Geoscience Column: The Oldest Eurypterid

Geoscience 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.


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: Mola de Lord

Imaggeo on Mondays: Mola de Lord

From the easterly Atlantic waters of the Bay of Biscay to the Catalan wild coast (Costa Brava) in the west, the Spanish Pyrenees stretch 430 km across the north of the country. At the foothills of the Catalan Pyrenees you’ll find the Pre-Pyrenees. Despite not reaching the soaring heights of the peaks of the Pyrenees, they nonetheless offer important insights into the geology of the range and stunning panoramas, such as the one featured as today’s Imaggeo on Mondays image. In today’s post, Sarah Weick, a researcher at the Georg August University in Göttingen, explains why the foothills of the mountain belt are a structural geologist’s playground.

The picture was taken from the top of the flat-topped mountain ‘Mola de Lord’, with a beautiful view over the turquoise-blue water of the river Cardener and growth folds, characterised by a significant increase in throw with depth, caused by their syn-sedimentary development The over 1000 m-high mountain belongs to Vall de Lord, close to the Sant Llorenc Growth Structure, formed of folded sedimentary rocks of marine and continental origin that developed from Eocene to Oligocene and display local angular unconformities (where horizontally parallel sedimentary rocks are deposited atop previously tilted layers). Moreover, it is excellently preserved as a structure in the footwall of the Pyrenees and helps to understand how sedimentary deposits are reorganized during the development of a syn-sedimentary growth structure and how they may distribute between the foreland basin and the mountain belt. Outcrops on the mountain top are of conglomeratic composition with clasts and fossilized nummulites – lense-shaped single-celled sea creatures with shells that lived from Paleocene to Oligocene.

As a geologist, Mola de Lord is not the only remarkable location in Catalonia. On a greater scale, the table mountain belongs to the Spanish Pyrenees. There, hikers can experience parts of untouched nature, and witness the mountain’s geological past: from eroded carbonate karsts with unique shapes to the Ebro basin.

The Pyrenees are located in southwest Europe on the border between France and Spain. The Upper Cretaceous to Miocene collision and subduction of the Iberian microplate under the European plate initiated the orogeny, which went through two main phases. The tectonic changes during the Alpine Orogeny that started 66 Ma ago and some earlier Jurassic activity, caused a compressive regime and thus produced a lot of pressure that caused folding on different scales and the continuing orogenic growth. Deformation occurred also after the collision. The orogenic basement can be described by inherited folded formations over a granitic basement.

 By Sarah Weick, researcher at the Georg August University in Göttingen.


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

GeoEd: A Framework Too Far?

GeoEd: A Framework Too Far?

In this month’s edition of GeoEd, Sam Illingworth, former ECS PC representative and Lecturer of Science Communication at Manchester Metropolitan University, talks about a new framework introduced by the UK government to measure the quality of teaching at higher education institutions. Although Sam explores the issue from a UK perspective, there is no doubt cross over within the European realm. Also, this post is a great opportunity to start a discussion, how is the quality of teaching across European Universities measured? We’d love to hear from you if you have a view on the newly proposed framework or if you can tell us more about how teaching excellence is measured in your country.

The UK government recently announced that a Teaching Excellence Framework (TEF) would be introduced to UK universities. At the moment, the exact form of what this will look like is speculative, but it is expected that it will potentially use a set of “outcome-focussed” metrics to form the basis of financial incentives to improve university teaching. For example, those universities that perform well in TEF might be allowed to charge more than the current tuition fee cap of £9,000 per annum.

Whilst primary and secondary schools in the UK are used to having the quality of their teaching assessed via inspections from the Office for Standards in Education, Children’s Services and Skills (Ofsted), there has been something of a mixed reaction amongst UK academics as to whether or not the TEF is actually needed.

Aside from the fact that TEF will probably be a very costly exercise (some estimates of REF, the research equivalent of TEF were put at being in excess of £1 billion), it is difficult to imagine how you would accurately measure teaching excellence in universities, and if indeed there is any need to do so. After all, the 2015 UK National Student Survey reported that the majority of students are ‘satisfied’ with their university course, despite the £9,000 tuition fees.

Will TEF help lecturers wake up to better teaching practices? (Photo Credit: Love Krittaya)

Will TEF help lecturers wake up to better teaching practices? (Photo Credit: Love Krittaya)

However, would a TEF really be such a bad idea? Aside from the fact that it might be used as a further tool to ensure that the richest and most well attended universities keep on getting richer and more over subscribed, I think that there are a number of potential benefits to such a framework:

  1. It will encourage more peer-assessment amongst lecturers. Whilst previous attempts to enforce this have been a little heavy handed, learning from one another is an excellent way to develop your craft as a teacher.
  2. It will help to strengthen the ‘teaching track’ in academia as a route that is at least on a par with the more traditional ‘research track’. This in turn should also help to pave the way for more distinctive career paths. Just because you are a world-class researcher does not mean that you are a world-class teacher, but nor should you be punished / penalised for this if research is your main reason for employment and visa versa.
  3. It will help to place greater value on the importance of good teaching for retention rates etc. Given the amount of money that universities bring in from tuition fees, it is amazing that a greater value is not already placed on lecturers that excel in the role of teachers.
  4. It should provide a more useful comparison for students when applying to universities than the REF tables. After all, whilst as a student you want to attend a university with a good research reputation, it is far more important that you attend one that excels at teaching.

Obviously, in the field of the geosciences, there will be additional obstacles that must be overcome, for example how will lecturers be assessed on their ability to teach fieldwork skills, or to run successful residential trips? However, providing that the TEF is constructed following consultation with practicing lecturers and university administrators, these could all potentially be accounted for.

Hopefully TEF should inspire lecturers to think more like this (Photo Credit: BK)

Hopefully TEF should inspire lecturers to think more like this (Photo Credit: BK)

Whilst many may see TEF as a further box-ticking or hurdle-jumping exercise, if it is done correctly it offers university’s a fantastic opportunity to ensure that all of their students are being taught be lecturers who are good at lecturing, and who actually want to be there. The good lecturers have nothing to worry about (apart from potential promotion), those wanting to learn will have a framework to work towards, and those that don’t care about the quality of their delivery are probably better off out of the system anyway.

By Sam Illingworth, Science Communication Lecturer at Manchester Metropolitan University

Join the EGU Blog Network!

Join the EGU Blog Network!

After announcing earlier this week that we are sadly saying goodbye to the EGU network blog Between a Rock and Hard Place, the time has come to find a new blog to take their place. If you are an Earth, planetary or space researcher (a PhD student, an early career scientist, or a more established one) with a passion for communicating your work, we’d like to hear from you!

We currently feature blogs in palaeontology (Green Tea and Velociraptors), international development (Geology for Global Development), geochemistry (GeoSphere), atmospheric sciences (Polluting the Internet), and more! Initially, we are looking to fill the gap left in the network by Between a Rock and Hard Place, which covered broad themes within volcanology and petrology. But, with so much great geoscience out there, we’d love to receive blog proposals from more fields within the Earth, planetary and space sciences we don’t yet feature on the network. This also means we may not limit the addition to the EGU network to one blog; if there is more than one strong candidate we’ll consider expanding the network further.

The network aims at fostering a diverse community of geoscience bloggers, sharing accurate information about geoscientific research in a language understandable not only to fellow scientists but also to the broader public. You, as an expert in your own research area, are in a better position than we are to share recent development in your area of research.

The benefits: apart from your site gaining exposure by having its posts listed on the front page of the EGU website, we will also share highlights of your work on our social media channels (Twitter, Facebook, LinkedIn, Google+) and advertise the blog network at our General Assembly, which has over 12,000 attendees. And, of course, you’ll get to join a great community of bloggers!

With the exception of An Atom’s-Eye View of the Planet, the network blogs are authored by early career researchers. In this call for bloggers we are particularly keen to add diversity to the network, and particularly welcome applications from more established scientists.

Having an existing blog is not a requirement for application. However, if you don’t have a blog already, we’d like you to have at least some experience of writing for a broader audience, be it as a guest blogger, or contributing to outlets such as The Conversation, for instance. In this case, let us know what you’d like your blog to be called, what topics you would cover, and link to articles you’ve published in the past.

If you’d like your blog (or blog idea) to be considered for our network, fill out this form by 11th September.

Join the EGU Network blogs . Credit: ClkerFreeVectorImages (distributed via  pixabay)

Join the EGU Network blogs . Credit: ClkerFreeVectorImages (distributed via pixabay)

Please note that only blogs in English will be considered, as this is the EGU working language, and the language of the blog network. We particularly encourage applications from all European countries, not just English-speaking countries, but bloggers from outside Europe can also apply.

Feel free to contact the EGU Communications Officer Laura Roberts if you have any questions. In the meantime – happy blogging!


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