Saturday, 24 March 2018

Charax awa: A new species of Charicid Fish from Maranhão State in northestern Brazil.

Charicids are freshwater Boney Fish related to Piranhas and Tetras that are found across South and Central America and as far north as Mexico and parts of Texas. Members of the genus Charax are medium sized members of this group, reaching a maximum of about 130 mm in length, most abundant in the Andean regions, but also found in southern and western Brazil and parts of the Guyanan Shield. No described member of this genus has a distribution that includes the coastal basins of northeastern Brazil, but there are several records of Fish apparently belonging to this group being found there. 

In a paper published in the journal Zoosystematics and Evolution on 1 February 2018, Erick Cristofore Guimarães of the Programa de Pós-Graduação em Biodiversidade e Conservação, and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Pâmella Silva De Brito of the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Beldo Rywllon Abreu Ferreira, also of the Programa de Pós-Graduação em Biodiversidade e Conservação at the Universidade Federal do Maranhão, and Felipe Polivanov Ottoni, of the Programa de Pós-Graduação em Biodiversidade e Conservação, the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia, the Laboratório de Sistemática e Ecologia de Organismos Aquáticos, and the Programa de Pós-Graduação em Oceanografia at the Universidade Federal do Maranhão, describe a new species of Charax from the Rio Mearim, Rio Munim and Rio Turiaçu basins, of Maranhão State in northestern Brazil.

The new species is named Charax awa, where ‘awa’ is the name used by the Guajá people of Maranhão State to describe themselves. Adults of this species range from 40.2 to120.0 mm in length and are silvery in colour, darker on the upper surface and towards the front, and with blotchy markings on the fins. The upper part of the head is distinctly concave, and the eyes somewhat small. The upper and lower jaws both have enlarged canine teeth as well as rows of smaller, conical teeth. 

 Charax awa, live specimen from a stream at the Miranda do Norte, in the Mearim River Basin of Maranhão State, Brazil. Erick Guimarães in Guimarães et al. (2018).

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Asteroid 2018 FD2 passes the Earth.

Asteroid 2018 FD2 passed by the Earth at a distance of about 907 000 km (2.36 times the average distance between the Earth and the Moon, or 0.61% of the distance between the Earth and the Sun), slightly after 6.35 am GMT on Saturday 17 March 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 FD2 has an estimated equivalent diameter of 8-26 m (i.e. it is estimated that a spherical object with the same volume would be 8-26 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 35 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 FD2. Minor Planet Center.

2018 FD2 was discovered on 19 March 2018 (two days after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2018 FD2 implies that it was the 54th asteroid (asteroid D2) discovered in the second half of March 2018 (period 2018 F).
2018 FD2 has a 434 day orbital period and an eccentric orbit tilted at an angle of 14.8° to the plane of the Solar System, which takes it from 0.68 AU from the Sun (i.e. 68% of he average distance at which the Earth orbits the Sun, and inside the orbit of the planet Venus) to 1.59 AU from the Sun (i.e. 159% of the average distance at which the Earth orbits the Sun, and slightly outside the orbit of the the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that 2018 EB4 has occasional close encounters with the planet Earth, with the last thought to have occurred in September 2016.

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Stictosisyra pennyi: A new species of Sisyrid Lacewing from Cretaceous Burmese Amber.

Sisyrid Lacewings, Sisyridae, are a small group of Neuropteran Insects today, with about 70 living species in four genera, mostly living in tropical areas. Based upon their relationships to other Neuropterans, Sisyrids are thought likely to be an ancient group, but they have only a limited fossil record, with six described fossil species, all from Eurasia. The oldest of these fossil species, Paradoxosisyra groehni, comes from Middle-to-Late Cretaceous Burmese Amber, from Kachin State in Myanmar, and is considered to be sufficiently different from all other known Sisyrids, living and fossil, to place it in a separate subfamily, the Paradoxosisyrinae.

In a paper published in the journal ZooKeys on 23 February 2018, Qiang Yang of the State Key Laboratory of Biocontrol at Sun Yat-sen University, the College of Life Sciences at Capital Normal University, and the Geoscience Museum at Hebei GEO University, Chaofan Shi, also of the College of Life Sciences at Capital Normal University, and the School of Earth Sciences and Engineering at Sun Yat-sen University, Dong Ren and Yongjie Wang, again of the College of Life Sciences at Capital Normal University, and Hong Pang, also of the State Key Laboratory of Biocontrol at Sun Yat-sen University, describe a second species of Sisyrid from Cretaceous Burmese Amber.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber. 

The new species is named Stictosisyra pennyi, where ‘Stictosisyra’ means ‘speckled Sisyrid’ in reference to a pattern of markings on its forewing, and ‘pennyi’ honours the late Norman Penny for his work on Lacewings and is kindness to Qiang Yang and Chaofan Shi during a visit to the California Academy of Sciences in 2016. The species is named from a single male specimen 2.9 mm in length. This specimen lacks the highly specialized mouthparts seen in Paradoxosisyra groehni, but is nevertheless thought to be more closely related to that species than to any other Sisyrid, living or fossil, and is therefore placed in the Paradoxosisyrinae.

Stictosisyra pennyi, male specimen, (A) photograph and (B) drawing. Scale bars are 1 mm. Yang et al. (2018). 

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Friday, 23 March 2018

Sinkholes swallow car and undermine building in the Centurian area of Gauteng Province, South Africa.

A series of sinkholes have opened up in the Centurian area of Gauteng Province, South Africa (between Pretoria and Midrand), following heavy rains in the area. In Valhala, on Friday 23 March 2017, Mpho Borodi, 30, drove into a sinkhole on an unlit road while on his way to work, while a second driver, had her car trapped as a sinkhole opened up beneath it. In Lyttelton a commercial building was partially undermined by another sinkhole, though the Tshwane Metro Geology Department had apparently previously warned that the building was at risk, while in Makause a number of families have been forced to evacuate their homes due to a nearby sinkhole which has put them at risk.

Car trapped in a sinkhole in Valhala, Gauteng, on 23 March 2018. Centurian Rekord.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

 Building undermined by a sinkhole in Lyttleton, Gauteng, on 22 March 2018. Centurian Rekord.

On this occasion the sinkholes have been linked to heavy rains in the area, with over 120 mm of rain recorded in Pretoria in 24 hours, which has caused a series of flash floods in Centurian, Pretoria, Johannesburg and neighbouring parts of Gauteng‚ KwaZulu-Natal and the Free State Provinces. The immediate causes of the sinkholes have not yet been determined, but it is thought that in several cases soft sediment beneath roads has been swept away after storm drains became blocked by vegetation and other debris causing water to escape into the surrounding deposits.

Flash flood in Bryanston, Gauteng, on 23 March 2018. Eyewitness News.

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Magnitude 4.7 Earthquake off the coast of Humboldt County, California.

The United States Geological Survey recorded a Magnitude 4.7 Earthquake at a depth of about 21.0 km roughly 5 km off the coast of Humboldt County, California, slightly before 8.10 pm local time on Thursday 22 March 2018 (slightly before 3.10 am on Friday 23 March GMT). There are no reports of any damage or injuries relating to this quake, but people have reported feeling it across much of northern California.

The approximate location of the 22 March 2018 Humboldt County Earthquake. USGS.

California is extremely prone to Earthquakes due to the presence of the San Andreas Fault, a tectonic plate margin that effectively bisects the state. The west of California, including Santa Barbara and Los Angeles, is located on the Pacific Plate, and is moving to the northwest. The east of California, including Fresno and Bakersfield is on the North American Plate, and is moving to the southeast. The plates do not move smoothly past one-another, but constantly stick together then break apart as the pressure builds up. This has led to a network of smaller faults that criss-cross the state, so that Earthquakes can effectively occur anywhere.

However the  22 March 2018 Earthquake happened on the southern part of the Cascadia Subduction Zone, a northward extension of the San Andreas Fault, where the Gorda Plate is being subducted beneath the North American Plate. Along this boundary the rocks of the two plates continuously stick together, then become stressed as the motion of the two plates draws them apart. This stress builds up until the rocks are forcibly snapped apart, which we experience as Earthquakes.

 Map showing the progress of the San Andreas Fault to the north, where it becomes the Gorda Plate subduction zone. Humboldt State University.

The Gorda Plate, along with the Explorer and Juan de Fuca Plates are remnants of an ancient oceanic plate, the Fallaron Plate which has almost completely disappeared beneath North America. The Fallaron Plate formerly diverged from the Pacific Plate along the Fallaron Ridge, but as the plate has been subducted both it and the ridge have broken up. The remnants of the plate are now the Explorer Plate in the north, then the Juan de Fuca Plate, then the Gorda Plate in the south. This borders onto the Pacific Plate along the Mendocino Fracture Zone, which extends on land as the San Andreas Fault.  

 North of California the San Andreas Fault becomes the Mendocino Fracture Zone. USGS.

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the USGS here.

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Caudal autotomy in Early Permian Captorhinids from Oklahoma.

Caudal autotomy is a process by which a vertebrate animal sheds its tail, or a portion of it, in order to escape from a predator. Today it is seen only in Lepidosaurs (Lizards, Snakes and the Turatura), suggesting that it is a unique innovation in this group. Caudal autotomy can occur intravertabrally (through the vertebrae), as seen in the Turatura and most Lizards, or intervertebrally, between the vertebrae, as seen in Agamid Lizards and Snakes.

In a paper published in the journal Scientific Reports on 5 March 2018, Aaron LeBlanc of the Department of Biology at the University of Toronto Mississauga, and the Department of Biological Sciences at the University of Alberta, Mark MacDougall, Yara Haridy, and Diane Scott, also of the Department of Biology at the University of Toronto Mississauga, and Robert Reisz of the Dinosaur Evolution Research Centre at Jilin University, describe evidence for the presence of caudal autotomy in Permian Captorhinids, a Eureptilian group (i.e. animals more closely related to modern Reptiles and Birds than to Mammals, but which split off from the ancestors of these modern animals long before the split between Archosauromorphs (Crocodiles, Birds and Turtles) and Lepidosaurs (Snakes, Lizards and the Turatura).

LeBlanc et al. examined 70 isolated or pairs of Captorhinid caudal (tail) vertebrae from the Royal Ontario Museum collections, obtained from the Early Permian Richards Spur locality at the Dolese Brothers Quarry in Oklahoma. They found that these had a line of weakness, which would apparently allow for caudal autotomy, with a potential line of fracture through the bottom part of the vertebrae. This appeared to be well developed in younger individuals, with the bone becoming more densely mineralised as the animals grew older, suggesting that fully mature individuals lost the ability to autotomise their tails, as is the situation in modern Iguanas.

Fracture planes in Captorhinid caudal vertebrae. (a) Artist’s reconstruction of the Permian Reptile Captorhinus with an autotomous tail (inset showing anterior caudal vertebrae with fracture planes). (b) Image and (c) SEM image of an isolated anterior caudal vertebra with a fracture plane passing through the centrum (black arrow). (d) Ventral view of an anterior, rib bearing caudal vertebra showing the absence of any fracture plane. (e) Ventral view of a caudal vertebra bearing a fracture plane (black arrows) (f) thin-section through the sagittal plane of a caudal vertebra with a fracture plane (black arrow) passing through the ventral portion of the centrum. (g) Close-up of fracture plane (black arrows) in (f) passing into the notochordal canal. Abbreviations: cb, cortical bone; cct, calcified cartilage; ce, centrum; nc, neural canal; ns, neural spine; ntc, notochordal canal. Reconstruction by Danielle Dufault. Anterior is to the left in all of the images. LeBlanc et al. (2018).

Intravertabral caudal autotomy (breaking off of the tail through the vertebrae) is generally associated with animals that can regrow their tails. No sign of any such regrowth was seen in any Captorhinid examined, though this does not necessarily imply that they were not capable of such recovery, as all of the specimens from the Richards Spur locality are isolated vertebrae rather than entire skeletons, which would make such preservation unlikely, and even were this not the case, the proportion of animals with recovering tails in the population would presumably be quite low, making the likelihood of such an animal being preserved equally low.

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Wednesday, 21 March 2018

German skier killed and Canadian injured by avalanche in French Alps.

A German skier has died after being caught in an avalanche while skiing near Grenoble in the French department of Isèreon Sunday 18 March 2018. The unnamed 25-year-old man was one of a party of five who were caught in the event when the snow gave way downslope of them. A second skier, Katie Combaluzier, 24, from Toronto, who was studying medicine in Dublin, suffered a fractured spine and other injuries in the same incident.

Katie Combaluzier, 24, from Toronto, injured by an avalache in the French Alps on 18 March 2018. CBC News.

Avalanches are caused by the mechanical failure of snowpacks; essentially when the weight of the snow above a certain point exceeds the carrying capacity of the snow at that point to support its weight. This can happen for two reasons, because more snow falls upslope, causing the weight to rise, or because snow begins to melt downslope, causing the carrying capacity to fall. Avalanches may also be triggered by other events, such as Earthquakes or rockfalls. Contrary to what is often seen in films and on television, avalanches are not usually triggered by loud noises. Because snow forms layers, with each layer typically occurring due to a different snowfall, and having different physical properties, multiple avalanches can occur at the same spot, with the failure of a weaker layer losing to the loss of the snow above it, but other layers below left in place - to potentially fail later.
Diagrammatic representation of an avalanche, showing how layering of snow contributes to these events. Expedition Earth.

The Alps have seen a number of avalanche related incidents this winter, largely due to high levels of snowfall. This is, in turn caused by warmer conditions over the Atlantic, which leads to higher rates of evaporation over the ocean, and therefore higher rates of precipitation over Europe, which falls as snow in cooler regions such as the Alps, where the moist air meets cold air fromt the east.

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