Hierarchy theory recognises that ecological and evolutionary units occur in a nested and intercon... more Hierarchy theory recognises that ecological and evolutionary units occur in a nested and interconnected hierarchical system, with cascading effects occurring between hierarchical levels. Different biological disciplines have routinely come into conflict over the primacy of different forcing mechanisms behind evolutionary and ecological change. These disconnects arise partly from differences in perspective (with some researchers favouring ecological forcing mechanisms while others favour developmental/historical mechanisms), as well as differences in the temporal framework in which workers operate. In particular, long-term palaeontological data often show that large-scale (macro) patterns of evolution are predominantly dictated by shifts in the abiotic environment, while short-term (micro) modern biological studies stress the importance of biotic interactions. We propose that thinking about ecological and evolutionary interactions in a hierarchical framework is a fruitful way to resolve these conflicts. Hierarchy theory suggests that changes occurring at lower hierarchical levels can have unexpected, complex effects at higher scales due to emergent interactions between simple systems. In this way, patterns occurring on short-and long-term time scales are equally valid, as changes that are driven from lower levels will manifest in different forms at higher levels. We propose that the dual hierarchy framework fits well with our current understanding of evolutionary and ecological theory. Furthermore, we describe how this framework can be used to understand major extinction events better. Multi-generational attritional loss of reproductive fitness (MALF) has recently been proposed as the primary mechanism behind extinction events, whereby extinction is explainable solely through processes that result in extirpation of populations through a shutdown of reproduction. While not necessarily explicit, the push to explain extinction through solely population-level dynamics could be used to suggest that environmentally mediated patterns of extinction or slowed speciation across geological time are largely artefacts of poor preservation or a coarse temporal scale. We demonstrate how MALF fits into a hierarchical framework, showing that MALF can be a primary forcing mechanism at lower scales that still results in differential survivorship patterns at the species and clade level which vary depending upon the initial environmental forcing mechanism. Thus, even if MALF is the primary mechanism of extinction across all mass extinction events, the primary environmental cause of these events will still affect the system and result in differential responses. Therefore, patterns at both temporal scales are relevant.
In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beak... more In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beaked bird from the Early Cretaceous Jehol Biota in northeastern China. Various soft tissues are visualized and interpreted through the use of laser-stimulated fluorescence, providing much novel anatomical information about this early bird, specifically reticulate scales covering the feet, and the well-developed and robust pro- and postpatagium. We also include a direct comparison between the forelimb soft tissues of Confuciusornis and modern avian patagia. Furthermore, apparently large, fleshy phalangeal pads are preserved on the feet. The reticulate scales, robust phalangeal pads as well as the highly recurved pedal claws strongly support Confuciusornis as an arboreal bird. Reticulate scales are more rounded than scutate scales and do not overlap, thus allowing for more flexibility in the toe. The extent of the pro- and postpatagium and the robust primary feather rachises are evidence that Confuciusornis was capable of powered flight, contrary to previous reports suggesting otherwise. A unique avian wing shape is also reconstructed based on plumage preserved. These soft tissues combined indicate an arboreal bird with the capacity for short-term (non-migratory) flight, and suggest that, although primitive, Confuciusornis already possessed many relatively advanced avian anatomical characteristics.
The bird track localities of the Republic of Korea are among the richest and most diverse avian t... more The bird track localities of the Republic of Korea are among the richest and most diverse avian tracksites in the world; however, no behavioral studies have been conducted with them. This paper examines the association of invertebrate traces, avian footprints, and small, enigmatic elongate and double-oval traces from silicone casts (KS001 and KS064) taken from two specimens from the Haman Formation near Jinju. Two distinct types of bird tracks are present: a larger type with a well-defined hallux impression on the majority of the tracks, Koreanaornis isp., and a smaller type without a clear hallux impression, K. hamanensis. Elongate traces interpreted to be peck marks and double-oval traces interpreted to be probe marks were found on KS001. The peck marks range from 4.0 to 11.2 mm long and average 7.6 mm in width. There are two distinct morphologies of probe marks which may represent different species or genera of birds. The large probe mark is 6.9 mm long and 2.9 mm wide, whereas the smaller probe marks are 4.5 mm long by 2.2 mm wide and 5.7 mm long by 3.0 mm wide, respectively. Invertebrate traces associated with the bird tracks and feeding traces include Cochlichnus, Steinichnus, and Arenicolites. This represents the first report of peck marks from a fossil bird track locality.
Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over t... more Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser's ability to concentrate very high flux rates both at the macroscopic and microscopic levels results in specimens fluorescing in ways a standard UV bulb cannot induce. Presented here are five paleontological case histories that illustrate the technique across a broad range of specimens and scales. Novel uses such as back-lighting opaque specimens to reveal detail and detection of specimens completely obscured by matrix are highlighted in these examples. The recent cost reductions in medium-power short wavelength lasers and use of standard photographic filters has now made this technique widely accessible to researchers. This technology has the potential to automate multiple aspects of paleontolog...
ABSTRACT An issue with collecting modern bird tracks is the difficulty in connecting video footag... more ABSTRACT An issue with collecting modern bird tracks is the difficulty in connecting video footage and photographs to tracks produced and the environmental conditions at the time of track production. A new experimental setup using a collapsible tray ~123 cm by ~72 cm and ~4 cm deep, a monopod ~150 cm tall, and a digital video camera, captures tracemaker, trace, and behavior all at once. The tray contains sediment that can be wetted to produce different types of media (=substrate) consistency, which can be measured before and after track production. This experimental setup is portable and can fit inside a small car. The experimental setup can be used in laboratory settings, controlled outdoor settings (e.g., aviary or coop), and uncontrolled natural settings (e.g., on a river bank or along a lakeshore). Several track-making experiments were performed to test this setup using domestic chickens (Gallus gallus) to examine the variation of track morphology with media consistency and type. An experiment was also performed using Mourning Doves (Zenaida macrocura) to test if the tray can be used in natural, uncontrolled settings. The results of the controlled experiment using G. gallus indicate that the finer the sediment size, the better detail is preserved—in coarse sand, no pad impressions are preserved at all, whereas in medium sand, fine sand, and mud, pad impressions are preserved. In mud, scale and claw impressions are also preserved. In dry sediment the digit impressions were significantly longer and wider than the digit impressions of saturated and moist sediment, and ended in blunt, rounded tips. In saturated sediment, the sediment was too elastic to hold fine detail, however, the digit impressions tapered to points. In wet and moist sediments, the potential for pad impression preservation was high, however, preservation of such features was less likely if the sediment became too dry. Behaviors observed in the controlled experimental setup included sinuous walking, walking, running, start-stop walking, landing, and takeoff trackways. Start-stop walking did not produce side-by-side tracks and was the result of a bird pausing in midstride. Takeoff and landing behaviors also did not necessarily produce side-by-side tracks. Behaviors observed in the natural settings included landing, takeoff, feeding, and defensive charging.
The Lower Cretaceous Haman Formation of the Republic of Korea has yielded several localities with... more The Lower Cretaceous Haman Formation of the Republic of Korea has yielded several localities with thousands of dinosaur, bird, and pterosaur tracks. One such tracksite is found at the Gyeongsangnam-do Institute of Science Education (GISE) in Jinju, Republis of Korea. More than 1000 bird tracks are exposed on a single bedding plane, and thousands more are found in smaller float blocks on exhibit around the museum or in storage. The morphologic and behavioral diversity is extremely high; there are more than seven different morphologies described herein, with behaviors ranging from feeding--including pecking, probing, predator-prey interactions, and scything traces--to landing and running. Arcuate traces and associated webbed-footed trackways are identical to scything feeding traces produced by the extant black-faced spoonbill (Palatea minor). Individual peck and probe marks have also been reported, and clustered probing has been observed. The behaviors at this site are strikingly modern in respect to morphology and diversity, indicating that ornithurine birds had a very modern set of behaviors and anatomy. The high morphologic diversity of track morphotypes indicates that Early Cretaceous ornithurine birds were actually very diverse, compared to previous assumptions based on the body fossil record, which is dominated by enantiornithines.
Proceedings of the National Academy of Sciences, 2010
Reply to Brougham and Brusatte: Overall anatomy confirms posture and flight model offers insight ... more Reply to Brougham and Brusatte: Overall anatomy confirms posture and flight model offers insight into the evolution of bird flight Brougham and Brusatte (1) agree with us that Microraptor was an arboreal glider but disagree with the posture of our model's hind limbs (1). They offer no suggestion for an alternative, other than the implied parasagittal posture of a typical dromaeosaur, which we showed was aerodynamically and mechanically unlikely (2). They cast doubt on the sprawled (abducted) hind-limb posture of our reconstruction-a key feature-by claiming that dromaeosaurid hips have structures (antitrochanters and supracetabular crests) that prevent abduction and that our specimen was too flattened to see such features. Whereas large dromaeosaurids may possess such structures, apparently, in small ones such as Microraptor, these structures are greatly reduced (3). The authors (1) misrepresent the small dromaeosaurid Hesperonychus as providing evidence against a sprawling posture, when the original description of Hesperonychus specifically mentions the lack of processes on the acetabulum preventing abduction and states that the "acetabulum opens dorsolaterally rather than laterally. . . suggesting the ability to partially abduct the hind limbs. This morphology is of interest in light of proposals that Microraptor gui abducted its feathered hind limbs to act as airfoils" (reference 4 in ref. 1). Their crushed flat claim is based on examining an incomplete cast (1). They did not examine the original fossil or its X-rays and X-ray computed tomography scans, and thus made a judgment using incomplete information. This Microraptor pelvis has been figured and described (4), and a complete 3D cast of the specimen is also available in our collections for examination. Furthermore, our pelvic morphology was checked against dozens of other specimens (as stated in ref. 2). We stand by our anatomical observations and are currently describing this specimen, along with other material, which will support the accuracy of our interpretation.
... Deutliche Unterschiede im Winkel des Trochlearbogens und dem Winkel der Divarikation konnten ... more ... Deutliche Unterschiede im Winkel des Trochlearbogens und dem Winkel der Divarikation konnten mit Vogel-Morphotypen wie Küstenvögeln, Watvögeln, am Boden nach Nahrung suchenden ... Northern Cardinal 55 175 1 50 56 162 2 58 57 170 3 39 58 174 4 45 59 175 5 44 60 ...
The record of Paleogene bird traces is quite scarce, especially when compared with the Mesozoic. ... more The record of Paleogene bird traces is quite scarce, especially when compared with the Mesozoic. Avian tracks have been reported mainly from western North America and the Middle East, with some sites also present in Europe and Sumatra. Here the first record of Eocene bird tracks from East Asia is reported. The track bearing level is recorded at the upper part of the Huayong Formation (lower Eocene), one of the continental units of the Sanshui Basin. More than 350 footprints were documented fromthree collected slabs. Many footprints were found in trackways, five morphotypeswere identified and assigned to four ichnotaxon: Gruipeda sp., Aviadactyla sp., Avipeda sp., and Fuscinapeda sp. The ichnotaxonomical identifications are supported by canonical variate analysis (CVA) based on the better preserved traces. These surfaces show a varied ichnofaunal assemblage composed of small and mediumshorebirds, large “game” birds, crane-like birds and heron-like birds, providing a more complete picture than was previously known of Early Eocene avian faunal assemblages in Asia.
Proceedings of The National Academy of Sciences, 2010
We suggest that some of the most avian dromaeosaurs, such as Sinornithosaurus, were venomous, and... more We suggest that some of the most avian dromaeosaurs, such as Sinornithosaurus, were venomous, and propose an ecological model for that taxon based on its unusual dentition and other cranial features including grooved teeth, a possible pocket for venom glands, and a groove leading from that pocket to the exposed bases of the teeth. These features are all analogous to the venomous morphology of lizards. Sinornithosaurus and related dromaeosaurs probably fed on the abundant birds of the Jehol forests during the Early Cretaceous in northeastern China. dromaeosaur | Jehol | grooved fangs | venomous delivery system O ne of the more bizarre innovations in organismic evolution is the ability to manufacture toxic substances. Venomous taxa occur in a variety of ecologic settings and include insects, lizards, snakes, and mammals (1-5). Clearly, venom has evolved numerous times in many different lineages employing various delivery apparatus. A combination of morphological and molecular research has recently shown that venomous taxa are far more widespread and primitive within tetrapod lineages than had previously been suspected (6).
Proceedings of The National Academy of Sciences, 2010
Fossils of the remarkable dromaeosaurid Microraptor gui and relatives clearly show well-developed... more Fossils of the remarkable dromaeosaurid Microraptor gui and relatives clearly show well-developed flight feathers on the hind limbs as well as the front limbs. No modern vertebrate has hind limbs functioning as independent, fully developed wings; so, lacking a living example, little agreement exists on the functional morphology or likely flight configuration of the hindwing. Using a detailed reconstruction based on the actual skeleton of one individual, cast in the round, we developed light-weight, three-dimensional physical models and performed glide tests with anatomically reasonable hindwing configurations. Models were tested with hindwings abducted and extended laterally, as well as with a previously described biplane configuration. Although the hip joint requires the hindwing to have at least 20°of negative dihedral (anhedral), all configurations were quite stable gliders. Glide angles ranged from 3°to 21°with a mean estimated equilibrium angle of 13.7°, giving a lift to drag ratio of 4.1:1 and a lift coefficient of 0.64. The abducted hindwing model's equilibrium glide speed corresponds to a glide speed in the living animal of 10.6 m·s −1 . Although the biplane model glided almost as well as the other models, it was structurally deficient and required an unlikely weight distribution (very heavy head) for stable gliding. Our model with laterally abducted hindwings represents a biologically and aerodynamically reasonable configuration for this four-winged gliding animal. M. gui's feathered hindwings, although effective for gliding, would have seriously hampered terrestrial locomotion. biomechanics | bird flight evolution | feathered dinosaurs | model tests | tetrapteryx E vidence now exists that should settle the long-running debate over a ground-up origin of avian flight vs. the evolution of avian flight from a trees-down glider. This evidence shows that the protoavian was arboreal (1) rather than a terrestrial cursor as many have suggested (2-4). The leading protagonist in this controversy is presently a dromaeosaur, Microraptor gui, with a fully formed hind wing that is closely similar to its completely avian forewing (5), having elongate, aerodynamically advanced "primary feathers" coming off the metatarsi (5). There seems little reason to doubt the aerodynamic function of the hindwing, but there has been controversy over exactly how it was arranged and used for flight. We decided to address this problem by creating and testing models that closely replicate the anatomical features preserved in the now numerous fossils of Microraptor and its close relatives (discussed in SI Text).
There have been a number of studies on the claws of Mesozoic birds, largely driven by interest in... more There have been a number of studies on the claws of Mesozoic birds, largely driven by interest in the habitat of Archaeopteryx. Many Mesozoic avians have large, well formed manual claws, largely absent in contemporary birds. Juvenile hoatzins are the only living birds with claws that are large enough to be generally functional, but not equivalent to those of Mesozoic birds. When birds developed an effective backstroke permitting easy ascent from flat surfaces, the need for manual claws disappeared, which would suggest that they were primarily used for climbing tree trunks and had little function in prey capture. This hypothesis has both phylogenetic and functional implications. The numerous claw studies to date are based primarily on measurements taken of the bony core, all that is usually preserved in fossils. Examination of contemporary birds shows that this is a poor estimator of the size and shape of the horny sheath that actually forms the functional claw. The discovery of vast numbers of exceptionally preserved fossil birds from the Late Jurassic and Early Cretaceous of China means that we now have an opportunity to compare actual horny claw data from the earliest birds with that of modern birds and test hypotheses on climbing, terrestrial activity, and predation.
Early Cretaceous bird tracks have been found in North America, China, South Korea and Japan. The ... more Early Cretaceous bird tracks have been found in North America, China, South Korea and Japan. The identification of many of the tracemakers as ornithurine birds rather than enantiornithines is supported by the overall morphological and behavioural similarity to tracks left by modern shorebirds, as well as indicators of ground-to-air takeoff. Various morphologies found in Asia, including web-footed, anisodactyl and zygodactyl tracks, indicate a very high diversity of birds. The most common are anisodactyl shorebird-like tracks represented by Aquatilavipes, Koreanaornis, Ignotornis and others. Such ichnogenera as Aquatilavipes and, more recently, Koreanaornis, have been discovered on both sides of the Pacific Ocean. Koreanaornis is more specific in its distinguishing criteria, unlike Aquatilavipes, which may be a taxonomic wastebasket. The appearance of the same ichnogenera across great distances implies that either ornithurine birds evolved long-distance migration in or before the Early Cretaceous, or that ornithurine birds arose before the Cretaceous. Molecular data support an Early Cretaceous origin for modern bird families, and shorebird-like tracks have been reported from very near the Jurassic–Cretaceous boundary. Shorebird-like trackways have been reported from the Early Jurassic of Africa and North America (e.g. Trisaurpodiscus), suggesting an even earlier origin for ornithurine birds.
Hierarchy theory recognises that ecological and evolutionary units occur in a nested and intercon... more Hierarchy theory recognises that ecological and evolutionary units occur in a nested and interconnected hierarchical system, with cascading effects occurring between hierarchical levels. Different biological disciplines have routinely come into conflict over the primacy of different forcing mechanisms behind evolutionary and ecological change. These disconnects arise partly from differences in perspective (with some researchers favouring ecological forcing mechanisms while others favour developmental/historical mechanisms), as well as differences in the temporal framework in which workers operate. In particular, long-term palaeontological data often show that large-scale (macro) patterns of evolution are predominantly dictated by shifts in the abiotic environment, while short-term (micro) modern biological studies stress the importance of biotic interactions. We propose that thinking about ecological and evolutionary interactions in a hierarchical framework is a fruitful way to resolve these conflicts. Hierarchy theory suggests that changes occurring at lower hierarchical levels can have unexpected, complex effects at higher scales due to emergent interactions between simple systems. In this way, patterns occurring on short-and long-term time scales are equally valid, as changes that are driven from lower levels will manifest in different forms at higher levels. We propose that the dual hierarchy framework fits well with our current understanding of evolutionary and ecological theory. Furthermore, we describe how this framework can be used to understand major extinction events better. Multi-generational attritional loss of reproductive fitness (MALF) has recently been proposed as the primary mechanism behind extinction events, whereby extinction is explainable solely through processes that result in extirpation of populations through a shutdown of reproduction. While not necessarily explicit, the push to explain extinction through solely population-level dynamics could be used to suggest that environmentally mediated patterns of extinction or slowed speciation across geological time are largely artefacts of poor preservation or a coarse temporal scale. We demonstrate how MALF fits into a hierarchical framework, showing that MALF can be a primary forcing mechanism at lower scales that still results in differential survivorship patterns at the species and clade level which vary depending upon the initial environmental forcing mechanism. Thus, even if MALF is the primary mechanism of extinction across all mass extinction events, the primary environmental cause of these events will still affect the system and result in differential responses. Therefore, patterns at both temporal scales are relevant.
In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beak... more In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beaked bird from the Early Cretaceous Jehol Biota in northeastern China. Various soft tissues are visualized and interpreted through the use of laser-stimulated fluorescence, providing much novel anatomical information about this early bird, specifically reticulate scales covering the feet, and the well-developed and robust pro- and postpatagium. We also include a direct comparison between the forelimb soft tissues of Confuciusornis and modern avian patagia. Furthermore, apparently large, fleshy phalangeal pads are preserved on the feet. The reticulate scales, robust phalangeal pads as well as the highly recurved pedal claws strongly support Confuciusornis as an arboreal bird. Reticulate scales are more rounded than scutate scales and do not overlap, thus allowing for more flexibility in the toe. The extent of the pro- and postpatagium and the robust primary feather rachises are evidence that Confuciusornis was capable of powered flight, contrary to previous reports suggesting otherwise. A unique avian wing shape is also reconstructed based on plumage preserved. These soft tissues combined indicate an arboreal bird with the capacity for short-term (non-migratory) flight, and suggest that, although primitive, Confuciusornis already possessed many relatively advanced avian anatomical characteristics.
The bird track localities of the Republic of Korea are among the richest and most diverse avian t... more The bird track localities of the Republic of Korea are among the richest and most diverse avian tracksites in the world; however, no behavioral studies have been conducted with them. This paper examines the association of invertebrate traces, avian footprints, and small, enigmatic elongate and double-oval traces from silicone casts (KS001 and KS064) taken from two specimens from the Haman Formation near Jinju. Two distinct types of bird tracks are present: a larger type with a well-defined hallux impression on the majority of the tracks, Koreanaornis isp., and a smaller type without a clear hallux impression, K. hamanensis. Elongate traces interpreted to be peck marks and double-oval traces interpreted to be probe marks were found on KS001. The peck marks range from 4.0 to 11.2 mm long and average 7.6 mm in width. There are two distinct morphologies of probe marks which may represent different species or genera of birds. The large probe mark is 6.9 mm long and 2.9 mm wide, whereas the smaller probe marks are 4.5 mm long by 2.2 mm wide and 5.7 mm long by 3.0 mm wide, respectively. Invertebrate traces associated with the bird tracks and feeding traces include Cochlichnus, Steinichnus, and Arenicolites. This represents the first report of peck marks from a fossil bird track locality.
Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over t... more Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser's ability to concentrate very high flux rates both at the macroscopic and microscopic levels results in specimens fluorescing in ways a standard UV bulb cannot induce. Presented here are five paleontological case histories that illustrate the technique across a broad range of specimens and scales. Novel uses such as back-lighting opaque specimens to reveal detail and detection of specimens completely obscured by matrix are highlighted in these examples. The recent cost reductions in medium-power short wavelength lasers and use of standard photographic filters has now made this technique widely accessible to researchers. This technology has the potential to automate multiple aspects of paleontolog...
ABSTRACT An issue with collecting modern bird tracks is the difficulty in connecting video footag... more ABSTRACT An issue with collecting modern bird tracks is the difficulty in connecting video footage and photographs to tracks produced and the environmental conditions at the time of track production. A new experimental setup using a collapsible tray ~123 cm by ~72 cm and ~4 cm deep, a monopod ~150 cm tall, and a digital video camera, captures tracemaker, trace, and behavior all at once. The tray contains sediment that can be wetted to produce different types of media (=substrate) consistency, which can be measured before and after track production. This experimental setup is portable and can fit inside a small car. The experimental setup can be used in laboratory settings, controlled outdoor settings (e.g., aviary or coop), and uncontrolled natural settings (e.g., on a river bank or along a lakeshore). Several track-making experiments were performed to test this setup using domestic chickens (Gallus gallus) to examine the variation of track morphology with media consistency and type. An experiment was also performed using Mourning Doves (Zenaida macrocura) to test if the tray can be used in natural, uncontrolled settings. The results of the controlled experiment using G. gallus indicate that the finer the sediment size, the better detail is preserved—in coarse sand, no pad impressions are preserved at all, whereas in medium sand, fine sand, and mud, pad impressions are preserved. In mud, scale and claw impressions are also preserved. In dry sediment the digit impressions were significantly longer and wider than the digit impressions of saturated and moist sediment, and ended in blunt, rounded tips. In saturated sediment, the sediment was too elastic to hold fine detail, however, the digit impressions tapered to points. In wet and moist sediments, the potential for pad impression preservation was high, however, preservation of such features was less likely if the sediment became too dry. Behaviors observed in the controlled experimental setup included sinuous walking, walking, running, start-stop walking, landing, and takeoff trackways. Start-stop walking did not produce side-by-side tracks and was the result of a bird pausing in midstride. Takeoff and landing behaviors also did not necessarily produce side-by-side tracks. Behaviors observed in the natural settings included landing, takeoff, feeding, and defensive charging.
The Lower Cretaceous Haman Formation of the Republic of Korea has yielded several localities with... more The Lower Cretaceous Haman Formation of the Republic of Korea has yielded several localities with thousands of dinosaur, bird, and pterosaur tracks. One such tracksite is found at the Gyeongsangnam-do Institute of Science Education (GISE) in Jinju, Republis of Korea. More than 1000 bird tracks are exposed on a single bedding plane, and thousands more are found in smaller float blocks on exhibit around the museum or in storage. The morphologic and behavioral diversity is extremely high; there are more than seven different morphologies described herein, with behaviors ranging from feeding--including pecking, probing, predator-prey interactions, and scything traces--to landing and running. Arcuate traces and associated webbed-footed trackways are identical to scything feeding traces produced by the extant black-faced spoonbill (Palatea minor). Individual peck and probe marks have also been reported, and clustered probing has been observed. The behaviors at this site are strikingly modern in respect to morphology and diversity, indicating that ornithurine birds had a very modern set of behaviors and anatomy. The high morphologic diversity of track morphotypes indicates that Early Cretaceous ornithurine birds were actually very diverse, compared to previous assumptions based on the body fossil record, which is dominated by enantiornithines.
Proceedings of the National Academy of Sciences, 2010
Reply to Brougham and Brusatte: Overall anatomy confirms posture and flight model offers insight ... more Reply to Brougham and Brusatte: Overall anatomy confirms posture and flight model offers insight into the evolution of bird flight Brougham and Brusatte (1) agree with us that Microraptor was an arboreal glider but disagree with the posture of our model's hind limbs (1). They offer no suggestion for an alternative, other than the implied parasagittal posture of a typical dromaeosaur, which we showed was aerodynamically and mechanically unlikely (2). They cast doubt on the sprawled (abducted) hind-limb posture of our reconstruction-a key feature-by claiming that dromaeosaurid hips have structures (antitrochanters and supracetabular crests) that prevent abduction and that our specimen was too flattened to see such features. Whereas large dromaeosaurids may possess such structures, apparently, in small ones such as Microraptor, these structures are greatly reduced (3). The authors (1) misrepresent the small dromaeosaurid Hesperonychus as providing evidence against a sprawling posture, when the original description of Hesperonychus specifically mentions the lack of processes on the acetabulum preventing abduction and states that the "acetabulum opens dorsolaterally rather than laterally. . . suggesting the ability to partially abduct the hind limbs. This morphology is of interest in light of proposals that Microraptor gui abducted its feathered hind limbs to act as airfoils" (reference 4 in ref. 1). Their crushed flat claim is based on examining an incomplete cast (1). They did not examine the original fossil or its X-rays and X-ray computed tomography scans, and thus made a judgment using incomplete information. This Microraptor pelvis has been figured and described (4), and a complete 3D cast of the specimen is also available in our collections for examination. Furthermore, our pelvic morphology was checked against dozens of other specimens (as stated in ref. 2). We stand by our anatomical observations and are currently describing this specimen, along with other material, which will support the accuracy of our interpretation.
... Deutliche Unterschiede im Winkel des Trochlearbogens und dem Winkel der Divarikation konnten ... more ... Deutliche Unterschiede im Winkel des Trochlearbogens und dem Winkel der Divarikation konnten mit Vogel-Morphotypen wie Küstenvögeln, Watvögeln, am Boden nach Nahrung suchenden ... Northern Cardinal 55 175 1 50 56 162 2 58 57 170 3 39 58 174 4 45 59 175 5 44 60 ...
The record of Paleogene bird traces is quite scarce, especially when compared with the Mesozoic. ... more The record of Paleogene bird traces is quite scarce, especially when compared with the Mesozoic. Avian tracks have been reported mainly from western North America and the Middle East, with some sites also present in Europe and Sumatra. Here the first record of Eocene bird tracks from East Asia is reported. The track bearing level is recorded at the upper part of the Huayong Formation (lower Eocene), one of the continental units of the Sanshui Basin. More than 350 footprints were documented fromthree collected slabs. Many footprints were found in trackways, five morphotypeswere identified and assigned to four ichnotaxon: Gruipeda sp., Aviadactyla sp., Avipeda sp., and Fuscinapeda sp. The ichnotaxonomical identifications are supported by canonical variate analysis (CVA) based on the better preserved traces. These surfaces show a varied ichnofaunal assemblage composed of small and mediumshorebirds, large “game” birds, crane-like birds and heron-like birds, providing a more complete picture than was previously known of Early Eocene avian faunal assemblages in Asia.
Proceedings of The National Academy of Sciences, 2010
We suggest that some of the most avian dromaeosaurs, such as Sinornithosaurus, were venomous, and... more We suggest that some of the most avian dromaeosaurs, such as Sinornithosaurus, were venomous, and propose an ecological model for that taxon based on its unusual dentition and other cranial features including grooved teeth, a possible pocket for venom glands, and a groove leading from that pocket to the exposed bases of the teeth. These features are all analogous to the venomous morphology of lizards. Sinornithosaurus and related dromaeosaurs probably fed on the abundant birds of the Jehol forests during the Early Cretaceous in northeastern China. dromaeosaur | Jehol | grooved fangs | venomous delivery system O ne of the more bizarre innovations in organismic evolution is the ability to manufacture toxic substances. Venomous taxa occur in a variety of ecologic settings and include insects, lizards, snakes, and mammals (1-5). Clearly, venom has evolved numerous times in many different lineages employing various delivery apparatus. A combination of morphological and molecular research has recently shown that venomous taxa are far more widespread and primitive within tetrapod lineages than had previously been suspected (6).
Proceedings of The National Academy of Sciences, 2010
Fossils of the remarkable dromaeosaurid Microraptor gui and relatives clearly show well-developed... more Fossils of the remarkable dromaeosaurid Microraptor gui and relatives clearly show well-developed flight feathers on the hind limbs as well as the front limbs. No modern vertebrate has hind limbs functioning as independent, fully developed wings; so, lacking a living example, little agreement exists on the functional morphology or likely flight configuration of the hindwing. Using a detailed reconstruction based on the actual skeleton of one individual, cast in the round, we developed light-weight, three-dimensional physical models and performed glide tests with anatomically reasonable hindwing configurations. Models were tested with hindwings abducted and extended laterally, as well as with a previously described biplane configuration. Although the hip joint requires the hindwing to have at least 20°of negative dihedral (anhedral), all configurations were quite stable gliders. Glide angles ranged from 3°to 21°with a mean estimated equilibrium angle of 13.7°, giving a lift to drag ratio of 4.1:1 and a lift coefficient of 0.64. The abducted hindwing model's equilibrium glide speed corresponds to a glide speed in the living animal of 10.6 m·s −1 . Although the biplane model glided almost as well as the other models, it was structurally deficient and required an unlikely weight distribution (very heavy head) for stable gliding. Our model with laterally abducted hindwings represents a biologically and aerodynamically reasonable configuration for this four-winged gliding animal. M. gui's feathered hindwings, although effective for gliding, would have seriously hampered terrestrial locomotion. biomechanics | bird flight evolution | feathered dinosaurs | model tests | tetrapteryx E vidence now exists that should settle the long-running debate over a ground-up origin of avian flight vs. the evolution of avian flight from a trees-down glider. This evidence shows that the protoavian was arboreal (1) rather than a terrestrial cursor as many have suggested (2-4). The leading protagonist in this controversy is presently a dromaeosaur, Microraptor gui, with a fully formed hind wing that is closely similar to its completely avian forewing (5), having elongate, aerodynamically advanced "primary feathers" coming off the metatarsi (5). There seems little reason to doubt the aerodynamic function of the hindwing, but there has been controversy over exactly how it was arranged and used for flight. We decided to address this problem by creating and testing models that closely replicate the anatomical features preserved in the now numerous fossils of Microraptor and its close relatives (discussed in SI Text).
There have been a number of studies on the claws of Mesozoic birds, largely driven by interest in... more There have been a number of studies on the claws of Mesozoic birds, largely driven by interest in the habitat of Archaeopteryx. Many Mesozoic avians have large, well formed manual claws, largely absent in contemporary birds. Juvenile hoatzins are the only living birds with claws that are large enough to be generally functional, but not equivalent to those of Mesozoic birds. When birds developed an effective backstroke permitting easy ascent from flat surfaces, the need for manual claws disappeared, which would suggest that they were primarily used for climbing tree trunks and had little function in prey capture. This hypothesis has both phylogenetic and functional implications. The numerous claw studies to date are based primarily on measurements taken of the bony core, all that is usually preserved in fossils. Examination of contemporary birds shows that this is a poor estimator of the size and shape of the horny sheath that actually forms the functional claw. The discovery of vast numbers of exceptionally preserved fossil birds from the Late Jurassic and Early Cretaceous of China means that we now have an opportunity to compare actual horny claw data from the earliest birds with that of modern birds and test hypotheses on climbing, terrestrial activity, and predation.
Early Cretaceous bird tracks have been found in North America, China, South Korea and Japan. The ... more Early Cretaceous bird tracks have been found in North America, China, South Korea and Japan. The identification of many of the tracemakers as ornithurine birds rather than enantiornithines is supported by the overall morphological and behavioural similarity to tracks left by modern shorebirds, as well as indicators of ground-to-air takeoff. Various morphologies found in Asia, including web-footed, anisodactyl and zygodactyl tracks, indicate a very high diversity of birds. The most common are anisodactyl shorebird-like tracks represented by Aquatilavipes, Koreanaornis, Ignotornis and others. Such ichnogenera as Aquatilavipes and, more recently, Koreanaornis, have been discovered on both sides of the Pacific Ocean. Koreanaornis is more specific in its distinguishing criteria, unlike Aquatilavipes, which may be a taxonomic wastebasket. The appearance of the same ichnogenera across great distances implies that either ornithurine birds evolved long-distance migration in or before the Early Cretaceous, or that ornithurine birds arose before the Cretaceous. Molecular data support an Early Cretaceous origin for modern bird families, and shorebird-like tracks have been reported from very near the Jurassic–Cretaceous boundary. Shorebird-like trackways have been reported from the Early Jurassic of Africa and North America (e.g. Trisaurpodiscus), suggesting an even earlier origin for ornithurine birds.
Uploads
Papers by Amanda Falk
have been reported mainly from western North America and the Middle East, with some sites also present in
Europe and Sumatra. Here the first record of Eocene bird tracks from East Asia is reported. The track bearing
level is recorded at the upper part of the Huayong Formation (lower Eocene), one of the continental units of
the Sanshui Basin.
More than 350 footprints were documented fromthree collected slabs. Many footprints were found in trackways,
five morphotypeswere identified and assigned to four ichnotaxon: Gruipeda sp., Aviadactyla sp., Avipeda sp., and
Fuscinapeda sp. The ichnotaxonomical identifications are supported by canonical variate analysis (CVA) based
on the better preserved traces. These surfaces show a varied ichnofaunal assemblage composed of small and
mediumshorebirds, large “game” birds, crane-like birds and heron-like birds, providing a more complete picture
than was previously known of Early Eocene avian faunal assemblages in Asia.
have been reported mainly from western North America and the Middle East, with some sites also present in
Europe and Sumatra. Here the first record of Eocene bird tracks from East Asia is reported. The track bearing
level is recorded at the upper part of the Huayong Formation (lower Eocene), one of the continental units of
the Sanshui Basin.
More than 350 footprints were documented fromthree collected slabs. Many footprints were found in trackways,
five morphotypeswere identified and assigned to four ichnotaxon: Gruipeda sp., Aviadactyla sp., Avipeda sp., and
Fuscinapeda sp. The ichnotaxonomical identifications are supported by canonical variate analysis (CVA) based
on the better preserved traces. These surfaces show a varied ichnofaunal assemblage composed of small and
mediumshorebirds, large “game” birds, crane-like birds and heron-like birds, providing a more complete picture
than was previously known of Early Eocene avian faunal assemblages in Asia.