1
|
Belyaev RI, Nikolskaia P, Bushuev AV, Panyutina AA, Kozhanova DA, Prilepskaya NE. Running, jumping, hunting, and scavenging: Functional analysis of vertebral mobility and backbone properties in carnivorans. J Anat 2024; 244:205-231. [PMID: 37837214 PMCID: PMC10780164 DOI: 10.1111/joa.13955] [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: 05/01/2023] [Revised: 09/06/2023] [Accepted: 09/07/2023] [Indexed: 10/15/2023] Open
Abstract
Carnivorans are well-known for their exceptional backbone mobility, which enables them to excel in fast running and long jumping, leading to them being among the most successful predators amongst terrestrial mammals. This study presents the first large-scale analysis of mobility throughout the presacral region of the vertebral column in carnivorans. The study covers representatives of 6 families, 24 genera and 34 species. We utilized a previously developed osteometry-based method to calculate available range of motion, quantifying all three directions of intervertebral mobility: sagittal bending (SB), lateral bending (LB), and axial rotation (AR). We observed a strong phylogenetic signal in the structural basis of the vertebral column (vertebral and joint formulae, length proportions of the backbone modules) and an insignificant phylogenetic signal in most characteristics of intervertebral mobility. This indicates that within the existing structure (stabilization of which occurred rather early in different phylogenetic lineages), intervertebral mobility in carnivorans is quite flexible. Our findings reveal that hyenas and canids, which use their jaws to seize prey, are characterized by a noticeably elongated cervical region and significantly higher SB and LB mobility of the cervical joints compared to other carnivorans. In representatives of other carnivoran families, the cervical region is very short, but the flexibility of the neck (both SB and LB) is significantly higher than that of short-necked odd-toed and even-toed ungulates. The lumbar region of the backbone in carnivorans is dorsomobile in the sagittal plane, being on average ~23° more mobile than in artiodactyls and ~38° more mobile than in perissodactyls. However, despite the general dorsomobility, only some representatives of Canidae, Felidae, and Viverridae are superior in lumbar flexibility to the most dorsomobile ungulates. The most dorsomobile artiodactyls are equal or even superior to carnivorans in their ability to engage in dorsal extension during galloping. In contrast, carnivorans are far superior to ungulates in their ability to engage ventral flexion. The cumulative SB in the lumbar region in carnivorans largely depends on the mode of running and hunting. Thus, adaptation to prolonged and enduring pursuit of prey in hyenas is accompanied by markedly reduced SB flexibility in the lumbar region. A more dorsostable run is also a characteristic of the Ursidae, and the peculiar maned wolf. Representatives of Felidae and Canidae have significantly more available SB mobility in the lumbar region. However, they fully engage it only occasionally at key moments of the hunt associated with the direct capture of the prey or when running in a straight line at maximum speed.
Collapse
Affiliation(s)
- Ruslan I. Belyaev
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesMoscowRussian Federation
| | - Polina Nikolskaia
- Geological InstituteRussian Academy of SciencesMoscowRussian Federation
| | - Andrey V. Bushuev
- Department of Vertebrate Zoology, Faculty of BiologyLomonosov Moscow State UniversityMoscowRussian Federation
| | | | - Darya A. Kozhanova
- Department of Paleontology, Faculty of GeologyLomonosov Moscow State UniversityMoscowRussian Federation
| | - Natalya E. Prilepskaya
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesMoscowRussian Federation
| |
Collapse
|
2
|
Belyaev RI, Kuznetsov AN, Prilepskaya NE. Truly dorsostable runners: Vertebral mobility in rhinoceroses, tapirs, and horses. J Anat 2023; 242:568-591. [PMID: 36519561 PMCID: PMC10008283 DOI: 10.1111/joa.13799] [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: 05/30/2022] [Revised: 11/16/2022] [Accepted: 11/20/2022] [Indexed: 12/23/2022] Open
Abstract
The vertebral column is a hallmark of vertebrates; it is the structural basis of their body and the locomotor apparatus in particular. Locomotion of any vertebrate animal in its typical habitat is directly associated with functional adaptations of its vertebrae. This study is the first large-scale analysis of mobility throughout the presacral region of the vertebral column covering a majority of extant odd-toed ungulates from 6 genera and 15 species. In this study, we used a previously developed osteometry-based method to calculate available range of motion. We quantified all three directions of intervertebral mobility: sagittal bending (SB), lateral bending (LB), and axial rotation (AR). The cervical region in perissodactyls was found to be the most mobile region of the presacral vertebral column in LB and SB. Rhinoceroses and tapirs are characterized by the least mobile necks in SB among odd-toed and even-toed ungulates. Equidae are characterized by very mobile necks, especially in LB. The first intrathoracic joint (T1-T2) in Equidae and Tapiridae is characterized by significantly increased mobility in the sagittal plane compared to the typical thoracic joints and is only slightly less mobile than typical cervical joints. The thoracolumbar part of the vertebral column in odd-toed ungulates is very stiff. Perissodactyls are characterized by frequent fusions of vertebrae with each other with complete loss of mobility. The posterior half of the thoracic region in perissodactyls is characterized by especially stiff intervertebral joints in the SB direction. This is probably associated with hindgut fermentation in perissodactyls: the sagittal stiffness of the posterior thoracic region of the vertebral column is able to passively support the hindgut heavily loaded with roughage. Horses are known as a prime example of a dorsostable galloper among mammals. However, based on SB in the lumbosacral part of the backbone, equids appear to be the least dorsostable among extant perissodactyls; the cumulative SB in equids and tapirs is as low as in the largest representatives of artiodactyls, while in Rhinocerotidae it is even lower representing the minimum across all odd-toed and even-toed ungulates. Morphological features of small Paleogene ancestors of rhinoceroses and equids indicate that dorsostability is a derived feature of perissodactyls and evolved convergently in the three extant families.
Collapse
Affiliation(s)
- Ruslan I Belyaev
- A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russian Federation
| | - Alexander N Kuznetsov
- A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russian Federation.,Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, Russian Federation
| | - Natalya E Prilepskaya
- A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russian Federation
| |
Collapse
|
3
|
Belyaev RI, Kuznetsov AN, Prilepskaya NE. How the even-toed ungulate vertebral column works: Comparison of intervertebral mobility in 33 genera. J Anat 2021; 239:1370-1399. [PMID: 34365661 PMCID: PMC8602029 DOI: 10.1111/joa.13521] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 07/03/2021] [Accepted: 07/07/2021] [Indexed: 11/28/2022] Open
Abstract
In this study, we used a previously developed osteometry-based method to calculate available range of motion in presacral intervertebral joints in artiodactyls. We have quantified all three directions of intervertebral mobility: sagittal bending (SB), lateral bending (LB), and axial rotation (AR). This research covers 10 extant families of artiodactyls from 33 genera and 39 species. The cervical region in artiodactyls is the most mobile region of the presacral vertebral column in SB and LB. Mobility is unevenly distributed throughout the joints of the neck. The posterior neck joints (C4-C7) are significantly more mobile (on average by 2.5-3.5°) to anterior joints (C2-C4) and to the neck-thorax joint (C7-T1) in SB and LB. An increase in the relative length of the cervical region in artiodactyls is accompanied by an increase in the bending amplitudes (SB: Pearson r = 0.781; LB: r = 0.884). Animals with the most mobile necks (representative of Giraffidae and Camelidae) are 2-3 times more mobile in SB and LB compared to species with the least mobile necks. The thoracic region in artiodactyls, as in other mammals, is characterized by the greatest amplitudes of AR due to the tangential orientation of the zygapophyseal articular facets. The lowest AR values in the thoracic region are typical for the heaviest artiodactyls-Hippopotamidae. The highest AR values are typical for such agile runners as cervids, musk deer, pronghorn, as well as large and small antelopes. SB mobility in the posterior part of the thoracic region can be used by artiodactyls during galloping. The highest values of SB aROM in the posterior part of the thoracic region are typical for small animals with high SB mobility in the lumbar region. The lumbar region in mammals is adapted for efficient SB. Both the cumulative and average SB values in the lumbar region showed correspondence to the running type employed by an artiodactyl. The greatest SB amplitudes in the lumbar region are typical for small animals, which use saltatorial and saltatorial-cursorial running. An increase in body size also corresponds to a decrease in lumbar SB amplitudes. The lowest SB amplitudes are typical for species using the so-called mediportal running. Adaptation to endurance galloping in open landscapes is accompanied by a decrease in lumbar SB amplitudes in artiodactyls. The consistency of the approach used and the wide coverage of the studied species make it possible to significantly expand and generalize the knowledge of the biomechanics of the vertebral column in artiodactyls.
Collapse
Affiliation(s)
- Ruslan I. Belyaev
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesMoscowRussian Federation
| | | | - Natalya E. Prilepskaya
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesMoscowRussian Federation
| |
Collapse
|
4
|
Müller MA, Merten LJF, Böhmer C, Nyakatura JA. Pushing the boundary? Testing the "functional elongation hypothesis" of the giraffe's neck. Evolution 2021; 75:641-655. [PMID: 33443310 DOI: 10.1111/evo.14171] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 11/28/2022]
Abstract
Although giraffes maintain the usual mammalian cervical number of seven vertebrae, their first thoracic vertebra (T1) exhibits aberrant anatomy and has been hypothesized to functionally elongate the neck. We test this "functional elongation hypothesis" by combining phylogenetically informed analyses of neck length, three-dimensional (3D) vertebral shape, and of the functional significance of shape differences across a broad sample of ruminants and camelids. Digital bone models of the cervicothoracic transition were subjected to 3D geometric morphometric analysis revealing how the shape of the seventh cervical (C7) has converged in several long-necked species. However, we find a unique "cervicalization" of the giraffe's T1. In contrast, we demonstrate a "thoracalization" of C7 for the European bison. Other giraffids (okapi and extinct Sivatherium) did not exhibit "cervicalized" T1 morphology. Quantitative range of motion (ROM) analysis at the cervicothoracic transition in ruminants and camelids confirms the "functional elongation hypothesis" for the giraffe in terms of increased mobility, especially with regard to dorsoventral flexion/extension. Additionally, other factors related to the unique morphology of the giraffe's cervicothoracic transition such as neck posture and intervertebral stability are discussed and should be considered in future studies of giraffe neck evolution.
Collapse
Affiliation(s)
- Marilena A Müller
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Luisa J F Merten
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Christine Böhmer
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, Paris, 75005, France.,Department für Geo- und Umweltwissenschaften und GeoBio-Center, Ludwig-Maximilians-Universität München, München, 80333, Germany
| | - John A Nyakatura
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| |
Collapse
|
5
|
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.
Collapse
|
6
|
Vidal D, Mocho P, Aberasturi A, Sanz JL, Ortega F. High browsing skeletal adaptations in Spinophorosaurus reveal an evolutionary innovation in sauropod dinosaurs. Sci Rep 2020; 10:6638. [PMID: 32313018 PMCID: PMC7171156 DOI: 10.1038/s41598-020-63439-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 03/31/2020] [Indexed: 11/09/2022] Open
Abstract
Sauropods were among the most diverse lineages of dinosaurs, with an ample geographic distribution throughout the Mesozoic. This evolutionary success is largely attributed to neck elongation and its impact on feeding efficiency. However, how neck elongation influenced exactly on feeding strategies is subject of debate. The process of mounting a nearly complete virtual skeleton of Spinophorosaurus nigerensis, from the Middle (?) Jurassic of Niger, has revealed several previously unknown osteological adaptations in this taxon. Wedged sacral and posterior dorsal vertebrae cause the presacral column to deflect antero-dorsally. This, together with elongated scapulae and humeri make the anterior region of the skeleton vertically lengthened. Also, elongated prezygapophyseal facets on the cervical vertebrae and a specialized first dorsal vertebra greatly increase the vertical range of motion of the neck. These characters support this early eusauropod as a more capable high browser than more basally branching sauropods. While limb proportions and zygapophyseal facets vary among Eusauropoda, the sacrum retained more than 10° of wedging in all Eusauropoda. This implied a functional constraint for sauropod species which evolved lower browsing feeding strategies: the antero-dorsal sloping caused by the sacrum had to be counteracted with further skeletal modifications, e.g. a ventrally curved mid to anterior presacral spine to hinder the dorsal slope of the whole presacral series caused by the wedged sacrum. This suggests that at least the last common ancestor of Eusauropoda developed high browsing capabilities, partially due to the modified wedged sacrum, likely a potential synapomorphy of the clade and key in the evolutionary history of the group.
Collapse
Affiliation(s)
- D Vidal
- Grupo de Biología Evolutiva, Facultad de Ciencias, UNED, Paseo Senda Del Rey, 9, 28040, Madrid, Spain.
| | - P Mocho
- Grupo de Biología Evolutiva, Facultad de Ciencias, UNED, Paseo Senda Del Rey, 9, 28040, Madrid, Spain
- Instituto Dom Luiz, Universidade de Lisboa, Bloco C6, 38Piso, sala 6.3.57, Campo Grande, 1749-016, Lisbon, Portugal
- The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Blvd., 90007, CA, Los Angeles, USA
| | - A Aberasturi
- Museo Paleontológico de Elche, Carrer Sant Joan, 3, 03203, Elche, Spain
| | - J L Sanz
- Unidad de Paleontología, Facultad de Ciencias, Universidad Autónoma de Madrid, Calle Darwin, 2, 28049, Madrid, Spain
- Real Academia Española de Ciencias Exactas, Físicas y Naturales, Calle Valverde, 24, 28004, Madrid, Spain
| | - F Ortega
- Grupo de Biología Evolutiva, Facultad de Ciencias, UNED, Paseo Senda Del Rey, 9, 28040, Madrid, Spain
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
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
| |
Collapse
|
9
|
Growth Pattern and Functional Morphology of the Cervical Vertebrae in the Gerenuk (Litocranius walleri): The Evolution of Neck Elongation in Antilopini (Bovidae, Artiodactyla). J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9396-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Williams EM. Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism. BIOLOGY 2016; 5:biology5030035. [PMID: 27626454 PMCID: PMC5037354 DOI: 10.3390/biology5030035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/07/2016] [Indexed: 11/16/2022]
Abstract
Giraffe (Giraffa camelopardalis), with their long neck and legs, are unique amongst mammals. How these features evolved is a matter of conjecture. The two leading ideas are the high browse and the sexual-selection hypotheses. While both explain many of the characteristics and the behaviour of giraffe, neither is fully supported by the available evidence. The extended viewing horizon afforded by increased height and a need to maintain horizon vigilance, as a mechanism favouring the evolution of increased height is reviewed. In giraffe, vigilance of predators whilst feeding and drinking are important survival factors, as is the ability to interact with immediate herd members, young and male suitors. The evidence regarding giraffe vigilance behaviour is sparse and suggests that over-vigilance has a negative cost, serving as a distraction to feeding. In woodland savannah, increased height allows giraffe to see further, allowing each giraffe to increase the distance between its neighbours while browsing. Increased height allows the giraffe to see the early approach of predators, as well as bull males. It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.
Collapse
Affiliation(s)
- Edgar M Williams
- Faculty of Life Sciences and Education, University of South Wales, Wales CF37 1DL, UK; ; Tel.: +44-1443-483-893.
| |
Collapse
|