- Flinders University, POB 2100, Adelaide, South Australia, Australia 5001
John Long
Flinders University of South Australia, Biological Sciences, Faculty Member
- My principal research interests concern how the human body plan was asembled from various evolutionary innovations th... moreMy principal research interests concern how the human body plan was asembled from various evolutionary innovations that originated in Early Palaeozoic fishes-eg limbs and girdles, jaws, teeth, axial skeleton, complex skull patterns etc as wellas the origin of various physiological traits like breathing and complex reproductive strategies etc. Early gnathostome fossils provide a wealth of such data if well preserved and properly prepared.edit
"We all know about the birds and the bees, but what about the ancient placoderm fishes and the dinosaurs? The history of sex is as old as life itself—and as complicated and mysterious. And despite centuries of study there is always more... more
"We all know about the birds and the bees, but what about the ancient placoderm fishes and the dinosaurs? The history of sex is as old as life itself—and as complicated and mysterious. And despite centuries of study there is always more to know. In 2008, paleontologist John A. Long and a team of researchers revealed their discovery of a placoderm fish fossil, known as “the mother fish,” which at 380 million years old revealed the oldest vertebrate embryo—the earliest known example of internal fertilization. As Long explains, this find led to the reexamination of countless fish fossils and the discovery of previously undetected embryos. As a result, placoderms are now considered to be the first species to have had intimate sexual reproduction or sex as we know it—sort of.
Inspired by this incredible find, Long began a quest to uncover the paleontological and evolutionary history of copulation and insemination. In The Dawn of the Deed, he takes readers on an entertaining and lively tour through the sex lives of ancient fish and exposes the unusual mating habits of arthropods, tortoises, and even a well-endowed (16.5 inches!) Argentine Duck. Long discusses these significant discoveries alongside what we know about reproductive biology and evolutionary theory, using the fossil record to provide a provocative account of prehistoric sex. The Dawn of the Deed also explores fascinating revelations about animal reproduction, from homosexual penguins to monogamous seahorses to the difficulties of dinosaur romance and how sexual organs in ancient shark-like fishes actually relate to our own sexual anatomy.
The Dawn of the Deed is Long’s own story of what it’s like to be a part of a discovery that rewrites evolutionary history as well as an absolutely rollicking guide to sex throughout the ages in the animal kingdom. It’s natural history with a naughty wink."
FURTHER INFO: a cheaperc paperback edition will be coming out in April 2014 from U.Chicago Press, and foreign language editions in Spanish, Russian, German, Chinese, Korean will be ouit soon too!
Inspired by this incredible find, Long began a quest to uncover the paleontological and evolutionary history of copulation and insemination. In The Dawn of the Deed, he takes readers on an entertaining and lively tour through the sex lives of ancient fish and exposes the unusual mating habits of arthropods, tortoises, and even a well-endowed (16.5 inches!) Argentine Duck. Long discusses these significant discoveries alongside what we know about reproductive biology and evolutionary theory, using the fossil record to provide a provocative account of prehistoric sex. The Dawn of the Deed also explores fascinating revelations about animal reproduction, from homosexual penguins to monogamous seahorses to the difficulties of dinosaur romance and how sexual organs in ancient shark-like fishes actually relate to our own sexual anatomy.
The Dawn of the Deed is Long’s own story of what it’s like to be a part of a discovery that rewrites evolutionary history as well as an absolutely rollicking guide to sex throughout the ages in the animal kingdom. It’s natural history with a naughty wink."
FURTHER INFO: a cheaperc paperback edition will be coming out in April 2014 from U.Chicago Press, and foreign language editions in Spanish, Russian, German, Chinese, Korean will be ouit soon too!
A completely revised, updated edition of the well-known 1995 version, with about 30% new illustrations and is now 284pp. Covers the origins and diversification of the first vertebrates, all main groups of extinct fishes (new chapters on... more
A completely revised, updated edition of the well-known 1995 version, with about 30% new illustrations and is now 284pp. Covers the origins and diversification of the first vertebrates, all main groups of extinct fishes (new chapters on teleosts and basal sarcopterygians added), plus a new Foreward by Phillippe Janvier. Available through Johns Hopkins (USA) and UNSW Press (Aust).
A complete review of the palaeontology of Antarctica, from Cambrian reefs to Holocene deposits, with artist's restorations of many key species from Devonian fishes, dinosaurs, marine reptile to giant penguins. Available by mail order from... more
A complete review of the palaeontology of Antarctica, from Cambrian reefs to Holocene deposits, with artist's restorations of many key species from Devonian fishes, dinosaurs, marine reptile to giant penguins. Available by mail order from C.S.I.R.O. Publishing, Melbourne, Australia; see link above.
A popular style book that narrates the discovery fo the 'mother fish' (a Devonian ptyctodontid) with embryo and related finds of arthrodires with embryos indicating early reprpoductive systems in placoderms, and reviews what we know from... more
A popular style book that narrates the discovery fo the 'mother fish' (a Devonian ptyctodontid) with embryo and related finds of arthrodires with embryos indicating early reprpoductive systems in placoderms, and reviews what we know from the fossil record of animal reproductive behaviour, as well as ventuyring into variability of animal sexuality in the modern world, touching lightly on sexual selection, sperm competition and the role of evo-devo studies in understanding early vertebrate evolution.
Endorsements by Jared Diamond, Tim Flannery, Robyn Williams and Carmelo Amelfi.
Endorsements by Jared Diamond, Tim Flannery, Robyn Williams and Carmelo Amelfi.
A simple colour book for upper primary school kids (aged 9-12)about where the big ideas that defined intellectual progress in human civilisation came from, starting with cave paintings and ideas from ancient Egypt, Greece, India etc.
An informative picture book for 8-12 year olds about our natural environments-the biomes (eg deserts, rainforest, reefs etc) and how climate change is effecting each of them. Paints two futuristic pictures of what will happen if we do... more
An informative picture book for 8-12 year olds about our natural environments-the biomes (eg deserts, rainforest, reefs etc) and how climate change is effecting each of them. Paints two futuristic pictures of what will happen if we do nothing to mitigate the problem, or if we take action now. Was shortlisted for an Australian Publishers Association best refernce book award.
A pictorial account using superb artistic restorations of the known and inferred likley feathered dinosaurs, with brief introductory text, based on the latest scientific information as of early 2008. Foreward by Luis Chiappe, endorsed by... more
A pictorial account using superb artistic restorations of the known and inferred likley feathered dinosaurs, with brief introductory text, based on the latest scientific information as of early 2008. Foreward by Luis Chiappe, endorsed by T. Flannery, P.Vickers-Rich.
From the first microscopic forms of life to the evolution of the first animals crawling and swimming in the oceans; from feathered dinosaurs to whales with legs; from the first flower to the first humans, this volume takes readers on a... more
From the first microscopic forms of life to the evolution of the first animals crawling and swimming in the oceans; from feathered dinosaurs to whales with legs; from the first flower to the first humans, this volume takes readers on a journey through time to show that these myriad designs were produced not by intelligence, but by the wonder of evolution. The earth's long-playing fossil record, the book explains, is a testament to the evolution of life on this planet over the past 3.5 billion years. Paleontologists show how recent fossil discoveries, especially those in Australia, are revolutionizing our understanding of the patterns and processes of animal, plant, and microbial evolution.
Publishers blurb: John Long has spent 20 years working at the world-renowned Gogo fish fossil sites. In this amazing story, Long chronicles the history of the sites and takes the reader on a journey of adventure, human endeavor and... more
Publishers blurb: John Long has spent 20 years working at the world-renowned Gogo fish fossil sites. In this amazing story, Long chronicles the history of the sites and takes the reader on a journey of adventure, human endeavor and intrigue with insights into the very nature of scientific study.
Paleontologist Long sets out for the Southern continent twice, the first time in December of 1988 and again in October of 1991, on an expedition sponsored by the National Geographic Society. Like the fossil hunters described in HP... more
Paleontologist Long sets out for the Southern continent twice, the first time in December of 1988 and again in October of 1991, on an expedition sponsored by the National Geographic Society. Like the fossil hunters described in HP Lovecraft's classic novella, At the Mountains of Madness, Long heads straight for the frigid silhouette painted by the Transantarctic Mountain range. It is a profoundly lonely and desolate place, but it is also a scientist's playground.
This book was written to introduce to upper primary and lower secondary level children an outline of the three main themes that contribute towards our understanding of evolution: time, physical processes, and biological change. The book... more
This book was written to introduce to upper primary and lower secondary level children an outline of the three main themes that contribute towards our understanding of evolution: time, physical processes, and biological change. The book can be used to augment studies in general science (astronomy, geology, biology), but also to contribute to an understanding of the birth of human culture and to promote discussion of environmental issues confronting the world today.
A complete pictorial reviewof what was known about Australian and New Guinea fossil mammals up to 2002, publsihed by Johns Hopkins University Press (USA), and UNSW Press (Aust). A revised updated edtion is under consideration by the... more
A complete pictorial reviewof what was known about Australian and New Guinea fossil mammals up to 2002, publsihed by Johns Hopkins University Press (USA), and UNSW Press (Aust). A revised updated edtion is under consideration by the authors and UNSW Press at present.
A potted history about dealing in fossils and fossil legislation set around the true story of tracing some stolen dinsosaur footprints from Broome, Australia that went missing in 1996. Was made into a 2 part documentary series for TV by... more
A potted history about dealing in fossils and fossil legislation set around the true story of tracing some stolen dinsosaur footprints from Broome, Australia that went missing in 1996. Was made into a 2 part documentary series for TV by Electric Pictures/ Alley Kat Productions Fremantle. It also contains a useful appendix listing known fossil legislation for different countries as of 2002.
An true life account of 2 fossil hunting expeditions to Antarctica (1988-89, 19991-92) where we traversed over 700km sledging in the remote Transantarctic Mountains to collect Devonian fossils. Provides details of finding some excellent... more
An true life account of 2 fossil hunting expeditions to Antarctica (1988-89, 19991-92) where we traversed over 700km sledging in the remote Transantarctic Mountains to collect Devonian fossils. Provides details of finding some excellent Devonian fish fossils from the Aztec Siltstone sites in the Cook Mountains and Skeleton neve regions, and gives accounts of the dangers and dramas when working in the deep field of Antarctica.
Contains 30 papers in vertebrate palaeontology covering early vertebrates through to mammals with just over half the contributions on lower vertebartes. Still available to buy through the Western Australian Museum website for $24.75 Aus... more
Contains 30 papers in vertebrate palaeontology covering early vertebrates through to mammals with just over half the contributions on lower vertebartes.
Still available to buy through the Western Australian Museum website for $24.75 Aus plus shipping (very good value!).
Still available to buy through the Western Australian Museum website for $24.75 Aus plus shipping (very good value!).
Contains some 28 papers on invertebvrate and vertebrate palaentology, environmental settings, palaoebiogeography of Palaeozoic terranes and faunas. Still available from the Western Australian Museum website for about $33.75 plus shipping.
Full color coverage of Mesozoic tetrapod faunas of Australia nd New Zealand, updated from my 1991, 1993 BW editions, with much new information added.
Contains 13 chapters highlighting biostratigraphic and biogeographic utility of Palaeozoic vertebrates from around the world. Chapters include morphological features of Palaeozoic vertebrates, tectonic settings, extinctions events;... more
Contains 13 chapters highlighting biostratigraphic and biogeographic utility of Palaeozoic vertebrates from around the world. Chapters include morphological features of Palaeozoic vertebrates, tectonic settings, extinctions events; accounts of Paleozoic faunas from ASia, Europe, Russia,. Australia, and chapters on biogeography. Authors: Z.X. Li, C. Powell, P. Janvier, A. Blieck, S. Turtner, G.C. Young, A. trench, S.-T. Wang, H. Lelievre, A.R. Milner.
An academic directory and search engine.
—The phylogeny of early gnathostomes provides an important framework for understanding one of the most significant evolutionary events, the origin and diversification of jawed vertebrates. A series of recent cladistic analyses have... more
—The phylogeny of early gnathostomes provides an important framework for understanding one of the most significant evolutionary events, the origin and diversification of jawed vertebrates. A series of recent cladistic analyses have suggested that the placoderms, an extinct group of armoured fish, form a paraphyletic group basal to all other jawed vertebrates. We revised and expanded this morphological data set, most notably by sampling autapomorphies in a similar way to parsimony-informative traits, thus ensuring this data (unlike most existing morphological data sets) satisfied an important assumption of Bayesian tip-dated morphological clock approaches. We also found problems with characters supporting placoderm paraphyly, including character correlation and incorrect codings. Analysis of this data set reveals that paraphyly and monophyly of core placoderms (excluding maxillate forms) are essentially equally parsimonious. The two alternative topologies have different root positions for the jawed vertebrates but are otherwise similar. However, analysis using tip-dated clock methods reveals strong support for placoderm monophyly, due to this analysis favoring trees with more balanced rates of evolution. Furthermore, enforcing placoderm paraphyly results in higher levels and unusual patterns of rate heterogeneity among branches, similar to that generated from simulated trees reconstructed with incorrect root positions. These simulations also show that Bayesian tip-dated clock methods outperform parsimony when the outgroup is largely uninformative (e.g., due to inapplicable characters), as might be the case here. The analysis also reveals that gnathostomes underwent a rapid burst of evolution during the Silurian period which declined during the Early Devonian. This rapid evolution during a period with few articulated fossils might partly explain the difficulty in ascertaining the root position of jawed vertebrates.
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The bearing that agnathans have on the origin of jawed vertebrates is one of the great unsolved problems in vertebrate phylogeny. Here we propose a mechanism for the evolution of jaws in vertebrates based on a combination of evidence from... more
The bearing that agnathans have on the origin of jawed vertebrates is one of the great unsolved
problems in vertebrate phylogeny. Here we propose a mechanism for the evolution of jaws in
vertebrates based on a combination of evidence from the fossil record and from experimental
developmental biology. In chick embryos, osteogenesis can be evoked experimentally from scleral
mesenchyme by the same mandibular epithelium that evokes osteogenesis in the jaws. Sclerotic
bones appeared before jaws in vertebrate phylogeny and scleral ossicles and jaw skeletons are
linked by shared developmental processes. As only one group of fossil agnathans—the
Osteostraci—has ossified sclerotic bones, they alone possessed the inherent developmental
potential to develop bone in the lower jaws and are also considered the most probable sister taxon to gnathostomes
problems in vertebrate phylogeny. Here we propose a mechanism for the evolution of jaws in
vertebrates based on a combination of evidence from the fossil record and from experimental
developmental biology. In chick embryos, osteogenesis can be evoked experimentally from scleral
mesenchyme by the same mandibular epithelium that evokes osteogenesis in the jaws. Sclerotic
bones appeared before jaws in vertebrate phylogeny and scleral ossicles and jaw skeletons are
linked by shared developmental processes. As only one group of fossil agnathans—the
Osteostraci—has ossified sclerotic bones, they alone possessed the inherent developmental
potential to develop bone in the lower jaws and are also considered the most probable sister taxon to gnathostomes
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Palaeozoic microvertebrate remains are documented from the Point Hibbs Formation, Point Hibbs, western Tasmania. They comprise scales, teeth and omamented dermal bone from: acanthodians "Nostolepis" guangxiensis, Nostolepis spp.,... more
Palaeozoic microvertebrate remains are documented from the Point Hibbs Formation, Point Hibbs, western Tasmania. They comprise scales, teeth and omamented dermal bone from:
acanthodians "Nostolepis" guangxiensis, Nostolepis spp., Gomphonchus? bogongensis, Trundlelepis cervicostulata and Watsonacanthus? sp., onychodontiform sarcopterygians, and four types of placoderms. The microvertebrate fauna supports a Lower Devonian (Pragian) age for the deposIt, when compared with other eastern Australian occurrences of these taxa.
acanthodians "Nostolepis" guangxiensis, Nostolepis spp., Gomphonchus? bogongensis, Trundlelepis cervicostulata and Watsonacanthus? sp., onychodontiform sarcopterygians, and four types of placoderms. The microvertebrate fauna supports a Lower Devonian (Pragian) age for the deposIt, when compared with other eastern Australian occurrences of these taxa.
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New material of the Australian Lower Carboniferous rhizodontid Barameda provides additional information on poorly known aspects of rhizodontid anatomy, including the braincase and branchial arches, and indicates that two species of... more
New material of the Australian Lower Carboniferous rhizodontid Barameda provides additional information on poorly known aspects of rhizodontid anatomy, including the braincase and branchial arches, and indicates that two species of Barameda are present in the Mansfield Group, a larger poorly ossified species, B. decipiens, and a new species, Barameda mitchelli n. sp. based on the smaller well ossified specimens previously assigned to B. decipiens. Unusually, in a new pectoral fin specimen assigned to B. decipiens, the humerus lacks ossified entepicondylar and pectoral processes, strong projections present on the humeri of most sarcopterygian fish and tetrapods. Juveniles of rhizodontids and of Eusthenopteron (Tristichopteridae) also lack these processes (ossifying later in development), which along with poor overall ossification of the fin in juveniles and in B. decipiens, indicates that the pectoral fin of the latter has been affected by heterochronic processes. These observations suggest a degree of developmental variability (timing, degree of ossification) in the entepicondyle relative to the rest of the humerus, which could be extended to other posterior processes of pectoral fin elements such as the ulnare flange. This flange is present in tristichopterids but absent in rhizodontids and taxa closely related to the origin of tetrapods, such as Panderichthys.
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A diverse vertebrate fauna, comprising both micro- and macrovertebrate remains, is known from the Paleozoic of Western Australia. However, it is the Late Devonian fauna of the Gogo Formation that shows exceptional preservation and which... more
A diverse vertebrate fauna, comprising both micro- and macrovertebrate remains, is known from the Paleozoic of Western Australia. However, it is the Late Devonian fauna of the Gogo Formation that shows exceptional preservation and which is the best known. Advances in tomographic techniques, both micro-CT and synchrotron, have revealed new histological data providing information on bone growth, muscle attachments and the evolution of teeth. The fishes from the Gogo Formation have also revealed new information on the evolution of reproductive structures and live birth in early vertebrates. Recent work on the Frasnian reefs that crop out along the Lennard Shelf and mineral drillcore through Paleozoic sedimentary rocks have yielded scales of agnathan thelodonts, and the bones, teeth and scales of sharks, acanthodians and osteichthyans, all of which have increased our knowledge of Ordovician–Late Devonian microfaunas in the Canning Basin, contributing to our understanding of biostratigraphy and correlation within Australian and globally. Less work has been undertaken in the Carnarvon Basin, although like the Canning Basin this has concentrated on Late Devonian strata. More recently, work has commenced on describing Early Carboniferous faunas from the Canning, Carnarvon and Bonaparte basins. All this work is providing information on faunal patterns and exchange of vertebrates through the Paleozoic. However, the paleogeographic evidence provided by the vertebrates is sometimes at odds with palaeogeographic reconstructions based on palaeomagnetic evidenceand further investigation is required to resolve these differing interpretations.
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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... more
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 example, 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.
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.
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Sedimentary pyrite formed in the water column ,or during diagenesis in organic muds, provides an accessible proxy for sea water chemistry in the marine rock record. Except for Mo, U, Ni and Cr, surprisingly little is known about trace... more
Sedimentary pyrite formed in the water column ,or during diagenesis in organic muds, provides an accessible proxy for sea water chemistry in the marine rock record. Except for Mo, U, Ni and Cr, surprisingly little is known about trace element trendsi n the deep time oceans , even though they are critica lto developing better models for the evolution of the Earth’s atmosphere and evolutionary pathways of life. Here we introduce a novel approach to simultaneously quantify a suite of trace elements in sedimentary pyrite from marine black shales. These trace element concentrations, at least in a first-order sense, track the primary elemental abundances in coeval seawater. In general, the trace element patterns show significant variation of several orders of magnitude in the Archaean and Phanerozoic, but less variation on longer wave lengths in the Proterozoic. Certain trace elements (e.g.,Ni,Co,As,Cr) have generally decreased in the oceans through the Precambrian, other elements (e.g.,Mo,Zn,Mn)have generally increased, and a further group initially increased and then decreased (e.g.,SeandU). These changes appear to be controlled by many factors, in particular:1) oxygenation cycles of the Earth’s ocean–atmospheresystem, 2)the composition ofexposed crustalrocks,3)longtermrates of continental erosion,and4)cyclesofoceananoxia.WeshowthatNiandCocontentofseawaterisaffectedbyglobalLargeIgneousProvinceevents,whereasredoxsensitivetraceelementssuchasSeandMoareaffectedbyatmosphereoxygenation.PositivejumpsinMoandSeconcentrationspriortotheGreatOxidationEvent(GOE1,c.2500Ma)suggestpulsesofoxygenationmayhaveoccurredasearlyas2950Ma.AflattodecliningpatternofmanybiologicallyimportantnutrientelementsthroughthemidtolateProterozoicmayrelatetodecliningatmosphereO2,andsupportspreviousmodelsofnutrientdeficiencyinhibitingmarineevolutionduringthisperiod.Thesetraceelements(Mo,Se,U,CuandNi)reachaminimuminthemidCryogenianandriseabruptlytowardtheendoftheCryogenianmarkingthepositionofasecondGreatOxidationEvent(GOE2).
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The transition from jawless to jawed vertebrates (gnathostomes) resulted in the reconfiguration of the muscles and skeleton of the head, including the creation of a separate shoulder girdle with distinct neck muscles. We describe here... more
The transition from jawless to jawed vertebrates (gnathostomes) resulted in the reconfiguration of the muscles and skeleton of the head, including the creation of a separate shoulder girdle
with distinct neck muscles. We describe here the only known examples of preserved musculature from placoderms (extinct armored fishes), the phylogenetically most basal jawed vertebrates.
Placoderms possess a regionalized muscular anatomy that differs radically from the musculature of extant sharks, which is often viewed as primitive for gnathostomes. The placoderm data
suggest that neck musculature evolved together with a dermal joint between skull and shoulder girdle, not as part of a broadly flexible neck as in sharks, and that transverse abdominal muscles
are an innovation of gnathostomes rather than of tetrapods.
with distinct neck muscles. We describe here the only known examples of preserved musculature from placoderms (extinct armored fishes), the phylogenetically most basal jawed vertebrates.
Placoderms possess a regionalized muscular anatomy that differs radically from the musculature of extant sharks, which is often viewed as primitive for gnathostomes. The placoderm data
suggest that neck musculature evolved together with a dermal joint between skull and shoulder girdle, not as part of a broadly flexible neck as in sharks, and that transverse abdominal muscles
are an innovation of gnathostomes rather than of tetrapods.
Recent discoveries of advanced fish-like stem-tetrapods (for example, Panderichthys and Tiktaalik) have greatly improved our knowledge of the fin-to-limb transition. However, a paucity of fossil data from primitive finned tetrapods... more
Recent discoveries of advanced fish-like stem-tetrapods (for example, Panderichthys and Tiktaalik) have greatly improved our knowledge of the fin-to-limb transition. However, a paucity of fossil data from primitive finned tetrapods prevents profound understanding of the acquisition sequence of tetrapod characters. Here we report a new stem-tetrapod (Tungsenia paradoxa gen. et sp. nov.) from the Lower Devonian (Pragian, ~409 million years ago) of China, which extends the earliest record of tetrapods by some 10 million years. Sharing many primitive features with stem-lungfishes, the new taxon further fills in the morphological gap between tetrapods and lungfishes. The X-ray tomography study of the skull depicts the plesiomorphic condition of the brain in the tetrapods. The enlargement of the cerebral hemispheres and the possible presence of the pars tuberalis in this stem-tetrapod indicate that some important brain modifications related to terrestrial life had occurred at the beginning of the tetrapod evolution, much earlier than previously thought.
ABSTRACT.—The first articulated phyllolepid placoderm from North America (outside of Greenland) is described from the Upper Devonian Catskill Formation in north-central Pennsylvania. Phyllolepis rossimontina Lane and Cuffey 2005, from... more
ABSTRACT.—The first articulated phyllolepid placoderm from North America (outside of Greenland) is described from the
Upper Devonian Catskill Formation in north-central Pennsylvania. Phyllolepis rossimontina Lane and Cuffey 2005, from the
same formation, and the genus Phyllolepis are reviewed based on the new Catskill Formation material and data from a range
of recently described Southern Hemisphere taxa. Phyllolepids can be a valuable tool for biostratigraphic correlation due to
their narrow age range within the Famennian stage of the Late Devonian in the Euramerican Province (Northern Hemisphere).
Faunal exchange between Euramerica and Gondwana during the Late Devonian and the association of Phyllolepis with early
tetrapods are discussed in the context of early tetrapod biogeography.
Upper Devonian Catskill Formation in north-central Pennsylvania. Phyllolepis rossimontina Lane and Cuffey 2005, from the
same formation, and the genus Phyllolepis are reviewed based on the new Catskill Formation material and data from a range
of recently described Southern Hemisphere taxa. Phyllolepids can be a valuable tool for biostratigraphic correlation due to
their narrow age range within the Famennian stage of the Late Devonian in the Euramerican Province (Northern Hemisphere).
Faunal exchange between Euramerica and Gondwana during the Late Devonian and the association of Phyllolepis with early
tetrapods are discussed in the context of early tetrapod biogeography.
Intro: Since Charles Darwin published his seminal work On the Origin of Species by Means of Natural Selection (Darwin, 1859), museums around the globe have been greatly expanding their holdings of palaeontological collections, and it is... more
Intro: Since Charles Darwin published his seminal work On the Origin of Species by Means of Natural Selection (Darwin, 1859), museums around the globe have been greatly expanding their holdings of palaeontological collections, and it is estimated that they now hold several hundred million specimens (McNamara and Long, 2007). Most scholars today acknowledge that the little information gained from the few fossils known in Darwin’s day was almost superfluous in formulating his theory of evolution; it was largely icing on the cake to reinforce the work achieved by his lifetime studying both biology and geology (Bowler, 2009). Today, these vast collections of fossils continue to provide valuable data towards resolving many of the crucial stages in the transformational macroevolution of the major vertebrate groups, as well as greatly elucidating both the nature and tempo of evolutionary trends (McNamara, 1997; Gould, 2002). Fossils have also provided valuable reference points for testing the reliability of molecular divergence times for defining the timing of critical branching events in phylogenies (Kumar and Hedges, 1998; Hurley et al., 2009), as well as providing nodes in time for the hypothetical origins of certain kinds of physiological traits such as air-breathing (Long, 1993; Clement and Long, 2010), or reproductive behaviours such as copulation (Long et al., 2008, 2009).
ABSTRACT—A full description of a complete and articulated, three-dimensionally preserved, placoderm fish, Materpiscis attenboroughi (Ptyctodontida), from the Late Devonian Gogo Formation is presented. The jaw articulation is unique in... more
ABSTRACT—A full description of a complete and articulated, three-dimensionally preserved, placoderm fish, Materpiscis attenboroughi (Ptyctodontida), from the Late Devonian Gogo Formation is presented. The jaw articulation is unique in being preserved in situ, providing new morphological information on the articulation of the quadrate, metapterygoid, and labial skeleton. In addition, separate hyoid and opercular cartilages are identified, thus confirming their presence for the first time within placoderms. Preserved orbital ossifications indicate an anteriomesial orientation of this braincase region. The complete scapulocoracoid provides additional morphological information on the pectoral fin articulation. A new specimen of Austroptyctodus gardineri preserving the anterior portion of the head and jaws allows for revised descriptions of the endocranium and visceral skeleton, including the most complete endocranial ossifications recovered to date. As well, elements of the labial skeleton not known previously in ptyctodonts are preserved. Small amounts of soft tissues are recovered from Materpiscis, and extensive postcranial body muscle from Austroptyctodus. This new material resolves several questions regarding cranial and postcranial morphology of the Ptyctodontida. Moreover, similarities in placoderm and chondrichthyan pelvic fins and reproductive structures (claspers) suggest early parallel expression of HoxD and sonic hedgehog genes (shh), potentially representing the first evidence for expression of these genes in placoderms.
The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era1, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of... more
The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era1, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of their reproductive biology2, 3, 4, 5. Here we document the oldest record of a live-bearing vertebrate in a new ptyctodontid placoderm, Materpiscis attenboroughi gen. et sp. nov., from the Late Devonian Gogo Formation of Australia (approximately 380 million years ago)6. The new specimen, remarkably preserved in three dimensions, contains a single, intra-uterine embryo connected by a permineralized umbilical cord. An amorphous crystalline mass near the umbilical cord possibly represents the recrystallized yolk sac. Another ptyctodont from the Gogo Formation, Austroptyctodus gardineri7, also shows three small embryos inside it in the same position. Ptyctodontids have already provided the oldest definite evidence for vertebrate copulation8, and the new specimens confirm that some placoderms had a remarkably advanced reproductive biology, comparable to that of some modern sharks and rays. The new discovery points to internal fertilization and viviparity in vertebrates as originating earliest within placoderms.
Research Interests: Ancient History, Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology, and 59 moreGenetics, Marine Biology, Neuroscience, Environmental Science, Geology, Geophysics, Physics, Materials Science, Quantum Physics, Developmental Biology, Immunology, Climate Change, Molecular Biology, Structural Biology, Genomics, RNA, Computational Biology, Transcriptomics, Reproduction, Biotechnology, Systems Biology, Cancer, Australia, Paleoecology, Biology, Metabolomics, Cell Cycle, Proteomics, Ecology, Drug Discovery, Scanning Electron Microscopy, Evolution, Taphonomy, Nanotechnology, Vertebrate Evolution, Astrophysics, Vertebrate Paleontology, Neurobiology, Medicine, Multidisciplinary, Palaeobiology, Functional Genomics, Nature, Signal Transduction, Astronomy, DNA, Anatomy, Devonian, Fossils, Female, Animals, Fishes, Cell Signalling, Medical Research, Paleozoic, Biological evolution, Holotype, Embryos, and Earth Science
The transition from fishes to tetrapods was one of the most dramatic events in the evolution of vertebrates, but many pivotal fossils are incomplete, resulting in gaps in the data that are used for phylogenetic reconstruction. Here we... more
The transition from fishes to tetrapods was one of the most dramatic events in the evolution of vertebrates, but many pivotal fossils are incomplete, resulting in gaps in the data that are used for phylogenetic reconstruction. Here we present new observations from the most complete, acid-prepared Devonian tetrapodomorph fish yet discovered, Gogonasus1,2, which was previously placed just crownward of Kenichthys and rhizodontids3,4, the most primitive taxa on the tetrapod lineage. Unexpectedly, Gogonasus shows a mosaic of plesiomorphic and derived tetrapod-like features.Whereas the braincase and dermal cranial skeleton exhibit generalized morphologies with respect to Eusthenopteron5 or Panderichthys6, taxa that are traditionally considered to be phyletically close to tetrapods7,8, the presence of a deeply invaginated, wide spiracle, advanced internal spiracular architecture and nearhorizontal hyomandibula are specialized features that are absent from Eusthenopteron9. Furthermore, the pectoral fin skeleton of Gogonasus shares several features with that of Tiktaalik, the most tetrapod-like fish10. A new phylogenetic analysis places Gogonasus crownward of Eusthenopteron as the sister taxon to the Elpistostegalia. Aspects of the basic tetrapod limb skeleton and middle ear architecture can now be traced further back within the tetrapodomorph radiation.
Research Interests: Ancient History, Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology, and 55 moreGenetics, Marine Biology, Neuroscience, Environmental Science, Geophysics, Physics, Materials Science, Quantum Physics, Developmental Biology, Immunology, Radiation, Climate Change, Molecular Biology, Structural Biology, Genomics, RNA, Computational Biology, Transcriptomics, Biotechnology, Systems Biology, Cancer, Australia, Biology, Metabolomics, Cell Cycle, Proteomics, Ecology, Drug Discovery, Morphology, Evolution, Nanotechnology, Astrophysics, Neurobiology, Medicine, Multidisciplinary, Palaeobiology, Functional Genomics, Nature, Signal Transduction, Astronomy, DNA, Phylogeny, Anatomy, Devonian, Fossils, Animals, Skull, Fishes, Cell Signalling, Medical Research, Paleozoic, Time Factors, Skeletons, Earth Science, and Extremities
Recent finds1, 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... more
Recent finds1, 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 previously1 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.
Research Interests: Ancient History, Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology, and 61 moreGenetics, Marine Biology, Neuroscience, Environmental Science, Geology, Geophysics, Physics, Materials Science, Quantum Physics, Developmental Biology, Immunology, Climate Change, Molecular Biology, Structural Biology, Genomics, RNA, Computational Biology, Transcriptomics, Reproduction, Biotechnology, Systems Biology, Cancer, Paleoecology, Biology, Metabolomics, Cell Cycle, Proteomics, Ecology, Drug Discovery, Evolution, Taphonomy, Nanotechnology, Vertebrate Evolution, Interpretation, Astrophysics, Vertebrate Paleontology, Neurobiology, Medicine, Palaeontology, Multidisciplinary, Palaeobiology, Functional Genomics, Nature, Signal Transduction, Astronomy, Biological Sciences, DNA, Anatomy, Early Vertebrates, Devonian, Fossils, Female, Animals, Male, Fishes, Cell Signalling, Medical Research, Natural Sciences, Pelvis, Fertilization, and Earth Science
Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi1, an extinct class of armoured fish, indicating a viviparous mode of reproduction in a... more
Evidence of reproductive biology is extremely rare in the fossil record. Recently the first known embryos were discovered within the Placodermi1, 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 Arthrodira2, 3. Here we report the discovery of embryos in the Arthrodira inside specimens of Incisoscutum ritchiei from the Upper Devonian Gogo Formation of Western Australia4 (approximately 380 million years ago), providing the first evidence, to our knowledge, for reproduction using internal fertilization in this diverse 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 gnathostomes2, 3, 5, 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.
Research Interests: Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology, Genetics, and 61 moreMarine Biology, Neuroscience, Environmental Science, Geophysics, Physics, Materials Science, Quantum Physics, Developmental Biology, Immunology, Climate Change, Molecular Biology, Structural Biology, Genomics, RNA, Computational Biology, Transcriptomics, Reproduction, Biotechnology, Systems Biology, Cancer, Biology, Metabolomics, Cell Cycle, Proteomics, Ecology, Drug Discovery, Evolution, Taphonomy, Nanotechnology, Vertebrate Evolution, Astrophysics, Vertebrate Paleontology, Neurobiology, Medicine, Reproductive Biology, Multidisciplinary, Palaeobiology, Functional Genomics, Soft Tissue Preservation, Nature, Signal Transduction, Astronomy, DNA, Phylogeny, Fossil record, Early Vertebrate Palaeontology, Sharks, Devonian, Fossils, Animals, Fishes, Cell Signalling, Medical Research, Paleozoic, Biological evolution, Western Australia, Pelvis, Fertilization, Embryos, Earth Science, and Fertilisation
The tetrapodomorph fish Marsdenichthys longioccipitus from the Givetian-Frasnian of Mt. Howitt, Victoria, Australia, occupies an uncertain phylogenetic position. Marsdenichthys has been linked to the base of the Tristichopteridae, as well... more
The tetrapodomorph fish Marsdenichthys longioccipitus from the Givetian-Frasnian of Mt. Howitt, Victoria, Australia, occupies an uncertain phylogenetic position. Marsdenichthys has been linked to the base of the Tristichopteridae, as well as to the poorly known Northern Hemisphere form Rhizodopsis, based on the presence of rounded scales bearing a median boss on the internal surface. However, its affinities to these taxa are ambiguous, due to the incomplete preservation of the two Marsdenichthys specimens initially described. For the first time, we present significant information regarding the cheek and palate of Marsdenichthys, based on the descriptions of two new specimens from Mt. Howitt. New autapomorphies for Marsdenichthys are proposed, including the presence of a bar-like maxilla being approximately equal in depth to the dentary, and a rectangular anterior termination of the lacrimal. Several plesiomorphic features are described from the palate, including rounded vomer morphology lacking a posterior process, a relatively short, broad parasphenoid, and a dermopalatine approximately equal in length to the ectopterygoid. No synapomorphies are shared between Marsdenichthys and tristichopterids. Scale morphology is redescribed, and shown to exhibit concentric rings on the external surface, as in Rhizodopsis. However, differences in skull morphology, such as the lack of an external opening for the pineal foramen in Rhizodopsis, suggest that this scale morphology may have evolved independently.
In this paper, we show exceptional three-dimensionally preserved fossilized muscle tissues in 380–384 Myr old placoderm fish (Late Devonian), offering new morphological evidence supporting the hypothesis that placoderms are the sister... more
In this paper, we show exceptional three-dimensionally preserved fossilized muscle tissues in 380–384 Myr old placoderm fish (Late Devonian), offering new morphological evidence supporting the hypothesis that placoderms are the sister group to all other gnathostomes. We describe the oldest soft tissue discovered in gnathostomes, which includes striated muscle fibres, circulatory and nerve tissues, preserved as phosphatized structures precipitated by microbial infilling of small, protected areas under the headshield of the arthrodire, Eastmanosteus calliaspis. Muscle impressions have also been found in the ptyctodontid, Austroptyctodus gardineri. The specimens display primitive vertebrate muscle structures; in particular, shallow W-shaped muscle blocks such as those observed in lampreys. New information from fossilized soft tissues thus elucidates the affinities of the placoderms and provides new insights into the evolution and radiation of gnathostomes.
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A new acanthodiform acanthodian Halimacanthodes ahlbergi n. gen. n. sp., based on a single uncrushed, partial articulated specimen, represents the first acanthodian collected from the Gogo Formation, Canning Basin, Western Australia. The... more
A new acanthodiform acanthodian Halimacanthodes ahlbergi n. gen. n. sp., based on a single uncrushed, partial articulated specimen, represents the first acanthodian collected from the Gogo Formation, Canning Basin, Western Australia. The delicate perichondral ossifications of the lower jaws, branchial skeleton and endoskeletal shoulder girdle are preserved in 3D. H. ahlbergi n. gen. n. sp. is characterised by having a tall slender scapular shaft, paired pelvic fin spines, mineralised branchial arches and scales with an anterior median depression and a microornament of tiny smooth tubercles randomly
distributed on the crown. In having paired pelvic spines and lacking prepelvic spines, it is most closely related to Howittacanthus kentoni from Frasnian lacustrine deposits of eastern Victoria. Isolated scales, here attributed to the new taxon, are found in the coeval Gneudna Formation, Carnarvon Basin, Western Australia.
distributed on the crown. In having paired pelvic spines and lacking prepelvic spines, it is most closely related to Howittacanthus kentoni from Frasnian lacustrine deposits of eastern Victoria. Isolated scales, here attributed to the new taxon, are found in the coeval Gneudna Formation, Carnarvon Basin, Western Australia.
The Gogo Formation of Western Australia preserves a unique Late Devonian (Frasnian) reef fauna. The exceptional three-dimensional preservation of macrofossils combined with unprecedented soft-tissue preservation (including muscle bundles,... more
The Gogo Formation of Western Australia preserves a unique Late Devonian (Frasnian) reef fauna. The exceptional three-dimensional preservation of macrofossils combined with unprecedented soft-tissue preservation (including muscle bundles, nerve cells, and umbilical structures) has yielded a particularly rich assemblage with almost 50 species of fishes described. The most significant discoveries have contributed to resolving placoderm phylogeny and elucidating their reproductive physiology. Specifically, these discoveries have produced data on the oldest known vertebrate embryos; the anatomy of the primitive actinopterygian neurocranium and phylogeny of the earliest actinopterygians; the histology, radiation, and plasticity of dipnoan (lungfish) dental and cranial structures; the anatomy and functional morphology of the extinct onychodonts; and the anatomy of the primitive tetrapodomorph head and pectoral fin.
Research Interests:
ABSTRACT—A new holodontid lungfish, Xeradipterus hatcheri, gen. et sp. nov., is described from the Late Devonian (Frasnian) Gogo Formation, Western Australia. The material comprises a single specimen preserved in a large concretion,... more
ABSTRACT—A new holodontid lungfish, Xeradipterus hatcheri, gen. et sp. nov., is described from the Late Devonian (Frasnian) Gogo Formation, Western Australia. The material comprises a single specimen preserved in a large concretion, represented by elements of the skull roof, cheek, lower jaw, palate, shoulder girdle, and parts of the postcranial skeleton. Xeradipterus, gen. nov., differs from other holodontids by its broad crushing dentition, prearticular tooth plates with pronounced heel, lack of prominent teeth, and ordered tooth rows, and by its parasphenoid morphology. Results of PAUP
analyses of 82 characters for 33 dipnoan taxa revealed that the new genus is a member of the Holodontidae, suggesting a possible endemic radiation of holodontids within the Gogo fauna. In addition, new “Holodipterus” elderae material examined shows the shape and extent of the nasal capsules, and the presence of an anterior median callus for the first time.
analyses of 82 characters for 33 dipnoan taxa revealed that the new genus is a member of the Holodontidae, suggesting a possible endemic radiation of holodontids within the Gogo fauna. In addition, new “Holodipterus” elderae material examined shows the shape and extent of the nasal capsules, and the presence of an anterior median callus for the first time.
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A new basal actinopterygian,Gogosardina coatesi gen. et sp. nov., is described from the Upper Devonian Gogo Formation of the Canning Basin, Western Australia. The new taxon is known from four prepared specimens that display the typical... more
A new basal actinopterygian,Gogosardina coatesi gen. et sp. nov., is described from the Upper Devonian Gogo Formation of the Canning Basin, Western Australia. The new taxon is known from four prepared specimens that display the typical exceptional preservation of fossil vertebrates from the region. Gogosardina gen. nov. possesses a series of four small postrostrals, no surangular and a highly gracile body covered with over 140 vertical rows of very small scales, all ornamented with separate horizontal ganoine ridges. One specimen contains conodont elements lodged among the branchial arches, indicating dietary habits and a possible cause of death.
New specimens of holodontid lungfishes from the Upper Devonian (Frasnian) Gogo Formation of Western Australia allows further description of the anatomy and taxonomic clarification of two poorly known taxa. Robinsondipterus longi n. gen.... more
New specimens of holodontid lungfishes from the Upper Devonian (Frasnian) Gogo Formation of Western Australia allows further description of the anatomy and taxonomic clarification of two poorly known taxa. Robinsondipterus longi n. gen. is erected for Holodipterus longi CAMPBELL & BARWICK 1991 based on the holotype plus 2 new skulls showing that the holotype was a juvenile specimen. The adult form has a skull length close to 20 cm. It is characterised by having an elongate mandible with a symphysial length of 30% jaw length, a palatal dentition primarily consisting of denticles with only marginal teeth of coalesced tuberosities developed, featuring two prominent tusks midway along the pterygoid margin, as seen in Griphognathus. Asthenorhynchus meemannae gen.nov. is elevated to generic level for Holodipterus ‘Asthenorhynchus’ meemannae PRIDMORE et al. 1994, distinguished from the genus Holodipterus by having paired dentaries in the lower jaw, separated pterygoid tooth plates that fuse at maturity. Robinsondipterus n. gen, in having an elongated snout, large labial pouch and marginal dentition, is here shown by phylogenetic analysis to be the sister taxon to Griphognathus whitei.
How well the ecology, zoogeography and evolution of modern biotas is understood depends substantially on knowledge of the Pleistocene1, 2. Australia has one of the most distinctive, but least understood, Pleistocene faunas. Records from... more
How well the ecology, zoogeography and evolution of modern biotas is understood depends substantially on knowledge of the Pleistocene1, 2. Australia has one of the most distinctive, but least understood, Pleistocene faunas. Records from the western half of the continent are especially rare3. Here we report on a diverse and exceptionally well preserved middle Pleistocene vertebrate assemblage from caves beneath the arid, treeless Nullarbor plain of south-central Australia. Many taxa are represented by whole skeletons, which together serve as a template for identifying fragmentary, hitherto indeterminate, remains collected previously from Pleistocene sites across southern Australia. A remarkable eight of the 23 Nullarbor kangaroos are new, including two tree-kangaroos. The diverse herbivore assemblage implies substantially greater floristic diversity than that of the modern shrub steppe, but all other faunal and stable-isotope data indicate that the climate was very similar to today. Because the 21 Nullarbor species that did not survive the Pleistocene were well adapted to dry conditions, climate change (specifically, increased aridity) is unlikely to have been significant in their extinction.
Research Interests: Ancient History, Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology, and 66 moreGenetics, Marine Biology, Neuroscience, Geography, Environmental Science, Geophysics, Physics, Materials Science, Quantum Physics, Developmental Biology, Immunology, Climate Change, Molecular Biology, Structural Biology, Genomics, RNA, Computational Biology, Transcriptomics, Biotechnology, Systems Biology, Adaptation, Cancer, Australia, Biology, Metabolomics, Stable Isotopes, Cell Cycle, Proteomics, Ecology, Drug Discovery, Evolution, Nanotechnology, Biodiversity, Astrophysics, Paleoclimate, Neurobiology, Medicine, Multidisciplinary, Palaeobiology, Pleistocene, Functional Genomics, Nature, Quaternary, Signal Transduction, Astronomy, DNA, Flora, Carbon Isotopes, Fossils, Stable Isotope, Animals, Fauna, Cell Signalling, Medical Research, Cenozoic, Species Diversity, Skeleton, Rainfall, Phanerozoic, Oxygen Isotopes, Aridity, Macropodidae, Steppes, Time Factors, Steppe, and Earth Science
New observations on the axial skeleton of the extant lungfish Neoceratodus forsteri (Dipnoi; Sarcopterygii) indicate that neural and haemal arch elements develop more independently than previously believed. For example, while the... more
New observations on the axial skeleton of the extant lungfish Neoceratodus forsteri (Dipnoi; Sarcopterygii) indicate that neural and haemal arch elements develop more independently than previously believed. For example, while the cartilaginous neural arches/spines begin development anteriorly, just behind the skull, the distal supraneurals first form separately in the posterior region of the axial skeleton. Proximal supraneurals develop subsequently, but initially lack clear association with either neural arches/spines or distal supraneurals. This contradicts previous studies of Neoceratodus and other extant lungfish suggesting that the supraneurals and more distal radials develop from a single cartilage. This was suggested as a unique sarcopterygian pattern, but our new observations suggest a closer resemblance to the actinopterygian condition. With respect to the caudal fin skeleton, the heterocercal tail of Devonian lungfish is replaced in Carboniferous and younger taxa by a diphycercal tail, comprising elongate and equal dorsal and ventral lobes. Whether these lobes resulted from fusion of dorsal/anal and caudal fins or expansion of dorsal and anal fin rays at the expense of the caudal fin is uncertain. However, comparing ontogenetic development of Neoceratodus with Devonian taxa indicates that the elements of the ventral diphycercal lobe in Neoceratodus are homologous to haemal elements present in the caudal fin of Devonian forms, but loss of supporting basal plates in the dorsal fins of Devonian taxa allowed supraneural elements of the dorsal fin to expand to form the dorsal lobe of the Neoceratodus tail.
Recent discoveries of previously unknown fossil forms have dramatically transformed understanding of many aspects of the fish-tetrapod transition. Newer paleobiological approaches have also contributed to changed views of which animals... more
Recent discoveries of previously unknown fossil forms have dramatically transformed understanding of many aspects of the fish-tetrapod transition. Newer paleobiological approaches have also contributed to changed views of which animals were involved and when, where, and how the transition occurred. This review summarizes major advances made and reevaluates alternative interpretations of important parts of the evidence.We begin with general issues and concepts, including limitations of the Paleozoic fossil record.We summarize important features of paleoclimates, paleo- environments, paleobiogeography, and taphonomy. We then review the history of Devonian tetrapods and their closest stem group ancestors within the sarcopterygian fishes. It is now widely accepted that the first tetrapods arose from advanced tetrapodomorph stock (the elpistostegalids) in the Late Devonian, probably in Euramerica. However, truly terrestrial forms did not emerge until much later, in geographically far-flung regions, in the Lower Carboniferous. The complete transition occurred over about 25 million years; definitive emergences onto land took place during the most recent 5 million years. The sequence of character acquisition during the transition can be seen as a five-step process involving: (1) higher osteichthyan (tetrapodomorph) diversification in the Middle Devonian (beginning about 380 million years ago [mya]), (2) the emergence of “prototetrapods” (e.g., Elginerpeton) in the Frasnian stage (about 372 mya), (3) the appearance of aquatic tetrapods (e.g., Acanthostega) sometime in the early to mid- Famennian (about 360 mya), (4) the appearance of “eutetrapods” (e.g., Tulerpeton) at the very end of the Devonian period (about 358 mya), and (5) the first truly terrestrial tetrapods (e.g., Pederpes) in the Lower Carboniferous (about 340 mya). We discuss each of these steps with respect to inferred functional utility of acquired character sets. Dissociated heterochrony is seen as the most likely process for the evolutionarily
rapid morphological transformations required. Developmental biological processes, including paedomorphosis, played important roles. We conclude with a discussion of phylogenetic interpretations of the evidence.
rapid morphological transformations required. Developmental biological processes, including paedomorphosis, played important roles. We conclude with a discussion of phylogenetic interpretations of the evidence.
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The ischnacanthid acanthodian Grenfellacanthus zerinae gen. et sp. nov. is described on the basis of two large jaw bones from the Late Devonian (late Famennian) Hunter Formation, near Grenfell, NSW The new species is the youngest known... more
The ischnacanthid acanthodian Grenfellacanthus zerinae gen. et sp. nov. is described on the basis of two large jaw bones from the Late Devonian (late Famennian) Hunter Formation, near Grenfell, NSW The new species is the youngest known ischnacanthid, and the largest ischnacanthid from Gondwana. As for many ischnacanthids, the structure of the jaws and teeth indicate that Grenfellacanthus was probably an ambush predator.
Livre: Fossil Mammals of Australian and New Guinea: One Hundred Million Years of Evolution LONG John A., ARCHER Michael, FLANNERY Tim.
Selenium (Se) is one of the key trace elements required by all animal and most plant life, and Se deficiencies in the food chain cause pathologies or death. Here we show from new geochemical analyses of trace elements in Phanerozoic... more
Selenium (Se) is one of the key trace elements required by all animal and most plant life, and Se deficiencies in the food chain cause pathologies or death. Here we show from new geochemical analyses of trace elements in Phanerozoic marine pyrite that sustained periods of severe Se depletion in the past oceans correlate closely with three major mass extinction events, at the end of the Ordovician, Devonian and Triassic periods. These represent periods of Se depletion >1.5-2 orders of magnitude lower than current ocean abundances, being within the range to cause severe pathological damage in extant Se-reliant organisms. Se depletion may have been one of several factors in these complex extinction scenarios. Recovery from the depletion/extinction events is likely part of a natural marine cycle, although rapid rises in global oxygen from sudden major increases in marine productivity and plant biomass after each extinction event may also have played a crucial role.