Middle Jurassic fossils document an early stage in salamander evolution.

Salamanders are an important group of living amphibians and model organisms for understanding locomotion, development, regeneration, feeding, and toxicity in tetrapods. However, their origin and early radiation remain poorly understood, with early fossil stem-salamanders so far represented by larval or incompletely known taxa. This poor record also limits understanding of the origin of Lissamphibia (i.e., frogs, salamanders, and caecilians). We report fossils from the Middle Jurassic of Scotland representing almost the entire skeleton of the enigmatic stem-salamander Marmorerpeton. We use computed tomography to visualize high-resolution three-dimensional anatomy, describing morphologies that were poorly characterized in early salamanders, including the braincase, scapulocoracoid, and lower jaw. We use these data in the context of a phylogenetic analysis intended to resolve the relationships of early and stem-salamanders, including representation of important outgroups alongside data from high-resolution imaging of extant species. Marmorerpeton is united with Karaurus, Kokartus, and others from the Middle Jurassic-Lower Cretaceous of Asia, providing evidence for an early radiation of robustly built neotenous stem-salamanders. These taxa display morphological specializations similar to the extant cryptobranchid "giant" salamanders. Our analysis also demonstrates stem-group affinities for a larger sample of Jurassic species than previously recognized, highlighting an unappreciated diversity of stem-salamanders and cautioning against the use of single species (e.g., Karaurus) as exemplars for stem-salamander anatomy. These phylogenetic findings, combined with knowledge of the near-complete skeletal anatomy of Mamorerpeton, advance our understanding of evolutionary changes on the salamander stem-lineage and provide important data on early salamanders and the origins of Batrachia and Lissamphibia.

Modes of Pangean lake level cyclicity driven by astronomical climate pacing modulated by continental position and pCO[Formula: see text].

Orbital cyclicity is a fundamental pacemaker of Earth's climate system. The Newark-Hartford Basin (NHB) lake sediment record of eastern North America contains compelling geologic expressions of this cyclicity, reflecting variations of climatic conditions in tropical Pangea during the Late Triassic and earliest Jurassic (~233 to 199 Ma). Climate modeling enables a deeper mechanistic understanding of Earth system modulation during this unique greenhouse and supercontinent period. We link major features of the NHB record to the combined climatic effects of orbital forcing, paleogeographic changes, and atmospheric pCO[Formula: see text] variations. An ensemble of transient, orbitally driven climate simulations is assessed for nine time slices, three atmospheric pCO[Formula: see text] values, and two paleogeographic reconstructions. Climatic transitions from tropical humid to more seasonal and ultimately semiarid are associated with tectonic drift of the NHB from [Formula: see text] to [Formula: see text]. The modeled orbital modulation of the precipitation-evaporation balance is most pronounced during the 220 to 200 Ma interval, whereas it is limited by weak seasonality and increasing aridity before and after this interval. Lower pCO[Formula: see text] at around 205 Ma contributes to drier climates and could have led to the observed damping of sediment cyclicity. Eccentricity-modulated precession dominates the orbitally driven climate response in the NHB region. High obliquity further amplifies summer precipitation through the seasonal shifts in the tropical rainfall belt. Regions with other proxy records are also assessed, providing guidance toward an integrated picture of global astronomical climate forcing in the Late Triassic and ultimately of other periods in Earth history.

Fossil evidence for the ancient link between clonal fragmentation, six-fold symmetry and an epizoic lifestyle in asterozoan echinoderms.

Asexual reproduction by means of splitting, also called fissiparity, is a common feature in some asterozoan groups, especially in ophiactid brittle stars. Most fissiparous brittle stars show six instead of the usual five rays, live as epibionts on host organisms, and use clonal fragmentation to rapidly colonize secluded habitats and effectively expand the margins of their distribution area. While the biology and ecology of clonal fragmentation are comparatively well understood, virtually nothing is known about the evolution and geological history of that phenomenon. Here, we describe an exceptional fossil of an articulated six-armed brittle star from the Late Jurassic of Germany, showing one body half in the process of regeneration, and assign it to the new species Ophiactis hex sp. nov. Phylogenetic inference shows that the fossil represents the oldest member of the extant family Ophiactidae. Because the Ophiactis hex specimen shows an original six-fold symmetry combined with a morphology typically found in epizoic ophiuroids, in line with recent fissiparous ophiactid relatives, we assume that the regenerating body half is an indication for fissiparity. Ophiactis hex thus shows that fissiparity was established as a means of asexual reproduction in asterozoan echinoderms by the Late Jurassic.

Middle Jurassic insect mines on gymnosperms provide missing links to early mining evolution.

We investigated the mining mode of insect feeding, involving larval consumption of a plant's internal tissues, from the Middle Jurassic (165 million years ago) Daohugou locality of Northeastern China. Documentation of mining from the Jurassic Period is virtually unknown, and results from this time interval would address mining evolution during the temporal gap of mine-seed plant diversifications from the previous Late Triassic to the subsequent Early Cretaceous. Plant fossils were examined with standard microscopic procedures for herbivory and used the standard functional feeding group-damage-type system of categorizing damage. All fossil mines were photographed and databased. We examined 2014 plant specimens, of which 27 occurrences on 14 specimens resulted in eight, new, mine damage types (DTs) present on six genera of bennettitalean, ginkgoalean, and pinalean gymnosperms. Three conclusions emerge from this study. First, these mid-Mesozoic mines are morphologically conservative and track plant host anatomical structure rather than plant phylogeny. Second, likely insect fabricators of these mines were three basal lineages of polyphagan beetles, four basal lineages of monotrysian moths, and a basal lineage tenthredinoid sawflies. Third, the nutrition hypothesis, indicating that miners had greater access to nutritious, inner tissues of new plant lineages, best explains mine evolution during the mid-Mesozoic.

Reconstruction of the pelvic girdle and hindlimb musculature of the early tetanurans Piatnitzkysauridae (Theropoda, Megalosauroidea).

Piatnitzkysauridae were Jurassic theropods that represented the earliest diverging branch of Megalosauroidea, being one of the earliest lineages to have evolved moderate body size. This clade's typical body size and some unusual anatomical features raise questions about locomotor function and specializations to aid in body support; and other palaeobiological issues. Biomechanical models and simulations can illuminate how extinct animals may have moved, but require anatomical data as inputs. With a phylogenetic context, osteological evidence, and neontological data on anatomy, it is possible to infer the musculature of extinct taxa. Here, we reconstructed the hindlimb musculature of Piatnitzkysauridae (Condorraptor, Marshosaurus, and Piatnitzkysaurus). We chose this clade for future usage in biomechanics, for comparisons with myological reconstructions of other theropods, and for the resulting evolutionary implications of our reconstructions; differential preservation affects these inferences, so we discuss these issues as well. We considered 32 muscles in total: for Piatnitzkysaurus, the attachments of 29 muscles could be inferred based on the osteological correlates; meanwhile, in Condorraptor and Marshosaurus, we respectively inferred 21 and 12 muscles. We found great anatomical similarity within Piatnitzkysauridae, but differences such as the origin of M. ambiens and size of M. caudofemoralis brevis are present. Similarities were evident with Aves, such as the division of the M. iliofemoralis externus and M. iliotrochantericus caudalis and a broad depression for the M. gastrocnemius pars medialis origin on the cnemial crest. Nevertheless, we infer plesiomorphic features such as the origins of M. puboischiofemoralis internus 1 around the "cuppedicus" fossa and M. ischiotrochantericus medially on the ischium. As the first attempt to reconstruct muscles in early tetanurans, our study allows a more complete understanding of myological evolution in theropod pelvic appendages.

Giant Jurassic dragon lacewing larvae with lacustrine palaeoecology represent the oldest fossil record of larval neuropterans.

Neuropterans seem to be less specious among holometabolans, while they are in fact the relicts of a diverse group from the Mesozoic era. Their early radiation resulted in great family level morphological heterogeneity of extant neuropterans, especially of their larvae. The earliest previously reported fossil larvae of this group were from the Early Cretaceous, where they already showed high taxonomic diversity and an extremely wide range of variations in morphotypes. In this work, the earliest record of the larva of the neuropteran Palaeoneurorthus baii gen. et sp. nov. from the Middle Jurassic Daohugou Beds of China is described. The larvae, which have large and elongated bodies, straight stylets with curved apices, an extremely elongated cervix and an extended anterior lobe of pronotum, are placed in Nevrorthidae. The elongated cervix is probably a specialized adaptation for hunting small organisms. The palaeoenvironment of these larvae indicates that larvae of Nevrorthidae have exhibited stable aquatic ecology since the Middle Jurassic, and underwent a possible shift from lakes to more lotic yet constricted modern mountain rivulet habitats over time.

Contrasting terrestrial and marine ecospace dynamics after the end-Triassic mass extinction event.

Mass extinctions have fundamentally altered the structure of the biosphere throughout Earth's history. The ecological severity of mass extinctions is well studied in marine ecosystems by categorizing marine taxa into functional groups based on 'ecospace' approaches, but the ecological response of terrestrial ecosystems to mass extinctions is less well understood due to the lack of a comparable methodology. Here, we present a new terrestrial ecospace framework that categorizes fauna into functional groups as defined by tiering, motility and feeding traits. We applied the new terrestrial and traditional marine ecospace analyses to data from the Paleobiology Database across the end-Triassic mass extinction-a time of catastrophic global warming-to compare changes between the marine and terrestrial biospheres. We found that terrestrial functional groups experienced higher extinction severity, that taxonomic and functional richness are more tightly coupled in the terrestrial, and that the terrestrial realm continued to experience high ecological dissimilarity in the wake of the extinction. Although signals of extinction severity and ecological turnover are sensitive to the quality of the terrestrial fossil record, our findings suggest greater ecological pressure from the end-Triassic mass extinction on terrestrial ecosystems than marine ecosystems, contributing to more prolonged terrestrial ecological flux.

Orbital pacing and secular evolution of the Early Jurassic carbon cycle.

Global perturbations to the Early Jurassic environment (∼201 to ∼174 Ma), notably during the Triassic-Jurassic transition and Toarcian Oceanic Anoxic Event, are well studied and largely associated with volcanogenic greenhouse gas emissions released by large igneous provinces. The long-term secular evolution, timing, and pacing of changes in the Early Jurassic carbon cycle that provide context for these events are thus far poorly understood due to a lack of continuous high-resolution δ13C data. Here we present a δ13CTOC record for the uppermost Rhaetian (Triassic) to Pliensbachian (Lower Jurassic), derived from a calcareous mudstone succession of the exceptionally expanded Llanbedr (Mochras Farm) borehole, Cardigan Bay Basin, Wales, United Kingdom. Combined with existing δ13CTOC data from the Toarcian, the compilation covers the entire Lower Jurassic. The dataset reproduces large-amplitude δ13CTOC excursions (>3‰) recognized elsewhere, at the Sinemurian-Pliensbachian transition and in the lower Toarcian serpentinum zone, as well as several previously identified medium-amplitude (∼0.5 to 2‰) shifts in the Hettangian to Pliensbachian interval. In addition, multiple hitherto undiscovered isotope shifts of comparable amplitude and stratigraphic extent are recorded, demonstrating that those similar features described earlier from stratigraphically more limited sections are nonunique in a long-term context. These shifts are identified as long-eccentricity (∼405-ky) orbital cycles. Orbital tuning of the δ13CTOC record provides the basis for an astrochronological duration estimate for the Pliensbachian and Sinemurian, giving implications for the duration of the Hettangian Stage. Overall the chemostratigraphy illustrates particular sensitivity of the marine carbon cycle to long-eccentricity orbital forcing.

The earliest known brood care in insects.

Brood care enhances offspring fitness and survival by providing protection or feeding through parents (commonly by females). It has evolved independently multiple times in animals, e.g. mammals, birds, dinosaurs and arthropods, especially various lineages of insects, and has significant implications for understanding the emergence of sociality of insects. However, few fossil insects document such an ephemeral behaviour directly. New exceptional fossils of the water boatman Karataviella popovi from the Middle-Late Jurassic Daohugou biota (ca 163.5 Ma, northeastern China), with adult females bearing clutches of eggs on their left mesotibia, provide a unique brooding strategy (asymmetric egg-carrying behaviour) unknown in all extinct and extant insects. Our discovery represents the earliest direct evidence of brood care among insects, pushing back by more than 38 million years, indicating that relevant adaptations associated with maternal investment of insects can be traced back to at least the Middle-Late Jurassic, and highlighting the existence of diverse brooding strategies in Mesozoic insects. In addition, our discovery reveals that a specialized trawl-like filter-capture apparatus of K. popovi probably represents pre-adaptions originally used for trapping coeval anostracan (fairy shrimp) eggs for food.

CO2 -induced biochemical changes in leaf volatiles decreased fire-intensity in the run-up to the Triassic-Jurassic boundary.

The Triassic-Jurassic boundary marks the third largest mass extinction event in the Phanerozoic, characterized by a rise in CO2 -concentrations from c. 600 ppm to c. 2100-2400 ppm, coupled with a c. 3.0-4.0°C temperature rise. This is hypothesized to have induced major floral turnover, altering vegetation structure, composition and leaf morphology, which in turn are hypothesized to have driven changes in wildfire. However, the effects of elevated CO2 on fuel properties, such as chemical composition of leaves, are also important in influencing fire behaviour, but yet have not been considered. We test this by selecting three Triassic analogue species grown experimentally in different atmospheric compositions, and analyse variations in leaf chemistry, and leaf level flammability. These data were used to inform a fire behaviour model. We find that all three species tested showed a reduction in their volatile component, leading to lower flammability. Accounting for these variations in a model, our results suggest that leaf intrinsic flammability has a measurable impact on modelled fire behaviour. If scaled up to ecosystem level, periods of elevated CO2 may therefore be capable of inducing both biochemical and morphological changes in fuel properties, and thus may be capable of influencing fire behaviour.

Phylogenetic revision of the lichenized family Gomphillaceae (Ascomycota: Graphidales) suggests post-K-Pg boundary diversification and phylogenetic signal in asexual reproductive structures.

We present the first broad molecular-phylogenetic revision of the lichenized family Gomphillaceae, based on 408 newly generated sequences of the mitochondrial SSU rDNA and nuclear LSU rDNA, representing 342 OTUs. The phylogenetic analysis of 20 out of the 28 currently accepted genera resulted in 48 clades. Twelve genera were resolved as monophyletic: Actinoplaca, Arthotheliopsis, Bullatina, Caleniopsis, Corticifraga, Gomphillus, Gyalectidium, Gyalidea, Jamesiella, Rolueckia, Rubrotricha, and Taitaia. Two genera resulted paraphyletic, namely Aulaxina (including Caleniopsis) and Asterothyrium (including Linhartia). Six genera were in part highly polyphyletic: Aderkomyces, Calenia, Echinoplaca, Gyalideopsis, Psorotheciopsis, and Tricharia. While ascoma morphology and anatomy has traditionally been considered as main character complex to distinguish genera, our study supported the notion that the characteristic asexual anamorph of Gomphillaceae, the so-called hyphophores, are diagnostic for most of the newly recognized clades. As a result, we recognize 26 new genus-level clades, three of which have names available (Microxyphiomyces, Psathyromyces, Spinomyces) and 23 that will require formal description as new genera. We also tested monophyly for 53 species-level names for which two or more specimens were sequenced: 27 were supported as monophyletic and representing a single species, 13 as monophyletic but with an internal topology suggesting cryptic speciation, four as paraphyletic, and nine as polyphyletic. These data suggest that species richness in the family is higher than indicated by the number of accepted names (currently 425); they also confirm that recently refined species concepts reflect species richness better than the broad concepts applied in Santesson's monograph. A divergence time analysis revealed that foliicolous Gomphillaceae diversified after the K-Pg-boundary and largely during the Miocene, a notion supported by limited data available for other common foliicolous lineages such as Chroodiscus (Graphidaceae), Pilocarpaceae, and Porinaceae. This contradicts recent studies suggesting that only macrofoliose Lecanoromycetes exhibit increased diversification rates in the Cenozoic.

Dietary niche partitioning in Early Jurassic ichthyosaurs from Strawberry Bank.

Jurassic ichthyosaurs dominated upper trophic levels of marine ecosystems. Many species coexisted alongside each another, and it is uncertain whether they competed for the same array of food or divided dietary resources, each specializing in different kinds of prey. Here, we test whether feeding differences existed between species, applying finite element analysis to ichthyosaurs for the first time. We examine two juvenile ichthyosaur specimens, referred to Hauffiopteryx typicus and Stenopterygius triscissus, from the Strawberry Bank Lagerstätte, a shallow marine environment from the Early Jurassic of southern England (Toarcian, ~183 Ma). Snout and cranial robusticity differ between the species, with S. triscissus having a more robust snout and cranium and specializing in slow biting of hard prey, and H. typicus with its slender snout specializing in fast, but weaker bites on fast-moving, but soft prey. The two species did not differ in muscle forces, but stress distributions varied in the nasal area, reflecting differences when biting at different points along the tooth row: the more robustly snouted Stenopterygius resisted increases or shifts in stress distribution when the bite point was shifted from the posterior to the mid-point of the tooth row, but the slender-snouted Hauffiopteryx showed shifts and increases in stress distributions between these two bite points. The differences in cranial morphology, dentition and inferred stresses between the two species suggest adaptations for dietary niche partitioning.

Mapping Solar System chaos with the Geological Orrery.

The Geological Orrery is a network of geological records of orbitally paced climate designed to address the inherent limitations of solutions for planetary orbits beyond 60 million years ago due to the chaotic nature of Solar System motion. We use results from two scientific coring experiments in Early Mesozoic continental strata: the Newark Basin Coring Project and the Colorado Plateau Coring Project. We precisely and accurately resolve the secular fundamental frequencies of precession of perihelion of the inner planets and Jupiter for the Late Triassic and Early Jurassic epochs (223-199 million years ago) using the lacustrine record of orbital pacing tuned only to one frequency (1/405,000 years) as a geological interferometer. Excepting Jupiter's, these frequencies differ significantly from present values as determined using three independent techniques yielding practically the same results. Estimates for the precession of perihelion of the inner planets are robust, reflecting a zircon U-Pb-based age model and internal checks based on the overdetermined origins of the geologically measured frequencies. Furthermore, although not indicative of a correct solution, one numerical solution closely matches the Geological Orrery, with a very low probability of being due to chance. To determine the secular fundamental frequencies of the precession of the nodes of the planets and the important secular resonances with the precession of perihelion, a contemporaneous high-latitude geological archive recording obliquity pacing of climate is needed. These results form a proof of concept of the Geological Orrery and lay out an empirical framework to map the chaotic evolution of the Solar System.

Paleophytogeography of the Siberian Paleofloristic Region in the Early Jurassic and First Half of the Middle Jurassic.

The results of a comparative analysis of taphofloras of the Early Jurassic and first half of the Middle Jurassic of the Siberian paleofloristic region are considered. For this time interval, a significant similarity in the systematic composition of the taphofloras of Western Siberia and Northern China is revealed. Based on the author's data and the published data, the position of the boundary in the south and southwest of the Siberian paleofloristic region and the boundary between its West Siberian and North China provinces are corrected. The refined systematic composition of paleofloras, the constant presence of numerous remains of leaves of deciduous gymnosperms in the sediments, and the sedimentological features of flora-bearing strata taken together convincingly confirm the fact that the climate throughout the entire Siberian region in the Early Jurassic and first half of the Middle Jurassic was humid with seasonal fluctuations in temperature and humidity. The paleogeographic features of the northeast of the Siberian paleofloristic region are briefly considered.

Development and evolution of the notarium in Pterosauria.

The notarium is the structure formed by fusion of the dorsal vertebrae which occurred independently in pterosaurs and birds. This ankylosis usually involves two to six elements and in many cases, also includes the last cervical vertebra. Fusion can occur in different degrees, uniting the vertebral centra, the neural spines, the transverse processes, the ventral processes, or a combination of these sites. A detailed assessment of the fusion process of pterosaur dorsal vertebrae is still lacking. Here we identify the fusion sequence of pterosaur notarial elements, demonstrating the order of ossification in vertebral bodies and neural spines based on fossils and extant birds. In both Pterosauria and Aves, the notarium generally develops in a antero-posterior direction, but the actual order of each fusion locus may present slight variations. Based on our data, we were able to identify seven developmental stages in the notarium formation, with broad implications for the prediction of ontogenetic stages for the Pterosauria. In addition, we report the occurrence of a notarium in Ardeadactylus longicollum (Kimmeridgian, Southern Germany), the oldest occurrence of this structure in pterosaurs.

Early Cretaceous abietoid Pinaceae from Mongolia and the history of seed scale shedding.

PREMISE: Seed cones of extant Pinaceae exhibit two mechanisms of seed release. In "flexers" the cone scales remain attached to the central axis, while flexing and separating from each other to release the seeds. In "shedders" scales are shed from the axis, with the seeds either remaining attached to the scale or becoming detached. The early fossil history of Pinaceae from the Jurassic to Early Cretaceous is dominated by flexing seed cones, while the systematic information provided by shedding fossil cones has been overlooked and rarely integrated with data based on compression and permineralized specimens. We describe the earliest and best-documented evidence of a "shedder" seed cone from the Aptian-Albian of Mongolia. METHODS: Lignite samples from Tevshiin Govi locality were disaggregated in water, washed, and dried in air. Fossils were compared to material of extant Pinaceae using LM and CT scans. RESULTS: Lepidocasus mellonae gen. et sp. nov. is characterized by a seed cone that disarticulated at maturity and shed obovate bract-scale complexes that have a distinctive ribbed surface and an abaxial surface covered with abundant trichomes. The ovuliferous scale has ca. 30-40 resin canals, but only scarce xylem near the attachment to the cone axis. Resin vesicles are present in the seed integument. Phylogenetic analysis places Lepidocasus as sister to extant Cedrus within the abietoid grade. CONCLUSIONS: The exquisite preservation of the trichomes in L. mellonae raises questions about their potential ecological function in the cones of fossil and living Pinaceae. Lepidocasus mellonae also shows that a shedding dispersal syndrome, a feature that has often been overlooked, evolved early in the history of Pinaceae during the Early Cretaceous.

A derived dryolestid mammal indicates possible insular endemism in the Late Jurassic of Germany.

The Langenberg Quarry near Bad Harzburg has yielded the first Jurassic stem therian mammal of Germany, recovered from Kimmeridgian (Late Jurassic) near shore deposits of a palaeo-island within the Lower Saxony Basin of the European archipelago. The new stem therian is represented by one lower and three upper molars. Hercynodon germanicus gen. et sp. nov. is attributed to the Dryolestidae, a group of pretribosphenic crown mammals that was common in western Laurasia from the Middle Jurassic to the Early Cretaceous. The new taxon is characterised by small size, a reduced cusp pattern in the upper molars lacking a metacone, and enhancement of the shearing crests paracrista and metacrista. Phylogenetic analysis identified Hercynodon gen. nov. as sister taxon of Crusafontia from the Lower Cretaceous (Barremian) of Spain. Both taxa belong to an endemic European clade of dryolestids, including also Achyrodon and Phascolestes from the earliest Cretaceous (Berriasian) of England. Despite its greater geological age, Hercynodon gen. nov. is the most derived representative of that clade, indicated by the complete reduction of the metacone. The discrepancy between derived morphology and geological age may be explained by an increased rate of character evolution in insular isolation. Other insular phenomena have earlier been observed in vertebrates from the Langenberg Quarry, such as dwarfism in the small sauropod Europasaurus, and possible gigantism in the morganucodontan mammaliaform Storchodon and the pinheirodontid multituberculate mammal Teutonodon which grew unusually large.

Thallium isotopes reveal protracted anoxia during the Toarcian (Early Jurassic) associated with volcanism, carbon burial, and mass extinction.

For this study, we generated thallium (Tl) isotope records from two anoxic basins to track the earliest changes in global bottom water oxygen contents over the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma) of the Early Jurassic. The T-OAE, like other Mesozoic OAEs, has been interpreted as an expansion of marine oxygen depletion based on indirect methods such as organic-rich facies, carbon isotope excursions, and biological turnover. Our Tl isotope data, however, reveal explicit evidence for earlier global marine deoxygenation of ocean water, some 600 ka before the classically defined T-OAE. This antecedent deoxygenation occurs at the Pliensbachian/Toarcian boundary and is coeval with the onset of initial large igneous province (LIP) volcanism and the initiation of a marine mass extinction. Thallium isotopes are also perturbed during the T-OAE interval, as defined by carbon isotopes, reflecting a second deoxygenation event that coincides with the acme of elevated marine mass extinctions and the main phase of LIP volcanism. This suggests that the duration of widespread anoxic bottom waters was at least 1 million years in duration and spanned early to middle Toarcian time. Thus, the Tl data reveal a more nuanced record of marine oxygen depletion and its links to biological change during a period of climatic warming in Earth's past and highlight the role of oxygen depletion on past biological evolution.

Hunting the Snark: the flawed search for mythical Jurassic angiosperms.

Several recent palaeobotanical studies claim to have found and described pre-Cretaceous angiosperm macrofossils. With rare exceptions, these papers fail to define a flower, do not acknowledge that fossils require character-based rather than group-based classification, do not explicitly state which morphological features would unambiguously identify a fossil as angiospermous, ignore the modern conceptual framework of phylogeny reconstruction, and infer features in the fossils in question that are interpreted differently by (or even invisible to) other researchers. This unfortunate situation is compounded by the relevant fossils being highly disarticulated two-dimensional compression-impressions lacking anatomical preservation. Given current evidence, all supposed pre-Cretaceous angiosperms are assignable to other major clades among the gymnosperms sensu lato. By any workable morphological definition, flowers are not confined to, and therefore cannot delimit, the angiosperm clade. More precisely defined character states that are potentially diagnostic of angiosperms must by definition originate on the phylogenetic branch that immediately precedes the angiosperm crown group. Although the most reliable candidates for diagnostic characters (triploid endosperm reflecting double fertilization, closed carpel, bitegmic ovule, and phloem companion cells) are rarely preserved and/or difficult to detect unambiguously, similar characters have occasionally been preserved in high-quality permineralized non-angiosperm fossils. The angiosperm radiation documented by Early Cretaceous fossils involves only lineages closely similar to extant taxonomic families, lacks obvious morphological gaps, and (as agreed by both the fossil record and molecular phylogenies) was relatively rapid-all features that suggest a primary radiation. It is unlikely that ancestors of the crown group common ancestor would have fulfilled a character-based definition of (and thereby required expansion of the concept of) an angiosperm; they would instead form a new element of the non-angiosperm members of the 'anthophyte' grade, competing with Caytonia to be viewed as morphologically determined sister group for angiosperms. Conclusions drawn from molecular phylogenetics should not be allowed to routinely constrain palaeobotanical inferences; reciprocal illumination between different categories of data offers greater explanatory power than immediately resorting to Grand Syntheses. The Jurassic angiosperm-essentially a product of molecular phylogenetics-may have become the holy grail of palaeobotany but it appears equally mythical.

The smallest eating the largest: the oldest mammalian feeding traces on dinosaur bone from the Late Jurassic of the Junggar Basin (northwestern China).

Reconstructing trophic interactions in ancient ecosystems is an important and fascinating branch of palaeontological research. Here we describe small bioerosional traces that are preserved on sauropod bone from the early Late Jurassic Qigu Formation (Oxfordian) of Liuhuanggou gorge in the southern Junggar Basin (Xinjiang Province, northwestern China). The most likely producers of these traces are tiny Mesozoic mammals as evinced by the small size of the traces as well as by their paired and opposed arrangement. The feeding traces are only superficially preserved on the bone surface and most likely were inflicted unintentionally during feeding. The occurrence of the bite marks along small ridges and the "gnawed" appearance of the bone surface points to selective feeding on the remaining soft tissues of the dinosaur carcass. The traces represent the oldest direct evidence for mammalian feeding behaviour in the fossil record. Additionally, these traces expand the known range of the early mammalian feeding repertoire significantly and shed light on the palaeobiology and palaeoecology of early mammals, a field that has remained evasive for a long time.