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  • 1.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Can fossils illuminate the evolution of gnathostome head development?2006In: European Society for Evolutionary Developmental Biology: The First and Founding Meeting, August 2006, Prague, 2006, p. 363-Conference paper (Other (popular scientific, debate etc.))
  • 2.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    CT scanning the nose of Eusthenopteron.2006In: Journal of Vertebrate Paleontology, ISSN 0272-4634, Vol. 26, no 3(supplement), p. 35A-Article in journal (Other scientific)
  • 3.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Fossils, developmental patterning and the origin of tetrapods.2003In: The new panorama of animal evolution, Pensoft Publishers, Sofia, Bulgaria , 2003, p. 45-54Chapter in book (Refereed)
  • 4.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Lär Livets Ords skola ut det?2007Other (Other (popular scientific, debate etc.))
  • 5.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ovederhäftiga angrepp på klimatforskning.2007Other (Other (popular scientific, debate etc.))
  • 6.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Science set in stone2007In: Nature, ISSN 0028-0836, Vol. 447, p. 37-38Article, book review (Other (popular scientific, debate etc.))
  • 7.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Tankefrihet eller pseudovetenskap?2005Other (Other (popular scientific, debate etc.))
  • 8.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Tro, vetande och tankefrihet.2005Other (Other (popular scientific, debate etc.))
  • 9.
    Ahlberg, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Beznosov, Pavel
    Luksevics, Ervins
    Clack, Jennifer
    A very primitive tetrapod from the earliest Famennian of South Timan, Russia2011In: Program and Abstracts: 71st Annual Meeting Society of Vertebrate Paleontology, Paris Las Vegas, Las Vegas, Nevada USA, November 2—5, 2011, Philadelphia: Society of Vertebrate Paleontology , 2011, p. 60-60Conference paper (Other academic)
  • 10.
    Ahlberg, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Clack, Jennifer
    Luksevics, Ervins
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Zupins, Ivars
    Ventastega curonica and the origin of tetrapod morphology2008In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 453, no 7199, p. 1199-1204Article in journal (Refereed)
    Abstract [en]

    The gap in our understanding of the evolutionary transition from fish to tetrapod is beginning to close thanks to the discovery of new intermediate forms such as Tiktaalik roseae. Here we narrow it further by presenting the skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica from the Late Devonian of Latvia, a transitional intermediate form between the 'elpistostegids' Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega. Ventastega is the most primitive Devonian tetrapod represented by extensive remains, and casts light on a part of the phylogeny otherwise only represented by fragmentary taxa: it illuminates the origin of principal tetrapod structures and the extent of morphological diversity among the transitional forms

  • 11.
    Ahlberg, Per E
    Natural History Museum of London.
    The intracranial joint in vertebrate phylogeny: (IVCM-4 abstracts)1994In: Journal of morphology (1931. Print), ISSN 0362-2525, E-ISSN 1097-4687, Vol. 220, no 3, p. 319-Article in journal (Other academic)
  • 12.
    Ahlberg, Per E.
    et al.
    Natural History Museum of London.
    Clack, J. A.
    The lower jaws of early tetrapods: morphology and evolution1997In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 17, no Suppl. 3, p. 28A-Article in journal (Other academic)
  • 13.
    Ahlberg, Per E.
    et al.
    Natural History Museum of London .
    Luksevics, E.
    New data on the head and shoulder skeletons of the primitive tetrapod Ventastega curonica1998In: Latvijas Geologijas Vestis, p. 34-40Article in journal (Other (popular science, discussion, etc.))
  • 14.
    Ahlberg, Per E.
    et al.
    Natural History Museum of London .
    Luksevics, E.
    Mark-Kurik, E.
    A near-tetrapod from the Baltic Middle Devonian2000In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 43, p. 533-548Article in journal (Refereed)
    Abstract [en]

    The tetrapodomorph sarcopterygian Livoniana multidentata gen. et sp. nov, is described on the basis of lower jaw fragments from the Middle Devonian (late Givetian) of Latvia and Estonia. It possesses a suite of derived characters previously only known fromtetrapods, which first appear in the late Devonian (late Frasnian), and a phylogenetic analysis places it on the internode between Panderichthys and the base of the Tetrapoda.The analysis also reveals that the 'Elpistostegalia' are paraphyletic to Tetrapoda, with Elpistostege closer to tetrapods than is Panderichthys. Owing to incompleteness of thematerial, there is almost no overlap between the data sets for Elpistostege and Livoniana;the analysis places the two genera in an unresolved trichotomy. In addition to the tetrapodfeatures, Livoniana has a strikingly autapomorphic dentary dentition comprising multiple tooth rows. It thus provides evidence both for the unexpectedly early evolution of tetrapodcharacteristics and for morphological radiation around the fish-tetrapod transition.

  • 15. Ahlberg, Per Erik
    Glimpsing the hidden majority1990In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 344, p. 23-Article in journal (Other academic)
  • 16.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Humeral homology and the origin of the tetrapod elbow: a reinterpretation of the enigmatic specimens ANSP 21350 and GSM 1045362011In: Studies on fossil tetrapods / [ed] P. M. Barrett, A. R. Milner, London: The Palaeontological Association , 2011, p. 17-29Chapter in book (Refereed)
    Abstract [en]

    Two putative tetrapod humeri of Devonian age, ANSP 21350 from the late Famennian of Pennsylvania and GSM 104536 from the late Frasnian of Scat Craig, Scotland, are reinterpreted in the light of more recent discoveries. The morphology of ANSP 21350 can be more fully homologized with those of elpistostegids and early tetrapods than previously recognized. Unique features include distally displaced dorsal muscle attachments and a ventrally rotated distal face of the bone. This suggests that a weight-bearing ventrally directed forearm was created, not by means of a flexed elbow as in other tetrapods, but by distorting the humerus. The olecranon process on the ulna was probably poorly developed or absent. Primitive characters that are absent in other tetrapods add support to the contention that ANSP 21350 is the least crownward of known tetrapod humeri. Contrary to previous claims, Acanthostega has a characteristic tetrapod ulnar morphology with an olecranon process; it does not resemble an elpistostegid ulna and is not uniquely primitive for tetrapods. This suggests that the flexed tetrapod elbow with ulnar extensor muscles attached to the olecranon evolved simultaneously with the large rectangular entepicondyle typical for early tetrapods, probably as part of a single functional complex. GSM 104536 is denfinitely not a primitive tetrapod humerus, nor a sarcopterygian branchial bone, but cannot be positively identified at present.    

  • 17.
    Ahlberg, Per Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Trinajstic, Kate
    Johanson, Zerina
    Long, John
    Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires2009In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 460, no 7257, p. 888-889Article in journal (Refereed)
    Abstract [en]

    Recent finds(1,2) demonstrate that internal fertilization and   viviparity (live birth) were more widespread in the Placodermi, an   extinct group of armoured fishes, than was previously realized.   Placoderms represent the sister group of the crown group jawed   vertebrates (Gnathostomata)(3,4), making their mode(s) of reproduction   potentially informative about primitive gnathostome conditions. An   ossified pelvic fin basipterygium discovered in the arthrodire   Incisoscutum ritchiei was hypothesized to be identical in males and   females, with males presumed to have an additional cartilaginous   element or series forming a clasper. Here we report the discovery of a   completely ossified pelvic clasper in Incisoscutum ritchiei (WAM   03.3.28) which shows that this interpretation was incorrect: the   basipterygium described previously(1) is in fact unique to females. The   male clasper is a slender rod attached to a square basal plate that   articulates directly with the pelvis. It carries a small cap of dermal   bone covered in denticles and small hooks that may be homologous with   the much larger dermal component of the ptyctodont clasper.

  • 18.
    Ahlberg, Per
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Köntges, Georgy
    Homologies and cell populations: a response to Sánchez-Villagra and Maier.2006In: Evolution and Development, ISSN 1520-541X, Vol. 8, p. 116-118Article in journal (Other (popular scientific, debate etc.))
  • 19.
    Ahlberg, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Smith, Moya
    MRC Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK.
    Johanson, Zerina
    Department of Biological Sciences and MUCEP, Department of Earth and Planetary Sciences, Macquarie University, Sydney 2010, Australia.
    Developmental plasticity and disparity in early dipnoan (lungfish) dentitions.2006In: Evolution & Development, ISSN 1520-541X, E-ISSN 1525-142X, Vol. 8, no 4, p. 331-349Article in journal (Refereed)
    Abstract [en]

    Although the lungfish (Dipnoi) belong within the Osteichthyes, their dentitions are radically different from other osteichthyans. Lungfish dentitions also show a uniquely high structural disparity during the early evolution of the group, partly owing to the independent variation of odontogenic and odontoclastic processes that are tightly and stereotypically coordinated in other osteichthyans. We present a phylogenetic analysis of early lungfishes incorporating a novel approach to coding these process characters in preference to the resultant adult dental morphology. The results only partially resolve the interrelationships of Devonian dipnoans, but show that the widely discussed hypothesis of separate tooth-plated, dentine-plated, and denticulated lineages is unlikely to be true. The dipnoan status of Diabolepis is corroborated. Lungfish dentitions seem to have undergone extensive and nonparsimonious evolution during the early history of the group, but much of the resulting disparity can be explained by a modest number of evolutionary steps in the underlying developmental processes, those for dental formation (odontogenic) and those for the remodeling of dentine tissue (odontoclastic). Later in lungfish evolution, this disparity was lost as the group settled to a pattern of dental development that is just as stereotypic as, but completely different from, that of other osteichthyans.

  • 20. Andrews, Mahala
    et al.
    Long, John
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Barwick, Richard
    Campbell, Kenton
    The structure of the sarcopterygian Onychodus jandemarrai n. sp. from Gogo, Western Australia: with a functional interpretation of the skeleton.2006In: Transactions of the Royal Society of Edinburgh: Earth Sciences, ISSN 0263-5933, Vol. 96, p. 197-307Article in journal (Refereed)
  • 21.
    Bazzi, Mohamad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Kear, Benjamin P.
    Uppsala University, Music and Museums, Museum of Evolution.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Campione, Nicolas E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Univ New England, Sch Environm & Rural Sci, Palaeosci Res Ctr, Armidale, NSW 2351, Australia.
    Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction2018In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 28, no 16, p. 2607-2615Article in journal (Refereed)
    Abstract [en]

    The Cretaceous-Palaeogene (K-Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades [1, 2]. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K-Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain [3]. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carch-arhiniformes (Ground sharks). These clades are prevalent predators in today's oceans, and were geographically widespread during the late Cretaceous-early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K-Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators [4, 5]. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing lowcrowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K-Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod [6] and pelagic amniote [5] groups, as well as the explosive radiation of middle trophic-level teleost fishes [1]. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic [7-10].

  • 22.
    Beznosov, Pavel A.
    et al.
    Russian Acad Sci, Ural Branch, Komi Sci Ctr, Inst Geol, Syktyvkar, Russia.
    Clack, Jennifer A.
    Univ Cambridge, Univ Museum Zool, Cambridge, England.
    Luksevics, Ervins
    Univ Latvia, Dept Geol, Riga, Latvia.
    Ruta, Marcello
    Univ Lincoln, Sch Life Sci, Joseph Banks Labs, Lincoln, England.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Morphology of the earliest reconstructable tetrapod Parmastega aelidae2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 574, no 7779, p. 527-531Article in journal (Refereed)
    Abstract [en]

    The known diversity of tetrapods of the Devonian period has increased markedly in recent decades, but their fossil record consists mostly of tantalizing fragments(1-15). The framework for interpreting the morphology and palaeobiology of Devonian tetrapods is dominated by the near complete fossils of Ichthyostega and Acanthostega; the less complete, but partly reconstructable, Ventastega and Tulerpeton have supporting roles(2,4,16-34). All four of these genera date to the late Famennian age (about 365-359 million years ago)-they are 10 million years younger than the earliest known tetrapod fragments(5,10), and nearly 30 million years younger than the oldest known tetrapod footprints(35). Here we describe Parmastega aelidae gen. et sp. nov., a tetrapod from Russia dated to the earliest Famennian age (about 372 million years ago), represented by three-dimensional material that enables the reconstruction of the skull and shoulder girdle. The raised orbits, lateral line canals and weakly ossified postcranial skeleton of P. aelidae suggest a largely aquatic, surface-cruising animal. In Bayesian and parsimony-based phylogenetic analyses, the majority of trees place Parmastega as a sister group to all other tetrapods.

  • 23.
    Blom, Henning
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Clack, Jennifer
    The postcranial skeleton of the Devonian tetrapod Ichthyostega from East Greenland.2005In: GFF, ISSN 1103-5897, Vol. 127, p. 45-Article in journal (Other scientific)
  • 24.
    Blom, Henning
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Clack, Jennifer
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Localities, distribution and stratigraphical context of the Late Devonian tetrapods of East Greenland.2005In: Meddelelser of Grönland, Geoscience, ISSN 0106-1046, Vol. 43, no 1, p. 4-50Article in journal (Refereed)
  • 25.
    Blom, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Jerve, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Qu, Qingming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Chen, Donglei
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Märss, Tiiu
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The affinity of Lophosteus and the evolution of osteichthyan characters2011Conference paper (Other academic)
  • 26.
    Blom, Henning
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Jerve, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Qu, Qinming
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Chen, Dong Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Märss, Tiiu
    Tallinn University of Technology.
    Dupret, Vincent
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The affinity of Lophosteus  and the evolution of osteichthyan characters2011Conference paper (Refereed)
  • 27.
    Boisvert, Catherine Anne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Joss, Jean
    Macquarie University.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Comparative pelvic development of the axolotl (Ambystoma mexicanum) and the Australian lungfish (Neoceratodus forsteri): conservation and innovation across the fish-tetrapod transition2013In: EvoDevo, ISSN 2041-9139, E-ISSN 2041-9139, Vol. 4, p. 3-Article in journal (Refereed)
    Abstract [en]

    Background: The fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. Although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. Relatively little attention has been paid to the transformation of the pelvic girdle from a small unipartite structure to a large tripartite weight-bearing structure, allowing tetrapods to rely mostly on their hindlimbs for locomotion. In order to understand how the ischium and the ilium evolved and how the acetabulum was reoriented during this transition, growth series of the Australian lungfish Neoceratodus forsteri and the Mexican axolotl Ambystoma mexicanum were cleared and stained for cartilage and bone and immunostained for skeletal muscles. In order to understand the myological developmental data, hypotheses about the homologies of pelvic muscles in adults of Latimeria, Neoceratodus and Necturus were formulated based on descriptions from the literature of the coelacanth (Latimeria), the Australian Lungfish (Neoceratodus) and a salamander (Necturus). Results: In the axolotl and the lungfish, the chondrification of the pelvic girdle starts at the acetabula and progresses anteriorly in the lungfish and anteriorly and posteriorly in the salamander. The ilium develops by extending dorsally to meet and connect to the sacral rib in the axolotl. Homologous muscles develop in the same order with the hypaxial musculature developing first, followed by the deep, then the superficial pelvic musculature. Conclusions: Development of the pelvic endoskeleton and musculature is very similar in Neoceratodus and Ambystoma. If the acetabulum is seen as being a fixed landmark, the evolution of the ischium only required pubic pre-chondrogenic cells to migrate posteriorly. It is hypothesized that the iliac process or ridge present in most tetrapodomorph fish is the precursor to the tetrapod ilium and that its evolution mimicked its development in modern salamanders.

  • 28.
    Boisvert, Catherine
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Mark-Kurik, Elga
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    The pectoral fin of Panderichthys and the origin of digits2008In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 456, no 7222, p. 636-638Article in journal (Refereed)
    Abstract [en]

    One of the identifying characteristics of tetrapods (limbed vertebrates) is the presence of fingers and toes. Whereas the proximal part of the tetrapod limb skeleton can easily be homologized with the paired fin skeletons of sarcopterygian (lobe-finned) fish, there has been much debate about the origin of digits. Early hypotheses1 interpreted digits as derivatives of fin radials, but during the 1990s the idea gained acceptance that digits are evolutionary novelties without direct equivalents in fish fin skeletons. This was partly based on developmental genetic data2, but also substantially on the pectoral fin skeleton of the elpistostegid (transitional fish/tetrapod) Panderichthys, which appeared to lack distal digit-like radials3. Here we present a CT scan study of an undisturbed pectoral fin of Panderichthys demonstrating that the plate-like 'ulnare' of previous reconstructions is an artefact and that distal radials are in fact present. This distal portion is more tetrapod-like than that found in Tiktaalik 4 and, in combination with new data about fin development in basal actinopterygians5, sharks6 and lungfish7, makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal radials present in all sarcopterygian fish.

  • 29.
    Brazeau, Martin
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    A new look at tetrapod middle ear origins: spiracle evolution in the Tetrapodomorpha.2005In: Journal of Vertebrate Paleontology, ISSN 0272-4634, Vol. 25, no 3, p. 39A-Article in journal (Other scientific)
  • 30.
    Brazeau, Martin
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Tetrapod-like middle ear architecture in a Devonian fish.2006In: Nature, Vol. 439, p. 318-321Article in journal (Refereed)
  • 31.
    Chen, Dong Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Alavi, Yasaman
    Univ Melbourne, Sch BioSci, Australia.
    Brazeau, Martin D.
    Imperial Coll London, Dept Life Sci, Berks, England.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Millward, David
    British Geol Survey, Lyell Ctr, Edinburgh, Midlothian, Scotland.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    A partial lower jaw of a tetrapod from "Romer's Gap"2018In: Earth and environmental science transactions of the Royal Society of Edinburgh, ISSN 1755-6910, E-ISSN 1755-6929, Vol. 108, no 1, p. 55-65Article in journal (Refereed)
    Abstract [en]

    The first half of the Mississippian or Early Carboniferous (Tournaisian to mid-Visean), an interval of about 20 million years, has become known as "Romer's Gap" because of its poor tetrapod record. Recent discoveries emphasise the differences between pre-"Gap" Devonian tetrapods, unambiguous stem-group members retaining numerous "fish" characters indicative of an at least partially aquatic lifestyle, and post-"Gap" Carboniferous tetrapods, which are far more diverse and include fully terrestrial representatives of the main crown-group lineages. It seems that "Romer's Gap" coincided with the cladogenetic events leading to the origin of the tetrapod crown group. Here, we describe a partial right lower jaw ramus of a tetrapod from the late Tournaisian or early Visean of Scotland. The large and robust jaw displays a distinctive character combination, including a significant mesial lamina of the strongly sculptured angular, an open sulcus for the mandibular lateral line, a non-ossified narrow Meckelian exposure, a well-defined dorsal longitudinal denticle ridge on the prearticular, and a mesially open adductor fossa. A phylogenctic analysis places this specimen in a trichotomy with Crassigyrinus and baphetids + higher tetrapods in the upper part of the tetrapod stem group, above Whatcheeria, Pederpes, Ossinodus, Sigournea and Greererpeton. It represents a small but significant step in the gradual closure of "Romer's Gap".

  • 32.
    Chen, Dong Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Tafforeau, Paul
    Estonian Marine Institute, University of Tartu.
    Märss, Tiiu
    Estonian Marine Institute, University of Tartu.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus 2017In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 5, article id 161084Article in journal (Refereed)
    Abstract [en]

    The numerous cushion-shaped tooth-bearing plates attributed to the stem-group osteichthyan Lophosteus superbus, which are argued here to represent the ancient form of inner dental arcade, display a unique and presumably primitive way of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent, gently recurved teeth arranged in transverse tooth files that diverge towards the lingual margin of the cushion. Three-dimensional (3D) reconstruction from propagation phase contrast synchrotron microtomography (PPC-SRμCT) reveals remnants of the first-generation teeth embedded in the basal plate that have never been discerned in any taxa. These teeth were shed by semi-basal resorption with the periphery of their bases retained as dentine rings. The rings are highly overlapped, which evidences tooth shedding prior to adding the next first-generation tooth. Later teeth at the same sites underwent cyclical replacing and shedding through basal resorption, producing stacks of buried resorption surfaces separated by bone of attachment. The number and spatial arrangement of resorption surfaces elucidates that basal resorption of replacement teeth had taken place at the older tooth sites before the addition of the youngest first-generation teeth at the lingual margin. Thus the replacement tooth buds cannot have been generated by a single permanent dental lamina, but must have arisen either from successional dental laminae associated with the predecessor teeth, or directly from the dental epithelium of these teeth. The virtual histological dissection of these Late Silurian microfossils broadens our understanding of the development of the gnathostome dental systems and the acquisition of the osteichthyan-type of tooth replacement. 

  • 33.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    A Partial Tetrapod Lower Jaw from “Romer’s Gap”2009In: SVP 69th Annual Meeting and the 57th Symposium of Vertebrate Palaeontology and Comparative Anatomy (SVPCA), 2009Conference paper (Other academic)
  • 34.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dental Development of the Stem Osteichthyan Andreolepis hedei Revealed by Three-dimensional Synchrotron Virtual Paleohistology2013In: Program and Abstracts: Society of Vertebrate Paleontology 73rd Annual meeting, 2013, p. 103-103Conference paper (Other academic)
  • 35.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Dental Development of the Stem Osteichthyan Andreolepis hedei Revealed by Three-dimensional Synchrotron Virtual Paleohistology2013Conference paper (Other academic)
  • 36.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Three-dimensional histology of tooth cushions of Lophosteus from the Late Silurian of Estonia2011In: Program and Abstracts: 71st Annual Meeting, Society of Vertebrate Paleontolog, Philadelphia: Society of Vertebrate Paleontology , 2011, p. 87-87Conference paper (Other academic)
  • 37.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Three-dimensional histology of tooth cushions of Lophosteus from the Upper Silurian of Estonia2011In: Abstracts: The 2nd Wiman meeting: Carl Wiman's Legacy: 100 years of Swedish Palaeontology: Uppsala 17–18 November 2011 / [ed] Benjamin P. Kear and Michael Streng, 2011, p. 5-6Conference paper (Other academic)
    Abstract [en]

    Lophosteus superbus from the Late Silurian of Estonia is one of the oldest and most plesiomorphic osteichthyans described to date. Unfortunately at present it is known only from fragmented dermal microremains. The affinities of Lophosteus are therefore controversial with the taxon placed as either basal to both actinopterygians and sarcopterygians, or ambiguously linked to either placoderms or acanthodians. To confound matters further, the character states diagnosing actinopterygians and sarcopterygians have recently been brought into question, and even monophyly of the traditional placoderm and acanthodian clades has been challenged. As a possible stem osteichthyan, Lophosteus could thus be central to our understanding of early gnathostome evolution and the origin of the osteichthyan body plan. Often the best-preserved, although incompletely documented, elements of Lophosteus are tooth cushions. These tooth-bearing arched ossicles could arguably be homologous with the parasymphysial tooth whorls in chondrichthyans, acanthodians, and sarcopterygians, or even the parasymphysial tooth plates in tetrapodomorphs. High-resolution synchrotron scans of 6 isolated tooth cushions from the Upper Silurian of Estonia has permitted a detailed reconstruction of their three-dimensional architecture. The absence of an enamel layer and the presence of large hollows (bigger than normal osteocytes) in the deepest lamellar layer confirmed assignment of the specimens to Lophosteus. The external surface displays irregularly distributed denticles and there are large parallel vessels running horizontally on the basal bone that feed the denticle rows internally. The odontodes have two distinct generations (with successive odontodes accreted between those of the preceding buried generation) and are organised in a similar manner to those found on Lophosteus scales. This new histological data on vascularization provides insight into early gnathostome tooth patterning and could contribute to future phylogenetic assessments.

  • 38.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sanchez, Sophie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab. European Synchrotron Radiat Facil, 6 Rue Jules Horowitz, F-38043 Grenoble, France..
    Tafforeau, Paul
    European Synchrotron Radiat Facil, 6 Rue Jules Horowitz, F-38043 Grenoble, France..
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    The stem osteichthyan Andreolepis and the origin of tooth replacement2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 539, no 7628, p. 237-+Article in journal (Refereed)
    Abstract [en]

    The teeth of gnathostomes (jawed vertebrates) show rigidly patterned, unidirectional replacement that may or may not be associated with a shedding mechanism. These mechanisms, which are critical for the maintenance of the dentition, are incongruently distributed among extant gnathostomes. Although a permanent tooth-generating dental lamina is present in all chondrichthyans, many tetrapods and some teleosts, it is absent in the non-teleost actinopterygians. Tooth-shedding by basal hard tissue resorption occurs in most osteichthyans (including tetrapods) but not in chondrichthyans. Here we report a three-dimensional virtual dissection of the dentition of a 424-million-year-old stem osteichthyan, Andreolepis hedei, using propagation phase-contrast synchrotron microtomography, with a reconstruction of its growth history. Andreolepis, close to the common ancestor of all extant osteichthyans, shed its teeth by basal resorption but probably lacked a permanent dental lamina. This is the earliest documented instance of resorptive tooth shedding and may represent the primitive osteichthyan mode of tooth replacement.

  • 39.
    Chen, Donglei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Janvier, Philippe
    Département Histoire de la Terre, Muséum National d'Histoire Naturelle,.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Scale morphology and squamation of the Late Silurian osteichthyan Andreolepis from Gotland, Sweden2012In: Historical Biology, ISSN 0891-2963, E-ISSN 1029-2381, Vol. 24, no 4, p. 411-423Article in journal (Refereed)
    Abstract [en]

    The origin of osteichthyans (bony fishes and tetrapods) dates back to the Late Silurian, but the early evolution of the group is poorly understood. Andreolepis is one of the oldest known osteichthyans, but exclusively documented by detached and fragmentary dermal microremains. A large data-set of Andreolepis scales from the Silurian of Gotland has been used to explore the scale morphology on different parts of the body. Landmark-based geometric morphometrics together with comparative anatomy and functional morphology has allowed 10 morphotypes to be identified and incorporated into a squamation model, in which scales are allocated to anterior-mid lateral flank scales, posterior lateral flank scales, caudal peduncle scales, pectoral peduncle scales, dorsal flank scales, dorsal fulcral scales, caudal fulcral scales, ventral flank scales, medioventral scales and cranial scales. The scale morphology and squamation pattern ofAndreolepis may be primitive for the Osteichthyes and thus informative about the acquisition of the osteichthyan body plan.

  • 40. Clack, Jennifer A.
    et al.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Blom, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Finney, Sarah M.
    A new genus of Devonian tetrapod from North-East Greenland, with new information on the lower jaw of Ichthyostega2012In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 55, no 1, p. 73-86Article in journal (Refereed)
    Abstract [en]

    A new genus and species of Devonian tetrapod has been identified from material collected in 1947 from the southern slope of Mt. Celsius, Ymer phi, North-East Greenland. The specimen preserves both lower jaws, partial palate, premaxillae and maxillae, with a natural mould of parts of the shoulder girdle. The new taxon, Ymeria denticulata, shows differences in dentition, skull ornament and lateral line expression from both Acanthostega and Ichthyostega, but it shows a closer resemblance to the latter. A cladistic analysis not only suggests that Ymeria lies adjacent to Ichthyostega on the tetrapod stem, but also reveals substantial topological instability. As the third genus and the fifth species of tetrapod identified from North-East Greenland, it demonstrates the high diversity of Devonian tetrapods in that region.

  • 41. Clack, Jennifer A.
    et al.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Sarcopterygians: From Lobe-Finned Fishes to the Tetrapod Stem Group2016In: Evolution of the Vertebrate Ear: Evidence from the Fossil Record / [ed] Jennifer A. Clack, Richard R. Fay, Arthur N. Popper, Springer Publishing Company, 2016, p. 51-70Chapter in book (Other academic)
    Abstract [en]

    The sarcopterygians or lobe-finned fishes is the group that gave rise to tetrapods, and they were the dominant bony fishes of the Devonian period. Their otic regions were constructed similarly to those of both the actinopterygians and chondrichthyans, their structure being the common inheritance of all jawed vertebrates. One distinguishing feature of the primitive sarcopterygian braincase was that the division between the anterior ethmosphenoid and posterior otoccipital section sof the braincase was marked by a flexible hinge joint, which is seen today in the modern coelacanth, Latimeria. The hyomandibular was long and projected ventrally with an opercular process that contacted the opercular bone and with the distal end associated indirectly with the jaw joint. It was a key component of the buccal pumping mechanism for breathing and feeding. The braincases of dipnoans (lungfishes) were the most highly modified of sarcopterygian braincases with consolidated fore and aft portions and reduction or loss of the hyomandibula. The utricle was enlarged in several fossil dipnoans, although the reason for this is not clear. The braincases of tetrapodomorph sarcopterygians differed little from the primitive condition in the group. The main modifications were to the more crownward and tetrapod-like forms from the Late Devonian. In these fishes, the hyomandibula was reduced in length, its contact with the opercular bone lost and, ultimately, the opercular bone itself disappeared. The spiracular notch and associated cleft increased in width and volume respectively, possibly resulting in increased air-breathing capacity and reduced use of the gill system.

  • 42. Clack, Jennifer
    et al.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Blom, Henning
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    New insights into the postcranial skeleton of Ichthyostega.2003In: Journal of Vertebrate Paleontology, ISSN 0272-4634, Vol. 23, no 3(supplement), p. 41A-Article in journal (Refereed)
  • 43. Clack, Jennifer
    et al.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Blom, Henning
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ontogeny of the humerus in Ichthyostega.2005In: PaleoBios, ISSN 0031-0298, Vol. 25, no 2 (supplement), p. 30-Article in journal (Other scientific)
  • 44. Clack, Jennifer
    et al.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Finney, Sarah
    Dominguez Alonso, Patricio
    Robinson, Jamie
    Ketcham, Richard
    A uniquely specialized ear in a very early tetrapod.2003In: Nature, ISSN 0028-0836, Vol. 425, no 6953, p. 66-69Article in journal (Refereed)
  • 45.
    Clement, Alice
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Ahlberg, Per Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The First Virtual Cranial Endocast of a Lungfish (Sarcopterygii: Dipnoi)2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 11, article id 0113898Article in journal (Refereed)
    Abstract [en]

    Lungfish, or dipnoans, have a history spanning over 400 million years and are the closest living sister taxon to the tetrapods. Most Devonian lungfish had heavily ossified endoskeletons, whereas most Mesozoic and Cenozoic lungfish had largely cartilaginous endoskeletons and are usually known only from isolated tooth plates or disarticulated bone fragments. There is thus a substantial temporal and evolutionary gap in our understanding of lungfish endoskeletal morphology, between the diverse and highly variable Devonian forms on the one hand and the three extant genera on the other. Here we present a virtual cranial endocast of Rhinodipterus kimberleyensis, from the Late Devonian Gogo Formation of Australia, one of the most derived fossil dipnoans with a well-ossified braincase. This endocast, generated from a Computed Microtomography (µCT) scan of the skull, is the first virtual endocast of any lungfish published, and only the third fossil dipnoan endocast to be illustrated in its entirety. Key features include long olfactory canals, a telencephalic cavity with a moderate degree of ventral expansion, large suparaotic cavities, and moderately enlarged utricular recesses. It has numerous similarities to the endocasts of Chirodipterus wildungensis and Griphognathus whitei, and to a lesser degree to 'Chirodipterus' australis and Dipnorhynchus sussmilchi. Among extant lungfish, it consistently resembles Neoceratodus more closely than Lepidosiren and Protopterus. Several trends in the evolution of the brains and labyrinth regions in dipnoans, such as the expansions of the utricular recess and telencephalic regions over time, are identified and discussed.

  • 46.
    Clement, Alice
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Flinders Univ S Australia, Coll Sci & Engn, Adelaide, SA, Australia;Museum Victoria, Dept Sci, Melbourne, Vic, Australia.
    King, Benedict
    Flinders Univ S Australia, Coll Sci & Engn, Adelaide, SA, Australia;Nat Biodivers Ctr, Leiden, Netherlands.
    Giles, Sam
    Univ Oxford, Dept Earth Sci, Oxford, England.
    Choo, Brian
    Flinders Univ S Australia, Coll Sci & Engn, Adelaide, SA, Australia.
    Ahlberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Young, Gavin C.
    Australian Natl Univ, Res Sch Phys & Engn, Dept Appl Math, Canberra, ACT, Australia;Australian Museum, Res Inst, Sydney, NSW, Australia.
    Long, John A.
    Flinders Univ S Australia, Coll Sci & Engn, Adelaide, SA, Australia;Museum Victoria, Dept Sci, Melbourne, Vic, Australia.
    Neurocranial anatomy of an enigmatic Early Devonian fish sheds light on early osteichthyan evolution2018In: eLIFE, E-ISSN 2050-084X, Vol. 7, article id e34349Article in journal (Refereed)
    Abstract [en]

    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.

  • 47.
    Clement, Alice M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Flinders Univ S Australia, Sch Biol Sci, GPO Box 2100, Adelaide, SA 5001, Australia..
    Long, J. A.
    Flinders Univ S Australia, Sch Biol Sci, GPO Box 2100, Adelaide, SA 5001, Australia..
    Tafforeau, P.
    Flinders Univ S Australia, Sch Biol Sci, GPO Box 2100, Adelaide, SA 5001, Australia.;European Synchrotron Radiat Facil, 71 Ave Martyrs, F-38043 Grenoble, France..
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology. Flinders Univ S Australia, Sch Biol Sci, GPO Box 2100, Adelaide, SA 5001, Australia..
    The dipnoan buccal pump reconstructed in 3D and implications for air breathing in Devonian lungfishes2016In: Paleobiology, ISSN 0094-8373, E-ISSN 1938-5331, Vol. 42, no 2, p. 289-304Article in journal (Refereed)
    Abstract [en]

    Lungfishes are known for, and indeed take their name from, their bimodal respiratory abilities. All three extant genera can use their lungs to extract oxygen from the atmosphere, although their reliance upon this capability differs among taxa. Lungs are considered primitive for the Osteichthyes, however the distinctive buccal pump mode of air gulping exhibited by extant lungfishes appears to be a specialization. It is associated with a number of derived skeletal characters (cranial ribs, long parasphenoid stalk, midline gap between palatal tooth plates) that first appeared during the Devonian. These have been described individually, but in no Devonian lungfish has their three-dimensional (3D) spatial relationship been reconstructed and analyzed. Here we present the 3D morphology of Rhinodipterus, a Mid-Late Devonian lungfish from Australia and Europe, based on synchrotron tomography and conventional microtomography scans. Unlike less crownward contemporaneous lungfishes such as Griphognathus and Chirodipterus, Rhinodipterus has a full set of skeletal buccal pump components that can be directly compared to those of extant lungfishes, suggesting that it made more extensive use of air breathing than other Gogo or Bergisch Gladbach genera. This is interesting in relation to the environmental context as Gogo and Bergisch Gladbach are both marine, contrasting with the frequently hypoxic tropical to subtropical fresh water environments inhabited by modern lungfishes. The evolution of buccal pump-supported lung ventilation was evidently not necessarily associated with a transition to non-marine habitats.

  • 48.
    Clement, Alice M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Nysjö, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Strand, Robin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Ahlberg, Per E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    Brain – Endocast relationship in the Australian lungfish, Neoceratodus forsteri, elucidated from tomographic data (Sarcopterygii: Dipnoi)2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 10, article id e0141277Article in journal (Refereed)
    Abstract [en]

    Although the brains of the three extant lungfish genera have been previously described, the spatial relationship between the brain and the neurocranium has never before been fully described nor quantified. Through the application of virtual microtomography (mu CT) and 3D rendering software, we describe aspects of the gross anatomy of the brain and labyrinth region in the Australian lungfish, Neoceratodus forsteri and compare this to previous accounts. Unexpected characters in this specimen include short olfactory peduncles connecting the olfactory bulbs to the telencephalon, and an oblong telencephalon. Furthermore, we illustrate the endocast (the mould of the internal space of the neurocranial cavity) of Neoceratodus, also describing and quantifying the brain-endocast relationship in a lungfish for the first time. Overall, the brain of the Australian lungfish closely matches the size and shape of the endocast cavity housing it, filling more than four fifths of the total volume. The forebrain and labyrinth regions of the brain correspond very well to the endocast morphology, while the midbrain and hindbrain do not fit so closely. Our results cast light on the gross neural and endocast anatomy in lungfishes, and are likely to have particular significance for palaeoneurologists studying fossil taxa.

  • 49.
    Clément, Gael
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    Ahlberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology. Evolutionär organismbiologi.
    The endocranial anatomy of the early sarcopterygian Powichthys from Spitsbergen revealed by high-resolution CT scans.2005In: Journal of Vertebrate Paleontology, ISSN 0272-4634, Vol. 25, no 3, p. 46A-Article in journal (Other scientific)
  • 50.
    Clément, Gaël
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology.
    Ahlberg, Per E
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Evolution and Developmental Biology.
    The endocranial anatomy of the early sarcopterygian Powichthys from Spitsbergen, based on CT scanning2010In: Morphology, Phylogeny and Paleobiogeography of Fossil Fishes: honoring Meemann Chang / [ed] David K. Elliott, John G. Maisey, Xiaobo Yu, Desui Miao, München: Dr. Friedrich Pfeil , 2010, p. 363-377Chapter in book (Other academic)
123 1 - 50 of 124
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