Global Fossil Record Research Articles

A silicified Early Triassic marine assemblage from Svalbard

Understanding how the marine biosphere recovered from the late Permian mass extinction event is a major evolutionary question. The quality of the global fossil record of this interval is, however, somewhat poor due to preservational, collection and sampling biases. Here we report a new earliest Induan (Hindeodus parvus Zone) marine assemblage from the Deltadalen Member of the Vikinghøgda Formation, central Spitsbergen, which fills a critical gap in knowledge. The fully silicified fossils comprise the oldest silicified assemblage known from the Triassic and provide critical new systematic data. For its age, the assemblage is exceptionally diverse with 14 species of bivalves and gastropods, as well as conodonts and ammonoids. Four new bivalve species (Austrotindaria antiqua, A. svalbardensis, Nucinella taylori and N. nakremi) and one new gastropod species (Glabrocingulum parvum) are described, and five families are recorded in the Induan for the first time. Some of the common and globally widespread Early Triassic taxa, such as Unionites, are also present, and their exceptional preservation reveals key morphological characters that are documented for the first time. Taxonomic and ecological revisions based on these new data suggest that shallow-infaunal deposit-feeders were a dominant component of pre-Spathian benthic communities. The gastropods and bivalves all possessed a planktotrophic larval stage, which may have been a particular advantage in the wake of the late Permian mass extinction.http://zoobank.org/urn:lsid:zoobank.org:pub:3EBCAEF3-27C2-4216-9F18-89F195FA534F

Sustained Mesozoic–Cenozoic diversification of marine Metazoa: A consistent signal from the fossil record

Research Article| November 01, 2015 Sustained Mesozoic–Cenozoic diversification of marine Metazoa: A consistent signal from the fossil record Andrew M. Bush; Andrew M. Bush 1Department of Ecology and Evolutionary Biology and Center for Integrative Geosciences, University of Connecticut, 75 North Eagleville Road, Storrs, Connecticut 06269-3043, USA Search for other works by this author on: GSW Google Scholar Richard K. Bambach Richard K. Bambach 2Department of Paleobiology, MRC-121, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20013-7012, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Andrew M. Bush 1Department of Ecology and Evolutionary Biology and Center for Integrative Geosciences, University of Connecticut, 75 North Eagleville Road, Storrs, Connecticut 06269-3043, USA Richard K. Bambach 2Department of Paleobiology, MRC-121, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20013-7012, USA Publisher: Geological Society of America Received: 16 Jul 2015 Revision Received: 02 Sep 2015 Accepted: 07 Sep 2015 First Online: 09 Mar 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (11): 979–982. https://doi.org/10.1130/G37162.1 Article history Received: 16 Jul 2015 Revision Received: 02 Sep 2015 Accepted: 07 Sep 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Andrew M. Bush, Richard K. Bambach; Sustained Mesozoic–Cenozoic diversification of marine Metazoa: A consistent signal from the fossil record. Geology 2015;; 43 (11): 979–982. doi: https://doi.org/10.1130/G37162.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Paleobiological data provide a key historical record of global biodiversity dynamics, but their interpretation is controversial due to geological and sampling biases. Raw data suggest that marine metazoans diversified dramatically during the late Mesozoic and Cenozoic, whereas bias-corrected analyses based on occurrence-level data in the Paleobiology Database (PBDB) have indicated much less Cenozoic diversification. These standardized analyses are cited as evidence that biases strongly conceal underlying patterns in the global fossil record. However, we show that marine diversity did increase substantially and continuously from the Jurassic to the Neogene, even after correcting for biases in PBDB data. Previous standardized analyses did not capture this diversification in full because they were based on incomplete data. In the Cenozoic, observed richness rose to twice the Paleozoic average, which is within the range of values seen in analyses of raw data, suggesting that even the raw global marine fossil record preserves first-order signals of diversity history. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Petreşti-Arini – An important but ephemeral Upper Cretaceous continental vertebrate site in the southwestern Transylvanian Basin, Romania

The Transylvanian region of Romania preserves some of the most unusual and iconic dinosaurs in the global fossil record, including dwarfed herbivores and aberrant carnivores that lived during the very latest Cretaceous (Maastrichtian) in an ancient island ecosystem (the Haţeg Island). A series of artificial outcrops recently exposed during a hydroelectric project, the Petreşti-Arini section near Sebeş in the Transylvanian Basin, records a 400+ meter sequence documenting the transition from fully marine to terrestrial environments during the Campanian–Maastrichtian. Calcareous nannofossil biostratigraphy indicates that the lower marine beds in this section, part of the uppermost Bozeş Formation, can be assigned to the CC22 biozone, corresponding to the lower–mid upper Campanian. These beds smoothly transition, via a brackish-water unit, into the fully continental Maastrichtian Sebeş Formation. Dinosaur and pterosaur fossils from the uppermost Bozeş Formation can be assigned a late Campanian age making them the oldest well-dated terrestrial fossils from the Haţeg Island, and indicating that the classic Haţeg dinosaur fauna was becoming established by this time, coincident with the first emergence of widespread land areas. Vertebrate fossils occur throughout the overlying Sebeş Formation at the site and are dominated by the small-bodied herbivorous dinosaur Zalmoxes. The dominance of Zalmoxes, and the absence of many taxa commonly seen elsewhere in Maastrichtian sites in Romania, suggests the possibility that either the Petreşti-Arini section preserves a somewhat unusual near-shore environment, or the earliest Haţeg Island dinosaur communities were structured differently from the more diverse communities later in the Maastrichtian. Alternatively, due to the limited sample size available from the studied succession, it is also conceivable that sampling biases give an incomplete portrayal of the Petreşti-Arini local fauna. Support for any one of these alternative hypotheses requires further data from Petreşti-Arini as well as from the larger Transylvania area.

The Osteology of Balaur bondoc, an Island-Dwelling Dromaeosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Romania

The Haţeg Island fauna of the terminal Late Cretaceous (ca. 71–65 million years ago) of Romania is one of the most unusual dinosaur assemblages in the global fossil record. It has long been recognized that many herbivorous dinosaurs from the Haţeg fauna were dwarfed, morphologically aberrant, and/or primitive relative to mainland contemporaries, and these taxa are often considered examples of the so-called island effect: the evolutionary phenomenon by which island-dwelling species are often dwarfed and anatomically modified. Very little, however, is known about the carnivorous dinosaurs that inhabited Haţeg Island, and it is unclear whether they were also dwarfed, aberrant, or primitive. In 2009, the discovery of the first substantially complete theropod from the Late Cretaceous of Europe, the holotype of the Romanian dromaeosaurid Balaur bondoc, provided the first clear glimpse at an island-dwelling carnivorous dinosaur. Here we describe and figure this remarkably preserved skeleton in detail. We provide detailed descriptions and photographs of individual bones, and make extensive comparisons with other dromaeosaurids (and other derived coelurosaurian theropods).This monographic description provides further evidence that Balaur is an unusual derived dromaeosaurid, closely related to Velociraptor, with a remarkably modified hand and foot skeleton, including a stocky and heavily fused distal hind limb, a double set of hyperextensible pedal claws, and a fused and atrophied hand, which are otherwise unknown among derived coelurosaurian theropods. We present an updated diagnosis of Balaur based on additional preparation of the holotype, comparisons with other dromaeosaurids, and careful consideration of postmortem crushing. Histological techniques demonstrate that both the holotype and a referred specimen of Balaur, which is approximately 50% larger than the holotype and from a separate locality, belong to mature individuals. Therefore, we remove the referred specimen from Balaur bondoc and conservatively consider it Balaur sp. We present an updated assessment of the phylogenetic relationships of Balaur based on a comprehensive new coelurosaurian cladistic dataset, which corroborates the close relationship between Balaur, Velociraptor, Deinonychus, Adasaurus, and Saurornitholestes. We review the fossil record of European Late Cretaceous theropods and show that other specimens from the Late Cretaceous of Romania (including the holotype of Elopteryx), France, and Hungary either do not belong to Balaur (due to the lack of Balaur autapomorphies) or cannot be compared to Balaur because of a lack of overlapping material. Finally, we discuss the biogeographic history of European terminal Cretaceous dinosaur faunas and comment on the extreme morphological specializations of Balaur. We conclude that the phylogenetic position of Balaur, a derived dromaeosaurid closely related to Late Cretaceous Laurasian taxa, is inconsistent with previous hypotheses of long-term geographic endemicity of the Romanian island faunas, but argue that the aberrant Bauplan of Balaur is similar to that seen in some living and recently extinct mammals and thus likely due to the “island effect.”

Saurichthys and other fossil fishes from the late Smithian (Early Triassic) of Bear Lake County (Idaho, USA), with a discussion of saurichthyid palaeogeography and evolution

A new marine fish assemblage from the late Smithian (Olenekian, Early Triassic) Anasibirites beds of the Thaynes Formation collected near Georgetown (Bear Lake County, south-east Idaho, USA) comprises actinopterygians (Saurichthys cf. elongatus, Actinopterygii indet.), sarcopterygians (Actinistia indet.), and possibly chondrichthyans. We review the global fossil record of the Triassic lower actinopterygian Saurichthys, which is used herein for a case study of trends in morphological adaptations as well as variations in palaeogeographic distribution and diversity dynamics of Early Mesozoic fishes. In the Early Triassic, Saurichthys already occupied a top position in marine food webs, with some species achieving body lengths of up to 1.5 m. Distribution of morphological characters in Saurichthys during the Triassic suggests trends towards a reduction in squamation, stiffening of the fins and axial skeleton, shortening of the postorbital portion of the cranium, and reduction in the number of dermal skull bones. The postcranial adaptations in particular helped to improve the fast-start ability of these ambush predatory fishes. The palaeogeographic range of Saurichthys changed from a virtually global distribution in the Early Triassic (indicating rapid dispersal within marine and freshwater ecosystems after the end-Permian mass extinction) to an occurrence mainly restricted to the north-western Tethys in the Late Triassic, and also towards increasing rarity within continental deposits. Modifications in the palaeogeographic distribution were accompanied by successive loss in global species richness and were possibly related to intra-Triassic extinction events, environmental alterations and/or competition.

A 56 million year rhythm in North American sedimentation during the Phanerozoic

Long-term (>10Myr) fluctuations in climate, sea-level and sedimentation have been documented in the stratigraphic record, but the lack of well-constrained data series has made it difficult to rigorously evaluate cyclic (periodic or quasi-periodic) changes at this scale. Here we utilize a new compilation of the coverage area of sedimentary rocks in North America to investigate the dominant modes (“orders”) of stratigraphic variability, and to evaluate potential long-period cyclic changes in sedimentation on the continent during the Phanerozoic. Our analysis resolves two principal temporal modes of variability: (1) a strongly sinusoidal mode with a periodicity of 56Myr+/−3Myr, and (2) a longer-term Phanerozoic mode (the “M-curve”, linked to the Wilson cycle), which is indistinguishable from a stochastic autoregressive process. The newly identified 56Myr cycle in sedimentation delineates most of the cratonic sequences that have previously been identified qualitatively in North America, but here we propose a quantitative redefinition that includes nine distinct units and two mega-sequences. The timing of the 56Myr beat in sedimentation is consistent with an orogenic oscillator source or an oscillatory dynamic in mantle convection, and its tempo is statistically similar to a known rhythm in number of marine animal genera in the global fossil record. Thus, the identification of a significant periodic signal in the sedimentary record of North America provides new evidence for an important tectonic- and/or mantle-scale cyclic process that links both large-scale biological evolution and physical environmental change.

Patterns of mammalian evolution across the Cretaceous-Tertiary boundary

The available fossil record of mammalian evolution across the Cretaceous-Tertiary (K-T) boundary is highly biased biogeographically by the results of detailed sampling of Late Cretaceous and Paleocene local faunas in what is now the Western Interior of the North American continent. In this area, which was then a coastal lowland, the mass extinction marking the K-T boundary resulted in extinction of many mammalian lineages. Analysis of the phylogenetic relationships of the mammals comprising North American early Paleocene faunas demonstrates that recovery of taxonomic diversity after the K-T boundary was the product of two processes: 1) evolutionary radiation of some locally surviving stocks and 2) immigration of mammals from other, as yet unsampled areas. Limited evidence suggests that dispersal of the groups that dominate these earliest Paleocene faunas had begun in the latest Cretaceous. Some mammalian local faunas of Late Cretaceous or early Paleocene age are known from other continents, but none of these provide as complete a fossil record of mammalian evolution during this interval. In spite of these limitations, analysis of the available, global fossil record reveals significant biogeographic provinciality of mammalian faunas and some similarities in their patterns of extinction and recovery of taxonomic diversity during the transition from the Cretaceous into the Tertiary.

Correlates of body mass evolution in primates

Body mass is undoubtedly central to the overall adaptive profile of any organism. Despite this, very little is known of what forces drive evolutionary changes in body mass and, consequently, shape patterns of body mass distribution exhibited by animal radiations. The search for factors that may influence evolutionary processes in general frequently focuses on environmental parameters such as climate change or interspecific competition. With respect to body mass, there is also the suggestion that evolutionary lineages may follow an inherent trend toward increased body mass, known as Cope's rule. The present paper investigates whether overall directional trends of body mass change, or correlations between patterns of body mass evolution and environmental factors have influenced the evolution of body mass in plesiadapiforms and primates. Analyses of the global fossil record of plesiadapiforms and primates suggest that the former did indeed follow an overall trend toward increased body mass compatible with the predictions of Cope's rule. In contrast, neither primates as a whole, nor a number of individual primate radiations (Adapiformes, Omomyiformes, and Anthropoidea), show any indication of overall directional patterns of body mass change. No correlations of primate body mass change with either the latitudinal distribution of fossil species, or with estimates of global temperature trends, were found. There is evidence, however, that direct competition between omomyiforms and adapiforms (the two main primate radiations known from the Paleogene) influenced processes of body mass evolution in omomyiforms.

Biogeographic and evolutionary patterns of continental margin benthic foraminifera

Several very large, taxonomically standardized data sets have been compiled and utilized to investigate biogeographic and evolutionary patterns of continental margin benthic foraminifera. Mean partial species durations for 87 frequently occurring and 180 rarely occurring species on the Atlantic continental margin of North America are the same, namely 21 m.y. The global fossil record of these species indicates no center or centers of origin and indicates very rapid dispersal. The Miocene had the greatest number of first occurrences with 46%, followed by the Pleistocene, Pliocene and Oligocene with approximately 13% each. The remaining 14% first occur in the Eocene, Paleocene, and Cretaceous. Species with a wide geographic distribution often exhibit longer species durations than those with narrow geographic ranges. The vast majority of endemic species (150 of 175) occur rarely and have no fossil record.