Friday, 21 July 2017

Understanding the relationship between ocean anoxia and porphyry formation.

Porphyry formations are igneous rocks that develop along subducting plate margins. They are rich in copper, molybdenum and gold ores, making them of great interest to geologists searching for such metals. Interestingly, almost all known porphyry deposits date from the Phanerozoic (i.e. Cambrian or younger), with such formations virtually absent from Precambrian rocks. It has been theorized that this is linked to the presence of oxygen in the deep oceans; in the presence of oxygen sulphur present in magma forms sulphate compounds; these are generally incompatible with copper, molybdenum and gold, and these metals are rapidly precipitated out of the melt, forming beds rich in these metals. However, in the absence of oxygen the sulphur is found in the form of sulphides, which react well with the metals, so that they become diffusely spread throughout the magma, never reaching concentrations at which their recovery would be economically viable. If this is the case, then porphyry deposits should also be absent from Phanerozoic deposits associated with deep-ocean anoxia.

In a paper published in the journal Geology on 1 May 2017, Jeremy Richards of the Department of Earth and Atmospheric Sciences at the University of Alberta and Celâl Şengör of the Maden Fakültesi, Jeoloji Bölümü, and Avrasya Yerbilimleri Enstitüsü at the İstanbul Teknik Üniversitesi, attempt to test this theory by examining porphyry deposits along the Tethyan Margin, an ancient subductive margin running from the Alps through Anatolia, the Caucasus and the Himalayas and on into Southeast Asia, associated with the closure of the Tethys Ocean from the Carboniferous to the Cainozoic, during which periods of both ocean oxygenation and anoxia are recorded in the sedimentary rock record.

Many porphyry deposits are known from the Tethyan Margin, though these have largely been studied by economic geologists interested in finding viable sources of copper, molybdenum and gold. Richards and Şengör collated records from a wide variety of sources, to establish the age of known porphyry deposits along the margin. They found that almost all commercially viable porphyry deposits on the Tethyan Margin were associated with the Neo-Tethyan Suture, laid down in the Cretaceous and Cainozoic, with virtually none associated with the Palaeo-Tethyan Suture, laid down in the Permian to Jurassic. 

Distribution of igneous rocks associated with Paleo-Tethyan (Permian to Jurassic) and Neo-Tethyan (Cretaceous–Cenozoic) subduction and collisional closure. Richards & Şengör (2017).

This is highly indicative, as the Palaeo-Tethyan Suture is associated with a period of prolonged deep-water anoxia in the ancient Tethys Ocean, as it was increasingly enclosed by the formation of the ancient Supercontinent of Pangea from the Carboniferous onwards, preventing ocean circulation, resulting in progressive anoxia in the deep Tethys Ocean. This reached its worst during the Late Permian, when the ocean was completely enclosed and the anoxia is known to have reached the continental shelves, leading to local extinction events in even very shallow waters. The ocean slowly recovered as Pangea broke up in the Triassic and Jurassic, leading to a return to normal ocean conditions in the Cretaceous.

Paleogeographic reconstruction of the Paleo-Tethyan ocean basin during the Late Permian. Isolation from global oceanic circulation led to anoxia and the deposition of thick sequences of reduced seafloor sediments. Richards & Şengör (2017). 

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Parababinskaia elegans: A new species of Babinskaiid Lacewing from the Early Cretaceous Crato Formation of Brazil.

The Babinskaiidae are an extinct family of Lacewings (Neuroptera) best known from the Early Cretaceous Crato Formation of Brazil, as well as from the Zaza Formation of southern Siberia and Burmese Amber deposits from Kachin State, Myanmar. They are small Lacewings, with forewings 9-12.7 mm in length, differentiated from other groups by the venation of their forewings (very few specimens have preserved hindwings).

In a paper published in the journal Cretaceous Research on 15 June 2017, Vladimir Makarkin of the Federal Scientific Center of the East Asia Terrestrial Biodiversity of the Far Eastern Branch of the Russian Academy of Sciences, Sam Heads of the Illinois Natural History Survey at the University of Illinois at Urbana-Champaign, and Sonja Wedmann of the Messel Research Station of the Senckenberg Research Institute, describe a new species of Babinskaiid Lacewing from the Crato Formation, as part of a wider review of the group.

The new species is named Parababinskaia elegans, where ‘Parababinskaia’ means ‘beside-Babinskaia’ in reference to another genus which it resembles., and ‘elegans’ means ‘elegant’, in reference to the quality of the specimen from which it is described. The species is described from a single specimen from the collection of the Illinois Natural History Survey. This specimen is preserved in a slab of finely laminated limestone, and is almost complete, lacking only the legs and detail of the forewings missing (unusually the hindwings are extremely well preserved). 

Parababinskaia elegans; specimen as preserved (wetted with ethanol). Scale bar represents 2 mm. Jared Thomas in Makarkin et al. (2017).

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Thursday, 13 July 2017

Magnitude 5.0 Earthquake to the northeast of West Nusa Tenggara, Indonesia.

The Badan Nasional Penangulanggan Bencana (Indonesia's Disaster Mitigation Agency), reported a Magnitude 5.0 Earthquake about 50 km to the northwest of the city of Bima, on West Nusa Tenggara island, at about 10.30 pm local time (about 2.30 pm GMT) on Thursday 13 July 2017. There are no reports of any damage or injuries associated with this event, though people have reported feeling it on East Nusa Tenggara Island.

The approximate location of the 13 July 2017 West Nusa Tenggara Earthquake. Google Maps.
West and East Nusa Tenggara form part of the Lesser Sunda Islands, which are located on the northern part of the Timor Microplate. This is trapped between the converging Eurasian and Australian Plates, both of which are being subducted beneath it. In the south the Australian Plate is passing under the island of Timor, with material from the subducted plate melted by the friction and the heat of the Earth's interior rising through the Timor Plate to feed the volcanoes of the island. In the north the Eurasian Plate is being subducted in the same way, feeding the volcanoes there.
The subduction zones beneath the Timor Microplate. Hamson (2004).

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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Wednesday, 12 July 2017

Aenigmatoconcha clivicola: A new species of Helicarionid Land Snail from northeastern Thailand.

Helicarionid Land Snails of the Subfamily Durgellinae are found on limestone hills across South China and Southeast Asia. There are currently two described genera in the group, with Sophina found in southern Myanmar and Chalepotaxis found across southern China and Taiwan. This disjunctive distribution would seem to imply the group has diverged through allopatric speciation (i.e. the different groups have become separated from one-another geographically, then become reproductively isolated through genetic drift), however it is equally likely to be due to poor sampling, which is to say the groups could quite possibly be present together across much of their range but not have been found to date.

In a paper published in the Raffles Bulletin of Zoology on 7 June 2017, Chanidaporn Tumpeesuwan, also of the Department of Biology at Mahasarakham University, and Sakboworn Tumpeesuwan, also of the Department of Biology and of the Palaeontological Research and Education Centre at Mahasarakham University describe a new species of Durgelline Snail from Loei Province in northeastern Thailand.

The new species is deemed sufficiently different from any previously described species to be given a new genus, Aenigmatoconcha, meaning ‘riddle-shell’, and given the specific name clivicola, meaning ‘dweller on the side of a hill’. The species has a flattened shell 7.69–9.89 mm in height and 15.40–18.62 mm in width, with 5¼–5½ whorls when fully grown and a large aperture. The shell is glassy and pale brown in colour, while the foot is darker brown. 

Aenigmatoconcha clivicola, in natural habitat. Kitti Tanmuangpak in Tumpeesuwan & Tumpeesuwan (2017).

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Fourteen feared dead after landslide in Arunachal Pradesh, India.

Fourteen people are feared to have died after a landslide hit a village in the Papum Pare District of Arunachal Pradesh State, India, on Tuesday 11 June 2017. The event occurred at about 3.30 pm local time, and burried a number of houses in the village of Latap. Fourteen people were found to be missing after the landslip, the bodies of five of whom have subsequently bee recovered. It is thought unlikely that any of the none remaining missing persons are still alive.

Rescue operations in the village of Latap in Arunachal Pradesh on Tuesday 11 July 2017. Press Trust of India.

The incident is reported to have happened after four days of continuous rain in the area, associated with the summer rainy season. Landslides are a common problem after severe weather, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. Arunchal Pradesh has a rainy season that begins around the end of April or beginning of May and ends around September, bringing 2-4000 mm of rain to the region each year.

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Sunday, 9 July 2017

Neovenator salerii: The neuroanatomy of the rostrum of an Early Cretaceous Allosauroid Dinosaur.

Neovenator salerii is an Early Cretaceous Allosauroid Theropod Dinosaur, known from a single partial skeleton from the Wessex Formation of the Isle of Wight. The skull of this skeleton is exceptionally well preserved, being deep and laterally (sideways) flattened, with blade-like teeth. This has been interpreted as indicative of a terrestrial apex predator, with a hunting technique that is likely to have involved targeting soft tissues, then defleshing with the sharp teeth, but avoiding biting down on bone or other hard tissue, which would produce wear marks on the teeth that are not seen (this is seen in some modern predators, such as Cheetahs).

In a paper published in the journal Scientific Reports on 16 June 2017, Chris Tijani Barker and Darren Naish of the National Oceanography Centre at the University of Southampton, Elis Newham and Orestis Katsamenis of the Faculty of Engineering and the Environment, also at the University of Southampton, and Gareth Dyke of the Department of Evolutionary Zoology and Human Biology at the University of Debrecen, and the Center for Interdisciplinary Biosciences at Pavol Jozef Safarik University, describe the results of a study of the cranial morphology of Neovenator salerii using microfocus μCT to investigate the distribution of its rostral foramina (the openings of channels within the bones of the snout through which nerves and blood vessels pass)and any internal preservation.

Barker et al. found that Neovenator salerii has an extensive network of channels within its maxilla and premaxilla running laterally (to the outside of) the dental alveoli, and connected to opening on the outer side of the bone. This is interpreted as part of the neurovascular system, occupying at least 7.3% and 6.7% of the internal volume of the premaxilla and maxilla, respectively. 

Complex anastomosing neurovasculature surrounding infilled dental alveoli of the premaxilla of Neovenator. (A) Volume rendering of left premaxilla in lateral view with foramina highlighted (blue). (B) Volume rendering of infilled voids. Barker et al. (2017).

Similar structures have previously been found in Pliosaurids (Mesozoic Marine Reptiles) and the Spinosaurids Spinosaurus and Baryonyx (Theropod Dinosaurs interpreted as having been partially aquatic). For this reason, the structures have been interpreted as sensory in nature, used to detect potential prey moving in the water. However, Neovenator appears to have no adaptations to an aquatic lifestyle, suggesting that the channels must have a different purpose.

Similar channels are found in a number of living animals notably some species of Birds, particularly those that engage in probe feeding, such as Kiwis (Apterygidae), Waders (Scolopacidae), and Ibises (Threskiornithidae), as well as in Ducks and Geese (Anseriformes), which use their beaks in a variety of ways for the detection, recognition, and transport of food, and Parrots (Psittaciformes), which are capable of extremely fine manipulation of objects with their beaks, including tool use. Beaks are known in a range of non-Avian Dinosaurs, including many Ornithischians and some Theropod groups, such as Ornithomimosaurs, Therizinosaurs, Oviraptorosaurs and some Ceratosaurs, but there is no evidence of any such structure in any Allosauroid, and nothing known about the biology of Neovenator suggests that it might have had a beak. 

Complex anastomosing neurovasculature surrounding infilled dental alveoli of the maxilla of Neovenator. (A) Volume rendering of left maxilla in lateral view with foramina highlighted (blue). (B) Volume rendering of infilled voids. Abbrevations: aor: antorbital ridge; asr: ascending ramus; ifs: interfenestral strut; laof: lateral antorbital fossa; maf: maxillary alveolar foramina; mcf: maxillary circumfenestra foramina; mfe: maxillary fenestra; mmf: medial maxillary foramina; pab: preantorbital body; pne: pneumatic excavation. Barker et al. (2017).

Channels of this type are also known in modern animals which lack beaks, notably Crocodylians, where it is associated with the detection potential prey moving in the water (as has been speculated for Pliosaurids and Spinosaurids), as well as temperature regulation. The very narrow snout seen in Neovanator makes a role in temperature regulation unlikely, as the snout would have shed excess heat (the only real issue for an animal this size) very efficiently without it. This makes it likely that the channels seen in the maxillary bones of Spinosaurus did indeed carry nerves rather than blood vessels. Barker et al. therefore speculate that the species, and other large Theropods such as Tyranosaurids, was probably capable of highly controlled snout movements, both when subduing prey and manipulating food, and that this would have been useful to an animal which needed to avoid brining very sharp, but not particularly strong, teeth into contact with the bone or other hard tissues of its prey.

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Pseudogobiopsis lumbantobing: A new species of freshwater Gobiid Fish from Java and Sumatra.

The freshwater Gobiid Fish genus Pseudogobiopsis is found from Thailand southeast to Papua New Guinea, though it is best known from the European aquarium trade, with collectors frequently sending professional ichthyologists photographs of unidentified species for identification.

In a paper published in the Raffles Bulletin of Zoology on 1 June 2017, Helen Larson of the Museum and Art Gallery of the Northern Territory and the Museum of Tropical Queensland, Renny Hadiaty of the Museum Zoologicum Bogoriense of the Indonesian Institute of Sciences and Nicolas Hubert of the Institut de Recherche pour le Développement, describe a new species of Pseudogobiopsis from the freshwater drainages of western Sumatra and western Java.

The new species is named Pseudogobiopsis lumbantobing, in honour of Daniel Lumbantobing of Jakarta, who collected the first specimens from the wild that were directly brought to the attention of scientists (although a number of aquarists had previously sent Helen Larson photographs of similar Fish of unknown provenance). The species is described from eighteen specimens, ranging from 18 to 33.5 mm in length, pearly grey in colour, with a with a white belly and a scattering of small orange spots. 
 Captive specimen of Pseudogobiopsis lumbantobing, imported via Singapore. Emma Turner in Larson et al. (2017).

This also potentially solves the mystery of a painting by Kuhl and van Hasselt, made between 1820 and 1823, of an unknown Gobiid Fish from Java. Unfortunately the original of this painting is in the collection of the Naturalis Library, which is currently undergoing renovation, so that the picture was in storage and unavailable for inspection prior to publication of the paper.

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