Looking for the eastern margin of the Palaeo-Tethys Ocean.

The Palaeo-Tethys Ocean ran separated the continent of Gondwana from the landmasses that would become Europe and Asia during the Palaeozoic Era, opening during the Middle Cambrian and eventually closing with the formation of the Supercontinent of Pangea during the Permian/Triassic. The western part of this ocean is reasonably well understood, but the eastern extent is less well known, as much of the geology of the region has been distorted and overwritten by the Himalayan Orogeny, as the Indian Plate has impacted Eurasia from the south. The ocean probably passed along the southern margin of the South China Block (also known as the Yangtze Plate) (i.e. the southeastern coast of China), producing an area of rifting similar to that seen beneath the Red Sea today, but there is little evidence to support this.

In a paper published in the journal Acta Geologica Sinica on 27 February 2018, Hu Lisha, of the Collage of Marine Geosciences at the Ocean University of China, and the Laboratory for Marine Geology at the Qingdao National Laboratory for Marine Science and Technology, Du Yuansheng of the State Key Laboratory of Biogeology and Environmental Geology at the China University of Geosciences, and Xu Yajun, Wang Zhiwan, and Wang Chenghao, also of the Collage of Marine Geosciences  at the Ocean University of China, describe the discovery of a volcanic tuff (ash) layer from Banchen in the Qinzhou area of the Guangxi Zhuang Autonomous Region of southeastern China, could provide evidence for subduction along the southern margin of the South China Block during the Palaeozoic.

Hu et al. report the discovery of a green tuff layer between layers of Devonian siliceous rocks, from which zircons were extracted for uranium/lead dating. Zircon is a mineral formed by the crystallisation of cooling magmas. When it forms it often contains trace amounts of uranium, which decays into (amongst other things) lead at a known rate. Since lead (which has a much lower precipitation temperature) will not have been present in the original lava, it is possible to calculate the age of a zircon crystal from the ratio between these elements.

(a) Tectonic framework of the East Asia; (b) Simplified geological map of the Qinfang Trough and location of the study area; (c) Photo for the Late Devonian chert and tuff; (d) Concordia diagram and cathodoluminescence (CL) images of representative zircons for the tuff sample. Hu et al. (2018).

Eighteen zircons were subjected to this analysis. Seven of them produced ages older than 600 million years, whereas eleven produced ages of between 380 and 350 million years, consistent with a Devonian or Carboniferous age for the tuff layer. The presence of much older zircons in the sample does not undermine this, as zircons are extremely tough, and are known to be able to endure repeated cycles of subduction and volcanic eruption, nor is the broad spread of ages found in the Palaeozoic zircons, as ash deposits often contain mineral grains aggregated over a long period before being erupted.

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Hominin footprints from 1 500 000-year-old deposits near Ileret in northern Kenya.

One of the features that serve to distinguish Modern Humans from our closest living relatives, the Great Apes, is an upright bipedal stance unlike that seen in any other Primate. Based upon analysis of fossil skeletons, it is thought that this gait and posture appeared in the earliest members of the genus Homo, with earlier Australopithicene Hominins thought likely to have had a more Ape-like gait. However this is based almost entirely upon analysis of the bones of the legs and pelvis, with foot bones extremely rare (a set of eleven isolated foot bones from 1.8 million-year-old deposits at Dmasini in Georgia have been attributed to Homo erectus, but beyond this the foot bones of early Homo are unknown). One method that has proved extremely useful when studying non-Hominin terrestrial animals is analysis of preserved footprints, which can reveal a great deal about both the posture and gait of the animals, however fossil Hominin footprints are also extremely rare; a set of 3.7 million year old footprints from Laetoli in Tanzania have been attributed to Australopithicua afarensis, but footprints assignable to early members of the genus Homo are extremely rare.

In a paper published in the journal Scientific Reports on 12 July 2016, a team of scientists led by Kevin Hatala of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology and the Center for the Advanced Study of Human Paleobiology at The George Washington University describe a series of Hominin footprints from the 1 500 000-year-old Ileret Tuff Complex in northern Kenya, and the implications that can be derived from these.

The tracks comprise 97 discrete footprints from five sites, representing 23 trackways made by 15-23 individuals (depending on whether some individuals made more than one trackway). The tracks were laid down in soft mud rich in volcanic ash close to Lake Turkana and covered by fresh sediment within a few hours of their formation. The footprints range from 20.5 cm to over 30 cm in length.

Schematic maps of excavated footprint surfaces at sites FE3 and FwJj14E. Map of the Ileret area (lower left) shows the locations of sites FE3 and FwJj14E, marked by black stars. Schematic maps of the excavated surfaces at FE3 (top left) and the FwJj14E Upper Footprint Layer (right) show the presence of multiple trackways across each of these surfaces. Print size analyses indicate that the groups of individuals represented at each site consist of predominantly males. Multiple trackways at FwJj14E show parallel directional movement and similar preservation states, suggesting that they could represent a group traveling together. Note that the schematic map of the FwJj14E surface has been rotated relative to North for visualization purposes. Solid red lines mark borders of the current excavations, and the same geological layers that preserve footprints are known to extend beyond these borders. Dashed red lines indicate the finite edge of the preserved surface, as areas beyond these lines have been lost due to erosion. The schematic map of the Ileret area was created by Neil Roach, using a map generated in ArcGIS software version 10.2. Hatala et al. (2016).

Based upon the size of the footprints the tracks are thought to have been made by individuals with an average adult body mass (the smallest set of tracks are thought to have come from a child, with all the others thought to be adults) of 48.9 kg. This is comparable to the average adult body mass of the modern Daasanach people (52.6 kg), who inhabit southwestern Ethiopia, southeast South Sudan and northwest Kenya, including the area around Lake Turkana, and also comparable to the estimated size derived for a series of 800 000-year-old footprints from Happisburgh in Norfolk, England, attributed to Homo antecessor, and considered to be the oldest-known Hominin footprints outside of Africa (48-52 kg).

1.5 Ma hominin tracks from Ileret, Kenya. Representative images of hominin tracks uncovered in the Ileret area between 2007 and 2014. These tracks come from five different sites within  about 1.5 km of each other. Some tracks show deterioration and overprinting, while many preserve fine detail, indicating that they were rapidly hardened and covered with sediment. No two sites represent the same continuous surface, as all come from different stratigraphic levels within the Ileret tuff complex. The total sample includes 97 hominin tracks produced by at least 20 different individuals. Hatala et al. (2016).

Three Hominin species are thought to have been present in the Turkana Basin 1 500 000 years ago, Paranthropus boisei, Homo habalis and Homo erectus. Of these only Homo erectus is thought to have been large enough to have made the Ileret footprints, the other species being considerably smaller. Morphological analysis of the footprints suggested that the weight distribution on the foot and gait of the track-makers was similar to (but not identical to) that of habitually barefoot Daasanach individuals living in the area today, but quite different to that of the makers of the 3.7 million year old footprints at Laetoli in Tanzania (probably made by Australopithicua afarensis, and certainly by an Australopithecine rather than a member of the genus Homo).

Forefoot depth profiles of modern human and fossil hominin footprints. Boxplots compare regional depth profiles of modern human footprints (n = 490 footprints from 41 individuals) to those of the 1.5 Ma Ileret (n = 11 footprints from 8 trackways) and 3.7 Ma Laetoli (n = 5 footprints from 1 trackway) Hominin tracks. Top row represents depths across the toes while bottom row represents depths across the metatarsal heads. In each plot, medial is left and lateral is right. The image at far left shows the distribution of pressure including the path of the centre of pressure, plotted as a dashed black line, during a typical human walking step. The overall forefoot morphology of the Ileret tracks closely resembles that of human tracks and provides evidence of a human-like medial weight transfer. The Laetoli tracks are distinct from those of Modern Humans and the Ileret Hominins, and reflect a different pattern of foot biomechanics. Note that scales differ only for the purpose of better visualizing the variation within the relatively smaller fossil samples. In all boxplots, the box encloses the 25–75% interquartile range, the bold line represents the median, and the upper and lower whiskers extend to the largest and smallest observations within a distance of 1.5 times the interquartile range above and below the limits of the box. Hatala et al. (2016).

Homo erectus is thought to have shown far higher sexual dimorphism than Modern Humans (i.e. the difference in size between males and females was more pronounced), for which reason it was considered to assign sexes to the makers of the tracks. Using this methodology it was calculated that sixteen of the trackways (representing 8-16 individuals) were made by substantially larger, presumably male individuals (the alternative hypothesis, that all the individuals were female, representing the size range of female Homo erectus individuals, with larger male footprints not present, was deemed to be less likely). This does not rule out the possibility that some of the smaller, presumed female, footprints were made by smaller, possibly subadult, males.

This high proportion of male individuals (8-16 adult males in a group of 15-25 individuals) is remarkable, in that it is unlike the population structure of any known Primate species, or indeed Mammal of any kind, and is unlikely to represent a reproductively viable population. Hatala et al. suggest that this may indicate that the trackways were made not by an entire population but by a sub-set of that population travelling with a specific purpose. This may represent the division of labour amongst a hunter-gatherer society, something which is known in both Modern Human and Great Ape populations today, or possibly the patrolling of a border of a territory held by one group of individuals against incursions by members of another group, behaviour which is known in both Modern Humans and Chimpanzees, and which in both cases is carried out by smaller groups of individuals from within a larger population, with those smaller groups predominantly or exclusively made up of adult males.

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Hominin rib from Sterkfontein Caves. Sterkfontein Caves is a palaeoarchaological excavation site about 40 km to the northwest of Johannesburg in Gauteng State, South Africa, which forms part of the Maropeng Cradle of Humankind World Heritage Site has previously produced a...

A Hadrosaurid Dinosaur trackway from the Denali National Park in Alaska.                           The preserved tracks of ancient animals such as Dinosaurs can provide insights into their lifestyles and biology that could not be determined by examination of bones alone, although such data needs to be interpreted carefully. Such studies can potentially provide data on herding or other social...

Reconstructing the Paluxy River Dinosaur Chase Sequence.                                            In 1940 palaeontologist Roland Bird of the American Museum of Natural History in New York described and partially excavated a sequence of Dinosaur footprints along the Paluxy River at Glen Rose in Texas. In...

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Didymodon novae-zelandiae: A new species of Moss from Manukau Harbour, New Zealand.

Mosses are among the simplest and most ancient groups of plants. They lack flowers, seeds and roots, and only have very simple vascular systems. Despite this primitive nature they are still some of the most abundant plants today, due to their ability to colonise short-lived environments and live upon other plants.

In a paper published in the journal Phytotaxa on 3 May 2016, Jessica Beever of Landcare Research and Allan Fife of the Allan Herbarium describe a new species of Moss from the northern shore of the Manukau Harbour on the Auckland Isthmus of North Island, New Zealand.

The new species is placed in the genus Didymodon and given the specific name novae-zelandiae, in reference to the country where it was discovered. The Moss was found growing at a single site on a vertical sea-cliff made up of volcanic tuff (rock formed from ash) shaded by a canopy of Pōhutukawa (Metrosideros excelsa) trees. The plants brownish in colour and were small even for a Moss, with stems reaching 1-2 mm in length.

Didymodon novae-zelandiae habit with capsules. Beever & Fife (2016).

Areas of the cliff colonised by Didymodon novae-zelandiae were apparently more easily colonised by a larger Moss, Bryum clavatum, which was able to settle in such patches then competitively exclude the smaller Didymodon novae-zelandiae. This process, called succession by ecologists, is common in plat communities, where one plant modifies an environment in a way that makes it suitable for a second plant to take over and exclude the original coloniser. However the tuffa cliffs where the Mosses were found were extremely soft and poorly consolidated, with areas of the cliff surface regularly falling away and revealing fresh surface, suitable for colonisation by Didymodon novae-zelandiae but not Bryum clavatum. A more serious threat to the whole ecosystem appeared to come from invasive Kikuyu Grass (Cenchrus clandestinus) which was begging to settle soft unstable sediments at the base of the cliff.

 Type locality of Didymodon novae-zelandiae on Manukau Harbour foreshore. Didymodon novae-zelandiae (position arrowed) on the cliff face, below a denser band of vegetation (mainly Bryum clavatum), some 1.5 m above high tide mark. The remains of trunks of trees buried by eruption of nearby Mount Maungataketake can be seen in the cliff base both to the right and left of the standing figure. The large Pōhutukawa tree (Metrosideros excelsa) to the right, above, has now fallen from the cliff. Jessica Beever in Beever & Fife (2016).

Didymodon novae-zelandiae was found growing only at a single site, on a poorly consolidated volcanic cliff. Such habitats are not common, even in volcanic New Zealand, however the small size of the Moss does leave the possibility that it is present in other environments and has been overlooked. For this reason Beever and Fife suggest that it be classified as an Data Deficient Endemic Plant for conservation purposes.

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Mosses from Late Eocene Rovno Amber. Mosses are thought to be among the most ancient of plant groups, and still make up a significant proportion of all plant communities. They are an ancient group, considerably predating vascular plants such as...

Two new species of Moss from the Permian of Brazil.                                                  Mosses (Bryophytes) are simple plants which lack vascular systems to pump water and nutrients from a root system, instead relying on what they can absorb through their leaves, and generally only reaching a few cm in height. This means that they are at their... 

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