Zerina Johanson

Copulation in antiarch placoderms and the origin of gnathostome internal fertilisation

Publisher: Springer Science and Business Media LLC

Date: 19-10-2015

DOI: 10.1038/NATURE13825

Abstract: Reproduction in jawed vertebrates (gnathostomes) involves either external or internal fertilization. It is commonly argued that internal fertilization can evolve from external, but not the reverse. Male copulatory claspers are present in certain placoderms, fossil jawed vertebrates retrieved as a paraphyletic segment of the gnathostome stem group in recent studies. This suggests that internal fertilization could be primitive for gnathostomes, but such a conclusion depends on demonstrating that copulation was not just a specialized feature of certain placoderm subgroups. The reproductive biology of antiarchs, consistently identified as the least crownward placoderms and thus of great interest in this context, has until now remained unknown. Here we show that certain antiarchs possessed dermal claspers in the males, while females bore paired dermal plates inferred to have facilitated copulation. These structures are not associated with pelvic fins. The clasper morphology resembles that of ptyctodonts, a more crownward placoderm group, suggesting that all placoderm claspers are homologous and that internal fertilization characterized all placoderms. This implies that external fertilization and spawning, which characterize most extant aquatic gnathostomes, must be derived from internal fertilization, even though this transformation has been thought implausible. Alternatively, the substantial morphological evidence for placoderm paraphyly must be rejected.

Mosaicism in a new Eocene pufferfish highlights rapid morphological innovation near the origin of crown tetraodontiforms

Publisher: Wiley

Date: 10-06-2016

DOI: 10.1111/PALA.12245

Embryonic development of fin spines in Callorhinchus milii (Holocephali); implications for chondrichthyan fin spine evolution

Publisher: Wiley

Date: 11-2014

DOI: 10.1111/EDE.12104

Abstract: Fin spines are commonly known from fossil gnathostomes (jawed vertebrates) and are usually associated with paired and unpaired fins. They are less common among extant gnathostomes, being restricted to the median fins of certain chondrichthyans (cartilaginous fish), including chimaerids (elephant sharks) and neoselachians (sharks, skates, and rays). Fin spine growth is of great interest and relevance but few studies have considered their evolution and development. We investigated the development of the fin spine of the chimaerid Callorhinchus milii using stained histological sections from a series of larval, hatchling, and adult in iduals. The lamellar trunk dentine of the Callorhinchus spine first condenses within the mesenchyme, rather than at the contact surface between mesenchyme and epithelium, in a manner more comparable to dermal bone formation than to normal odontode development. Trabecular dentine forms a small component of the spine under the keel it is covered externally with a thin layer of lamellar trunk dentine, which is difficult to distinguish in sectioned adult spines. We suggest that the distinctive characteristics of the trunk dentine may reflect an origin through co-option of developmental processes involved in dermal bone formation. Comparison with extant Squalus and a range of fossil chondrichthyans shows that Callorhinchus is more representative than Squalus of generalized chondrichthyan fin-spine architecture, highlighting its value as a developmental model organism.

The English Chalk and London Clay: two remarkable British bony fish Lagerstätten

Publisher: Geological Society of London

Date: 23-11-2015

DOI: 10.1144/SP430.18

Fish fingers: digit homologues in sarcopterygian fish fins

Publisher: Wiley

Date: 2007

DOI: 10.1002/JEZ.B.21197

Abstract: A defining feature of tetrapod evolutionary origins is the transition from fish fins to tetrapod limbs. A major change during this transition is the appearance of the autopod (hands, feet), which comprises two distinct regions, the wrist/ankle and the digits. When the autopod first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before the full complement of wrist/ankle bones. Early tetrapod wrists/ankles, including those with a full complement of bones, also show a sharp pattern discontinuity between proximal elements and distal elements. This suggests the presence of a discontinuity in the proximal-distal sequence of development. Such a discontinuity occurs in living urodeles, where digits form before completion of the wrist/ankle, implying developmental independence of the digits from wrist/ankle elements. We have observed comparable independent development of pectoral fin radials in the lungfish Neoceratodus (Osteichthyes: Sarcopterygii), relative to homologues of the tetrapod limb and proximal wrist elements in the main fin axis. Moreover, in the Neoceratodus fin, expression of Hoxd13 closely matches late expression patterns observed in the tetrapod autopod. This evidence suggests that Neoceratodus fin radials and tetrapod digits may be patterned by shared mechanisms distinct from those patterning the proximal fin/limb elements, and in that sense are homologous. The presence of independently developing radials in the distal part of the pectoral (and pelvic) fin may be a general feature of the Sarcopterygii.

Oldest coelacanth, from the Early Devonian of Australia

Publisher: The Royal Society

Date: 21-03-2006

DOI: 10.1098/RSBL.2006.0470

Abstract: Coelacanths are well-known sarcopterygian (lobe-finned) fishes, which together with lungfishes are the closest extant relatives of land vertebrates (tetrapods). Coelacanths have both living representatives and a rich fossil record, but lack fossils older than the late Middle Devonian (385–390 Myr ago), conflicting with current phylogenies implying coelacanths erged from other sarcopterygians in the earliest Devonian (410–415 Myr ago). Here, we report the discovery of a new coelacanth from the Early Devonian of Australia (407–409 Myr ago), which fills in the approximately 20 Myr ‘ghost range’ between previous coelacanth records and the predicted origin of the group. This taxon is based on a single lower jaw bone, the dentary, which is deep and short in form and possesses a dentary sensory pore, otherwise seen in Carboniferous and younger taxa.

Development of the Synarcual in the Elephant Sharks (Holocephali; Chondrichthyes): Implications for Vertebral Formation and Fusion

Publisher: Public Library of Science (PLoS)

Date: 04-09-2015

DOI: 10.1371/JOURNAL.PONE.0135138

Evolution of Vertebrate Reproduction

Publisher: Cambridge University Press

Date: 31-12-2018

DOI: 10.1017/9781316832172.013

Foreword: special issue on ‘transformative reparations for sexual violence post-conflict: prospects and problems’^†

Publisher: Informa UK Limited

Date: 05-10-2017

DOI: 10.1080/13642987.2017.1366622

NEW MORPHOLOGICAL INFORMATION ON THE PTYCTODONTID FISHES (PLACODERMI, PTYCTODONTIDA) FROM WESTERN AUSTRALIA

Publisher: Informa UK Limited

Date: 26-06-2012

DOI: 10.1080/02724634.2012.661379

Open data and digital morphology

Publisher: The Royal Society

Date: 12-04-2017

DOI: 10.1098/RSPB.2017.0194

Abstract: Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.

Devonian arthrodire embryos and the origin of internal fertilization in vertebrates

Publisher: Springer Science and Business Media LLC

Date: 02-2009

DOI: 10.1038/NATURE07732

Abstract: Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi, an extinct class of armoured fish, indicating a viviparous mode of reproduction in a vertebrate group outside the crown-group Gnathostomata (Chondrichthyes and Osteichthyes). These embryos were found in ptyctodontids, a small group of placoderms phylogenetically basal to the largest group, the Arthrodira. Here we report the discovery of embryos in the Arthrodira inside specimens of Incisoscutum ritchiei from the Upper Devonian Gogo Formation of Western Australia (approximately 380 million years ago), providing the first evidence, to our knowledge, for reproduction using internal fertilization in this erse group. We show that Incisoscutum and some phyllolepid arthrodires possessed pelvic girdles with long basipterygia that articulated distally with an additional cartilaginous element or series, as in chondrichthyans, indicating that the pelvic fin was used in copulation. As homology between similar pelvic girdle skeletal structures in ptyctodontids, arthrodires and chondrichthyans is difficult to reconcile in the light of current phylogenies of lower gnathostomes, we explain these similarities as being most likely due to convergence (homoplasy). These new finds confirm that reproduction by internal fertilization and viviparity was much more widespread in the earliest gnathostomes than had been previously appreciated.

Development of teeth and jaws in the earliest jawed vertebrates

Publisher: Springer Science and Business Media LLC

Date: 17-10-2012

DOI: 10.1038/NATURE11555

Abstract: Teeth and jaws constitute a model of the evolutionary developmental biology concept of modularity and they have been considered the key innovations underpinning a classic ex le of adaptive radiation. However, their evolutionary origins are much debated. Placoderms comprise an extinct sister clade or grade to the clade containing chondrichthyans and osteichthyans, and although they clearly possess jaws, previous studies have suggested that they lack teeth, that they possess convergently evolved tooth-like structures or that they possess true teeth. Here we use synchrotron radiation X-ray tomographic microscopy (SRXTM) of a developmental series of Compagopiscis croucheri (Arthrodira) to show that placoderm jaws are composed of distinct cartilages and gnathal ossifications in both jaws, and a dermal element in the lower jaw. The gnathal ossification is a composite of distinct teeth that developed in succession, polarized along three distinct vectors, comparable to tooth families. The teeth are composed of dentine and bone, and show a distinct pulp cavity that is infilled centripetally as development proceeds. This pattern is repeated in other placoderms, but differs from the structure and development of tooth-like structures in the postbranchial lamina and dermal skeleton of Compagopiscis and other placoderms. We interpret this evidence to indicate that Compagopiscis and other arthrodires possessed teeth, but that tooth and jaw development was not developmentally or structurally integrated in placoderms. Teeth did not evolve convergently among the extant and extinct classes of early jawed vertebrates but, rather, successional teeth evolved within the gnathostome stem-lineage soon after the origin of jaws. The chimaeric developmental origin of this model of modularity reflects the distinct evolutionary origins of teeth and of component elements of the jaws.

Evolution of vertebrate postcranial complexity: axial skeleton regionalization and paired appendages in a Devonian jawless fish

Publisher: Wiley

Date: 05-07-2018

DOI: 10.1111/PALA.12379

NEW ONYCHODONTIFORM (OSTEICHTHYES; SARCOPTERYGII) FROM THE LOWER DEVONIAN OF VICTORIA, AUSTRALIA

Publisher: Cambridge University Press (CUP)

Date: 09-2007

DOI: 10.1666/PLEO05-023.1

Fossilized ontogenies: the contribution of placoderm ontogeny to our understanding of the evolution of early gnathostomes

Publisher: Wiley

Date: 07-01-2014

DOI: 10.1111/PALA.12093

Questioning hagfish affinities of the enigmatic Devonian vertebratePalaeospondylus

Publisher: The Royal Society

Date: 07-2017

DOI: 10.1098/RSOS.170214

Abstract: Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic affinities have been debated since it was first described. Most recently, Palaeospondylus has been identified as a stem-group hagfish (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of the cartilaginous skull, a feature of jawed vertebrates. Additionally, new tomographic data reveal that the following characters of crown-group gnathostomes (chondrichthyans + osteichthyans) are present in Palaeospondylus : a longer telencephalic region of the braincase, separation of otic and occipital regions by the otico-occipital fissure, and vertebral centra. As well, a precerebral fontanelle and postorbital articulation of the palatoquadrate are characteristic of certain chondrichthyans. Similarities in the structure of the postorbital process to taxa such as Pucap ella , and possible presence of the ventral cranial fissure, both support a resolution of Pa. gunni as a stem chondrichthyan. The internally mineralized cartilaginous skeleton in Palaeospondylus may represent a stage in the loss of bone characteristic of the Chondrichthyes.

Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires

Publisher: Springer Science and Business Media LLC

Date: 13-07-2009

DOI: 10.1038/NATURE08176

Abstract: Recent finds 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), 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 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.

Early vertebrates and the emergence of jaws

Publisher: Springer International Publishing

Date: 2019

DOI: 10.1007/978-3-319-93560-7_2

Chondrichthyan Evolution, Diversity, and Senses

Publisher: Springer International Publishing

Date: 2019

DOI: 10.1007/978-3-319-93560-7_4

Evolution and development of the synarcual in early vertebrates

Publisher: Springer Science and Business Media LLC

Date: 17-07-2012

DOI: 10.1007/S00435-012-0169-9

A new species ofBarameda(Rhizodontida) and heterochrony in the rhizodontid pectoral fin

Publisher: Informa UK Limited

Date: 12-06-2007

DOI: 10.1671/0272-4634(2007)27[295:ANSOBR]2.0.CO;2

Pelvic and reproductive structures in placoderms (stem gnathostomes)

Publisher: Wiley

Date: 02-06-2015

DOI: 10.1111/BRV.12118

Abstract: Newly discovered pelvic and reproductive structures within placoderms, representing some of the most crownward members of the gnathostome stem group and the most basal jawed vertebrates, challenge established ideas on the origin of the pelvic girdle and reproductive complexity. Here we critically review previous descriptions of the pelvic structures in placoderms and reinterpret the morphology of the pelvic region within the arthrodires and ptyctodonts, in particular the position of the pelvic fin and the relationship of the male clasper to the pelvic girdle. Absence of clear articular surfaces on the clasper and girdle in the Arthrodira, along with evidence from the Ptyctodontida, suggest that these are separate structures along the body. We describe similarities between the pectoral and pelvic girdles and claspers, for ex le, all these have both dermal and perichondral (cartilaginous) components. Claspers in placoderms and chondrichthyans develop in very different ways in sharks, claspers develop from the pelvic fin while the claspers in placoderms develop separately, suggesting that their independent development involved a posterior extension of the 'competent stripes' for fin development previously limited to the region between the paired pectoral and pelvic fins. Within this expanded zone, we suggest that clasper position relative to the pelvic fins was determined by genes responsible for limb position. Information on early gnathostome reproductive processes is preserved in both the Ptyctodontida and Arthrodira, including the presence of multiple embryos in pregnant females, embryos of differing sizes and of different sexes (e.g. male claspers preserved in some embyros). By comparison with chondrichthyans, these observations suggest more complex reproductive strategies in placoderms than previously appreciated.

Natural History Museum

Location: United Kingdom of Great Britain and Northern Ireland

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Discovery Projects - Grant ID: DP110101127

Start Date: 08-2011

End Date: 03-2017

Amount: $710,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0663874

Start Date: 09-2006

End Date: 12-2008

Amount: $270,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP220100825

Start Date: 10-2022

End Date: 09-2025

Amount: $507,060.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP140104161

Start Date: 06-2014

End Date: 12-2018

Amount: $347,000.00

Funder: Australian Research Council