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LePore CN, McLain MA. Variation in the sacrum of phytosaurs: New evidence from a partial skeleton of Machaeroprosopus mccauleyi. J Anat 2024; 244:959-976. [PMID: 38284134 PMCID: PMC11095306 DOI: 10.1111/joa.14007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 01/30/2024] Open
Abstract
Phytosaurs are a group of Upper Triassic semi-aquatic archosauriform reptiles. Their variable skull morphology forms the foundation of our understanding of their relationships and paleoecology, while only a few studies have focused on demonstrating the existence of postcranial variation. The numbers of vertebrae in the sacrum are thought to vary from two, the plesiomorphic condition for archosauriforms, to three, with the addition of a sacralized dorsal (i.e., dorsosacral) vertebra. In this study, we demonstrate the presence of a sacralized first caudal (i.e., caudosacral) vertebra in a sacrum belonging to Machaeroprosopus mccauleyi. We rule out taphonomic distortion or pathology as explanations for the inclusion of this element in the sacrum, suggesting instead that it occurred through modifications of the same developmental processes that likely produced dorsosacral vertebrae in phytosaurs. Additionally, we show that a dorsosacral vertebra is common in phytosaur specimens from the Chinle Formation and Dockum Group of the southwestern United States and suggest that it may be widespread among phytosaurs. The addition of sacral vertebrae potentially aided adaptation to larger body sizes or more terrestrial lifestyles in certain taxa.
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Affiliation(s)
- Caleb N. LePore
- Department of Earth and Biological SciencesLoma Linda UniversityLoma LindaCaliforniaUSA
| | - Matthew A. McLain
- Department of Earth and Biological SciencesLoma Linda UniversityLoma LindaCaliforniaUSA
- Department of Biological and Physical SciencesThe Master's UniversitySanta ClaritaCaliforniaUSA
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Wu S, Rheindt FE, Zhang J, Wang J, Zhang L, Quan C, Li Z, Wang M, Wu F, Qu Y, Edwards SV, Zhou Z, Liu L. Genomes, fossils, and the concurrent rise of modern birds and flowering plants in the Late Cretaceous. Proc Natl Acad Sci U S A 2024; 121:e2319696121. [PMID: 38346181 PMCID: PMC10895254 DOI: 10.1073/pnas.2319696121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 12/29/2023] [Indexed: 02/15/2024] Open
Abstract
The phylogeny and divergence timing of the Neoavian radiation remain controversial despite recent progress. We analyzed the genomes of 124 species across all Neoavian orders, using data from 25,460 loci spanning four DNA classes, including 5,756 coding sequences, 12,449 conserved nonexonic elements, 4,871 introns, and 2,384 intergenic segments. We conducted a comprehensive sensitivity analysis to account for the heterogeneity across different DNA classes, leading to an optimal tree of Neoaves with high resolution. This phylogeny features a novel Neoavian dichotomy comprising two monophyletic clades: a previously recognized Telluraves (land birds) and a newly circumscribed Aquaterraves (waterbirds and relatives). Molecular dating analyses with 20 fossil calibrations indicate that the diversification of modern birds began in the Late Cretaceous and underwent a constant and steady radiation across the KPg boundary, concurrent with the rise of angiosperms as well as other major Cenozoic animal groups including placental and multituberculate mammals. The KPg catastrophe had a limited impact on avian evolution compared to the Paleocene-Eocene Thermal Maximum, which triggered a rapid diversification of seabirds. Our findings suggest that the evolution of modern birds followed a slow process of gradualism rather than a rapid process of punctuated equilibrium, with limited interruption by the KPg catastrophe. This study places bird evolution into a new context within vertebrates, with ramifications for the evolution of the Earth's biota.
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Affiliation(s)
- Shaoyuan Wu
- Jiangsu Key Laboratory of Phylogenomics and Comparative Genomics, Jiangsu International Joint Center of Genomics, School of Life Sciences, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China
| | - Frank E Rheindt
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Jin Zhang
- School of Computer and Communication Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China
| | - Jiajia Wang
- Jiangsu Key Laboratory of Phylogenomics and Comparative Genomics, Jiangsu International Joint Center of Genomics, School of Life Sciences, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China
| | - Lei Zhang
- Jiangsu Key Laboratory of Phylogenomics and Comparative Genomics, Jiangsu International Joint Center of Genomics, School of Life Sciences, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China
| | - Cheng Quan
- School of Earth Science and Resources, Chang'an University, Xi'an, Shaanxi 710054, China
| | - Zhiheng Li
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Min Wang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Feixiang Wu
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Yanhua Qu
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138
| | - Zhonghe Zhou
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Liang Liu
- Department of Statistics, Institute of Bioinformatics, University of Georgia, Athens, GA 30606
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Brownstein CD. A juvenile bird with possible crown-group affinities from a dinosaur-rich Cretaceous ecosystem in North America. BMC Ecol Evol 2024; 24:20. [PMID: 38336630 PMCID: PMC10858573 DOI: 10.1186/s12862-024-02210-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 02/01/2024] [Indexed: 02/12/2024] Open
Abstract
BACKGROUND Living birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins. RESULTS Here, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon. The North American provenance of the specimen supports a cosmopolitan distribution of early crown birds, clashes with the hypothesized southern hemisphere origins of living birds, and demonstrates that crown birds and their closest relatives coexisted with non-avian dinosaurs that independently converged on avian skeletal anatomy, such as the alvarezsaurids and dromaeosaurids. CONCLUSIONS By revealing the ecological and biogeographic context of Cretaceous birds within or near the crown clade, the Lance Formation specimen provides new insights into the contingent nature of crown avian survival through the Cretaceous-Paleogene mass extinction and the subsequent origins of living bird diversity.
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Affiliation(s)
- Chase Doran Brownstein
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.
- , Stamford, USA.
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Widrig KE, Bhullar BS, Field DJ. 3D atlas of tinamou (Neornithes: Tinamidae) pectoral morphology: Implications for reconstructing the ancestral neornithine flight apparatus. J Anat 2023; 243:729-757. [PMID: 37358291 PMCID: PMC10557402 DOI: 10.1111/joa.13919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 06/06/2023] [Accepted: 06/12/2023] [Indexed: 06/27/2023] Open
Abstract
Palaeognathae, the extant avian clade comprising the flightless ratites and flight-capable tinamous (Tinamidae), is the sister group to all other living birds, and recent phylogenetic studies illustrate that tinamous are phylogenetically nested within a paraphyletic assemblage of ratites. As the only extant palaeognaths that have retained the ability to fly, tinamous may provide key information on the nature of the flight apparatus of ancestral crown palaeognaths-and, in turn, crown birds-as well as insight into convergent modifications to the wing apparatus among extant ratite lineages. To reveal new information about the musculoskeletal anatomy of tinamous and facilitate development of computational biomechanical models of tinamou wing function, we generated a three-dimensional musculoskeletal model of the flight apparatus of the extant Andean tinamou (Nothoprocta pentlandii) using diffusible iodine-based contrast-enhanced computed tomography (diceCT). Origins and insertions of the pectoral flight musculature of N. pentlandii are generally consistent with those of other extant volant birds specialized for burst flight, and the entire suite of presumed ancestral neornithine flight muscles are present in N. pentlandii with the exception of the biceps slip. The pectoralis and supracoracoideus muscles are robust, similar to the condition in other extant burst-flying birds such as many extant Galliformes. Contrary to the condition in most extant Neognathae (the sister clade to Palaeognathae), the insertion of the pronator superficialis has a greater distal extent than the pronator profundus, although most other anatomical observations are broadly consistent with the conditions observed in extant neognaths. This work will help form a basis for future comparative studies of the avian musculoskeletal system, with implications for reconstructing the flight apparatus of ancestral crown birds and clarifying musculoskeletal modifications underlying the convergent origins of ratite flightlessness.
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Affiliation(s)
- Klara E. Widrig
- Department of Earth SciencesUniversity of CambridgeCambridgeUK
| | - Bhart‐Anjan S. Bhullar
- Department of Earth and Planetary SciencesYale UniversityNew HavenConnecticutUSA
- Peabody Museum of Natural HistoryYale UniversityNew HavenConnecticutUSA
| | - Daniel J. Field
- Department of Earth SciencesUniversity of CambridgeCambridgeUK
- Museum of ZoologyUniversity of CambridgeCambridgeUK
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Lowi-Merri TM, Demuth OE, Benito J, Field DJ, Benson RBJ, Claramunt S, Evans DC. Reconstructing locomotor ecology of extinct avialans: a case study of Ichthyornis comparing sternum morphology and skeletal proportions. Proc Biol Sci 2023; 290:20222020. [PMID: 36883281 PMCID: PMC9993061 DOI: 10.1098/rspb.2022.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 02/08/2023] [Indexed: 03/09/2023] Open
Abstract
Avian skeletal morphology is associated with locomotor function, including flight style, swimming and terrestrial locomotion, and permits informed inferences on locomotion in extinct taxa. The fossil taxon Ichthyornis (Avialae: Ornithurae) has long been regarded as highly aerial, with flight similar to terns or gulls (Laridae), and skeletal features resembling foot-propelled diving adaptations. However, rigorous testing of locomotor hypotheses has yet to be performed on Ichthyornis, despite its notable phylogenetic position as one of the most crownward stem birds. We analysed separate datasets of three-dimensional sternal shape (geometric morphometrics) and skeletal proportions (linear measurements across the skeleton), to examine how well these data types predict locomotor traits in Neornithes. We then used this information to infer locomotor capabilities of Ichthyornis. We find strong support for both soaring and foot-propelled swimming capabilities in Ichthyornis. Further, sternal shape and skeletal proportions provide complementary information on avian locomotion: skeletal proportions allow better predictions of the capacity for flight, whereas sternal shape predicts variation in more specific locomotor abilities such as soaring, foot-propelled swimming and escape burst flight. These results have important implications for future studies of extinct avialan ecology and underscore the importance of closely considering sternum morphology in investigations of fossil bird locomotion.
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Affiliation(s)
- Talia M. Lowi-Merri
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6
| | - Oliver E. Demuth
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
- Structure and Motion Laboratory, Royal Veterinary College, Hatfield, UK
| | - Juan Benito
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
- Department of Biology and Biochemistry, Milner Centre for Evolution, University of Bath, Bath, UK
| | - Daniel J. Field
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
- Museum of Zoology, University of Cambridge, Cambridge, UK
| | - Roger B. J. Benson
- Division of Paleontology, American Museum of Natural History, 200 Central Park West, New York, NY 12004, USA
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK
| | - Santiago Claramunt
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6
| | - David C. Evans
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6
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Basal Anseriformes from the Early Paleogene of North America and Europe. DIVERSITY 2023. [DOI: 10.3390/d15020233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
We describe nearly complete skeletons of basal Anseriformes from the Latest Paleocene to the early Eocene of North America and Europe. Collectively, these birds appear to be representative of anseriforms near the divergence of Anhimae and Anseres, but their exact positions relative to these clades remains uncertain. A new family, Anachronornithidae nov. fam., is erected on the basis of one of these, Anachronornis anhimops nov. gen., nov. gen. et sp., to which the others cannot be confidently assigned. The new fossils augment a growing collection of early Pan-Anseriformes, which in their diversity do not paint an unambiguous picture of phylogeny or character state evolution on the path to or within crown-Anseriformes. Anachronornis nov. gen. is similar in some aspects of both cranial and postcranial anatomy to other well-represented early Paleogene Anseriformes and members of Anseres, such as Presbyornis Wetmore, 1926. However, it exhibits a more landfowl-like bill, like that of Anhimae and unlike the spatulate bill of Anseres. Additional specimens of similar basal Anseriformes of uncertain affinities from the early Eocene of North America and Europe further complicate interpretation of character state polarity due to the mosaicism of primitive and derived characters they exhibit.
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