A new Groenlandaspidid Arthrodire (Vertebrata: Placodermi) from the Famennian of Belgium

A new species of the arthrodire genus Groenlandaspis is described from the upper part of the Evieux Formation (Upper Famennian), based on several specimens collected from quarries at Modave and Villers-le-Temple,Liège Province, Belgium. It is the first occurrence of this widespread genus in continental Europe. This new species is characterized by an almost smooth dermal armour, except for some scattered tubercles on its skull roof, median dorsal and spinal plates. Its median dorsal plate is triangular in shape and almost perfectly equilateral in lateral aspect and bears large, spiniform denticles on its posterior edge. All these Groenlandaspis remains occur in micaceous, dolomitic claystones or siltstones probably deposited in a subtidal environment. Outcrops of the same area have yielded other vertebrate remains, such as the placoderms Phyllolepis and Bothriolepis, acanthodians, various piscine sarcopterygians (Holoptychius, dipnoans, a rhizodontid, Megalichthys, Eusthenodon and a large tristichopterid), and a tetrapod that is probably close to Ichthyostega. The biogeographical history of the genus Groenlandaspis is briefly outlined, and the late Frasnian-Famennian interchange of vertebrate taxa between Gondwana and Euramerica is discussed

Electric current in flares ribbons: observations and 3D standard model

We present for the first time the evolution of the photospheric electric currents during an eruptive X-class flare, accurately predicted by the standard 3D flare model. We analyze this evolution for the February 15, 2011 flare using HMI/SDO magnetic observations and find that localized currents in \J-shaped ribbons increase to double their pre-flare intensity. Our 3D flare model, developed with the OHM code, suggests that these current ribbons, which develop at the location of EUV brightenings seen with AIA imagery, are driven by the collapse of the flare's coronal current layer. These findings of increased currents restricted in localized ribbons are consistent with the overall free energy decrease during a flare, and the shape of these ribbons also give an indication on how much twisted the erupting flux rope is. Finally, this study further enhances the close correspondence obtained between the theoretical predictions of the standard 3D model and flare observations indicating that the main key physical elements are incorporated in the model.Comment: 12 pages, 7 figure

A New Paleozoic Symmoriiformes (Chondrichthyes) from the Late Carboniferous of Kansas (USA) and Cladistic Analysis of Early Chondrichthyans

BACKGROUND: The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians) into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters. METHODOLOGY/PRINCIPAL FINDINGS: On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii) form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters. CONCLUSIONS/SIGNIFICANCE: Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters

Slipping magnetic reconnection during an X-Class solar flare observed by SDO/AIA

We present SDO/AIA observations of an eruptive X-class flare of July 12, 2012, and compare its evolution with the predictions of a 3D numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the AIA 131A observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km/s along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A DEM analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a CME observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the "standard solar flare model in 3D". This model matches the observations well, reproducing both the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour

Diversité, impacts et usages des Loranthaceae parasites de Cola nitida (Vent.) Schott. & Endl. au Sud-Bénin

Cola nitida est une espèce fruitière à usages multiples qui, malheureusement, est souvent la cible des plantes parasites de la famille des Loranthaceae. L’objectif de la présente étude est de recenser les espèces de Loranthaceae parasites de C. nitida, d’évaluer leur impact sur ce fruitier et d’inventorier les usages thérapeutiques faits de ces plantes parasites au Sud du Bénin. Pour y parvenir, des inventaires floristique et forestier puis des enquêtes ethnobotaniques ont été réalisés. Au total, 15 plantations et 50 jardins de case abritant C. nitida ont été explorés dans 12 villages à travers lesquels 87 personnes utilisant les Loranthaceae ont été questionnées. Les résultats révèlent que sur les 552 pieds de C. nitida explorés, 6 espèces de Loranthaceae qui sont : Globimetula braunii, G. cupulata, Phragmanthera capitata, Tapinanthus bangwensis, T. belvisii et T. globiferus ont été recensées. Le taux d’infestation est de 53%. Sur le plan ethnobotanique, les Loranthaceae de C. nitida interviennent dans le traitement de 3 affections que sont : la stérilité, les fausses couches (40% chacune) et les troubles menstruels (20%). Cette étude permet de proposer l’utilisation à grande échelle des Loranthaceae comme approche de gestion durable de ces hémiparasites.© 2015 International Formulae Group. All rights reserved.Mots clés: Gui africain, biodiversité, densité parasitaire, gestion durable, BéninEnglish Title: Diversity, impacts and uses of Loranthaceae growing on Cola nitida (Vent.) Schott. & Endl. in Southern BeninEnglish AbstractCola nitida is a kind of fruit presenting international multiple uses. However, this fruit is often the target of parasitic plants of Loranthaceae family. The aim of the present work is to know the diversity and  impact of Loranthaceae on C. nitida tree and the different uses made of these parasites. A total of 552 feet of C. nitida have been explored within 15 plantations and 50 home gardens spread in 12 villages through which 87 people using Loranthaceae have been questioned. The results show that C. nitida is parasitized by 6 species of Loranthaceae (Globimetula braunii, G. cupulata, Phragmanthera capitata, Tapinanthus bangwensis, T. belvisii and T. globiferus). Infestation rate of C. nitida is 53%. On ethnobotanical level, Loranthaceae growing on C. nitida contribute to the treatment of three diseases which are barrenness, miscarriage (40% each) and menstrual disorders (20%). Pending the development of effective struggle methods against Loranthaceae growing on C. nitida, the widespread use of these parasites can contribute to maintain them in acceptable damage threshold and also generate incomes for people.© 2015 International Formulae Group. All rights reserved.Keywords: African mistletoes, biodiversity, parasite density, sustainable management, Beni

Student perspectives on the relationship between a curve and its tangent in the transition from Euclidean Geometry to Analysis

The tangent line is a central concept in many mathematics and science courses. In this paper we describe a model of students’ thinking – concept images as well as ability in symbolic manipulation – about the tangent line of a curve as it has developed through students’ experiences in Euclidean Geometry and Analysis courses. Data was collected through a questionnaire administered to 196 Year 12 students. Through Latent Class Analysis, the participants were classified in three hierarchical groups representing the transition from a Geometrical Global perspective on the tangent line to an Analytical Local perspective. In the light of this classification, and through qualitative explanations of the students’ responses, we describe students’ thinking about tangents in terms of seven factors. We confirm the model constituted by these seven factors through Confirmatory Factor Analysis

Early fossils illuminate character evolution and interrelationships of Lampridiformes (Teleostei, Acanthomorpha)

Lampridiformes is a peculiar clade of pelagic marine acanthomorph (spiny-rayed) teleosts. Its phylogenetic position remains ambiguous, and varies depending on the type of data (morphological or molecular) used to infer interrelationships. Because the extreme morphological specializations of lampridiforms may have overwritten the ancestral features of the group with a bearing on its relationships, the inclusion of fossils that exhibit primitive character state combinations for the group as a whole is vital in establishing its phylogenetic position. Therefore, we present an osteological data set of extant (ten taxa) and fossil (14 taxa) acanthomorphs, including early Late Cretaceous taxa for which a close relationship with extant Lampridiformes has been suggested: †Aipichthyoidea, †Pharmacichthyidae, and †Pycnosteroididae. We find that all three taxa plus Lampridiformes form a clade that we call Lampridomorpha. Under this hypothesis, †Aipichthyoidea is paraphyletic. The inclusion of fossils in the analysis changes the topology, highlighting their critical importance in phylogenetic studies of morphological characters. When fossils are included, Lampridomorpha is sister to Euacanthomorpha (all other extant acanthomorphs), concurring with most previous anatomical studies, but conflicting with most molecular results. Lampridomorpha as a whole was a major component of the earliest acanthomorph faunas, notably in the Cenomanian

Diversité Des Loranthaceae Et Leur Impact Sur Vitellaria Paradoxa C.F.Gaertn.: Un Fruitier À Grande Valeur Socio-Économique Au Nord-Bénin

Shea butter: Vitellaria paradoxa C. F. Gaertn (Sapotaceae) is a fruit tree in the Sudano-Sahelian region where it is a major economic source. Unfortunately, in Benin, the species has been revealed in recent decades, the target of parasitic vascular plants of Loranthaceae family that threaten its conservation. The present study, carried out in northern Benin, evaluated the impact of these parasitic plants on the shea of two phytogeographical zones. The botanical inventory identified three species of Loranthaceae in fields and protected areas. The rate of infestation and parasite density were assessed and their variation on shea was assessed. The results show that shea is parasitized by three species of Loranthaceae in varying proportions: Agelanthus dodoneifolius (DC.) Polh. and Wiens (191.75 tufts / ha), Tapinanthus globiferus (A. Rich.) Van Tieghem (70.57 tufts / ha) and T. Ophiodes (Sprague) (2 tufts / ha). The impact of Loranthaceae on shea productivity varies significantly between fields and protected areas with infestation rates of 87% versus 42% and average densities per shea foot of 14.76 tufts versus 3.62 tufts. These results are data to be taken into account in the control programs against Loranthaceae which parasitize shea

The dermal skeleton of the jawless vertebrate Tremataspis mammilata (Osteostraci, stem-Gnathostomata)

Osteostracans are the closest jawless relatives of jawed vertebrates, informing the gradual assembly of the vertebrate mineralised skeleton. Conflicting interpretations of their dermal skeletal histology arise from failure to account for topological variation, obscuring their significance in elucidating vertebrate skeletal evolution. To resolve this, we characterize the cranial and trunk dermal skeleton of a single individual of Tremataspis mammilata (Osteostraci, Thyestiida) at submicron resolution using synchrotron tomography. Our results show that the architecture of the Tremataspis dermal skeleton is, for the most part, conserved over the skeleton and is broadly consistent with previous histological hypotheses based on 2-dimensional thin section study. We resolve debate over the homology of the basal layer, identifying it as osteogenic acellular isopedin rather than odontogenic elasmodine or metaplastic ossification of the stratum compactum of the dermis. We find topological variation between all dermal skeletal elements studied, and particularly between the cranial and postcranial dermal skeleton. This variation can be largely explained by reduction in differentiation due to geometric constraints imposed within smaller skeletal elements, such as scales. Our description of the dermal skeleton of Tremataspis mammilata provides a foundation for interpreting data from cursory topological samples of dermal skeletal diversity obtained in other osteostracans. This reveals general aspects of histological structure that must be primitive for osteostracans and, likely, ancestral jawed vertebrates. Finally, we draw the distinction between hypotheses and descriptions in palaeohistology