• Ancient hydrothermal seafloor deposits in Eridania basin on Mars

      Michalski, JR; Dobrea, EZN; Niles, PB; Cuadros, J (2017-07-10)
    • Climate-mediated diversification of turtles in the Cretaceous

      Nicholson, DB; Holroyd, PA; Benson, RBJ; Barrett, PM (2015-12)
    • Exites in Cambrian arthropods and homology of arthropod limb branches

      Liu, Yu; Edgecombe, GD; Schmidt, Michel; Bond, Andrew D; Melzer, Roland R; Zhai, Dayou; Mai, Huijuan; Zhang, Maoyin; Hou, Xianguang (Springer Science and Business Media LLC, 2021-04-01)
      Abstract: The last common ancestor of all living arthropods had biramous postantennal appendages, with an endopodite and exopodite branching off the limb base. Morphological evidence for homology of these rami between crustaceans and chelicerates has, however, been challenged by data from clonal composition and from knockout of leg patterning genes. Cambrian arthropod fossils have been cited as providing support for competing hypotheses about biramy but have shed little light on additional lateral outgrowths, known as exites. Here we draw on microtomographic imaging of the Cambrian great-appendage arthropod Leanchoilia to reveal a previously undetected exite at the base of most appendages, composed of overlapping lamellae. A morphologically similar, and we infer homologous, exite is documented in the same position in members of the trilobite-allied Artiopoda. This early Cambrian exite morphology supplements an emerging picture from gene expression that exites may have a deeper origin in arthropod phylogeny than has been appreciated.
    • Increasing species sampling in chelicerate genomic-scale datasets provides support for monophyly of Acari and Arachnida.

      Lozano-Fernandez, Jesus; Tanner, AR; Giacomelli, M; Carton, Robert; Vinther, Jakob; Edgecombe, GD; Pisani, Davide (Nature Publishing Group, 2019-05-24)
      Chelicerates are a diverse group of arthropods, represented by such forms as predatory spiders and scorpions, parasitic ticks, humic detritivores, and marine sea spiders (pycnogonids) and horseshoe crabs. Conflicting phylogenetic relationships have been proposed for chelicerates based on both morphological and molecular data, the latter usually not recovering arachnids as a clade and instead finding horseshoe crabs nested inside terrestrial Arachnida. Here, using genomic-scale datasets and analyses optimised for countering systematic error, we find strong support for monophyletic Acari (ticks and mites), which when considered as a single group represent the most biodiverse chelicerate lineage. In addition, our analysis recovers marine forms (sea spiders and horseshoe crabs) as the successive sister groups of a monophyletic lineage of terrestrial arachnids, suggesting a single colonisation of land within Chelicerata and the absence of wholly secondarily marine arachnid orders.
    • A new Middle Jurassic diplodocoid suggests an earlier dispersal and diversification of sauropod dinosaurs

      Xu, X; Upchurch, P; Mannion, PD; Barrett, PM; Regalado-Fernandez, OR; Mo, J; Ma, J; Liu, H (2018-07-24)
    • New Permian fauna from tropical Gondwana

      Cisneros, JC; Marsicano, C; Angielczyk, KD; Smith, RMH; Richter, M; Fröbisch, J; Kammerer, CF; Sadleir, RW (2015-12)
    • Ontogeny of the maxilla in Neanderthals and their ancestors

      Lacruz, RS; Bromage, TG; O’Higgins, P; Arsuaga, J-L; Stringer, C; Godinho, RM; Warshaw, J; Martínez, I; Gracia-Tellez, A; de Castro, JMB; et al. (Springer Science and Business Media LLC, 2015-12-07)
      Neanderthals had large and projecting (prognathic) faces similar to those of their putative ancestors from Sima de los Huesos (SH) and different from the retracted modern human face. When such differences arose during development and the morphogenetic modifications involved are unknown. We show that maxillary growth remodelling (bone formation and resorption) of the Devil’s Tower (Gibraltar 2) and La Quina 18 Neanderthals and four SH hominins, all sub-adults, show extensive bone deposition, whereas in modern humans extensive osteoclastic bone resorption is found in the same regions. This morphogenetic difference is evident by ∼5 years of age. Modern human faces are distinct from those of the Neanderthal and SH fossils in part because their postnatal growth processes differ markedly. The growth remodelling identified in these fossil hominins is shared with Australopithecus and early Homo but not with modern humans suggesting that the modern human face is developmentally derived.
    • Re-evaluating the phylogenetic position of the enigmatic early Cambrian deuterostome Yanjiahella

      Zamora, Samuel; Wright, David F; Mooi, Rich; Lefebvre, Bertrand; Guensburg, Thomas E; Gorzelak, Przemysław; David, Bruno; Sumrall, Colin D; Cole, Selina R; Hunter, Aaron W; et al. (Springer Science and Business Media LLC, 2020-03-09)
    • Reconstruction of the diapsid ancestral genome permits chromosome evolution tracing in avian and non-avian dinosaurs

      O'Connor, RE; Romanov, MN; Kiazim, LG; Barrett, PM; Farré, M; Damas, J; Ferguson-Smith, M; Valenzuela, N; Larkin, DM; Griffin, DK (2018-05-21)
    • Reptile-like physiology in Early Jurassic stem-mammals

      Newham, E; Gill, Pamela; Brewer, Philippa; Benton, MJ; Fernandez, Vincent; Gostling, NJ; Haberthür, D; Jernvall, J; Kankaanpää, T; Kallonen, A; et al. (Springer Science and Business Media LLC, 2020-10-12)
      Despite considerable advances in knowledge of the anatomy, ecology and evolution of early mammals, far less is known about their physiology. Evidence is contradictory concerning the timing and fossil groups in which mammalian endothermy arose. To determine the state of metabolic evolution in two of the earliest stem-mammals, the Early Jurassic Morganucodon and Kuehneotherium, we use separate proxies for basal and maximum metabolic rate. Here we report, using synchrotron X-ray tomographic imaging of incremental tooth cementum, that they had maximum lifespans considerably longer than comparably sized living mammals, but similar to those of reptiles, and so they likely had reptilian-level basal metabolic rates. Measurements of femoral nutrient foramina show Morganucodon had blood flow rates intermediate between living mammals and reptiles, suggesting maximum metabolic rates increased evolutionarily before basal metabolic rates. Stem mammals lacked the elevated endothermic metabolism of living mammals, highlighting the mosaic nature of mammalian physiological evolution.
    • Sequestration of Martian CO2 by mineral carbonation

      Tomkinson, T; Lee, MR; Mark, DF; Smith, CL (Springer Science and Business Media LLC, 2013-10-22)
      Carbonation is the water-mediated replacement of silicate minerals, such as olivine, by carbonate, and is commonplace in the Earth’s crust. This reaction can remove significant quantities of CO2 from the atmosphere and store it over geological timescales. Here we present the first direct evidence for CO2 sequestration and storage on Mars by mineral carbonation. Electron beam imaging and analysis show that olivine and a plagioclase feldspar-rich mesostasis in the Lafayette meteorite have been replaced by carbonate. The susceptibility of olivine to replacement was enhanced by the presence of smectite veins along which CO2-rich fluids gained access to grain interiors. Lafayette was partially carbonated during the Amazonian, when liquid water was available intermittently and atmospheric CO2 concentrations were close to their present-day values. Earlier in Mars’ history, when the planet had a much thicker atmosphere and an active hydrosphere, carbonation is likely to have been an effective mechanism for sequestration of CO2.
    • Sustained fluvial deposition recorded in Mars’ Noachian stratigraphic record

      Salese, F; McMahon, WJ; Balme, MR; Ansan, V; Davis, Joel; Kleinhans, MG (Springer Science and Business Media LLC, 2020-05-05)
      Orbital observation has revealed a rich record of fluvial landforms on Mars, with much of this record dating 3.6–3.0 Ga. Despite widespread geomorphic evidence, few analyses of Mars’ alluvial sedimentary-stratigraphic record exist, with detailed studies of alluvium largely limited to smaller sand-bodies amenable to study in-situ by rovers. These typically metre-scale outcrop dimensions have prevented interpretation of larger scale channel-morphology and long-term basin evolution, vital for understanding the past Martian climate. Here we give an interpretation of a large sedimentary succession at Izola mensa within the NW Hellas Basin rim. The succession comprises channel and barform packages which together demonstrate that river deposition was already well established >3.7 Ga. The deposits mirror terrestrial analogues subject to low-peak discharge variation, implying that river deposition at Izola was subject to sustained, potentially perennial, fluvial flow. Such conditions would require an environment capable of maintaining large volumes of water for extensive time-periods, necessitating a precipitation-driven hydrological cycle.
    • Taking the pulse of Mars via dating of a plume-fed volcano

      Cohen, BE; Mark, DF; Cassata, WS; Lee, MR; Tomkinson, T; Smith, CL (2017-12)