1
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Booth W, Levine BA, Corush JB, Davis MA, Dwyer Q, De Plecker R, Schuett GW. Discovery of facultative parthenogenesis in a new world crocodile. Biol Lett 2023; 19:20230129. [PMID: 37282490 DOI: 10.1098/rsbl.2023.0129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023] Open
Abstract
Over the past two decades, there has been an astounding growth in the documentation of vertebrate facultative parthenogenesis (FP). This unusual reproductive mode has been documented in birds, non-avian reptiles-specifically lizards and snakes-and elasmobranch fishes. Part of this growth among vertebrate taxa is attributable to awareness of the phenomenon itself and advances in molecular genetics/genomics and bioinformatics, and as such our understanding has developed considerably. Nonetheless, questions remain as to its occurrence outside of these vertebrate lineages, most notably in Chelonia (turtles) and Crocodylia (crocodiles, alligators and gharials). The latter group is particularly interesting because unlike all previously documented cases of FP in vertebrates, crocodilians lack sex chromosomes and sex determination is controlled by temperature. Here, using whole-genome sequencing data, we provide, to our knowledge, the first evidence of FP in a crocodilian, the American crocodile, Crocodylus acutus. The data support terminal fusion automixis as the reproductive mechanism; a finding which suggests a common evolutionary origin of FP across reptiles, crocodilians and birds. With FP now documented in the two main branches of extant archosaurs, this discovery offers tantalizing insights into the possible reproductive capabilities of the extinct archosaurian relatives of crocodilians and birds, notably members of Pterosauria and Dinosauria.
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Affiliation(s)
- Warren Booth
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
- Chiricahua Desert Museum, Rodeo, NM 88056, USA
| | - Brenna A Levine
- Chiricahua Desert Museum, Rodeo, NM 88056, USA
- Department of Biology, Kean University, Union, NJ 07083, USA
| | - Joel B Corush
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Illinois, IL 61820, USA
| | - Mark A Davis
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Illinois, IL 61820, USA
| | - Quetzal Dwyer
- Reptilandia Reptile Lagoon, Johnson City, TX 78636, USA
| | - Roel De Plecker
- Parque Reptilandia, Dominical 5000, Puntarenas Province, 11902, Costa Rica
| | - Gordon W Schuett
- Chiricahua Desert Museum, Rodeo, NM 88056, USA
- Department of Biology, Neuroscience Institute, Georgia State University, Atlanta, GA 30302, USA
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2
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Turner ML, Gatesy SM. Inner workings of the alligator ankle reveal the mechanistic origins of archosaur locomotor diversity. J Anat 2023; 242:592-606. [PMID: 36484567 PMCID: PMC10008286 DOI: 10.1111/joa.13801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 11/17/2022] [Accepted: 11/20/2022] [Indexed: 12/13/2022] Open
Abstract
Major transformations in the locomotor system of archosaurs (a major clade of reptiles including birds, crocodiles, dinosaurs, and pterosaurs) were accompanied by significant modifications to ankle anatomy. How the evolution of such a complex multi-joint structure is related to shifts in ankle function and locomotor diversity across this clade remains unclear and weakly grounded in extant experimental data. Here, we used X-ray Reconstruction of Moving Morphology to reconstruct skeletal motion and quantify the sources of three-dimensional ankle mobility in the American alligator, a species that retains the ancestral archosaur ankle structure. We then applied the observed relationships between joint excursion and locomotor behaviors to predict ankle function in extinct archosaurs. High-resolution reconstructions of Alligator skeletal movement revealed previously unseen regionalized coordination among joints responsible for overall ankle rotation. Differences in joint contributions between maneuvers and steady walking parallel transitions in mobility inferred from the ankle structure of fossil taxa in lineages with more erect hind limb postures. Key ankle structures related to ankle mobility were identified in the alligator, which permitted the characterization of ancestral archosaur ankle function. Modifications of these structures provide morphological evidence for functional convergence among sublineages of bird-line and crocodylian-line archosaurs. Using the dynamic insight into the internal sources of Alligator ankle mobility and trends among locomotor modes, we trace anatomical shifts and propose a mechanistic hypothesis for the evolution of ankle structure and function across Archosauria.
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Affiliation(s)
- Morgan L Turner
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, Rhode Island, USA.,Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, USA
| | - Stephen M Gatesy
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, Rhode Island, USA
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3
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Natarajan C, Signore AV, Bautista NM, Hoffmann FG, Tame JRH, Fago A, Storz JF. Evolution and molecular basis of a novel allosteric property of crocodilian hemoglobin. Curr Biol 2023; 33:98-108.e4. [PMID: 36549299 PMCID: PMC9839640 DOI: 10.1016/j.cub.2022.11.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/25/2022] [Accepted: 11/22/2022] [Indexed: 12/24/2022]
Abstract
The extraordinary breath-hold diving capacity of crocodilians has been ascribed to a unique mode of allosterically regulating hemoglobin (Hb)-oxygenation in circulating red blood cells. We investigated the origin and mechanistic basis of this novel biochemical phenomenon by performing directed mutagenesis experiments on resurrected ancestral Hbs. Comparisons of Hb function between the common ancestor of archosaurs (the group that includes crocodilians and birds) and the last common ancestor of modern crocodilians revealed that regulation of Hb-O2 affinity via allosteric binding of bicarbonate ions represents a croc-specific innovation that evolved in combination with the loss of allosteric regulation by ATP binding. Mutagenesis experiments revealed that evolution of the novel allosteric function in crocodilians and the concomitant loss of ancestral function were not mechanistically coupled and were caused by different sets of substitutions. The gain of bicarbonate sensitivity in crocodilian Hb involved the direct effect of few amino acid substitutions at key sites in combination with indirect effects of numerous other substitutions at structurally disparate sites. Such indirect interaction effects suggest that evolution of the novel protein function was conditional on neutral mutations that produced no adaptive benefit when they first arose but that contributed to a permissive background for subsequent function-altering mutations at other sites. Due to the context dependence of causative substitutions, the unique allosteric properties of crocodilian Hb cannot be easily transplanted into divergent homologs of other species.
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Affiliation(s)
| | - Anthony V Signore
- School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA
| | - Naim M Bautista
- School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA
| | - Federico G Hoffmann
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Mississippi State, MS 39762, USA; Institute for Genomics, Biocomputing, and Biotechnology, Mississippi State University, Mississippi State, MS 39762, USA
| | - Jeremy R H Tame
- Drug Design Laboratory, Yokohama City University, Yokohama 230-0045, Japan
| | - Angela Fago
- Zoophysiology, Department of Bioscience, Aarhus University, DK-8000 Aarhus, Denmark
| | - Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA.
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4
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Cuff AR, Demuth OE, Michel K, Otero A, Pintore R, Polet DT, Wiseman ALA, Hutchinson JR. Walking-and Running and Jumping-with Dinosaurs and Their Cousins, Viewed Through the Lens of Evolutionary Biomechanics. Integr Comp Biol 2022; 62:icac049. [PMID: 35595475 DOI: 10.1093/icb/icac049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Archosauria diversified throughout the Triassic Period before experiencing two mass extinctions near its end ∼201 Mya, leaving only the crocodile-lineage (Crocodylomorpha) and bird-lineage (Dinosauria) as survivors; along with the pterosaurian flying reptiles. About 50 years ago, the "locomotor superiority hypothesis" (LSH) proposed that dinosaurs ultimately dominated by the Early Jurassic Period because their locomotion was superior to other archosaurs'. This idea has been debated continuously since, with taxonomic and morphological analyses suggesting dinosaurs were "lucky" rather than surviving due to being biologically superior. However, the LSH has never been tested biomechanically. Here we present integration of experimental data from locomotion in extant archosaurs with inverse and predictive simulations of the same behaviours using musculoskeletal models, showing that we can reliably predict how extant archosaurs walk, run and jump. These simulations have been guiding predictive simulations of extinct archosaurs to estimate how they moved, and we show our progress in that endeavour. The musculoskeletal models used in these simulations can also be used for simpler analyses of form and function such as muscle moment arms, which inform us about more basic biomechanical similarities and differences between archosaurs. Placing all these data into an evolutionary and biomechanical context, we take a fresh look at the LSH as part of a critical review of competing hypotheses for why dinosaurs (and a few other archosaur clades) survived the Late Triassic extinctions. Early dinosaurs had some quantifiable differences in locomotor function and performance vs. some other archosaurs, but other derived dinosaurian features (e.g., metabolic or growth rates, ventilatory abilities) are not necessarily mutually exclusive from the LSH; or maybe even an opportunistic replacement hypothesis; in explaining dinosaurs' success.
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Affiliation(s)
- A R Cuff
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
- Human Anatomy Resource Centre, University of Liverpool, Liverpool, United Kingdom
| | - O E Demuth
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
- Department of Earth Sciences, University of Cambridge, United Kingdom
| | - K Michel
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
| | - A Otero
- CONICET - División Paleontología de Vertebrados, Facultad de Ciencias Naturales y Museo, Anexo Laboratorios, La Plata, Argentina
| | - R Pintore
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
- Mécanismes adaptatifs et évolution (MECADEV) / UMR 7179, CNRS / Muséum National d'Histoire Naturelle, France
| | - D T Polet
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
| | - A L A Wiseman
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
- McDonald Institute for Archaeological Research, University of Cambridge, United Kingdom
| | - J R Hutchinson
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, United Kingdom
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5
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Schachner ER, Diaz RE, Coke R, Echols S, Osborn ML, Hedrick BP. Architecture of the bronchial tree in Cuvier's dwarf caiman (Paleosuchus palpebrosus). Anat Rec (Hoboken) 2022; 305:3037-3054. [PMID: 35377558 DOI: 10.1002/ar.24919] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/25/2022] [Accepted: 03/09/2022] [Indexed: 01/16/2023]
Abstract
We imaged the lungs of five Cuvier's dwarf caiman (Paleosuchus palpebrosus) via computed tomography (CT) and micro-computed tomography (μCT) and compared these data to the lungs of the American alligator (Alligator mississippiensis). These data demonstrate anatomical commonalities between the lungs of P. palpebrosus and A. mississippiensis, and a few notable differences. The structural similarities are (a) a proximally narrow, distally widened, hook-shaped primary bronchus; (b) a cervical ventral bronchus that branches of the primary bronchus and immediately makes a hairpin turn toward the apex of the lung; (c) a sequential series of dorsobronchi arising from the primary bronchus caudal to the cervical ventral bronchus; (d) intraspecifically highly variable medial sequence of secondary airways; (e) sac-like laterobronchi; and (f) grossly dead-ended caudal group bronchi in the caudal and ventral aspects of the lung. The primary differences between the two taxa are in the overall number of large bronchi (fewer in P. palpebrosus), and the number of branches that contribute to the cardiac regions. Imaging data of both a live and deceased specimen under varying states (postprandial, fasting, total lung capacity, open to atmosphere) indicate that the caudal margin and position of the lungs shift craniocaudally relative to the vertebral column. These imaging data suggest that the smooth thoracic ceiling may be correlated to visceral movement during ventilation, but this hypothesis warrants validation. These results provide the scaffolding for future comparisons between crocodilians, for generating preliminary reconstructions of the ancestral crocodilian bronchial tree, and establishing new hypotheses of bronchial homology across Archosauria.
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Affiliation(s)
- Emma R Schachner
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Raul E Diaz
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
| | - Rob Coke
- San Antonio Zoo, San Antonio, Texas, USA
| | - Scott Echols
- The Medical Center for Birds, Oakley, California, USA
| | - Michelle L Osborn
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Brandon P Hedrick
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
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6
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Rose KAR, Tickle PG, Elsey RM, Sellers WI, Crossley DA, Codd JR. Scaling of axial muscle architecture in juvenile Alligator mississippiensis reveals an enhanced performance capacity of accessory breathing mechanisms. J Anat 2021; 239:1273-1286. [PMID: 34302302 PMCID: PMC8602021 DOI: 10.1111/joa.13523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 07/08/2021] [Accepted: 07/12/2021] [Indexed: 11/30/2022] Open
Abstract
Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional specialisation of the crocodilian trunk is yet to be investigated. Increases in body size and trunk stiffness would be expected to cause a disproportionate increase in muscle force demands and therefore constrain the basal costal aspiration mechanism, necessitating changes in respiratory mechanics. Here, we describe the anatomy of the trunk muscles, their properties that determine muscle performance (mass, length and physiological cross‐sectional area [PCSA]) and investigate their scaling in juvenile Alligator mississippiensis spanning an order of magnitude in body mass (359 g–5.5 kg). Comparatively, the expiratory muscles (transversus abdominis, rectus abdominis, iliocostalis), which compress the trunk, have greater relative PCSA being specialised for greater force‐generating capacity, while the inspiratory muscles (diaphragmaticus, truncocaudalis ischiotruncus, ischiopubis), which create negative internal pressure, have greater relative fascicle lengths, being adapted for greater working range and contraction velocity. Fascicle lengths of the accessory diaphragmaticus scaled with positive allometry in the alligators examined, enhancing contractile capacity, in line with this muscle's ability to modulate both tidal volume and breathing frequency in response to energetic demand during terrestrial locomotion. The iliocostalis, an accessory expiratory muscle, also demonstrated positive allometry in fascicle lengths and mass. All accessory muscles of the infrapubic abdominal wall demonstrated positive allometry in PCSA, which would enhance their force‐generating capacity. Conversely, the basal tetrapod expiratory pump (transversus abdominis) scaled isometrically, which may indicate a decreased reliance on this muscle with ontogeny. Collectively, these findings would support existing anecdotal evidence that crocodilians shift their breathing mechanics as they increase in size. Furthermore, the functional specialisation of the diaphragmaticus and compliance of the body wall in the lumbar region against which it works may contribute to low‐cost breathing in crocodilians.
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Affiliation(s)
- Kayleigh A R Rose
- Department of Biosciences, College of Science, Swansea University, Wales, UK
| | - Peter G Tickle
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Ruth M Elsey
- Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA, USA
| | - William I Sellers
- Department of Earth and Environmental Sciences, Faculty of Science and Engineering, University of Manchester, Manchester, UK
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, TX, USA
| | - Jonathan R Codd
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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7
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Wiseman ALA, Bishop PJ, Demuth OE, Cuff AR, Michel KB, Hutchinson JR. Musculoskeletal modelling of the Nile crocodile (Crocodylus niloticus) hindlimb: Effects of limb posture on leverage during terrestrial locomotion. J Anat 2021; 239:424-444. [PMID: 33754362 PMCID: PMC8273584 DOI: 10.1111/joa.13431] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 03/02/2021] [Accepted: 03/04/2021] [Indexed: 12/11/2022] Open
Abstract
We developed a three-dimensional, computational biomechanical model of a juvenile Nile crocodile (Crocodylus niloticus) pelvis and hindlimb, composed of 47 pelvic limb muscles, to investigate muscle function. We tested whether crocodiles, which are known to use a variety of limb postures during movement, use limb orientations (joint angles) that optimise the moment arms (leverages) or moment-generating capacities of their muscles during different limb postures ranging from a high walk to a sprawling motion. We also describe the three-dimensional (3D) kinematics of the crocodylian hindlimb during terrestrial locomotion across an instrumented walkway and a treadmill captured via X-ray Reconstruction of Moving Morphology (biplanar fluoroscopy; 'XROMM'). We reconstructed the 3D positions and orientations of each of the hindlimb bones and used dissection data for muscle lines of action to reconstruct a focal, subject-specific 3D musculoskeletal model. Motion data for different styles of walking (a high, crouched, bended and two types of sprawling motion) were fed into the 3D model to identify whether any joints adopted near-optimal poses for leverage across each of the behaviours. We found that (1) the hip adductors and knee extensors had their largest leverages during sprawling postures and (2) more erect postures typically involved greater peak moment arms about the hip (flexion-extension), knee (flexion) and metatarsophalangeal (flexion) joints. The results did not fully support the hypothesis that optimal poses are present during different locomotory behaviours because the peak capacities were not always reached around mid-stance phase. Furthermore, we obtained few clear trends for isometric moment-generating capacities. Therefore, perhaps peak muscular leverage in Nile crocodiles is instead reached either in early/late stance or possibly during swing phase or other locomotory behaviours that were not studied here, such as non-terrestrial movement. Alternatively, our findings could reflect a trade-off between having to execute different postures, meaning that hindlimb muscle leverage is not optimised for any singular posture or behaviour. Our model, however, provides a comprehensive set of 3D estimates of muscle actions in extant crocodiles which can form a basis for investigating muscle function in extinct archosaurs.
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Affiliation(s)
- Ashleigh L A Wiseman
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
| | - Peter J Bishop
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK.,Geosciences Program, Queensland Museum, Brisbane, Qld, Australia.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, USA
| | - Oliver E Demuth
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK.,Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Andrew R Cuff
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK.,Hull York Medical School, University of York, York, UK
| | - Krijn B Michel
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
| | - John R Hutchinson
- Structure and Motion Laboratory, Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
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8
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Green TL, Gignac PM. Osteological description of casque ontogeny in the southern cassowary (Casuarius casuarius) using micro-CT imaging. Anat Rec (Hoboken) 2020; 304:461-479. [PMID: 32558300 DOI: 10.1002/ar.24477] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/23/2020] [Accepted: 05/02/2020] [Indexed: 11/06/2022]
Abstract
Extant cassowaries (Casuarius) are unique flightless birds found in the tropics of Indo-Australia. They have garnered substantial attention from anatomists with focus centered on the bony makeup and function of their conspicuous cranial casques, located dorsally above the orbits and neurocranium. The osteological patterning of the casque has been formally described previously; however, there are differing interpretations between authors. These variable descriptions suggest that an anatomical understanding of casque anatomy and its constituent elements may be enhanced by developmental studies aimed at further elucidating this bizarre structure. In the present study, we clarify casque osteology of the southern cassowary (C. casuarius) by detailing casque anatomy across an extensive growth series for the first time. We used micro-computed tomography (μCT) imaging to visualize embryonic development and post-hatching ontogeny through adulthood. We also sampled closely related emus (Dromaius novaehollandiae) and ostriches (Struthio camelus) to provide valuable comparative context. We found that southern cassowary casques are comprised of three paired (i.e., nasals, lacrimals, frontals) and two unpaired elements (i.e., mesethmoid, median casque element). Although lacrimals have rarely been considered as casque elements, the contribution to the casque structure was evident in μCT images. The median casque element has often been cited as a portion of the mesethmoid. However, through comparisons between immature C. casuarius and D. novaehollandiae, we document the median casque element as a distinct unit from the mesethmoid.
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Affiliation(s)
- Todd L Green
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, Oklahoma, USA
| | - Paul M Gignac
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, Oklahoma, USA.,Division of Paleontology, American Museum of Natural History, New York, New York, USA.,MicroCT Imaging Consortium for Research and Outreach, Fayetteville, Arkansas, USA
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9
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Abstract
The evolutionary relationships of the mammalian neocortex and avian dorsal telencephalon (DT) nuclei have been debated for more than a century. Despite their central importance to this debate, nonavian reptiles remain underexplored with modern molecular techniques. Reptile studies harbor great potential for understanding the changes in DT organization that occurred in the early evolution of amniotes. They may also help clarify the specializations in the avian DT, which comprises a massive, cell-dense dorsal ventricular ridge (DVR) and a nuclear dorsal-most structure, the Wulst. Crocodilians are phylogenetically and anatomically attractive for DT comparative studies: they are the closest living relatives of birds and have a strikingly bird-like DVR, but they also possess a highly differentiated reptile cerebral cortex. We studied the DT of the American alligator, Alligator mississippiensis, at late embryonic stages with a panel of molecular marker genes. Gene expression and cytoarchitectonic analyses identified clear homologs of all major avian DVR subdivisions including a mesopallium, an extensive nidopallium with primary sensory input territories, and an arcopallium. The alligator medial cortex is divided into three components that resemble the mammalian dentate gyrus, CA fields, and subiculum in gene expression and topography. The alligator dorsal cortex contains putative homologs of neocortical input, output, and intratelencephalic projection neurons and, most notably, these are organized into sublayers similar to mammalian neocortical layers. Our findings on the molecular anatomy of the crocodilian DT are summarized in an atlas of the alligator telencephalon.
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Affiliation(s)
- Steven D Briscoe
- Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, Illinois
| | - Clifton W Ragsdale
- Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, Illinois.,Department of Neurobiology, University of Chicago, Chicago, Illinois.,Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois
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10
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Barta DE, Nesbitt SJ, Norell MA. The evolution of the manus of early theropod dinosaurs is characterized by high inter- and intraspecific variation. J Anat 2017; 232:80-104. [PMID: 29114853 PMCID: PMC5735062 DOI: 10.1111/joa.12719] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2017] [Indexed: 11/27/2022] Open
Abstract
The origin of the avian hand, with its reduced and fused carpals and digits, from the five‐fingered hands and complex wrists of early dinosaurs represents one of the major transformations of manus morphology among tetrapods. Much attention has been directed to the later part of this transition, from four‐ to three‐fingered taxa. However, earlier anatomical changes may have influenced these later modifications, possibly paving the way for a later frameshift in digit identities. We investigate the five‐ to four‐fingered transition among early dinosaurs, along with changes in carpus morphology. New three‐dimensional reconstructions from computed tomography data of the manus of the Triassic and Early Jurassic theropod dinosaurs Coelophysis bauri and Megapnosaurus rhodesiensis are described and compared intra‐ and interspecifically. Several novel findings emerge from these reconstructions and comparisons, including the first evidence of an ossified centrale and a free intermedium in some C. bauri specimens, as well as confirmation of the presence of a vestigial fifth metacarpal in this taxon. Additionally, a specimen of C. bauri and an unnamed coelophysoid from the Upper Triassic Hayden Quarry, New Mexico, are to our knowledge the only theropods (other than alvarezsaurs and birds) in which all of the distal carpals are completely fused together into a single unit. Several differences between the manus of C. bauri and M. rhodesiensis are also identified. We review the evolution of the archosauromorph manus more broadly in light of these new data, and caution against incorporating carpal characters in phylogenetic analyses of fine‐scale relationships of Archosauromorpha, in light of the high degree of observed polymorphism in taxa for which large sample sizes are available, such as the theropod Coelophysis and the sauropodomorph Plateosaurus. We also find that the reduction of the carpus and ultimate loss of the fourth and fifth digits among early dinosaurs did not proceed in a neat, stepwise fashion, but was characterized by multiple losses and possible gains of carpals, metacarpals and phalanges. Taken together, the high degree of intra‐ and interspecific variability in the number and identities of carpals, and the state of reduction of the fourth and fifth digits suggest the presence of a ‘zone of developmental variability’ in early dinosaur manus evolution, from which novel avian‐like morphologies eventually emerged and became channelized among later theropod clades.
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Affiliation(s)
- Daniel E Barta
- Richard Gilder Graduate School, American Museum of Natural History, New York, NY, USA.,Division of Paleontology, American Museum of Natural History, New York, NY, USA
| | - Sterling J Nesbitt
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.,Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Mark A Norell
- Richard Gilder Graduate School, American Museum of Natural History, New York, NY, USA.,Division of Paleontology, American Museum of Natural History, New York, NY, USA
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11
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Sobral G, Sookias RB, Bhullar BAS, Smith R, Butler RJ, Müller J. New information on the braincase and inner ear of Euparkeria capensis Broom: implications for diapsid and archosaur evolution. R Soc Open Sci 2016; 3:160072. [PMID: 27493766 PMCID: PMC4968458 DOI: 10.1098/rsos.160072] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/10/2016] [Indexed: 05/27/2023]
Abstract
Since its discovery, Euparkeria capensis has been a key taxon for understanding the early evolution of archosaurs. The braincase of Euparkeria was described based on a single specimen, but much uncertainty remained. For the first time, all available braincase material of Euparkeria is re-examined using micro-computed tomography scanning. Contrary to previous work, the parabasisphenoid does not form the posterior border of the fenestra ovalis in lateral view, but it does bear a dorsal projection that forms the anteroventral half of the fenestra. No bone pneumatization was found, but the lateral depression of the parabasisphenoid may have been pneumatic. We propose that the lateral depression likely corresponds to the anterior tympanic recess present in crown archosaurs. The presence of a laterosphenoid is confirmed for Euparkeria. It largely conforms to the crocodilian condition, but shows some features which make it more similar to the avemetatarsalian laterosphenoid. The cochlea of Euparkeria is elongated, forming a deep cochlear recess. In comparison with other basal archosauromorphs, the metotic foramen is much enlarged and regionalized into vagus and recessus scalae tympani areas, indicating an increase in its pressure-relief mechanism. The anterior semicircular canal is extended and corresponds to an enlarged floccular fossa. These aspects of the braincase morphology may be related to the development of a more upright posture and active lifestyle. They also indicate further adaptations of the hearing system of Euparkeria to terrestriality.
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Affiliation(s)
- Gabriela Sobral
- Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
- Departamento de Geologia e Paleontologia, Museu Nacional do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
| | - Roland B. Sookias
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
- GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany
| | - Bhart-Anjan S. Bhullar
- Department of Geology and Geophysics and Peabody Museum of Natural History, Yale University, New Haven, CT, USA
| | - Roger Smith
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- Iziko South African Museum, Cape Town, South Africa
| | - Richard J. Butler
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
| | - Johannes Müller
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
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12
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Janes DE, Organ CL, Stiglec R, O'Meally D, Sarre SD, Georges A, Graves JAM, Valenzuela N, Literman RA, Rutherford K, Gemmell N, Iverson JB, Tamplin JW, Edwards SV, Ezaz T. Molecular evolution of Dmrt1 accompanies change of sex-determining mechanisms in reptilia. Biol Lett 2015; 10:20140809. [PMID: 25540158 DOI: 10.1098/rsbl.2014.0809] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In reptiles, sex-determining mechanisms have evolved repeatedly and reversibly between genotypic and temperature-dependent sex determination. The gene Dmrt1 directs male determination in chicken (and presumably other birds), and regulates sex differentiation in animals as distantly related as fruit flies, nematodes and humans. Here, we show a consistent molecular difference in Dmrt1 between reptiles with genotypic and temperature-dependent sex determination. Among 34 non-avian reptiles, a convergently evolved pair of amino acids encoded by sequence within exon 2 near the DM-binding domain of Dmrt1 distinguishes species with either type of sex determination. We suggest that this amino acid shift accompanied the evolution of genotypic sex determination from an ancestral condition of temperature-dependent sex determination at least three times among reptiles, as evident in turtles, birds and squamates. This novel hypothesis describes the evolution of sex-determining mechanisms as turnover events accompanied by one or two small mutations.
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Affiliation(s)
- Daniel E Janes
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Christopher L Organ
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717, USA
| | - Rami Stiglec
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Denis O'Meally
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Stephen D Sarre
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Jennifer A M Graves
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Robert A Literman
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Kim Rutherford
- Allen Wilson Centre, Department of Anatomy, University of Otago, Dunedin 9054, New Zealand
| | - Neil Gemmell
- Allen Wilson Centre, Department of Anatomy, University of Otago, Dunedin 9054, New Zealand
| | - John B Iverson
- Department of Biology, Earlham College, Richmond, IN 47374, USA
| | - Jeffrey W Tamplin
- Department of Biology, University of Northern Iowa, Cedar Falls, IA 50614, USA
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
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13
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Anné J, Edwards NP, Wogelius RA, Tumarkin-Deratzian AR, Sellers WI, van Veelen A, Bergmann U, Sokaras D, Alonso-Mori R, Ignatyev K, Egerton VM, Manning PL. Synchrotron imaging reveals bone healing and remodelling strategies in extinct and extant vertebrates. J R Soc Interface 2014; 11:20140277. [PMID: 24806709 PMCID: PMC4032541 DOI: 10.1098/rsif.2014.0277] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Current understanding of bone healing and remodelling strategies in vertebrates has traditionally relied on morphological observations through the histological analysis of thin sections. However, chemical analysis may also be used in such interpretations, as different elements are known to be absorbed and used by bone for different physiological purposes such as growth and healing. These chemical signatures are beyond the detection limit of most laboratory-based analytical techniques (e.g. scanning electron microscopy). However, synchrotron rapid scanning–X-ray fluorescence (SRS–XRF) is an elemental mapping technique that uniquely combines high sensitivity (ppm), excellent sample resolution (20–100 µm) and the ability to scan large specimens (decimetre scale) approximately 3000 times faster than other mapping techniques. Here, we use SRS–XRF combined with microfocus elemental mapping (2–20 µm) to determine the distribution and concentration of trace elements within pathological and normal bone of both extant and extinct archosaurs (Cathartes aura and Allosaurus fragilis). Results reveal discrete chemical inventories within different bone tissue types and preservation modes. Chemical inventories also revealed detail of histological features not observable in thin section, including fine structures within the interface between pathological and normal bone as well as woven texture within pathological tissue.
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Affiliation(s)
- Jennifer Anné
- School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, , Manchester M13 9PL, UK
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