1
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Brownstein CD. Palaeospondylus and the early evolution of gnathostomes. Nature 2023; 620:E20-E22. [PMID: 37612401 DOI: 10.1038/s41586-023-06434-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/14/2023] [Indexed: 08/25/2023]
Affiliation(s)
- Chase Doran Brownstein
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.
- Stamford Museum and Nature Center, Stamford, CT, USA.
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2
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Eboreime J, Choi SK, Yoon SR, Sadybekov A, Katritch V, Calabrese P, Arnheim N. Germline selection of PTPN11 (HGNC:9644) variants make a major contribution to both Noonan syndrome's high birth rate and the transmission of sporadic cancer variants resulting in fetal abnormality. Hum Mutat 2022; 43:2205-2221. [PMID: 36349709 PMCID: PMC10099774 DOI: 10.1002/humu.24493] [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: 04/04/2022] [Revised: 09/20/2022] [Accepted: 10/12/2022] [Indexed: 11/10/2022]
Abstract
Some spontaneous germline gain-of-function mutations promote spermatogonial stem cell clonal expansion and disproportionate variant sperm production leading to unexpectedly high transmission rates for some human genetic conditions. To measure the frequency and spatial distribution of de novo mutations we divided three testes into 192 pieces each and used error-corrected deep-sequencing on each piece. We focused on PTPN11 (HGNC:9644) Exon 3 that contains 30 different PTPN11 Noonan syndrome (NS) mutation sites. We found 14 of these variants formed clusters among the testes; one testis had 11 different variant clusters. The mutation frequencies of these different clusters were not correlated with their case-recurrence rates nor were case recurrence rates of PTPN11 variants correlated with their tyrosine phosphatase levels thereby confusing PTPN11's role in germline clonal expansion. Six of the PTPN11 exon 3 de novo variants associated with somatic mutation-induced sporadic cancers (but not NS) also formed testis clusters. Further, three of these six variants were observed among fetuses that underwent prenatal ultrasound screening for NS-like features. Mathematical modeling showed that germline selection can explain both the mutation clusters and the high incidence of NS (1/1000-1/2500).
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Affiliation(s)
- Jordan Eboreime
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Soo-Kyung Choi
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Song-Ro Yoon
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
| | - Anastasiia Sadybekov
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, California, USA
| | - Vsevolod Katritch
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, California, USA
| | - Peter Calabrese
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, California, USA
| | - Norman Arnheim
- Department of Biological Sciences, Molecular and Computational Biology Program, University of Southern California, Los Angeles, California, USA
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3
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Abstract
Innovations relating to the consumption of hard prey are implicated in ecological shifts in marine ecosystems as early as the mid-Paleozoic. Lungfishes represent the first and longest-ranging lineage of durophagous vertebrates, but how and when the various feeding specializations of this group arose remain unclear. Two exceptionally preserved fossils of the Early Devonian lobe-finned fish Youngolepis reveal the origin of the specialized lungfish feeding mechanism. Youngolepis has a radically restructured palate, reorienting jaw muscles for optimal force transition, coupled with radiating entopterygoid tooth rows like those of lungfish toothplates. This triturating surface occurs in conjunction with marginal dentition and blunt coronoid fangs, suggesting a role in crushing rather than piercing prey. Bayesian tip-dating analyses incorporating these morphological data indicate that the complete suite of lungfish feeding specializations may have arisen in as little as 7 million years, representing one of the most striking episodes of innovation during the initial evolutionary radiations of bony fishes. It is unclear how Lungfishes evolved durophagy, the consumption of hard prey, despite being the longest lineage of vertebrates with this feeding mechanism. Here, the authors describe exceptionally preserved fossils of Youngolepis from the Early Devonian, showing early adaptations to durophagy.
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4
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Mondéjar‐Fernández J, Meunier FJ, Cloutier R, Clément G, Laurin M. A microanatomical and histological study of the scales of the Devonian sarcopterygian Miguashaia bureaui and the evolution of the squamation in coelacanths. J Anat 2021; 239:451-478. [PMID: 33748974 PMCID: PMC8273612 DOI: 10.1111/joa.13428] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 02/26/2021] [Accepted: 02/26/2021] [Indexed: 01/31/2023] Open
Abstract
Coelacanths have traditionally been described as morphologically conservative throughout their long evolutionary history, which spans more than 400 million years. After an initial burst during the Devonian, a morphological stasis was long thought to have prevailed since the Carboniferous, as shown by the extant Latimeria. New fossil discoveries have challenged this view, with punctual and sometimes unusual departures from the general coelacanth Bauplan. The dermal skeleton is considered to represent one, if not the main, example of morphological stasis in coelacanth evolution and as a consequence, has remained poorly surveyed. The lack of palaeohistological data on the dermoskeleton has resulted in a poor understanding of the early establishment and evolution of the coelacanth squamation. Here we describe the scales of Miguashaia bureaui from the Upper Devonian of Miguasha, Québec (Canada), revealing histological data for a Palaeozoic coelacanth in great detail and adding to our knowledge on the dermal skeleton of sarcopterygians. Miguashaia displays rounded scales ornamented by tubercules and narrow ridges made of dentine and capped with enamel. At least two generations of superimposed odontodes occur, which is reminiscent of the primitive condition of stem osteichthyans like Andreolepis or Lophosteus, and onychodonts like Selenodus. The middle vascular layer is well developed and shows traces of osteonal remodelling. The basal plate consists of a fully mineralised lamellar bone with a repetitive rotation pattern every five layers indicating a twisted plywood-like arrangement of the collagen plies. Comparisons with the extant Latimeria and other extinct taxa show that these features are consistently conserved across coelacanth evolution with only minute changes in certain taxa. The morphological and histological features displayed in the scales of Miguashaia enable us to draw a comprehensive picture of the onset of the coelacanth squamation and to propose and discuss evolutionary scenarios for the coelacanth dermoskeleton.
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Affiliation(s)
- Jorge Mondéjar‐Fernández
- Département Origines & ÉvolutionUMR 7207 (MNHN–Sorbonne Université–CNRS), CR2P, Centre de Recherche en Paléontologie—ParisMuséum national d’Histoire naturelleParisFrance
- Senckenberg Forschungsinstitut und Naturmuseum FrankfurtFrankfurt am MainGermany
| | - François J. Meunier
- Département Adaptations du VivantFRE BOREA 2030, (MNHN–Sorbonne Université–Univ. Caen Normandie–Univ. Antilles–CNRS–IRD)Muséum national d'Histoire naturelleParisFrance
| | | | - Gaël Clément
- Département Origines & ÉvolutionUMR 7207 (MNHN–Sorbonne Université–CNRS), CR2P, Centre de Recherche en Paléontologie—ParisMuséum national d’Histoire naturelleParisFrance
| | - Michel Laurin
- Département Origines & ÉvolutionUMR 7207 (MNHN–Sorbonne Université–CNRS), CR2P, Centre de Recherche en Paléontologie—ParisMuséum national d’Histoire naturelleParisFrance
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5
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Marjanović D. The Making of Calibration Sausage Exemplified by Recalibrating the Transcriptomic Timetree of Jawed Vertebrates. Front Genet 2021; 12:521693. [PMID: 34054911 PMCID: PMC8149952 DOI: 10.3389/fgene.2021.521693] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 03/22/2021] [Indexed: 01/20/2023] Open
Abstract
Molecular divergence dating has the potential to overcome the incompleteness of the fossil record in inferring when cladogenetic events (splits, divergences) happened, but needs to be calibrated by the fossil record. Ideally but unrealistically, this would require practitioners to be specialists in molecular evolution, in the phylogeny and the fossil record of all sampled taxa, and in the chronostratigraphy of the sites the fossils were found in. Paleontologists have therefore tried to help by publishing compendia of recommended calibrations, and molecular biologists unfamiliar with the fossil record have made heavy use of such works (in addition to using scattered primary sources and copying from each other). Using a recent example of a large node-dated timetree inferred from molecular data, I reevaluate all 30 calibrations in detail, present the current state of knowledge on them with its various uncertainties, rerun the dating analysis, and conclude that calibration dates cannot be taken from published compendia or other secondary or tertiary sources without risking strong distortions to the results, because all such sources become outdated faster than they are published: 50 of the (primary) sources I cite to constrain calibrations were published in 2019, half of the total of 280 after mid-2016, and 90% after mid-2005. It follows that the present work cannot serve as such a compendium either; in the slightly longer term, it can only highlight known and overlooked problems. Future authors will need to solve each of these problems anew through a thorough search of the primary paleobiological and chronostratigraphic literature on each calibration date every time they infer a new timetree, and that literature is not optimized for that task, but largely has other objectives.
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Affiliation(s)
- David Marjanović
- Department of Evolutionary Morphology, Science Programme “Evolution and Geoprocesses”, Museum für Naturkunde – Leibniz Institute for Evolutionary and Biodiversity Research, Berlin, Germany
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6
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Endocast and Bony Labyrinth of a Devonian "Placoderm" Challenges Stem Gnathostome Phylogeny. Curr Biol 2021; 31:1112-1118.e4. [PMID: 33508218 DOI: 10.1016/j.cub.2020.12.046] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/24/2020] [Accepted: 12/23/2020] [Indexed: 11/20/2022]
Abstract
Our understanding of the earliest evolution of jawed vertebrates depends on a credible phylogenetic framework for the jawed stem gnathostomes collectively known as "placoderms".1 However, their relationships, and whether placoderms represent a single radiation or a paraphyletic array, remain contentious.2-13 This uncertainty is compounded by an uneven understanding of anatomy across the group, particularly of the phylogenetically informative braincase and brain cavity-endocast. Based on new tomographic data, we here describe the endocast and bony labyrinth of Brindabellaspis stensioi from the Early Devonian of New South Wales.14 The taxon was commonly recovered as branching near the base of placoderms.5-9,11,12,15-17 Previous studies of Brindabellaspis emphasized its resemblances with fossil jawless fishes in the braincase anatomy14 and endocast proportions1,18 and its distinctive features were interpreted as autapomorphies, such as the elongated premedian region.19 Although our three-dimensional data confirmed the resemblance of its endocast to those of jawless vertebrates, we discovered that the inner ear and endolymphatic complex display a repertoire of previously unrecognized characters close to modern or crown-group jawed vertebrates, including a pronounced sinus superior and a vertical duct that connects the endolymphatic sac and the labyrinth cavity. Both parsimony and Bayesian analyses suggest that prevailing hypotheses of placoderm relationships are unstable, with newly revealed anatomy pointing to a radical revision of early gnathostome evolution. Our results call into question the appropriateness of arthrodire-like placoderms as models of primitive gnathostome anatomy and raise questions of homology relating to key cranial features.
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Kawasaki K, Keating JN, Nakatomi M, Welten M, Mikami M, Sasagawa I, Puttick MN, Donoghue PC, Ishiyama M. Coevolution of enamel, ganoin, enameloid, and their matrix SCPP genes in osteichthyans. iScience 2021; 24:102023. [PMID: 33506188 PMCID: PMC7814152 DOI: 10.1016/j.isci.2020.102023] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 11/14/2020] [Accepted: 12/29/2020] [Indexed: 12/19/2022] Open
Abstract
We resolve debate over the evolution of vertebrate hypermineralized tissues through analyses of matrix protein-encoding secretory calcium-binding phosphoprotein (SCPP) genes and phylogenetic inference of hypermineralized tissues. Among these genes, AMBN and ENAM are found in both sarcopterygians and actinopterygians, whereas AMEL and SCPP5 are found only in sarcopterygians and actinopterygians, respectively. Actinopterygian AMBN, ENAM, and SCPP5 are expressed during the formation of hypermineralized tissues on scales and teeth: ganoin, acrodin, and collar enamel in gar, and acrodin and collar enameloid in zebrafish. Our phylogenetic analyses indicate the emergence of an ancestral enamel in stem-osteichthyans, whereas ganoin emerged in stem-actinopterygians and true enamel in stem-sarcopterygians. Thus, AMBN and ENAM originated in concert with ancestral enamel, SCPP5 evolved in association with ganoin, and AMEL evolved with true enamel. Shifts in gene expression domain and timing explain the evolution of different hypermineralized tissues. We propose that hypermineralized tissues in osteichthyans coevolved with matrix SCPP genes. Ganoin emerged in actinopterygians; true enamel arose in sarcopterygians Dental enamel, acrodin, and enameloid in actinopterygians are related to ganoin SCPP5 evolved in association with ganoin, whereas AMEL evolved with true enamel Shifts in SCPP gene expression explain the evolution of hypermineralized tissues
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Affiliation(s)
- Kazuhiko Kawasaki
- Department of Anthropology, Pennsylvania State University, University Park, PA 16802, USA
- Corresponding author
| | - Joseph N. Keating
- School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Mitsushiro Nakatomi
- Division of Anatomy, Kyushu Dental University, Kitakyushu, Fukuoka 803-8580, Japan
| | - Monique Welten
- School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Masato Mikami
- Department of Microbiology, School of Life Dentistry at Niigata, the Nippon Dental University, Niigata, Niigata 951-8580, Japan
| | - Ichiro Sasagawa
- Advanced Research Center, School of Life Dentistry at Niigata, the Nippon Dental University, Niigata, Niigata 951-8580, Japan
| | - Mark N. Puttick
- School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK
- Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | | | - Mikio Ishiyama
- Department of Histology, School of Life Dentistry at Niigata, the Nippon Dental University, Niigata, Niigata 951-8580, Japan
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8
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King B, Rücklin M. A Bayesian approach to dynamic homology of morphological characters and the ancestral phenotype of jawed vertebrates. eLife 2020; 9:e62374. [PMID: 33274719 PMCID: PMC7793628 DOI: 10.7554/elife.62374] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 12/03/2020] [Indexed: 12/22/2022] Open
Abstract
Phylogenetic analysis of morphological data proceeds from a fixed set of primary homology statements, the character-by-taxon matrix. However, there are cases where multiple conflicting homology statements can be justified from comparative anatomy. The upper jaw bones of placoderms have traditionally been considered homologous to the palatal vomer-dermopalatine series of osteichthyans. The discovery of 'maxillate' placoderms led to the alternative hypothesis that 'core' placoderm jaw bones are premaxillae and maxillae lacking external (facial) laminae. We introduce a BEAST2 package for simultaneous inference of homology and phylogeny, and find strong evidence for the latter hypothesis. Phenetic analysis of reconstructed ancestors suggests that maxillate placoderms are the most plesiomorphic known gnathostomes, and the shared cranial architecture of arthrodire placoderms, maxillate placoderms and osteichthyans is inherited. We suggest that the gnathostome ancestor possessed maxillae and premaxillae with facial and palatal laminae, and that these bones underwent divergent evolutionary trajectories in placoderms and osteichthyans.
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9
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Teng CS, Cavin L, Maxson RE, Sánchez-Villagra MR, Crump JG. Resolving homology in the face of shifting germ layer origins: Lessons from a major skull vault boundary. eLife 2019; 8:e52814. [PMID: 31869306 PMCID: PMC6927740 DOI: 10.7554/elife.52814] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 12/13/2019] [Indexed: 12/13/2022] Open
Abstract
The vertebrate skull varies widely in shape, accommodating diverse strategies of feeding and predation. The braincase is composed of several flat bones that meet at flexible joints called sutures. Nearly all vertebrates have a prominent 'coronal' suture that separates the front and back of the skull. This suture can develop entirely within mesoderm-derived tissue, neural crest-derived tissue, or at the boundary of the two. Recent paleontological findings and genetic insights in non-mammalian model organisms serve to revise fundamental knowledge on the development and evolution of this suture. Growing evidence supports a decoupling of the germ layer origins of the mesenchyme that forms the calvarial bones from inductive signaling that establishes discrete bone centers. Changes in these relationships facilitate skull evolution and may create susceptibility to disease. These concepts provide a general framework for approaching issues of homology in cases where germ layer origins have shifted during evolution.
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Affiliation(s)
- Camilla S Teng
- Department of Stem Cell Biology and Regenerative MedicineUniversity of Southern CaliforniaLos AngelesUnited States
- Department of Biochemistry, Keck School of MedicineUniversity of Southern CaliforniaLos AngelesUnited States
| | - Lionel Cavin
- Department of Earth SciencesNatural History Museum of GenevaGenevaSwitzerland
| | - Robert E Maxson
- Department of Biochemistry, Keck School of MedicineUniversity of Southern CaliforniaLos AngelesUnited States
| | | | - J Gage Crump
- Department of Stem Cell Biology and Regenerative MedicineUniversity of Southern CaliforniaLos AngelesUnited States
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10
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Doeland M, Couzens AMC, Donoghue PCJ, Rücklin M. Tooth replacement in early sarcopterygians. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191173. [PMID: 31827852 PMCID: PMC6894600 DOI: 10.1098/rsos.191173] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
Teeth were an important innovation in vertebrate evolution but basic aspects of early dental evolution remain poorly understood. Teeth differ from other odontode organs, like scales, in their organized, sequential pattern of replacement. However, tooth replacement patterns also vary between the major groups of jawed vertebrates. Although tooth replacement in stem-osteichthyans and extant species has been intensively studied it has been difficult to resolve scenarios for the evolution of osteichthyan tooth replacement because of a dearth of evidence from living and fossil sarcopterygian fishes. Here we provide new anatomical data informing patterns of tooth replacement in the Devonian sarcopterygian fishes Onychodus, Eusthenopteron and Tiktaalik and the living coelacanth Latimeria based on microfocus- and synchrotron radiation-based X-ray microtomography. Early sarcopterygians generated replacement teeth on the jaw surface in a pattern similar to stem-osteichthyans, with damaged teeth resorbed and replacement teeth developed on the surface of the bone. However, resorption grades and development of replacement teeth vary spatially and temporally within the jaw. Particularly in Onychodus, where teeth were also shed through anterior rotation and resorption of bone at the base of the parasymphyseal tooth whorl, with new teeth added posteriorly. As tooth whorls are also present in more stem-osteichthyans, and statodont tooth whorls are present among acanthodians (putative stem-chondrichthyans), rotational replacement of the anterior dentition may be a stem-osteichthyan character. Our results suggest a more complex evolutionary history of tooth replacement.
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Affiliation(s)
- Mark Doeland
- Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
- Institute of Biology, Universiteit Leiden, Silviusweg 72, 2333 BE Leiden, The Netherlands
| | - Aidan M. C. Couzens
- Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
| | - Philip C. J. Donoghue
- School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Martin Rücklin
- Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
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11
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King B. Which morphological characters are influential in a Bayesian phylogenetic analysis? Examples from the earliest osteichthyans. Biol Lett 2019; 15:20190288. [PMID: 31311486 PMCID: PMC6684994 DOI: 10.1098/rsbl.2019.0288] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 06/19/2019] [Indexed: 12/12/2022] Open
Abstract
There has been much recent debate about which method is best for reconstructing the tree of life from morphological datasets. However, little attention has been paid to which characters, if any, are responsible for topological differences between trees recovered from competing methods on empirical datasets. Indeed, a simple procedure for finding characters supporting conflicting tree topologies is available in a parsimony framework, but an equivalent procedure in a model-based framework is lacking. Here, I introduce such a procedure and apply it to the problem of the 'psarolepid' osteichthyans. The 'psarolepids', which include the earliest known osteichthyans, are weakly supported as stem osteichthyans under parsimony but strongly supported as sarcopterygians in Bayesian analysis. The Bayesian result is driven by just two characters, both of which relate to the intracranial joint of sarcopterygians. Important characters that support a stem osteichthyan affinity for 'psarolepids', such as the absence of tooth enamel, have virtually no effect in a Bayesian framework. This is because of a bias towards characters with relatively complete sampling, a bias that has previously been reported for molecular data. This has important implications for Bayesian analysis of morphological datasets in general, as characters from different body parts commonly have different levels of coding completeness. Methods to critically appraise character support for conflicting phylogenetic hypotheses, such as that used here, should form an important part of phylogenetic analyses.
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Affiliation(s)
- Benedict King
- Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
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12
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Scale morphology and squamation pattern of Guiyu oneiros provide new insights into early osteichthyan body plan. Sci Rep 2019; 9:4411. [PMID: 30867533 PMCID: PMC6416254 DOI: 10.1038/s41598-019-40845-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 01/07/2019] [Indexed: 11/15/2022] Open
Abstract
Scale morphology and squamation play an important role in the study of fish phylogeny and classification. However, as the scales of the earliest osteichthyans or bony fishes are usually found in a disarticulated state, research into squamation patterns and phylogeny has been limited. Here we quantitatively describe the scale morphology of the oldest articulated osteichthyan, the 425-million-year-old Guiyu oneiros, based on geometric morphometrics and high-resolution computed tomography. Based on the cluster analysis of the scales in the articulated specimens, we present a squamation pattern of Guiyu oneiros, which divides the body scales into 4 main belts, comprising 16 areas. The new pattern reveals that the squamation of early osteichthyans is more complicated than previously known, and demonstrates that the taxa near the crown osteichthyan node in late Silurian had a greater degree of squamation zonation compared to more advanced forms. This study offers an important reference for the classification of detached scales of early osteichthyans, provides new insights into the early evolution of osteichthyan scales, and adds to our understanding of the early osteichthyan body plan.
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13
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Sallan L, Friedman M, Sansom RS, Bird CM, Sansom IJ. The nearshore cradle of early vertebrate diversification. Science 2018; 362:460-464. [DOI: 10.1126/science.aar3689] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 10/02/2018] [Indexed: 11/02/2022]
Abstract
Ancestral vertebrate habitats are subject to controversy and obscured by limited, often contradictory paleontological data. We assembled fossil vertebrate occurrence and habitat datasets spanning the middle Paleozoic (480 million to 360 million years ago) and found that early vertebrate clades, both jawed and jawless, originated in restricted, shallow intertidal-subtidal environments. Nearshore divergences gave rise to body plans with different dispersal abilities: Robust fishes shifted shoreward, whereas gracile groups moved seaward. Fresh waters were invaded repeatedly, but movement to deeper waters was contingent upon form and short-lived until the later Devonian. Our results contrast with the onshore-offshore trends, reef-centered diversification, and mid-shelf clustering observed for benthic invertebrates. Nearshore origins for vertebrates may be linked to the demands of their mobility and may have influenced the structure of their early fossil record and diversification.
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14
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Henderson SAC, Challands TJ. The cranial endocast of the Upper Devonian dipnoan ' Chirodipterus' australis. PeerJ 2018; 6:e5148. [PMID: 30002977 PMCID: PMC6037139 DOI: 10.7717/peerj.5148] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 06/12/2018] [Indexed: 11/20/2022] Open
Abstract
One of the first endocasts of a dipnoan (lungfish) to be realised was that of the Upper Devonian taxon Chirodipterus australis. This early interpretation was based on observations of the shape of the cranial cavity alone and was not based on a natural cast or ‘steinkern’ nor from serial sectioning. The validity of this reconstruction is therefore questionable and continued reference to and use of this interpretation in analyses of sarcopterygian cranial evolution runs the risk of propagation of error. Here we present a new detailed anatomical description of the endocast of ‘Chirodipterus’ australis from the Upper Devonian Gogo Formation of Western Australia, known for exceptional 3D preservation which enables fine-scale scrutiny of endocranial anatomy. We show that it exhibits a suite of characters more typical of Lower and Middle Devonian dipnoan taxa. Notably, the small utricular recess is unexpected for a taxon of this age, whereas the ventral expansion of the telencephalon is more typical of more derived taxa. The presence of such ’primitive’ characters in ‘C.’ australis supports its relatively basal position as demonstrated in the most recent phylogenies of Devonian Dipnoi.
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Affiliation(s)
| | - Tom J Challands
- School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom
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15
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Clement AM, King B, Giles S, Choo B, Ahlberg PE, Young GC, Long JA. Neurocranial anatomy of an enigmatic Early Devonian fish sheds light on early osteichthyan evolution. eLife 2018; 7:e34349. [PMID: 29807569 PMCID: PMC5973833 DOI: 10.7554/elife.34349] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 04/27/2018] [Indexed: 11/13/2022] Open
Abstract
The skull of 'Ligulalepis' from the Early Devonian of Australia (AM-F101607) has significantly expanded our knowledge of early osteichthyan anatomy, but its phylogenetic position has remained uncertain. We herein describe a second skull of 'Ligulalepis' and present micro-CT data on both specimens to reveal novel anatomical features, including cranial endocasts. Several features previously considered to link 'Ligulalepis' with actinopterygians are now considered generalized osteichthyan characters or of uncertain polarity. The presence of a lateral cranial canal is shown to be variable in its development between specimens. Other notable new features include the presence of a pineal foramen, the some detail of skull roof sutures, the shape of the nasal capsules, a placoderm-like hypophysial vein, and a chondrichthyan-like labyrinth system. New phylogenetic analyses place 'Ligulalepis' as a stem osteichthyan, specifically as the sister taxon to 'psarolepids' plus crown osteichthyans. The precise position of 'psarolepids' differs between parsimony and Bayesian analyses.
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Affiliation(s)
- Alice M Clement
- College of Science and EngineeringFlinders UniversityAdelaideAustralia
- Department of Organismal BiologyEvolutionary Biology Centre, Uppsala UniversityUppsalaSweden
- Department of SciencesMuseum VictoriaMelbourneAustralia
| | - Benedict King
- College of Science and EngineeringFlinders UniversityAdelaideAustralia
- Naturalis Biodiversity CenterLeidenNetherlands
| | - Sam Giles
- Department of Earth SciencesUniversity of OxfordOxfordUnited Kingdom
| | - Brian Choo
- College of Science and EngineeringFlinders UniversityAdelaideAustralia
| | - Per E Ahlberg
- Department of Organismal BiologyEvolutionary Biology Centre, Uppsala UniversityUppsalaSweden
| | - Gavin C Young
- Department of Applied MathematicsResearch School of Physics & Engineering, Australian National UniversityCanberraAustralia
- Australian Museum Research InstituteSydneyAustralia
| | - John A Long
- College of Science and EngineeringFlinders UniversityAdelaideAustralia
- Department of SciencesMuseum VictoriaMelbourneAustralia
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