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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Arctic region
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Greenland
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East Greenland (1)
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Jameson Land (1)
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fossils
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Chordata
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Vertebrata
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Tetrapoda
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Reptilia
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Diapsida
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Archosauria (1)
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ichnofossils (1)
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tracks (1)
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geologic age
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Mesozoic
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Triassic
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Upper Triassic
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Norian (1)
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Primary terms
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Arctic region
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Greenland
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East Greenland (1)
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Jameson Land (1)
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biogeography (1)
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Chordata
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Vertebrata
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Tetrapoda
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Reptilia
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Diapsida
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Archosauria (1)
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ichnofossils (1)
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Mesozoic
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Triassic
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Upper Triassic
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Norian (1)
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paleoecology (1)
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sedimentary structures
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tracks (1)
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Abstract The Ørsted Dal Member of the Upper Triassic Fleming Fjord Formation in East Greenland is well known for its rich vertebrate fauna, represented by numerous specimens of both body and ichnofossils. In particular, the footprints of theropod dinosaurs have been described. Recently, an international expedition discovered several slabs with 100 small chirotheriid pes and manus imprints (pes length 4–4.5 cm) in siliciclastic deposits of this unit. They show strong similarities with Brachychirotherium , a characteristic Upper Triassic ichnogenus with a global distribution. A peculiar feature in the Fleming Fjord specimens is the lack of a fifth digit, even in more deeply impressed imprints. Therefore, the specimens are assigned here tentatively to cf. Brachychirotherium . Possibly, this characteristic is related to the extremely small size and early ontogenetic stage of the trackmaker. The record from Greenland is the first evidence of this morphotype from the Fleming Fjord Formation. Candidate trackmakers are crocodylian stem group archosaurs; however, a distinct correlation with known osteological taxa from this unit is not currently possible. While the occurrence of sauropodomorph plateosaurs in the bone record links the Greenland assemblage more closer to that from the Germanic Basin of central Europe, here the described footprints suggest a Pangaea-wide exchange. Supplementary material: Three-dimensional model of cf. Brachychirotherium pes–manus set (from MGUH 31233b) from the Upper Triassic Fleming Fjord Formation (Norian–Rhaetian) of East Greenland as pdf, ply and jpg files (3D model created by Oliver Wings; photographs taken by Jesper Milàn) is available at https://doi.org/10.6084/m9.figshare.c.2133546
Abstract Triassic tetrapod footprints have a Pangaea-wide distribution; they are known from North America, South America, Europe, North Africa, China, Australia, Antarctica and South Africa. They often occur in sequences that lack well-preserved body fossils. Therefore, the question arises, how well can tetrapod footprints be used in age determination and correlation of stratigraphic units? The single largest problem with Triassic footprint biostratigraphy and biochronology is the non-uniform ichnotaxonomy and evaluation of footprints that show extreme variation in shape due to extramorphological (substrate-related) phenomena. Here, we exclude most of the countless ichnospecies of Triassic footprints, and instead we consider ichnogenera and form groups that show distinctive, anatomically-controlled features. Several characteristic footprint assemblages and ichnotaxa have a restricted stratigraphic range and obviously occur in distinct time intervals. This can be repeatedly observed in the global record. Some reflect distinct stages in the evolutionary development of the locomotor apparatus as indicated by their digit proportions and the trackway patterns. Essential elements are archosaur tracks with Rotodactylus , the chirotherian ichnotaxa Protochirotherium , Synaptichnium , Isochirotherium , Chirotherium and Brachychirotherium , and grallatorids that can be partly linked in a functional-evolutionary sequence. Non-archosaur footprints are common, especially the ichnotaxa Rhynchosauroides , Procolophonichnium , Capitosauroides and several dicynodont-related or mammal-like forms. They are dominant in some footprint assemblages. From the temporal distribution pattern we recognize five distinct tetrapod-footprint-based biochrons likened to the known land-vertebrate faunachrons (LVFs) of the tetrapod body fossil record: 1. Dicynodont tracks (Lootsbergian=Induan age); 2. Protochirotherium ( Synaptichnium ), Rhynchosauroides , Procolophonichnium (Nonesian=Induan–Olenekian age); 3. Chirotherium barthii , C. sickleri , Isochirotherium , Synaptichnium (‘ Brachychirotherium ’), Rotodactylus , Rhynchosauroides , Procolophonichnium , dicynodont tracks, Capitosauroides (Nonesian–Perovkan=Olenekian–early Anisian); 4. Atreipus–Grallator (‘ Coelurosaurichnus ’), Synaptichnium (‘ Brachychirotherium ’), Isochirotherium , Sphingopus , Parachirotherium , Rhynchosauroides , Procolophonichnium (Perovkan–Berdyankian=Late Anisian–Ladinian); 5. Brachychirotherium , Atreipus – Grallator , Grallator , Eubrontes , Apatopus , Rhynchosauroides , dicynodont tracks (Otischalkian–Apachean=Carnian–Rhaetian). Tetrapod footprints are useful for biostratigraphy and biochronology of the Triassic. However, compared to the tetrapod body fossil record with eight biochrons, the five footprint-based biochrons show less resolution of faunal turnover as ichnogenera and ichnospecies at best reflect biological families or higher biotaxonomic units. Nevertheless, in sequences where body fossils are rare, footprints can coarsely indicate their stratigraphic age.