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Tetrapod (structure)
Fossil Record
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The fossil record of exceptionally preserved soft tissues in Konservat-Lagersta ¨tten provides rare yet significant insight into past behaviours and ecologies.Such deposits are known to occur in bursts rather than evenly through time, but reasons for this pattern and implications for the origins of novel structures remain unclear.Previous assessments of these records focused on marine environments preserving chemically heterogeneous tissues from across animals.Here, we investigate the preservation of skin and keratinous integumentary structures in land-dwelling vertebrates (tetrapods) through time, and in distinct terrestrial and marine depositional environments.We also evaluate previously proposed biotic and abiotic controls on the distribution of 143 tetrapod Konservat-Lagersta ¨tten from the Permian to the Pleistocene in a multivariate framework.Gap analyses taking into account sampling intensity and distribution indicate that feathers probably evolved close to their first appearance in the fossil record.By contrast, hair and archosaur filaments are weakly sampled (five times less common than feathers), and their origins may significantly pre-date earliest known occurrences in the fossil record.This work suggests that among-integument variation in preservation can bias the reconstructed first origins of integumentary novelties and has implications for predicting where, and in what depositional environments, to expect further discoveries of exquisitely preserved tetrapod integument.
Tetrapod (structure)
Integument
Fossil Record
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Biochronology
Tetrapod (structure)
Early Triassic
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Tetrapod footprints have a fossil record in rocks of Devonian-Neogene age. Three principal factors limit their use in biostratigraphy and biochronology (palichnostratigraphy): invalid ichnotaxa based on extramorphological variants, slow apparent evolutionary turnover rates and facies restrictions. The ichnotaxonomy of tetrapod footprints has generally been oversplit, largely due to a failure to appreciate extramorphological variation. Thus, many tetrapod footprint ichnogenera and most ichnospecies are useless phantom taxa that confound biostratigraphic correlation and biochronological subdivision. Tracks rarely allow identification of a genus or species known from the body fossil record. Indeed, almost all tetrapod footprint ichnogenera are equivalent to a family or a higher taxon (order, superorder, etc.) based on body fossils. This means that ichnogenera necessarily have much longer temporal ranges and therefore slower apparent evolutionary turnover rates than do body fossil genera. Because of this, footprints cannot provide as refined a subdivision of geological time as do body fossils. The tetrapod footprint record is much more facies controlled than the tetrapod body fossil record. The relatively narrow facies window for track preservation, and the fact that tracks are almost never transported, redeposited or reworked, limits the facies that can be correlated with any track-based biostratigraphy. A Devonian-Neogene global biochronology based on tetrapod footprints generally resolves geologic time about 20 to 50 percent as well as does the tetrapod body fossil record. The following globally recognizable time intervals can be based on the track record: (1) Late Devonian; (2) Mississippian; (3) Early-Middle Pennsylvanian; (4) Late Pennsylvanian; (5) Early Permian; (6) Late Permian; (7) Early-Middle Triassic; (8) late Middle Triassic; (9) Late Triassic; (10) Early Jurassic; (11) Middle-Late Jurassic; (12) Early Cretaceous; (13) Late Cretaceous; (14) Paleogene; (15) Neogene. Tetrapod footprints are most valuable in establishing biostratigraphic datum points, and this is their primary value to understanding the stratigraphic (temporal) dimension of tetrapod evolution.
Tetrapod (structure)
Biochronology
Devonian
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Six compilations of fossil tetrapod families, spanning 100 years, each contain a broadly similar diversity pattern since the Upper Devonian. Comparison of four recent data bases, one of which is derived from a strict cladistic treatment, reveals widespread taxonomic and stratigraphic inaccuracies in three earlier data bases. Improvement of our interpretation of the tetrapod fossil record will come through continued taxonomic and stratigraphic revision as well as discovery of new fossils.
Tetrapod (structure)
Fossil Record
Devonian
Completeness (order theory)
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This chapter enumerates the new species that began to re-inhabit the earth after the End-Frasnian Catastrophe. In the wake of Famennian period, the first tetrapod to live on land, according to the fossil record, was the Russian species Jakubsonia livnensis. It is the sole fossil species known from the Famennian Gap—a gap in fossil records between End-Frasnian catastrophe and Famennian. Afterwards, five new tetrapod species populated Greenland, namely Ichthyostega stensioei, Ichthyostega watsoni, Ichthyostega eigili, Acanthostega gunnari, and Ymeria denticulate. Following the appearance of these five species, two new tetrapod species began to live in Pennsylvania in the United States: the Hynerpeton bassetti and the Frasnian ghost lineage species Densignathus rowei. Lastly, the Tulerpeton curtum dwelt on the land of Russia together with Jakubsonia livnensis.
Tetrapod (structure)
Fossil Record
Lineage (genetic)
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Jurassic tetrapod fossils are known from all of the continents, and their distribution documents a critical paleobiogeographic juncture in tetrapod evolution – the change from cosmopolitan Pangean tetrapod faunas to the provincialized faunas that characterize the late Mesozoic and Cenozoic. Two global tetrapod biochronological units (faunachrons) have been named for the Early Jurassic – Wassonian and Dawan – and reflect some Early Jurassic tetrapod cosmopolitanism. However, after the Dawan, a scattered and poorly-dated Middle Jurassic tetrapod record and a much better understood Upper Jurassic tetrapod record indicate that significant provincialization of the global tetrapod fauna had begun. Middle Jurassic tetrapod assemblages include distinct local genera of sauropod dinosaurs, which are large, mobile terrestrial tetrapods, and this suggests marked provinciality by Bajocian time. The obvious provincialism of well known Chinese Middle-Upper Jurassic dinosaur faunas also documents the end of tetrapod cosmopolitanism. The distribution of some Late Jurassic dinosaur taxa defines a province that extended from the western USA through Europe into eastern Africa. Provincial tetrapod biochronologies have already been proposed for this province and for the separate eastern Asian Late Jurassic province. Tetrapod footprints only identify two global assemblage zones, one of Early Jurassic and the other of Middle-Late Jurassic age. The incomplete state of Jurassic tetrapod biochronology reflects both an inadequate record with poor temporal constraints and a relative lack of study of the biostratigraphy of Jurassic fossil vertebrates.
Tetrapod (structure)
Biochronology
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Abstract: The end‐Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.
Tetrapod (structure)
Permian–Triassic extinction event
Fossil Record
Early Triassic
myr
Extinction (optical mineralogy)
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Citations (65)
Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups in
northeastern Arizona and adjacent areas preserve tetrapod body fossils and footprints that are one of the world’s most extensive tetrapod fossil records across the Triassic-Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean-Wassonian boundary approximates the Triassic-Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau confirms that non-crocodilian crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic.
Tetrapod (structure)
Biochronology
Early Triassic
Ladinian
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Tetrapod (structure)
Fossil Record
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Tetrapod (structure)
Fossil Record
Integument
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