The bizarre Scansoriopterygidae theropods Yi and Ambopteryx are the only dinosaurs thought to hav... more The bizarre Scansoriopterygidae theropods Yi and Ambopteryx are the only dinosaurs thought to have had skin stretched between elongate fingers that form a potential membranous wing. While these structures have been suggested to have been used in aerial locomotion, this has never been shown to be the case. Demonstrating this function is of great importance because if these wings permitted flight it would support the growing view that theropod dinosaurs evolved flight multiple times in distinctive ways before the origin of modern birds. Here using Laser-Stimulated Fluorescence imaging we re-evaluate the anatomy of Yi and integrate this new information into several different equation-based aerodynamic calculations covering flight potential, methods of take-off (terrestrial-based running, arboreal launch), and powered versus gliding flight capabilities. For the first time we test whether Yi and Ambopteryx had flight capabilities and if so how efficient and effective it was. We also evaluate wing-based behaviours including wing-assisted incline running (WAIR). We find that Yi and Ambopteryx were highly unlikely to have any form of powered flight and had limited gliding abilities compared to similar-sized living and fossil gliders. We find that both taxa could not take-off from a terrestrial setting, supporting the idea that they were likely arboreal. Compared to similar-sized early-diverging fossil paravians, like Archaeopteryx and Microraptor, Scansoriopterygidae show significant deficiencies and differences in flapping-based locomotion models that indicate a much less competent flight stroke with limited aerial abilities. Combining these findings, our results show that the Scansoriopterygidae are not models for the early evolution of bird flight and that their structurally distinct and inefficient wings differed greatly from contemporaneous paravians including the earliest birds. Instead, we propose that Scansoriopterygidae represent a unique but failed flight architecture of non-avialan theropods. These findings conform with emerging data supporting multiple independent origins of flight in modern lineages. They show that the battle to capture the vertebrate aerial morphospace in the Middle to Late Jurassic was a dynamic and complex one not restricted to pterosaurs and only one theropod lineage.
In the recent study in Current Biology by Pei and colleagues1, we used two proxies - wing loading... more In the recent study in Current Biology by Pei and colleagues1, we used two proxies - wing loading and specific lift - to reconstruct powered flight potential across the vaned feathered fossil pennaraptorans. The results recovered multiple origins of powered flight. We respectfully disagree with the criticism raised by Serrano and Chiappe2 that wing loading and specific lift, used in sequence, fail to discriminate between powered flight and gliding. We will explain this in reference to our original conservative approach.
Evolution of birds from non-flying theropod dinosaurs is a classic evolutionary transition, but a... more Evolution of birds from non-flying theropod dinosaurs is a classic evolutionary transition, but a deeper understanding of early flight has been frustrated by disagreement on the relationships between birds (Avialae) and their closest theropod relatives. We address this through a larger, more resolved evolutionary hypothesis produced by a novel automated analysis pipeline tailored for large morphological datasets. We corroborate the grouping of dromaeosaurids + troodontids (Deinonychosauria) as the sister taxon to birds (Paraves), as well as the recovery of Anchiornithidae as basalmost avialans. Using these phylogenetic results and available data for vaned feathered paravians, maximum and minimum estimates of wing loading and specific lift calculated using ancestral state reconstruction analysis are used as proxies for the potential for powered flight through this transition. We found a broad range of paravian ancestors with estimates approaching values that are indicative of powered...
Limb length, cursoriality and speed have long been areas of significant interest in theropod pale... more Limb length, cursoriality and speed have long been areas of significant interest in theropod paleobiology as locomotory capacity, especially running ability, is critical in not just in prey pursuit but also to avoid become prey oneself. One aspect that is traditionally overlooked is the impact of allometry on running ability and the limiting effect of large body size. Since several different non-avian theropod lineages have each independently evolved body sizes greater than any known terrestrial carnivorous mammal, ∼1000kg or more, the effect that such larger mass has on movement ability and energetics is an area with significant implications for Mesozoic paleoecology. Here using expansive datasets, incorporating several different metrics to estimate body size, limb length and running speed, to calculate the effects of allometry running We test both on traditional metrics used to evaluate cursoriality in non-avian theropods such as distal limb length, relative hindlimb length as wel...
Pterosaurs thrived in and around water for 160 + million years but their take-off from water is p... more Pterosaurs thrived in and around water for 160 + million years but their take-off from water is poorly understood. A purportedly low floating position and forward centre of gravity barred pterosaurs from a bird-like bipedal running launch. Quadrupedal water launch similar to extant water-feeding birds and bats has been proposed for the largest pterosaurs, such as Anhanguera and Quetzalcoatlus. However, quadrupedal water launch has never been demonstrated in smaller pterosaurs, including those living around the Tethys Sea in the Late Jurassic Solnhofen Lagoon. Using Laser-Stimulated Fluorescence, we singled out aurorazhdarchid specimen MB.R.3531 that alone preserved specific soft tissues among more than a dozen well-preserved Solnhofen pterosaur specimens. These soft tissues pertain to primary propulsive contact surfaces needed for quadrupedal water launch (pedal webbing and soft tissues from an articulated forelimb) that permit robust calculations of its dynamic feasibility without ...
We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yi... more We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China's Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight-a flight mode common to passeriforms and other small living birds-as early as 125 million years ago.
Background:Powered flight is implicated as a major driver for the success of birds. Here we exami... more Background:Powered flight is implicated as a major driver for the success of birds. Here we examine the effectiveness of three hypothesized pathways for the evolution of the flight stroke, the forelimb motion that powers aerial locomotion, in a terrestrial setting across a range of stem and basal avians: flap running, Wing Assisted Incline Running (WAIR), and wing-assisted leaping.Methods:Using biomechanical mathematical models based on known aerodynamic principals and in vivo experiments and ground truthed using extant avians we seek to test if an incipient flight stroke may have contributed sufficient force to permit flap running, WAIR, or leaping takeoff along the phylogenetic lineage from Coelurosauria to birds.Results:None of these behaviours were found to meet the biomechanical threshold requirements before Paraves. Neither was there a continuous trend of refinement for any of these biomechanical performances across phylogeny nor a signal of universal applicability near the or...
The article focuses on research into pelagornithid species of birds and how the species were able... more The article focuses on research into pelagornithid species of birds and how the species were able to fly while being larger than modern avians. It comments on paleontologist Edouard Lartet's discovery in 1857 of the first pelagornithid, dubbed Pelagornis (P.) micaenus, which had a humerus that measured nearly two feet long. It mentions the discovery of P. sandersi in 2014 with a humerus three feet in length and talks about the bird's aspect ratio, wing load, and wing shape like an albatross.
The bizarre Scansoriopterygidae theropods Yi and Ambopteryx are the only dinosaurs thought to hav... more The bizarre Scansoriopterygidae theropods Yi and Ambopteryx are the only dinosaurs thought to have had skin stretched between elongate fingers that form a potential membranous wing. While these structures have been suggested to have been used in aerial locomotion, this has never been shown to be the case. Demonstrating this function is of great importance because if these wings permitted flight it would support the growing view that theropod dinosaurs evolved flight multiple times in distinctive ways before the origin of modern birds. Here using Laser-Stimulated Fluorescence imaging we re-evaluate the anatomy of Yi and integrate this new information into several different equation-based aerodynamic calculations covering flight potential, methods of take-off (terrestrial-based running, arboreal launch), and powered versus gliding flight capabilities. For the first time we test whether Yi and Ambopteryx had flight capabilities and if so how efficient and effective it was. We also evaluate wing-based behaviours including wing-assisted incline running (WAIR). We find that Yi and Ambopteryx were highly unlikely to have any form of powered flight and had limited gliding abilities compared to similar-sized living and fossil gliders. We find that both taxa could not take-off from a terrestrial setting, supporting the idea that they were likely arboreal. Compared to similar-sized early-diverging fossil paravians, like Archaeopteryx and Microraptor, Scansoriopterygidae show significant deficiencies and differences in flapping-based locomotion models that indicate a much less competent flight stroke with limited aerial abilities. Combining these findings, our results show that the Scansoriopterygidae are not models for the early evolution of bird flight and that their structurally distinct and inefficient wings differed greatly from contemporaneous paravians including the earliest birds. Instead, we propose that Scansoriopterygidae represent a unique but failed flight architecture of non-avialan theropods. These findings conform with emerging data supporting multiple independent origins of flight in modern lineages. They show that the battle to capture the vertebrate aerial morphospace in the Middle to Late Jurassic was a dynamic and complex one not restricted to pterosaurs and only one theropod lineage.
In the recent study in Current Biology by Pei and colleagues1, we used two proxies - wing loading... more In the recent study in Current Biology by Pei and colleagues1, we used two proxies - wing loading and specific lift - to reconstruct powered flight potential across the vaned feathered fossil pennaraptorans. The results recovered multiple origins of powered flight. We respectfully disagree with the criticism raised by Serrano and Chiappe2 that wing loading and specific lift, used in sequence, fail to discriminate between powered flight and gliding. We will explain this in reference to our original conservative approach.
Evolution of birds from non-flying theropod dinosaurs is a classic evolutionary transition, but a... more Evolution of birds from non-flying theropod dinosaurs is a classic evolutionary transition, but a deeper understanding of early flight has been frustrated by disagreement on the relationships between birds (Avialae) and their closest theropod relatives. We address this through a larger, more resolved evolutionary hypothesis produced by a novel automated analysis pipeline tailored for large morphological datasets. We corroborate the grouping of dromaeosaurids + troodontids (Deinonychosauria) as the sister taxon to birds (Paraves), as well as the recovery of Anchiornithidae as basalmost avialans. Using these phylogenetic results and available data for vaned feathered paravians, maximum and minimum estimates of wing loading and specific lift calculated using ancestral state reconstruction analysis are used as proxies for the potential for powered flight through this transition. We found a broad range of paravian ancestors with estimates approaching values that are indicative of powered...
Limb length, cursoriality and speed have long been areas of significant interest in theropod pale... more Limb length, cursoriality and speed have long been areas of significant interest in theropod paleobiology as locomotory capacity, especially running ability, is critical in not just in prey pursuit but also to avoid become prey oneself. One aspect that is traditionally overlooked is the impact of allometry on running ability and the limiting effect of large body size. Since several different non-avian theropod lineages have each independently evolved body sizes greater than any known terrestrial carnivorous mammal, ∼1000kg or more, the effect that such larger mass has on movement ability and energetics is an area with significant implications for Mesozoic paleoecology. Here using expansive datasets, incorporating several different metrics to estimate body size, limb length and running speed, to calculate the effects of allometry running We test both on traditional metrics used to evaluate cursoriality in non-avian theropods such as distal limb length, relative hindlimb length as wel...
Pterosaurs thrived in and around water for 160 + million years but their take-off from water is p... more Pterosaurs thrived in and around water for 160 + million years but their take-off from water is poorly understood. A purportedly low floating position and forward centre of gravity barred pterosaurs from a bird-like bipedal running launch. Quadrupedal water launch similar to extant water-feeding birds and bats has been proposed for the largest pterosaurs, such as Anhanguera and Quetzalcoatlus. However, quadrupedal water launch has never been demonstrated in smaller pterosaurs, including those living around the Tethys Sea in the Late Jurassic Solnhofen Lagoon. Using Laser-Stimulated Fluorescence, we singled out aurorazhdarchid specimen MB.R.3531 that alone preserved specific soft tissues among more than a dozen well-preserved Solnhofen pterosaur specimens. These soft tissues pertain to primary propulsive contact surfaces needed for quadrupedal water launch (pedal webbing and soft tissues from an articulated forelimb) that permit robust calculations of its dynamic feasibility without ...
We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yi... more We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China's Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight-a flight mode common to passeriforms and other small living birds-as early as 125 million years ago.
Background:Powered flight is implicated as a major driver for the success of birds. Here we exami... more Background:Powered flight is implicated as a major driver for the success of birds. Here we examine the effectiveness of three hypothesized pathways for the evolution of the flight stroke, the forelimb motion that powers aerial locomotion, in a terrestrial setting across a range of stem and basal avians: flap running, Wing Assisted Incline Running (WAIR), and wing-assisted leaping.Methods:Using biomechanical mathematical models based on known aerodynamic principals and in vivo experiments and ground truthed using extant avians we seek to test if an incipient flight stroke may have contributed sufficient force to permit flap running, WAIR, or leaping takeoff along the phylogenetic lineage from Coelurosauria to birds.Results:None of these behaviours were found to meet the biomechanical threshold requirements before Paraves. Neither was there a continuous trend of refinement for any of these biomechanical performances across phylogeny nor a signal of universal applicability near the or...
The article focuses on research into pelagornithid species of birds and how the species were able... more The article focuses on research into pelagornithid species of birds and how the species were able to fly while being larger than modern avians. It comments on paleontologist Edouard Lartet's discovery in 1857 of the first pelagornithid, dubbed Pelagornis (P.) micaenus, which had a humerus that measured nearly two feet long. It mentions the discovery of P. sandersi in 2014 with a humerus three feet in length and talks about the bird's aspect ratio, wing load, and wing shape like an albatross.
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