Eubrachythoracid arthrodires with tubular rostral plates from Gogo, Western Australia

Two monotypic genera of tubular-snouted eubrachythoracid arthrodires are described from the Upper Devonian Gogo Formation of Western Australia as Rolfosteur gen nov. and Tubonnsus gen. nov. They are most closely related to Camuropiscis Dennis & Miles, also from the Gogo Formation, and all three are therefore placed in the family Camuropiscidae nov. Rolfosteus and Tubonasus are jointly the sister-group of Camuropiscis .     

Eubrachythoracid arthrodires from Gogo, Western Australia

Two monotypic genera of coccosteoid eubrachythoracid arthrodires are described from the Upper Devonian Gogo Formation of Western Australia as Compagopiscis gen. nov. and Gogopiscis gen. 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.     

A New Eurypterid (Chelicerata: Eurypterida) from the Upper Devonian Gogo Formation of Western Australia, With A Review of the Rhenopteridae

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 Størmer, 1936 is synonymized with R. diensti Størmer, 1936 as it is here recognized as a female sexual dimorph; R. maccarthyi (Kjellesvig-Waering, 1934) is an orthocone nautiloid.     

Endoskeletal structure in Cheirolepis (Osteichthyes,Actinopterygii), An early ray‐finned fish

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.     

A eubrachythoracid arthrodire with a snubnose from Gogo, Western Australia

A new eubrachythoracid arthrodire, Simosteus tuberculatus gen. et sp. nov., is described from the Upper Devonian Gogo Formation of Western Australia and its structure and relationships are discussed. It is related to the trematosteids, leiosteids and hadrosteids on the evidence of 'fused' preorbital and postnasal bones.     

A pachyosteomorph arthrodire from Gogo, Western Australia

A new monotypic genus of eubrachythoracid arthrodire is described from die Upper Devonian Gogo Formation of Western Australia as Incisoscutum ritchiei gen. et sp. nov. It is at die pachyosteomorph level of organization, having no contact between the plates of die flank and those of the ventral shield behind the pectoral fin. It is interchangeable widi Coccosteus spp. and a number of earlier described Gogo forms in a sketch dadogram for arthrodires, but its phylogenedc relationships are unknown. Well preserved material of die scapulocoracoid throws new light on die structure of this element in arthrodires, particularly widi respect to variations in die pattern of canals and foramina.     

Crown group Oxyphotobacteria postdate the rise of oxygen

The rise of oxygen ca. 2.3 billion years ago (Ga) is the most distinct environmental transition in Earth history. This event was enabled by the evolution of oxygenic photosynthesis in the ancestors of Cyanobacteria. However, long‐standing questions concern the evolutionary timing of this metabolism, with conflicting answers spanning more than one billion years. Recently, knowledge of the Cyanobacteria phylum has expanded with the discovery of non‐photosynthetic members, including a closely related sister group termed Melainabacteria, with the known oxygenic phototrophs restricted to a clade recently designated Oxyphotobacteria. By integrating genomic data from the Melainabacteria, cross‐calibrated Bayesian relaxed molecular clock analyses show that crown group Oxyphotobacteria evolved ca. 2.0 billion years ago (Ga), well after the rise of atmospheric dioxygen. We further estimate the divergence between Oxyphotobacteria and Melainabacteria ca. 2.5–2.6 Ga, which—if oxygenic photosynthesis is an evolutionary synapomorphy of the Oxyphotobacteria—marks an upper limit for the origin of oxygenic photosynthesis. Together, these results are consistent with the hypothesis that oxygenic photosynthesis evolved relatively close in time to the rise of oxygen.     

A new species of eastmanosteid arthrodire (Pisces: Placodermi) from Gogo, Western Australia

A new species of Eastmanosteus Obruchev is described from the Upper Devonian Gogo Formation of Western Australia as E. calliaspis sp. nov. It is at the pachyosteomorph level of organization having no contact between the plates of the flank and those of the ventral shield behind the pectoral fin. Well preserved material of the parasphenoid and scapulocoracoid throws further light on the structure of these elements in arthrodires. The genus Eastmanosteus is reviewed.     

New durophagous arthrodires from Gogo, Western Australia

Three new monotypic genera of eubrachythorarid arthrodires with crushing toothplates are described from the Upper Devonian Gogo Formation of Western Australia as Bruntonichthys multidens gen. et sp. nov., Bullerichthysfascidens gen. et sp. nov. and Kendrickkhthys cavemosus gen. et sp. nov. Their structure and relationships are discussed within the framework provided by a sketch cladogram. All three are interchangeable with Coccosteus spp. but their phylogenetic relationships are not known in any detail. However, Kendrickkhthys does appear to be immediately related to Dinomylostoma from North America.     

Out of South‐East Asia: phylogeny and biogeography of the spiny ant genus Polyrhachis Smith (Hymenoptera: Formicidae)

Spiny ants (Polyrhachis Smith) are a hyper‐diverse genus of ants distributed throughout the Palaeotropics and the temperate zones of Australia. To investigate the evolution and biogeographic history of the group, we reconstructed their phylogeny and biogeography using molecular data from 209 taxa and seven genes. Our molecular data support the monophyly of Polyrhachis at the generic level and several of the 13 recognized subgenera, but not all are recovered as monophyletic. We found that Campomyrma Wheeler consists of two distinct clades that follow biogeographic affinities, that the boundaries of Hagiomyrma Wheeler are unclear depending on the analysis, that Myrma Billberg might be treated as one or two clades, and that Myrmhopla Forel is not monophyletic, as previously proposed. Our biogeographic ancestral range analyses suggest that the evolution of Polyrhachis originated in South‐East Asia, with an age of the modern crown‐group Polyrhachis of 58 Ma. Spiny ants dispersed out of South‐East Asia to Australia several times, but only once to mainland Africa around 26 Ma.     

Tommotiids from the early Cambrian (Series 2, Stage 3) of Morocco and the evolution of the tannuolinid scleritome and setigerous shell structures in stem group brachiopods

An assemblage of tannuolinid sclerites is described from the Amouslek Formation (Souss Basin) of the Anti‐Atlas Mountains in Morocco. The assemblage contains two species, Tannuolina maroccana n. sp., which is represented by a small number of mitral and sellate sclerites, and Micrina sp., represented by a single mitral sclerite. Tannuolina maroccana differs from other species of the genus in the presence of both bilaterally symmetrical and strongly asymmetrical sellate sclerites. This observation suggests that the scleritome of Tannuolina was more complex than previously thought and that this tommotiid may have held a more basal position in the brachiopod stem group than previously assumed. The shell structure of both T. maroccana and Micrina sp. is well preserved and exhibits two fundamentally different sets of tubular structures, only one of which was likely to contain shell‐penetrating setae. Based on these observations, the structure of the tannuolinid shell is discussed and its implications for the evolution of tubular microstructures in stem and crown group brachiopods are analysed.     

Early evolution of the Eukaryota

The evolution of eukaryotes represents one of the most fundamental transitions in the history of life on Earth; however, there is little consensus as to when or over what timescale it occurred. Review of recent hypotheses and data in a phylogenetic context yields a broadly coherent account. Critical re‐assessment of the palaeontological record provides convincing evidence for the presence of crown‐group eukaryotes in the late Palaeoproterozic, and stem‐group eukaryotes extending back to the early Archaean. Despite their relatively early establishment, crown‐eukaryotes appear not to have become ecologically significant until the middle Neoproterozoic. I argue that this billion‐year delay was due to the singular, contingent evolution of crown‐group animals and their unique capacity to drive co‐evolutionary change.     

Infaunal augurs of the Cambrian explosion: An Ediacaran trace fossil assemblage from Nevada,USA

Morphologically complex trace fossils, recording the infaunal activities of bilaterian animals, are common in Phanerozoic successions but rare in the Ediacaran fossil record. Here, we describe a trace fossil assemblage from the lower Dunfee Member of the Deep Spring Formation at Mount Dunfee (Nevada, USA), over 500 m below the Ediacaran–Cambrian boundary. Although millimetric in scale and largely not fabric‐disruptive, the Dunfee assemblage includes complex and sediment‐penetrative trace fossil morphologies that are characteristic of Cambrian deposits. The Dunfee assemblage records one of the oldest documented instances of sediment‐penetrative infaunalization, corroborating previous molecular, ichnologic, and paleoecological data suggesting that crown‐group bilaterians and bilaterian‐style ecologies were present in late Ediacaran shallow marine ecosystems. Moreover, Dunfee trace fossils co‐occur with classic upper Ediacaran tubular body fossils in multiple horizons, indicating that Ediacaran infauna and epifauna coexisted and likely formed stable ecosystems.     

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

Tetraodontiformes (pufferfishes and kin) is a taxonomically and structurally diverse, widely‐distributed clade of acanthomorphs, whose members often serve as models for genomics and, increasingly, macroevolutionary studies. Morphologically disparate Palaeogene fossils suggest considerable early experimentation, but these flattened specimens often preserve limited information. We present a three‐dimensionally preserved beaked tetraodontiform from the early Eocene (c. 53 Ma) London Clay Formation, UK. Approximately coeval with the oldest crown tetraodontiforms, ?Ctenoplectus williamsi gen. et sp. nov. presents an unprecedented combination of characters, pairing a fused beak‐like dentition with prominent dorsal‐fin spines that insert atop transversely‐expanded pterygiophores roofing the skull. Bayesian total‐evidence tip‐dating analysis indicates that ?Ctenoplectus represents the sister lineage of Triodontidae and highlights considerable levels of homoplasy in early tetraodontiform evolution. According to our dataset, rates of morphological character evolution were elevated at the origin of crown Tetraodontiformes, especially within gymnodonts, but declined after the principal body plans were established. Such ‘early burst’ patterns are regarded as a hallmark of adaptive radiations, but are typically associated with diversification at smaller spatiotemporal scales. However, denser sampling of Neogene and Recent taxa is needed to confirm this pattern.     

Testing the phylogenetic position of Cambrian pancrustacean larval fossils by coding ontogenetic stages

The study of ontogeny as an integral part of understanding the pattern of evolution dates back over 200 years, but only recently have ontogenetic data been explicitly incorporated into phylogenetic analyses. Pancrustaceans undergo radical ontogenetic changes. The spectacular upper Cambrian “Orsten” fauna preserves phosphatized fossil larvae, including putative crown‐group pancrustaceans with amazingly complete developmental sequences. The putative presence and nature of adult stages remains a source of debate, causing spurious placements in a traditional morphological analysis. We introduce a new coding method where each semaphoront (discrete larval or adult stage) is considered an operational taxonomic unit. This avoids a priori assumptions of heterochrony. Characters and their states are defined to identify changes in morphology throughout ontogeny. Phylogenetic analyses of semaphoronts produced possible relationships of each Orsten fossil to the crown‐group clade expected from morphology shared with extant larvae. Bredocaris is a member of the stem lineage of Thecostraca or (Thecostraca + Copepoda), and Yicaris and Rehbachiella are probably members of the stem lineage of Cephalocarida. These placements rely directly on comparisons between extant and fossil larval character states. The position of Phosphatocopina remains unresolved. This method may have broader applications to other phylogenetic problems which may rely on ontogenetically variable homology statements.     

The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia

While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms-members of Eusuchia-do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98-95 Myr ago; Albian-Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms-a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.