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Discoveries from the Late Devonian Gogo Formation, in the Canning Basin, Western Australia have provided insights into the origin and evolution of many unique gnathostome features such as the origins of teeth, internal fertilisation, air-breathing, transitional tissues between bone and cartilage, and insights into the fin to limb transition. Although vertebrate studies have dominated evolutionary work, invertebrate studies have added important insights into the palaeoecology of the site and demonstrated close faunal affinities along the margins of northern Gondwana and China. Geochemical analyses have broadened the understanding of the pathways involved in the exceptional preservation of this Devonian Konservat-Lagerstatte. Fossils from the Gogo Formation show extensive soft tissue preservation through phosphatization recording anatomical details not normally obtained from fossil sites.

The tetrapodomorph fish, Gogonasus andrewsae is a three dimensionally well-preserved sarcopterygian from the Gogo Formation (Frasnian, early Upper Devonian, ∼380 million years ago) in Western Australia. High-resolution X-ray Micro-Computed Tomography and 3D printouts were used to obtain a digital reconstruction of its shoulder girdle and opercular series. Our new findings show the opercular series in a close fit against the upper bones of the shoulder girdle only if the anocleithrum, supracleithrum and post-temporal are aligned more horizontally than in previous reconstructions. The lowermost subopercular bone also differs, in partly covering the clavicle of the shoulder girdle. The ascending process of the clavicle, and the ventral process of the anocleithrum, do not fit closely inside the cleithrum, and perhaps functioned for ligamentous attachment. A rugose area on the anocleithral process is in a similar relative position to the attachment of a muscle ligament on the shoulder girdle of various living actinopterygians. Our manipulation of 3D printouts permits testing of the morphological fit of extremely fragile acid-etched bones, and indicates a new way to investigate the constructional morphology of one or more mechanical units of the vertebrate skeleton. It is suggested that Micro-CT imaging, reconstruction, visualisation and 3D printing techniques will provide a rigorous new test leading to modification of previous reconstructions of extinct vertebrates that were based on graphical methods and 2D imaging.

The study of early actinopterygians (ray-finned fishes) from the Devonian has been hampered by imperfect preservation in the majority of taxa. The Late Devonian (early Frasnian) Gogo Formation of north-western Western Australia is notable in producing complete fossil actinopterygians with exceptional three-dimensional preservation of both the dermal and endoskeletal anatomy. Four taxa have been described and have proved invaluable in understanding the anatomy of early representatives of this clade. Here, we present a fifth Gogo taxon, based on a single exceptionally preserved specimen and representing a new genus and species of early ray-finned fish. The neurocranium was CT scanned, permitting a detailed examination of the endocast. The new taxon possesses unusual features including a greatly enlarged spiracular opening and extensive spinose ornamentation on the dermal skull bones, median ridge scutes and lepidotrichia. The endocast displays a mosaic of characters, some of which are similar to Mimipiscis and non-actinopterygian outgroups, while other features are more akin to Raynerius from the Late Devonian of France as well as several stratigraphically younger taxa. A phylogenetic analysis resolves the new form as sister taxon to fishes from the Late Devonian of the Northern Hemisphere and all post-Devonian actinopterygians, confirming that the assemblage of fossil ray fins from the Gogo Formation is part of the wider Devonian actinopterygian radiation .

The mudstones of the Western Australian Gogo Formation harbour numerous carbonate concretions which often contain preserved fossils of Lagerstätte-like quality. These are especially notable in places where the mudstone has eroded, giving way to nodule fields, which afford valuable paleobiological records. It is, however, a challenge to determine their paleoenvironmental context. Here, we analysed concretions from a core drilled in the Canning Basin Gogo Formation. At two different depths, concretions were compared to the surrounding mudstone found at the same depth. Electron microscopy and X-ray spectroscopy showed that the concretions were carbonate-rich and contained detrital fragments. Biomarker data showed that mudstone and concretions had very similar distributions and presented marine biosignatures including indicators of anoxic depositional conditions, a stratified water column, and photic zone euxinia. The concretions contained higher amounts of C27 steranes, indicating that more labile organic matter such as animal remains could have triggered concretion formation. Statistical analyses of the results showed that concretions and shales differed (p < 0.1) in indices diagnostic for lithologies (and often related to maturity), particularly in the sample recovered from the younger section of the core: the diasterane/sterane indices at each of the depths were 0.34 in the shale vs 0.12 in the concretion in the younger set of samples, and 0.21 vs 0.19 in the older set. The homohopane isomerisation indices of the mudstone and concretion were 0.66 vs 0.58 and 0.62 vs 0.60 (47 and 54 m depth, respectively). Furthermore, shales contained higher relative amounts of moretanes. Concretions also differed from the mudstone in their methylhopane distributions, with shales showing higher amounts of 3-methylhopanes. Conversely, when biomarker composition was compared at the two depths, they only differed significantly (p < 0.1) in the 2-methylhopane index,%C31 homohopanes, and hopane/sterane ratios (p < 0.1). Our results show that the biomarker composition of the mudstone at the time of deposition is largely preserved in the concretions with only a minor overprint from diagenesis, bacterial communities involved in concretion formation, or the organic matter nucleus. It is therefore possible to use biomarker analysis on carbonate concretions to determine their provenance if found outside their immediate geological context., NASA Astrobiology Institute (Award NNA13AA90A)

Significant new material of Late Devonian Gogo Formation fish fossils is still surfacing. Collecting in the past decade has uncovered the first Gogo shark fossils (Gogoselachusplus another new undescribed taxon), the first acanthodian (Halmacanthodes ahlbergi), the first coelacanth, as well as the first placoderm embryos. Recent studies have elucidated the nature of placoderm claspers, pelvic girdles, synarcuals and embryos, the structure of their teeth, a description of well-preserved muscles in placoderms, and how muscles attach to bones. Molecular biomarkers have also been identified in Gogo fossils. There are now five basal ray-fin fishes in the fauna, including one undescribed new taxon. The lungfish fauna from Gogo is the most diverse known for any Devonian site, with 10 genera and 12 species. The dermal skeleton and endocast of the dipteridRhinodipterus kimberleyensishave been described in detail from CT scans; and the ontogenetic stages of neurocranium formation inGriphognathus. New specimens of the tetrapodomorph fishGogonasus andrewsaehave shed further light on its endocranium, pectoral girdle and fin. Through their exceptional preservation of both hard and varied kinds of soft tissues, the Gogo fishes remain crucial for resolving key debates on the diversification, physiology, biomechanics and phylogenetic relationships of early gnathostomes.

The lowermost Famennian deposits of the Kowala quarry (Holy Cross Mountains, Poland) are becoming famous for their rich fossil content such as their abundant phosphatized arthropod remains (mostly thylacocephalans). Here, for the first time, palaeontological and geochemical data were integrated to document abundance and diversity patterns in the context of palaeoenvironmental changes. During deposition, the generally oxic to suboxic conditions were interrupted at least twice by the onset of photic zone euxinia (PZE). Previously, PZE was considered as essential in preserving phosphatised fossils from, e.g., the famous Gogo Formation, Australia. Here, we show, however, that during PZE, the abundance of arthropods drastically dropped. The phosphorous content during PZE was also very low in comparison to that from oxic-suboxic intervals where arthropods are the most abundant. As phosphorous is essential for phosphatisation but also tends to flux off the sediment during bottom water anoxia, we propose that the PZE in such a case does not promote the fossilisation of the arthropods but instead leads to their impoverishment and non-preservation. Thus, the PZE conditions with anoxic bottom waters cannot be presumed as universal for exceptional fossil preservation by phosphatisation, and caution must be paid when interpreting the fossil abundance on the background of redox conditions.

One of the first endocasts of a dipnoan (lungfish) to be realised was that of the Upper Devonian taxon Chirodipterus australis. This early interpretation was based on observations of the shape of the cranial cavity alone and was not based on a natural cast or ‘steinkern’ nor from serial sectioning. The validity of this reconstruction is therefore questionable and continued reference to and use of this interpretation in analyses of sarcopterygian cranial evolution runs the risk of propagation of error. Here we present a new detailed anatomical description of the endocast of ‘Chirodipterus’ australis from the Upper Devonian Gogo Formation of Western Australia, known for exceptional 3D preservation which enables fine-scale scrutiny of endocranial anatomy. We show that it exhibits a suite of characters more typical of Lower and Middle Devonian dipnoan taxa. Notably, the small utricular recess is unexpected for a taxon of this age, whereas the ventral expansion of the telencephalon is more typical of more derived taxa. The presence of such ’primitive’ characters in ‘C.’ australis supports its relatively basal position as demonstrated in the most recent phylogenies of Devonian Dipnoi.

As the sister lineage of all other actinopterygians, the Middle to Late Devonian (Eifelian-Frasnian) Cheirolepis occupies a pivotal position in vertebrate phylogeny. Although the dermal skeleton of this taxon has been exhaustively described, very little of its endoskeleton is known, leaving questions of neurocranial and fin evolution in early ray-finned fishes unresolved. The model for early actinopterygian anatomy has instead been based largely on the Late Devonian (Frasnian) Mimipiscis, preserved in stunning detail from the Gogo Formation of Australia. Here, we present re-examinations of existing museum specimens through the use of high-resolution laboratory- and synchrotron-based computed tomography scanning, revealing new details of the neuro-cranium, hyomandibula and pectoral fin endoskeleton for the Eifelian Cheirolepis trailli. These new data highlight traits considered uncharacteristic of early actinopterygians, including an uninvested dorsal aorta and imperforate propterygium, and corroborate the early divergence of Cheirolepis within actinopterygian phylogeny. These traits represent conspicuous differences between the endoskeletal structure of Cheirolepis and Mimipiscis. Additionally, we describe new aspects of the parasphenoid, vomer and scales, most notably that the scales display peg-and-socket articulation and a distinct neck. Collectively, these new data help clarify primitive conditions within ray-finned fishes, which in turn have important implications for understanding features likely present in the last common ancestor of living osteichthyans.

Micro computed tomography has revealed as yet undescribed internal braincase anatomy of the tetrapodomorph fishGogonasus andrewsaefrom the Frasnian Gogo Formation, Paddy's Valley, Kimberley Region, Western Australia. The complete material, including the cranial cavities and channels for blood vessels and nerves, reveals several notable features inside the endocranium. The ethmosphenoid unit includes a median capsule, which lies underneath the median postrostral and rostral series. Based on innervation and association with cutaneous vessels, potential electroreceptive function is inferred for this capsule. Several regions of poor ossification, including foramina for the glossopharyngeal and abducens nerves, as well as the apparent suture separating the ethmoid from the sphenoid portions of the braincase, are possibly indicative of early ontogenetic features. Former interpretations of the course for the superficial ophthalmic nerve inside the nasal capsule ofOsteolepisandGyroptychiusmay be incorrect, with new research supporting a path through the nasal septum, as inGogonasus.

Photic zone euxinia (PZE) has proven important for elucidating biogeochemical changes that occur during oceanic anoxic events, including mass extinction and conditions associated with unique fossil preservation. Organic geochemical analyses of a 380 Ma invertebrate fossil, which included well-preserved soft tissues, from the Gogo Formation (Canning Basin, Western Australia) showed biomarkers and stable isotopic values characteristic of PZE and a consortium of sulfate-reducing bacteria, which lead to exceptional fossil and biomarker preservation. The carbonate concretion contained phytoplankton, green sulfur bacteria (Chlorobi), and sulfate-reducing bacteria biomarkers with an increasing concentration toward the nucleus where the fossil is preserved. The spatial distribution of cholestane unequivocally associated with the fossilized tissue and its high relative abundance to the total steranes suggest that the fossil is a crustacean. The presence of an active sulfur cycle in this Devonian system, including sulfate reduction and the resulting PZE, played a pivotal role in the preservation of soft tissue from the fossil and its associated low-maturity biomarker ratios.

Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited., Lungfish first appeared in the geological record over 410 million years ago and are the closest living group of fish to the tetrapods. Palaeoneurological investigations into the group show that unlike numerous other fishes—but more similar to those in tetrapods—lungfish appear to have had a close fit between the brain and the cranial cavity that housed it. As such, researchers can use the endocast of fossil taxa (an internal cast of the cranial cavity) both as a source of morphological data but also to aid in developing functional and phylogenetic implications about the group. Using fossil endocast data from a three-dimensional-preserved Late Devonian lungfish from the Gogo Formation, Rhinodipterus, and the brain-neurocranial relationship in the extant Australian lungfish, Neoceratodus, we herein present the first virtually reconstructed brain of a fossil lungfish. Computed tomographic data and a newly developed ‘brain-warping’ method are used in conjunction with our own distance map software tool to both analyse and present the data. The brain reconstruction is adequate, but we envisage that its accuracy and wider application in other taxonomic groups will grow with increasing availability of tomographic datasets.

Recently discovered material has yielded new information on the pectoral girdle and fin endoskeleton of Gogonasusandrewsae (Frasnian Gogo Formation, Kimberley Region, Western Australia). These elements permit the first comprehensive description of the anocleithrum, cleithrum, scapulocoracoid, and lepidotrichia. New autapomorphies of Gogonasus include a square exposed region on the supracleithrum, an unusual knob-like process on the scapulocoracoid, a relatively small entepicondyle, and lepidotrichia with I-beam-shaped cross sections. Several poorly ossified regions on the scapulocoracoid and humerus indicate an early ontogenetic state, as with other immature tetrapodomorph fish specimens. A phylogenetic analysis indicates a more stemward position for Gogonasus in a weakly supported clade with other “osteolepidid” taxa, compared to other recent studies placing Gogonasus crownward of osteolepidid fishes and the Tristichopteridae, as the sister taxon to the “Elpistosteglia” + Tetrapoda. A phylogenetic position among megalichthyid fishes is suggested for Sterropterygion, while radiographs of the megalichthyid Cladarosymblema show a scythe-like radius terminating distally with that of the intermedium. New data on the scapulocoracoid of the rhizodontid Barameda reveals a coroacoid crest and small supraglenoid foramen. J. Morphol. 2013. © 2012 Wiley Periodicals, Inc.

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 previousl...

The Devonian actinopterygian Mimia Gardiner & Bartram (1977) of the Upper Devonian (Frasnian) Gogo Formation of Western Australia, one of the most completely known of all Palaeozoic ray-finned fishes, is renamed Mimipiscis nom. nov. due to preoccupation of the former genus by the butterfly Mimia Evans (1953). Recently acquired data, including the description of newly prepared fossil material, has revealed the presence of a second species in this formerly monotypic genus, as well as previously unreported features of the tail, parasphenoid and ontogenetic variability of type species, Mimipiscis toombsi (Gardiner & Bartram 1977). The second form, Mimipiscis bartrami sp. nov., differs from the contemporary M. toombsi in details of the body shape, squamation, snout, suboperculum and parasphenoid. Phylogenetic analyses recover Mimipiscis and Gogosardina as sister genera within a monophyletic Mimiidae, a clade restricted to the Late Devonian of Western Australia.

A new species of the Late Devonian lungfish Rhinodipterus is described from the Frasnian Gogo Formation, northern Western Australia. The description is based on a single specimen preserved in a small concretion, represented by elements of the skull roof, lower jaw, palate, neurocranium, hyoid arch, pectoral girdle and other parts of the postcranial skeleton. Rhinodipterus kimberleyensis sp. nov. differs from other species in the shape of its parasphenoid, number of tooth rows, nature of the tooth plates and characteristics of the skull roof. Functional morphology suggests Rhinodipterus kimberleyensis sp. nov. had a weak bite and may have fed off the reef substrate. Rhinodipterus kimberleyensis sp. nov. possessed a suite of skeletal characters that suggest it may have breathed air. Morphological comparison and a cladistic analysis place Rhinodipterus crown-ward of all other Gogo lungfishes and closely related to Oervigia, Andreyevichthys and Orlovichthys. Faunal comparisons between Australia and Laurussia indicate palaeobiogeographical links existed between these landmasses during the Middle to Late Devonian.

Phyllocarids (Crustacea: Malacostraca) from the Upper Devonian (Givetian-Frasnian) Gogo Formation of Western Australia are described and two new species are reconstructed. The mineralized exoskeleton is well preserved in concretions, but the appendages, apart from the mandible, are unknown. Montecaris gogoensis sp. nov. (Echinocarididae) is represented by >600 specimens; a possible second species of Montecaris is represented only by ∼14 specimens of antero-dorsal fragments of the valves, which are highly tuberculate. Schugurocaris wami sp. nov. (Ceratiocarididae) is represented by >300 specimens; a possible second species with a very elongate telson is represented by four specimens. An undetermined species of Dithyrocaris (Dithyrocarididae) is represented by >80 specimens.

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.

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.

Recent discoveries of tetrapod trackways in 395 Myr old tidal zone deposits of Poland (Niedźwiedzki et al . 2010 Nature 463 , 43–48 ( doi:10.1038/nature.08623 )) indicate that vertebrates had already ventured out of the water and might already have developed some air-breathing capacity by the Middle Devonian. Air-breathing in lungfishes is not considered to be a shared specialization with tetrapods, but evolved independently. Air-breathing in lungfishes has been postulated as starting in Middle Devonian times ( ca 385 Ma) in freshwater habitats, based on a set of skeletal characters involved in air-breathing in extant lungfishes. New discoveries described herein of the lungfish Rhinodipterus from marine limestones of Australia identifies the node in dipnoan phylogeny where air-breathing begins, and confirms that lungfishes living in marine habitats had also developed specializations to breathe air by the start of the Late Devonian ( ca 375 Ma). While invasion of freshwater habitats from the marine realm was previously suggested to be the prime cause of aerial respiration developing in lungfishes, we believe that global decline in oxygen levels during the Middle Devonian combined with higher metabolic costs is a more likely driver of air-breathing ability, which developed in both marine and freshwater lungfishes and tetrapodomorph fishes such as Gogonasus .

Intraspecies variation, polymorphism and asymmetric traits are observed within two families of Arthrodira, the Incisoscutidae and Camuropiscidae, from the Gogo Formation in northern Western Australia. Individual plates of the head and trunk shield show considerable variation between individuals. Plates that show the greatest degree polymorphic traits are the rostral (R), marginal (M), submarginal (SM), preorbital (PrO), anterior dorsolateral, anterior median ventral (AMV) and posterior ventrolateral (PVL) plates. The paths of the sensory line canals are the most variable feature and the dermal plates of the cheek show the greatest asymmetry. It is apparent that if anatomical data in arthrodires are to be interpreted with greater precision, detailed knowledge of intraspecies variation, polymorphic and asymmetric traits is essential. How these variables are treated in cladistic analysis is also critical. Here multistate characters were coded differently in five discrete analyses, each analysis yielding a different number of trees and relationships. It was concluded that including and coding for multistate characters gave the most robust tree. In addition, further morphological characters from a new specimen of Gogosteus sarahae Long (1994) indicates many of the characters used to separate this genus from Incisoscutum are inconsistent and so it is here considered that the genus Gogosteus is a junior synonym of Incisoscutum.

Within the Tetrapodomorpha, the Late Devonian Gogonasus andrewsae of the Gogo Formation, Gogo, Western Australia, has occupied an uncertain phylogenetic position. Following the description of several well-preserved three-dimensional skulls and pectoral girdles, the discovery of the first complete specimen (NMV P221807) made Gogonasus one of the best-known tetrapodomorph fish. Recent studies of pectoral fin structure and the spiracular opening of Gogonasus have suggested an unexpected affinity with ‘elpistostegalid’ fish such as Tiktaalik. Subsequent work has refuted characters linking these taxa, with phylogenetic analysis of the Tetrapodomorpha placing Gogonasus basal to megalichthyids and tristichopterids. In this paper we reanalyse characters linking Gogonasus with ‘elpistostegalid’ fish and those supporting the placement of Gogonasus crownward of Eusthenopteron. New phylogenetic analyses of the Tetrapodomorpha show a revised phylogenetic position of Gogonasus as being deeply nested within the Tetrapodomorpha, crownward of Osteolepis and Megalichthys, but basal to Eusthenopteron+‘elpistostegalids’. Functional consideration of the spiracular structure suggests a position of Gogonasus closer to ‘elpistostegalids’, although data is lacking from other less-well-preserved taxa to fully test the hypothesis. The humerus of the Late Devonian lungfish Chirodipterus from Gogo, Western Australia is figured for comparative purposes.

Studies of ecological structure and diversity over time in extinct groups have always been challenged by the inability to observe the behavior of fossil taxa directly. The only available evidence for function, behavior, and interactions between taxa is the morphological characteristics of the preserved fossils. Recent studies on modern groups have shown that morphological analyses may give misleading results in terms of ecological pattern and diversity. An alternative approach is to focus on functionally relevant aspects of morphology through a paleobiomechanical paradigm. The purpose of this research is to examine variation in the lower jaw morphology in Late Devonian arthrodire placoderms and develop biomechanical metrics that can be used to quantify functional diversity among this fossil group. Nine functionally relevant morphological characters were collected for 94 isolated arthrodire inferognathals from the Gogo Formation in Western Australia and the Cleveland Shale in Ohio. These data were used to address aspects of functional morphology, biomechanical disparity, and ecological structure in arthrodire placoderms from the Late Devonian. Results were compared with results from previous morphometric work on the same set of jaws.Statistical tests show a significant difference in functional characters between the two faunas. The differences may be related to phylogenetic differences between faunas, as the two major clades of arthrodire taxa included in this study are almost completely segregated between faunas. Average pairwise disparity analyses of the mechanical characters indicate that there is no significant difference in overall functional diversity between the Cleveland Shale and Gogo Reef arthrodire faunas. This result is at odds with previous results that show overall morphological disparity to be much higher in the Cleveland Shale. Clustering patterns within a multivariate function-space show tightly constrained functional groups of taxa independent of phylogenetic or shape-based morphological similarity. These functional groups illustrate a level of ecological diversity in Late Devonian arthrodires that is comparable to that in certain modern faunas.Further statistical analysis of the morphological and functional disparity of these Late Devonian taxa shows a disjoint between the two measures. Model I regression analysis of and Spearman rank-correlation analysis of average pairwise morphological and functional disparity measures indicate no significant relationship between morphological and functional disparity among the jaws used in this study. Although function is obviously derived from morphology, these results show that morphological shape analysis is not necessarily a good proxy for eco-functional diversity.

Examining morphological patterns is key to understanding mechanics and function in biological systems. In extinct taxa, there is a lack of observational or behavioral data to use to understand function, and groups without descendants limit the use of modern homologues. The only available evidence for function is the morphological characteristics of the preserved fossils. The purpose of this research is to analyze the functional consequences of variation in the lower jaw morphology in Late Devonian arthrodire placoderms. Landmark-based morphometric data were collected for 94 isolated arthrodire inferognathals (lower jaws) from the Gogo Formation in Western Australia and the Cleveland Shale in Ohio. These data were used to define the morphological differences and variation between two phylogenetically distinct morphotypes. Statistical results indicate fundamental shape differences between the two arthrodire morphotypes (coccosteomorphs and pachyosteomorphs). Differences in the shape of the blade po...

A new basal actinopterygian fish, Donnrosenia schaefferi gen. et sp. nov., is described from the Middle Devonian (Givetian) Aztec Siltstone of southern Victoria Land, Antarctica. Donnrosenia gen. nov. is characterized by the large parietals which are of almost equivalent size to the frontals, very small intertemporals, a small accessory operculum situated dorsally to the prominent anterodorsal process of the suboperculum, a deep dentary with anterior flexure, porous ornamentation on the clavicle, an elongate body form with macromeric squamation, an absence of paired fringing fulcra on the fins, and pectoral lepidotrichia which are unsegmented for much of their length. A phylogenetic analysis based on dermal skeletal features of Devonian actinopterygians indicates that Donnrosenia gen. nov. is the sister taxon to Howqualepis from the Middle Devonian of Victoria, Australia, and is embedded within a possible clade containing the actinopterygians from the Gogo Formation, Western Australia. This supports the concept of an endemic radiation of East Gondwanan actinopterygians, and reinforces the already strong biogeographical similarities between the Middle Devonian palaeofaunas of Australia and Antarctica.

Compagopiscis croucheri and Gogopiscis gracilis (Gardiner and Miles, 1994) were collected in high numbers and in different size classes from the Upper Devonian Gogo Formation, Western Australia. This material has provided the basis for an investigation of ontogentic and phenotypic variation of characters and their phylogenetic implications. We used the Principal Component Analysis to examine if variation between specimens assigned to C. croucheri and G. gracilis could be attributed to random variation. In our analysis we found that only the first two principal components showed any significant ability to discriminate between the specimens assigned to C. croucheri and G. gracilis. The first principal component is a measure of overall size of the specimen, so that variation in this principal component can be explained in terms of maturity and growth within a single species. Not all the anatomical variation observed in this study can be attributed to ontogeny and it is considered that the two-class ...

A description of the head, mandible, pectoral girdle, humerus, medial fins and their supports, and the dissociated vertebral column has been prepared for Onychodus jandemarrai n. sp. from the Gogo Formation (Frasnian) of Western Australia. This is the most completely known species of the genus. The feature influencing most of the head morphology is the retractable parasymphysial tusk whorls. Their presence has caused a reorganisation of the braincase, palate (including the loss of the vomers), and lateral displacement of the nasal capsules. The extensive mandibular articulation is in cartilage, and the mandibular symphysis is weak. This makes for a kinetic skull. There is a single submandibular on each side. The vertebral column is poorly ossified, consisting of intercentra which have no ventral contact, and pleurocentra. The neural arches have no longitudinal ligament, have unequal sides, and asymmetrical placing of the dorsal and ventral nerve root foramina. Each arch has an anterior surface that often attaches to the next anterior arch. The caudal fin is almost diphycercal; all the medial fins have strong support structures. An attempt is made to discuss the functional morphology of many features of the skeleton.

A new eurypterid, Rhenopterus waterstoni sp. nov., is described from the Gogo Formation (Frasnian, Upper Devonian) of Western Australia. This species is distinguished from related forms by the tuberculation of the anteriormost tergite and crenulated posterior margins of the carapace and opisthosomal segments. It is the only eurypterid specimen known from the Gogo Formation, the most complete eurypterid from Australia, and also the youngest representative of Rhenopterus in the fossil record. Structures retrieved from between the prosomal-opisthosomal juncture comprise polygonal tubes 30–40 μm in diameter, which are interpreted as sarcomeral sheaths of muscular tissue. Rhenopterus is reviewed: R. latus Stormer, 1936 is synonymized with R. diensti Stormer, 1936 as it is here recognized as a female sexual dimorph; R. maccarthyi (Kjellesvig-Waering, 1934) is an orthocone nautiloid.

This work is a contribution to IGCP 596., Here we present new data from the first well-preserved chondrichthyan fossil from the early Late Devonian (ca. 380–384 Mya) Gogo Formation Lägerstatte of Western Australia. The specimen is the first Devonian shark body fossil to be acid-prepared, revealing the endoskeletal elements as three-dimensional undistorted units: Meckel’s cartilages, nasal, ceratohyal, basibranchial and possible epibranchial cartilages, plus left and right scapulocoracoids, as well as teeth and scales. This unique specimen is assigned to Gogoselachus lynnbeazleyae n. gen. n. sp., This work was supported by grants from the Australian Research Council DP 0772138 awarded to GCY and JAL for travel and scanning of specimens at the ANU; and DP1092870 awarded to KMT for travel to collaborate. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The Late Devonian Gogo Formation of Western Australia has pro vided a wealth of new anatomical information about basal gnathostome fishes, particularly about the nature of early sarcopterygians (Miles, 1977; Campbell and Barwick, 1999; Long et al., 1997). New discov eries from Gogo of an as yet undescribed species of the osteichthyan Onychodus (Jessen, 1966; Fig. 1) show for the first time the structure of the braincase and other features which provide information concern ing the possible origin of the group. Recent discoveries of Psarolepis romeri, a primitive bony fish from the Late Silurian-Early Devonian of China and Vietnam (Yu, 1998; Zhu and Schultze, 1997; Zhu et al., 1999) have resulted in several opposing hypotheses of osteichthyan in terrelationships. However, the absence of data on the poorly known onychodontiform group has meant that key information relevant to the debate has not been previously available. In this paper some aspects of the anatomy of the new Gogo Onychodus, are compared with recently described material of Psarolepis, the oldest known possible sarcopter ygian fish, which have immediate bearing on competing schemes of basal osteichthyan phylogeny. It must be pointed out that a complete description of the new Gogo Onychodus material is currently being prepared by the author, Dr. Per Ahlberg, Prof. Ken Campbell, and Dr. Dick Barwick in association with the notes and descriptions from the late Dr. S. M. Andrews, so the views presented here are the sole opin ions of the author.

Lenticular stromatolite-barite-sulfide mounds, interpreted as sedimentary exhalative deposits, are exposed at several localities in Devonian reef complexes of the Canning basin, Western Australia. These mounds, hundreds of meters long and tens of meters thick, occur along contacts between basinal shales (Gogo Formation) and marginal-slope limestones (Sadler Limestone) and adjacent to synsedimentary faults cutting the Gogo Formation. The mounds are limestone buildups, composed of stromatolites intergrown with barite and cut by iron sulfide veins. The iron sulfides (marcasite and pyrite) are weathered to gossans at the surface. They fill fissures that probably formed as a result of contemporary seismic activity and the early compaction of underlying and adjoining shales. The stromatolite-barite-sulfide deposits also occur as allochthonous clasts in penecontemporaneous debris-flow deposits. Postdepositional compaction of basinal shales in the Gogo Formation commonly amounted to about 75 percent. This resulted in the expulsion of large volumes of fluids along permeable interbeds, shale-limestone contacts, and synsedimentary faults, reaching the sea floor as cool-fluid seepages. The expelled fluids carried dissolved carbonate, barium, iron, and reduced sulfur. They probably nourished chemosynthetic bacteria that mediated the deposition of stromatolites, barite, and iron sulfides, resulting in growth of the stromatolite-barite-sulfide buildups. There is no known economic mineralization in the exhalative buildups, but some drill holes encountered minor uneconomic veins of epigenetic Zn-Pb mineralization, filling narrow fissures that postdate the exhalative deposits. Economic epigenetic Zn-Pb deposits that have been mined elsewhere in the same general area of the Canning basin were formed during the early Carboniferous or latest Devonian, many millions of years after the exhalative deposits. Both exhalative and epigenetic phases of mineralization are thought to have been sourced through the compaction-driven dewatering of shales. The exhalative deposits are interpreted to have formed over seepages of cool fluids having salinities close to that of seawater, whereas the epigenetic deposits formed from much hotter fluids, probably brines, expelled during subsequent shale compaction.

The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of their reproductive biology. 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). 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 gardineri, also shows three small embryos inside it in the same position. Ptyctodontids have already provided the oldest definite evidence for vertebrate copulation, 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.

The squamation of a complete palaeoniscoid, M. durgaringa Gardiner & Bartram, 1977, from the Frasnian Gogo Formation is described. A variety of isolated scales from the Gneudna Formation, Carnarvon Basin, are referred to M. durgaringa on the basis of comparison with the described articulated specimen. Scales of various forms are attributed to specific regions of the body.

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.

The ontogenetic trajectories of fourteen dermal plates from Compagopiscis croucheri (Placodermi, Arthrodira) and,the more derived species Incisoscutum ritchei were compared. The mechanism of allometric predisplacement occured in: the biting division of the inferognathal; the anterior ventrolateral; and the median dorsal breadth. Allometric postdisplacement occured in the postmesial breadth and the orbital diameter and allometric hypermorphosis was seen in the increases of the prepineal length and the median dorsal length. It is suggested that the lengthwise growth occurs earlier in the ontogeny than breadthways growth and that dissociated allometric heterochrony has been an important mechanism in the evolution of the arthrodires.

Two monotypic genera of coccosteoid eubrachythoracid arthrodires are described from the Upper Devonian Gogo Formation of Western Australia as Compagopiscisgen. nov. and Gogopiscisgen. nov. They are most closely related to Torosteus Gardiner & Miles, also from the Gogo Formation, and all three are placed in the family Plourdosteidae Vezina, 1990; Compagopiscis and Gogopiscis are jointly the sister-group of Torosteus.

Holodipterus (Holodipterus) gogoensiswas first described by Miles (Zool. J. Linn. Soc. 61, 1-328 (1977)) from eight specimens from the Frasnian Gogo Formation of the Canning Basin, Western Australia. In 1991H. longiwas described by Campbell & Barwick from a single specimen from the same locality. Subsequent collecting has produced two other new species which we assign to two new subgenera, described herein asH. (Holodipteroides) elderaeandH.(Asthenorhynchus) meemannae. Diagnoses of the two new subgenera are given. A small isolated palate, which provides new information on the mode of growth of the group, is described as Holodontid gen. et sp. indet. It is shown that all these holodipterans have a distinctive mode of dental growth involving periodic and extensive resorption of denticles, teeth and calluses. Hypermineralized dentine occurs in both the teeth and the calluses. Smith (in Campbell & Smith,Rec. Aust. Mus. 39(3), 131-167 (1987); and in Smith,Mém. Mus. natn. Hist, nat., ParisC53, 179-194 (1988)) has argued that because teeth are developed only in dental laminae, which are complicated structures unlikely to have been evolved more than once, they are reliable guides to understanding phyletic relationships. Consequently she considered that holodipterans should be regarded as derivatives of a Speonesydrion-ike dipnoan that retained and developed numbers of shedding denticles. Campbell (in Campbell & Smith 1987), and Campbell & Barwick (inEarly vertebrates and related problems of evolutionary biology(ed. M.-m. Changet al.), Beijing Science Press (1991)) argued that teeth have evolved several times in dipnoans and that their presence in holodipterans is not indicative of relationship. The latter authors have given reasons for consideringHolodipterusto be a member of the so-called ‘rasping’ or ‘denticle shedding’ lineage which can be traced back to the Early DevonianUranolophus. The newly described subgenera add information vital for clarifying the position of the holodipterans. H. (Holodipteroides) had no true teeth, but it produced radial ridges on the palate and prearticulars simply by adding new raised tissue at the end of the radial ridges, and it had denticulated plates attached to the surface of the basihyal.H. (Asthenorhynchus)had a pectoral girdle of the same kind asGriphognathusand a number of dermopalatines and other denticulated plates at the anterior end of the palate, as doesH. (Holodipterus) gogoensisandGriphognathus whitei, which is the best documented member of the ‘denticle-shedding’ lineage. It is also shown that holodipterans andGriphognathusshared a distinctive pustulose/ perforate structure of the head bones. We therefore conclude that holodipterans, Griphognathus (and perhaps other rhynchodipterids) developed from some unspecified Middle Devonian stock that underwent rapid radiation either at the end of the Middle Devonian or in the early Late Devonian (Frasnian).

Long, J. A., 1994:03:28. A second incisoscutid arthrodire (Pisces, Placodermi) from the Late Devonian Gogo Formation. Western Australia. Alcheringa 18. 59–69. ISSN 0311-5518. A new incisoscutid arthrodire is described from the Upper Devonian Gogo Formation of Western Australia as Gogosteus sarahae gen. et sp. nov. It is characterised by its narrow headshield with cheek unit firmly attached to skull roof, crushing gnathal plates, deep postnasal plates, elongate anterior lateral plate with deeply embayed postbranchial notch and squarely cut posterior margin, and fine dermal ornamentation. The family Incisoscutidae Denison 1984 is redefined to include Incisoscutum ritchiei Dennis & Miles 1981 and Gogosteus gen. nov., and the superfamily Incisoscutoidea nov. defined to include Incisoscutidae and Camuropiscidae.

A new genus of chirodipterid lungfish, Gogodipterus gen. nov., is erected for Chirodipterus paddyensis Miles, 1977, after further preparation of the holotype revealed that the palate has an unusual parasphenoid with a raised buccal lozenge that participated in the reduction of food. Other major differences between Gogodiptems and Cllirodipterus are in the dentition and features of the braincase. A revised classification ofthechirodipterid group is proposed in which the families Chirodipteridae Campbell and Barwick, 1990, and Stomiahykidae Bernacsek, 1977 are placed within the superfamily Chirodipteroidea superfam. nov. The family Chirodipteridae contains two subfamilies: the Chirodipterinae subfam. nov. and the Pillararhynchinae subfam. nov. Gogodipterus is regarded as a sister genus to Chirodipterus based on synapomorphies of the palate, dentition and scales, and absence of more specialized characters seen in Pillararhynchus and orbitorhynchus.

Attempts at understanding evolutionary relationships among Paleozoic Dipnoi (lungfish) using cladistic methodology have proved totally unsatisfactory (Miles 1977; Marshall 1987). We attempt to reconstruct the relationships between the better known genera using a method that involves the recognition of lineages based on evolving functional complexes, particularly those involved with food reduction and respiration. Within these broadly defined lineages, we have defined sub-lineages based on evolutionary patterns shown by structures that have been stratigraphically dated; such patterns are found inter alia in the roofing bones and the external dermal bones of the mandible. A number of new suborders and families are recognised; genera for which further morphological data are required before they can be assigned to a higher taxon are indicated; two generic synonyms are recognised.In appendices, short descriptions are given of two new genera—Pillararhynchus from the Gogo Formation (Upper Devonian) of Western Australia, and Sorbitorhynchus from the Emsian of Guangxi, China.

The principal objective of our paper was to describe the exceptional muscle and nerve tissues occurring in the 380 Myr old placoderms from the Gogo Formation in northern Western Australia. It was never our intention to produce an in-depth discussion on early vertebrate phylogeny, but instead to

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.

Moythomasia is one of the most speciose and completely known of all Devonian actinopterygian genera and has been incorporated into numerous phylogenetic studies. However, several species remain incompletely documented despite being known from excellent fossil material. Specimens from the Late Devonian of Germany and Australia are described herein. A form from Bergisch Gladbach, Germany, previously described by Jessen as Moythomasia cf. striata, is recognized as a new species: M. lineata, sp. nov. Newly prepared specimens of Moythomasia durgaringa from the Gogo Formation, Western Australia, allow for the first rigorous full-body reconstructions of this species. Aspects of the dermal skeleton and body shape of this form are updated over previous descriptions. The genus is currently problematic owing to the highly fragmentary nature of the type species, M. perforata from Kokenhusen; however, it is considered provisionally valid owing to distinctive cranial ornamentation. The three completely known sp...

Co-occuring conodonts, radiolarians, and sponge spicules from the type locality of the Slaven Chert, northern Shoshone Range, Nevada, indicate that the radiolarian and sponge spicule assemblage described herein correlates with the Late rhenana conodont Zone (late Frasnian). The moderately well preserved radiolarians are the first Frasnian-age fauna described from the Western Hemisphere. They include spumellarians, Ceratoikiscum, and Paleoscenidium, and a radiolarian which we have assigned to a new genus, Durahelenifore Boundy-Sanders and Murchey, with its type species, Durahelenifore robustum Boundy-Sanders and Murchey. Sponge spicules include umbellate microscleres of the Subclass Amphidiscophora, Order Hemidiscosa, previously documented only in Pennsylvanian and younger rocks. INTRODUCTION Most of the documentation of Devonian radiolarian faunas, and all of the documentation of Western Hemisphere faunas, has been of Famennian taxa (Foreman 1963; Coles and Snyder 1985; Cheng 1986; Aitchison 1990; Coles 1991; Noble 1992; Aitchison, in press). Previously, the only well-dated Frasnian faunas have been from the southern Urals (Nazarov 1975), the Gogo Formation of Western Australia (Nazarov et al. 1982; Nazarov and Ormiston 1983; Aitchison, 1993), from the Yarrimie Formation near Tamworth, New South Wales, eastern Australia (Aitchison 1990), and from the Liukiang Formation, eastern and southern Guangxi Province, China (Li and Wang 1991). The fauna described in this paper is the first Frasnian fauna described from the Western Hemisphere. We focus on samples from the type locality of the Slaven Chert in Nevada, but the most distinctive and previously undescribed species in the assemblage also occurs in the Barita de Sonora district near Hermosillo, Mexico, and in the Yugambal terrane of the eastern New England orogen, Western Australia (J.C. Aitchison, written commun. 1992). A similar radiolarian occurs in the Gamilaroi terrane of the New England orogen, Eastern Australia, in rocks thought to be Middle Devonian in age (J.C. Aitchison, written commun. 1993). The Nevada locality has yielded not only sponge spicules and the new radiolarian species, but also an abundance of conodonts which indicate that this assemblage correlates with the late Frasnian Late rhenana Zone (Ziegler and Sandberg 1990). This *Present address: 17859 149th Ave. NE, Woodinville WA 98072-6202 co-occurrence provides an important tie between radiolarian and conodont biochronologies. The new radiolarian, Durahelenifore robustum n. gen. and n. sp., shares many characteristics with the genus Helenifore. We suggest that the heleniforids may be diagnostic of the upper part of the Frasnian Stage, although they do not occur in every deep-water Frasnian assemblage (Li and Wang 1991). The occurrence of hemidiscid sponge spicules in the Slaven Chert samples extends the range of this spicule morphology downward from its previous lowest known occurrence in Pennsylvanian rocks (Finks 1983). Previously published radiolarian biostratigraphies cover Famennian and higher strata (Holdsworth and Jones 1980a, b; Miller et al. 1984; Cheng 1986 and Holdsworth therein; Schwartzapfel 1990). A radiolarian biostratigraphy for Frasnian and lower strata awaits the discovery and study of coherent, continuous sections. GEOLOGIC SETTING The Devonian Slaven Chert traditionally has been regarded as the youngest formation in the Roberts Mountains allochthon (Madrid 1987; Gilluly and Gates 1965). The Roberts Mountains sequence was deposited in a basin that may be described as episodically sediment-starved: cherts of Ordovician, Silurian, and Devonian age alternate with numerous and in places voluminous sequences of clastic rocks. Although the connection between the Roberts Mountains allochthon and other North American sequences is well accepted, several lithostratigraphic, sedimentological, and faunal differences warn against drawing an overly facile correlation between the Roberts Mountains allochthon and the distal miogeoclinal section of east-central Alaska (Turner, Madrid, and Miller micropaleontology, vol. 45, no. 1, pp. 62-68, text-figures 1-2, plates 1-2, table 1, 1999 62 This content downloaded from 207.46.13.120 on Wed, 14 Sep 2016 04:13:00 UTC All use subject to http://about.jstor.org/terms Micropaleontology, vol. 45, no. 1, 1999