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Article Reference A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds
The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle–Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China)1–4 has challenged the pivotal position of Archaeopteryx3,4, regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians3,5. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sistergroup to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle–Late Jurassic period.
Located in Library / RBINS Staff Publications
Article Reference A Jurassic ornithischian dinosaur from Siberia with both feathers and scales
Middle Jurassic to Early Cretaceous deposits from northeastern China have yielded varied theropod dinosaurs bearing feathers. Filamentous integumentary structures have also been described in ornithischian dinosaurs, but whether these filaments can be regarded as part of the evolutionary lineage toward feathers remains controversial. Here we describe a new basal neornithischian dinosaur from the Jurassic of Siberia with small scales around the distal hindlimb, larger imbricated scales around the tail, monofilaments around the head and the thorax, and more complex featherlike structures around the humerus, the femur, and the tibia.The discovery of these branched integumentary structures outside theropods suggests that featherlike structures coexisted with scales and were potentially widespread among the entire dinosaur clade; feathers may thus have been present in the earliest dinosaurs.
Located in Library / RBINS Staff Publications
Article Reference A juvenile skull from the early Palaeocene of China extends the appearance of crocodyloids in Asia back by 15–20 million years
The earliest Crocodylia from Asia have been represented so far only by alligatoroids and planocraniids. Although definitive crocodyloids are not known until the late Eocene, it has been hypothesized that Asiatosuchus-like basal crocodyloids originated in Asia before the late Palaeocene. In this paper, we describe a new fossil crocodyloid from the lower Palaeocene of Qianshan Basin, Anhui Province, China. The skull and lower jaw fragment exhibit several characteristics typical of juvenile crocodylians. They also display a combination of features not seen in any other taxon, warranting the erection of a new species and genus, Qianshanosuchus youngi gen. & sp. nov. Its affinities are tested in phylogenetic analyses based on two recent character matrices of Eusuchia. To assess the effect of juvenile characteristics on the outcome of the phylogenetic analyses, juvenile specimens of extant crocodylian taxa are analysed in the same way, showing that the effect of their ontogenetic stage on their placement in the tree is minimal. Our analyses point to a basal crocodyloid position for Q. youngi. With these findings, the presence of Crocodyloidea in Asia is extended to the early Palaeocene, 15–20 Myr earlier than formerly thought. Furthermore, our results corroborate previous hypotheses of a Palaeocene dispersal route of Asiatosuchus-like crocodyloids from Asia into Europe.
Located in Library / RBINS Staff Publications 2022 OA
Article Reference A Karethraichnus boring on a turtle shell bone from the Miocene of Italy is assessed as the attachment scar of a platylepadid symbiont
Among the turtle and whale barnacles, those included in the family Platylepadidae are mostly found partly embedded in the carapace and plastron of sea turtles. As a likely consequence of their fragile shell, the fossil record of these cirripede epizoans of marine chelonians is currently limited to two occurrences of Platylepas in Pleistocene strata. Here, we describe and refer to Karethraichnus cf. lakkos an isolated boring on a fossil cheloniid costal plate from the upper Miocene Arenaria di Ponsano Formation of Tuscany (central Italy). A scrutiny of palaeontological and neontological literature as well as new first-hand observations reveal that this boring was most likely produced by a platylepadid barnacle similar to Stomatolepas, Stephanolepas or Platylepas. Two other probable platylepadid attachment scars, both of which incise cheloniid shell bones, are noted from the Oligocene and Miocene, respectively. On the whole, these scanty data support the hypothesis that platylepadids have ancient evolutionary roots and a long story of symbiosis with sea turtles. Future research efforts in this field should focus on 1) further investigating the potential of bone damage of turtle-dwelling barnacles; 2) initiating a methodical quest for possible platylepadid attachment scars in Cenozoic marine turtle fossils; and 3) replenishing the still fragmentary Palaeogene fossil record of Coronuloidea.
Located in Library / RBINS Staff Publications 2022
Article Reference A land micro-mammal fauna from the Early Eocene marine Egem deposits (NP12, Belgium) and the first occurrence of the peradectid marsupial Armintodelphys outside North America
Dental remains of land mammals are sometimes discovered in shallow marine Paleogene deposits of the North Sea Basin. Such is the case for eleven specimens we describe here from the Early Eocene Egemkapel Clay Member in the middle part of the Tielt Formation, found in Ampe quarry at Egem in Northwestern Belgium. The small fauna consists of 6 taxa, including the neoplagiaulacid multituberculate Ectypodus, the erinaceomorph insectivore Macrocranion, the nyctitheriid Leptacodon, an eochiropteran bat possibly belonging to a palaeochiropterygid, an unidentified perissodactyl possibly belonging to an equoid, and a new species of the peradectid marsupial Armintodelphys. The latter represents the first European occurrence of the genus, which was previously only known from the North American late Early and early Middle Eocene of the Wind River and Green River basins in Wyoming and the Uinta Basin in Utah. Biogeographic and biostratigraphic analyses of peradectid marsupials suggest that Armintodelphys dispersed between North America and Europe around the time of the Early Eocene Climatic Optimum. The Egemkapel Clay Member has been dated as middle NP12, early late Ypresian, whereas the Egem mammal fauna can be correlated to the fauna of Avenay from the Paris Basin, which is the international reference-level MP8+9 of the mammalian biochronological scale for the European Paleogene.
Located in Library / RBINS Staff Publications
Article Reference A land snail's view of a fragmented landscape
Habitat fragmentation may influence the genetic structure of populations, especially of species with low mobility. So far, these effects have been mainly studied by surveying neutral markers, and much less by looking at ecologically relevant characters. Therefore, we aimed to explore eventual patterns of covariation between population structuring in neutral markers and variation in shell morphometrics in the forest-associated snail Discus rotundatus in relation to habitat fragment characteristics. To this end, we screened shell morphometric variability and sequence variation in a fragment of the mitochondrial 16S rDNA gene in D. rotundatus from the fragmented landscape of the Lower Rhine Embayment, Germany. The 16S rDNA of D. rotundatus was highly variable, with a total of 118 haplotypes (384 individuals) forming four clades and one unresolved group. There was a geographic pattern in the distribution of the clades with the river Rhine apparently separating two groups. Yet, at the geographic scale considered, there was no obvious effect of fragmentation on shell morphometrics and 16S rDNA variation because G(ST) often was as high within, as between forests. Instead, the age of the habitat and (re-)afforestation events appeared to affect shell shape and 16S rDNA in terms of the number of clades per site. The ecologically relevant characters thus supported the presumably neutral mitochondrial DNA markers by indicating that populations of not strictly stenecious species may be (relatively) stable in fragments. However, afforestation after large clearcuts and habitat gain after the amendment of deforestation are accompanied by several, seemingly persistent peculiarities, such as altered genetic composition and shell characters (e.g. aperture size). (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 839-850.
Located in Library / RBINS Staff Publications
Article Reference A large Late Miocene cetotheriid (Cetacea, Mysticeti) from the Netherlands clarifies the status of Tranatocetidae
Located in Library / RBINS Staff Publications 2019
Article Reference A large meteoritic event over Antarctica ca. 430 ka ago inferred from chondritic spherules from the Sør Rondane Mountains
Large airbursts, the most frequent hazardous impact events, are estimated to occur orders of magnitude more frequently than crater-forming impacts. However, finding traces of these events is impeded by the difficulty of identifying them in the recent geological record. Here, we describe condensation spherules found on top of Walnumfjellet in the Sør Rondane Mountains, Antarctica. Affinities with similar spherules found in EPICA Dome C and Dome Fuji ice cores suggest that these particles were produced during a single-asteroid impact ca. 430 thousand years (ka) ago. The lack of a confirmed crater on the Antarctic ice sheet and geochemical and 18O-poor oxygen isotope signatures allow us to hypothesize that the impact particles result from a touchdown event, in which a projectile vapor jet interacts with the Antarctic ice sheet. Numerical models support a touchdown scenario. This study has implications for the identification and inventory of large cosmic events on Earth.
Located in Library / RBINS Staff Publications 2021
Article Reference A large new collection of Palaeostylops from the Paleocene of the Flaming Cliffs area (Ulan-Nur Basin, Gobi Desert, Mongolia), and an evaluation of the phylogenetic affinities of Arctostylopidae (Mammalia, Gliriformes)
Arctostylopids are enigmatic mammals known from the Paleocene and early Eocene of Asia and North America. Based on molar similarities, they have most often been grouped with the extinct Notoungulata from South and Central America, but tarsal evidence links them to Asian basal gliriforms. Although Palaeostylops is the best known arctostylopid genus, some points of its content and species level taxonomy are uncertain. Here we report 255 upper and lower jaw fragments of Palaeostylops, five calcanea, three astragali, as well as the first known arctostylopid distal tibia. This new material was collected from the late Paleocene of the Flaming Cliffs area in Mongolia, in a single lens almost exclusively containing arctostylopid remains. Our study of the morphology and size of the new Palaeostylops dental material confirms the validity of two species, P. iturus and P. macrodon, and illustrates their morphological and biometrical variability and diagnostic differences. The distal tibia of Palaeostylops is relatively unspecialised and resembles the Asian gliriforms Pseudictops and Rhombomylus. We also review the relevance of the historically important genus Palaeostylops in view of other, more recently described but less abundant arctostylopid genera. Palaeostylops remains the reference taxon for the arctostylopid anterior dentition and postcranial morphology. For both anatomical regions, arctostylopids differ significantly from notoungulates, and present a mosaic of characters also seen in basal gliriforms. The notoungulate-like molars of Palaeostylops are highly specialized for arctostylopids and the arctostylopid molar morphotype is therefore better illustrated by the early middle Paleocene Asiostylops. This morphotype does not present any similarities to notoungulates, but shares a number of derived characters with basal gliriforms. Among gliriforms, the primitive arctostylopid morphotype is most similar to Astigale from the early Paleocene of South China, and we suggest that Arctostylopidae may therefore be more closely related to Astigalidae than to any other group.
Located in Library / RBINS Staff Publications
Article Reference A Late Devonian refugium for Colpodexylon (Lycopsida) at high latitude
Located in Library / RBINS Staff Publications 2021