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McLean CJ, Brassey CA, Seiter M, Garwood RJ, Gardiner JD. The kinematics of amblypygid (Arachnida) pedipalps during predation: extreme elongation in raptorial appendages does not result in a proportionate increase in reach and closing speed. J Exp Biol 2024; 227:jeb246654. [PMID: 38304965 DOI: 10.1242/jeb.246654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 01/26/2024] [Indexed: 02/03/2024]
Abstract
The link between form and function is key to understanding the evolution of unique and/or extreme morphologies. Amblypygids, or whip spiders, are arachnids that often have highly elongated spined pedipalps. These limbs are used to strike at, and secure, prey before processing by the chelicerae. Amblypygi pedipalps are multifunctional, however, being used in courtship and contest, and vary greatly in form between species. Increased pedipalp length may improve performance during prey capture, but length could also be influenced by factors including territorial contest and sexual selection. Here, for the first time, we used high-speed videography and manual tracking to investigate kinematic differences in prey capture between amblypygid species. Across six morphologically diverse species, spanning four genera and two families, we created a total dataset of 86 trials (9-20 per species). Prey capture kinematics varied considerably between species, with differences being expressed in pedipalp joint angle ranges. In particular, maximum reach ratio did not remain constant with total pedipalp length, as geometric scaling would predict, but decreased with longer pedipalps. This suggests that taxa with the most elongated pedipalps do not deploy their potential length advantage to proportionally increase reach. Therefore, a simple mechanical explanation of increased reach does not sufficiently explain pedipalp elongation. We propose other factors to help explain this phenomenon, such as social interactions or sexual selection, which would produce an evolutionary trade-off in pedipalp length between prey capture performance and other behavioural and/or anatomical pressures.
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Affiliation(s)
- Callum J McLean
- The School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, Scotland, UK
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester M15 6BH, UK
| | - Charlotte A Brassey
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester M15 6BH, UK
| | - Michael Seiter
- Department of Evolutionary Biology, Unit Integrative Zoology, University of Vienna, 1010 Vienna, Austria
- Naturhistorisches Museum Wien, 1010 Vienna, Austria
| | - Russell J Garwood
- Department of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PY, UK
- The Natural History Museum, London SW7 5BD, UK
| | - James D Gardiner
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester M15 6BH, UK
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2
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Amino K, Matsuo T. Reproductive advantage of the winners of male-male competition in Drosophila prolongata. Behav Processes 2023; 206:104831. [PMID: 36693576 DOI: 10.1016/j.beproc.2023.104831] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/16/2022] [Accepted: 01/20/2023] [Indexed: 01/22/2023]
Abstract
In the resource-defence mating system, where males compete for limited resources to acquire females, male traits associated with fighting ability are selected, leading to the evolution of sexual dimorphism. However, the evolution of sexual dimorphism is also driven by other mechanisms, such as female selection. Therefore, to elucidate the evolutionary mechanisms of male traits, it is necessary to clarify their contribution to fitness through male-male competition. In this regard, it is surprising that numerous studies on sexually dimorphic species have assumed the resource-defence mating system without directly examining the relationship between resource-defending behaviour and mating success. In a sexually dimorphic fruit fly, Drosophila prolongata, the presence of the resource-defence mating system has been suggested, but technical difficulties had prevented spatial quantification of the resource-defending behaviour. In this study, by using an automated behaviour analysis tool previously developed, we located the occurrence of male-male competition and courtship to investigate their relationship in D. prolongata, considering the position of food resources. We found that the male-male competition led to the exclusive occupation of resources, increasing the courtship opportunities of the resource holders. These results illustrate the importance of resource-defending for reproductive success in D. prolongata.
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Affiliation(s)
- Kai Amino
- Laboratory of Applied Entomology, Department of Agricultural and Environmental Biology, The University of Tokyo, Japan.
| | - Takashi Matsuo
- Laboratory of Applied Entomology, Department of Agricultural and Environmental Biology, The University of Tokyo, Japan
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3
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Roithmair Z, Edgecombe GD, Wanninger A, Akkari N. Sexually dimorphic characters of the ultimate legs in lithobiid centipedes (Myriapoda, Chilopoda, and Lithobiomorpha): Morphology and implications for reproductive behavior. J Morphol 2023; 284:e21549. [PMID: 36538584 DOI: 10.1002/jmor.21549] [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: 05/27/2022] [Revised: 11/29/2022] [Accepted: 12/10/2022] [Indexed: 12/24/2022]
Abstract
Many species of lithobiomorph centipedes present a pronounced sexual dimorphism reflected in remarkable structural modifications on the ultimate legs of males. Most records of these male secondary sexual characters addressed taxonomy, helping to identify and characterize species or diagnose genera, but information on their diversity, detailed morphology and possible function(s) is scarce. In this study, nine species of the two lithobiid genera Lithobius Leach, 1814 and Eupolybothrus Verhoeff, 1907 were investigated, using light and scanning electron microscopy to document the detailed morphology of secondary sexual characters of male ultimate legs. Secondary sexual characters affecting the cuticle of the ultimate legs are described in detail and found to often be associated with sensilla, interpreted here as chemo- and mechanoreceptors, and with clusters of pores, a hitherto undescribed pore-distribution for this group. The tibial nodule of the species Lithobius nodulipes Latzel, 1880, was additionally examined with histological semi-thin sections. These results revealed that the clustered pores are connected to glandular tissue, and are, based on their morphology, interpreted as openings of flexo-canal epidermal glands. The presence of various sensory and glandular structures associated with sexual dimorphism indicates a likely role during courtship and mating. The closely related species examined in this research show comparable dimorphic structures, which are otherwise species-specific. Morphological observations on secondary sexual structures inform on reproductive biology in groups like lithobiomorphs for which there are limited behavioral data.
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Affiliation(s)
- Zita Roithmair
- Department of Invertebrate Zoology III, Natural History Museum Vienna, Vienna, Austria.,Department of Evolutionary Biology, Unit for Integrative Zoology, Vienna, Austria
| | | | - Andreas Wanninger
- Department of Evolutionary Biology, Unit for Integrative Zoology, Vienna, Austria
| | - Nesrine Akkari
- Department of Invertebrate Zoology III, Natural History Museum Vienna, Vienna, Austria
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4
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Réveillion F, Montuire S, Maquart PO, Fétiveau C, Bollache L. Variations in the carapace shape of whip spiders (Arachnida: Amblypygi). J Morphol 2022; 283:1003-1014. [PMID: 35670656 DOI: 10.1002/jmor.21485] [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: 12/09/2021] [Revised: 05/03/2022] [Accepted: 05/21/2022] [Indexed: 11/06/2022]
Abstract
Morphological studies often need to reference body size to correctly characterise the shape of organisms. In arthropods, the most commonly used reference for this is the length or width of the carapace, thorax, or the prosoma in the case of chelicerates. However, in the case of animals with unlimited growth, such as whip spiders, this measure could be irrelevant if growth is allometric. In this study, we analyse the ontogenetic modifications in prosoma outline shape in whip spiders during growth and compare the differences in shape between species. Differences are important for the relative prosoma width between species and, in the case of Damon medius, during growth in the juvenile stages, whereas the shape remains stable in mature stages. We conclude that a one-dimensional measure (i.e., length or width) suffices for mature specimens of a single species or family, but for larger studies, or when including immature specimens, at least the prosoma area (within the outline shape) should be used as a size estimator.
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Affiliation(s)
- Florian Réveillion
- Université de Bourgogne Franche Comté, Dijon, France.,Laboratoire Chrono-Environnement, UMR 6249, CNRS, Université Bourgogne Franche-Comté, Besançon, France
| | - Sophie Montuire
- Biogéosciences, UMR 6282, CNRS, Université Bourgogne Franche-Comté, Dijon, France.,EPHE, PSL University, Dijon, France
| | - Pierre-Olivier Maquart
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | | | - Loïc Bollache
- Université de Bourgogne Franche Comté, Dijon, France.,Laboratoire Chrono-Environnement, UMR 6249, CNRS, Université Bourgogne Franche-Comté, Besançon, France
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5
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Schmidt M, Melzer RR, Plotnick RE, Bicknell RD. Spines and baskets in apex predatory sea scorpions uncover unique feeding strategies using 3D-kinematics. iScience 2022; 25:103662. [PMID: 35024591 PMCID: PMC8733173 DOI: 10.1016/j.isci.2021.103662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 11/21/2021] [Accepted: 12/16/2021] [Indexed: 11/28/2022] Open
Abstract
Megalograptidae and Mixopteridae with elongate, spinose prosomal appendages are unique early Palaeozoic sea scorpions (Eurypterida). These features were presumably used for hunting, an untested hypothesis. Here, we present 3D model-based kinematic range of motion (ROM) analyses of Megalograptus ohioensis and Mixopterus kiaeri and compare these to modern analogs. This comparison confirms that the eurypterid appendages were likely raptorial, used in grabbing and holding prey for consumption. The Megalograptus ohioensis model illustrates notable Appendage III flexibility, indicating hypertrophied spines on Appendage III may have held prey, while Appendage II likely ripped immobilized prey. Mixopterus kiaeri, conversely, constructed a capture basket with Appendage III, and impaled prey with Appendage II elongated spines. Thus, megalograptid and mixopterid frontalmost appendages constructed a double basket system prior to moving dismembered prey to the chelicerae. Such 3D kinematic modeling presents a more complete understanding of these peculiar euchelicerates and highlights their possible position within past ecosystems.
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Affiliation(s)
- Michel Schmidt
- Bavarian State Collection of Zoology, Bavarian Natural History Collections, Munich, Germany
- Department Biology II, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Roland R. Melzer
- Bavarian State Collection of Zoology, Bavarian Natural History Collections, Munich, Germany
- Department Biology II, Ludwig-Maximilians-Universität München, Munich, Germany
- GeoBio-Center, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Roy E. Plotnick
- Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Russell D.C. Bicknell
- Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, Australia
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Schmidt M, Melzer RR, Bicknell RDC. Kinematics of whip spider pedipalps: a 3D comparative morpho-functional approach. Integr Zool 2021; 17:156-167. [PMID: 34532979 DOI: 10.1111/1749-4877.12591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/12/2021] [Accepted: 09/14/2021] [Indexed: 11/30/2022]
Abstract
Amblypygi are tropical and subtropical ambush predators that use elongated, raptorial pedipalps for different activities. Although pedipalp use in predation and courtship has been explored in videography in vivo analyses, kinematic ex vivo examination of these appendages has not been conducted. Here, we rectify this lack of data by using micro-CT scans to 3D-kinematically model the appendage morphology and the range of motion (ROM) of the joints for Damon medius and Heterophrynus elaphus. We illustrate the successful application of this technique to terrestrial euarthropods in determining the maximum ROM values for each pedipalp joint. We also note that, in life, these values would be lower due to motion restricting structures like tendons, arthrodial membranes, and muscles. We further compare our maximum values obtained here with data from video-based motion analyses. The ROM of each joint shows the greatest flexibility in the femur-tibia joint (140-150°), the lowest in the basitarsus-claw joint (35-40°). ROM in the tibia-basitarsus joint is markedly distinct (D. medius: 44°; H. elaphus: 105°). This disparity reflects how H. elaphus uses the joint in the capture basket, while D. medius uses the femur-tibia joint to form the capture basket. We further illustrate notable vertical motion of the H. elaphus pedipalp compared to D. medius. This difference reflects the retro-ventral trochanter apophysis of H. elaphus. Our study opens the possibility to further whip spider kinematic understanding. Examination of other taxa using this approach will result in a more comprehensive understanding of the ecological significance and ethological implications of this unique arachnid group.
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Affiliation(s)
- Michel Schmidt
- Bavarian State Collection of Zoology, Bavarian Natural History Collections, Munich, Germany.,Department Biology II, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Roland R Melzer
- Bavarian State Collection of Zoology, Bavarian Natural History Collections, Munich, Germany.,Department Biology II, Ludwig-Maximilians-Universität München, Munich, Germany.,GeoBio-Center, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Russell D C Bicknell
- Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, Australia
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McLean C, Garwood R, Brassey C. Assessing the patterns and drivers of shape complexity in the amblypygid pedipalp. Ecol Evol 2021; 11:10709-10719. [PMID: 34367607 PMCID: PMC8328453 DOI: 10.1002/ece3.7882] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/25/2021] [Accepted: 06/03/2021] [Indexed: 11/09/2022] Open
Abstract
Amblypygi is an arachnid order possessing a unique pair of spined pedipalps: appendages that perform in prey capture, courtship, and contest. Pedipalp length, hypothesized to be under sexual selection, varies markedly across amblypygid species, and pedipalp spination, thought to reflect selection for function in prey capture, also differs interspecifically. Differences in pedipalp shape between species may indicate that the relative strength of selection for prey capture and sexual selection vary across the group. However, interspecific differences in pedipalp shape have not been quantified, due to difficulties in identifying homologous features. For the first time, we quantify trends in amblypygid pedipalp shape complexity. We use elliptical Fourier analysis to quantify 2D complexity in pedipalp outlines across eleven species and six genera. We find that complexity significantly decreases as pedipalp length increases. This appears to be driven by relative spine length, suggesting that a trade-off exists between pedipalp length and spination. Furthermore, significant female-biased sexual dimorphism in shape complexity is present in the tibial segment of the amblypygid pedipalp. Our results provide novel insights into the drivers of amblypygid pedipalp evolution and suggest that a functional trade-off between performance in prey capture and other functions under sexual selection exist in this enigmatic structure.
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Affiliation(s)
- Callum McLean
- Department of Natural SciencesManchester Metropolitan UniversityManchesterUK
| | - Russell Garwood
- School of Earth and Environmental SciencesUniversity of ManchesterManchesterUK
- Earth Sciences DepartmentNatural History MuseumLondonUK
| | - Charlotte Brassey
- Department of Natural SciencesManchester Metropolitan UniversityManchesterUK
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8
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McLean C, Garwood R, Brassey C. Sexual dimorphism in the size and shape of the raptorial pedipalps of Giant Whip Spiders (Arachnida: Amblypygi). J Zool (1987) 2019. [DOI: 10.1111/jzo.12726] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- C.J. McLean
- School of Science and The Environment Manchester Metropolitan University Manchester UK
| | - R.J. Garwood
- School of Earth and Environmental Sciences University of Manchester Manchester UK
- Earth Sciences Department Natural History Museum London UK
| | - C.A. Brassey
- School of Science and The Environment Manchester Metropolitan University Manchester UK
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9
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Rico-Guevara A, Hurme KJ. Intrasexually selected weapons. Biol Rev Camb Philos Soc 2019; 94:60-101. [PMID: 29924496 DOI: 10.1111/brv.12436] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 05/14/2018] [Accepted: 05/18/2018] [Indexed: 01/24/2023]
Abstract
We propose a practical concept that distinguishes the particular kind of weaponry that has evolved to be used in combat between individuals of the same species and sex, which we term intrasexually selected weapons (ISWs). We present a treatise of ISWs in nature, aiming to understand their distinction and evolution from other secondary sex traits, including from 'sexually selected weapons', and from sexually dimorphic and monomorphic weaponry. We focus on the subset of secondary sex traits that are the result of same-sex combat, defined here as ISWs, provide not previously reported evolutionary patterns, and offer hypotheses to answer questions such as: why have only some species evolved weapons to fight for the opposite sex or breeding resources? We examined traits that seem to have evolved as ISWs in the entire animal phylogeny, restricting the classification of ISW to traits that are only present or enlarged in adults of one of the sexes, and are used as weapons during intrasexual fights. Because of the absence of behavioural data and, in many cases, lack of sexually discriminated series from juveniles to adults, we exclude the fossil record from this review. We merge morphological, ontogenetic, and behavioural information, and for the first time thoroughly review the tree of life to identify separate evolution of ISWs. We found that ISWs are only found in bilateral animals, appearing independently in nematodes, various groups of arthropods, and vertebrates. Our review sets a reference point to explore other taxa that we identify with potential ISWs for which behavioural or morphological studies are warranted. We establish that most ISWs come in pairs, are located in or near the head, are endo- or exoskeletal modifications, are overdeveloped structures compared with those found in females, are modified feeding structures and/or locomotor appendages, are most common in terrestrial taxa, are frequently used to guard females, territories, or both, and are also used in signalling displays to deter rivals and/or attract females. We also found that most taxa lack ISWs, that females of only a few species possess better-developed weapons than males, that the cases of independent evolution of ISWs are not evenly distributed across the phylogeny, and that animals possessing the most developed ISWs have non-hunting habits (e.g. herbivores) or are faunivores that prey on very small prey relative to their body size (e.g. insectivores). Bringing together perspectives from studies on a variety of taxa, we conceptualize that there are five ways in which a sexually dimorphic trait, apart from the primary sex traits, can be fixed: sexual selection, fecundity selection, parental role division, differential niche occupation between the sexes, and interference competition. We discuss these trends and the factors involved in the evolution of intrasexually selected weaponry in nature.
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Affiliation(s)
- Alejandro Rico-Guevara
- Department of Integrative Biology, University of California, Berkeley, 3040 Valley Life Sciences Building, Berkeley, CA, 94720, U.S.A.,Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd, Unit 3043, Storrs, CT, 06269, U.S.A.,Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Código Postal 11001, Bogotá DC, Colombia
| | - Kristiina J Hurme
- Department of Integrative Biology, University of California, Berkeley, 3040 Valley Life Sciences Building, Berkeley, CA, 94720, U.S.A.,Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd, Unit 3043, Storrs, CT, 06269, U.S.A
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10
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McLean CJ, Garwood RJ, Brassey CA. Sexual dimorphism in the Arachnid orders. PeerJ 2018; 6:e5751. [PMID: 30416880 PMCID: PMC6225839 DOI: 10.7717/peerj.5751] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 09/14/2018] [Indexed: 01/21/2023] Open
Abstract
Sexual differences in size and shape are common across the animal kingdom. The study of sexual dimorphism (SD) can provide insight into the sexual- and natural-selection pressures experienced by males and females in different species. Arachnids are diverse, comprising over 100,000 species, and exhibit some of the more extreme forms of SD in the animal kingdom, with the males and females of some species differing dramatically in body shape and/or size. Despite this, research on arachnid SD has primarily focused on specific clades as opposed to observing traits across arachnid orders, the smallest of which have received comparatively little attention. This review provides an overview of the research to date on the trends and potential evolutionary drivers for SD and sexual size dimorphism (SSD) in individual arachnid orders, and across arachnids as a whole. The most common trends across Arachnida are female-biased SSD in total body size, male-biased SSD in relative leg length and SD in pedipalp length and shape. However, the evolution of sexually dimorphic traits within the group is difficult to elucidate due to uncertainty in arachnid phylogenetic relationships. Based on the dataset we have gathered here, we highlight gaps in our current understanding and suggest areas for future research.
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Affiliation(s)
- Callum J. McLean
- School of Science and the Environment, Manchester Metropolitan University, Manchester, UK
| | - Russell J. Garwood
- School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
- Earth Sciences Department, Natural History Museum, London, UK
| | - Charlotte A. Brassey
- School of Science and the Environment, Manchester Metropolitan University, Manchester, UK
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