Perspectives on the Evolution and Diversification of the Diatoms

2007 ◽  
Vol 13 ◽  
pp. 1-12 ◽  
Author(s):  
Matthew L. Julius
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Early Jurassic ◽  
Late Triassic ◽  
Evolutionary Relationships ◽  
Data Sets ◽  
Diatom Species ◽  
Generic Level ◽  
Existing Data

The understanding of diatom evolution has progressed greatly over the last two decades. Existing data sets have been reanalyzed, new data sets have been generated, and new tools have been employed. Hindering progress is the seemingly endless number of diatom species remaining to be described and relative small number of investigators active in the field. This problem is further confounded by the dramatic reorganization of generic level classification in the group. Despite these problems, many conclusions can be made about prior hypotheses concerning the group's development. Most notably, the origin of the diatoms can be bracketed between the Late Triassic and Early Jurassic using fossil record and molecular clock estimates. This combination of techniques has also provided consensus and clarification to the origin and duration of specific lineages enhancing our understanding of the group's diversification, early ecology, and evolutionary relationships.

Taxonomic diversity estimation using rarefaction

Paleobiology ◽  
1975 ◽  
Vol 1 (4) ◽  
pp. 333-342 ◽  
Author(s):  
David M. Raup
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Sample Size ◽  
Fossil Record ◽  
World Wide ◽  
Taxonomic Diversity ◽  
Early Jurassic ◽  
Late Triassic ◽  
Geologic Time ◽  
Large Samples

Benthic ecologists have successfully applied rarefaction techniques to the problem of compensating for the effect of sample size on apparent species diversity (= species richness). The same method can be used in studies of diversity at higher taxonomic levels (families and orders) in the fossil record where samples represent world-wide distributions of species or genera over long periods of geologic time.Application of rarefaction to several large samples of post-Paleozoic echinoids (totaling 7,911 species) confirms the utility of the method. Rarefaction shows that the observed increase in the number of echinoid families since the Paleozoic is real in the sense that it cannot be explained solely by the increase in numbers of preserved species. There has been no statistically significant increase in the number of families since mid-Cretaceous, however. At the order level, echinoid diversity may have been nearly constant since late Triassic or early Jurassic.

A Survey of Mammalian Origins

1984 ◽  
Vol 8 ◽  
pp. 32-47
Author(s):  
Farish A. Jenkins
Keyword(s):  
Fossil Record ◽  
Early Jurassic ◽  
The Other ◽  
Current Understanding ◽  
Late Triassic ◽  
Early Permian ◽  
Substantial Modification ◽  
Evolution Of Mammals

The origin of mammals, often treated as a discrete but obscure event that took place sometime between the Late Triassic and Early Jurassic, can also be viewed as the product of many transitions - from the early synapsid radiations during the Pennsylvanian and Early Permian through the emergence of placentals and marsupials in the Cretaceous (see Hopson, 1969). A fundamental dichotomy appeared early in the evolution of amniotes; sauropsids (represented today by living reptiles and birds) constituted one lineage, synapsids (which includes the mammal-like reptiles- pelycosaurs and therapsids- and their mammalian descendants) the other. Thus, mammalian ancestry may be traced to pelycosaurs that first appear in the fossil record as part of the earliest known reptilian fauna (Carroll, 1982). And mammalian bony and dental structures continued to undergo substantial modification throughout the Mesozoic, long after the appearance of forms technically classified as Mammalia. Given these phylogenetic changes, the suggestion that there occurred a point when mammals “originated” seems simplistic. Yet the major evolutionary stages may still be evaluated with the purpose of identifying the inception of features and functions basic to the radiation of modern mammals. Accordingly, this survey summarizes our current understanding of the evolution of mammals with full acknowledgment that an account of mammalian origins has neither a definitive beginning nor a climactic end.

Speciation in pelagic Protista and its study in the planktonic microfossil record: a review

Paleobiology ◽  
1983 ◽  
Vol 9 (4) ◽  
pp. 327-340 ◽  
Author(s):  
David Lazarus
Keyword(s):  
Deep Sea ◽  
Fossil Record ◽  
Punctuated Equilibrium ◽  
Evolutionary Change ◽  
Morphologic Change ◽  
Data Sets ◽  
Biometric Data ◽  
Future Work ◽  
Existing Data ◽  
Peripheral Isolate

The punctuated equilibrium hypothesis, largely derivable from Mayr's peripheral isolate model of speciation, is but one of many possible paleontologic patterns of speciation which may be tested against the deep-sea fossil record of planktonic microfossils. The nature of reproduction and variation within a species has a profound effect on its expected tempo and mode of evolutionary change. Biologic data on pelagic plankton and on protistan genetics and reproduction suggest that speciation in pelagic holoplanktonic protists may also be parapatric, “equal” allopatric, or the result of hybridization. Each of these models is shown to make testable predictions of paleontologic pattern. Published records of speciation in planktonic deep-sea microfossil data are compatible with these alternative models. Existing data sets are not yet sufficiently complete to provide strong tests. Future work needs to integrate taxonomic, paleoecologic, biogeographic, and biometric data in studies of individual speciation events. Micropaleontologic studies of morphologic change through time may thereby contribute to our understanding of speciation mechanisms in the pelagic protistan plankton.

scholarly journals Phylogenetic and ecomorphologic diversifications of spiriferinid brachiopods after the end-Permian extinction

Paleobiology ◽  
2020 ◽  
Vol 46 (4) ◽  
pp. 495-510
Author(s):  
Zhen Guo ◽  
Zhong-Qiang Chen ◽  
David A. T. Harper
Keyword(s):  
Phylogenetic Analysis ◽  
Small Group ◽  
Phylogenetic Trees ◽  
Early Jurassic ◽  
Late Triassic ◽  
Evolutionary Relationships ◽  
Early Triassic ◽  
Permian Extinction ◽  
Recovery Dynamics

AbstractThe Order Spiriferinida spanning the latest Ordovician to Early Jurassic is a small group of brachiopods overshadowed by other taxon-rich clades during the Paleozoic. It diversified significantly after the end-Permian extinction and became one of the four major clades of Triassic brachiopods. However, the phylogeny and recovery dynamics of this clade during the Triassic still remain unknown. Here, we present a higher-level parsimony-based phylogenetic analysis of Mesozoic spiriferinids to reveal their evolutionary relationships. Ecologically related characters are analyzed to indicate the variances in ecomorphospace occupation and disparity of spiriferinids through the Permian–Triassic (P-Tr) transition. For comparison with potential competitors of the spiriferinids, the pre-extinction spiriferids are also included in the analysis. Phylogenetic trees demonstrate that about half of the Mesozoic families appeared during the Anisian, indicating the greatest phylogenetic diversification at that time. Triassic spiriferinids reoccupied a large part of the ecomorphospace released by its competitor spiriferids during the end-Permian extinction; they also fully exploited the cyrtiniform region and developed novel lifestyles. Ecomorphologic disparity of the spiriferinids dropped greatly in the Early Triassic, but it rebounded rapidly and reached the level attained by the pre-extinction spiriferids in the Late Triassic. The replacement in ecomorphospace occupation between spiriferids and spiriferinids during the P-Tr transition clearly indicates that the empty ecomorphospace released by the extinction of Permian spiriferids was one of the important drivers for the diversification of the Triassic spiriferinids. The Spiriferinida took over the empty ecomorphospace and had the opportunity to flourish.

scholarly journals Macroevolutionary patterns in the evolutionary radiation of archosaurs (Tetrapoda: Diapsida)

2010 ◽  
Vol 101 (3-4) ◽  
pp. 367-382 ◽  
Author(s):  
Stephen L. Brusatte ◽  
Michael J. Benton ◽  
Graeme T. Lloyd ◽  
Marcello Ruta ◽  
Steve C. Wang
Keyword(s):  
Strong Evidence ◽  
Fossil Record ◽  
Morphological Character ◽  
Middle Triassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Morphological Disparity ◽  
Faunal Abundance ◽  
Evolutionary Radiation ◽  
Early Middle Triassic

ABSTRACTThe rise of archosaurs during the Triassic and Early Jurassic has been treated as a classic example of an evolutionary radiation in the fossil record. This paper reviews published studies and provides new data on archosaur lineage origination, diversity and lineage evolution, morphological disparity, rates of morphological character change, and faunal abundance during the Triassic–Early Jurassic. The fundamental archosaur lineages originated early in the Triassic, in concert with the highest rates of character change. Disparity and diversity peaked later, during the Norian, but the most significant increase in disparity occurred before maximum diversity. Archosaurs were rare components of Early–Middle Triassic faunas, but were more abundant in the Late Triassic and pre-eminent globally by the Early Jurassic. The archosaur radiation was a drawn-out event and major components such as diversity and abundance were discordant from each other. Crurotarsans (crocodile-line archosaurs) were more disparate, diverse, and abundant than avemetatarsalians (bird-line archosaurs, including dinosaurs) during the Late Triassic, but these roles were reversed in the Early Jurassic. There is no strong evidence that dinosaurs outcompeted or gradually eclipsed crurotarsans during the Late Triassic. Instead, crurotarsan diversity decreased precipitously by the end-Triassic extinction, which helped usher in the age of dinosaurian dominance.

Protremaster, a new Lower Jurassic genus of asteroid from Antarctica

1985 ◽  
Vol 122 (4) ◽  
pp. 351-359 ◽  
Author(s):  
Andrew B. Smith ◽  
T. H. Tranter
Keyword(s):  
Fossil Record ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Morphological Diversification ◽  
The Family

AbstractA new and well-preserved.asteroid, Protremaster uniserialis (gen. & sp.nov.) is described from the Lower Jurassic (Sinemurian) of Antarctica. This find extends the fossil record of the family Asterinidae and the subfamily Tremasterinae considerably and lends support to the idea that asteroids underwent an important morphological diversification in the late Triassic-early Jurassic.

Liapora neubigi n. g. et n. sp., the first Early Jurassic scyphopolyp with chitino-phosphatic periderm

2019 ◽  
Vol 294 (2) ◽  
pp. 131-142
Author(s):  
Helmut Keupp
Keyword(s):  
Chemical Composition ◽  
Fossil Record ◽  
Early Jurassic ◽  
Late Triassic ◽  
Tube Surface ◽  
New Family ◽  
New Findings

Two cone-shaped Early Jurassic (Late Pliensbachian) chitino-phosphatic fossils are described from a clay pit near Buttenheim (northern Bavaria, Germany). The chemical composition and microstructure of their black wall corresponds partially with that of Palaeozoic presumed scyphopolyps like conulariids and the genus Byronia Matthew, 1899 and show similarities with the circular periderm tube of the modern Stephanoscyphus. A possible relationship to other chitino-phosphatic fossils, like inarticulate brachiopods or anaptychi of ammonites, is excluded. The presence of growth-lines on the tube surface further excludes an interpretation as remains of ecdysozoa (e. g., arthropods). Accordingly, the new findings are assigned to scyphozoan polyps representing a new family Liaporidae, with Liapora neubigi n. g. et n. sp. The new Early Jurassic scyphozoan genus Liopora shortens the gap in the fossil record between the so far youngest known conulariids from the Late Triassic and modern thecate scyphopolyps (Coronatae).

scholarly journals The origin of mammals: chronology and paleobiogeography

1992 ◽  
Vol 6 ◽  
pp. 189-189
Author(s):  
Spencer G. Lucas ◽  
Adrian P. Hunt
Keyword(s):  
Geographic Distribution ◽  
Fossil Record ◽  
New World ◽  
Early Jurassic ◽  
Late Triassic ◽  
Comprehensive Review ◽  
Vertebrate Fauna ◽  
West Texas ◽  
Land Vertebrate

A comprehensive review of the stratigraphic and geographic distribution of the advanced, non-mammalian cynodonts (traversodontids, tritylodontids and tritheledontids) and the Late Triassic-Early Jurassic mammals indicates that: (1) traversodontids were a wholly Triassic group that disappeared during the Rhaetian; during the late Carnian-early Norian they were rare but widespread components of Pangaean land-vertebrate faunas; (2) tritylodontids first appeared in Europe during the Rhaetian, were a cosmopolitan group by the Sinemurian/Pliensbachian and disappeared during the Bathonian; (3) tritheledontids ranged in age from late Carnian to Sinemurian/Pliensbachian and were mostly a New World group; and (4) the oldest mammal is of late Carnian age from West Texas, but there is at least a 10-million-year gap between it and the next oldest mammals from the late Norian of Europe.Advanced cynodont and mammalian distributions of the Late Triassic-Early Jurassic do not suggest Late Triassic paleoprovinciality, but they do support the notion of a cosmopolitan vertebrate fauna during the Sinemurian/Pliensbachian. Proponents of a tritylodontid ancestry of mammals must explain away a 15-million-year-long absence of tritylodontids from the Late Triassic fossil record. In contrast, proponents of a tritheledontid ancestry of mammals need offer no such explanation since tritheledontids and mammals appeared simultaneously during the late Carnian.

Evolutionary relationships among Eimeria spp. (Apicomplexa) infecting cricetid rodents

1987 ◽  
Vol 65 (3) ◽  
pp. 722-735 ◽  
Author(s):  
David W. Reduker ◽  
Donald W. Duszynski ◽  
Terry L. Yates
Keyword(s):  
Cladistic Analysis ◽  
Type A ◽  
Evolutionary Relationships ◽  
Data Sets ◽  
Type B ◽  
Generic Level ◽  
Thin Walls ◽  
Eimeria Spp ◽  
Eimeria Nieschulzi ◽  
Peromyscus Eremicus

Evolutionary relationships among seven species of Eimeria from five species of cricetid rodents (Neotoma albigula, Peromyscus eremicus, Peromyscus leucopus, Peromyscus maniculatus, Peromyscus truei) were examined by phenetic and cladistic analysis of oocyst structure, life-history data, and isozyme banding patterns. Phenetic and cladistic analyses revealed two distinct lineages of Eimeria spp.: type A Eimeria spp. (Eimeria albigulae, Eimeria arizonensis, Eimeria peromysci), characterized by subspheroid oocysts with rough outer walls, lemon-shaped sporocysts, oocyst residua, prominent Stieda bodies, and two obvious wall layers; and type B Eimeria spp. (Eimeria delicata, Eimeria lachrymalis, Eimeria ladronensis, Eimeria lange-barteli), characterized by ellipsoid oocysts with one obvious, smooth wall, no residuum, and ellipsoid or teardrop-shaped sporocysts with thin walls and tiny Stieda bodies. Cladistic analysis of the type A and type B data sets, using Eimeria nieschulzi and Eimeria papillata (hosts: Rattus norvegicus and Mus musculus, respectively) for outgroup comparison, showed the more derived nature of Eimeria spp. infecting Peromyscus spp. relative to those species infecting N. albigula. Comparison of parasite phylogenies to a hypothesized phylogeny for the hosts based on enzyme electrophoretic data revealed patterns of host–parasite phylogenetic congruence that were most evident at the generic level of the hosts.

scholarly journals A palaeoequatorial ornithischian and new constraints on early dinosaur diversification

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141147 ◽  
Author(s):  
Paul M. Barrett ◽  
Richard J. Butler ◽  
Roland Mundil ◽  
Torsten M. Scheyer ◽  
Randall B. Irmis ◽  
...  
Keyword(s):  
South America ◽  
Growth Rates ◽  
Mass Extinction ◽  
Fossil Record ◽  
Early Jurassic ◽  
Late Triassic ◽  
Evolution Of Sociality ◽  
Northern South America ◽  
Dinosaur Evolution ◽  
Broad Scale

Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic–Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history.

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