Landlubbers to leviathans: evolution of swimming in mosasaurine mosasaurs

Paleobiology ◽  
2011 ◽  
Vol 37 (3) ◽  
pp. 445-469 ◽  
Author(s):  
Johan Lindgren ◽  
Michael J. Polcyn ◽  
Bruce A. Young
Keyword(s):  
Stable Isotope ◽  
Aspect Ratio ◽  
Fossil Record ◽  
Phenotypic Expression ◽  
Complete Sequence ◽  
Foraging Habitat ◽  
Evolutionary Patterns ◽  
Evolutionary Transitions ◽  
Single Animal ◽  
Caudal Segment

Incremental stages of major evolutionary transitions within a single animal lineage are rarely observed in the fossil record. However, the extraordinarily complete sequence of well preserved material spanning the 27-Myr existence of the marine squamate subfamily Mosasaurinae provides a unique exception. By comparison with extant and extinct analogs, the tail morphology of four mosasaurine genera is examined, revealing a pattern of evolution that begins with the generalized varanoid anatomy and culminates in a high-aspect-ratio fin, similar to that of sharks. However, unlike the epicercal caudal fluke of selachians in which the tail bends dorsocaudally, derived mosasaurs develop a hypocercal tail with a ventrocaudal bend. Progressive caudal regionalization, reduced intervertebral mobility, increased tail depth due to a marked downturn of the posterior caudal segment, and the development of finlike paired appendages reveal a pattern of adaptation toward an optimized marine existence. This change in morphology reflects a transition from anguilliform or sub-carangiform locomotion to carangiform locomotion, and indicates a progressive shift from nearshore dwellers to pelagic cruisers—a change in foraging habitat independently corroborated by paleobiogeographic, stable isotope, osteohistological, and paleopathological data. Evolutionary patterns similar to those observed in mosasaurine mosasaurs are seen in other secondarily aquatically adapted amniotes, notably metriorhynchid crocodyliforms, cetaceans, and ichthyosaurs, and may be explained by developmental modularity governing the observed phenotypic expression.

Evolutionary Patterns Within Fossil Lineages: Model-Based Assessment of Modes, Rates, Punctuations and Process

2008 ◽  
Vol 14 ◽  
pp. 117-131 ◽  
Author(s):  
Gene Hunt
Keyword(s):  
Fossil Record ◽  
Morphological Evolution ◽  
Phenotypic Change ◽  
Relative Importance ◽  
Phenotypic Evolution ◽  
Evolutionary Patterns ◽  
Evolutionary Transitions ◽  
Direct View ◽  
Great Progress ◽  
Evolutionary Mode

Patterns of phenotypic change documented in the fossil record offer the only direct view scientists have of evolutionary transitions arrayed over significant durations of time. What lessons should be drawn from these data, however, has proven to be rather contentious. Although we as paleontologists have made great progress in documenting the geological record of phenotypic evolution with greater thoroughness and sophistication, these successes have been limited by the use of verbal models of how phenotypes change. Descriptive terms such as “gradual” have been understood differently by different authors, and this has led to completely incompatible summary statements about the fossil record of morphological evolution. Here I argue that the solution to this ambiguity lies in insisting that different evolutionary interpretations be represented as explicit, statistical models of evolution. With such an approach, the powerful machinery of likelihood-based inference can be help resolve long-standing paleontological questions.Here I first review this approach and some aspects of its implementation. Then, I show how this approach leads to new traction on important issues in evolutionary paleobiology, including: understanding modes of evolution and determining their relative importance, separating evolutionary mode from tempo, assessing the evidence for hypotheses of punctuated change, and detecting adaptive evolution in the fossil record.

scholarly journals Understanding plant reproductive diversity

2010 ◽  
Vol 365 (1537) ◽  
pp. 99-109 ◽  
Author(s):  
Spencer C. H. Barrett
Keyword(s):  
Reproductive Biology ◽  
Flowering Plants ◽  
Future Research ◽  
Wind Pollination ◽  
Evolutionary Patterns ◽  
Evolutionary Transitions ◽  
Floral Diversity ◽  
Self Fertilization ◽  
Personal Reflections ◽  
Animal Pollination

Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology.

Evolutionary Patterns in the History of Permo-Triassic and Cenozoic Synapsid Predators

2002 ◽  
Vol 8 ◽  
pp. 267-288 ◽  
Author(s):  
Blaire Van Valkenburgh ◽  
Ian Jenkins
Keyword(s):  
Fossil Record ◽  
Late Carboniferous ◽  
Second Phase ◽  
Evolutionary Patterns ◽  
Large Size ◽  
Jaw Mechanics ◽  
History Of ◽  
Trends Over Time ◽  
Energetic Constraints ◽  
Over Time

Synapsids include modern mammals and their fossil ancestors, the non-mammalian synapsids, or ‘mammal-like reptiles' of old classifications. The synapsid fossil record extends from the Late Carboniferous to the present, a span of nearly 300 million years. However, it can be broken into two distinct phases of diversification, separated by about 150 million years. The first phase extends from the Late Carboniferous to the mid-Triassic, includes the first large land predators on Earth, and is almost entirely non-mammalian. The second phase begins about 65 million years ago after the demise of the dinosaurs, includes only mammals, and extends to the present. In this overview of synapsid predators, we emphasize terrestrial species of large size, and their adaptations for killing and feeding, rather than locomotion. Despite fundamental differences in jaw mechanics and tooth morphology, there are significant parallels in the non-mammalian and mammalian radiations of synapsid predators. Both groups evolve sabertooth forms more than once, and both evolve short-snouted, powerful biting forms. In addition, both the Late Carboniferous—Triassic and Cenozoic phases are characterized by repeated patterns of clade replacement, in which one or a few clades evolve large size and seem to dominate the carnivore guild for several million years, but then decline and are replaced by new taxa. Moreover, within both ancient and Cenozoic predator clades, there are parallel trends over time toward increased body size and hypercarnivory that likely result from a combination of interspecific competition and energetic constraints.

scholarly journals Stable isotope analyses revealed the influence of foraging habitat on mercury accumulation in tropical coastal marine fish

2019 ◽  
Vol 650 ◽  
pp. 2129-2140 ◽  
Author(s):  
Gaël Le Croizier ◽  
Gauthier Schaal ◽  
David Point ◽  
François Le Loc'h ◽  
Eric Machu ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Marine Fish ◽  
Mercury Accumulation ◽  
Foraging Habitat ◽  
Stable Isotope Analyses ◽  
Coastal Marine ◽  
Isotope Analyses

Chemosynthesis and Chemosymbiosis in the Fossil Record: Detecting Unusual Communities Using Isotope Geochemistry

1998 ◽  
Vol 4 ◽  
pp. 255-285 ◽  
Author(s):  
Emily A. Cobabe
Keyword(s):  
Stable Isotope ◽  
Fossil Record ◽  
Hydrothermal Vents ◽  
Evolutionary History ◽  
Isotope Geochemistry ◽  
Selective Advantage ◽  
Geochemical Proxies ◽  
Second Tier ◽  
Geologic Record ◽  
Life On Earth

The exploration of chemosynthetic communities in the geologic record over the last ten years has generated a series of sedimentological, tectonic and geochemical criteria that help define a continuum of environments from hot hydrothermal vents to nearshore geothermal deposits. Many of these studies have used stable isotope geochemistry to uncover a depleted carbon signature that characterizes most fossil chemosynthetically derived deposits. Isotope geochemistry (carbon, nitrogen and sulfur) as been an important thread in the story of the discovery of modern chemosynthetic communities, as well, adding to understanding of the biogeochemistry of these ecosystems. With increasing awareness of the prominence of these communities, not just as a biological novelty, but as a fundamental component of life on Earth (and perhaps elsewhere), the drive to develop geochemical proxies for chemosynthetic taxa in the fossil record intensifies. Increased ability to recognize these communities provides access to a second tier of paleobiological questions, including ideas of evolutionary history and selective advantage.

scholarly journals Cladogenesis and replacement in the fossil record of Microsyopidae (?Primates) from the southern Bighorn Basin, Wyoming

2021 ◽  
Vol 17 (2) ◽  
Author(s):  
Mary T. Silcox ◽  
Keegan R. Selig ◽  
Thomas M. Bown ◽  
Amy E. Chew ◽  
Kenneth D. Rose
Keyword(s):  
Fossil Record ◽  
Evolutionary Change ◽  
Local Extinction ◽  
Bighorn Basin ◽  
Early Eocene ◽  
Evolutionary Transitions ◽  
Continuous Record ◽  
Extinction Event ◽  
Nearly Continuous

The early Eocene of the southern Bighorn Basin, Wyoming, is notable for its nearly continuous record of mammalian fossils. Microsyopinae (?Primates) is one of several lineages that shows evidence of evolutionary change associated with an interval referred to as Biohorizon A. Arctodontomys wilsoni is replaced by a larger species, Arctodontomys nuptus , during the biohorizon interval in what is likely an immigration/emigration or immigration/local extinction event. The latter is then superseded by Microsyops angustidens after the end of the Biohorizon A interval. Although this pattern has been understood for some time, denser sampling has led to the identification of a specimen intermediate in morphology between A. nuptus and M. angustidens , located stratigraphically as the latter is appearing. Because specimens of A. nuptus have been recovered approximately 60 m above the appearance of M. angustidens , it is clear that A. nuptus did not suffer pseudoextinction. Instead, evidence suggests that M. angustidens branched off from a population of A. nuptus , but the latter species persisted. This represents possible evidence of cladogenesis, which has rarely been directly documented in the fossil record. The improved understanding of both evolutionary transitions with better sampling highlights the problem of interpreting gaps in the fossil record as punctuations.

Biogeographic and evolutionary patterns of continental margin benthic foraminifera

Paleobiology ◽  
1989 ◽  
Vol 15 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Martin A. Buzas ◽  
Stephen J. Culver
Keyword(s):  
North America ◽  
Continental Margin ◽  
Endemic Species ◽  
Benthic Foraminifera ◽  
Fossil Record ◽  
Data Sets ◽  
Evolutionary Patterns ◽  
Geographic Ranges ◽  
Centers Of Origin ◽  
Wide Geographic Distribution

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.

Evolution of mammalian biology

2004 ◽  
Author(s):  
T.S. Kemp
Keyword(s):  
Fossil Record ◽  
Vertebral Column ◽  
The Body ◽  
Evolutionary Transitions ◽  
Highly Sensitive ◽  
Jaw Musculature ◽  
Very High ◽  
Insight Into ◽  
Biological Differences ◽  
Considerable Insight

There are large biological differences between the mammals and the primitive living amniotes as represented by turtles, lizards, and crocodiles ● Differentiated dentition with occluding post-canine teeth, and radical reorganisation of jaw musculature to operate them ● Differentiation of vertebral column and limb musculature, and repositioning of limbs to bring feet under the body, increasing agility of locomotion ● Relatively huge brain and highly sensitive sense organs ● Endothermic temperature physiology, with very high metabolic rates, insulation, and high respiratory rates ● Precise osmoregulatory and chemoregulatory abilities using loops of Henle in the kidney and an array of endocrine mechanisms Incomplete as it is, the fossil record of the mammal-like reptiles, or ‘non-mammalian synapsids’ permits the reconstruction of a series of hypothetical intermediate stages that offers considerable insight into how, when, and where this remarkable transition occurred. Deriving these stages starts with a cladogram of the relevant fossils that is then read as an evolutionary tree, with hypothetical ancestors represented by the nodes. The characters that define a node, plus the characters of the previous nodes, constitute the reconstruction. The differences in characters between adjacent nodes represent the evolutionary transitions that by inference occurred, and the whole set of successive nodes generates all that can be inferred about the sequence of acquisition of characters. If a hypothetical ancestral synapsid is placed at the base of the cladogram, and a hypothetical ancestral mammal as the final node, then the set of nodes in between represents everything the fossil record is capable of revealing about the pattern by which mammalian characters evolved: the sequence of their acquisition, the correlations between characters, and possibly the rates of their evolution. Of course, the inferred pattern of evolution of characters is only as reliable as the cladogram which generated it, and that in turn is only as realistic as the model of evolution used in its construction from the character data. And of course, there must have been many intermediate stages in the transition than cannot be reconstructed for want of appropriate fossil representation of those particular grades. Nevertheless, limited as it may be, this is what can be known from the fossil record.

scholarly journals A unique winged euthycarcinoid from the Permian of Antarctica

2017 ◽  
Vol 91 (5) ◽  
pp. 987-993
Author(s):  
Joseph H. Collette ◽  
John L. Isbell ◽  
Molly F. Miller
Keyword(s):  
Fossil Record ◽  
Trace Fossil ◽  
Morphological Similarity ◽  
Evolutionary Transitions ◽  
Body Segments ◽  
Rapid Transition ◽  
Proglacial Lake ◽  
High Degree ◽  
Freshwater Environments

AbstractEuthycarcinoid arthropods (Cambrian–Triassic) were likely the first animals to transition from oceanic to freshwater and emergent environments. Although their basic bauplan is well known, they have a poor fossil record because their non-sclerotized exoskeleton was rarely preserved. Euthycarcinoids’ unusual morphology (varying numbers of body segments, seemingly dichotomous possession of either mandibles or a labrum, specialized or generalized limbs, and possession by some euthycarcinoid species of sternal pores—structures possibly analogous to coxal vesicles in myriapods) contribute to uncertainty regarding their relationship to other arthropod groups; while their poor fossil record masks the evolutionary transitions within and between the separate realms they inhabited (marine, freshwater, emergent). A new euthycarcinoid from a Permian polar proglacial lake is described herein that is morphologically unlike all other euthycarcinoids, and interpreted as being well adapted for a nekton-benthic lifestyle. Antarcticarcinus pagoda n. gen. n. sp. possesses a pair of large wing-like processes that project laterally from the preabdominal dorsal exoskeleton. A trace fossil from the overlying Mackellar Formation, cf. Orbiculichnus, which was previously interpreted as having been produced by insects taking off or landing on wet sediments, is reinterpreted herein as being produced by A. pagoda n. gen. n. sp. due to the high degree of morphological similarity between traces and body fossils. This occurrence indicates that euthycarcinoids were able to adapt to life in temperate freshwater environments, while possible subaerial adaptations hint at an ability to breathe air. Indeed, if euthycarcinoids could breathe air, Cambrian terrestrial forays and rapid transition (by the Ordovician) into freshwater environments might be explained.

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