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Ruebenstahl A, Ciurca SJ, Briggs DEG. A Giant Eurypterus from the Silurian (Pridoli) Bertie Group of North America. BULLETIN OF THE PEABODY MUSEUM OF NATURAL HISTORY 2021. [DOI: 10.3374/014.062.0101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Alexander Ruebenstahl
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06520-8109 USA
| | | | - Derek E. G. Briggs
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06520-8109; and Yale Peabody Museum of Natural History, Yale University, New Haven, CT 06520-8118 USA —
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2
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Dunlop JA. Evolution: A Breath of Fresh Air for Eurypterids. Curr Biol 2020; 30:R1304-R1306. [DOI: 10.1016/j.cub.2020.09.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Howard RJ, Puttick MN, Edgecombe GD, Lozano-Fernandez J. Arachnid monophyly: Morphological, palaeontological and molecular support for a single terrestrialization within Chelicerata. ARTHROPOD STRUCTURE & DEVELOPMENT 2020; 59:100997. [PMID: 33039753 DOI: 10.1016/j.asd.2020.100997] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/18/2020] [Accepted: 09/18/2020] [Indexed: 06/11/2023]
Abstract
The majority of extant arachnids are terrestrial, but other chelicerates are generally aquatic, including horseshoe crabs, sea spiders, and the extinct eurypterids. It is necessary to determine whether arachnids are exclusively descended from a single common ancestor (monophyly), because only that relationship is compatible with one land colonisation in chelicerate evolutionary history. Some studies have cast doubt on arachnid monophyly and recast the origins of their terrestrialization. These include some phylogenomic analyses placing horseshoe crabs within Arachnida, and from aquatic Palaeozoic stem-group scorpions. Here, we evaluate the possibility of arachnid monophyly by considering morphology, fossils and molecules holistically. We argue arachnid monophyly obviates the need to posit reacquisition/retention of aquatic characters such as gnathobasic feeding and book gills without trabeculae from terrestrial ancestors in horseshoe crabs, and that the scorpion total-group contains few aquatic taxa. We built a matrix composed of 200 slowly-evolving genes and re-analysed two published molecular datasets. We retrieved arachnid monophyly where other studies did not - highlighting the difficulty of resolving chelicerate relationships from current molecular data. As such, we consider arachnid monophyly the best-supported hypothesis. Finally, we inferred that arachnids terrestrialized during the Cambrian-Ordovician using the slow-evolving molecular matrix, in agreement with recent analyses.
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Affiliation(s)
- Richard J Howard
- Department of Biosciences, University of Exeter, Penryn Campus, UK; Department of Earth Sciences, The Natural History Museum, UK.
| | - Mark N Puttick
- School of Biochemistry & Biological Sciences, University of Bath, Bath, UK
| | | | - Jesus Lozano-Fernandez
- Institute of Evolutionary Biology (CSIC-UPF), Barcelona, Spain; School of Biological Sciences, University of Bristol, Bristol, UK.
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Lamsdell JC, McCoy VE, Perron-Feller OA, Hopkins MJ. Air Breathing in an Exceptionally Preserved 340-Million-Year-Old Sea Scorpion. Curr Biol 2020; 30:4316-4321.e2. [PMID: 32916114 DOI: 10.1016/j.cub.2020.08.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/24/2020] [Accepted: 08/07/2020] [Indexed: 11/26/2022]
Abstract
Arachnids are the second most successful terrestrial animal group after insects [1] and were one of the first arthropod clades to successfully invade land [2]. Fossil evidence for this transition is limited, with the majority of arachnid clades first appearing in the terrestrial fossil record. Furthermore, molecular clock dating has suggested a Cambrian-Ordovician terrestrialization event for arachnids [3], some 60 Ma before their first fossils in the Silurian, although these estimates assume that arachnids evolved from a fully aquatic ancestor. Eurypterids, the sister clade to terrestrial arachnids [4-6], are known to have undergone major macroecological shifts in transitioning from marine to freshwater environments during the Devonian [7, 8]. Discoveries of apparently subaerial eurypterid trackways [9, 10] have led to the suggestion that eurypterids were even able to venture on land and possibly breathe air [11]. However, modern horseshoe crabs undertake amphibious excursions onto land to reproduce [12], rendering trace fossil evidence alone inconclusive. Here, we present details of the respiratory organs of Adelophthalmus pyrrhae sp. nov. from the Carboniferous of Montagne Noire, France [13], revealed through micro computed tomography (μ-CT) imaging. Pillar-like trabeculae on the dorsal surface of each gill lamella indicate eurypterids were capable of subaerial breathing, suggesting that book gills are the direct precursors to book lungs while vascular ancillary respiratory structures known as Kiemenplatten represent novel air-breathing structures. The discovery of air-breathing structures in eurypterids indicates that characters permitting terrestrialization accrued in the arachnid stem lineage and suggests the Cambrian-Ordovician ancestor of arachnids would also have been semi-terrestrial.
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Affiliation(s)
- James C Lamsdell
- Department of Geology and Geography, West Virginia University, 98 Beechurst Avenue, Morgantown, WV 26506, USA.
| | - Victoria E McCoy
- Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Avenue, Milwaukee, WI 53211, USA
| | - Opal A Perron-Feller
- Department of Geology, Oberlin College, 52 W. Lorain Street, Oberlin, OH 44074, USA
| | - Melanie J Hopkins
- Division of Paleontology (Invertebrates), American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
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Noah KE, Hao J, Li L, Sun X, Foley B, Yang Q, Xia X. Major Revisions in Arthropod Phylogeny Through Improved Supermatrix, With Support for Two Possible Waves of Land Invasion by Chelicerates. Evol Bioinform Online 2020; 16:1176934320903735. [PMID: 32076367 PMCID: PMC7003163 DOI: 10.1177/1176934320903735] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 01/02/2020] [Indexed: 01/04/2023] Open
Abstract
Deep phylogeny involving arthropod lineages is difficult to recover because the erosion of phylogenetic signals over time leads to unreliable multiple sequence alignment (MSA) and subsequent phylogenetic reconstruction. One way to alleviate the problem is to assemble a large number of gene sequences to compensate for the weakness in each individual gene. Such an approach has led to many robustly supported but contradictory phylogenies. A close examination shows that the supermatrix approach often suffers from two shortcomings. The first is that MSA is rarely checked for reliability and, as will be illustrated, can be poor. The second is that, to alleviate the problem of homoplasy at the third codon position of protein-coding genes due to convergent evolution of nucleotide frequencies, phylogeneticists may remove or degenerate the third codon position but may do it improperly and introduce new biases. We performed extensive reanalysis of one of such "big data" sets to highlight these two problems, and demonstrated the power and benefits of correcting or alleviating these problems. Our results support a new group with Xiphosura and Arachnopulmonata (Tetrapulmonata + Scorpiones) as sister taxa. This favors a new hypothesis in which the ancestor of Xiphosura and the extinct Eurypterida (sea scorpions, of which many later forms lived in brackish or freshwater) returned to the sea after the initial chelicerate invasion of land. Our phylogeny is supported even with the original data but processed with a new "principled" codon degeneration. We also show that removing the 1673 codon sites with both AGN and UCN codons (encoding serine) in our alignment can partially reconcile discrepancies between nucleotide-based and AA-based tree, partly because two sequences, one with AGN and the other with UCN, would be identical at the amino acid level but quite different at the nucleotide level.
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Affiliation(s)
| | - Jiasheng Hao
- College of Life Sciences, Anhui Normal University, Wuhu, China
| | - Luyan Li
- Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, China
| | - Xiaoyan Sun
- Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, China
| | - Brian Foley
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Qun Yang
- Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, China
| | - Xuhua Xia
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON, Canada
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Schoenemann B, Poschmann M, Clarkson ENK. Insights into the 400 million-year-old eyes of giant sea scorpions (Eurypterida) suggest the structure of Palaeozoic compound eyes. Sci Rep 2019; 9:17797. [PMID: 31780700 PMCID: PMC6882788 DOI: 10.1038/s41598-019-53590-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 10/30/2019] [Indexed: 11/09/2022] Open
Abstract
Sea scorpions (Eurypterida, Chelicerata) of the Lower Devonian (~400 Mya) lived as large, aquatic predators. The structure of modern chelicerate eyes is very different from that of mandibulate compound eyes [Mandibulata: Crustacea and Tracheata (Hexapoda, such as insects, and Myriapoda)]. Here we show that the visual system of Lower Devonian (~400 Mya) eurypterids closely matches that of xiphosurans (Xiphosura, Chelicerata). Modern representatives of this group, the horseshoe crabs (Limulidae), have cuticular lens cylinders and usually also an eccentric cell in their sensory apparatus. This strongly suggests that the xiphosuran/eurypterid compound eye is a plesiomorphic structure with respect to the Chelicerata, and probably ancestral to that of Euchelicerata, including Eurypterida, Arachnida and Xiphosura. This is supported by the fact that some Palaeozoic scorpions also possessed compound eyes similar to those of eurypterids. Accordingly, edge enhancement (lateral inhibition), organised by the eccentric cell, most useful in scattered light-conditions, may be a very old mechanism, while the single-lens system of arachnids is possibly an adaptation to a terrestrial life-style.
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Affiliation(s)
- Brigitte Schoenemann
- University of Cologne, Zoology Department/ Neurobiology/Animal Physiology/Institute of Biology Education, Herbert-Lewin-Straße 10, D-50931, Cologne, Germany.
| | - Markus Poschmann
- Generaldirektion Kulturelles Erbe RLP, Direktion Landesarchäologie/Erdgeschichte, Niederberger Höhe 1, D-56077, Koblenz, Germany
| | - Euan N K Clarkson
- University of Edinburgh, Grant Institute, School of Geosciences, West Mains Road, Edinburgh, EH9 3JW, Scotland
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Dunlop JA, Lamsdell JC. Segmentation and tagmosis in Chelicerata. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:395-418. [PMID: 27240897 DOI: 10.1016/j.asd.2016.05.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/17/2016] [Accepted: 05/18/2016] [Indexed: 05/16/2023]
Abstract
Patterns of segmentation and tagmosis are reviewed for Chelicerata. Depending on the outgroup, chelicerate origins are either among taxa with an anterior tagma of six somites, or taxa in which the appendages of somite I became increasingly raptorial. All Chelicerata have appendage I as a chelate or clasp-knife chelicera. The basic trend has obviously been to consolidate food-gathering and walking limbs as a prosoma and respiratory appendages on the opisthosoma. However, the boundary of the prosoma is debatable in that some taxa have functionally incorporated somite VII and/or its appendages into the prosoma. Euchelicerata can be defined on having plate-like opisthosomal appendages, further modified within Arachnida. Total somite counts for Chelicerata range from a maximum of nineteen in groups like Scorpiones and the extinct Eurypterida down to seven in modern Pycnogonida. Mites may also show reduced somite counts, but reconstructing segmentation in these animals remains challenging. Several innovations relating to tagmosis or the appendages borne on particular somites are summarised here as putative apomorphies of individual higher taxa. We also present our observations within the concept of pseudotagma, whereby the true tagmata - the prosoma and opisthosoma - can be defined on a fundamental change in the limb series while pseudotagmata, such as the cephalosoma/proterosoma, are expressed as divisions in sclerites covering the body without an accompanying change in the appendages.
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Affiliation(s)
- Jason A Dunlop
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, D-10115 Berlin, Germany.
| | - James C Lamsdell
- American Museum of Natural History, Division of Paleontology, Central Park West at 79th St, New York, NY 10024, USA.
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Daley AC, Drage HB. The fossil record of ecdysis, and trends in the moulting behaviour of trilobites. ARTHROPOD STRUCTURE & DEVELOPMENT 2016; 45:71-96. [PMID: 26431634 DOI: 10.1016/j.asd.2015.09.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 09/01/2015] [Accepted: 09/14/2015] [Indexed: 06/05/2023]
Abstract
Ecdysis, the process of moulting an exoskeleton, is one of the key characters uniting arthropods, nematodes and a number of smaller phyla into Ecdysozoa. The arthropod fossil record, particularly trilobites, eurypterids and decapod crustaceans, yields information on moulting, although the current focus is predominantly descriptive and lacks a broader evolutionary perspective. We here review literature on the fossil record of ecdysis, synthesising research on the behaviour, evolutionary trends, and phylogenetic significance of moulting throughout the Phanerozoic. Approaches vary widely between taxonomic groups, but an overall theme uniting these works suggests that identifying moults in the palaeontological record must take into account the morphology, taphonomy and depositional environment of fossils. We also quantitatively analyse trends in trilobite ecdysis based on a newly generated database of published incidences of moulting behaviour. This preliminary work reveals significant taxonomic and temporal signal in the trilobite moulting fossil record, with free cheek moulting being prevalent across all Orders and throughout the Phanerozoic, and peaks of cephalic moulting in Phacopida during the Ordovician and rostral plate moulting in Redlichiida during the Cambrian. This study and a review of the literature suggest that it is feasible to extract large-scale evolutionary information from the fossil record of moulting.
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Affiliation(s)
- Allison C Daley
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, United Kingdom; Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PZ, United Kingdom.
| | - Harriet B Drage
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, United Kingdom; Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PZ, United Kingdom
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Garwood RJ, Dunlop J. Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders. PeerJ 2014; 2:e641. [PMID: 25405073 PMCID: PMC4232842 DOI: 10.7717/peerj.641] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/08/2014] [Indexed: 12/12/2022] Open
Abstract
Arachnids are an important group of arthropods. They are: diverse and abundant; a major constituent of many terrestrial ecosystems; and possess a deep and extensive fossil record. In recent years a number of exceptionally preserved arachnid fossils have been investigated using tomography and associated techniques, providing valuable insights into their morphology. Here we use X-ray microtomography to reconstruct members of two extinct arachnid orders. In the Haptopoda, we demonstrate the presence of 'clasp-knife' chelicerae, and our novel redescription of a member of the Phalangiotarbida highlights leg details, but fails to resolve chelicerae in the group due to their small size. As a result of these reconstructions, tomographic studies of three-dimensionally preserved fossils now exist for three of the four extinct orders, and for fossil representatives of several extant ones. Such studies constitute a valuable source of high fidelity data for constructing phylogenies. To illustrate this, here we present a cladistic analysis of the chelicerates to accompany these reconstructions. This is based on a previously published matrix, expanded to include fossil taxa and relevant characters, and allows us to: cladistically place the extinct arachnid orders; explicitly test some earlier hypotheses from the literature; and demonstrate that the addition of fossils to phylogenetic analyses can have broad implications. Phylogenies based on chelicerate morphology-in contrast to molecular studies-have achieved elements of consensus in recent years. Our work suggests that these results are not robust to the addition of novel characters or fossil taxa. Hypotheses surrounding chelicerate phylogeny remain in a state of flux.
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Affiliation(s)
- Russell J. Garwood
- School of Earth, Atmospheric and Environmental Sciences and The Manchester X-ray Imaging Facility, School of Materials, The University of Manchester, Manchester, UK
| | - Jason Dunlop
- Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University Berlin, Berlin, Germany
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12
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Haug JT, Caron JB, Haug C. Demecology in the Cambrian: synchronized molting in arthropods from the Burgess Shale. BMC Biol 2013; 11:64. [PMID: 23721223 PMCID: PMC3685569 DOI: 10.1186/1741-7007-11-64] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/10/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Burgess Shale is well known for its preservation of a diverse soft-bodied biota dating from the Cambrian period (Series 3, Stage 5). While previous paleoecological studies have focused on particular species (autecology) or entire paleocommunities (synecology), studies on the ecology of populations (demecology) of Burgess Shale organisms have remained mainly anecdotal. RESULTS Here, we present evidence for mass molting events in two unrelated arthropods from the Burgess Shale Walcott Quarry, Canadaspis perfecta and a megacheiran referred to as Alalcomenaeus sp. CONCLUSIONS These findings suggest that the triggers for such supposed synchronized molting appeared early on during the Cambrian radiation, and synchronized molting in the Cambrian may have had similar functions in the past as it does today. In addition, the finding of numerous juvenile Alalcomenaeus sp. molts associated with the putative alga Dictyophycus suggests a possible nursery habitat. In this nursery habitat a population of this animal might have found a more protected environment in which to spend critical developmental phases, as do many modern species today.
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Affiliation(s)
- Joachim T Haug
- Zoological Institute and Museum, Department of Cytology and Evolutionary Biology, Soldmannstrasse 23, 17487 Greifswald, Germany.
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Lamsdell JC. Revised systematics of Palaeozoic ‘horseshoe crabs’ and the myth of monophyletic Xiphosura. Zool J Linn Soc 2012. [DOI: 10.1111/j.1096-3642.2012.00874.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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