pentecopterus, a giant sea scorpion

Journal reference: James C. Lamsdell, Derek E. G. Briggs, Huaibao P. Liu, Brian J. Witzke, Robert M. McKay. The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa. BMC Evolutionary Biology, 2015; 15 (1) DOI: 10.1186/s12862-015-0443-9

Eurypterids are a diverse group of chelicerates known from ~250 species with a sparse Ordovician record currently comprising 11 species; the oldest fully documented example is from the Sandbian of Avalonia. The Middle Ordovician (Darriwilian) fauna of the Winneshiek Lagerstätte includes a new eurypterid species represented by more than 150 specimens, including some juveniles, preserved as carbonaceous cuticular remains. This taxon represents the oldest described eurypterid, extending the documented range of the group back some 9 million years.

Results

The new eurypterid species is described as Pentecopterus decorahensis gen. et sp. nov.. Phylogenetic analysis places Pentecopterus at the base of the Megalograptidae, united with the two genera previously assigned to this family by the shared possession of two or more pairs of spines per podomere on prosomal appendage IV, a reduction of all spines except the pair on the penultimate podomere of appendage V, and an ornamentation of guttalate scales, including angular scales along the posterior margin of the dorsal tergites and in longitudinal rows along the tergites. The morphology of Pentecopterus reveals that the Megalograptidae are representatives of the derived carcinosomatoid clade and not basal eurypterids as previously interpreted.

Conclusions

The relatively derived position of megalograptids within the eurypterids indicates that most eurypterid clades were present by the Middle Ordovician. Eurypterids either underwent an explosive radiation soon after their origination, or earlier representatives, perhaps Cambrian in age, remain to be discovered. The available instars of Pentecopterus decorahensis suggest that eurypterids underwent extreme appendage differentiation during development, a potentially unique condition among chelicerates. The high degree of appendage specialization in eurypterids is only matched by arachnids within chelicerates, supporting a sister taxon relationship between them.

Pentecopterus decorahensis, prosomal ventral plate. a SUI 139914, posterior lobe of lateral portion of ventral plate. b SUI 139978, lateral portion of ventral plate showing carapace locking mechanism (arrowed). c SUI 139936, anterior portion of ventral plate including rostrum, retained on shale. d SUI 139936, posterior portion of ventral plate shown in Fig. 1c including linguoid projection, removed from sediment. e SUI 1139921, linguoid projection. f SUI 139917 part, ventral plate. g SUI 139917 counterpart, lateral portion of ventral plate. h SUI 139916, lateral portion of large ventral plate. Scale bars = 10 mm Lamsdell et al. BMC Evolutionary Biology 2015 15:169 doi:10.1186/s12862-015-0443-9

Pentecopterus decorahensis, prosomal ventral plate. a SUI 139914, posterior lobe of lateral portion of ventral plate. b SUI 139978, lateral portion of ventral plate showing carapace locking mechanism (arrowed). c SUI 139936, anterior portion of ventral plate including rostrum, retained on shale. d SUI 139936, posterior portion of ventral plate shown in Fig. 1c including linguoid projection, removed from sediment. e SUI 1139921, linguoid projection. f SUI 139917 part, ventral plate. g SUI 139917 counterpart, lateral portion of ventral plate. h SUI 139916, lateral portion of large ventral plate. Scale bars = 10 mm
Lamsdell et al. BMC Evolutionary Biology 2015 15:169 doi:10.1186/s12862-015-0443-9

 

This is an artist's rendering of Pentecopterus. Credit: Patrick Lynch/Yale University

This is an artist’s rendering of Pentecopterus.Credit: Patrick Lynch/Yale University

just how good is the fossil record?

Everyone is excited by discoveries of new dinosaurs – or indeed any new fossil species. But a key question for palaeontologists is ‘just how good is the fossil record?’ Do we know fifty per cent of the species of dinosaurs that ever existed, or ninety per cent or even less than one per cent? And how can we tell?

It all depends on how we read the record – the sum total of all the fossils in rocks and in museums. In a new study published today, Professor Mike Benton of the University of Bristol has explored how knowledge about has accumulated over the past 200 years, since the first dinosaur was named in 1824. His research does not answer the question once and for all, but it suggests that strong caution is needed with some popular methods to ‘correct’ the fossil record.

Professor Benton said: “In the past ten years, many palaeontologists have tried to find the true pattern of evolution by using measures of sampling to estimate where the fossil record is well known or poorly known. But it turns out that many of the popular methods are not doing what they are supposed to.’

Professor Benton reconstructed year-by-year, through the history of research on dinosaurs, from 1820 to 2015, how palaeontologists have discovered new species of dinosaurs, and how the patterns of discovery match the patterns of discovery of new geological formations. In fact, the patterns of discovery are closely linked: one or two new dinosaurs for each fossil-bearing geological formation that is newly explored.

The pattern of discovery of new dinosaur species and new dinosaur-bearing formations, as they accumulated through research time, from 1820 to the present day Read more at: http://phys.org/news/2015-08-good-bad-fossil-dinosaurs.html#jCp

The pattern of discovery of new dinosaur species and new dinosaur-bearing formations, as they accumulated through research time, from 1820 to the present day. Read more at: http://phys.org/news/2015-08-good-bad-fossil-dinosaurs.html#jCp

This close linkage has been explained in two ways: either rocks drive fossils, or fossils drive rocks. The usual view was that rocks drive fossils: palaeontologists were keen to find new dinosaurs, but could only find them if they looked at new rocks in a new part of the world. Therefore, it could be said that the availability of appropriate rocks biases our knowledge of dinosaurs (or any other fossil group).

The opposite view is that fossils drive rocks, and that palaeontologists usually go out looking for dinosaurs in a very focused way,, and when they find them they would often add a new dinosaur-bearing formation to the list. In this case, the limiting factor is not simply the rocks, because palaeontologists do not search steadily and evenly over the ground, but they go straight to spots where they hear there are bones to be found.

“I have been worried for a while that some of the popular correction methods actually make things worse,” Professor Benton said. “By removing the numerical signal of the formations, localities, or collections they were actually removing a huge amount of real information, and producing a resulting curve that is meaningless.

“The is clearly incomplete, and it is clearly biased by many factors, but many of the supposedly ‘corrected’ diversity curves we have seen recently may actually be further from the truth than the raw data.”

The new work does not answer the question of whether we know 50 per cent of dinosaur species or less than one per cent. But it does provide a clearer picture of why there is such a close correlation between dinosaur species numbers with formations, localities or collections. The numbers of all four are connected because they are all telling pretty much the same story, and they are measuring the same history of knowledge. It is not possible to separate one or other of these measures from the others and then try to use it as an independent yardstick of sampling.

 

Pigments in fossil feathers

A study provides multiple lines of new evidence that pigments and the microbodies that produce them can remain evident in a dinosaur fossil. In the journal Scientific Reports, an international team of paleontologists correlates the distinct chemical signature of animal pigment with physical evidence of melanosome organelles in the fossilized feathers of Anchiornis huxleyi, a bird-like dinosaur that died about 150 million years ago in China.

The idea that melanosomes, which produce melanin pigment, are preserved in fossils has been hotly debated among scientists during the last several years. Microscopic traces that to some scientists seem to resemble melanosomes, appear to skeptics to instead be similar-looking bacteria. The new study resolves the debate, said co-author Ryan Carney, a graduate student at Brown University, by adding a powerful second line of evidence: chemistry.

A fossilized Anchioris huxleyi, a bird-lke dinosaur, carries evidence of pigment and the subcellular organelles that made it. Credit: Thierry Hubin/RBINS

A fossilized Anchioris huxleyi, a bird-lke dinosaur, carries evidence of pigment and the subcellular organelles that made it.
Credit: Thierry Hubin/RBINS

“We have integrated structural and molecular evidence that demonstrates that melanosomes do persist in the fossil record,” said Carney, who helped design and write the study. “This evidence of animal-specific melanin in fossil feathers is the final nail in the coffin that shows that these microbodies are indeed melanosomes and not microbes.”

The finding has important implications for the interpretation of both past and future studies on fossil color, Carney said, and substantiates prior proposals that Anchiornis had some dark black feathers.

Signatures of animal pigment

In the new study, led by Johan Lindgren of Lund University in Sweden, the team used electron microscopes to observe what appear to be rod-like melanosome structures and imprints within the barbules of feathers all over the body.

That morphological evidence alone, however, would not advance the debate, so in addition the team performed two different kinds of chemical analyses to see if they could detect animal eumelanin pigment. They used both time-of-flight secondary ion mass spectrometry and infrared reflectance spectroscopy to discern the molecular signature of melanin in the samples. They compared those observed signatures with the signatures of modern-day animal eumelanin. The melanins were virtually identical, except for minor contributions from sulfur in the fossil, Carney said.

The researchers also analyzed the observed spectral signatures to compare them with melanins produced by various microbes, just to make sure that the pigments were not from any other source. The closest spectral agreement remained with an animal source, however.

“This is animal melanin, not microbial melanin, and it is associated with these melanosome-like structures in the fossil feathers,” Carney said.

Furthermore, no other types of molecules from potential microbes were detected.

In addition to Lindgren and Carney, the paper’s other authors are Peter Sjövall, Aude Cincotta, Per Uvdal, Steven Hutcheson, Ola Gustafsson, Ulysse Lefèvre, François Escuillié, Jimmy Heimdal, Anders Engdahl, Johan Gren, Benjamin Kear, Kazumasa Wakamatsu, Johan Yans and Pascal Godefroit.

The Swedish Research Council, the Crafoord Foundation and the National Geographic Society funded the research.

Gueragama sulamericana: Lizard Fossil

University of Alberta paleontologists have discovered a new species of lizard, named Gueragama sulamericana, in the municipality of Cruzeiro do Oeste in Southern Brazil in the rock outcrops of a Late Cretaceous desert, dated approximately 80 million years ago.

“The roughly 1700 species of iguanas are almost without exception restricted to the New World, primarily the Southern United States down to the tip of South America,” says Michael Caldwell, biological sciences professor from the University of Alberta and one of the study’s authors. Oddly however, iguanas closest relatives, including chameleons and bearded dragons, are all Old World. As one of the most diverse groups of extant lizards, spanning from acrodontan iguanians (meaning the teeth are fused to the top of their jaws) dominating the Old World to non-acrodontans in the New World, this new lizard species is the first acrodontan found in South America, suggesting both groups of ancient iguanians achieved a worldwide distribution before the final break up of Pangaea.

A terrestrial Noah’s Arc

“This fossil is an 80 million year old specimen of an acrodontan in the New World,” explains Caldwell. “It’s a missing link in the sense of the paleobiogeography and possibly the origins of the group, so it’s pretty good evidence to suggest that back in the lower part of the Cretaceous, the southern part of Pangaea was still a kind of single continental chunk.”

Distributions of plants and animals from the Late Cretaceous reflect the ancestry of Pangaea when it was whole. “This Gueragama sulamericana fossil indicates that the group is old, that it’s probably Southern Pangaean in its origin, and that after the break up, the acrodontans and chameleon group dominated in the Old World, and the iguanid side arose out of this acrodontan lineage that was left alone on South America,” says Caldwell. “South America remained isolated until about 5 million years ago. That’s when it bumps into North America, and we see this exchange of organism north and south. It was kind of like a floating Noah’s Arc for a very long time, about 100 million years. This is an Old World lizard in the new world at a time when we weren’t expecting to find it. It answers a few questions about iguanid lizards and their origin.”

This is an illustration of Gueragama sulamerica. Credit: Julius Csotonyi

This is an illustration of Gueragama sulamerica.Credit: Julius Csotonyi

The University of Alberta is a world leader in paleontology. This study was a collaboration between the University of Alberta and scientists in Brazil. Caldwell says of the collaboration, “It’s providing an opportunity for our students and research groups to expand our expertise and interests into an ever-increasing diversity of organisms within this group of animals called snakes and lizards.”

The lead author of the paper is Caldwell’s PhD student, Tiago Simoes, a Vanier scholar. “As with many other scientific findings, this one raises a number of questions we haven’t previously considered,” says Simoes. “This finding raises a number of biogeographic and faunal turnover questions of great interest to both paleontologists and herpetologists that we hope to answer in the future.”

In terms of next steps, Caldwell notes “Each answer only rattles the questions harder. The evolution of the group is much older than has been previously thought, which means we can push an acrodontan to 80 million years in South America. We now need to focus on much older units of of rock if we’re going to find the next step in the process.”

The findings, “A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana,” were published in the journal Nature Communications, one of the world’s top multidisciplinary scientific journals.

Malformed fossil plankton

Several Palaeozoic mass extinction events during the Ordovician and Silurian periods (ca. 485 to 420 to million years ago) shaped the evolution of life on our planet. Although some of these short-lived, periodic events were responsible for eradication of up to 85% of marine species, the exact kill-mechanism responsible for these crises remains poorly understood.

An international team led by Thijs Vandenbroucke (researcher at the French CNRS and invited professor at UGent) and Poul Emsbo (US Geological Survey) initiated a study to investigate a little known association between ‘teratological’ or ‘malformed’ fossil plankton assemblages coincident with the initial stages of these extinction events.

In a paper just published in Nature Communications, they present evidence that malformed fossil remains of marine plankton from the late Silurian (415 million years ago) contain highly elevated concentrations of heavy metals, such as iron, lead, and arsenic. These are well-known toxins that cause morphologic abnormalities in modern aquatic organisms; which led the authors to conclude that metal poisoning caused the malformation observed in these ancient organisms and may have contributed to their extinction and that of many other species.

Malformed (a) versus normal (b) plankton. Toxic metal contamination may be a previously unrecognized contributing agent to many, if not all, extinction events in the ancient oceans. Credit: Image courtesy of Ghent University

Malformed (a) versus normal (b) plankton. Toxic metal contamination may be a previously unrecognized contributing agent to many, if not all, extinction events in the ancient oceans.Credit: Image courtesy of Ghent University

Documented chemical behavior of these metals, which correlates with previously observed disturbances in oceanic carbon, oxygen and sulphur signatures, strongly suggests that these metal increases resulted from reductions of ocean oxygenation.

Thus, metal toxicity, and its expressions in fossilized malformations, could provide the ‘missing link’ that relates organism extinctions to widespread ocean anoxia. As part of a series of complex systemic interactions accompanying oceanic geochemical variation, the mobilisation of metals in spreading anoxic waters may identify the early phase of the kill-mechanism that culminated in these catastrophic events.

The recurring correlation between fossil malformations and Ordovician-Silurian extinction events raises the provocative prospect that toxic metal contamination may be a previously unrecognized contributing agent to many, if not all, extinction events in the ancient oceans.

REF: Thijs R. A. Vandenbroucke, Poul Emsbo, Axel Munnecke, Nicolas Nuns, Ludovic Duponchel, Kevin Lepot, Melesio Quijada, Florentin Paris, Thomas Servais, Wolfgang Kiessling. Metal-induced malformations in early Palaeozoic plankton are harbingers of mass extinction. Nature Communications, 2015; 6: 7966 DOI: 10.1038/ncomms8966

microtomography : A new tool in Paleontology

Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich have used computed microtomography (micro-CT) to identify to the species level an exceptionally wellpreserved fossil arthropod from the famous Chengjiang Lagerstätte in China.

Modern imaging methods make it possible to perform detailed, non-invasive studies on the internal structures of irreplaceable fossil specimens. Researchers led by Dr. Yu Liu of LMU’s Department of Biology II now demonstrate the power of this approach by using computed microtomography (micro-CT) to investigate a specimen recovered from the famous fossil beds of Chengjiang in southwestern China. The results of the study, which appear in the online Open Access journal “Scientific Reports,” demonstrate the ability of micro-CT to reveal anatomical details preserved inside fossil slabs.

The figure on the left shows a light micrograph of the fossil, while the microtomographic image right reveals fine details of structures hitherto concealed within the slab. Credit: Image courtesy of LMU

The figure on the left shows a light micrograph of the fossil, while the microtomographic image right reveals fine details of structures hitherto concealed within the slab.Credit: Image courtesy of LMU

The fossil Lagerstätte Chengjiang in China is a UNESCO World Heritage Site, which harbors a rich fossil assemblage dating from 520 million years ago. The rocks preserved here are among the oldest that document the so-called Cambrian explosion — the relatively abrupt appearance of a highly diverse, species-rich multicellular fauna in the fossil record. And many of the specimens discovered in these beds are extremely well preserved. In particular, their soft parts have left clear impressions in the sediments that accumulated here. Imprints of organisms with mineralized skeletons often extend for several millimeters below the surface of the slabs of sediment in which they are embedded. In order to study their structure, such specimens must first be removed from the surrounding rock matrix. “Because this inevitably involves the destruction of at least some of their fine structure, most of the published work on Chengjiang’s fossils is based on careful examination of surface structures with the help of optical and fluorescence microscopy,” as Yu Liu explains.

The LMU team now reports the first in-depth microtomographic study of a three-dimensionally preserved fossil from Chengjiang. The term micro-CT refers to a method in which multiple X-radiographs of a specimen are taken from different angles, and then assembled with the help of mathematical procedures to yield a three-dimensional model of the original. It is now a well-established analytical tool in palaeontology, but has not yet been widely applied to fossils from Chengjiang. Yu Liu’s study uncovers internal structures in a specimen recovered from the site, which allow the fossil to be identified as Xandarella spectaculum, a rare species of arthropod that shows similarities to the iconic (but now extinct) trilobites, and is known only from Chengjiang. The three-dimensional reconstruction reveals informative details of the fossil’s morphology, which had hitherto remained hidden in the rock matrix. On the basis of the new results, Yu Liu confidently asserts that “microtomography is a powerful technique for the analysis of the three-dimensionally preserved specimens recovered at Chengjiang.”

Meteorite impacts can create DNA building blocks

A new study shown that meteorite impacts on ancient oceans may have created nucleobases and amino acids. Researchers from Tohoku University, National Institute for Materials Science and Hiroshima University discovered this after conducting impact experiments simulating a meteorite hitting an ancient ocean.

These are chematics of nucleobases formation by meteorite impact on earth. Credit: Dr. Yoshihiro Furukawa

These are chematics of nucleobases formation by meteorite impact on earth.Credit: Dr. Yoshihiro Furukawa

With precise analysis of the products recovered after impacts, the team found the formation of nucleobases and amino acids from inorganic compounds. The research is reported this week in the journal Earth and Planetary Science Letters.

All the genetic information of modern life is stored in DNA as sequences of nucleobases. However, formation of nucleobases from inorganic compounds available on prebiotic Earth had been considered to be difficult.

In 2009, this team reported the formation of the simplest amino acid, glycine, by simulating meteorite impacts. This time, they replaced the carbon source with bicarbonate and conducted hypervelocity impact experiments at 1 km/s using a single stage propellant gun.

They found the formation of a far larger variety of life’s building blocks, including two kinds of nucleobases and nine kinds of proteinogenic amino acids. The results suggest a new route for how genetic molecules may have first formed on Earth.

Courtesy: Tohoku University. “Meteorite impacts can create DNA building blocks.” ScienceDaily. ScienceDaily, 18 August 2015. <www.sciencedaily.com/releases/2015/08/150818085751.htm>.

Montsechia, first aquatic angiosperm ?

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet’s earliest flowers, known as angiosperms.

“This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life,” said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences’ Department of Geological Sciences.

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country’s border with France.

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

This is a large intact specimen of the fossil, Montsechia. Usually only small fragmentary pieces of the fossil are found. Credit: David Dilcher

This is a large intact specimen of the fossil, Montsechia. Usually only small fragmentary pieces of the fossil are found.
Credit: David Dilcher

“A ‘first flower’ is technically a myth, like the ‘first human,'” said Dilcher, an internationally recognized expert on angiosperm anatomy and morphology who has studied the rise and spread of flowering plants for decades. “But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus.”

He also asserted that the fossils used in the study were “poorly understood and even misinterpreted” during previous analyses.

“The reinterpretation of these fossils provides a fascinating new perspective on a major mystery in plant biology,” said Donald H. Les, a professor of ecology and evolutionary biology at the University of Connecticut, who is the author of a commentary on the discovery in the journal PNAS. “David’s work is truly an important contribution to the continued quest to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence.”

The conclusions are based upon careful analyses of more than 1,000 fossilized remains of Montsechia, whose stems and leaf structures were coaxed from stone by applying hydrochloric acid on a drop-by-drop basis. The plant’s cuticles — the protective film covering the leaves that reveals their shape — were also carefully bleached using a mixture of nitric acid and potassium chlorate.

Examination of the specimens was conducted under a stereomicroscope, light microscope and scanning electron microscope.

The age of the plant at 125 million to 130 million years is based upon comparisons to other fossils in the same area, notably the freshwater algae charophytes, which places Montsechia in the Barremian age of the early Cretaceous period, making this flowering plant a contemporary of dinosaurs such as the brachiosaurus and iguanodon.

The precise, painstaking analysis of fossilized structures remains crucial to paleobotany, in contrast to other biological fields, due to the current inability to know the molecular characters of ancient plants from millions of years ago, Dilcher said.

This careful examination was particularly important to Montsechia since most modern observers might not even recognize the fossil as a flowering plant.

Montsechia possesses no obvious ‘flower parts,’ such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water,” he said. “The fruit contains a single seed” — the defining characteristic of an angiosperm — “which is borne upside down.”

In terms of appearance, Dilcher said, Montsechia resembles its most modern descendent, identified in the study as Ceratophyllum. Also known as coontails or hornworts, Ceratophyllum is a dark green aquatic plant whose coarse, tufty leaves make it a popular decoration in modern aquariums and koi ponds.

Next up, Dilcher and colleagues want to understand more about the species connecting Montsechia and Ceratophyllum, as well as delve deeper into when precisely other species of angiosperms branched off from their ancient forefathers.

“There’s still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth,” he said.

Ref: David L. Dilcherd et al. Montsechia, an ancient aquatic angiosperm. PNAS, August 2015 DOI: 10.1073/pnas.1509241112

How do continents break up?

When the western part of the super-continent Gondwana broke up around 130 Million years ago, today’s Africa and South-America started to separate and the South Atlantic was born. It is commonly assumed that enormous masses of magma ascended from the deep mantle up to higher levels, and that this hot mantle plume (the Tristan mantle plume) weakened the continental lithosphere, eventually causing the break-up of the continental plate of Gondwana.

A group of German scientists are now questioning this theory. On the basis of seismic measurements published in the current issue of the journal Geology, scientists from Potsdam (GFZ German Research Centre for Geosciences), Bremerhaven (Alfred-Wegener-Institute, AWI) and Kiel (GEOMAR) show that impacts of the mantle plume on the continental crust are actually surprisingly small. This is by no means in agreement with a large plume playing an important role in the break-up process. Accordingly, a dominant or controlling role of a mantle plume for the break-up of the continent is thus questionable.

 mantle plume

mantle plume

Hot ascending mantle plumes in the Earth’s mantle are an important driving force in plate tectonics. With an assumed diameter of the plume heads of up to several thousand kilometers, the amount of hot material ascending from the core mantle boundary at 2900 km depth is sufficient to migrate through the continental lithosphere. This process leads to the eruption of large volcanic material (flood basalts) at the Earth’s surface. This is also the case for Southern Africa and South America: the Parana/Etendeka/ flood basalt provinces are the direct consequences of the Gondwana break-up starting some 130 million years ago. Traces of the break-up process can be found on the newly formed ocean floor: the Walvis Ridge off the coast of Northern Namibia images the track of the mantle plume.

In order to study these processes, German scientists investigated structures which are related to the break-up process of Gondwana in the South Atlantic. The upwelling of large amounts of hot mantle material produces regions of crustal and mantle rocks with different seismic velocities (with respect to the surrounding, unaffected regions). In cooperation with colleagues from AWI and GEOMAR, and with the support of the Geological Survey of Namibia, scientists from GFZ have carried out extensive seismic investigations on and offshore Northern Namibia. The crustal structure was investigated along several seismic lines.

Overnight camp in Northern Namibia. Credit: C. Haberland, GFZ

Overnight camp in Northern Namibia.
Credit: C. Haberland, GFZ

“For the first time we could obtain images of the deeper crustal structure in the region where the Walvis Ridge joins the African continent, in order to study the impact of a mantle plume” explains Trond Ryberg from GFZ. “Our seismic investigations found a distinctive high-velocity anomaly in the lower crust between 20 and 40 km depth.” This region of anomalously high seismic velocities can be related to the intrusion of magmatic material in the lower crust of the Earth. This was expected according to the current perception. But surprisingly, the size of the anomaly was far too small to be created by a large plume head playing an active role in the break-up process. Trond Ryberg: “The crustal structure in the investigated region reflects the general process of continental break-up rather than the immediate impact of the plume head on the lithosphere. In addition, we were able to reconstruct the direction of the mantle plume flow.” It seems that the break-up of Gondwana in the South Atlantic and, in general, the role of mantle plumes during the continental break-up needs to be carefully re-evaluated.

Courtesy: GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre. “How do continents break up? Classical theory of mantle plume is put in question: New insights from South Africa.” ScienceDaily. ScienceDaily, 13 August 2015. <www.sciencedaily.com/releases/2015/08/150813092824.htm>.

Ichibengops : pre-mammal fossils from Zambia

Scientists at The Field Museum have identified a new species of pre-mammal in what is now Zambia. Thanks to a unique groove on the animal’s upper jaw, it was dubbed Ichibengops (Itchy-BEN-gops), which combines the local Bemba word for scar (ichibenga), and the common Greek suffix for face (ops). Put simply: Scarface.

Believed to be roughly the size of a dachshund, Ichibengops lived around 255 million years ago, and was a member of Therocephalia, a group of ancient mammal relatives that survived the largest mass extinction in history (the Permian-Triassic extinction). The species description was published in the Journal of Vertebrate Paleontology by University of Utah, University of Washington and Burke Museum, and The Field Museum.

Believed to be roughly the size of a dachshund, Ichibengops lived around 255 million years ago. Credit: Image courtesy of Field Museum

Believed to be roughly the size of a dachshund, Ichibengops lived around 255 million years ago.
Credit: Image courtesy of Field Museum

“Discoveries of new species of animals like Ichibengops are particularly exciting because they help us to better understand the group of animals that gave rise to mammals,” said Field Museum’s Kenneth Angielczyk, PhD, associate curator of paleomammalogy. “One interesting feature about this species in particular is the presence of grooves above its teeth, which may have been used to transmit venom.”

Indeed, venomousness is rare among mammals and their extinct relatives. Only a handful of modern mammals produce venom, including the platypus and certain species of shrews. One other extinct therocephalian, Euchambersia, has been suggested to be venomous, but even among ancient mammal relatives this is an exception rather than the rule. Although the trait is uncommon, it may have proved advantageous to carnivores by enabling them to better capture prey and defend themselves.

Angielczyk, whose work focuses on ancient mammal relatives, explained the importance of finding new species like Ichibengops. “By studying the effects of the Permian-Triassic mass extinction and the subsequent recovery, we can apply the lessons we learn to the mass extinction being caused by humans today.”