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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.
Philip J. Currie - One of the best experts on this subject based on the ideXlab platform.
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Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures
'Springer Science and Business Media LLC', 2021Co-Authors: Fabien L. Condamine, Michael J Benton, Guillaume Guinot, Philip J. CurrieAbstract:Dinosaurs are thought to have been driven extinct by an asteroid impact 66 million years ago. Here, Condamine et al. show that six major Dinosaur families were already in decline in the preceding 10 million years, possibly due to global cooling and competition among herbivores
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bristles before down a new perspective on the functional origin of feathers
Evolution, 2015Co-Authors: Walter Scott Persons, Philip J. CurrieAbstract:: Over the course of the last two decades, the understanding of the early evolution of feathers in nonavian Dinosaurs has been revolutionized. It is now recognized that early feathers had a simple form comparable in general structure to the hairs of mammals. Insight into the prevalence of simple feathers throughout the Dinosaur family tree has gradually arisen in tandem with the growing evidence for endothermic Dinosaur metabolisms. This has led to the generally accepted opinion that the early feather coats of Dinosaurs functioned as thermo insulation. However, thermo insulation is often erroneously stated to be a likely functional explanation for the origin of feathers. The problem with this explanation is that, like mammalian hair, simple feathers could serve as insulation only when present in sufficiently high concentrations. The theory therefore necessitates the origination of feathers en masse. We advocate for a novel origin theory of feathers as bristles. Bristles are facial feathers common among modern birds that function like mammalian tactile whiskers, and are frequently simple and hair-like in form. Bristles serve their role in low concentrations, and therefore offer a feasible first stage in feather evolution.
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a mummified duck billed Dinosaur with a soft tissue cock s comb
Current Biology, 2014Co-Authors: Phil R Bell, Philip J. Currie, Federico Fanti, Victoria M ArbourAbstract:Summary Among living vertebrates, soft tissues are responsible for labile appendages (combs, wattles, proboscides) that are critical for activities ranging from locomotion to sexual display [1]. However, soft tissues rarely fossilize, and such soft-tissue appendages are unknown for many extinct taxa, including Dinosaurs. Here we report a remarkable "mummified" specimen of the hadrosaurid Dinosaur Edmontosaurus regalis from the latest Cretaceous Wapiti Formation, Alberta, Canada, that preserves a three-dimensional cranial crest (or "comb") composed entirely of soft tissue. Previously, crest function has centered on the hypertrophied nasal passages of lambeosaurine hadrosaurids, which acted as resonance chambers during vocalization [2–4]. The fleshy comb in Edmontosaurus necessitates an alternative explanation most likely related to either social signaling or sexual selection [5–7]. This discovery provides the first view of bizarre, soft-tissue signaling structures in a Dinosaur and provides additional evidence for social behavior. Crest evolution within Hadrosaurinae apparently culminated in the secondary loss of the bony crest at the terminal Cretaceous; however, the new specimen indicates that cranial ornamentation was in fact not lost but substituted in Edmontosaurus by a fleshy display structure. It also implies that visual display played a key role in the evolution of hadrosaurine crests and raises the possibility of similar soft-tissue structures among other Dinosaurs.
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a microraptorine Dinosauria dromaeosauridae from the late cretaceous of north america
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Nicholas R Longrich, Philip J. CurrieAbstract:The fossil assemblages of the Late Cretaceous of North America are dominated by large-bodied Dinosaur species. Associated skeletons of small Dinosaurs are exceedingly rare, and small (<10 kg) carnivorous theropods have not previously been reported from these beds. Here, we describe a small dromaeosaurid from the 75-million-year-old Dinosaur Park Formation of Alberta, Canada. Hesperonychus elizabethae gen. et sp. nov. is represented by a pelvic girdle from an animal weighing approximately 1,900 g. Despite its size, the pubes and ilia are coossified, indicating that the animal was somatically mature. This is the smallest carnivorous, nonavian Dinosaur known from North America. Phylogenetic analysis of Hesperonychus reveals that it is not closely related to previously described North American dromaeosaurids. Instead, Hesperonychus is a member of the dromaeosaurid clade Microraptorinae, a group containing the 4-winged Microraptor and the feathered Sinornithosaurus, both from the Lower Cretaceous Jehol Group of China. Hesperonychus is the youngest known member of this lineage, extending the temporal range of the clade by 45 million years, and it is the first microraptorine known from North America, providing further evidence for an affinity between the Dinosaur faunas of North America and Asia. Study of fossil collections from the Dinosaur Park and Oldman formations of Alberta has revealed numerous isolated bones of small, basal dromaeosaurids, which are tentatively referred to Hesperonychus. These fossils suggest that small dromaeosaurids were a significant component of the carnivore community in this Late Cretaceous biota.