1
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Marek RD, Felice RN. The neck as a keystone structure in avian macroevolution and mosaicism. BMC Biol 2023; 21:216. [PMID: 37833771 PMCID: PMC10576348 DOI: 10.1186/s12915-023-01715-x] [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: 05/18/2023] [Accepted: 09/27/2023] [Indexed: 10/15/2023] Open
Abstract
BACKGROUND The origin of birds from non-avian theropod dinosaur ancestors required a comprehensive restructuring of the body plan to enable the evolution of powered flight. One of the proposed key mechanisms that allowed birds to acquire flight and modify the associated anatomical structures into diverse forms is mosaic evolution, which describes the parcelization of phenotypic traits into separate modules that evolve with heterogeneous tempo and mode. Avian mosaicism has been investigated with a focus on the cranial and appendicular skeleton, and as such, we do not understand the role of the axial column in avian macroevolution. The long, flexible neck of extant birds lies between the cranial and pectoral modules and represents an opportunity to study the contribution of the axial skeleton to avian mosaicism. RESULTS Here, we use 3D geometric morphometrics in tandem with phylogenetic comparative methods to provide, to our knowledge, the first integrative analysis of avian neck evolution in context with the head and wing and to interrogate how the interactions between these anatomical systems have influenced macroevolutionary trends across a broad sample of extant birds. We find that the neck is integrated with both the head and the forelimb. These patterns of integration are variable across clades, and only specific ecological groups exhibit either head-neck or neck-forelimb integration. Finally, we find that ecological groups that display head-neck and neck-forelimb integration tend to display significant shifts in the rate of neck morphological evolution. CONCLUSIONS Combined, these results suggest that the interaction between trophic ecology and head-neck-forelimb mosaicism influences the evolutionary variance of the avian neck. By linking together the biomechanical functions of these distinct anatomical systems, the cervical vertebral column serves as a keystone structure in avian mosaicism and macroevolution.
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Affiliation(s)
- Ryan D Marek
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London, UK.
| | - Ryan N Felice
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London, UK
- Department of Life Sciences, Natural History Museum, London, UK
- Department of Genetics, Evolution, and Environment, University College London, London, UK
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2
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Brinkworth A, Green E, Li Y, Oyston J, Ruta M, Wills MA. Bird clades with less complex appendicular skeletons tend to have higher species richness. Nat Commun 2023; 14:5817. [PMID: 37726273 PMCID: PMC10509246 DOI: 10.1038/s41467-023-41415-2] [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: 09/30/2022] [Accepted: 08/30/2023] [Indexed: 09/21/2023] Open
Abstract
Species richness is strikingly uneven across taxonomic groups at all hierarchical levels, but the reasons for this heterogeneity are poorly understood. It is well established that morphological diversity (disparity) is decoupled from taxonomic diversity, both between clades and across geological time. Morphological complexity has been much less studied, but there is theory linking complexity with differential diversity across groups. Here we devise an index of complexity from the differentiation of the fore and hind limb pairs for a sample of 983 species of extant birds. We test the null hypothesis that this index of morphological complexity is uncorrelated with clade diversity, revealing a significant and negative correlation between the species richness of clades and the mean morphological complexity of those clades. Further, we find that more complex clades tend to occupy a smaller number of dietary and habitat niches, and that this proxy for greater ecological specialisation correlates with lower species richness. Greater morphological complexity in the appendicular skeleton therefore appears to hinder the generation and maintenance of species diversity. This may result from entrenchment into morphologies and ecologies that are less capable of yielding further diversity.
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Affiliation(s)
- Andrew Brinkworth
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, BA2 7AZ, UK.
| | - Emily Green
- Joseph Banks Laboratories, Department of Life Sciences, University of Lincoln, Green Lane, Lincoln, LN6 7DL, UK
| | - Yimeng Li
- Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Jack Oyston
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, BA2 7AZ, UK
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - Marcello Ruta
- Joseph Banks Laboratories, Department of Life Sciences, University of Lincoln, Green Lane, Lincoln, LN6 7DL, UK
| | - Matthew A Wills
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, BA2 7AZ, UK
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3
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Liu QL, Cheng L, Stubbs TL, Moon BC, Benton MJ, Yan CB, Tian L. Rapid neck elongation in Sauropterygia (Reptilia: Diapsida) revealed by a new basal pachypleurosaur from the Lower Triassic of China. BMC Ecol Evol 2023; 23:44. [PMID: 37648992 PMCID: PMC10469986 DOI: 10.1186/s12862-023-02150-w] [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: 12/05/2022] [Accepted: 08/16/2023] [Indexed: 09/01/2023] Open
Abstract
Neck elongation has appeared independently in several tetrapod groups, including giraffes and sauropod dinosaurs on land, birds and pterosaurs in the air, and sauropterygians (plesiosaurs and relatives) in the oceans. Long necks arose in Early Triassic sauropterygians, but the nature and rate of that elongation has not been documented. Here, we report a new species of pachypleurosaurid sauropterygian, Chusaurus xiangensis gen. et sp. nov., based on two new specimens from the Early Triassic Nanzhang-Yuan'an Fauna in the South China Block. The new species shows key features of its Middle Triassic relatives, but has a relatively short neck, measuring 0.48 of the trunk length, compared to > 0.8 from the Middle Triassic onwards. Comparative phylogenetic analysis shows that neck elongation occurred rapidly in all Triassic eosauropterygian lineages, probably driven by feeding pressure in a time of rapid re-establishment of new kinds of marine ecosystems.
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Affiliation(s)
- Qi-Ling Liu
- Hubei Key Laboratory of Paleontology and Geological Environment Evolution, Wuhan Centre of China Geological Survey, Wuhan, 430023, P. R. China
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei, 430078, P. R. China
| | - Long Cheng
- Hubei Key Laboratory of Paleontology and Geological Environment Evolution, Wuhan Centre of China Geological Survey, Wuhan, 430023, P. R. China.
| | - Thomas L Stubbs
- School of Earth Sciences, Life Sciences Building, Tyndall Avenue, University of Bristol, Bristol, BS8 1TQ, UK
- School of Life, Health and Chemical Sciences, The Open University, Milton Keynes, UK
| | - Benjamin C Moon
- School of Earth Sciences, Life Sciences Building, Tyndall Avenue, University of Bristol, Bristol, BS8 1TQ, UK
| | - Michael J Benton
- School of Earth Sciences, Life Sciences Building, Tyndall Avenue, University of Bristol, Bristol, BS8 1TQ, UK
| | - Chun-Bo Yan
- Hubei Key Laboratory of Paleontology and Geological Environment Evolution, Wuhan Centre of China Geological Survey, Wuhan, 430023, P. R. China
| | - Li Tian
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei, 430078, P. R. China.
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4
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Li Y, Brinkworth A, Green E, Oyston J, Wills M, Ruta M. Divergent vertebral formulae shape the evolution of axial complexity in mammals. Nat Ecol Evol 2023; 7:367-381. [PMID: 36878987 PMCID: PMC9998275 DOI: 10.1038/s41559-023-01982-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 01/03/2023] [Indexed: 03/08/2023]
Abstract
Complexity, defined as the number of parts and their degree of differentiation, is a poorly explored aspect of macroevolutionary dynamics. The maximum anatomical complexity of organisms has undoubtedly increased through evolutionary time. However, it is unclear whether this increase is a purely diffusive process or whether it is at least partly driven, occurring in parallel in most or many lineages and with increases in the minima as well as the means. Highly differentiated and serially repeated structures, such as vertebrae, are useful systems with which to investigate these patterns. We focus on the serial differentiation of the vertebral column in 1,136 extant mammal species, using two indices that quantify complexity as the numerical richness and proportional distribution of vertebrae across presacral regions and a third expressing the ratio between thoracic and lumbar vertebrae. We address three questions. First, we ask whether the distribution of complexity values in major mammal groups is similar or whether clades have specific signatures associated with their ecology. Second, we ask whether changes in complexity throughout the phylogeny are biased towards increases and whether there is evidence of driven trends. Third, we ask whether evolutionary shifts in complexity depart from a uniform Brownian motion model. Vertebral counts, but not complexity indices, differ significantly between major groups and exhibit greater within-group variation than recognized hitherto. We find strong evidence of a trend towards increasing complexity, where higher values propagate further increases in descendant lineages. Several increases are inferred to have coincided with major ecological or environmental shifts. We find support for multiple-rate models of evolution for all complexity metrics, suggesting that increases in complexity occurred in stepwise shifts, with evidence for widespread episodes of recent rapid divergence. Different subclades evolve more complex vertebral columns in different configurations and probably under different selective pressures and constraints, with widespread convergence on the same formulae. Further work should therefore focus on the ecological relevance of differences in complexity and a more detailed understanding of historical patterns.
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Affiliation(s)
- Yimeng Li
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK.,Nanjing Institute of Geology and Palaeontology, CAS, Nanjing, China
| | - Andrew Brinkworth
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - Emily Green
- Joseph Banks Laboratories, Department of Life Sciences, University of Lincoln, Lincoln, UK
| | - Jack Oyston
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - Matthew Wills
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK.
| | - Marcello Ruta
- Joseph Banks Laboratories, Department of Life Sciences, University of Lincoln, Lincoln, UK.
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5
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Large size in aquatic tetrapods compensates for high drag caused by extreme body proportions. Commun Biol 2022; 5:380. [PMID: 35484197 PMCID: PMC9051157 DOI: 10.1038/s42003-022-03322-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 03/25/2022] [Indexed: 11/08/2022] Open
Abstract
Various Mesozoic marine reptile lineages evolved streamlined bodies and efficient lift-based swimming, as seen in modern aquatic mammals. Ichthyosaurs had low-drag bodies, akin to modern dolphins, but plesiosaurs were strikingly different, with long hydrofoil-like limbs and greatly variable neck and trunk proportions. Using computational fluid dynamics, we explore the effect of this extreme morphological variation. We find that, independently of their body fineness ratio, plesiosaurs produced more drag than ichthyosaurs and modern cetaceans of equal mass due to their large limbs, but these differences were not significant when body size was accounted for. Additionally, necks longer than twice the trunk length can substantially increase the cost of forward swimming, but this effect was cancelled out by the evolution of big trunks. Moreover, fast rates in the evolution of neck proportions in the long-necked elasmosaurs suggest that large trunks might have released the hydrodynamic constraints on necks thus allowing their extreme enlargement.
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6
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Figueirido B, Serrano FJ, Pérez-Ramos A, Esteban JM, Ferrón HG, Martín-Serra A. Body-axis organization in tetrapods: a model-system to disentangle the developmental origins of convergent evolution in deep time. Biol Lett 2022; 18:20220047. [PMID: 35382583 PMCID: PMC8984341 DOI: 10.1098/rsbl.2022.0047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Convergent evolution is a central concept in evolutionary theory but the underlying mechanism has been largely debated since On the Origin of Species. Previous hypotheses predict that developmental constraints make some morphologies more likely to arise than others and natural selection discards those of the lowest fitness. However, the quantification of the role and strength of natural selection and developmental constraint in shaping convergent phenotypes on macroevolutionary timescales is challenging because the information regarding performance and development is not directly available. Accordingly, current knowledge of how embryonic development and natural selection drive phenotypic evolution in vertebrates has been extended from studies performed at short temporal scales. We propose here the organization of the tetrapod body-axis as a model system to investigate the developmental origins of convergent evolution over hundreds of millions of years. The quantification of the primary developmental mechanisms driving body-axis organization (i.e. somitogenesis, homeotic effects and differential growth) can be inferred from vertebral counts, and recent techniques of three-dimensional computational biomechanics have the necessary potential to reveal organismal performance even in fossil forms. The combination of both approaches offers a novel and robust methodological framework to test competing hypotheses on the functional and developmental drivers of phenotypic evolution and evolutionary convergence.
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Affiliation(s)
- Borja Figueirido
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain
| | - Francisco J Serrano
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain.,Dinosaur Institute, Natural History Museum of Los Angeles County; Exposition Boulevard, Los Angeles, CA 90007, USA
| | - Alejandro Pérez-Ramos
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain
| | - Juan Miguel Esteban
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain
| | - Humberto G Ferrón
- Instituto Cavanilles de Biodiversidad y Biologia Evolutiva, Universitat de Valencia, 46980-Paterna, Valencia, Spain
| | - Alberto Martín-Serra
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain
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7
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Figueirido B, Martín-Serra A, Pérez-Ramos A, Velasco D, Pastor FJ, Benson RJ. Serial disparity in the carnivoran backbone unveils a complex adaptive role in metameric evolution. Commun Biol 2021; 4:863. [PMID: 34267313 PMCID: PMC8282787 DOI: 10.1038/s42003-021-02346-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 05/20/2021] [Indexed: 11/09/2022] Open
Abstract
Organisms comprise multiple interacting parts, but few quantitative studies have analysed multi-element systems, limiting understanding of phenotypic evolution. We investigate how disparity of vertebral morphology varies along the axial column of mammalian carnivores — a chain of 27 subunits — and the extent to which morphological variation have been structured by evolutionary constraints and locomotory adaptation. We find that lumbars and posterior thoracics exhibit high individual disparity but low serial differentiation. They are pervasively recruited into locomotory functions and exhibit relaxed evolutionary constraint. More anterior vertebrae also show signals of locomotory adaptation, but nevertheless have low individual disparity and constrained patterns of evolution, characterised by low-dimensional shape changes. Our findings demonstrate the importance of the thoracolumbar region as an innovation enabling evolutionary versatility of mammalian locomotion. Moreover, they underscore the complexity of phenotypic macroevolution of multi-element systems and that the strength of ecomorphological signal does not have a predictable influence on macroevolutionary outcomes. Figueirido et al. use a 3D geometric morphometric approach to study functional among-species disparity in the vertebral column of Carnivora, as well as assessing the effect of different sampling methods on homology. Disparity is generally higher in more caudal regions, compared to more cranial regions, but recruitment for locomotor function is pervasive throughout the whole studied column.
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Affiliation(s)
- Borja Figueirido
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
| | - Alberto Martín-Serra
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Alejandro Pérez-Ramos
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - David Velasco
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Francisco J Pastor
- Departamento de Anatomía y Radiología, Museo de Anatomía, Universidad de Valladolid, Valladolid, Spain
| | - Roger J Benson
- Department of Earth Sciences, University of Oxford, Oxford, UK
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8
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Fischer V, Zverkov NG, Arkhangelsky MS, Stenshin IM, Blagovetshensky IV, Uspensky GN. A new elasmosaurid plesiosaurian from the Early Cretaceous of Russia marks an early attempt at neck elongation. Zool J Linn Soc 2020. [DOI: 10.1093/zoolinnean/zlaa103] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
Plesiosaurian marine reptiles evolved a wide range of body shapes during the Jurassic and Cretaceous, including long-necked forms. Many Late Cretaceous members of the clade Elasmosauridae epitomized this part of the plesiosaurian morphological spectrum by evolving extremely long necks through somitogenesis (resulting in an increase in the number of cervical centra) and differential growth (resulting in the elongation of cervical centra). However, the early evolution of elasmosaurids remains poorly understood because of a generally poor Lower Cretaceous fossil record. We describe a new elasmosaurid, Jucha squalea gen. et sp. nov., from the upper Hauterivian (Lower Cretaceous) of Ulyanovsk (European Russia), in addition to other elasmosaurid remains from the same area. Jucha squalea is one of the oldest and basalmost elasmosaurids known and lacks a series of features that otherwise characterize the group, such as the heart-shaped intercoracoid fenestra and the median pectoral bar. However, Jucha squalea marks an early attempt at cervical elongation through differential growth. The data we gathered on the shape of cervical centra among elasmosaurids suggest multiple episodes of elongation and shortening. However, the precise patterns are obscured by an unstable phylogenetic signal.
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Affiliation(s)
- Valentin Fischer
- Evolution & Diversity Dynamics Lab, Université de Liège, Allée du 6 Août, Liège, Belgium
| | - Nikolay G Zverkov
- Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow, Russia
- Geological Institute of the Russian Academy of Sciences, Moscow, Russia
| | - Maxim S Arkhangelsky
- Department of General Geology and Minerals, Saratov State University, Saratov, Russia
- Department of Geoecology and Engineering Geology, Saratov State Technical University, Saratov, Russia
| | - Ilya M Stenshin
- Undory Paleontological Museum, Undory, Ulyanovsk Region, Russia
| | - Ivan V Blagovetshensky
- Department of Biology, Ecology and Nature Management, Ulyanovsk State University, Ulyanovsk, Russia
| | - Gleb N Uspensky
- Natural Science Museum, Ulyanovsk State University, Ulyanovsk, Russia
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9
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Fischer V, MacLaren JA, Soul LC, Bennion RF, Druckenmiller PS, Benson RBJ. The macroevolutionary landscape of short-necked plesiosaurians. Sci Rep 2020; 10:16434. [PMID: 33009498 PMCID: PMC7532190 DOI: 10.1038/s41598-020-73413-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/16/2020] [Indexed: 11/09/2022] Open
Abstract
Throughout their evolution, tetrapods have repeatedly colonised a series of ecological niches in marine ecosystems, producing textbook examples of convergent evolution. However, this evolutionary phenomenon has typically been assessed qualitatively and in broad-brush frameworks that imply simplistic macroevolutionary landscapes. We establish a protocol to visualize the density of trait space occupancy and thoroughly test for the existence of macroevolutionary landscapes. We apply this protocol to a new phenotypic dataset describing the morphology of short-necked plesiosaurians, a major component of the Mesozoic marine food webs (ca. 201 to 66 Mya). Plesiosaurians evolved this body plan multiple times during their 135-million-year history, making them an ideal test case for the existence of macroevolutionary landscapes. We find ample evidence for a bimodal craniodental macroevolutionary landscape separating latirostrines from longirostrine taxa, providing the first phylogenetically-explicit quantitative assessment of trophic diversity in extinct marine reptiles. This bimodal pattern was established as early as the Middle Jurassic and was maintained in evolutionary patterns of short-necked plesiosaurians until a Late Cretaceous (Turonian) collapse to a unimodal landscape comprising longirostrine forms with novel morphologies. This study highlights the potential of severe environmental perturbations to profoundly alter the macroevolutionary dynamics of animals occupying the top of food chains.
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Affiliation(s)
- Valentin Fischer
- Evolution & Diversity Dynamics Lab, Université de Liège, 14 Allée du 6 Août, 4000, Liège, Belgium.
| | - Jamie A MacLaren
- Evolution & Diversity Dynamics Lab, Université de Liège, 14 Allée du 6 Août, 4000, Liège, Belgium
| | - Laura C Soul
- Department of Paleobiology, Smithsonian Institution, P.O. Box 37012, Washington, DC, 20013-7012, USA
| | - Rebecca F Bennion
- Evolution & Diversity Dynamics Lab, Université de Liège, 14 Allée du 6 Août, 4000, Liège, Belgium
- OD Earth and History of Life, Institut Royal des Sciences Naturelles de Belgique, 29 Rue Vautier, 1000, Brussels, Belgium
| | - Patrick S Druckenmiller
- University of Alaska Museum and Department of Geosciences, University of Alaska Fairbanks, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, South Parks road, Oxford, OX1 3AN, UK
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10
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Evolution of the Mammalian Neck from Developmental, Morpho-Functional, and Paleontological Perspectives. J MAMM EVOL 2020. [DOI: 10.1007/s10914-020-09506-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
AbstractThe mammalian neck adopts a variety of postures during daily life and generates numerous head trajectories. Despite its functional diversity, the neck is constrained to seven cervical vertebrae in (almost) all mammals. Given this low number, an unexpectedly high degree of modularity of the mammalian neck has more recently been uncovered. This work aims to review neck modularity in mammals from a developmental, morpho-functional, and paleontological perspective and how high functional diversity evolved in the mammalian neck after the occurrence of meristic limitations. The fixed number of cervical vertebrae and the developmental modularity of the mammalian neck are closely linked to anterior Hox genes expression and strong developmental integration between the neck and other body regions. In addition, basic neck biomechanics promote morpho-functional modularity due to preferred motion axes in the cranio-cervical and cervico-thoracic junction. These developmental and biomechanical determinants result in the characteristic and highly conserved shape variation among the vertebrae that delimits morphological modules. The step-wise acquisition of these unique cervical traits can be traced in the fossil record. The increasing functional specialization of neck modules, however, did not evolve all at once but started much earlier in the upper than in the lower neck. Overall, the strongly conserved modularity in the mammalian neck represents an evolutionary trade-off between the meristic constraints and functional diversity. Although a morpho-functional partition of the neck is common among amniotes, the degree of modularity and the way neck disparity is realized is unique in mammals.
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11
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Wintrich T, Jonas R, Wilke HJ, Schmitz L, Sander PM. Neck mobility in the Jurassic plesiosaur Cryptoclidus eurymerus: finite element analysis as a new approach to understanding the cervical skeleton in fossil vertebrates. PeerJ 2019; 7:e7658. [PMID: 31720095 PMCID: PMC6842296 DOI: 10.7717/peerj.7658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 08/11/2019] [Indexed: 11/20/2022] Open
Abstract
The sauropterygian clade Plesiosauria arose in the Late Triassic and survived to the very end of the Cretaceous. Plesiosauria evolved the greatest species diversity of any marine reptile clade, attaining a global distribution. Plesiosauria consist of two clades, Rhomaleosauridae and Neoplesiosauria. Basal Neoplesiosauria have long necks with at least 30 cervicals, but show qualitative osteological evidence for a stiff neck. Here we quantify neck mobility in lateral, ventral, and dorsal directions based on finite element modeling of neck vertebrae from the Middle Jurassic plesiosaur Cryptoclidus eurymerus. We model the mobility in a single motion segment, consisting of two adjacent cervical vertebrae and the joints connecting them. Based on the model with a maximum intervertebral spacing of 3 mm, we find that in Cryptoclidus, the maximum angle of lateral deflection in the motion segment was 2°. The maximum angle of ventral deflection was 5° and of dorsal deflection was 5°. When these values are multiplied by the number of cervical vertebrae, it becomes apparent that neck mobility was limited in all directions. The maximum angle of total lateral deflection in the neck was 67°. The maximum angle of total ventral deflection was 148° and of total dorsal deflection was 157°. This raises the question of the function of such a long, multi-segment but immobile neck. We posit that the long neck served in hydrodynamic and visual camouflage, hiding the bulk of the body from the small but abundant prey, such as schooling fish and squid. Neck immobility may have been advantageous in withstanding strong hydrodynamic forces acting on the neck during predatory strikes.
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Affiliation(s)
- Tanja Wintrich
- Section Paleontology, Institute of Geosciences, University of Bonn, Bonn, Germany.,Institute of Anatomy, University of Bonn, Bonn, Germany
| | - René Jonas
- Institute of Orthopaedic Research and Biomechanics, Universität Ulm, Ulm, Germany
| | | | - Lars Schmitz
- Keck Science Department of the Claremont Colleges, Claremont, CA, USA.,Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
| | - P Martin Sander
- Section Paleontology, Institute of Geosciences, University of Bonn, Bonn, Germany.,Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
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12
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Powell GL, Russell AP, Sutey J. Patterns of growth in the presacral vertebral column of the leopard gecko (Eublepharis macularius). J Morphol 2018; 279:1088-1103. [PMID: 29732599 DOI: 10.1002/jmor.20833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/06/2018] [Accepted: 04/08/2018] [Indexed: 11/10/2022]
Abstract
Postnatal growth patterns within the vertebral column may be informative about body proportions and regionalization. We measured femur length, lengths of all pre-sacral vertebrae, and lengths of intervertebral spaces, from radiographs of a series of 21 Eublepharis macularius, raised under standard conditions and covering most of the ontogenetic body size range. Vertebrae were grouped into cervical, sternal, and dorsal compartments, and lengths of adjacent pairs of vertebrae were summed before analysis. Femur length was included as an index of body size. Principal component analysis of the variance-covariance matrix of these data was used to investigate scaling among them. PC1 explained 94.19% of total variance, interpreted as the variance due to body size. PC1 differed significantly from the hypothetical isometric vector, indicating overall allometry. The atlas and axis vertebrae displayed strong negative allometry; the remainder of the vertebral pairs exhibited weak negative allometry, isometry or positive allometry. PC1 explained a markedly smaller amount of variance for the vertebral pairs of the cervical compartment than for the remainder of the vertebral pairs, with the exception of the final pair. The relative standard deviations of the eigenvalues from the PCAs of the three vertebral compartments indicated that the vertebrae of the cervical compartment were less strongly integrated by scaling than were the sternal or dorsal vertebrae, which did not differ greatly between themselves in their strong integration, suggesting that the growth of the cervical vertebrae is constrained by the mechanical requirements of the head. Regionalization of the remainder of the vertebral column is less clearly defined but may be associated with wave form propagation incident upon locomotion, and by locomotory changes occasioned by tail autotomy and regeneration. Femur length exhibits negative allometry relative to individual vertebral pairs and to vertebral column length, suggesting a change in locomotor requirements over the ontogenetic size range.
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Affiliation(s)
| | - Anthony P Russell
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Jennifer Sutey
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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13
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Fischer V, Benson RBJ, Druckenmiller PS, Ketchum HF, Bardet N. The evolutionary history of polycotylid plesiosaurians. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172177. [PMID: 29657811 PMCID: PMC5882735 DOI: 10.1098/rsos.172177] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/13/2018] [Indexed: 05/31/2023]
Abstract
Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. Thililua longicollis from the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long neck and, as originally reported, a series of unusual cranial features that cause unstable phylogenetic relationships for polycotylids. We reinterpret the holotype specimen of Thililua longicollis and clarify its cranial anatomy. Thililua longicollis possesses an extensive, foramina-bearing jugal, a premaxilla-parietal contact and carinated teeth. Phylogenetic analyses of a new cladistic dataset based on first-hand observation of most polycotylids recover Thililua and Mauriciosaurus as successive lineages at the base of the earliest Late Cretaceous polycotyline radiation. A new dataset summarizing the Bauplan of polycotylids reveals that their radiation produced an early burst of disparity during the Cenomanian-Turonian interval, with marked plasticity in relative neck length, but this did not arise as an ecological release following the extinction of ichthyosaurs and pliosaurids. This disparity vanished during and after the Turonian, which is consistent with a model of 'early experimentation/late constraint'. Two polycotylid clades, Occultonectia clade nov. and Polycotylinae, survived up to the Maastrichtian, but with low diversity.
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Affiliation(s)
- V. Fischer
- Department of Geology, Université de Liège, 14 allée du 6 Août, Liège 4000, Belgium
| | - R. B. J. Benson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - P. S. Druckenmiller
- University of Alaska Museum and Department of Geosciences, University of Alaska Fairbanks, 1962 Yukon Drive, Fairbanks, AK 99775, USA
| | - H. F. Ketchum
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - N. Bardet
- CR2P CNRS-MNHN-UPMC Paris 6, Département Origines et Evolution, Muséum National d'Histoire Naturelle, CP 38, 57 rue Cuvier, 75005 Paris, France
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14
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Neenan JM, Reich T, Evers SW, Druckenmiller PS, Voeten DFAE, Choiniere JN, Barrett PM, Pierce SE, Benson RBJ. Evolution of the Sauropterygian Labyrinth with Increasingly Pelagic Lifestyles. Curr Biol 2017; 27:3852-3858.e3. [PMID: 29225027 DOI: 10.1016/j.cub.2017.10.069] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 10/25/2017] [Accepted: 10/27/2017] [Indexed: 11/29/2022]
Abstract
Sauropterygia, a successful clade of marine reptiles abundant in aquatic ecosystems of the Mesozoic, inhabited nearshore to pelagic habitats over >180 million years of evolutionary history [1]. Aquatic vertebrates experience strong buoyancy forces that allow movement in a three-dimensional environment, resulting in structural convergences such as flippers and fish-like bauplans [2, 3], as well as convergences in the sensory systems. We used computed tomographic scans of 19 sauropterygian species to determine how the transition to pelagic lifestyles influenced the evolution of the endosseous labyrinth, which houses the vestibular sensory organ of balance and orientation [4]. Semicircular canal geometries underwent distinct changes during the transition from nearshore Triassic sauropterygians to the later, pelagic plesiosaurs. Triassic sauropterygians have dorsoventrally compact, anteroposteriorly elongate labyrinths, resembling those of crocodylians. In contrast, plesiosaurs have compact, bulbous labyrinths, sharing some features with those of sea turtles. Differences in relative labyrinth size among sauropterygians correspond to locomotory differences: bottom-walking [5, 6] placodonts have proportionally larger labyrinths than actively swimming taxa (i.e., all other sauropterygians). Furthermore, independent evolutionary origins of short-necked, large-headed "pliosauromorph" body proportions among plesiosaurs coincide with reductions of labyrinth size, paralleling the evolutionary history of cetaceans [7]. Sauropterygian labyrinth evolution is therefore correlated closely with both locomotory style and body proportions, and these changes are consistent with isolated observations made previously in other marine tetrapods. Our study presents the first virtual reconstructions of plesiosaur endosseous labyrinths and the first large-scale, quantitative study detailing the effects of increasingly aquatic lifestyles on labyrinth morphology among marine reptiles.
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Affiliation(s)
- James M Neenan
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK.
| | - Tobias Reich
- Palaeontological Institute and Museum, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Serjoscha W Evers
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Patrick S Druckenmiller
- University of Alaska Museum and Department of Geology and Geophysics, University of Alaska Fairbanks, 907 Yukon Drive, Fairbanks, AK 99775, USA
| | - Dennis F A E Voeten
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38000 Grenoble, France; Department of Zoology and Laboratory of Ornithology, Palacký University, 17 listopadu 50, 771 46 Olomouc, Czech Republic
| | - Jonah N Choiniere
- School of Geosciences and Evolutionary Studies Institute, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, Braamfontein 2000, South Africa
| | - Paul M Barrett
- Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK; School of Geosciences and Evolutionary Studies Institute, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, Braamfontein 2000, South Africa
| | - Stephanie E Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK; School of Geosciences and Evolutionary Studies Institute, University of the Witwatersrand, 1 Jan Smuts Avenue, Johannesburg, Braamfontein 2000, South Africa
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