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Steven W Salisbury - One of the best experts on this subject based on the ideXlab platform.
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reevaluation of the lark quarry dinosaur tracksite late albian cenomanian winton formation central western queensland australia no longer a stampede
Journal of Vertebrate Paleontology, 2013Co-Authors: Anthony Romilio, Ryan T Tucker, Steven W SalisburyAbstract:The Lark Quarry dinosaur tracksite has previously been recognized as recording the stampede of a mixed herd of dozens of small theropod and ornithopod Dinosaurs. A reexamination of trackway material reveals that the small theropod-type tracks, previously assigned to the ichnotaxon Skartopus, can co-occur within individual trackways of the ornithopod-type tracks assigned to Wintonopus. Moreover, in singular deep tracks where the overall surface outline resembles Skartopus, the base of the track can also resemble Wintonopus. Whereas the Wintonopus holotype may reflect the pedal anatomy of a short-toed or subunguligrade ornithopod trackmaker, the elongate 'toe' impressions typically associated with Skartopus (including the holotype) primarily provide information on digit movement through the sediment and, in many instances, may represent swim traces. The morphological differences between the two ichnotaxa are therefore not taxonomically significant and we formally propose that Skartopus australis should be considered a junior synonym of Wintonopus latomorum. Longitudinal depth profiles through tracks indicate that many are swim traces. The sedimentology and lithology of Lark Quarry further indicates the site represents a time-averaged assemblage formed in a fluvial-dominated floodplain under variable subaqueous conditions, with the parallel orientation of the numerous trackways formed by trackmakers under the influence of downstream current flow. This indicates that the fluvial environment may have been a preferred route for hydrophilic bipedal Dinosaurs. We thus do not consider the Lark Quarry dinosaur tracksite to represent a 'stampede.' Instead, the tracksite may represent part of a riverine setting, where the water was shallow, in which small Dinosaurs swam and/or waded.
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a reassessment of large theropod dinosaur tracks from the mid cretaceous late albian cenomanian winton formation of lark quarry central western queensland australia a case for mistaken identity
Cretaceous Research, 2011Co-Authors: Anthony Romilio, Steven W SalisburyAbstract:Multivariate analysis is used to differentiate shape variations between ichnites of theropod and ornithopod Dinosaurs. Tracks of an alleged theropod cf. Tyrannosauropus from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia were examined and foot shape ratios calculated. Multivariate analysis of these shape variables indicates this track-maker was an ornithopod dinosaur. A strong morphological similarity exists between the Lark Quarry ichnites and those of the iguanodontian ichnotaxon Amblydactylus gethingi. Considering the grade of ornithopod this ichnogenus is thought to represent (a non-hadrosaurid styracosternan) and the age and geography of Lark Quarry, we suggest that the track-maker may have been a dinosaur similar to Muttaburrasaurus langdoni. (C) 2010 Elsevier Ltd. All rights reserved.
Chase Doran Brownstein - One of the best experts on this subject based on the ideXlab platform.
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strict_consensus.tre from Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
2021Co-Authors: Chase Doran BrownsteinAbstract:During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the Middle Cretaceous has concealed how Dinosaurs and other terrestrial vertebrates responded to these events. I describe two Dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous Dinosaurs. This skeleton is associated with the first perinate dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are surprisingly comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance
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Supplementary Information (Text);Supplementary Data (Phylogenetic Matrices, Measurements, and Trees) from Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
2021Co-Authors: Chase Doran BrownsteinAbstract:During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the Middle Cretaceous has concealed how Dinosaurs and other terrestrial vertebrates responded to these events. I describe two Dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous Dinosaurs. This skeleton is associated with the first perinate dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are surprisingly comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance
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Hadrosauridae.nex from Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
2021Co-Authors: Chase Doran BrownsteinAbstract:During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the Middle Cretaceous has concealed how Dinosaurs and other terrestrial vertebrates responded to these events. I describe two Dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous Dinosaurs. This skeleton is associated with the first perinate dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are surprisingly comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance
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hadroboots.tre from Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
2021Co-Authors: Chase Doran BrownsteinAbstract:During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the Middle Cretaceous has concealed how Dinosaurs and other terrestrial vertebrates responded to these events. I describe two Dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous Dinosaurs. This skeleton is associated with the first perinate dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are surprisingly comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance
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Hadrosaurid phylogenetic matrix.txt from Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
2021Co-Authors: Chase Doran BrownsteinAbstract:During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the Middle Cretaceous has concealed how Dinosaurs and other terrestrial vertebrates responded to these events. I describe two Dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous Dinosaurs. This skeleton is associated with the first perinate dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are surprisingly comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance
Anthony Romilio - One of the best experts on this subject based on the ideXlab platform.
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an unusual dinosaur track assemblage from the jurassic cretaceous boundary anning formation lufeng basin china
Historical Biology, 2019Co-Authors: Lida Xing, Anthony RomilioAbstract:Late Jurassic dinosaur track assemblages from China are much less common than those reported from the Lower and Middle Jurassic which are heavily dominated by well-known theropod ichnogenera such as Grallator, Eubrontes, Kayentapus, and a few sauropodomorph and ornithischian ichnotaxa. We here report two tridactyl dinosaur morphotypes from the Lufeng Basin in southern China that most closely resemble Late Jurassic Dinehichnus from North America, a probable gracile ornithopod morphotype, and an unnamed avian morphotype reported from rare occurrences in North America and Europe, which we here name as Tridentigerpes ichnogen. nov., accommodating two ichnospecies T. huasibanleei ichnosp. nov. from the Lufeng Basin, and T. pinuelai ichnosp nov., from Spain. These ichnites re-orient our understanding of Late Jurassic dinosaur track distributions in the Late Jurassic of China, which was previously based in large part on very poor material of presumed theropod affinity. Given the sparse body fossil record from southern China including very fragmentary sauropod remains, the ichnological record of diverse bipedal Dinosaurs, suggestive of avian and non-avian Dinosaurs and ornithopods, the Anning Formation represents a type 2b deposit where tracks are more common than skeletal remains and indicative of faunas not represented by the body fossil record.
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reevaluation of the lark quarry dinosaur tracksite late albian cenomanian winton formation central western queensland australia no longer a stampede
Journal of Vertebrate Paleontology, 2013Co-Authors: Anthony Romilio, Ryan T Tucker, Steven W SalisburyAbstract:The Lark Quarry dinosaur tracksite has previously been recognized as recording the stampede of a mixed herd of dozens of small theropod and ornithopod Dinosaurs. A reexamination of trackway material reveals that the small theropod-type tracks, previously assigned to the ichnotaxon Skartopus, can co-occur within individual trackways of the ornithopod-type tracks assigned to Wintonopus. Moreover, in singular deep tracks where the overall surface outline resembles Skartopus, the base of the track can also resemble Wintonopus. Whereas the Wintonopus holotype may reflect the pedal anatomy of a short-toed or subunguligrade ornithopod trackmaker, the elongate 'toe' impressions typically associated with Skartopus (including the holotype) primarily provide information on digit movement through the sediment and, in many instances, may represent swim traces. The morphological differences between the two ichnotaxa are therefore not taxonomically significant and we formally propose that Skartopus australis should be considered a junior synonym of Wintonopus latomorum. Longitudinal depth profiles through tracks indicate that many are swim traces. The sedimentology and lithology of Lark Quarry further indicates the site represents a time-averaged assemblage formed in a fluvial-dominated floodplain under variable subaqueous conditions, with the parallel orientation of the numerous trackways formed by trackmakers under the influence of downstream current flow. This indicates that the fluvial environment may have been a preferred route for hydrophilic bipedal Dinosaurs. We thus do not consider the Lark Quarry dinosaur tracksite to represent a 'stampede.' Instead, the tracksite may represent part of a riverine setting, where the water was shallow, in which small Dinosaurs swam and/or waded.
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a reassessment of large theropod dinosaur tracks from the mid cretaceous late albian cenomanian winton formation of lark quarry central western queensland australia a case for mistaken identity
Cretaceous Research, 2011Co-Authors: Anthony Romilio, Steven W SalisburyAbstract:Multivariate analysis is used to differentiate shape variations between ichnites of theropod and ornithopod Dinosaurs. Tracks of an alleged theropod cf. Tyrannosauropus from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia were examined and foot shape ratios calculated. Multivariate analysis of these shape variables indicates this track-maker was an ornithopod dinosaur. A strong morphological similarity exists between the Lark Quarry ichnites and those of the iguanodontian ichnotaxon Amblydactylus gethingi. Considering the grade of ornithopod this ichnogenus is thought to represent (a non-hadrosaurid styracosternan) and the age and geography of Lark Quarry, we suggest that the track-maker may have been a dinosaur similar to Muttaburrasaurus langdoni. (C) 2010 Elsevier Ltd. All rights reserved.
Sterling J. Nesbitt - One of the best experts on this subject based on the ideXlab platform.
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a large bodied silesaurid from the lifua member of the manda beds middle triassic of tanzania and its implications for body size evolution in dinosauromorpha
Gondwana Research, 2015Co-Authors: Paul M Barrett, Sterling J. Nesbitt, Brandon R PeecookAbstract:Abstract Many dinosaur lineages were characterised by wide ranges of body-size, ranging from taxa that were Marasuchus and lagerpetids, were small-bodied animals with little variation in body-size. Here, we describe a partial femur of an unexpectedly large-bodied silesaurid (non-dinosaurian dinosauriform) from the Lifua Member of the Manda beds (?late Anisian) from southwestern Tanzania. This specimen (NHMUK R16303) is estimated to have had a femoral length of approximately 345 mm, which exceeds that of many Triassic and Lower Jurassic Dinosaurs, and is either a large individual of the contemporary Asilisaurus kongwe or represents a new and otherwise unknown silesaurid taxon. In either case, it shows that body-size increases were more prevalent among early dinosauromorphs than realised previously. Moreover, silesaurid size increase occurred in parallel with that in early Dinosaurs, alongside the convergent acquisition of other features related to locomotion and herbivory. However, Late Triassic faunas including large-bodied sauropodomorph and theropod Dinosaurs lack similarly-sized non-dinosaurian dinosauromorphs, whereas the Lifua Member fauna includes both a large silesaurid and the early ?dinosaur Nyasasaurus , which overlapped in size.
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the oldest dinosaur a middle triassic dinosauriform from tanzania
Biology Letters, 2013Co-Authors: Sterling J. Nesbitt, Paul M Barrett, Christian A. Sidor, Sarah Werning, Alan J. CharigAbstract:The rise of Dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister–taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early Dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that Dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria.
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a complete skeleton of a late triassic saurischian and the early evolution of Dinosaurs
Science, 2009Co-Authors: Sterling J. Nesbitt, Randall B Irmis, Nathan D Smith, Alan H Turner, Alex Downs, Mark A NorellAbstract:Characterizing the evolutionary history of early Dinosaurs is central to understanding their rise and diversification in the Late Triassic. However, fossils from basal lineages are rare. A new theropod dinosaur from New Mexico is a representative of the early North American diversification. Known from several nearly complete skeletons, it reveals a mosaic of plesiomorphic and derived features that clarify early saurischian dinosaur evolution and provide evidence for the antiquity of novel avian character systems including skeletal pneumaticity. The taxon further reveals latitudinal differences among saurischian assemblages during the Late Triassic, demonstrates that the theropod fauna from the Late Triassic of North America was not endemic, and suggests that intercontinental dispersal was prevalent during this time.
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a critical re evaluation of the late triassic dinosaur taxa of north america
Journal of Systematic Palaeontology, 2007Co-Authors: Sterling J. Nesbitt, Randall B Irmis, William G. ParkerAbstract:Synopsis The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re‐evaluation of saurischian and theropod synapomorphies. Here, we re‐evaluate each purported Triassic dinosaur from North America on a specimen by specimen basis using an apomorphy‐based approach. We attempt to assign specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur material from North America indicates that Dinosaurs were rarer and less diverse in these strata than previously thought. This analysis concludes that non‐dinosaurian dinosauriforms were present in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary and/or indistinguishable from corresponding elements in the only well‐known Triassic theropod of North America, Coelophysis bauri. No Triassic material ...
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the late triassic pseudosuchian revueltosaurus callenderi and its implications for the diversity of early ornithischian Dinosaurs
Proceedings of The Royal Society B: Biological Sciences, 2005Co-Authors: William G. Parker, Sterling J. Nesbitt, Randall B Irmis, Jeffrey W Martz, Lori S BrowneAbstract:A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to Dinosaurs. Therefore, dental characters previously used to place Revueltosaurus within the Ornithischia evolved convergently among other archosaur taxa, and cannot be used to diagnose ornithischian dinosaur teeth. As a result, all other putative North American Late Triassic ornithischians, which are all based exclusively on teeth, are cast into doubt. The only reasonably well-confirmed Late Triassic ornithischians worldwide are Pisanosaurus mertii and an unnamed heterodontosaurid from Argentina. This considerably changes the understanding of early dinosaur diversity, distribution and evolution in the Late Triassic.
Mark A Norell - One of the best experts on this subject based on the ideXlab platform.
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dinosaur egg colour had a single evolutionary origin
Nature, 2018Co-Authors: Jasmina Wiemann, Tzuruei Yang, Mark A NorellAbstract:Birds are the only living amniotes with coloured eggs1–4, which have long been considered to be an avian innovation1,3. A recent study has demonstrated the presence of both red-brown protoporphyrin IX and blue-green biliverdin5—the pigments responsible for all the variation in avian egg colour—in fossilized eggshell of a nonavian dinosaur6. This raises the fundamental question of whether modern birds inherited egg colour from their nonavian dinosaur ancestors, or whether egg colour evolved independently multiple times. Here we present a phylogenetic assessment of egg colour in nonavian Dinosaurs. We applied high-resolution Raman microspectroscopy to eggshells that represent all of the major clades of Dinosaurs, and found that egg colour pigments were preserved in all eumaniraptorans: egg colour had a single evolutionary origin in nonavian theropod Dinosaurs. The absence of colour in ornithischian and sauropod eggs represents a true signal rather than a taphonomic artefact. Pigment surface maps revealed that nonavian eumaniraptoran eggs were spotted and speckled, and colour pattern diversity in these eggs approaches that in extant birds, which indicates that reproductive behaviours in nonavian Dinosaurs were far more complex than previously known3. Depth profiles demonstrated identical mechanisms of pigment deposition in nonavian and avian dinosaur eggs. Birds were not the first amniotes to produce coloured eggs: as with many other characteristics7,8 this is an attribute that evolved deep within the dinosaur tree and long before the spectacular radiation of modern birds.
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the osteology of balaur bondoc an island dwelling dromaeosaurid dinosauria theropoda from the late cretaceous of romania
Bulletin of the American Museum of Natural History, 2013Co-Authors: Stephen L. Brusatte, Alan H Turner, Matyas Vremir, Zoltan Csikisava, Akinobu Watanabe, Gregory M Erickson, Mark A NorellAbstract:ABSTRACT The Haţeg Island fauna of the terminal Late Cretaceous (ca. 71–65 million years ago) of Romania is one of the most unusual dinosaur assemblages in the global fossil record. It has long been recognized that many herbivorous Dinosaurs from the Haţeg fauna were dwarfed, morphologically aberrant, and/or primitive relative to mainland contemporaries, and these taxa are often considered examples of the so-called island effect: the evolutionary phenomenon by which island-dwelling species are often dwarfed and anatomically modified. Very little, however, is known about the carnivorous Dinosaurs that inhabited Haţeg Island, and it is unclear whether they were also dwarfed, aberrant, or primitive. In 2009, the discovery of the first substantially complete theropod from the Late Cretaceous of Europe, the holotype of the Romanian dromaeosaurid Balaur bondoc, provided the first clear glimpse at an island-dwelling carnivorous dinosaur. Here we describe and figure this remarkably preserved skeleton in detail. W...
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a complete skeleton of a late triassic saurischian and the early evolution of Dinosaurs
Science, 2009Co-Authors: Sterling J. Nesbitt, Randall B Irmis, Nathan D Smith, Alan H Turner, Alex Downs, Mark A NorellAbstract:Characterizing the evolutionary history of early Dinosaurs is central to understanding their rise and diversification in the Late Triassic. However, fossils from basal lineages are rare. A new theropod dinosaur from New Mexico is a representative of the early North American diversification. Known from several nearly complete skeletons, it reveals a mosaic of plesiomorphic and derived features that clarify early saurischian dinosaur evolution and provide evidence for the antiquity of novel avian character systems including skeletal pneumaticity. The taxon further reveals latitudinal differences among saurischian assemblages during the Late Triassic, demonstrates that the theropod fauna from the Late Triassic of North America was not endemic, and suggests that intercontinental dispersal was prevalent during this time.
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a basal troodontid from the early cretaceous of china
Nature, 2002Co-Authors: Mark A Norell, Xiaolin Wang, Peter J MakovickyAbstract:Troodontid Dinosaurs form one of the most avian-like dinosaur groups1,2,3,4,5. Their phylogenetic position is hotly debated, and they have been allied with almost all principal coelurosaurian lineages6,7,8,9,10,11,12,13. Here we report a basal troodontid dinosaur, Sinovenator changii gen. et sp. nov., from the lower Yixian Formation of China. This taxon has several features that are not found in more derived troodontids, but that occur in dromaeosaurids and avialans. The discovery of Sinovenator and the examination of character distributions along the maniraptoran lineage indicate that principal structural modifications toward avians were acquired in the early stages of maniraptoran evolution.