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fossils

Imaggeo on Mondays: A prehistoric forest

Imaggeo on Mondays: A prehistoric forest

This stunning vista encompasses the south-western wilderness of Tasmania as seen from the Tahune air walk 60 m above the Huon river valley. In front lies the beginning of a huge UNESCO World Heritage Site, covering almost a fourth of the area of Tasmania. The site mostly consists of a pristine, temperate rainforest of Gondwanan origin that is home to the tallest flowering trees in the world; Eucalyptus spp. reach up to 100 m height in this region.

“I have never tasted the sense of a more remote place than this one. Give me more,” says Vytas Huth, who captured this stunning shot.

Gondwana was a supercontinent, consisting of present day Africa, South America, India, Madagascar, Australia and New Zealand. It formed when the even larger supercontinent of Pangaea broke up 250 million years ago.

Slowly, Gondwana started to break apart too. India tore away first, followed by Africa and then New Zealand. By the end of the Cretaceous, 65 million years ago, only South America, Australia and Antarctica remained joined.  It took a further 20 million years before Australia and Antarctica separated.

By the time Australia started being pulled northwards, the first glaciers were forming on Antarctica, as it began freezing over. Atop the old rocks which made up its bulk, animals and plants of ancient origin, travel northwards with the Land Down Under.

Because India and Africa broke away from the supercontinent so early on, few hallmarks of ancient Gondwana wildlife are left in their present biodiversity. In contrast, Australia and Tasmania remained connected to Antarctica and South America much longer and there are clear similarities in species across these continents.

“Fossil evidence suggests that temperate rainforest once extended across Australia, Antarctica, South America and New Zealand around 45 million years ago. Such fossils and the surviving species in Tasmania provide evidence of the ancient link to Gondwana”, reports the Tasmania Parks & Wildlife Service.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Livers, guts and gills: understanding how organisms become fossils

Livers, guts and gills: understanding how organisms become fossils

It’s 10am and Thomas Clements, a 3rd year palaeobiology PhD Student, is getting ready to check on his latest experiment. Full kited up in what can only be described as a space suit, Thomas carefully approaches the fume cupboard home to his latest specimen: a decaying seabass, balanced on a specially designed ‘hammock’ in a tank of salty water. Opening the lid to check on the rotting fish, Thomas is hit by the smell, so atrocious the fume hood and protective overalls only go some way toward shielding his sense of smell. It might be a bleak start to the day, but it is central to Thomas’ research.

While the fossil record is dominated by the hard mineralised parts of organisms such as shells, teeth and bones, in the past few years palaentologists have started to rely on different fossilised remains and techniques to discover more about extinct animals.

“In fact, soft-bodied fossils are much more informative about the anatomy, physiology, ecology and behaviour of ancient organisms. They also give scientists a much better idea as to the type of conditions, ecosystems and environments in which the organisms lived,” explains Thomas.

However, before the vital clues held in the remains of soft-bodied fossils can be accurately interpreted by researchers, the processes which cause them to be preserved in the first instance must be fully understood too. This is where Thomas’s smelly study of decaying fish carcases comes in. Using seabass, because its genealogy can be traced back in time (organisms related to the blue fish are known to exist in the ancient fossil record), Thomas aims to better understand how decay processes affect the fossilisation potential of soft-tissues – especially of internal anatomy.

Thomas injects the silica gel around the probes to make sure the incisions are sealed. You can see the fish in it’s hammock. (Credit: Thomas Clemens)

Thomas injects the silica gel around the probes to make sure the incisions are sealed. You can see the fish in it’s hammock. (Credit: Thomas Clemens)

Along with the Palaeobiology Lab Group at Leicester University, Thomas has devised a series of novel experiments to investigate the process. Because he is particularly interested in how internal organs decay, Thomas cuts millimetre sized incisions into the fish, sourced from a local fishmongers, to place probes into liver, guts, stomach and even kidneys. The chemical data measured by the probes allows him to unravel both the timing and sequence of anatomical decay of the different organs.

“One of the most important parts of the experiment is to accurately recreate the natural death of the animal,” describes Thomas.

That is why it is vitally important that the wounds caused by the incisions are fully sealed with inert silica gel so as not to speed up the decay process. This also means that before any experiment, he painstakingly practices cutting and sealing for hours. By the end of his practice runs he is intimately familiar with the exact location of each internal organ and able to perform only the smallest cuts required to insert his probes.

Recreating the conditions under which an ancient fish would decay is also important. Surgical incision complete, probes inserted ready to acquire data, the fish is gently placed on a hammock of inert plastic netting (again, so that no chemicals plastic may give off will interfere with the natural break down of the body parts) and lowered into an aquarium of salty water.

Thomas’ experiments are sustainable and environmentally friendly too! Rather than placing the hammock directly on the tank floor, it is suspended in the water, by way of plastic ropes attached to the corners of the aquarium. This means that as the fish is left to decompose over time, most fish parts sink towards the base of the tank an eventually dissolve in the water – making it extremely foul-smelling, as you might imagine! Once the experiment is complete, whatever fish parts may remain on the hammock can be simply discarded and the (washed) plastic used in a new experiment.

Thomas teaches visiting PhD student, Yujing Li, about the anatomy of a Seabass. (Credit: Thomas Clemens)

Thomas teaches visiting PhD student, Yujing Li, about the anatomy of a Seabass. (Credit: Thomas Clemens)

The experiments performed so far show that the decay process is actually very quick. After 60 days, the majority of the fish has fully decomposed, with only fins and very small tissue parts remaining. It takes no more than 20 days for muscle fibres to disappear and as little as five days for ultra-structures to break down. Through his work, Thomas now knows that the preservation of soft tissues during fossilisation has to happen very quickly or conditions have to be just right.

Thomas thinks that “slowing down the decay process is what gives soft-bodied parts a better chance of preservation.”

This is why during the experiments he has been testing how changes in the conditions, from lowering the water temperature, reducing agitation of the tank, changing salinity or even reducing bioturbation (the disturbance of sediment caused by sea floor dwelling critters),  affect how likely it is for tissues to be preserved.

Despite the advances and better understanding gained through the experiments, enigmatic questions still remain: why are some organs, such as guts, often found preserved in the fossil record, but why are others, such as eyes, so much rarer? And so, Thomas’ work in the lab, complete with rotting fish, surgical gloves, spacesuit-like protective equipment and stomach turning smells continues.

By Laura Roberts Artal, EGU Communications Officer

Thomas Clements presented his work at the 2016 EGU General Assembly, at a press conference entitled: How ancient organisms moved and fed: finding out more from fossils. The full press conference can be streamed here. In addition, the work was presented in session SSP4.2: Experimental solutions to deep time problems in palaeontology. Thomas’ abstract can be found here.

Geosciences Column: The Oldest Eurypterid

Geosciences Column: The Oldest Eurypterid

The name of a newly found fossil of sea scorpion draws inspiration from ancient Greece warships and is a unique example of exceptional preservation, shedding light on the rich life of this bygone sea critter, explains David Marshall of Palaeocast fame. To learn more about the importance of giving new fossils names and what Pentecopterus decorahensis (as the new fossil is formally called) teaches us about a crucial time for biodiversification, read on!

It is considered best-practice that organisms, extinct or extant, be given a descriptive name. Triceratops, or ‘three horned-face’, is a perfect example of this. However scientists have often utilised some poetic license with this: Tyrannosaurus rex translates as ‘tyrant lizard king’, referring to its unrivalled size and ferocity, and Brontosaurus as ‘thunder lizard’, envisioning the noise produced by the placement of one of its gigantic legs. Recently the etymology of some names has become somewhat less poetically-descriptive and more, shall we say, ‘tabloid-newspaper-friendly’. The publication of names such as Dracorex hogwartsia, translating as ‘dragon king of Hogwarts’, do conjure images, even if it is done with a lot of artistic license. One animal with an equally abstract, but appropriate, name is described in BMC Evolutionary Biology today as Pentecopterus decorahensis.

Pentecopterus is a newly identified species of eurypterid, or ‘sea scorpion’. Eurypterids are an extinct group of chelicerates, the group containing the terrestrial arachnids (such as spiders and scorpions) and the aquatic ‘merostomes’ (represented today solely by the horseshoe crabs). The sea scorpions bear a close morphological resemblance to their namesakes, but perhaps may have been more closely related to horseshoe crabs. They were active predators or scavengers in the Paleozoic seas, between the Ordovician and Permian periods, approximately 460 – 250 million years ago. Some crawled along the ocean floor, whilst others were capable of limited swimming. Some reached incredible size, with the largest arthropod yet discovered, Jaekelopterus, estimated to have measured up to 2.5m.

Whilst most were quite small and generally unremarkable to look at, some eurypterids were truly the things of nightmares. Pentecopterus was a megalograptid: a particularly large and well-armed eurypterid family, typically measuring between 0.75 and 1.5m. Their appendages bore an array of inward-facing spikes, perfect for ambush, but without jaws, teeth or the sophisticated injection of enzymes, they (as with all eurypterids) would have simply shredded their prey into small enough pieces to eat. These were undoubtedly active predators, built as if solely for offence.

Results of the phylogenetic analysis plotted as an evolutionary tree. All of the branches of the tree leading to Pentecopterus must have occurred before we see our first Pentecopterus specimen (solid box). We can therefore infer ‘ghost ranges’ (dashed lines) for many eurypterid species and groups, where we believe they existed, but haven’t found fossils yet. Examination of rocks within the ghost ranges may yield new finds.

Results of the phylogenetic analysis plotted as an evolutionary tree. All of the branches of the tree leading to Pentecopterus must have occurred before we see our first Pentecopterus specimen (solid box). We can therefore infer ‘ghost ranges’ (dashed lines) for many eurypterid species and groups, where we believe they existed, but haven’t found fossils yet. Examination of rocks within the ghost ranges may yield new finds. Image credit: James C. Lamsdell et al / BMC Evolutionary Biology

Pentecopterus was discovered close to Decorah, Iowa, (hence the species name decorahensis) and is the oldest eurypterid yet described, hailing from the Darriwilian Stage of the Ordovician Period, some 467.3 – 458.4 million years old. This was a time of great change; the Ordovician biosphere underwent an explosion of species, form and ecology, in what is now dubbed the ‘Great Ordovician Biodiversification Event’. Organisms, previously confined to in and around the sea floor in the Cambrian period, began inhabiting the whole water column. Photosynthesising plankton took off (figuratively and literally) and the oceans were filled with new food webs based on this primary productivity. Sitting close to the top of the pile was Pentecopterus, a new kind of predator: large, armour-clad and armed to the teeth.

The genus name Pentecopterus is derived from marriage of the Greek words Πεντηκόντορος (Penteconter) with φτερός (–pterus, meaning wing) as the standard suffix for eurypterid genera. The Penteconter is a ship from the Archaic Period of Ancient Greece. This period saw the rapid expansion of the population of Greece, the formation of the city-state and founding of colonies. The Archaic period was a time of great social, political and economic change. This was primarily facilitated by the relationship the Ancient Greeks had with sea. But up until this time, there was little diversity in form of vessels; form did not necessarily follow function.

The Penteconter changed this. A vessel powered by 50 men (the name translating as fifty-oared), it was fast, manoeuvrable and built solely for aggression. It is considered to be the world’s first warship.

But far beyond the tabloid media coverage of ‘Oldest killer sea scorpion found’, and even my fondness for its poetical name, Pentecopterus is quite a remarkable specimen for our understanding of eurypterids.

Reconstruction: Scientific reconstruction of Pentecopterus. A, Dorsal view of a complete specimen. B, Genital segment. C, Ventral view of headshield. The semi-circular area is where the appendages would have inserted. D, Ventral view of prosoma with appendages in place. Scale 10cm.

Reconstruction: Scientific reconstruction of Pentecopterus. A, Dorsal view of a complete specimen. B, Genital segment. C, Ventral view of headshield. The semi-circular area is where the appendages would have inserted. D, Ventral view of prosoma with appendages in place. Scale 10cm. Image credit: James C. Lamsdell et al / BMC Evolutionary Biology

Despite most of the Pentecopterus specimens being disarticulated or fragmentary, with parts of the animal still yet to be discovered, there are enough pieces to put together a very good picture of its external anatomy. From the presence or absence of spines on certain parts of its appendages, this new species can clearly be assigned to the megalograptid family. For various anatomical reasons, the megalograptids have long been considered to be one of the most primitive groups of eurypterids, placed right at the base of the eurypterid ‘family tree’, with Pentecopterus as the oldest yet found supporting this theory. However, a phylogenetic analysis (a hypothesis of likely relationship based on numbers of shared anatomical characteristics) conducted on the eurypterid group provided some interesting ramifications.

The analysis placed the megalograptids with some other families belonging to the larger group Carcinosomatoidea. The interesting thing is that all other carcinosomatoids are typically at the top-end of the eurypterid family tree. Moving the megalograptids up from the bottom to join them at the top now means that we have one of the highest branches of the tree appearing first in geological time. The implication of this is that the whole tree has to be moved back in time. All the branches and splits that happen before we get to our carcinosomatoid group have to have occurred earlier than the time at which we find Pentecopterus. Whilst Pentecopterus is the earliest and most ‘primitive’ member of the megalograptids and carcinosomatoids, it cannot be the first eurypterid.

So, a quick recap: we found the oldest-yet eurypterid, we figured out it can’t actually be the first and we named it after a boat. And yet, we still haven’t got to the most-significant details of Pentecopterus. This lies within the exquisite preservation of the fossils.

If you are familiar with palaeontology, you may understand the fossil record is biased towards the preservation of the hard parts of organisms. The hard parts are useful and can tell us a lot about organisms: how they walked, how they ate, how they protected themselves, but most of the important information is lost. Consider your own body and the importance of your soft tissues and organs. Your sight, your touch, your taste, your reproductive organs. None of these would be preserved under normal circumstances. Soft-body preservation is exceedingly rare, but can provide unparalleled insights into extinct organisms. We have skin impressions from dinosaurs, muscle fibres from worms and optical pigments in squid. Pentecopterus has no soft-body preservation, but then again, it doesn’t need it.

Arthropods subscribe to a different ethos of construction; they wear their hard parts on the outside. This means that all their interactions with the environment occurs through their exoskeleton. Their eyes are hard and both their touch and taste is conducted through sensory hairs projecting through the hard cuticle. In Pentecopterus we find exceptional hard-body preservation. The fossils, though incomplete and disarticulated yield a treasure-trove of ecological information. The ‘teeth’ of Pentecopterus come equipped with thick spinose hairs, the legs and body bear the insertion sockets of finer hairs and swimming paddles have rows of sockets along the edges. What we’re seeing is how this organism sensed its environment. Although this information isn’t unique within eurypterids, it is exceedingly rare and this new species provides an essential point of comparison which hopefully will allow us to distinguish the exact function of the different hair types.

The Great Ordovician Biodiversification Event went on to shape the biosphere. It was a time of great change and whilst we may not know all of the events that occurred at the time, we may at least be able to discover how Pentecopterus felt about it.

By David Marshall, PhD student at the University of Bristol.

Reference

J. C. Lamsdell, Briggs D.E.G, Liu H.P., et al.: The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa, BMC Evolutionary Biology, doi 10.1186/s12862-015-0443-9, 2015

Imaggeo on Mondays: Escullos

Imaggeo on Mondays: Escullos

This picture shows a Quaternary aeolianite fossil dune at the Escullos beach, in the Nature Reserve of Cabo de Gata (Almeria, Spain). Originally a soft accumulation of sand grains, shaped by the wind into large mounds and ridges, the dunes eventually turn into rock. As the sediments compact under their own pressure and expel any moisture and fluids retained within them, they become lithified and become the structure seen in this week’s Imaggeo image. This particular example is a richly fossilifeorous and contains abundant cidaroid spines. Cidaroids are primitive forms of sea urchins, but unlike the more familiar, well rounded spike covered sea hedgehogs, their spikes are much more separated and sparse.

A present day cidaroid. Note the sparse and relatively flat spines. Credit, Alicia Morugán.

A present day cidaroid. Note the sparse and relatively flat spines. Credit, Alicia Morugán.

Almeria is the eastern most province of Andalucia, located in South East Spain. Almeria province is geologically very interesting as the relationships between tectonics, sedimentary geology and geomorphology are evident throughout the landscape. The province lies within the Baetic Cordillera, an Alpine mountain chain resulting from the collision of the micro-Iberian and African plate from Late Mesozoic to Middle Cenozoic times. This characteristic makes it very tectonically active. Furthermore, Almeria province has the driest climate in Europe, resulting in mean annual precipitation of less than 300 mm. In terms of geomorphology, quaternary alluvial fans are the most common structure in the region. Geologically speaking, aeolianite rocks are the most common rock in the region. A final thanks: thanks Maria Burguet for support editing the picture.

By Alicia Morugán, Universitat de València, València, Spain

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

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