Interior Basin. 

   more » « less
3. Tectonic influence on Cenozoic mammal richness and sedimentation history of the Basin and Range, western North America

   https://doi.org/10.1126/sciadv.abh4470  

   Loughney, Katharine M.; Badgley, Catherine; Bahadori, Alireza; Holt, William E.; Rasbury, E. Troy (November 2021, Science Advances)

   Tectonic activity can drive speciation and sedimentation, potentially causing the fossil and rock records to share common patterns through time. The Basin and Range of western North America arose through widespread extension and collapse of topographic highlands in the Miocene, creating numerous basins with rich mammalian fossil records. We analyzed patterns of mammalian species richness from 36 to 0 million years ago in relation to the history of sediment accumulation to test whether intervals of high species richness corresponded with elevated sediment accumulation and fossil burial in response to tectonic deformation. We found that the sedimentary record of the Basin and Range tracks the tectonic evolution of landscapes, whereas species-richness trends reflect actual increased richness in the Miocene rather than increased fossil burial. The sedimentary record of the region broadly determines the preservation of the fossil record but does not drive the Miocene peak in mammalian species richness. 

   more » « less
4. Calibrating the Russøya excursion in Svalbard, Norway, and implications for Neoproterozoic chronology

   https://doi.org/10.1130/G49593.1  

   Millikin, Alexie E.G.; Strauss, Justin V.; Halverson, Galen P.; Bergmann, Kristin D.; Tosca, Nicholas J.; Rooney, Alan D. (February 2022, Geology)

   Abstract The Tonian–Ediacaran Hecla Hoek succession of Svalbard, Norway, represents one of the most complete and well-preserved Neoproterozoic sedimentary successions worldwide. With diverse fossil assemblages, an extensive carbonate δ13C record, and sedimentary evidence for two distinct Cryogenian glaciations, this succession will continue to yield insights into the Neoproterozoic Earth system; however, at present there are no direct radiometric age constraints for these strata. We present two new Re-Os ages and initial Os isotope data that constrain the timing of Neoproterozoic glaciation in Svalbard, providing further support for two globally synchronous Cryogenian glaciations and insight into pre- and post-snowball global weathering conditions. An age from the Russøya Member (Elbobreen Formation) facilitates correlation of the negative carbon isotope excursion recorded therein with the pre-glacial “Islay” excursion of the Callison Lake Formation of northwestern Canada and the Didikama and Matheos Formations of Ethiopia. We propose that this globally synchronous ca. 735 Ma carbon isotope excursion be referred to as the Russøya excursion with northeastern Svalbard as the type locality. This new age provides an opportunity to construct a time-calibrated geological framework in Svalbard to assess connections between biogeochemical cycling, evolutionary innovations within the eukaryotes, and the most extreme climatic changes in Earth history. 

   more » « less
5. Spatiotemporal variability of the late Paleozoic glacial-to-postglacial transition across eastern Paraná Basin, Brazil

   https://doi.org/10.1016/j.sedgeo.2023.106420  

   Mottin, T.E.; Vesely, F.F.; Iannuzzi, R.; Griffis, N.P.; Montañez, I.P. (July 2023, Sedimentary Geology)

   The late Paleozoic glacial-to-postglacial turnover evolved complexly across Gondwana. Successions bearing volcaniclastic material that can be radiometrically dated provide crucial information about the timing of those climate events. The southernmost part of the Paraná Basin, for instance, has a high-precision geochronological framework. The eastern sector of this basin (Paraná State and north of Santa Catarina State), however, lacks radiometric ages, but conversely, has a more complete stratigraphic record, and paleontological information still poorly explored for the purpose of biostratigraphic correlation. This work examines the glacial-to-postglacial interval in the Paraná State, represented by the upper Itararé Group (Taciba Formation; glacial) and lower–middle Rio Bonito Formation (postglacial). Sedimentological, paleontological and geochemical data from outcrops, cores and well logs were used to decipher the timing, paleoclimatic and paleogeographic scenarios of this transition. The examined succession comprises four stacked units (U1 to U4, from older to younger). Diamictite-dominated units (U1 and U3), here interpreted as consecutive glaciation–deglaciation events, are separated by non-glacial, continental to shallow marine deposits, commonly bearing fossil plants and coal seams (U2). An important transgression followed the first deglaciation,which is equivalent to the “Eurydesma transgression”, basedonthepresence of marine invertebrates of the homonymous fauna in the Passinho Shale. U2 holds elements of two different floras, i.e., Phyllotheca–Gangamopteris (P–G), predating the “Eurydesma transgression”, and Glossopteris Brasilodendron (G–B), above the transgression. Therefore, U2 is interpreted as an interglacial interval, once it records a climate improving before the last glacial episode of U3, which is further supported by relatively high values of the Chemical Index of Alteration (CIA). Deposits of U3, associated with a decrease in the value of the CIA, are unconformably overlain by U4. The occurrence of coal-bearing postglacial facies (U4) associated with the G–B Flora, coincides with an increase in the CIA values. Sediment transport was toward the SWin all units and in the same direction it is observed an overall thinning of U1 and U3 and thickening of U2. The interglacial P–G Flora of the study area correlates with postglacial southernmost floras, based on U–Pb CA-TIMS Asselian ages of tonsteins. Correlation of the Eurydesma fauna-containing Passinho Shale with equivalent successions with high-precision age control in southern Africa, allowed us to position both deglaciations of the Taciba Formation (U1 and U3) in the Asselian. These findings suggest that U1 and U3 record two early Permian glacial episodes, with the younger one (U3) disappearing southward. Accordingly, our results indicate that the glacial-to-postglacial turnoverwas diachronous along the eastern belt of the Paraná Basin, being progressively older southward, considering that interglacial fossil plant assemblages in the eastern margin correspond in time to postglacial assemblages farther south. 

   more » « less