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Esteban JM, Martín-Serra A, Pérez-Ramos A, Mulot B, Jones K, Figueirido B. The impact of the land-to-sea transition on evolutionary integration and modularity of the pinniped backbone. Commun Biol 2023; 6:1141. [PMID: 37949962 PMCID: PMC10638317 DOI: 10.1038/s42003-023-05512-8] [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: 05/24/2023] [Accepted: 10/26/2023] [Indexed: 11/12/2023] Open
Abstract
In this study, we investigate how the terrestrial-aquatic transition influenced patterns of axial integration and modularity in response to the secondary adaptation to a marine lifestyle. We use 3D geometric morphometrics to quantify shape covariation among presacral vertebrae in pinnipeds (Carnivora; Pinnipedia) and to compare with patterns of axial integration and modularity in their close terrestrial relatives. Our results indicate that the vertebral column of pinnipeds has experienced a decrease in the strength of integration among all presacral vertebrae when compared to terrestrial carnivores (=fissipeds). However, separate integration analyses among the speciose Otariidae (i.e., sea lions and fur seals) and Phocidae (i.e., true seals) also suggests the presence of different axial organizations in these two groups of crown pinnipeds. While phocids present a set of integrated "thoracic" vertebrae, the presacral vertebrae of otariids are characterized by the absence of any set of vertebrae with high integration. We hypothesize that these differences could be linked to their specific modes of aquatic locomotion -i.e., pelvic vs pectoral oscillation. Our results provide evidence that the vertebral column of pinnipeds has been reorganized from the pattern observed in fissipeds but is more complex than a simple "homogenization" of the modular pattern of their close terrestrial relatives.
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Affiliation(s)
- Juan Miguel Esteban
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain.
| | - Alberto Martín-Serra
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
| | - Alejandro Pérez-Ramos
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
| | - Baptiste Mulot
- ZooParc de Beauval & Beauval Nature, 41110, Saint-Aignan, France
| | - Katrina Jones
- Department of Earth and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL, UK
| | - Borja Figueirido
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071, Málaga, Spain
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Smith SM, Angielczyk KD. A Shrewd Inspection of Vertebral Regionalization in Large Shrews (Soricidae: Crocidurinae). Integr Org Biol 2022; 4:obac006. [PMID: 35291671 PMCID: PMC8915212 DOI: 10.1093/iob/obac006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The regionalization of the mammalian spinal column is an important evolutionary, developmental, and functional hallmark of the clade. Vertebral column regions are usually defined using transitions in external bone morphology, such as the presence of transverse foraminae or rib facets, or measurements of vertebral shape. Yet the internal structure of vertebrae, specifically the trabecular (spongy) bone, plays an important role in vertebral function, and is subject to the same variety of selective, functional, and developmental influences as external bone morphology. Here, we investigated regionalization of external and trabecular bone morphology in the vertebral column of a group of shrews (family Soricidae). The primary goals of this study were to: (1) determine if vertebral trabecular bone morphology is regionalized in large shrews, and if so, in what configuration relative to external morphology; (2) assess correlations between trabecular bone regionalization and functional or developmental influences; and (3) determine if external and trabecular bone regionalization patterns provide clues about the function of the highly modified spinal column of the hero shrew Scutisorex. Trabecular bone is regionalized along the soricid vertebral column, but the configuration of trabecular bone regions does not match that of the external vertebral morphology, and is less consistent across individuals and species. The cervical region has the most distinct and consistent trabecular bone morphology, with dense trabeculae indicative of the ability to withstand forces in a variety of directions. Scutisorex exhibits an additional external morphology region compared to unmodified shrews, but this region does not correspond to a change in trabecular architecture. Although trabecular bone architecture is regionalized along the soricid vertebral column, and this regionalization is potentially related to bone functional adaptation, there are likely aspects of vertebral functional regionalization that are not detectable using trabecular bone morphology. For example, the external morphology of the Scutisorex lumbar spine shows signs of an extra functional region that is not apparent in trabecular bone analyses. It is possible that body size and locomotor mode affect the degree to which function is manifest in trabecular bone, and broader study across mammalian size and ecology is warranted to understand the relationship between trabecular bone morphology and other measures of vertebral function such as intervertebral range of motion.
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Affiliation(s)
- Stephanie M Smith
- Field Museum of Natural History, Negaunee Integrative Research Center, 1400 S DuSable Lake Shore Drive, Chicago IL 60605, USA
| | - Kenneth D Angielczyk
- Field Museum of Natural History, Negaunee Integrative Research Center, 1400 S DuSable Lake Shore Drive, Chicago IL 60605, USA
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Arlegi M, Pantoja-Pérez A, Veschambre-Couture C, Gómez-Olivencia A. Covariation between the cranium and the cervical vertebrae in hominids. J Hum Evol 2021; 162:103112. [PMID: 34894608 DOI: 10.1016/j.jhevol.2021.103112] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/26/2021] [Accepted: 10/26/2021] [Indexed: 11/16/2022]
Abstract
The analysis of patterns of integration is crucial for the reconstruction and understanding of how morphological changes occur in a taxonomic group throughout evolution. These patterns are relatively constant; however, both patterns and the magnitudes of integration may vary across species. These differences may indicate morphological diversification, in some cases related to functional adaptations to the biomechanics of organisms. In this study, we analyze patterns of integration between two functional and developmental structures, the cranium and the cervical spine in hominids, and we quantify the amount of divergence of each anatomical element through phylogeny. We applied these methods to three-dimensional data from 168 adult hominid individuals, summing a total of more than 1000 cervical vertebrae. We found the atlas (C1) and axis (C2) display the lowest covariation with the cranium in hominids (Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Gorilla beringei, Pongo pygmaeus). H. sapiens show a relatively different pattern of craniocervical correlation compared with chimpanzees and gorillas, especially in variables implicated in maintaining the balance of the head. Finally, the atlas and axis show lower magnitude of shape change during evolution than the rest of the cervical vertebrae, especially those located in the middle of the subaxial cervical spine. Overall, results suggest that differences in the pattern of craniocervical correlation between humans and gorillas and chimpanzees could reflect the postural differences between these groups. Also, the stronger craniocervical integration and larger magnitude of shape change during evolution shown by the middle cervical vertebrae suggests that they have been selected to play an active role in maintaining head balance.
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Affiliation(s)
- Mikel Arlegi
- Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA), Zona Educacional 4, Campus Sescelades URV (Edifici W3), 43007 Tarragona, Spain; Universitat Rovira i Virgili, Department d'Història i Història de l'Art, Avinguda de Catalunya 35, 43002 Tarragona, Spain.
| | - Ana Pantoja-Pérez
- Centro UCM-ISCIII de Investigación sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos 5 (Pabellón 14), 28029 Madrid, Spain
| | - Christine Veschambre-Couture
- UMR 5199 PACEA, Université de Bordeaux, Allée Geoffroy Saint Hilaire, Bâtiment B8, CS 50023, 33615, Pessac Cedex, France
| | - Asier Gómez-Olivencia
- Departamento de Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco-Euskal Herriko Unibertsitatea (UPV/EHU), Barrio Sarriena S/n, 48940 Leioa, Spain; Sociedad de Ciencias Aranzadi, Zorroagagaina 11, 20014 Donostia-San Sebastián, Spain; Centro UCM-ISCIII de Investigación sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos 5 (Pabellón 14), 28029 Madrid, Spain
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4
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Abstract
The axial skeleton of all vertebrates is composed of individual units known as vertebrae. Each vertebra has individual anatomical attributes, yet they can be classified in five different groups, namely cervical, thoracic, lumbar, sacral and caudal, according to shared characteristics and their association with specific body areas. Variations in vertebral number, size, morphological features and their distribution amongst the different regions of the vertebral column are a major source of the anatomical diversity observed among vertebrates. In this review I will discuss the impact of those variations on the anatomy of different vertebrate species and provide insights into the genetic origin of some remarkable morphological traits that often serve to classify phylogenetic branches or individual species, like the long trunks of snakes or the long necks of giraffes.
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5
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Fossoriality and evolutionary development in two Cretaceous mammaliamorphs. Nature 2021; 592:577-582. [PMID: 33828300 DOI: 10.1038/s41586-021-03433-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/09/2021] [Indexed: 02/02/2023]
Abstract
Mammaliamorpha comprises the last common ancestor of Tritylodontidae and Mammalia plus all its descendants1. Tritylodontids are nonmammaliaform herbivorous cynodonts that originated in the Late Triassic epoch, diversified in the Jurassic period2-5 and survived into the Early Cretaceous epoch6,7. Eutriconodontans have generally been considered to be an extinct mammalian group, although different views exist8. Here we report a newly discovered tritylodontid and eutriconodontan from the Early Cretaceous Jehol Biota of China. Eutriconodontans are common in this biota9, but it was not previously known to contain tritylodontids. The two distantly related species show convergent features that are adapted for fossorial life, and are the first 'scratch-diggers' known from this biota. Both species also show an increased number of presacral vertebrae, relative to the ancestral state in synapsids or mammals10,11, that display meristic and homeotic changes. These fossils shed light on the evolutionary development of the axial skeleton in mammaliamorphs, which has been the focus of numerous studies in vertebrate evolution12-17 and developmental biology18-28. The phenotypes recorded by these fossils indicate that developmental plasticity in somitogenesis and HOX gene expression in the axial skeleton-similar to that observed in extant mammals-was already in place in stem mammaliamorphs. The interaction of these developmental mechanisms with natural selection may have underpinned the diverse phenotypes of body plan that evolved independently in various clades of mammaliamorph.
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6
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Marek RD, Falkingham PL, Benson RBJ, Gardiner JD, Maddox TW, Bates KT. Evolutionary versatility of the avian neck. Proc Biol Sci 2021; 288:20203150. [PMID: 33653136 PMCID: PMC7934994 DOI: 10.1098/rspb.2020.3150] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column is a hierarchical morpho-functional appendage, with varying magnitudes of ecologically driven osteological variation at different scales of organization. Contrary to expectations given the widely varying ecological functions of necks in different species, we find that regional modularity of the avian neck is highly conserved, with an overall structural blueprint that is significantly altered only by the most mechanically demanding ecological functions. Nevertheless, the morphologies of vertebrae within subregions of the neck show more prominent signals of adaptation to ecological pressures. We also find that both neck length allometry and the nature of neck elongation in birds are different from other vertebrates. In contrast with mammals, neck length scales isometrically with head mass and, contrary to previous work, we show that neck elongation in birds is achieved predominantly by increasing vertebral lengths rather than counts. Birds therefore possess a cervical spine that may be unique in its versatility among extant vertebrates, one that, since the origin of flight, has adapted to function as a surrogate forelimb in varied ecological niches.
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Affiliation(s)
- Ryan D Marek
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Peter L Falkingham
- Biological and Environmental Sciences, James Parsons Building, Byrom Street, Liverpool L3 3AF, UK
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - James D Gardiner
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Thomas W Maddox
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Karl T Bates
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
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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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8
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Arlegi M, Veschambre‐Couture C, Gómez‐Olivencia A. Evolutionary selection and morphological integration in the vertebral column of modern humans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 171:17-36. [DOI: 10.1002/ajpa.23950] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/03/2019] [Accepted: 09/26/2019] [Indexed: 01/22/2023]
Affiliation(s)
- Mikel Arlegi
- Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y TecnologíaUniversidad del País Vasco‐Euskal Herriko Unibertsitatea (UPV/EHU) Leioa Spain
- Université de Bordeaux, PACEA UMR 5199 Pessac France
| | | | - Asier Gómez‐Olivencia
- Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y TecnologíaUniversidad del País Vasco‐Euskal Herriko Unibertsitatea (UPV/EHU) Leioa Spain
- IKERBASQUE. Basque Foundation for Science Bizkaia Spain
- Centro UCM‐ISCIII de Investigación sobre Evolución y Comportamiento Humanos Madrid Spain
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9
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Williams SA, Spear JK, Petrullo L, Goldstein DM, Lee AB, Peterson AL, Miano DA, Kaczmarek EB, Shattuck MR. Increased variation in numbers of presacral vertebrae in suspensory mammals. Nat Ecol Evol 2019; 3:949-956. [DOI: 10.1038/s41559-019-0894-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 04/08/2019] [Indexed: 11/09/2022]
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10
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Law CJ, Slater GJ, Mehta RS. Shared extremes by ectotherms and endotherms: Body elongation in mustelids is associated with small size and reduced limbs. Evolution 2019; 73:735-749. [PMID: 30793764 DOI: 10.1111/evo.13702] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 01/08/2023]
Abstract
An elongate body with reduced or absent limbs has evolved independently in many ectothermic vertebrate lineages. While much effort has been spent examining the morphological pathways to elongation in these clades, quantitative investigations into the evolution of elongation in endothermic clades are lacking. We quantified body shape in 61 musteloid mammals (red panda, skunks, raccoons, and weasels) using the head-body elongation ratio. We also examined the morphological changes that may underlie the evolution toward more extreme body plans. We found that a mustelid clade comprised of the subfamilies Helictidinae, Guloninae, Ictonychinae, Mustelinae, and Lutrinae exhibited an evolutionary transition toward more elongate bodies. Furthermore, we discovered that elongation of the body is associated with the evolution of other key traits such as a reduction in body size and a reduction in forelimb length but not hindlimb length. This relationship between body elongation and forelimb length has not previously been quantitatively established for mammals but is consistent with trends exhibited by ectothermic vertebrates and suggests a common pattern of trait covariance associated with body shape evolution. This study provides the framework for documenting body shapes across a wider range of mammalian clades to better understand the morphological changes influencing shape disparity across all vertebrates.
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Affiliation(s)
- Chris J Law
- Department of Ecology and Evolutionary Biology, Coastal Biology Building, University of California, Santa Cruz, California, 95060
| | - Graham J Slater
- Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, 60637
| | - Rita S Mehta
- Department of Ecology and Evolutionary Biology, Coastal Biology Building, University of California, Santa Cruz, California, 95060
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11
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Westphal N, Mahlow K, Head JJ, Müller J. Pectoral myology of limb-reduced worm lizards (Squamata, Amphisbaenia) suggests decoupling of the musculoskeletal system during the evolution of body elongation. BMC Evol Biol 2019; 19:16. [PMID: 30630409 PMCID: PMC6329177 DOI: 10.1186/s12862-018-1303-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 11/20/2018] [Indexed: 01/10/2023] Open
Abstract
Background The evolution of elongated body forms in tetrapods has a strong influence on the musculoskeletal system, including the reduction of pelvic and pectoral girdles, as well as the limbs. However, despite extensive research in this area it still remains unknown how muscles within and around bony girdles are affected by these reductions. Here we investigate this issue using fossorial amphisbaenian reptiles, or worm lizards, as a model system, which show substantial variation in the degree of reductions of girdles and limbs. Using iodine-based contrast-enhanced computed tomography (diceCT), we analyze the composition of the shoulder muscles of the main clades of Amphisbaenia and their outgroups relative to the pectoral skeleton. Results All investigated amphisbaenian taxa retain the full set of 17 shoulder muscles, independent of the degree of limb and girdle reductions, whereas in some cases muscles are fused to complexes or changed in morphology relative to the ancestral condition. Bipes is the only taxon that retains forelimbs and an almost complete pectoral girdle. All other amphisbaenian families show more variation concerning the completeness of the pectoral girdle having reduced or absent girdle elements. Rhineura, which undergoes the most severe bone reductions, differs from all other taxa in possessing elongated muscle strands instead of discrete shoulder muscles. In all investigated amphisbaenians, the shoulder muscle agglomerate is shortened and shifted anteriorly relative to the ancestral position as seen in the outgroups. Conclusions Our results show that pectoral muscle anatomy does not necessarily correspond to the loss or reduction of bones, indicating a decoupling of the musculoskeletal system. Muscle attachment sites change from bones to non-skeletal areas, such as surrounding muscles, skin or connective tissue, whereas muscle origins themselves remain in the same region where the pectoral bones were ancestrally located. Our findings indicate a high degree of developmental autonomy within the musculoskeletal system, we predict that the observed evolutionary rearrangements of amphisbaenian shoulder muscles were driven by functional demands rather than by developmental constraints. Nevertheless, worm lizards display a spatial offset of both pectoral bones and muscles relative to the ancestral position, indicating severe developmental modifications of the amphisbaenian body axis. Electronic supplementary material The online version of this article (10.1186/s12862-018-1303-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Natascha Westphal
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstr. 43, 10115, Berlin, Germany.
| | - Kristin Mahlow
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstr. 43, 10115, Berlin, Germany
| | - Jason James Head
- Department of Zoology and University Museum of Zoology, University of Cambridge, Downing St, Cambridge, CB2 3EJ, UK
| | - Johannes Müller
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstr. 43, 10115, Berlin, Germany
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12
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Montañez‐Rivera I, Nyakatura JA, Amson E. Bone cortical compactness in 'tree sloths' reflects convergent evolution. J Anat 2018; 233:580-591. [PMID: 30117161 PMCID: PMC6183012 DOI: 10.1111/joa.12873] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2018] [Indexed: 01/15/2023] Open
Abstract
Bone remodeling, one of the main processes that regulate bone microstructure, consists of bone resorption followed by the deposition of secondary bone at the same location. Remodeling intensity varies among taxa, but a characteristically compact cortex is ubiquitous in the long bones of mature terrestrial mammals. A previous analysis found that cortical bone in a few 'tree sloth' (Bradypus and Choloepus) specimens is heavily remodeled and characterized by numerous immature secondary osteons, suggesting that these animals were remodeling their bones at high rate until late in their ontogeny. This study aims at testing if this remodeling is generally present in 'tree sloths', using a quantitative analysis of the humeral cortical compactness (CC) among xenarthrans. The results of the investigation of humeral diaphyseal cross-sections of 26 specimens belonging to 10 xenarthran species including specimens from both extinct and extant species indicate that in 'tree sloths' the CC is significantly lower than in the other sampled xenarthrans. No significant difference was found between the CC of the two genera of 'tree sloths'. Our results are consistent with the hypothesis that the cortical bone of 'tree sloths' in general undergoes intense and balanced remodeling that is maintained until late (possibly throughout) in their ontogeny. In the light of xenarthran phylogeny, low CC represents another convergence between the long-separated 'tree sloth' lineages. Although the exact structural and/or functional demands that are associated with this trait are hitherto unknown, several hypotheses are suggested here, including a relationship to their relatively low metabolism and to the mechanical demands imposed upon the bones by the suspensory posture and locomotion, which was independently acquired by the two genera of 'tree sloths'.
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Affiliation(s)
- Irene Montañez‐Rivera
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
| | - John A. Nyakatura
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
- Bild Wissen Gestaltung. Ein interdisziplinäres LaborHumboldt UniversitätBerlinGermany
| | - Eli Amson
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
- Bild Wissen Gestaltung. Ein interdisziplinäres LaborHumboldt UniversitätBerlinGermany
- Museum für NaturkundeLeibniz‐Institut für Evolutions‐ und BiodiversitätsforschungBerlinGermany
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13
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Böhmer C, Amson E, Arnold P, van Heteren AH, Nyakatura JA. Homeotic transformations reflect departure from the mammalian 'rule of seven' cervical vertebrae in sloths: inferences on the Hox code and morphological modularity of the mammalian neck. BMC Evol Biol 2018; 18:84. [PMID: 29879896 PMCID: PMC5992679 DOI: 10.1186/s12862-018-1202-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/23/2018] [Indexed: 11/10/2022] Open
Abstract
Background Sloths are one of only two exceptions to the mammalian ‘rule of seven’ vertebrae in the neck. As a striking case of breaking the evolutionary constraint, the explanation for the exceptional number of cervical vertebrae in sloths is still under debate. Two diverging hypotheses, both ultimately linked to the low metabolic rate of sloths, have been proposed: hypothesis 1 involves morphological transformation of vertebrae due to changes in the Hox gene expression pattern and hypothesis 2 assumes that the Hox gene expression pattern is not altered and the identity of the vertebrae is not changed. Direct evidence supporting either hypothesis would involve knowledge of the vertebral Hox code in sloths, but the realization of such studies is extremely limited. Here, on the basis of the previously established correlation between anterior Hox gene expression and the quantifiable vertebral shape, we present the morphological regionalization of the neck in three different species of sloths with aberrant cervical count providing indirect insight into the vertebral Hox code. Results Shape differences within the cervical vertebral column suggest a mouse-like Hox code in the neck of sloths. We infer an anterior shift of HoxC-6 expression in association with the first thoracic vertebra in short-necked sloths with decreased cervical count, and a posterior shift of HoxC-5 and HoxC-6 expression in long-necked sloths with increased cervical count. Conclusion Although only future developmental analyses in non-model organisms, such as sloths, will yield direct evidence for the evolutionary mechanism responsible for the aberrant number of cervical vertebrae, our observations lend support to hypothesis 1 indicating that the number of modules is retained but their boundaries are displaced. Our approach based on quantified morphological differences also provides a reliable basis for further research including fossil taxa such as extinct ‘ground sloths’ in order to trace the pattern and the underlying genetic mechanisms in the evolution of the vertebral column in mammals. Electronic supplementary material The online version of this article (10.1186/s12862-018-1202-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christine Böhmer
- UMR 7179 CNRS/MNHN, Muséum National d'Histoire Naturelle, 57 rue Cuvier, CP-55, Paris, France.
| | - Eli Amson
- AG Morphologie und Formengeschichte, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany.,Image Knowledge Gestaltung: An Interdisciplinary Laboratory, Humboldt University, Philippstraße 13, 10115, Berlin, Germany.,Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany
| | - Patrick Arnold
- Institut für Zoologie und Evolutionsforschung mit Phyletischem Museum, Ernst-Haeckel-Haus und Biologiedidaktik, Friedrich-Schiller-Universität Jena, Erbertstraße 1, 07743, Jena, Germany.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
| | - Anneke H van Heteren
- Sektion Mammalogie, SNSB - Zoologische Staatssammlung, Münchhausenstraße 21, 81247, München, Germany.,GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Straße 10, 80333, Munich, Germany.,Department Biologie II, Ludwig-Maximilians-Universität München, Großhaderner Straße 2, 82152, Planegg-Martinsried, Germany
| | - John A Nyakatura
- AG Morphologie und Formengeschichte, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany.,Image Knowledge Gestaltung: An Interdisciplinary Laboratory, Humboldt University, Philippstraße 13, 10115, Berlin, Germany
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14
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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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15
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Villamil CI. Phenotypic integration of the cervical vertebrae in the Hominoidea (Primates). Evolution 2018; 72:490-517. [DOI: 10.1111/evo.13433] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 01/11/2018] [Accepted: 01/12/2018] [Indexed: 12/30/2022]
Affiliation(s)
- Catalina I. Villamil
- Department of Anthropology; Dickinson College; P.O. Box 1773 Carlisle Pennsylvania 17013
- Center for the Study of Human Origins, Department of Anthropology; New York University; 25 Waverly Place New York New York 10003
- New York Consortium in Evolutionary Primatology; New York New York 10024
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16
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Shape Covariation (or the Lack Thereof) Between Vertebrae and Other Skeletal Traits in Felids: The Whole is Not Always Greater than the Sum of Parts. Evol Biol 2018; 45:196-210. [PMID: 29755151 PMCID: PMC5938317 DOI: 10.1007/s11692-017-9443-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 12/18/2017] [Indexed: 12/25/2022]
Abstract
Within carnivorans, cats show comparatively little disparity in overall morphology, with species differing mainly in body size. However, detailed shape analyses of individual osteological structures, such as limbs or skulls, have shown that felids display significant morphological differences that correlate with their observed ecological and behavioural ranges. Recently, these shape analyses have been extended to the felid axial skeleton. Results demonstrate a functionally-partitioned vertebral column, with regions varying greatly in level of correlation between shape and ecology. Moreover, a clear distinction is evident between a phylogenetically-constrained neck region and a selection-responsive posterior spine. Here, we test whether this regionalisation of function reflected in vertebral column shape is also translated into varying levels of phenotypic integration between this structure and most other skeletal elements. We accomplish this comparison by performing pairwise tests of integration between vertebral and other osteological units, quantified with 3D geometric morphometric data and analysed both with and without phylogenetic correction. To our knowledge, this is the first study to test for integration across a comprehensive sample of whole-skeleton elements. Our results show that, prior to corrections, strong covariation is present between vertebrae across the vertebral column and all other elements, with the exception of the femur. However, most of these significant correlations disappear after correcting for phylogeny, which is a significant influence on cranial and limb morphology of felids and other carnivorans. Our results thus suggest that the vertebral column of cats displays relative independence from other skeletal elements and may represent several distinct evolutionary morphological modules.
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17
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Arnold P, Esteve-Altava B, Fischer MS. Musculoskeletal networks reveal topological disparity in mammalian neck evolution. BMC Evol Biol 2017; 17:251. [PMID: 29237396 PMCID: PMC5729486 DOI: 10.1186/s12862-017-1101-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The increase in locomotor and metabolic performance during mammalian evolution was accompanied by the limitation of the number of cervical vertebrae to only seven. In turn, nuchal muscles underwent a reorganization while forelimb muscles expanded into the neck region. As variation in the cervical spine is low, the variation in the arrangement of the neck muscles and their attachment sites (i.e., the variability of the neck's musculoskeletal organization) is thus proposed to be an important source of neck disparity across mammals. Anatomical network analysis provides a novel framework to study the organization of the anatomical arrangement, or connectivity pattern, of the bones and muscles that constitute the mammalian neck in an evolutionary context. RESULTS Neck organization in mammals is characterized by a combination of conserved and highly variable network properties. We uncovered a conserved regionalization of the musculoskeletal organization of the neck into upper, mid and lower cervical modules. In contrast, there is a varying degree of complexity or specialization and of the integration of the pectoral elements. The musculoskeletal organization of the monotreme neck is distinctively different from that of therian mammals. CONCLUSIONS Our findings reveal that the limited number of vertebrae in the mammalian neck does not result in a low musculoskeletal disparity when examined in an evolutionary context. However, this disparity evolved late in mammalian history in parallel with the radiation of certain lineages (e.g., cetartiodactyls, xenarthrans). Disparity is further facilitated by the enhanced incorporation of forelimb muscles into the neck and their variability in attachment sites.
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Affiliation(s)
- Patrick Arnold
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Borja Esteve-Altava
- Structure & Motion Lab, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
| | - Martin S. Fischer
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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18
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Böhmer C, Werneburg I. Deep time perspective on turtle neck evolution: chasing the Hox code by vertebral morphology. Sci Rep 2017; 7:8939. [PMID: 28827543 PMCID: PMC5566328 DOI: 10.1038/s41598-017-09133-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/21/2017] [Indexed: 12/24/2022] Open
Abstract
The unparalleled ability of turtle neck retraction is possible in three different modes, which characterize stem turtles, living side-necked (Pleurodira), and hidden-necked (Cryptodira) turtles, respectively. Despite the conservatism in vertebral count among turtles, there is significant functional and morphological regionalization in the cervical vertebral column. Since Hox genes play a fundamental role in determining the differentiation in vertebra morphology and based on our reconstruction of evolutionary genetics in deep time, we hypothesize genetic differences among the turtle groups and between turtles and other land vertebrates. We correlated anterior Hox gene expression and the quantifiable shape of the vertebrae to investigate the morphological modularity in the neck across living and extinct turtles. This permitted the reconstruction of the hypothetical ancestral Hox code pattern of the whole turtle clade. The scenario of the evolution of axial patterning in turtles indicates shifts in the spatial expression of HoxA-5 in relation to the reduction of cervical ribs in modern turtles and of HoxB-5 linked with a lower morphological differentiation between the anterior cervical vertebrae observed in cryptodirans. By comparison with the mammalian pattern, we illustrate how the fixed count of eight cervical vertebrae in turtles resulted from the emergence of the unique turtle shell.
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Affiliation(s)
- Christine Böhmer
- UMR 7179 CNRS/MNHN, Muséum National d'Histoire Naturelle, 57 rue Cuvier CP-55, 75005, Paris, France.
| | - Ingmar Werneburg
- Senckenberg Center for Human Evolution and Palaeoenvironment at Eberhard Karls Universität, Sigwartstr, 10, 72076, Tübingen, Germany.
- Fachbereich Geowissenschaften, Eberhard Karls Universität, Hölderlinstraße 12, D-72074, Tübingen, Germany.
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin, Invalidenstraße 43, 10115, Berlin, Germany.
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19
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Buchholtz EA, Gee JK. Finding sacral: Developmental evolution of the axial skeleton of odontocetes (Cetacea). Evol Dev 2017; 19:190-204. [PMID: 28726248 DOI: 10.1111/ede.12227] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Emily A. Buchholtz
- Department of Biological Sciences; Wellesley College; Wellesley Massachusetts
| | - Jessica K. Gee
- Department of Biological Sciences; Wellesley College; Wellesley Massachusetts
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20
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Böhmer C. Correlation between Hox code and vertebral morphology in the mouse: towards a universal model for Synapsida. ZOOLOGICAL LETTERS 2017; 3:8. [PMID: 28630745 PMCID: PMC5469011 DOI: 10.1186/s40851-017-0069-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 05/16/2017] [Indexed: 03/27/2024]
Abstract
BACKGROUND The importance of the cervical vertebrae as part of the skull-neck system in facilitating the success and diversity of tetrapods is clear. The reconstruction of its evolution, however, is problematic because of the variation in the number of vertebrae, making it difficult to identify homologous elements. Quantification of the morphological differentiation in the neck of diverse archosaurs established homologous units of vertebrae (i.e. modules) resulting from Hox gene expression patterns within the cervical vertebral column. The present study aims to investigate the modularity of the cervical vertebral column in the mouse and to reveal the genetic patterns and changes underlying the evolution of the neck of modern mammals and their extinct relatives. In contrast to modern mammals, non-mammalian synapsids are characterized by a variable cervical count, the presence of free cervical ribs and the presence of a separate CV1 centrum. How might these evolutionary modifications be associated with changes in the Hox code? RESULTS In combination with up-to-date information on cervical Hox gene expression including description of the vertebral phenotype of Hox knock-out mutants, the 3D landmark-based geometric morphometric approach demonstrates a correlation between Hox code and vertebral morphology in the mouse. There is evidence that the modularity of the neck of the mouse had already been established in the last common ancestor of mammals, but differed from that of non-mammalian synapsids. The differences that likely occurred during the evolution of synapsids include an anterior shift in HoxA-5 expression in relation to the reduction of cervical ribs and an anterior shift in HoxD-4 expression linked to the development of the highly differentiated atlas-axis complex, whereas the remaining Hox genes may have displayed a pattern similar to that in mammals on the basis of the high level of conservatism in the axial skeleton of this lineage. CONCLUSION Thus, the mouse Hox code provides a model for understanding the evolutionary mechanisms responsible for the great morphological adaptability of the cervical vertebral column in Synapsida. However, more studies in non-model organisms are required to further elucidate the evolutionary role of Hox genes in axial patterning of the unique mammalian body plan.
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Affiliation(s)
- Christine Böhmer
- UMR 7179 CNRS/MNHN, Muséum National d’Histoire Naturelle, 57 rue Cuvier CP-55, Paris, France
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21
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Randau M, Goswami A. Morphological modularity in the vertebral column of Felidae (Mammalia, Carnivora). BMC Evol Biol 2017; 17:133. [PMID: 28599641 PMCID: PMC5466766 DOI: 10.1186/s12862-017-0975-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/22/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Previous studies have demonstrated that the clear morphological differences among vertebrae across the presacral column are accompanied by heterogeneous functional signals in vertebral shape. Further, several lines of evidence suggest that the mammalian axial skeleton is a highly modular structure. These include its composition of serial units, a trade-off between high shape variance and strong conservation of vertebral count, and direct association of regions with anterior expression sites of Hox genes. Here we investigate the modular organisation of the presacral vertebral column of modern cats (Felidae, Carnivora, Mammalia) with pairwise comparisons of vertebral shape covariation (i.e. integration) and evaluate our results against hypotheses of developmental and functional modularity. We used three-dimensional geometric morphometrics to quantify vertebral shape and then assessed integration between pairs of vertebrae with phylogenetic two-block partial least square analysis (PLS). RESULTS Six modules were identified in the pairwise analyses (vertebrae included are designated as 'C' for cervical, 'T' for thoracic, and 'L' for lumbar): an anterior module (C1 to T1); a transitional module situated between the last cervicals and first thoracics (C6 to T2); an anterior to middle thoracic set (T4 to T8); an anticlinal module (T10 and T11); a posterior set composed of the last two thoracics and lumbars (T12 to L7); and a module showing covariation between the cervicals and the posterior set (T12 to L7). These modules reflect shared developmental pathways, ossification timing, and observed ecological shape diversification in living species of felids. CONCLUSIONS We show here that patterns of shape integration reflect modular organisation of the vertebral column of felids. Whereas this pattern corresponds with hypotheses of developmental and functional regionalisation in the axial skeleton, it does not simply reflect major vertebral regions. This modularity may also have permitted vertebral partitions, specifically in the posterior vertebral column, to be more responsive to selection and achieve higher morphological disparity than other vertebral regions.
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Affiliation(s)
- Marcela Randau
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, WC1E 6BT UK
| | - Anjali Goswami
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, WC1E 6BT UK
- Department of Earth Sciences, University College London, Gower Street, London, UK
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22
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Soul LC, Benson RBJ. Developmental mechanisms of macroevolutionary change in the tetrapod axis: A case study of Sauropterygia. Evolution 2017; 71:1164-1177. [PMID: 28240769 PMCID: PMC5485078 DOI: 10.1111/evo.13217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Revised: 02/05/2017] [Accepted: 02/19/2017] [Indexed: 01/29/2023]
Abstract
Understanding how developmental processes change on macroevolutionary timescales to generate body plan disparity is fundamental to the study of vertebrate evolution. Adult morphology of the vertebral column directly reflects the mechanisms that generate vertebral counts (somitogenesis) and their regionalisation (homeotic effects) during embryonic development. Sauropterygians were a group of Mesozoic marine reptiles that exhibited an extremely high disparity of presacral vertebral/somite counts. Using phylogenetic comparative methods, we demonstrate that somitogenesis and homeotic effects evolved in a co-ordinated way among sauropterygians, contrasting with the wider pattern in tetrapods, in which somitogenetic and homeotic shifts are uncorrelated. Changes in sauropterygian body proportions were primarily enabled by homeotic shifts, with a lesser, but important, contribution from differences in postpatterning growth among somites. High body plan plasticity was present in Triassic sauropterygians and was maintained among their Jurassic and Cretaceous descendants. The extreme disparity in the body plan of plesiosaurian sauropterygians did not result from accelerated rates of evolutionary change in neck length, but instead reflect this ancestral versatility of sauropterygian axial development. Our results highlight variation in modes of axial development among tetrapods, and show that heterogeneous statistical models can uncover novel macroevolutionary patterns for animal body plans and the developmental mechanisms that control them.
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Affiliation(s)
- Laura C. Soul
- Department of Paleobiology, National Museum of Natural HistorySmithsonian InstitutionWashingtonDistrict of Columbia20013
- Department of Earth SciencesUniversity of Oxford,OX1 3ANUnited Kingdom
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23
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Arnold P, Amson E, Fischer MS. Differential scaling patterns of vertebrae and the evolution of neck length in mammals. Evolution 2017; 71:1587-1599. [PMID: 28323340 DOI: 10.1111/evo.13232] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 03/06/2017] [Indexed: 12/13/2022]
Abstract
Almost all mammals have seven vertebrae in their cervical spines. This consistency represents one of the most prominent examples of morphological stasis in vertebrae evolution. Hence, the requirements associated with evolutionary modifications of neck length have to be met with a fixed number of vertebrae. It has not been clear whether body size influences the overall length of the cervical spine and its inner organization (i.e., if the mammalian neck is subject to allometry). Here, we provide the first large-scale analysis of the scaling patterns of the cervical spine and its constituting cervical vertebrae. Our findings reveal that the opposite allometric scaling of C1 and C2-C7 accommodate the increase of neck bending moment with body size. The internal organization of the neck skeleton exhibits surprisingly uniformity in the vast majority of mammals. Deviations from this general pattern only occur under extreme loading regimes associated with particular functional and allometric demands. Our results indicate that the main source of variation in the mammalian neck stems from the disparity of overall cervical spine length. The mammalian neck reveals how evolutionary disparity manifests itself in a structure that is otherwise highly restricted by meristic constraints.
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Affiliation(s)
- Patrick Arnold
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbert-Straße 1, D-07743, Jena, Germany.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, Germany
| | - Eli Amson
- AG Morphologie und Formengeschichte, Bild Wissen Gestaltung-ein interdisziplinäres Labor & Institut für Biologie, Humboldt-Universität zu Berlin, Philippstraße 12/13, D-10115, Berlin, Germany
| | - Martin S Fischer
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbert-Straße 1, D-07743, Jena, Germany
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24
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Randau M, Goswami A. Unravelling intravertebral integration, modularity and disparity in Felidae (Mammalia). Evol Dev 2017; 19:85-95. [DOI: 10.1111/ede.12218] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Marcela Randau
- Department of Genetics; Evolution and Environment; University College London; Darwin Building 218A, Gower Street London WC1E 6BT UK
| | - Anjali Goswami
- Department of Genetics; Evolution and Environment; University College London; Darwin Building 218A, Gower Street London WC1E 6BT UK
- Department of Earth Sciences; University College London; London UK
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25
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Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories. ORG DIVERS EVOL 2016. [DOI: 10.1007/s13127-016-0304-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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26
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Mekonen HK, Hikspoors JPJM, Mommen G, Köhler SE, Lamers WH. Development of the ventral body wall in the human embryo. J Anat 2016; 227:673-85. [PMID: 26467243 DOI: 10.1111/joa.12380] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2015] [Indexed: 11/29/2022] Open
Abstract
Migratory failure of somitic cells is the commonest explanation for ventral body wall defects. However, the embryo increases ~ 25-fold in volume in the period that the ventral body wall forms, so that differential growth may, instead, account for the observed changes in topography. Human embryos between 4 and 10 weeks of development were studied, using amira reconstruction and cinema 4D remodeling software for visualization. Initially, vertebrae and ribs had formed medially, and primordia of sternum and hypaxial flank muscle primordium laterally in the body wall at Carnegie Stage (CS)15 (5.5 weeks). The next week, ribs and muscle primordium expanded in ventrolateral direction only. At CS18 (6.5 weeks), separate intercostal and abdominal wall muscles differentiated, and ribs, sterna, and muscles began to expand ventromedially and caudally, with the bilateral sternal bars fusing in the midline after CS20 (7 weeks) and the rectus muscles reaching the umbilicus at CS23 (8 weeks). The near-constant absolute distance between both rectus muscles and approximately fivefold decline of this distance relative to body circumference between 6 and 10 weeks identified dorsoventral growth in the dorsal body wall as determinant of the 'closure' of the ventral body wall. Concomitant with the straightening of the embryonic body axis after the 6th week, the abdominal muscles expanded ventrally and caudally to form the infraumbilical body wall. Our data, therefore, show that the ventral body wall is formed by differential dorsoventral growth in the dorsal part of the body.
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Affiliation(s)
- Hayelom K Mekonen
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands
| | - Jill P J M Hikspoors
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands
| | - Greet Mommen
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands
| | - S Eleonore Köhler
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands
| | - Wouter H Lamers
- Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.,Tygat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
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27
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Randau M, Goswami A, Hutchinson JR, Cuff AR, Pierce SE. Cryptic complexity in felid vertebral evolution: shape differentiation and allometry of the axial skeleton. Zool J Linn Soc 2016. [DOI: 10.1111/zoj.12403] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Marcela Randau
- Department of Genetics, Evolution and Environment; University College London; London UK
| | - Anjali Goswami
- Department of Genetics, Evolution and Environment; University College London; London UK
| | - John R. Hutchinson
- Department of Genetics, Evolution and Environment; University College London; London UK
- Department of Comparative Biomedical Sciences and Structure & Motion Laboratory; The Royal Veterinary College; Hertfordshire UK
| | - Andrew R. Cuff
- Department of Genetics, Evolution and Environment; University College London; London UK
- Department of Comparative Biomedical Sciences and Structure & Motion Laboratory; The Royal Veterinary College; Hertfordshire UK
| | - Stephanie E. Pierce
- Department of Comparative Biomedical Sciences and Structure & Motion Laboratory; The Royal Veterinary College; Hertfordshire UK
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology; Harvard University; Cambridge MA USA
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28
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Woltering JM, Duboule D. Tetrapod axial evolution and developmental constraints; Empirical underpinning by a mouse model. Mech Dev 2015; 138 Pt 2:64-72. [PMID: 26238020 PMCID: PMC4678112 DOI: 10.1016/j.mod.2015.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Revised: 07/19/2015] [Accepted: 07/20/2015] [Indexed: 02/05/2023]
Abstract
The tetrapod vertebral column has become increasingly complex during evolution as an adaptation to a terrestrial life. At the same time, the evolution of the vertebral formula became subject to developmental constraints acting on the size of the cervical and thoraco-lumbar regions. In the course of our studies concerning the evolution of Hox gene regulation, we produced a transgenic mouse model expressing fish Hox genes, which displayed a reduced number of thoraco-lumbar vertebrae and concurrent sacral homeotic transformations. Here, we analyze this mutant stock and conclude that the ancestral, pre-tetrapodial Hox code already possessed the capacity to induce vertebrae with sacral characteristics. This suggests that alterations in the interpretation of the Hox code may have participated to the evolution of this region in tetrapods, along with potential modifications of the HOX proteins themselves. With its reduced vertebral number, this mouse stock violates a previously described developmental constraint, which applies to the thoraco-lumbar region. The resulting offset between motor neuron morphology, vertebral patterning and the relative positioning of hind limbs illustrates that the precise orchestration of the Hox-clock in parallel with other ontogenetic pathways places constraints on the evolvability of the body plan. A transgenic mouse line expressing fish Hox genes has anterior homeotic transformations. Fish Hox genes are capable of inducing tetrapod specific vertebral characters. A sacral Hox-code influences adult hindlimb position, yet not the position of limb budding.
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Affiliation(s)
- Joost M Woltering
- Department of Genetics and Evolution, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva, Switzerland
| | - Denis Duboule
- Department of Genetics and Evolution, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva, Switzerland; School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
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29
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The equine neck and its function during movement and locomotion. ZOOLOGY 2015; 118:364-76. [PMID: 26163862 DOI: 10.1016/j.zool.2015.03.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 02/20/2015] [Accepted: 03/24/2015] [Indexed: 11/22/2022]
Abstract
During both locomotion and body movements at stance, the head and neck of the horse are a major craniocaudal and lateral balancing mechanism employing input from the visual, vestibular and proprioceptive systems. The function of the equine neck has recently become the focus of several research groups; this is probably also feeding on an increase of interest in the equine neck in equestrian sports, with a controversial discussion of specific neck positions such as maximum head and neck flexion. The aim of this review is to offer an overview of new findings on the structures and functions of the equine neck, illustrating their interplay. The movement of the neck is based on intervertebral motion, but it is also an integral part of locomotion; this is illustrated by the different neck conformations in the breeds of horses used for various types of work. The considerable effect of the neck movement and posture onto the whole trunk and even the limbs is transmitted via bony, ligamentous and muscular structures. Also, the fact that the neck position can easily be influenced by the rider and/or by the employment of training aids makes it an important avenue for training of new movements of the neck as well as the whole horse. Additionally, the neck position also affects the cervical spinal cord as well as the roots of the spinal nerves; besides the commonly encountered long-term neurological effects of cervical vertebral disorders, short-term changes of neural and muscular function have also been identified in the maximum flexion of the cranial neck and head position. During locomotion, the neck stores elastic energy within the passive tissues such as ligaments, joint capsules and fasciae. For adequate stabilisation, additional muscle activity is necessary; this is learned and requires constant muscle training as it is essential to prevent excessive wear and tear on the vertebral joints and also repetitive or single trauma to the spinal nerves and the spinal cord. The capability for this stabilisation decreases with age in the majority of horses due to changes in muscle tissue, muscle coordination and consequently muscle strength.
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Jones KE. Evolutionary allometry of the thoracolumbar centra in felids and bovids. J Morphol 2015; 276:818-31. [PMID: 25773228 DOI: 10.1002/jmor.20382] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Revised: 01/29/2015] [Accepted: 02/03/2015] [Indexed: 11/07/2022]
Abstract
Mammals have evolved a remarkable range of body sizes, yet their overall body plan remains unaltered. One challenge of evolutionary biology is to understand the mechanisms by which this size diversity is achieved, and how the mechanical challenges associated with changing body size are overcome. Despite the importance of the axial skeleton in body support and locomotion, and much interest in the allometry of the appendicular skeleton, little is known about vertebral allometry outside primates. This study compares evolutionary allometry of the thoracolumbar centra in two families of quadrupedal running mammals: Felidae and Bovidae. I test the hypothesis that, as size increases, the thoracolumbar region will resist increasing loads by becoming a) craniocaudally shorter, and b) larger in cross-sectional area, particularly in the sagittal plane. Length, width, and height of the thoracolumbar centra of 23 felid and 34 bovid species were taken. Thoracic, prediaphragmatic, lumbar, and postdiaphragmatic lengths were calculated, and diameters were compared at three equivalent positions: the midthoracic, the diaphragmatic and the midlumbar vertebra. Allometric slopes were calculated using a reduced major axis regression, on both raw and independent contrasts data. Slopes and elevations were compared using an ANCOVA. As size increases the thoracolumbar centra become more robust, showing preferential reinforcement in the sagittal plane. There was less allometric shortening of the thoracic than the lumbar region, perhaps reflecting constraints due to its connection with the respiratory apparatus. The thoracic region was more robust in bovids than felids, whereas the lumbar region was longer and more robust in felids than bovids. Elongation of lumbar centra increases the outlever of sagittal bending at intervertebral joints, increasing the total pelvic displacement during dorsomobile running. Both locomotor specializations and functional regionalization of the axial skeleton appear to have influenced its response to increasing size.
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Affiliation(s)
- Katrina E Jones
- Center for Functional Anatomy and Evolution, Johns Hopkins University, 1830 East Monument st., Baltimore, Maryland, USA
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Meng QJ, Ji Q, Zhang YG, Liu D, Grossnickle DM, Luo ZX. Mammalian evolution. An arboreal docodont from the Jurassic and mammaliaform ecological diversification. Science 2015; 347:764-8. [PMID: 25678661 DOI: 10.1126/science.1260879] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A new docodontan mammaliaform from the Middle Jurassic of China has skeletal features for climbing and dental characters indicative of an omnivorous diet that included plant sap. This fossil expands the range of known locomotor adaptations in docodontans to include climbing, in addition to digging and swimming. It further shows that some docodontans had a diet with a substantial herbivorous component, distinctive from the faunivorous diets previously reported in other members of this clade. This reveals a greater ecological diversity in an early mammaliaform clade at a more fundamental taxonomic level not only between major clades as previously thought.
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Affiliation(s)
- Qing-Jin Meng
- Beijing Museum of Natural History, Beijing 100050 China
| | - Qiang Ji
- Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
| | | | - Di Liu
- Beijing Museum of Natural History, Beijing 100050 China
| | - David M Grossnickle
- Committee on Evolutionary Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Zhe-Xi Luo
- Committee on Evolutionary Biology, The University of Chicago, Chicago, IL 60637, USA. Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA.
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Luo ZX, Meng QJ, Ji Q, Liu D, Zhang YG, Neander AI. Evolutionary development in basal mammaliaforms as revealed by a docodontan. Science 2015; 347:760-4. [DOI: 10.1126/science.1260880] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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LeBlanc ARH, Reisz RR. New postcranial material of the early caseid Casea broilii Williston, 1910 (Synapsida: Caseidae) with a review of the evolution of the sacrum in Paleozoic non-mammalian synapsids. PLoS One 2014; 9:e115734. [PMID: 25545624 PMCID: PMC4278720 DOI: 10.1371/journal.pone.0115734] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 12/01/2014] [Indexed: 11/19/2022] Open
Abstract
Here we use the description of a new specimen of the small caseid synapsid Casea broilii that preserves the sacral, pelvic and hind limb regions in great detail and in three dimensions, as a unique opportunity to reevaluate the early stages in the evolution of the sacrum in the lineage that led to mammals. We place this new material in the context of sacral evolution in early caseid synapsids and conclude that the transition from two to three sacral vertebrae occurred in small-bodied species, suggesting that it was not an adaptation to heavy weight bearing. Furthermore, we compare descriptions of sacral anatomy among known early synapsids, including caseids, ophiacodontids, edaphosaurids, varanopids, and sphenacodontians and review sacral evolution in early synapsids. Based on the descriptions of new species of caseids, edaphosaurids, and varanopids over the past several decades, it is clear that a sacrum consisting of three vertebrae evolved independently at least four times in synapsids during the Late Carboniferous and Early Permian. Furthermore, similarities in the morphologies of the sacral vertebrae and ribs of these early synapsids lead us to conclude that an anterior caudal vertebra had been incorporated into the sacral series convergently in these groups. Given the repeated acquisition of a three-vertebra sacrum in early synapsids and no apparent link to body size, we argue that this sacral anatomy was related to more efficient terrestrial locomotion than to increased weight bearing.
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Affiliation(s)
- Aaron R. H. LeBlanc
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
- * E-mail:
| | - Robert R. Reisz
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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Buchholtz EA, Wayrynen KL, Lin IW. Breaking constraint: axial patterning in Trichechus (Mammalia: Sirenia). Evol Dev 2014; 16:382-93. [PMID: 25339599 DOI: 10.1111/ede.12103] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Meristic variation is often limited in serially homologous systems with high internal differentiation and high developmental modularity. The mammalian neck, an extreme example, has a fixed (at seven) count of diversely specialized segments. Imposition of the mammalian cervical constraint has been tentatively linked to the origin of the diaphragm, which is muscularized by cells that migrate from cervical somites during development. With six cervical vertebrae, the genus Trichechus (manatee) has apparently broken this constraint, although the mechanism of constraint escape is unknown. Hypotheses for the developmental origin of Trichechus cervical morphology include cervical rib 7 repatterning, a primaxial/abaxial patterning shift, and local homeosis at the cervical/thoracic boundary. We tested predictions of these hypotheses by documenting vertebral morphology, axial ossification patterns, regionalization of the postcranial skeleton, and the relationship of thoracic ribs to sternal subunits in a large data set of fetal and adult Trichechus and Dugong specimens. These observations forced rejection of all three hypotheses. We propose alternatively that a global slowing of the rate of somitogenesis reduced somite count and disrupted alignment of Hox-generated anatomical markers relative to somite (and vertebral) boundaries throughout the Trichechus column. This hypothesis is consistent with observations of the full range of traditional cervical morphologies in the six cervical vertebrae, conserved postcranial proportions, and column-wide reduction in count relative to its sister taxon, Dugong. It also suggests that the origin of the mammalian cervical constraint lies in patterning, not in count, and that Trichechus and the tree sloths have broken the constraint using different developmental mechanisms.
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Affiliation(s)
- Emily A Buchholtz
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA
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Ossification sequence and genetic patterning in the mouse axial skeleton. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 322:631-42. [DOI: 10.1002/jez.b.22590] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 06/01/2014] [Accepted: 06/25/2014] [Indexed: 01/06/2023]
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Axial systems and their actuation: new twists on the ancient body of craniates. ZOOLOGY 2013; 117:1-6. [PMID: 24468089 DOI: 10.1016/j.zool.2013.11.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Accepted: 11/26/2013] [Indexed: 11/24/2022]
Abstract
Craniate animals--vertebrates and their jawless sister taxa--have evolved a body axis with powerful muscles, a distributed nervous system to control those muscles, and an endoskeleton that starts at the head and ends at the caudal fin. The body axis undulates, bends, twists, or holds firm, depending on the behavior. In this introduction to the special issue on axial systems and their actuation, we provide an overview of the latest research on how the body axis functions, develops, and evolves. Based on this research, we hypothesize that the body axis of craniates has three primary, post-cranial modules: precaudal, caudal, and tail. The term "module" means a portion of the body axis that functions, develops, and evolves in relative independence from other modules; "relative independence" means that structures and processes within a module are more tightly correlated in function, development, and behavior than the same processes are among modules.
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