Special Issue "Paleontology and Geo/Biological Evolution"

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A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (1 July 2012)

Special Issue Editor

Guest Editor
Prof. Dr. George D. Stanley, Jr.

Department of Geosciences, The University of Montana, 32 Campus Drive #1296, Missoula, MT 59812, USA
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Fax: +1 406 243 4028
Interests: invertebrate paleontology & paleoecology; Triassic to Jurassic reefs and corals faunas; recovery from mass extinctions; Cambrian soft-bodied lagerstatten; using fossils to reconstruct paleogeography of displaced tectonic terranes

Special Issue Information

Dear Colleagues,

Life has been an amazing phenomenon and as far as we know, it is confined to planet Earth. Paleontology and ancient life are one of the most important forces on the planet.  Our biosphere, atmosphere and lithosphere has been influenced and indeed in many respects, controlled by the evolution of life during the past 3.5 billion years. Some of these changes have been gradual while others were geologically sudden. The interactions of tectonics, oceans and climate have changed through time, dramatically affecting the Earth’s paleontological and sedimentary record and the course of biotic evolution. Biological evolution also has been affected by forces from outside the planet including interactions with extraterrestrial bodies. This special issue will examine the fossil record and geo-biological evolution, focusing on two major themes:  1) important and unique events controlling the history of life through time and 2) important geo/biological themes that weave their way through time.

Prof. Dr. George D. Stanley, Jr.
Guest Editor

Published Papers (14 papers)

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Research

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Open AccessArticle Nacre in Molluscs from the Ordovician of the Midwestern United States
Geosciences 2013, 3(1), 1-29; doi:10.3390/geosciences3010001
Received: 13 November 2012 / Revised: 24 December 2012 / Accepted: 31 December 2012 / Published: 8 January 2013
Cited by 6 | PDF Full-text (7072 KB) | HTML Full-text | XML Full-text
Abstract
Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described
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Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described herein from the Ordovician of Iowa, Indiana, and Ohio provide supporting evidence for the hypothesis that sometime between the middle Cambrian and late Ordovician, nacre originated in cephalopod, bivalve, and possibly gastropod lineages. The correlation of independent origins of fracture-resistant nacre with increasing shell-crushing abilities of predators during the Cambrian-Ordovician suggests an early pulse in the evolutionary arms race between predators and molluscan prey. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
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Open AccessArticle Oxygen-Dependent Morphogenesis of Modern Clumped Photosynthetic Mats and Implications for the Archean Stromatolite Record
Geosciences 2012, 2(4), 235-259; doi:10.3390/geosciences2040235
Received: 2 August 2012 / Accepted: 25 September 2012 / Published: 11 October 2012
Cited by 9 | PDF Full-text (3034 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Some modern filamentous oxygenic photosynthetic bacteria (cyanobacteria) form macroscopic tufts, laminated cones and ridges that are very similar to some Archean and Proterozoic stromatolites. However, it remains unclear whether microbes that constructed Archean clumps, tufts, cones and ridges also produced oxygen. Here, we
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Some modern filamentous oxygenic photosynthetic bacteria (cyanobacteria) form macroscopic tufts, laminated cones and ridges that are very similar to some Archean and Proterozoic stromatolites. However, it remains unclear whether microbes that constructed Archean clumps, tufts, cones and ridges also produced oxygen. Here, we address this question by examining the physiology of cyanobacterial clumps, aggregates ~0.5 mm in diameter that initiate the growth of modern mm- and cm-scale cones. Clumps contain more particulate organic carbon in the form of denser, bowed and bent cyanobacterial filaments, abandoned sheaths and non-cyanobacterial cells relative to the surrounding areas. Increasing concentrations of oxygen in the solution enhance the bending of filaments and the persistence of clumps by reducing the lateral migration of filaments away from clumps. Clumped mats in oxic media also release less glycolate, a soluble photorespiration product, and retain a larger pool of carbon in the mat. Clumping thus benefits filamentous mat builders whose incorporation of inorganic carbon is sensitive to oxygen. The morphogenetic sequence of mm-scale clumps, reticulate ridges and conical stromatolites from the 2.7 Ga Tumbiana Formation likely records similar O2-dependent behaviors, preserving currently the oldest morphological signature of oxygenated environments on Early Earth. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Ocean Acidification and the End-Permian Mass Extinction: To What Extent does Evidence Support Hypothesis?
Geosciences 2012, 2(4), 221-234; doi:10.3390/geosciences2040221
Received: 21 July 2012 / Revised: 16 August 2012 / Accepted: 18 September 2012 / Published: 28 September 2012
Cited by 5 | PDF Full-text (4927 KB) | HTML Full-text | XML Full-text
Abstract
Ocean acidification in modern oceans is linked to rapid increase in atmospheric CO2, raising concern about marine diversity, food security and ecosystem services. Proxy evidence for acidification during past crises may help predict future change, but three issues limit confidence of
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Ocean acidification in modern oceans is linked to rapid increase in atmospheric CO2, raising concern about marine diversity, food security and ecosystem services. Proxy evidence for acidification during past crises may help predict future change, but three issues limit confidence of comparisons between modern and ancient ocean acidification, illustrated from the end-Permian extinction, 252 million years ago: (1) problems with evidence for ocean acidification preserved in sedimentary rocks, where proposed marine dissolution surfaces may be subaerial. Sedimentary evidence that the extinction was partly due to ocean acidification is therefore inconclusive; (2) Fossils of marine animals potentially affected by ocean acidification are imperfect records of past conditions; selective extinction of hypercalcifying organisms is uncertain evidence for acidification; (3) The current high rates of acidification may not reflect past rates, which cannot be measured directly, and whose temporal resolution decreases in older rocks. Thus large increases in CO2 in the past may have occurred over a long enough time to have allowed assimilation into the oceans, and acidification may not have stressed ocean biota to the present extent. Although we acknowledge the very likely occurrence of past ocean acidification, obtaining support presents a continuing challenge for the Earth science community. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
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Open AccessArticle Homology and Potential Cellular and Molecular Mechanisms for the Development of Unique Feather Morphologies in Early Birds
Geosciences 2012, 2(3), 157-177; doi:10.3390/geosciences2030157
Received: 30 July 2012 / Revised: 30 August 2012 / Accepted: 3 September 2012 / Published: 14 September 2012
Cited by 17 | PDF Full-text (8419 KB) | HTML Full-text | XML Full-text
Abstract
At least two lineages of Mesozoic birds are known to have possessed a distinct feather morphotype for which there is no neornithine (modern) equivalent. The early stepwise evolution of apparently modern feathers occurred within Maniraptora, basal to the avian transition, with asymmetrical pennaceous
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At least two lineages of Mesozoic birds are known to have possessed a distinct feather morphotype for which there is no neornithine (modern) equivalent. The early stepwise evolution of apparently modern feathers occurred within Maniraptora, basal to the avian transition, with asymmetrical pennaceous feathers suited for flight present in the most basal recognized avian, Archaeopteryx lithographica. The number of extinct primitive feather morphotypes recognized among non-avian dinosaurs continues to increase with new discoveries; some of these resemble feathers present in basal birds. As a result, feathers between phylogenetically widely separated taxa have been described as homologous. Here we examine the extinct feather morphotypes recognized within Aves and compare these structures with those found in non-avian dinosaurs. We conclude that the “rachis dominated” tail feathers of Confuciusornis sanctus and some enantiornithines are not equivalent to the “proximally ribbon-like” pennaceous feathers of the juvenile oviraptorosaur Similicaudipteryx yixianensis. Close morphological analysis of these unusual rectrices in basal birds supports the interpretation that they are modified pennaceous feathers. Because this feather morphotype is not seen in living birds, we build on current understanding of modern feather molecular morphogenesis to suggest a hypothetical molecular developmental model for the formation of the rachis dominated feathers of extinct basal birds. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
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Open AccessArticle Bythocythere solisdeus n. sp. and Cytheropteron eleonorae n. sp. (Crustacea, Ostracoda) from the Early Pleistocene Bathyal Sediments of Cape Milazzo (NE, Sicily)
Geosciences 2012, 2(3), 147-156; doi:10.3390/geosciences2030147
Received: 21 May 2012 / Revised: 19 June 2012 / Accepted: 29 June 2012 / Published: 9 July 2012
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Abstract
Two new fossil species of Ostracoda belonging to the genus Bythocythere Sars, 1866, Bythocythere solisdeus n. sp. and to the genus Cytheropteron Sars, 1866, Cytheropteron eleonorae n. sp. are described. The specimens come from the upper silty sand layers of the Globorotalia truncatulinoides
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Two new fossil species of Ostracoda belonging to the genus Bythocythere Sars, 1866, Bythocythere solisdeus n. sp. and to the genus Cytheropteron Sars, 1866, Cytheropteron eleonorae n. sp. are described. The specimens come from the upper silty sand layers of the Globorotalia truncatulinoides excelsa Zone (“Sicilian” stage), cropping out in “Cala S. Antonino” along the western side of the Cape Milazzo Peninsula (NE Sicily). Both species belong to a typical Bathyal ostracod association characterized by very low temperatures. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere
Geosciences 2012, 2(2), 130-146; doi:10.3390/geosciences2020130
Received: 29 March 2012 / Revised: 9 May 2012 / Accepted: 22 May 2012 / Published: 31 May 2012
Cited by 10 | PDF Full-text (571 KB) | HTML Full-text | XML Full-text
Abstract
The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of
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The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon) in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire) excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Squalicorax Chips a Tooth: A Consequence of Feeding-Related Behavior from the Lowermost Navesink Formation (Late Cretaceous: Campanian-Maastrichtian) of Monmouth County, New Jersey, USA
Geosciences 2012, 2(2), 109-129; doi:10.3390/geosciences2020109
Received: 6 March 2012 / Revised: 20 April 2012 / Accepted: 23 May 2012 / Published: 30 May 2012
Cited by 3 | PDF Full-text (1347 KB) | HTML Full-text | XML Full-text
Abstract
Chipped and broken functional teeth are common in modern sharks with serrated tooth shape. Tooth damage consists of splintering, cracking, and flaking near the cusp apex where the enameloid is broken and exposes the osteodentine and orthodentine. Such damage is generally viewed as
[...] Read more.
Chipped and broken functional teeth are common in modern sharks with serrated tooth shape. Tooth damage consists of splintering, cracking, and flaking near the cusp apex where the enameloid is broken and exposes the osteodentine and orthodentine. Such damage is generally viewed as the result of forces applied during feeding as the cusp apex impacts the skeletal anatomy of prey. Damage seen in serrated functional teeth from sharks Squalicorax kaupi [1] and Squalicorax pristodontus [1] from the late Cretaceous lowermost Navesink Formation of New Jersey resembles that occurring in modern sharks and suggests similar feeding behavior. Tumbling experiments using serrated modern and fossil functional shark teeth, including those of Squalicorax, show that teeth are polished, not cracked or broken, by post-mortem abrasion in lowermost Navesink sediment. This provides further evidence that chipped and broken Squalicorax teeth are feeding-related and not taphonomic in origin. Evolution of rapid tooth replacement in large sharks such as Squalicorax ensured maximum functionality after feeding-related tooth damage occurred. Serrated teeth and rapid tooth replacement in the large sharks of the Mesozoic and Cenozoic afforded them competitive advantages that helped them to achieve their place as apex predators in today’s ocean. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Early Silurian (Aeronian) East Point Coral Patch Reefs of Anticosti Island, Eastern Canada: First Reef Recovery from the Ordovician/Silurian Mass Extinction in Eastern Laurentia
Geosciences 2012, 2(2), 64-89; doi:10.3390/geosciences2020064
Received: 5 April 2012 / Revised: 11 May 2012 / Accepted: 15 May 2012 / Published: 24 May 2012
Cited by 9 | PDF Full-text (3444 KB) | HTML Full-text | XML Full-text
Abstract
An extensive late Aeronian patch reef swarm outcrops for 60–70 km on Anticosti Island, eastern Canada, located in the inner to mid-shelf area of a prominent tropical carbonate platform of southeastern Laurentia, at 20°–25° S paleolatitude of the southern typhoon belt. This complex,
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An extensive late Aeronian patch reef swarm outcrops for 60–70 km on Anticosti Island, eastern Canada, located in the inner to mid-shelf area of a prominent tropical carbonate platform of southeastern Laurentia, at 20°–25° S paleolatitude of the southern typhoon belt. This complex, described here for the first time, includes more than 100 patch reefs, up to 60–80 m in diameter and 10 m high. Reefs are exposed three-dimensionally on present-day tidal flats, as well as inland along roads and rivers. Down the gentle 1°–2° paleoslope, the reefs grade into coral-sponge biostromes, and westerly they grade into inter-reef or deeper ‘crinoidal meadow’ facies. The reef builders were dominantly tabulate and rugose corals, with lesser stromatoporoids. Other components include crinoids, brachiopods, green algae (especially paleoporellids), and encrusting cyanobacteria: reefs display some of the earliest known symbiotic intergrowths of corals and stromatoporoids. Reefs were variably built on a base of crinoidal grainstones, meadows of baffling tabulate corals, brachiopod shells, or chlorophytes. These reefs mark an early phase of reef recovery after a prominent reef gap of 5–6 million years following the Ordovician/Silurian mass extinction events. The reefs feature a maximal diversity of calcifying cyanobacteria, corals and stromatoporoids, but low diversity of brachiopods, nautiloids and crinoids. Following the North American Stratigraphic Code, we define herein the Menier Formation, encompassing the lower two members of the existing Jupiter Formation. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Distribution and Diversity of Carboniferous and Permian Colonial Rugose Coral Faunas in Western North America: Clues for Placement of Allochthonous Terranes
Geosciences 2012, 2(2), 42-63; doi:10.3390/geosciences2020042
Received: 3 April 2012 / Revised: 25 April 2012 / Accepted: 2 May 2012 / Published: 10 May 2012
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Abstract
Colonial rugose corals are common in western cratonal North America and in some of the allochthonous terranes, now amalgamated against its western margin. Throughout the Late Paleozoic, the coral faunas in these two different settings were significantly different. Comparisons of these faunas suggest
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Colonial rugose corals are common in western cratonal North America and in some of the allochthonous terranes, now amalgamated against its western margin. Throughout the Late Paleozoic, the coral faunas in these two different settings were significantly different. Comparisons of these faunas suggest that during the Mississippian the Alexander terrane probably was southwest of Arctic Alaska and the Stikine terrane probably lay west of the southern part of the North American craton. The Cache Creek terrane lay far out in the Paleopacific Ocean. The Pennsylvanian faunas suggest that the Quesnellia and Eastern Klamath terranes were situated southwest of Arctic Alaska and the Alexander terrane was somewhat farther southwest and farther from cratonal North America. The Stikine terrane continued to be positioned west of the southern part of the North American craton. During the Early Permian, terranes with a cratonal faunal aspect may have lain 2000–3000 km west of cratonal North America and latitudinally generally southwest of their present positions. In the Middle Permian these terranes were carried southward relative to the North American craton. Simultaneously the Tethyan Realm expanded eastward. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessArticle Cenozoic Mammals and Climate Change: The Contrast between Coarse-Scale versus High-Resolution Studies Explained by Species Sorting
Geosciences 2012, 2(2), 25-41; doi:10.3390/geosciences2020025
Received: 9 March 2012 / Revised: 29 March 2012 / Accepted: 9 April 2012 / Published: 13 April 2012
Cited by 4 | PDF Full-text (1232 KB) | HTML Full-text | XML Full-text
Abstract
Many paleontologists have noticed the broadly similar patterns between the changes in Cenozoic mammalian diversity and taxonomic dominance and climate changes. Yet detailed studies of fossil population samples with fine-scale temporal resolution during episodes of climate change like the Eocene-Oligocene transition in the
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Many paleontologists have noticed the broadly similar patterns between the changes in Cenozoic mammalian diversity and taxonomic dominance and climate changes. Yet detailed studies of fossil population samples with fine-scale temporal resolution during episodes of climate change like the Eocene-Oligocene transition in the White River Group, and the late Pleistocene at Rancho La Brea tar pits, demonstrates that most fossil mammal species are static and show no significant microevolutionary response to major climate changes. This mismatch between patterns seems best explained by species sorting. As the punctuated equilibrium model demonstrated, over long time spans most fossil species are stable and do not respond to climate change. Instead, change occurs at the next hierarchical level, with species sorting adding and subtracting to the total diversity pattern revealed by coarse-scale taxon counting, apparently responding to longer-term changes in climate as revealed by proxies like the oxygen isotope record. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessCommunication The Extinction of the Conulariids
Geosciences 2012, 2(1), 1-10; doi:10.3390/geosciences2010001
Received: 22 February 2012 / Revised: 12 March 2012 / Accepted: 15 March 2012 / Published: 22 March 2012
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Abstract
Conulariids are unusual extinct metazoans most often considered to be a group of scyphozoan cnidarians or close relatives. Generally, the temporal range of conulariid fossils is perceived to be late Precambrian or Cambrian to Triassic, though a supposed Cretaceous conulariid from Peru was
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Conulariids are unusual extinct metazoans most often considered to be a group of scyphozoan cnidarians or close relatives. Generally, the temporal range of conulariid fossils is perceived to be late Precambrian or Cambrian to Triassic, though a supposed Cretaceous conulariid from Peru was published 46 years ago. A re-evaluation of this fossil indicates it is not a conulariid, but instead a pinnacean bivalve (Pinna sp.), confirming that the geologically youngest conulariids are of Late Triassic age. However, a review of the Triassic conulariid fossil record indicates it is very sparse, with only eight published records. It does not provide a reliable basis for analyzing the structure of conulariid extinction. Nevertheless, conulariid extinction still appears to have taken place very close to the end of the Triassic. The cause of conulariid extinction may have been the onset of the Mesozoic marine revolution, in which durivorous predators developed new mechanisms for preying on the epifaunal benthos, including the conulariids. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)

Review

Jump to: Research

Open AccessReview Evolution of Endemic Species, Ecological Interactions and Geographical Changes in an Insular Environment: A Case Study of Quaternary Mammals of Sicily (Italy, EU)
Geosciences 2013, 3(1), 114-139; doi:10.3390/geosciences3010114
Received: 12 December 2012 / Revised: 21 January 2013 / Accepted: 21 January 2013 / Published: 5 February 2013
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Abstract
The Quaternary mammals of Sicily are well known, and five faunal complexes have been distinguished on the basis of bioevents (extinctions and new arrivals) and evolution of endemic species. It is clear that the composition of mammal faunas is strictly related to the
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The Quaternary mammals of Sicily are well known, and five faunal complexes have been distinguished on the basis of bioevents (extinctions and new arrivals) and evolution of endemic species. It is clear that the composition of mammal faunas is strictly related to the dispersal ability of each species and to the paleogeography of the area. Until now, researches have chiefly attributed paleogeographical changes as controlling these dispersals: the sea strait between the island and the Italian peninsula has had different widths and depths over time, operating different kinds of filters on the spreading of terrestrial mammals. Moreover, Sicily and its nearby mainland underwent changes in paleogeography. Some incongruence in bioevents has been attributed to the filter operated by the marine strait, which could have acted in differential ways on large and small mammals. However, the roles of ecological interactions among vertebrate species and their control on bioevents have been greatly underestimated. In this critical review, changes in mammals’ associations are reconsidered not only in terms of biochronology and dispersal ability of taxa through the marine strait, evolution of endemic features, in addition to the paleogeography of the island, but also considering the ecological role of each species and the interactions among the species with each faunal complex. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
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Open AccessReview The Location and Styles of Ice-Free “Oases” during Neoproterozoic Glaciations with Evolutionary Implications
Geosciences 2012, 2(2), 90-108; doi:10.3390/geosciences2020090
Received: 13 March 2012 / Revised: 10 April 2012 / Accepted: 17 May 2012 / Published: 29 May 2012
Cited by 2 | PDF Full-text (1495 KB) | HTML Full-text | XML Full-text
Abstract
Evidence based on molecular clocks, together with molecular evidence/biomarkers and putative body fossils, points to major evolutionary events prior to and during the intense Cryogenian and Ediacaran glaciations. The glaciations themselves were of global extent. Sedimentological evidence, including hummocky cross-stratification (representing ice-free seas
[...] Read more.
Evidence based on molecular clocks, together with molecular evidence/biomarkers and putative body fossils, points to major evolutionary events prior to and during the intense Cryogenian and Ediacaran glaciations. The glaciations themselves were of global extent. Sedimentological evidence, including hummocky cross-stratification (representing ice-free seas affected by intra-glacial storms), dropstone textures, microbial mat-bearing ironstones, ladderback ripples, and wave ripples, militates against a “hard” Snowball Earth event. Each piece of sedimentological evidence potentially allows insight into the shape and location, with respect to the shoreline, of ice-free areas (“oases”) that may be viewed as potential refugia. The location of such oases must be seen in the context of global paleogeography, and it is emphasized that continental reconstructions at 600 Ma (about 35 millions years after the “Marinoan” ice age) are non-unique solutions. Specifically, whether continents such as greater India, Australia/East Antarctica, Kalahari, South and North China, and Siberia, were welded to a southern supercontinent or not, has implications for island speciation, faunal exchange, and the development of endemism. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)
Open AccessReview Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back?
Geosciences 2012, 2(2), 11-24; doi:10.3390/geosciences2020011
Received: 5 March 2012 / Revised: 19 March 2012 / Accepted: 30 March 2012 / Published: 12 April 2012
Cited by 10 | PDF Full-text (260 KB) | HTML Full-text | XML Full-text
Abstract
Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic–Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes.
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Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic–Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes. This review summarizes the occurrence of all Cretaceous genera. A discussion of morphological diversity demonstrates the different, though overlapping, ecological niches occupied by the different taxa, while the comparison of phylogenetic hypotheses shows the problems inherent in understanding the evolutionary relationships between Cretaceous genera. The Late Jurassic radiation indicated in the competing phylogenetic hypotheses may correlate with the opening of the Atlantic Ocean or additional dispersal routes established by the breakup of Gondwana. Inclusion of the stratigraphically oldest Platypterygius species may aid in resolving these evolutionary relationships. Full article
(This article belongs to the Special Issue Paleontology and Geo/Biological Evolution)

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