Tony Huynh | University of California, Berkeley (original) (raw)

Papers by Tony Huynh

ABSTRACT Blastoids were a group of stalked, sessile echinoderm preserved in rocks that span the m... more ABSTRACT Blastoids were a group of stalked, sessile echinoderm preserved in rocks that span the middle Ordovician (~}470 mya) to the end of the Permian (~{250 mya). These extinct echinoderms possessed hydrospires, uniquely complex internal thecal structures with putative respiratory function. Here, we present measurement and visualization of flow within the hydrospires using a 3D-printed and Reynolds-similar physical model of the interior of a hydrospire of the blastoid Pentremites rusticus, to examine in further detail possible functions of the hydrospire. Specifically, the model allows examination of the extent to which the pattern of flow within the hydrospire kept oxygen-rich incurrent water separated from water that had already been depleted of oxygen. If the flow pattern within the hydrospire fails to keep these two bodies of water separate, this would suggest some other function for the hydrospires. In addition, the model also allows for determination of whether active pumping would have been required to achieve optimal respiratory function, or whether passive pumping alone was sufficient. Furthermore, the model allows for testing of the hypothesis that the need for removal of digestive waste, thought to be associated with the hydrospires, is responsible for some unusual aspects of the hydrospires, such as the conical shape of the putative excurrent canals and the presence of cover plates over the remarkably large excurrent openings.

PeerJ, 2014

The capacity for aerial maneuvering was likely a major influence on the evolution of flying anima... more The capacity for aerial maneuvering was likely a major influence on the evolution of flying animals. Here we evaluate consequences of paravian morphology for aerial performance by quantifying static stability and control effectiveness of physical models for numerous taxa sampled from within the lineage leading to birds (Paraves). Results of aerodynamic testing are mapped phylogenetically to examine how maneuvering characteristics correspond to tail shortening, forewing elaboration, and other morphological features. In the evolution of Paraves we observe shifts from static stability to inherently unstable aerial planforms; control effectiveness also migrated from tails to the forewings. These shifts suggest that a some degree of aerodynamic control and capacity for maneuvering preceded the evolution of a strong power stroke. The timing of shifts also suggests features normally considered in light of development of a power stroke may play important roles in control. JR. 2013. Linking the evolution of body shape and locomotor biomechanics in bird-line archosaurs. Nature 497:104-107 DOI 10.1038/nature12059. Beebe CW. 1915. A tetrapteryx stage in the ancestry of birds. Zoologica 2:39-52. Benton MJ. 2005. Vertebrate paleontology. Malden, MA: Blackwell Publishing. Burch SH. 2014. Complete forelimb myology of the basal theropod dinosaur Tawa hallae based on a novel robust muscle reconstruction method. Mindell D. 2004. Phylogenetic relationships among modern birds (Neornithes): toward an avian tree of life. In: Cracraft J, Donoghue MJ, eds. Assembling the tree of life. Oxford: Oxford University Press, 468-489. Davis M. 2008. Four winged dinosaur. NOVA television broadcast on PBS, February 26, 2008. Dial K. 2003. Wing-assisted incline running and the evolution of flight. Science 299:402-404 Tse K, Koehl M. 2014b. Aerodynamic characteristics of a feathered dinosaur measured using physical models. effects of form on static stability and control effectiveness. PLoS ONE 9:e85203 JK. 2008. A new basal lineage of early Cretaceous birds from China and its implications on the evolution of the avian tail. Paleontology 51:775-791

Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from h... more Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from hatching through 14 days-post-hatching (dph). Asymmetric movements of the wings were used from 1-8 dph to effect progressively more successful righting behaviour via body roll. Following 8 dph, wing motions transitioned to bilaterally symmetric flapping that yielded aerial righting via nose-down pitch, along with substantial increases in vertical force production during descent. Ontogenetically, the use of such wing motions to effect aerial righting precedes both symmetric flapping and a previously documented behaviour in chukar (i.e., wing-assisted incline running) hypothesized to be relevant to incipient flight evolution in birds. These findings highlight the importance of asymmetric wing activation and controlled aerial manoeuvres during bird development, and are potentially relevant to understanding the origins of avian flight.

PLoS ONE, 2014

We report the effects of posture and morphology on the static aerodynamic stability and control e... more We report the effects of posture and morphology on the static aerodynamic stability and control effectiveness of physical models based on the feathered dinosaur, { Microraptor gui, from the Cretaceous of China. Postures had similar lift and drag coefficients and were broadly similar when simplified metrics of gliding were considered, but they exhibited different stability characteristics depending on the position of the legs and the presence of feathers on the legs and the tail. Both stability and the function of appendages in generating maneuvering forces and torques changed as the glide angle or angle of attack were changed. These are significant because they represent an aerial environment that may have shifted during the evolution of directed aerial descent and other aerial behaviors. Certain movements were particularly effective (symmetric movements of the wings and tail in pitch, asymmetric wing movements, some tail movements). Other appendages altered their function from creating yaws at high angle of attack to rolls at low angle of attack, or reversed their function entirely. While { M. gui lived after { Archaeopteryx and likely represents a side experiment with feathered morphology, the general patterns of stability and control effectiveness suggested from the manipulations of forelimb, hindlimb and tail morphology here may help understand the evolution of flight control aerodynamics in vertebrates. Though these results rest on a single specimen, as further fossils with different morphologies are tested, the findings here could be applied in a phylogenetic context to reveal biomechanical constraints on extinct flyers arising from the need to maneuver.

Palaeontologia Electronica, Mar 30, 2015

ABSTRACT Blastoids were a group of stalked, sessile echinoderm preserved in rocks that span the m... more ABSTRACT Blastoids were a group of stalked, sessile echinoderm preserved in rocks that span the middle Ordovician (~}470 mya) to the end of the Permian (~{250 mya). These extinct echinoderms possessed hydrospires, uniquely complex internal thecal structures with putative respiratory function. Here, we present measurement and visualization of flow within the hydrospires using a 3D-printed and Reynolds-similar physical model of the interior of a hydrospire of the blastoid Pentremites rusticus, to examine in further detail possible functions of the hydrospire. Specifically, the model allows examination of the extent to which the pattern of flow within the hydrospire kept oxygen-rich incurrent water separated from water that had already been depleted of oxygen. If the flow pattern within the hydrospire fails to keep these two bodies of water separate, this would suggest some other function for the hydrospires. In addition, the model also allows for determination of whether active pumping would have been required to achieve optimal respiratory function, or whether passive pumping alone was sufficient. Furthermore, the model allows for testing of the hypothesis that the need for removal of digestive waste, thought to be associated with the hydrospires, is responsible for some unusual aspects of the hydrospires, such as the conical shape of the putative excurrent canals and the presence of cover plates over the remarkably large excurrent openings.

PeerJ, 2014

The capacity for aerial maneuvering was likely a major influence on the evolution of flying anima... more The capacity for aerial maneuvering was likely a major influence on the evolution of flying animals. Here we evaluate consequences of paravian morphology for aerial performance by quantifying static stability and control effectiveness of physical models for numerous taxa sampled from within the lineage leading to birds (Paraves). Results of aerodynamic testing are mapped phylogenetically to examine how maneuvering characteristics correspond to tail shortening, forewing elaboration, and other morphological features. In the evolution of Paraves we observe shifts from static stability to inherently unstable aerial planforms; control effectiveness also migrated from tails to the forewings. These shifts suggest that a some degree of aerodynamic control and capacity for maneuvering preceded the evolution of a strong power stroke. The timing of shifts also suggests features normally considered in light of development of a power stroke may play important roles in control. JR. 2013. Linking the evolution of body shape and locomotor biomechanics in bird-line archosaurs. Nature 497:104-107 DOI 10.1038/nature12059. Beebe CW. 1915. A tetrapteryx stage in the ancestry of birds. Zoologica 2:39-52. Benton MJ. 2005. Vertebrate paleontology. Malden, MA: Blackwell Publishing. Burch SH. 2014. Complete forelimb myology of the basal theropod dinosaur Tawa hallae based on a novel robust muscle reconstruction method. Mindell D. 2004. Phylogenetic relationships among modern birds (Neornithes): toward an avian tree of life. In: Cracraft J, Donoghue MJ, eds. Assembling the tree of life. Oxford: Oxford University Press, 468-489. Davis M. 2008. Four winged dinosaur. NOVA television broadcast on PBS, February 26, 2008. Dial K. 2003. Wing-assisted incline running and the evolution of flight. Science 299:402-404 Tse K, Koehl M. 2014b. Aerodynamic characteristics of a feathered dinosaur measured using physical models. effects of form on static stability and control effectiveness. PLoS ONE 9:e85203 JK. 2008. A new basal lineage of early Cretaceous birds from China and its implications on the evolution of the avian tail. Paleontology 51:775-791

Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from h... more Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from hatching through 14 days-post-hatching (dph). Asymmetric movements of the wings were used from 1-8 dph to effect progressively more successful righting behaviour via body roll. Following 8 dph, wing motions transitioned to bilaterally symmetric flapping that yielded aerial righting via nose-down pitch, along with substantial increases in vertical force production during descent. Ontogenetically, the use of such wing motions to effect aerial righting precedes both symmetric flapping and a previously documented behaviour in chukar (i.e., wing-assisted incline running) hypothesized to be relevant to incipient flight evolution in birds. These findings highlight the importance of asymmetric wing activation and controlled aerial manoeuvres during bird development, and are potentially relevant to understanding the origins of avian flight.

PLoS ONE, 2014

We report the effects of posture and morphology on the static aerodynamic stability and control e... more We report the effects of posture and morphology on the static aerodynamic stability and control effectiveness of physical models based on the feathered dinosaur, { Microraptor gui, from the Cretaceous of China. Postures had similar lift and drag coefficients and were broadly similar when simplified metrics of gliding were considered, but they exhibited different stability characteristics depending on the position of the legs and the presence of feathers on the legs and the tail. Both stability and the function of appendages in generating maneuvering forces and torques changed as the glide angle or angle of attack were changed. These are significant because they represent an aerial environment that may have shifted during the evolution of directed aerial descent and other aerial behaviors. Certain movements were particularly effective (symmetric movements of the wings and tail in pitch, asymmetric wing movements, some tail movements). Other appendages altered their function from creating yaws at high angle of attack to rolls at low angle of attack, or reversed their function entirely. While { M. gui lived after { Archaeopteryx and likely represents a side experiment with feathered morphology, the general patterns of stability and control effectiveness suggested from the manipulations of forelimb, hindlimb and tail morphology here may help understand the evolution of flight control aerodynamics in vertebrates. Though these results rest on a single specimen, as further fossils with different morphologies are tested, the findings here could be applied in a phylogenetic context to reveal biomechanical constraints on extinct flyers arising from the need to maneuver.

Palaeontologia Electronica, Mar 30, 2015