Showing papers in "Palaeontology in 2012"
TL;DR: A broad overview of the Phanerozoic history of fish diversity is provided, placing a special emphasis on intervals of turnover, evolutionary radiation, and extinction.
Abstract: Fishes include more than half of all living animals with backbones, but large-scale palaeobiological patterns in this assemblage have not received the same attention as those for terrestrial vertebrates. Previous surveys of the fish record have generally been anecdotal, or limited either in their stratigraphic or in their taxonomic scope. Here, we provide a broad overview of the Phanerozoic history of fish diversity, placing a special emphasis on intervals of turnover, evolutionary radiation, and extinction. In particular, we provide in-depth reviews of changes during, and ecological and evolutionary recovery after, the end-Devonian (Hangenberg) and Cretaceous–Palaeogene (K–Pg) extinctions.
179 citations
TL;DR: The taxonomic origin of the white shark, Carcharodon, is a highly debated subject as mentioned in this paper and new fossil evidence presented in this study suggests that the genus is derived from the broad-toothed "mako" Carcharis hastalis, and includes the new species C. hubbelli sp. nov.
Abstract: The taxonomic origin of the white shark, Carcharodon, is a highly debated subject. New fossil evidence presented in this study suggests that the genus is derived from the broad-toothed ‘mako’, Carcharodon (Cosmopolitodus) hastalis, and includes the new species C. hubbelli sp. nov. – a taxon that demonstrates a transition between C. hastalis and Carcharodon carcharias. Specimens from the Pisco Formation clearly demonstrate an evolutionary mosaic of characters of both recent C. carcharias and fossil C. hastalis. Characters diagnostic to C. carcharias include the presence tooth serrations and a symmetrical first upper anterior tooth that is the largest in the tooth row, while those indicative of C. hastalis include a mesially slanted third anterior (intermediate) tooth. We also provide a recalibration of critical fossil horizons within the Pisco Formation, Peru using zircon U-Pb dating and strontium-ratio isotopic analysis. The recalibration of the absolute dates suggests that Carcharodon hubbelli sp. nov. is Late Miocene (6–8 Ma) in age. This research revises and elucidates lamnid shark evolution based on the calibration of the Neogene Pisco Formation.
130 citations
TL;DR: The arrangement of the elbow joint supports the view that the great appendage evolved into the chelicera of Chelicerata sensu stricto, as similar joints are found in various ingroup taxa such as Xiphosura, Opiliones or Palpigradi.
Abstract: We redescribe the morphology of Yohoia tenuis (Chelicerata sensu lato) from the Cambrian Burgess Shale Lagerstatte. The morphology of the most anterior, promi- nent, so-called great appendage changes throughout ontog- eny. While its principal morphology remains unaltered, the length ratios of certain parts of the great appendage change significantly. Furthermore, it possesses a special jack-knifing mechanism, i.e. an elbow joint: the articulation between the distal one of the two peduncle elements and the most proxi- mal of the four spine-bearing claw elements. This morphol- ogy might have enabled the animal to hunt like a modern spearer-type mantis shrimp, an analogy enhanced by the sim- ilarly large and protruding eyes. For comparison, details of specimens of selected other great-appendage arthropods from the Lower Cambrian Chengjiang Lagerstatte have been inves- tigated using fluorescence microscopy. This revealed that the morphology of the great appendage of Y. tenuis is much like that of the Chengjiang species Fortiforceps foliosa and Jianfen- gia multisegmentalis. The morphology of the great appendage of the latter is even more similar to the morphology devel- oped in early developmental stages of Y. tenuis, while the morphology of the great appendage of F. foliosa is more sim- ilar to that of later developmental stages of Y. tenuis. The arrangement of the elbow joint supports the view that the great appendage evolved into the chelicera of Chelicerata sensu stricto, as similar joints are found in various ingroup taxa such as Xiphosura, Opiliones or Palpigradi. With this, it also supports the interpretation of the great appendage to be homologous with the first appendage of other arthropods.
115 citations
TL;DR: A unified and approachable scheme for the description and phylogenetic analysis of frondose genera and their species and it is hoped that this scheme will provide a robust framework for future studies of rangeomorph ontogeny and evolution.
Abstract: Ongoing discoveries of new rangeomorph fossils from the Ediacaran of Avalonia allow us to put forward a unified and approachable scheme for the description and phylogenetic analysis of frondose genera and their species. This scheme focuses upon the branching morphology of rangeomorph units. Our system has the advantage of being applicable at all visible scales of subdivision and is suitable for the study of isolated fragmentary specimens. The system is also free from hypothesis about biological affinity and avoids tectonically influenced features such as shape metrics. Using a set of twelve character states within this unified scheme, we here present emended diagnoses for Beothukis, Avalofractus, Bradgatia, Hapsidophyllas, Fractofusus, Trepassia and Charnia, together with a more extensive taxonomic treatment of the latter genus. For those forms that fall within the morphological spectrum between Trepassia and Beothukis, we introduce Vinlandia gen. nov. It is hoped that this scheme will provide a robust framework for future studies of rangeomorph ontogeny and evolution.
73 citations
TL;DR: Several fused clusters of conodont elements of the genera Neospathodus and Novispathodus were recovered from limestone beds at the Dienerian-Smithian and Smithi- an-Spathian boundaries, respectively, from several localities in Guangxi province, South China as mentioned in this paper.
Abstract: Several fused clusters of conodont elements of the genera Neospathodus and Novispathodus were recovered from limestone beds at the Dienerian-Smithian and Smithi- an-Spathian boundaries, respectively, from several localities in Guangxi province, South China. Conodont clusters are otherwise extremely rare in the Triassic, and these are first described for the Early Triassic. The exceptional specimens partially preserve the relative three-dimensional position and orientation of ramiform elements and are therefore extremely important for testing hypotheses on the architecture of appa- ratuses. These specimens partly confirm the previous recon- struction of the Novispathodus apparatus by Orchard. Within apparatuses of members of superfamily Gondolelloidea, ele- ments previously identified as occupying the S1 and S2 posi- tions instead occupy the S2 and S1 positions. Similarly, within apparatuses of members of the subfamily Novispa- thodinae, elements previously referred to S3 and S4 positions are reinterpreted to have occupied S4 and S3 positions, respectively.
55 citations
TL;DR: In the Lagerstatte of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north-west Germany, 17 sediment-compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded.
Abstract: From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north-west Germany), 17 sediment-compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstatte, upper jaws and anaptychi of ammonites rank among the commonest fossils.
52 citations
TL;DR: A new family, Sinoalidae Wang and Szwedo fam.
Abstract: A new family, Sinoalidae Wang and Szwedo fam. nov., is described from the Middle Jurassic Daohugou Biota (Inner Mongolia, China). Two new genera with three new species (Sinoala parallelivena Wang and Szwedo gen. et sp. nov., Jiania crebra Wang and Szwedo gen. et sp. nov., and Jiania gracila Wang and Szwedo sp. nov.) are erected based on well-preserved whole-bodied specimens. The morphologi- cal characters of Procercopidae and the new family are given, and a key to the species of Sinoalidae is presented. The genera Luanpingia Hong, 1983 and Huabeicercopis Hong, 1983 are revised and attributed to Sinoalidae. The genera Mesocercopis Hong, 1983 and Sinotettegarcta Hong, 1986 are considered junior synonyms of Anthoscytina Hong, 1983. Taxa assigned to Sinoalidae fam. nov. cannot be attributed to any previously known family, but share some general (plesiomorphic) characters with ancient Clypeata, for example, postclypeus distinctly swollen, transversely wrin- kled, antenna with a flagellum of a few elongate segments, frons with median ocellus and lateral ocelli on crown. More- over, the new family is closely related to Procercopidae (Cercopoidea) based on a pronotum with a median incision at the hind margin; tegmen slender, partly punctuate, basal portion of Sc not exceeding apex of basal cell, and hind legs with lateral spines. It has a mixture of ancestral characters shared with Hylicelloidea and Jurassic Procercopidae and some derived characters. Therefore, it is tentatively placed in Cercopoidea. A preliminary phylogram of Clypeata is presented based on the combination of fossil and morphological data.
45 citations
TL;DR: This new egg type is attributed to a small theropod, probably with a single oviduct like birds and whose mosaic distribution of features is a combination between that of birds and nonavian theropods, enhances the arguments supporting the close phylogenetic relationships between both groups.
Abstract: A new type of small, ovoid dinosaur egg, Sankofa pyrenaica oogen. nov. oosp. nov., with a prismatic type eggshell is described from upper Cretaceous (upper Campanian–Maastrichtian) deposits of the Montsec area, South Pyrenean Central Unit, Lleida, Catalonia, Spain. This egg type was sub-vertically laid in only two rich monospecific sites of a single stratigraphic layer from coastal deposits of the Aren Formation, interpreted as an emerged beach ridge of a barrier island – lagoon depositional system. The size and shape of these eggs with their asymmetric poles are roughly similar to modern hen eggs, which is unusual in the Cretaceous fossil egg record. Its phylogenetic position clusters with bird and Troodontid eggs. A morphospace analysis of egg shapes shows the similarity of the new egg to a Campanian fossil bird egg from Argentina, both being intermediate between modern-bird eggs and extinct nonavian theropod eggs. However, the eggshell microstructure of Sankofa pyrenaica differs from that of bird eggs in its incipient squamatic texture. It has a peculiar pattern of interlocking small crystals in the middle of the palisade layer, instead of the thick squamatic structure commonly present in modern avian eggshells. This new egg type is attributed to a small theropod, probably with a single oviduct like birds and whose mosaic distribution of features is a combination between that of birds and nonavian theropods. This enhances the arguments supporting the close phylogenetic relationships between both groups.
45 citations
TL;DR: In this article, the authors compare a number of proxies representing the three main aspects of sampling, i.e., sedimentary rock volume, rock accessibility and worker effort, with palaeodiversity in a geographically and stratigraphically constrained data set, the marine Lower Jurassic outcrop of the Dorset and East Devon Coast.
Abstract: Most studies of the adequacy of the fossil record have been carried out at a global or continental scale, and they have used sampling proxies that generally do not incorporate all aspects of sampling (i.e. rock volume, accessibility, effort). Nonetheless, such studies have identified positive correlations between apparent diversity and various sampling proxies. The covariation of fossil and rock record signals has been interpreted as evidence for bias or for a common cause, such as sea level change, or as evidence that the signals are in some ways redundant with each other. Here, we compare a number of proxies representing the three main aspects of sampling, (1) sedimentary rock volume, (2) rock accessibility and (3) worker effort, with palaeodiversity in a geographically and stratigraphically constrained data set, the marine Lower Jurassic outcrop of the Dorset and East Devon Coast. We find that the proxies for rock volume and accessibility do not correlate well with the other sampling proxies, nor with apparent diversity, suggesting that the total amount of sedimentary rock preserved does not influence apparent diversity at a local scale, that is, the rock record at outcrop has been sampled efficiently. However, we do find some correlations between apparent diversity and proxies for worker effort. The fact that the proxies do not correlate significantly with each other suggests that none can be regarded as an all-encompassing sampling proxy that covers all aspects of bias. Further, the presence of some correlations between sampling proxies and diversity most probably indicates the bonanza effect, as palaeontologists have preferentially sampled the richest rock units.
43 citations
TL;DR: Microvertebrate sampling of the Stairway Sandstone has yielded scales that are chondrichthyan‐like in their overall construction, and Tantalepis gatehousei gen. et sp.
Abstract: Microvertebrate sampling of the Stairway Sand- stone (Darriwilian, Middle Ordovician, central Australia) has yielded scales that are chondrichthyan-like in their overall construction, and Tantalepis gatehousei gen. et sp. nov. is erected here to describe these specimens. Tantalepis gatehousei gen. et sp. nov. is the stratigraphically oldest microsquamous taxon described thus far, and the 'shark-like' appearance of the scales may extend the chondrichthyan lineage back into the Middle Ordovician. The presence of 'shark-like' scales in the fossil record some 50 myr prior to the first articulated chondrichthyan body fossils and 44 myr before the first clearly identifiable chondrichthyan teeth suggests there is a considerable scope for the recovery of articulated specimens with which to document the early history of crown gnathosto- mes. Traditional hypotheses of phylogenetic relationships among early jawed vertebrates were recently challenged by the proposal of a radically different tree topology. However, the development of a new data set specifically addressing scale- based characters is required before taxa such as Tantalepis, that are based upon disarticulated remains alone, can be firmly placed within the emerging, revised, evolutionary narrative.
41 citations
TL;DR: This study presents a redescription and updated comparison of the anatomy of Ptomacanthus based on unfigured material from the type and referred specimens, as well as adding new data on spine and scale histology.
Abstract: The spine-bearing jawed vertebrates (gnathostomes) assigned to the assemblage ‘Acanthodii’ play a key role in understanding the early evolution of osteichthyans and chondrichthyans. Amongst ‘acanthodians’, the genus Ptomacanthus has played a prominent role owing to its shark-like tooth files. Recently described braincase material from this taxon contrasts strongly with the osteichthyan-like braincase of Acanthodes, the only other ‘acanthodian’ for which this anatomy is well known. This seriously challenges acanthodian monophyly or at least the prevailing interpretation of Acanthodes. This study presents a redescription and updated comparison of the anatomy of Ptomacanthus based on unfigured material from the type and referred specimens, as well as adding new data on spine and scale histology. Ptomacanthus is remarkably heterosquamous compared to some other ‘acanthodians’. Further to its resemblances to Climatius, Ptomacanthus shares some features of the external morphology of its scales with the enigmatic genus Obtusacanthus. The scale crowns of Ptomacanthus exhibit both superpositional and areal growth. The bases, however, grow separately from the crown. As in Acanthodes, scales are here inferred to be added to the body from posterior to anterior. In spite of its chondrichthyan-like form and characters, Ptomacanthus remains difficult to place on either the chondrichthyan, osteichthyan or gnathostome stem. Different placements each require invoking considerable character incongruence. Nevertheless, these new data from Ptomacanthus provide broader anatomical context for hard tissue characters commonly described on the basis of isolated remains.
TL;DR: Phthipodochiton thraivensis presents an apparent mosaic of aplacophoran and polyplacphoran features and as such will inform the understanding of the relationship between these groups of extant molluscs.
Abstract: The palaeoloricate ‘polyplacophorans’ are an extinct paraphyletic group of basal chiton-like organisms known primarily from their fossilized valves. Their phylogenetic placement remains contentious, but they are likely to include both stem-group Polyplacophora and stem-group Aplacophora. Candidates for the latter position include ‘Helminthochiton’thraivensis from the Ordovician of Scotland, which we redescribe here through a combined optical and micro-CT (XMT) restudy of the type material. The 11 specimens in the type series are all articulated, presenting partial or complete valve series as well as mouldic preservation of the girdle armature; they demonstrate a vermiform body plan. The valves are typically palaeoloricate in aspect, but differ in detail from all existing palaeoloricate genera; we hence erect Phthipodochiton gen. nov. to contain the species. The most notable feature of the fossils is the spicular girdle; this is impersistently preserved, but demonstrably wraps entirely around the ventral surface of the animal, implying that a ‘true’ (i.e. polyplacophoran like) foot was absent, although we do not exclude the possibility of a narrow solenogastre-like median pedal groove having been present. Phthipodochiton thraivensis presents an apparent mosaic of aplacophoran and polyplacophoran features and as such will inform our understanding of the relationship between these groups of extant molluscs. An inference may also be drawn that at least some other palaeoloricates possessed an ‘armoured aplacophoran’ body plan, in contrast to the ‘limpet-like’ body plan of extant Polyplacophora.
TL;DR: The question of whether postcrisis recovery of vertebrate faunas, including the radiation of Temnodontosaurus into a new ecological niche, may have been a consequence of marine ecosystem reorganization across this event is raised.
Abstract: We describe an almost complete ichthyosaur skeleton from the middle Toarcian (Lower Jurassic) of the Beaujolais foothills near Lyon, France, and assign it to Temnodontosaurus azerguensis sp. nov. This new species exhibits cranial peculiarities such as a thin, elongated and possibly edentulous rostrum, as well as a reduced quadrate. These characters indicate dietary preferences that markedly differ from other species referred to Temnodontosaurus, a genus previously considered as the top predator of the Early Jurassic seas. Despite a conservative postcranial skeleton, we propose that Temnodontosaurus is one of the most ecologically disparate genera of ichthyosaurs, including apex predators and now a soft prey longirostrine hunter. Ammonites collected from the same stratigraphic level as the described specimen indicate that the new species is somewhat younger (bifrons ammonite zone) than the most known Toarcian ichthyosaurs and therefore slightly postdates the interval of severe environmental changes and marine invertebrate extinctions known as the Toarcian Oceanic Anoxic Event. The present study therefore raises the question of whether postcrisis recovery of vertebrate faunas, including the radiation of Temnodontosaurus into a new ecological niche, may have been a consequence of marine ecosystem reorganization across this event.
TL;DR: Ten of 15 species recognized in this study have not been reported from other regions, which may indicate increasing provincialism towards the end of the Early Triassic, or reflect the still insufficient knowledge of faunas from the epoch that followed the greatest crisis in the history of life.
Abstract: Based on newly collected material from the uppermost Smithian and lower to middle Spathian (Oleneki- an, Lower Triassic) of the Salt Range and Surghar Range (Pakistan), 15 bivalve species belonging to 11 genera are described, including two new genera, Eobuchia and Dimor- phoconcha , and one new species, Palaeoneilo ? fortistriata . Eo- buchia gen. nov. is placed in a new subfamily, the Eobuchiinae, which differs from the Buchiinae in having an almost planar and only moderately inclined or offset right anterior auricle. Inclination of the right anterior auricle is proposed as a synapomorphy of the revised suborder Monotidina, which includes the Buchiidae, Monotidae, Oxytomidae and, tentatively, the Dolponellidae. The Pseudo- monotidae, Chaenocardiidae and Claraiidae are discussed as candidate ancestors of the Monotidina. Dimorphoconcha gen. nov., provisionally placed in the Limidae, is a morphologically unusual genus characterized by a globose shell centre and a strongly plicate fringe. Permophorus costatus , which was pre- viously known exclusively from Permian strata, is reported from the Spathian of the Surghar Range. This record extends the range of P. costatus for at least 8 Myr and makes it the first reported Lazarus species , with an outage of more than 2 Myr after the end-Permian mass extinction. Ten of 15 species recognized in this study have not been reported from other regions, which may indicate increasing provincialism towards the end of the Early Triassic, or, alternatively, reflect the still insufficient knowledge of ben- thic faunas from the epoch that followed the greatest crisis in the history of life.
TL;DR: A new genus and species of Devonian tetrapod has been identified from material collected in 1947 from the southern slope of Mt. Celsius, Ymer phi, North-East Greenland.
Abstract: A new genus and species of Devonian tetrapod has been identified from material collected in 1947 from the southern slope of Mt. Celsius, Ymer phi, North-East Greenland. The specimen preserves both ...
TL;DR: Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals as discussed by the authors.
Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook-like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla–maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic (Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic.
TL;DR: A new squamate taxon is described on the basis of an articulated skeleton from the Early Cretaceous Spanish lagerstatten of Las Hoyas, which differs from other known Mesozoic lizards in combining very small body size with a short rostrum, low maxillary tooth count, a relatively slender and elongated body, and short limbs with large hind feet.
Abstract: The smallest living amniotes are all lizards, but the fossil history of this size trait in Squamata is difficult to follow because small skeletons have low preservation potential and are often hard to detect in the field. A new squamate taxon, Jucaraseps grandipes gen. et sp. nov., is here described on the basis of an articulated skeleton from the Early Cretaceous Spanish lagerstatten of Las Hoyas. It differs from other known Mesozoic lizards in combining very small body size with a short rostrum, low maxillary tooth count, a relatively slender and elongated body, and short limbs with large hind feet. Phylogenetic analysis using TNT places it on the stem of a clade encompassing scincomorphs, gekkotans, snakes, amphisbaenians and anguimorphs. Comparison with modern lizards suggests it was probably a cryptic surface or subsurface ground dweller but not a burrower.
TL;DR: The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual, and it is likely that the genus Pliosaurus will be found to include several genera.
Abstract: Complete skulls of giant marine reptiles of the Late Jurassic are rare, and so the discovery of the 1.8-m- long skull of a pliosaur from the Kimmeridge Clay Forma- tion (Kimmeridgian) of Westbury, Wiltshire, UK, is an important find. The specimen shows most of the cranial and mandibular anatomy, as well as a series of pathological conditions. It was previously referred to Pliosaurus brachy- spondylus, but it can be referred reliably only to the genus Pliosaurus, because species within the genus are currently in need of review. The new specimen, together with another from the same locality, also referred to P. brachyspondylus, will be crucial in that systematic revision, and it is likely that the genus Pliosaurus will be found to include several genera. The two Westbury Pliosaurus specimens share many features, including the form of the teeth, but marked differ- ences in the snout and parietal crest suggest sexual dimor- phism; the present specimen is probably female. The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual. An erosive arthrotic condition of the articular glenoids led to pro- longed jaw misalignment, generating a suite of associated bone and dental pathologies. Further damage to the jaw joint may have been the cause of death.
TL;DR: Morphological comparison and a cladistic analysis place Rhinodipterus crown-ward of all other Gogo lungfishes and closely related to Oervigia, Andreyevichthys and Orlovichthys.
Abstract: 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.
TL;DR: Jurassic plesiosaur fossils are exceptionally rare in Australia and currently restricted to a single fragmentary skeleton (Sinemurian, Razorback beds, Queensland), some articulated vertebrae (lower Toarcian, Evergreen Formation, Queensland) and a few isolated bones and teeth (Aalenian-Bajocian, Champion Bay Group, Western Australia).
Abstract: Jurassic plesiosaur fossils are exceptionally rare in Australia and currently restricted to a single fragmentary skeleton (Sinemurian, Razorback beds, Queensland), some articulated vertebrae (lower Toarcian, Evergreen Formation, Queensland) and a few isolated bones and teeth (Aalenian–Bajocian, Champion Bay Group, Western Australia). These remains are attributable to either indeterminate plesiosaurs, or more specifically to pliosauroids and plesiosauroids, and occur within a variety of fluviatile-lacustrine to coastal marine depositional settings. Although hampered by their incompleteness, Australia’s Jurassic plesiosaurs are significant because they include some of the most ancient occurrences from nonmarine strata, and Gondwanan marine reptiles of a similar age are otherwise very sparsely known.
TL;DR: New microstructural data reveal a unique microstructure for Sunnaginia ?
Abstract: The tommotiids are a significant component of the earliest skeletal animal remains in the fossil record, occurring in large numbers in the Lower Cambrian. Sclerites of the tommotiid genus Sunnaginia have been implicated as integral to hypotheses regarding the evolution of the brachiopod body plan, with a morphology intermediate between the unspecialized sclerites of the tubular Eccentrot- heca and the specialized sclerites of the tannuolinids. Abun- dant Sunnaginia ?imbricata sclerites, of a broad ontogenetic spectrum, were recovered from the Comley Limestone, Lower Cambrian (Stages 3-4), Shropshire, UK and compared to Sunnaginia imbricata from the Aldan River, Siberia (uppermost Tommotian). New microstructural data, collected using synchrotron radiation X-ray tomographic microscopy, reveal a unique microstructure for Sunnaginia ?imbricata sclerites among the tommotiids; interlamellar cavities spanned by a series of continuous pillars, giving a colon- naded appearance contrasting to that of S. imbricata. These data refute the inclusion of Eccentrotheca within the Sunnaginiidae and highlight the need for a revision of suprageneric classification of the tommotiids. Rather, struc- tural similarities between Sunnaginia sclerites and those of the tannuolinids suggest a close affinity to this group. Recent phylogenetic hypotheses place the tannuolinids as stem-linguliform brachiopods, with Paterimitra plus the pat- erinid (and possibly rhynchonelliform) brachiopods as their sister group. Our new data therefore resolve Sunnaginia as close to the node defining crown-Brachiopoda. However, the characters supporting this phylogenetic scheme cannot be consistently applied to all taxa, nor do they define a series of nested clades. We therefore suggest that a more thorough phylogenetic analysis is required in the light of the data presented here and other recent descriptions.
TL;DR: In this article, the authors present a re-investigation of this scorpion's anatomy and a new reconstruction, with a particular focus on the species' original habitat, showing that the scorpion was most probably terrestrial.
Abstract: Palaeoscorpius devonicus Lehmann, 1944 is known from only a single specimen, found in the Eschenbach Pit near Bundenbach in the Lower Devonian Hunsruck Slate of Germany. It is a key fossil, having been interpreted both as the most basal member of the Scorpiones and as one of the order’s most likely candidates for an aquatic mode of life. Prepared both ventrally and dorsally, some aspects of its morphology remain problematic. Here, with the aid of new techniques, including computed tomography, we present a re-investigation of this scorpion’s anatomy and a new reconstruction, with a particular focus on the species’ original habitat. On the basis of the environmental interpretation of the Hunsruck Slate and the completeness of the specimen, previous authors concluded that P. devonicus was marine, but none offered convincing morphological evidence. Recent studies of the deposit’s environment suggest that the Hunsruck Sea was part of an intrashelf basin, relatively close to the coastline, and fossils of land plants show that terrestrial wash-in occasionally occurred. Our revised interpretation of the fossil’s morphology demonstrates that the scorpion was most probably terrestrial. Internal mesosomal organs are interpreted as book lungs, but other terrestrial adaptations are lacking. The absence of both coxapophyses and gnathobases makes determining the scorpion’s feeding mechanism difficult. Interpreting the scorpion’s character states within a phylogenetic framework, especially the possible presence of book lungs, implies either that the plesiomorphic position of P. devonicus is no longer supported or that the development of book lungs had already taken place early in the scorpion lineage.
TL;DR: The comparative anatomy of Markuelia and the co-occurring palaeoscolecids shows a number of distinctions, particularly in the structure of the tail; all similarities are scalidophoran or introvertan (cyclone- uralian) symplesiomorphies.
Abstract: Three-dimensional fragments of palaeoscolecid cuticle have been recovered from the Furongian (upper Cambrian) of Hunan, South China. Extraordinary preserva- tion of the fossils shows exquisite surface details indicating a three-layered structure of the cuticle. One new genus and two new species Dispinoscolex decorus gen. et sp. nov. and Schistoscolex hunanensis sp. nov. are described. The co-occur- rence of these palaeoscolecid remains with those of Marku- elia hunanensis allowed us to test the hypothesis that Markuelia, known hitherto only from embryonic remains, is an embryonic palaeoscolecid. The comparative anatomy of Markuelia and the co-occurring palaeoscolecids shows a number of distinctions, particularly in the structure of the tail; all similarities are scalidophoran or introvertan (cyclone- uralian) symplesiomorphies. The available evidence does not support the interpretation of Markuelia as an embryonic pal- aeoscolecid.
TL;DR: Homosporous, arborescent lycopsids probably represent one of the transient forms between the Devonian herbaceous protolepidodendrids and theDevonian-Carboniferous heterosporos arb fluorescent lycopids.
Abstract: A new arborescent lycopsid, Hoxtolgaya robusta gen. et sp. nov., is described from the Middle Devonian of Xinjiang, Northwest China. It has stems up to 90 mm wide with fusiform leaf bases and long linear microphylls. Sporophylls are not aggregated into strobili and are iso- morphic, with sporangia homosporous and bearing Acinosporites-type microspores. A syndrome of characters in Hoxtolgaya, including the arborescence and the homo- spory, implies that the arborescent habit is not necessarily correlated with the heterospory in the early evolu- tion of arborescent lycopsids. Homosporous, arborescent lycopsids probably represent one of the transient forms between the Devonian herbaceous protolepidodendrids and the Devonian-Carboniferous heterosporous arborescent lycopsids.
TL;DR: The combination of derived and plesiomorphic characters in the specimen suggests its assignment to Brachiosaurus, and a brachiosaurid assignment is here suggested in base of the widely accepted monophyly of this group.
Abstract: Morphological changes in the ontogeny of sauro- pods are poorly known, making difficult to establish the sys- tematic affinities of very young individuals. New information on an almost complete juvenile sauropod (SMA 0009) with an estimated total length of about 2 m is here presented. The specimen was described as a diplodocid owing to the pres- ence of some putative synapomorphies of this group. How- ever, recent further preparation revealed the absence of diplodocid characters and the presence of macronarian derived characters. To test the affinities of this specimen, a phylogenetic analysis was conducted. The strict consensus tree recovers the specimen as a basal titanosauriform, in an unresolved relation with Brachiosaurus and Giraffatitan. Nev- ertheless, a brachiosaurid assignment is here suggested in base of the widely accepted monophyly of this group (only recovered when SMA 0009 is placed within this group). Although the existence of a new taxon cannot be completely ruled out, the combination of derived and plesiomorphic characters in the specimen suggests its assignment to Bra- chiosaurus. Sixteen extra steps are needed to place this speci- men within Diplodocidae. The high cost to place this specimen within this group is owing to the fact that several diplodocid characters are absent in SMA 0009, such as the absence of divided centroprezygapophyseal lamina in cervical vertebrae, procoelous anterior caudal centra, composed lat- eral lamina in anterior caudal vertebrae, elongated middle caudal vertebrae, short cervical ribs and caudolateral projec- tion of distal condyle of metatarsal I. Finally, the systematic position reveals few major ontogenetic transformations. These affect the pneumatic structures (e.g. change from sim- ple pleurocoels in the cervical vertebrae to complex pleuroco- els and the development of lateral excavations in the dorsal vertebrae) but also include unrecorded transformations of the neural spine (e.g. the development of the spinodiapophy- seal lamina, the widening of the neural spines in the dorsal vertebrae) and allometric growth in some limb bones.
TL;DR: Groenlandibelus rosenkrantzi from the Maastrichtian of Greenland has long been thought to constitute an early representative of spirulid coleoids, but this study shows that this view must be reassessed, at least in part.
Abstract: Groenlandibelus rosenkrantzi from the Maastrich- tian of Greenland has long been thought to constitute an early representative of spirulid coleoids. This study shows that this view must be reassessed, at least in part. A re-investigation of the types and of material recorded subse- quently has revealed that none of these specimens is conspecific with the holotype of G. rosenkrantzi. Cyrtobelus birkelundae gen. nov, sp. nov. differs from the type of G. rosenkrantzi in having lower chambers and in lacking an apically elongated sheath. The longiconic phragmocone of G. rosenkrantzi has more features in common with the pre- sumed spirulid genus Naefia. A specimen described in detail by J. A. Jeletzky in the mid 1960s as 'G. rosenkrantzi 'i s designated holotype of C. birkelundae sp. nov., which means that internal phragmocone features are still unknown in G. rosenkrantzi. Cyrtobelus hornbyense gen. nov, sp. nov. from the Campanian of western Canada constitutes the first record of early spirulids from the northeast Pacific, being based on seventeen extraordinarily well-preserved phragmo- cones. This species differs from C. birkelundae sp. nov. only in the width of the siphuncular tube. The presence of a caecum, a nacre-less conotheca that represents the continu- ation of the protoconch conotheca, conothecal flaps that anchor the mural parts of the septa, and a thin investment- like sheath are characters shared only with Recent Spirula. In particular, the unusual protoconch architecture of Cyrtobelus gen. nov. challenges a phylogenetic origin within bactritoid-like coleoids.
TL;DR: In this paper, the Bajocian-Bathonian Bemaraha Formation of western Madagascar has been used for the discovery of the first dinosaur tracks from Gondwana.
Abstract: New dinosaur tracksites are described from the Bajocian–Bathonian Bemaraha Formation of western Madagascar. Two track-bearing surfaces can be followed over a distance of at least 4 km, suggesting the existence of a hitherto unrecognized megatracksite. The track assemblage is theropod dominated, but sauropod tracks also occur at one site. Qualitative and quantitative analysis of the abundant theropod track material suggests that most, if not all, theropod footprints are attributable to a single trackmaker and are referred to Kayentapus isp. Although this ichnogenus, originally described from the Lower Jurassic of North America, has never been recorded from Gondwana nor from the Middle Jurassic, track morphology strongly suggests this attribution. Palaeogeographical, sedimentological and ichnological data suggest that the dinosaur tracks formed in an intertidal to supratidal setting where the coastline influenced the preferred walking direction of the animals.
TL;DR: These formal descriptions are the oldest for the genus and the family Oonopidae, and two new species of Orchestina are described as O. gappi sp.
Abstract: Two new species of Orchestina (Araneae: Oon- opidae) are described as O. gappi sp. nov. and O. raba- gensis sp. nov. from the Cretaceous of France and Spain, respectively. Two additional specimens from Spain are placed within Orchestina but not assigned to species. These formal descriptions are the oldest for the genus and the family Oonopidae. The discovery of these older Orchestina is not surprising, as the genus is considered a basal member of the Oonopidae and one of the most diverse and long-lived spider lineages. Two of the spiders were imaged at the European Synchrotron Radiation Facility using propagation phase-contrast X-ray synchro- tron microtomography, demonstrating once again the enormous potential of this technique for studying fossil inclusions in amber.
TL;DR: The need of a group‐specific character analysis, primarily of allometries and levels of character variation, prior to a phylogenetic reconstruction is emphasized, to suggest a genus‐level diversity among the Diomedeoididae from the Oligocene of Europe.
Abstract: Two European species of the Diomedeoididae, an extinct family of procellariiform (tube-nose) birds, have hitherto been distinguished primarily by size of their limb bones. Here, we describe an Early Oligocene (Rupelian) procellariifom coracoid that in all probability represents the larger species, Diomedeoides lipsiensis, and compare it to the coracoids of smaller diomedeoidids and extant procellarii- forms. Using multivariate (Principal Component Analysis) and univariate analyses, we demonstrate that nearly all measurements are heavily size dependent, which makes the proportions and some other shape characters of little use as phylogenetic markers. Among eight measurements, the coracoid corpus width shows the highest correlation (higher than corpus depth) with body mass, permitting a precise calculation of over twofold difference in body mass between D. lipsiensis and smaller species. Among 16 qualitative characters analysed, the majority proved too variable to be used as markers of interfamily relationships and only 2-3, the ventral intermuscular line, sternocoracoid articulation (divided vs. undivided), and, with reservations, epimarginal crest vary consistently between the families. By far the most variable is the acrocoracoid process that tends to be deeper (more elongate dorsoventrally) in larger petrels but not in the albatrosses. However, the detailed shapes of the acrocora- coid heads are highly genus specific and suggest a genus-level diversity among the Diomedeoididae from the Oligocene of Europe. The common features of the diomedeoidid coracoids are best interpreted as plesiomorphies, which accounts for some similarities to the Oceanitinae (that are probably basal among the crown-group procellariiforms). The evidence from the coracoid is consistent with a stem-group position of the Diomedeoididae as previously proposed by others. We emphasize the need of a group-specific character analysis, primarily of allometries and levels of character variation, prior to a phylogenetic reconstruction.
TL;DR: Using the results from a Bayesian relaxed molecular clock to test competing scenarios of the relationship of multiplacophorans to crown group polyplacophOrans, it is demonstrated that multiplacrophorans are stem group polylocus in which certain characters of the crown group evolved convergently.
Abstract: Multiplacophorans are Palaeozoic (Silurian to Permian) stem group polyplacophorans with 17 shell plates in a particular arrangement of single terminal plates separated by three columns of plates forming five transverse rows. Their distinctive morphology has prompted disparate interpretations of their relationship to polyplacophorans. Some features are strikingly similar to crown group polyplacophorans and even to some living families. Here we describe two Devonian forms, Protobalanus spinicoronatus sp. nov., a hercolepadid from northeast Ohio, USA, and Hannestheronia australis gen. et sp. nov., a strobilepid from South Africa. Using the results from a Bayesian relaxed molecular clock to test competing scenarios of the relationship of multiplacophorans to crown group polyplacophorans, we demonstrate that multiplacophorans are stem group polyplacophorans in which certain characters of the crown group evolved convergently.