Could the 1908 Tunguska Event have been caused by an extra-terrestrial body passing through the Earth's atmosphere without impacting?

On 30 June 1908 a explosion near the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Siberia, flattened around 80 million trees over an area of about 2150 km², and is thought to have killed at least three people. The cause of this is unclear; the most possible current explanation is that a stony meteorite with a diameter of about 100 m exploded in an airburst 5-10 km above the ground, although no debris from such an event has ever been found, which is surprising. Since the Chelyabinsk meteor impact of February 2013, when a meteor estimated to have been 20 m in size passed over the city of Chelyabinsk, creating a shockwave that caused considerable damage on the ground, before breaking up to the west of the city, it has been clear that a bolide passint through the Earth's atmosphere could cause considerable damage on the ground, even without impacting or detonating in an airburst. 

In a paper published in the Monthly Nottices of the Royal Astronomical Society on 4 February 2020, Daniil Khrennikov of the Siberian Federal University, Andrei Titov of the Moscow Institute of Physics and Technology, Alexander Ershov, also of the Siberian Federal University, and of the Institute of Computational Modeling, Vladimir Pariev of the PN Lebedev Physical Institute, and Sergei Karpov, again of the Siberian Federal University, and also the LV Kirensky Institute of Physics and the Siberian State University of Science and Technology, examine the possibility of through passage of asteroid bodies across the Earth’s atmosphere, and the likelyhood that this might have caused the damage associated with the 1908 Tunguska Event.

Fallen trees in the aftermath of the 1908 Tunguska Event. Leonid Kulik.

The problem of the motion in the Earth’s atmosphere of a large bolide, capable of falling on to the surface of the planet in the form of meteorites, is now of great interest. An equally urgent concern is the study of the conditions for the passage of such bodies through the upper atmosphere, even without collision with the Earth’s surface, since the shockwaves produced by this passage have a colossal destructive effect.

Large bolides (1–10 km in size and larger) that carry the potential danger of collision with the Earth are detected by ordinary astronomical observations. The bodies of intermediate dimensions began to be registered relatively recently. Observations of such bodies and the interpretation of observational data make it possible to determine the probability of their collision with the Earth, their properties, and the characteristic features of passage through the atmosphere, as well as the consequences of fall. The clarification of these questions will enable us to assess more accurately the degree of asteroid hazard.

 

One of the fundamental problems of meteor physics is the determination of the pre-atmospheric mass of bolides, since the intensity of the meteor phenomenon is determined by the kinetic energy of the body when entering the atmosphere of the planet. It is known that the velocity of the bodies belonging to the Solar  System at the entrance to the Earth’s atmosphere should be inside a relatively narrow range, between 11.2 and 72.8 km per second, so that the variance of the contribution of the velocitysquared factor to the kinetic energy does not exceed 50 times. At the same time, the mass of a meteor body can vary in a much wider range: from fractions of a gram (micrometeor) to tens of millions of tons or more (the Tunguska space body), that is, by 13–15 orders of magnitude.

The goal of Khrennikov et al.'s study was to evaluate the effect on the trajectory of the bolide of its passage through dense layers of the atmosphere, taking into account the acting forces, the initial velocity, and the mass and its variation during the flight, to determine the conditions for possible passage of a large bolide through the atmosphere with a minimum loss of mass without collision with the Earth’s surface. The obtained results are compared with observational data on the Tunguska space body with an estimated altitude of maximum energy release of about 10–15 km to receive evidence in favour of a new explanation of the Tunguska phenomenon, which attributes the absence of meteoritic material on the Earth’s surface near the epicentre to the through passage of the bolide across the atmosphere with a small loss of velocity.

Firstly, Khrennikov et al. imagine a model explaining the entry of a bolide into the Earth’s atmosphere with respect to a chosen X–Y coordinate system coinciding with the centre of the Earth and corotating with the rotation of the Earth. The altitude of the entry of the bolide into the atmosphere is measured from the starting value 160 km, at which the temperature of the bolide begins to increase. The angle of entry into the atmosphere relative to the local horizontal line at the altitude 160 km.is one of the most important parameters of the problem. 

Schematic diagram of the motion of a bolide in the Earth’s atmosphere and the angle of entry into the atmosphere (β) at a given point relative to the X–Y coordinate system. Rₑ is the radius of the Earth. Thickness of the atmosphere is exaggerated. The trajectory of the bolide and its length within the atmosphere are indicated by the line with the arrow. Khrennikov et al.(2020).

Khrennikov et al. describe the ballistics of the bolide by a system of equations, including the equation of motion under the action of applied forces: the force of the aerodynamic drag and the gravitational force.

The contribution of the lifting force to the ballistic motion of the bolide is also neglected as Khrennikov et al.assume that its shape is close to spherical. The Coriolis and centrifugal forces in the rotating reference frame are negligible for fast-moving bolides compared to the aerodynamical forces from stratospheric winds, which they also neglect here because bolides move much faster than the wind speed.

In accordance with existing ideas, Khrennikov et al. assume the main contribution to the force of aerodynamic drag is made by the difference in pressure between the frontal and rear parts of the bolide's surface (low-pressure cavity forms near the rear surface).

Mass-loss of bolides occurs due to heating to a temperature much higher than the melting point. In Khrennikov et al.'s model the main contributor to this heating is the radiant heat transfer between the the bolide and the boundary layer of the shock wave, whose temperature reaches several thousand degrees close to the surface of the bolide. One of the most difficult problems in calculating the radiant heat transfer is the determination of the radiant heat transfer coefficient. Its magnitude is affected by the velocity of motion in the atmosphere, flight altitude, air density, temperature of the boundary layer and the nature of the processes in the boundary layer (dissociation and ionization of air molecules), the degree of blackness of the radiating and absorbing surfaces, etc.

Khrennikov et al.'s model does not involve the process of bolide fragmentation, since the initial dimensions of the bolide are taken to be quite significant (from 50 to 200 m) as well as moderate velocities, when most of the bolide remains intact, despite extreme external influences. First of all, maximum resistance to fragmentation is characteristic of iron bolidess, which is associated with the high homogeneity of their internal structure. In contrast to the iron bolidess, the internal structure of stone and ice bolidess is heterogeneous with an abundance of numerous microcracks. The results of the study of the conditions for the fragmentation of iron bolidess will be presented in the future.

Khrennikov et al. denote the mass-loss by the term ‘ablation’, which includes two processes: The first process is the low-temperature blowing off a liquid film from the bolide's surface (at a temperature about 1000°C) with the formation of small droplets. These droplets are typical for a slow fall of small bolides or their fragments at the final stage of the flight in the atmosphere. The second process is the high-temperature sublimation of material occurring when the surface temperature exceeds several thousand degrees. In this case, a mass-loss occurs in the form of vapours of single atoms and their ions. Under the conditions in consideration, Khrennikov et al.'s model includes the sublimation as a dominant process responsible for the mass-loss at high velocities (over 12 km per second).

As a typical example of Khrennikov et al's calculations, in th case of the trajectory of a spherical iron bolide with a radius of 50 m entering into the atmosphere at 20 km per second when passing through it at the entry angle 11.2° and a minimum altitude of 11 km, the perturbation of the trajectory of the SB deviates it from the initial direction by an angle of 11.25° when neglecting the aerodynamic drag effect and 16.9° when the aerodynamic drag effect is taken into account. These results demonstrate the significant effect of aerodynamic drag on the bolide trajectory.

 

Changes in the trajectory of SB during a through passage via the atmosphere. The bolide parameters are radius 50 m, the velocity of entry into the atmosphere is 20 kmper second, and the minimum altitude is 11 km. Khrennikov et al. (2020).

At present, there are over 100 hypotheses about the nature of the Tunguska phenomenon, among which three to four versions  are predominant theories. They include the fall on to the Earth of a small asteroid measuring several dozen metres, consisting of typical asteroid materials, either metal or stone, as well as ice, which is characteristic of cometary nuclei. The most probable material of the Tunguska bolide mentioned in literature is ice. According to the available observational data, there are several variants of the direction and the trajectory length of the Tunguska bolide, from 450 to 600 km, in particular, with a propagation direction from ‘south–north’ to ‘east–west’. The value of the angle of entry into the atmosphere mentioned in literature is 30°–40°. The radius of the Tunguska bolide was estimated based on the amplitude of the shock wave recorded by the seismic stations and amounted to about 25 m. The minimum trajectory altitude of the Tunguska bolide approximately corresponded to the point of maximum energy release.

The results of comparative calculations of the velocity variations of iron, stone, and ice bolides with radii 100 and 50 m along the trajectory of through passage across the atmosphere for an initial velocity of 20 km per second, suggests that stone bolides lose their velocity faster than iron bolides, and ice bolides do not survive passage through the atmosphere.

Khrennikov et al. calculated the trajectories of bolides with radii of 50 m and iron and stone compositions. Both enter the atmosphere at 160 km, reach a minium altitude of 11 km, then exit the atmosphere at 160 km agian. However, there is a considerable lengthening of trajectory of the stone bolide compared to the iron body. The iron bolide passes through the atmosphere with a minimum loss of velocity and minimum deflection due to a high initialmass, whereas the stone bolide subsequently re-enters the atmosphere due to a significant decrease in velocity. Although quite improbable, such an bolide could manifest itself as a pair of explosive phenomena in the atmosphere separated by thousands of kilometres in distance and tens of minutes in time.

Khrennikov et al. calculated the trajectories of an ice bolide with a radius of 100 m at different entry angles and changes inmass. They found that such a bolide suffered a dramatic loss of mass at angles over 11°. At angle 10°, the initial mass is preserved due to the high altitude, with the bolide remaining over 50 km above the Earth's surface. 

Next Khrennikov et al. calculated the reduction of the masses of ice bolides with radii of 100, 50, and 25 m on the trajectory of collision with the surface of the Earth. The residual fractions of the mass at an initial velocity of 15 km per second were 49 per cent, 21.3 per cent, and 4.8 per cent, respectively, for radii of 100, 50, and 25 m. The length of the trajectory until the moment of the collision with the surface of the Earth is about 325 km for the initial velocity of 15 km per second. At an entry velocity of 25 km per second, for radii of 100 and 50 m, ice bolides fall with a preservation of 6 per cent and 0.000 04 per cent of the initial mass respectively. For radii of 25 m and entry velocity of 25 km per second, an ice bolide loses all its mass completely within a trajectory length of about 329 km.

Of course, the fall of a bolide with preservation of a significant part of the initial mass results in the formation of a crater with a diameter larger than 1 km. However, there are no craters near the epicentre of the Tunguska Event or in the surrounding area. The actual length of the trajectory based on the results of visual observations was estimated to be about 450–700 km, which is over 1.5 times longer than the calculated value for the ice bolide. Therefore, the hypothesis of the ice origin of the Tunguska bolide, which enters the atmosphere at an angle of 30°–40°, is hardly justified accorind to Khrennikov et al.'s model.

Moreover, the decrease in the mass of the ice bolide with an initial radius of 100 m along the trajectory at small angles of entry into the atmosphere, while preserving a significant fraction of mass is possible only at a minimum altitude above 40 km, which contradicts with the estimated minimum altitude of about 10–15 km in the Tunguska event.

Khrennikov et al.'s calculations showed that the trajectory length of the ice bolide when it passes through the atmosphere at a minimum altitude of 15.5 km and small entry angles (less than 15°) until the moment of its complete loss of mass even at a radius of 100 m is two times shorter compared to the case of the iron bolide. Thus, the through passage of the ice bolide at small entry angles with a minimum trajectory altitude 10–15 km is impossible.

For the ice bolide with a radius of 25 m, the length of the trajectory to the moment of the total loss of mass is reduced by four to five times. In addition, it was shown that a considerable part of the initial mass is preserved by iron and stone bolides with radii of 100, 50, and 25 m at an entry angle of 30°. But their fall would be accompanied by the formation of craters with a diameter larger than 1 km and a depth over 200 m.

Khrennikov et al. did not deal with the problem of the formation of a shock wave, although when comparing the Tunguska phenomenon with the Chelyabinsk meteorite with a size of about 10 m and an altitude of maximum energy release of about 30 km, they have no reason to doubt that the body that is 10–20 times larger with an altitude of maximum energy release of 10–15 km at a velocity of 20 km per second will create a shock wave with a huge amplitude and destructive force, capable of causing tree-fall over an area exceeding 1600 km². Experimental modelling of the knock-down effect of a shock wave from the source with cylindrical geometry was performed in a 1966 study. The cylindrical source of the shock wave was modelled by a long detonating cord inclined at a certain angle to a plane planted with small sticks, which imitated trees in the Siberian forest. It was shown that the shape of the area of fallen sticks was similar to the shape of real treefall territory. However, that study did not model the dependence of the strength of the cylindrical shock wave on the height of its source above the ground. Instead, they added a point explosive at the lower end of their cord to model a presumed spherical component of the shock wave. Because rates of the mass and energy losses of the bolide that caused the Tunguska event depend strongly on its altitude above the ground a sharp increase in energy release close to the minimum altitude reached by the through passing bolide can be interpreted as an explosion creating a spherical component of the shock wave. Clearly, making a detailed prediction for the patterns of tree-fall in the framework of our hypothesis of a through-passed bolide as a cause for the Tunguska event will be an important subject of future research.

In solving the main problems in this work, Khrennikov et al. confined themselves to the need to make an upper estimate for calculating the residual mass of space body using the parameters maximising the massloss. They did not consider the problem of the mass-loss of the space body due to its fragmentation. This will be the subject of future research and the results will be published elsewhere.

Based on the obtained results, Khrennikov et al. make the following statements: (i) The conditions for the possible through passage of a large space body composed of various materials across the Earth’s atmosphere with a minimal loss of mass and without collision with the surface of the planet are established. It was shown that this corresponds to the entry angles of space body into the atmosphere of at least 11.5°. (ii) It was shown that the Tunguska space body could hardly consist of ice, since the length of the trajectory of such a body in the atmosphere before the complete loss of its mass would be less than the length of its trajectory estimated on the basis of observational data.  (iii) The value of the angle of entry into the atmosphere of 30°–40° mentioned in the literature for the Tunguska space body looks unrealistic, since it corresponds to the trajectory of a fall of a body with a large residual mass and trajectory length, which is 1.5–2 times shorter than the estimated trajectory length based on the observational data. Such a fall would be accompanied by the formation of a large crater, absent near the epicentre and around. (iv) The most realistic version explaining the Tunguska phenomenon is the through passage of the iron asteroid body as the most resistible to fragmentation across the Earth’s atmosphere at a minimum altitude of 10–15 km with the length of the trajectory in the atmosphere of about 3000 km and a subsequent exit of this asteroid body into the outer space to the near-solar orbit. This version is supported by the fact that there are no remnants of this body and craters on the surface of the Earth. Within this version,  Khrennikov et al. can explain optical effects associated with a strong dustiness of high layers of the atmosphere over Europe, which caused a bright glow of the night sky.

If Khrennikov et al. admit the version of the complete loss of mass of the bolide after the passage of the epicentre or close to it, then the evidence of its reality would be the presence of droplets of meteoric iron of millimetre sizes on the Earth’s surface along the trajectory of the bolide. It follows that the smaller the bolide size and its mass are, the faster it loses a velocity (the amplitude of the shock wave near the epicentre also becomes smaller). Finally, when the velocity of a diminishing bolide reduces to such an extent that its surface temperature approaches 1000°C, the sublimation ceases and the dominant mechanism of mass-loss consists of blowing off a liquid film from the surface of the body. In this case, the bolide becomes the source of a huge amount of droplets, which will be sprayed by the bolide. However, such microformations have not been found despite intensive searches around the epicentre and far beyond. The absence of iron droplets around the epicentre is explained by the high velocity of the bolide during through passage across the Earth’ s atmosphere, always over 11.2 km per second when the surface temperature exceeds several thousands of degree Celcius. The dominant mechanism of mass-loss at these temperatures is the sublimation of material in the form of single atoms, which can be found on the Earth’s surface as iron oxides, which do not differ from the same widespread iron oxides of terrestrial origin.

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Dendrochernes mahnerti: A new species of Pseudoscorpion from Xinjiang Province, China.

The Chernetidae is the most speciose family in the Pseudoscorpiones and is composed of over 650 species in more than 110 genera, but only 10 genera and 16 species have been reported from China. The chernetid genus Dendrochernes was erected by Max Beier in 1932, and at present comprises only four known species: the type species Dendrochernes cyrneus is widespread in central Asia (Pakistan, Kazakhstan and Kyrgyzstan), north Africa and Europe; while the remaining three species occur in north America: Dendrochernes crassus, Dendrochernes morosus, and Dendrochernes instabilis.

In a paper published in the journal Arthropoda Selecta on 19 June 2020, Zhizhong Gao of the Department of Biology and Wutai Mountain Institute of Resource and Environment at Xinzhou Teachers University, and Feng Zhang of the Key Laboratory of Zoological Systematics and Application at Hebei University, describe a new species of Dendrochernes from Xinjiang Province, China.

Kanas Lake, located in a valley in the Altai Mountains in the Burqin County of Altay Prefecture, northwestern China, is China’s deepest freshwater alpine lake, with a high biodiversity. It borders with the country of Kazakhstan, Mongolia and Russia.

While examining Pseudoscorpion specimens collected from Xinjiang, two chernetid specimens presenting the generic characters of Dendrochernes were examined: eye spots lacking or indistinct; tergites divided except the last one and finely to moderately granulate; setae of body and palps broadened and thickened, denticulate and short, never strongly clavate; rallum with 4 (but occasionally 3) blades; palps stout, finely to moderately granulate; accessory teeth of chelal fingers numerous; tactile seta sub-terminal of movable finger nearer to sub-basal than to terminal; fixed finger with tactile seta interior sub-terminal at the level of or very little distal to the level of exterior sub-terminal; tarsus IV with a tactile seta located distal to the midpoint of the tarsus, being 0.6 to 0.7 of the length of the tarsus from the proximal margin of the segment; the spermatheca of the female with two long, slender tubules, of uniform diameter throughout, greatly coiled, and without a terminal enlargement or bulb.

The new species is named Dendrochernes mahnerti, in honour of Volker Mahnert, a famous zoologist and arachnologist, who has made significant contribution and leaves behind an outstanding scientific legacy on Pseudoscorpions. It is described from two female specimens, collected by Feng Zheng in August 2006 from under tree bark, at an altitude of 1456 m above sealevel, in the Kanas National Nature Reserve in Burqin  County in the Xinjiang Uygur Autonomous Region of China.

 

Dendrochernes mahnerti, (a) female holotype habitus, dorsal view; (b) female paratype habitus, dorsal view. Gao & Zhang (2020).

The colour of Dendrochernes mahnerti is mostly reddish brown, carapace, legs brown, tergites and palps darker, remaining parts (sternites and pleural membranes) light yellowish brown. Most setae slightly apically denticulate.

The surface of the carapace is evenly granular. Slightly longer than broad (1.07–1.17 times), eyespots indistinct, with two regularly granular transverse furrows, both of them very distinct, the subbasal one slightly nearer to the posterior margin than to median furrow, a longitudinal shallow groove in metazone. With about 110 setae, including 6 on anterior margin and 12–13 on posterior margin. All setae short and apically dentate.

All tergites of the abdomen are widely divided except the last one. Lateral keels absent; weakly scale-shaped sculpture. Half-tergites with about 8–11 setae, tergite VI with 13–16 setae (include 2 long tactile setae), anus with 2 simple and acuminate setae. Manducatory process with 5 setae. All sternites distinctly divided except VI, weakly scaly sculptured, setae simple and acuminate, chaetotaxy (IV–XI): 6(5)–6: 13–13(16): 15(16)–15: 14(17)–14(15): 11(15)–12(15): 11(15)–11(16): 9(11)–10(11): 12 (include 4 long tactile setae): 2 (simple and acuminate setae). Coxae of pedipalps scale-shaped sculpture, with about 21, coxae I with about 15, II 20, III about 25 setae, IV numerous setae. Anterior genital operculum with about 31–32 simple and acuminate setae, 21–22 setae in a row along the posterior margin of the posterior operculum.

Spermatheca with 2 long tubules, both of them without distinct terminal enlargements or bulbs.

The chelicera have weakly scale-shaped sculpture. Five setae in basal part, all of them simple and acuminate; with 2 lyrifissures on the dorsal face of palm; fixed fingers with a few different sized teeth in the end. Movable finger with a seta in midway of terminal of finger; serrula exterior with 23–24 lamellae. Rallum usually with 4 blades, but occasionally with 3, anterior blade slightly denticulate. Galea with 6 short branches.

Palp slender, most segments normally granulate; except for chelal fingers, which are finely gaping; setae acuminate and weakly apically dentate; without tactile setae on femur, patella or hand; trochanter with distinct rounded dorsal hump; proportions (based on two specimens): trochanter 1.41–1.70 times as long as broad; femur 2.63–2.71 times as long as broad; patella 2.18–2.23 times as long as broad; chela with pedicel 2.63–2.75 times as long as broad, chela without pedicel 2.45–2.54 times as long as broad, hand with pedicel 1.56–1.59 times, without pedicel 1.37–1.41 times, as long as broad. Movable finger 0.77–0.78 times as long as hand with pedicel, and 0.88 times without pedicel. fixed finger with 36–37 teeth, 11–12 acuminate accessory teeth on lateral side, 7–8 accessory teeth on interior side; movable finger with 40–44 teeth, 10–11 acuminate accessory teeth on lateral side, 6–7 accessory teeth on interior side; nodus ramosus closer to terminal than to sub-terminal. 

Venom apparatus only present in moveable chelal fingers, venom duct slender, extend over trichobothrium terminal in movable fingers.

Leg I has a typical facies, with numerous terminal slightly denticulate and acuminate setae, tactile setae absent, weakly scale-like sculpture, claws simple; proportions: trochanter 1.00–1.31 times; femur 1.45–1.47 times; patella 2.30–2.35 times; tibia 3.43–3.54 times; tarsus 4.20–4.56 times as long as deep. Subterminal tarsal seta simple, acuminate and curved, arolium shorter than claws. 

Leg IV has a surface weakly scale-like sculptured; tibia and tarsus with numerous terminal slightly denticulate and acuminate setae, trochanter 1.68–1.71 times; femur+patella 3.23–3.48 times; tibia 4.44–4.53 times; tarsus 3.75–3.83 times as long as deep. An acute tactile seta in terminal third of tarsus and almost the half long as tarsus; arolia undivided and shorter than the simple and large claws, subterminal seta simple, acuminate and curved.

Both chelicerae of the holotype and paratype were examined in different orientations to obtain an 'all-round-view' of each rallum. Although most had four blades, which is typical of the genus, the left rallum of the holotype consisted of only three blades.

The right tubule of the spermatheca in the holotype possesses a short branch, which is unusual, we subsequently dissected the spermatheca of the paratype and there is no any modification on both tubules, so Gao and Zhang prefer to think that the presence of a short branch on the right spermatheca of the holotype is an anomaly.

Dendrochernes cyrneus is widespread across Europe and Asia, with vast literatures citations. It is difficult to identify a specimen to species level only based on immature individuals which little diagnostic characteristic can be used, for instance, extraordinarily dark coloring of the carapace, the palps and the tergites is absent in juveniles. The record from Kyrgyzstan are based on only a deutonymph; although it is possible that Dendrochernes cyrneus distributed in Kyrgyzstan, the record is still unreliable.

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Lycocerus wenchuani: A new species of Soldier Beetle from Taiwan.

Soldier Beetles, Cantharidae, are an extremely diverse and widespread group of elongate, soft-bodied Beetles related to Click Beetles and Fireflies. They get their name from the red colouration of one of the earliest species descried, which resembled the colour of the red jackets worn by British soldiers in the eighteenth century, rather than any particularly aggresive behaviour. 

In a paper published in the journal Acta Entomologica Musie Nationalis Pragae on 15 July 2016, Yun Hsiao of the Department of Entomology at the National Taiwan University and Yûichi Okushima of the Kurashiki Museum of Natural History describe a new species of Solier Beetle from southern and southeastern Taiwan.

The new species is placed in the genus Lycoceras, an extremely specious Asian genus, with thirty six previously described species from Taiwan alone, and given the specific name wenchuani, in honour of Wen-Chuan Liao, who collected the first known specimen of the species and who is a citizen scientist who assists many Taiwanese taxonomists with the collection of material. The species is largely black in colour with yellow and brown markings, and reaches 4.5-5.0 mm in length. Females are slightly wider than the males, with slightly smaller eyes. The species was originally noted by the Jinshuiying Historic Trail in Pingtung County, but is thought to be present across south and southeastern Taiwan, at altitudes of 1000-1600 m above sealevel. Adults of the species appear from late spring into early summer.

Lycocerus wenchuani. (F) Male, and (G) female. Hsiao & Okushima (2016).

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Japanese Eel classified as Endangered.

The International Union for the Conservation of Nature published its annual update of its Red List of Threatened Species on Thursday 12 June 2014, marking the 50th year of the list's existence, and revising the status of a number of Plant and Animal species from around the world. The Japanese Eel, Anguilla japonica, has been included on the list for the first time, being believed to have lost over half its spawning population in the last 30 years, primarily due to overfishing. 

A Japanese Eel, Anguilla japoonica, in Hong Kong. HT Cheng/iNaturalist.

While named for Japan, the species is quite widespread, being found from Korea and Japan in the north, along the coasts of China, Taiwan and Hong Kong to the Philippines in the south, as well as sometimes being found in Thailand, Vietnam and Cambodia. However recent studies have shown that all the Eels across this range form a single population with a common breeding ground, to the west of the Mariana Islands. The Eel is also widely bred in captivity, with waterways stocked from captive-bred Eels across much of its range. However it is far from clear if these captive-bred Eels are capable of returning to the wild spawning grounds, and thereby contributing to the future of the species. 

The known range of the Japanese Eel, Anguilla japonica. ICUN Species Survival Commission.

Like most Eels the Japanese Eel has a complex life cycle, with adults migrating to breed at an oceanic breeding site remote from the land, and an ocean-going larval stage that migrates back to estuarine waters before metamorphosing into a juvenile that takes several years to mature to a full adult. Unusually the Japanese Eel seems to have two separate post-metamorphic lifestyles, with some juveniles migrating into rivers and other fresh water ecosystems to mature, while others remain in shallow marine waters around the coast. However all these Eels appear to be a single breeding population. 

The single breeding site for the species, combined with heavy levels of human consumption of all life-stages across its range, and uncertainty as to the extent to which each adult population contributes to the breeding population, together with the risk of the breeding cycle being disrupted by climate-change driven changes in ocean current, lead to a considerable degree of concern about the future of this species.

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 A living fossil eel discovered in Palau.

Eels first appear in the fossil record about 100 million years ago, in the Mid Cretaceous. These Cretaceous forms are primitive compared to modern forms, with incomplete fusion of the dorsal, caudal and anal fins, scales on their bodies and many of the bones lost or fused still present. However they are still clearly eels, with elongate bodies and the loss and fusion of some bones associated with the group, in...

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The origin and diversification of modern Lions.

Lions (Panthera leo) are large, charismatic predators currently found in Africa and India, with a fossil record that includes areas of northern Eurasia and North America. Lions outside their current range persisted in North Africa (Barbary Lions) and the Middle East (Persian Lions) into historic times, but are now extinct. Modern Lions are divided into two subspecies, the Indian Lion (Panthera leo persica), which is considered to be 'Endangered' under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, with only about 400 individuals thought to be surviving in the wild, and the African Lion (Panthera leo leo) considered to be 'Vulnerable', having suffered a roughly 30% decline in numbers in the last two decades.

Lion Frieze from the Palace of Darius I, dating from circa 510 B.C., currently in the Louvre Museum. Lions are no longer found in the Middle East. John Malyon/Artcyclopedia.

In a paper published in the journal BMC Evolutionary Biology on 2 April 2014, a team of scientist led by Ross Barnett of the Department of Archaeology at Durham University describe the results of a study into relationships between modern and historic Lion populations, based upon the analysis of mitochondrial DNA, and the implications of the results of this analysis for the conservation of Lions.

Traditionally modern Lions have been split into two subspecies, with Indian and Persian Lions being described as Panthera leo persica and all African Lions, including the Barbary Lions of North Africa, being described as Panthera leo leo, while other subspecific names were assigned to various fossil Lions.

Barnett et al. could find no evidence to support this classification system, with modern Lions falling into five distinct groupings (fossil Lions were not examined in the study). Persian and Indian Lions did form a single group, but this group also included the Barbary Lions of North Africa, while the Lions of sub-Saharan Africa could be divided into four groups; West African, Central African, East African and Southern African. Furthermore these five groups could be grouped into two larger groups, one comprising the Barbary and Asian Lions plus West and Central African Lions, and the other comprising Southeastern and Southern African Lions.

Furthermore the study suggested that all the modern Lion groups shared a common ancestor in the Late Pleistocene, around 124 200 years ago, and that the Lions of Asia are the result of a much later migration, in the Late Pleistocene to early Holocene, 24 000 to 10 000 years ago. The fossil Lions of Eurasia and North America are therefore likely to have been the result of one or more earlier migrations, which subsequently became extinct.

An Indian Lion at Arignar Anna Zoological Park. Vincent Paul/Wikimedia Commons.

Barnett et al. suggest that the divergence of the different groups of Lions can be dated using a molecular clock method. The oldest split occurred between Southern and Eastern African Lions and all other lions around the calculated time of the most recent common ancestor, so about 124 200 years ago. Southern and East African Lions then split around 81 900 years ago. The Central African Lions split from the West and North African/Asian Lions around 61 500 years ago, and the West African Lions split from the North African and Asian Lions around 51 000 years ago.

Phylogenetic tree of modern Lions, based upon mDNA analysis. Estimates of divergence times: (a) 124,200 years; (b) 61,500 years; (c) 51,000 years; (d) 81,900 years; (e) 57,800 years; (f) 21,100 years. Branch colours correspond to reconstructed ancestral geographic states (Purple, South Africa; Yellow, East Africa; Orange, West Africa; Red, Central Africa; Teal, North Africa; Blue, South Asia; Green, Near-East). Barnett et al. (2014).

Barnett et al. suggest that the separation of the different Lion groups represents shifting climatic patterns during the Pleistocene, with lions expanding to populate most of Africa during the dryer period prior to about 130 000 years ago,  when the continent was covered by savanna and scrub woodland, but subsequently becoming divided into two populations by the expansion of rainforests in the subsequent more humid period. Around 74 000 years ago the climate began to dry again, enabling some Lions to colonize Central Africa from the West, then eventually leading to the expansion of the Sahara Desert, which separated the Lions of North and West Africa. Finally some North African Lions expanded into southwest Asia in the warming climate at the end of the Pleistocene.

Reconstructed distribution of the modern lion at different times. Estimates of spatial diffusion pathways at Marine Isotope Stage (MIS) time points: (A) MIS5 (B) MIS4-MIS3 (C) MIS2-MIS1 (D) Estimated natural distribution prior to anthropogenic disturbance. Black arrows show

estimated spatial diffusions, with thicknesses proportional to Bayes factors. Movement from East Africa to South Africa (4.83), from South Africa to East Africa (4.66), from West Africa to Central Africa (3.00), from North Africa to South Asia (4.37), from South Asia to North Africa (4.50), from North Africa to Middle East (21.03). Tropical rainforest is shown in light grey (present distribution), maximal extent during humid periods (black dashed line), and minimal extent during arid periods (white dashed line). The Great Rift Valley is shown in dark grey. African rivers are shown in blue. Co, Congo; Ng, Niger; Ni, Nile; Se, Senegal. Barnett et al. (2014).

This has strong implications for the conservation of Lions. All African Lions have previously been regarded as members of a single sub-species, Panthera leo leo, which while stressed across parts of its range, was thriving in others, giving the species the potential to recover should the opportunity arise or be created. However if African Lions comprise four separate sub-species, then two of these subspecies should be regarded as being at a much higher level of risk; there are thought to be about 800 West African Lions and about 900 Central African Lions surviving in the wild, making these groups almost as vulnerable as the Lions of India. Furthermore almost all Lions in captivity in zoos are descended from East or Southern African Lions, severely limiting the potential for restoring West or Central African Lion populations with captive breeding programs.

There has also been considerable talk of re-introducing Barbary Lions to North Africa in recent years. This idea has been based upon the idea that these Lions belonged to the same subspecies as the Lions of sub-Saharan Africa, making fairly large, healthy populations available from which to recruit Lions for the re-colonization of North Africa. However if the Barbary Lions were in fact the same sub-species as the endangered Lions of India, and re-introduction methods wish to repopulate North Africa with the same subspecies that formerly colonized the region, then this project becomes correspondingly more difficult.

See also...

 A new species of Fox from the Pleisticene of Gauteng Province, South Africa.

 The diet of the Langebaanweg Hyaenids.

 Fossil Pandas from the Middle Miocene of Spain.

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A new species of Bumble Bee Scarab Beetle from the Early Cretaceous of Inner Mongolia.

Bumble Bee Scarab Beetles (Glaphyridae) are small, brightly coloured Scarab Beetles; they are active animals, and frequently resemble Bumble Bees when in flight. There are eight extant genera in the family, two of which have fossil records. Another two genera are known from the fossil record only. The fossil record of the family dates back to the Early Cretaceous.

In a paper published in the journal ZooKeys on 14 November 2012, Zhuo Yan of the Key Laboratory of Insect Evolution and Environmental Changes at the College of Life Sciences at Capital Normal University in Beijing, Georgiy Nikolajev of the Department of Biology and Biotechnology at the Al-Farabi Kazakh National University and Dong Ren, also of the Key Laboratory of Insect Evolution and Environmental Changes, describe a new species of Bumble Bee Scarab Beetle from the Early Cretaceous Yixian Formation at Liutiaogou Village in Ningcheng County, Inner Mongolia.

The new species is considered to be distinctive enough to be placed in a new genus, named Cretohypna, meaning Anthypna, from the Cretaceous; Anthypna being  a modern genus of Glaphyrid Beetle. It is given the specific name Cretohypna cristata, where 'cristata' means crested, a reference to a crest-like structure on the head. The species is described from a single male specimen. Cretohypna cristata is a 16.1 mm Beetle with an elongate oval body. 

Cretohypna cristata; (a) protibia, (b) mesotibia, (c) body in dorsal view, (d) metatibia and metatarsus. Yan, Nikolajev & Ren (2012).

Cretohypna cristata, line drawings of holotype in (a) dorsal view, and (b) ventral view. Yan, Nikolajev & Ren (2012).

The Yixian Formation is probably 129.7-122.1 million years old, making it from the Barremian to early Aptian Age. The deposits are mainly lacustrine (from a lake) with occasional horizons of volcanic ash. The climate at the time of deposition interpreted as cool temperate, with mean air temperatures of 10 ± 4 °C. The formation is noted for its numerous fossil insects.

The approximate location of the site where Cretohypna cristata was found. Google Maps.

See also A new species of Corythoderine Scarab Beetle from Cambodia, Two new species of Ground Beetle from the Pyrenees, Six new species of Jewel Beetle from Southeast Asia, A Rove Beetle from the Late Triassic of Virginia and A new species of Blister Beetle from southeast Iran.

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A cryptic Sea Snake from Australia.

The Beaked Sea Snake Enhydrina schistosa is known from the Arabian Gulf to Southeast Asia and south to Australia and Papua New Guinea. It is distinctive, with an elongated central scale on its lower jaw, overlapping the upper jaw to form a sort of beak, used to tackle spiney Fish. The Snake has a bad reputation; its habits lead to it frequently being caught in fishing nets, where it is hard to detect. To make matters worse it is notoriously bad tempered, and has an extremely venomous bite. About 50% of all Sea Snake bites are the work of Enhydrina schistosa, and around 90% of fatalities.

The Beaked Sea Snake, Enhydrina schistosa. Avinash Shanbhag/Indian Snakes.

In a paper published in the journal Molecular Phylogenetics and Evolution on 5 October 2012, a team of scientists led by Kanishka Ukuwela of the School of Earth and Environmental Sciences at the University of Adelaide publish a study of the population genetics of Enhydrina schistosa, which suggests that the Snake is in fact two sepperate, convergently evolved species, that arose within the morphologically disticnt genus Hydrophis, the two Snakes having apparently setttled on the same form due to similar ecologies (convergent evolution).

This is an important discovery, and not just from a taxonomic point of view; there is no reason to suppose that two Snakes that have evolved similar morphologies will have evolved similar venoms, and therefore an antivenom developed to counter the venom of one Snake is unlikely to have any effect on the venom of the other. Fortunately the Snakes do not seem to have overlapping ranges, with one species found in Australian waters and the other around the coast of South Asia.

The taxonomic position of the snakes is now complicated; Ukuwela et al. report the early description of a second species in the genus Enhydrina, Enhydrina zweifeli, described from a single specimen from Papua New Guinea in 1985, but not generally recognised as a valid species by herpetologists. The Australian population of Enhydrina schistosa is reported to have fewer bands on the body than the Asian population, and lower but broadly overlapping ventral scale count; a description matching that of Enhydrina zweifeli, and Ukuwela et al. suggest this name should be used to describe the Australian population. 

However this would make the genus Enhydrina polyphyletic (having more than one origin) and the genus Hydrophis paraphyletic (not including all the species descended from the last common ancestor of the group) whereas modern taxonomy usually requires that taxomic groups be monophyletic (all descended from a common ancestor, and including all the species descended from that ancestor), so it is likely that this taxonomy will change.

The multiple origins of Enhydrina schistosa within the genus Hydrophis. Ukuwela et al. (2012).

See also New species of Snail-eating Snake from western Panama, New species of Treesnakes from the Comoras, New species of Asian Coral Snake from western India, Velvet Geckos and Broad-headed Snakes; understanding the population structure of a favored prey item in order to help protect an endangered predator, and Reptiles on Sciency Thoughts YouTube.

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A new species of Pseudoscorpion from Hainan Island, south China.

Pseudoscorpions (or False Scorpions) are small Arachnids with flattened oval or pear-shaped bodies; they have pincers resembling those of true Scorpions, but lack stinging tails. The largest species reach 12 mm, but most are considerably smaller. They have a fossil record dating back to the Devonian, and may be considerably older since the oldest fossils closely resemble modern forms.

In a paper published in the Journal of Threatened Taxa on 26 September 2012, Jun-fang Hu and Feng Zhang of the College of Life Sciences at Hebei University, describe a new species of Pseudoscorpion from Hainan Islans, off the south coast of mainland China.

The new species is placed in the genus Atemnus, and given the specific name limuensis, after Mount Limu, where it was discovered living under the bark of an Ormosia tree (a type of Legume). Atemnus limuensis is a small, reddish brown Pseudoscorpion, with females larger than the males; 5.4-6.25 mm, compared to 4.38-4.88 mm. 

Atemnus limuensis, male specimen. Hu & Zhang (2012).

See also Two new species of Pseudoscorpion from China and An Eocene False Scorpion from Baltic amber. 

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A new species of tree-dwelling Fighting Fish from Thailand.

Fighting Fish (Bettas) are colourful members of the Gourami Family (Osphronemidae) popular in the aquarium trade and noted for their aggressive nesting behavior. In the wild they live in rice paddies and similar environments, where the males build bubble-nests from sticky oral secretions containing air bubbles, typically anchored to some sort of plant. The females lay their eggs in these nests, which the males then defend these nests against other males and any other perceived threats (the Thai name for the  Fish, Plaklad, translates as 'Biting Fish').

In a paper published in the journal Zootaxa on 19 October 2012, Chanon Kowasupat of the Institute for Innovative Learning at Mahidol University, Bhinyo Panijpan and Pintep Ruenwongsa of the Faculty of Science at Mahidol University and Namkang Sriwattannarothai also of the Institute for Innovative Learning at Mahidol University describe a new species of Fighting Fish found nesting in Nipa Palms (Nypa fruticans) in Samut Sakhon Province, Thailand.

Nipa Palms are a form of Mangrove; trees which can tolerate immersion in salt water, and which colonize tidal flats and salt marshes, forming unique habitats. The Palms trap pools of water at the bases of their leaf stems, similar to the pools of Bromeliads, and it is in these pools that the new species of Fighting Fish nests. The population has been known of for some time by fish enthusiasts, and there has been some prior speculation as to whether they were a separate species, or a population of the more widespread Splendid Fighting Fish, Betta splendens.

(a) A Nipa Palm stand in Samut Sakhon Province, Thailand. (b) Water pockets at the base of the leaf stems of a Palm, with Fish found within one of the pockets inset. (c) The Fish inside the pocket, with a bubble-nest to the right. Kowasupat et al. (2012).

Kowasupat et al. have now confirmed this Fish is a separate species, based upon both morphology and DNA analysis. They name it Betta mahachaiensis, after Maha Chai, where the Fish were first noted and where the suspicion they might be a separate species began. It was found at a number of sites in Samut Sakhon Province, west of Bankok. These sites are not pristine natural environments, they are disturbed by human activity (Nipa Palm is used as a roofing and basket-making material as well as an animal feed, and Arrack, a form of palm-wine, is made from its sap), and all are threatened by expansion of human settlements into the salt-marshes where they occur, suggesting that Betta mahachaiensis, is under threat from human activity. The area has also recently become prone to flooding with fresh-water, something which both the Palms and the Fish can tolerate, but which brings larger predators into the marshes.

(a) Map of Thailand showing the area where Betta mahachaiensis was found (rectangle). (b) Expanded map of the inset area, showing sites where Betta mahachaiensis and the related Betta splendens were found. Kowasupat et al. (2012).

Betta mahachaiensis is a 120-140 mm Fighting Fish, black or brown with iridescent green or bluish-green scales. The males are considerably more conspicuous than the females. 

Betta mahachaiensis; (top) male & (bottom) female. Kowasupat et al. (2012).

See also A Flying Fish from the Middle Triassic of Guizhou Province, China, To cull or not to cull? The Goliath Grouper in Floridan waters, A new species of Pufferfish form French Polynesia, A new species of Cichlid Fish from Lake Tanganyika and Boney Fish on Sciency Thoughts YouTube.

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How Bar-headed Geese cross the Himalayas.

Bar-headed Geese, Anser indicus, are well known for their annual migration between breeding grounds in Tibet, Mongolia and northern China, and wintering grounds in southern India, a migration route that involves crossing the highest part of the Himalayas. There have been frequent reports of climbers witnessing the Geese at extremely high altitudes, and they are regularly cited in popular literature as achieving sustained flights at altitudes exceeding 8000 m. However empirical data on such flights has been lacking, and migration routes in excess of 8000 m seem highly unlikely to biologists, as the air at this height is rarified (thin), providing little lift to the Geese (which are quite large Birds), and therefore requiring more energy, and at the same time depleted in oxygen, making less energy available. In favor of the high altitude migration route, it has been agued that it would represent a much shorter total journey and that it would reduce the risk of Geese flying into mountains.

Bar-headed Geese (Anser indicus) in flight. Rajiv Lather/Birding in India.

In a paper published in the Proceedings of the Royal Society Series B: Biological Sciences on 31 October 2012, a team of Scientists led by Lucy Hawkes of the School of Biological Sciences at the University of Bangor and the Environment and Sustainability Institute at the University of Exeter, present the results of a study in which Bar-headed Geese were radio-tagged in order to trace their travel routes through or over the Himalayas.

Hawkes et al. found that the Geese spent 95% of their time bellow 5784 m (still impressively high), choosing to take a longer route through the Himalayas in order to utilize lower-altitude valleys and passes. Only 10 of the 91 Geese tagged were ever recorded above this altitude, and only one exceeded 6500 m, reaching 6540 m on an overnight flight, when the air was particularly cool (and therefore dense). While they cannot rule out the possibility that Geese do sometimes reach higher altitudes, Hawkes et al. strongly suspect that tales of Geese flying at 8000 m are apocryphal, owing more to climbers' folk-law than to accurate observation.

(a) Map showing the migration routes of the tagged birds. (b) The land elevation of a cross-section through the migration route (exaggerated). Hawkes et al. (2012).

See also A fossil Bird from the Eocene of Guangdong Province China, The impact of the introduced Common Myna on the Birds of Canberra, How the Deepwater Horizon oil spill effected wildlife on the Gulf of Mexico, Ritual use of raptor claws by Neanderthals, 90 000 - 40 000 years ago and Birds on Sciency Thoughts YouTube.

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