Ichthyosaurs: Now available in colour

So, I am aware that it has been a long, long time since I last posted a blog. I am sorry for that. I am writing up my PhD, which takes a lot of time and effort and I am very close to submitting. The small amount of spare time I have, I have spent making the most of my personal life rather than writing blogs. Anyway, with any luck I can remember how to do this so here goes.

This blog posts deals with colour in the fossil record, and particularly with colour in ichthyosaurs. This focuses on the paper published in 2014 by Lindgren et. al. (2014).

Colour is rarely seen in the fossil record as soft parts of the body (such as skin or feathers) are not often preserved. Despite this, in a few rare cases colour can be seen. It has been reported previously, predominantly in insects (Fig. 1) but also in feathers (McNamara et. al., 2012) where exceptional preservation occurs.

Beetle

Fig. 1: Fossilised beetles with colour preserved. From McNamara et. al. (2012).

So how does this relate to ichthyosaurs? Well, exceptionally preserved specimens of ichthyosaurs are known, typically from the Holzmaden area of Germany. Many of these specimens preserve a soft bodied outline which has already contributed to knowledge of ichthyosaurs (Fig. 2). Without these outlines, the dorsal fin and the semi-lunate tail shape would not have been known if only skeletal material was preserved. These outlines have generally thought to have been the result of a bacterial mat that built up during decomposition.

Fig. 2: Ichthyosaur showing soft body outline

Fig. 2: Ichthyosaur showing soft body outline

Lindgren et. al. (2014) analysed these soft body parts of an ichthyosaurs, carbonised scales of mosasaurs and remains of a leatherback turtle using SEM (scanning electron microscope) and ion mass spectrometry. Under SEM, the black material surrounding the skeleton is comprised of micro-meter sized spherical and rod shaped bodies (Fig. 3). These bodies strongly resemble melanosomes that are found in extant lizards and feathers. Melanosomes are an organelle that creates and stores melanin, a natural pigment that creates darker colours in organisms. In humans it is found in hair and more can be creates in sunlight, resulting in a tan. Further micro analysis shows that these features are more associated with the ‘skin’ rather than the surrounding rock.

Ion mass spectrometry  produced negative-ion mass spectra from specific smaple regions of the ichthyosaur. The results closely match the spectrum obtained from natural eumelanin. Eumelanin is a type of melanin that relates to black and dark-brown colours.

Fig. 3: Photograph of the specimen showing part of the tail (Scale 5cm); Ion image showing eumelanin in green (Scale 3µm); Enlarges area showing melanosome like microbodies (Scale 1µm).

Fig. 3: Photograph of the specimen showing part of the tail (Scale 5cm); Ion image showing eumelanin in green (Scale 3µm); Enlarges area showing melanosome like microbodies (Scale 1µm) from Lindgren et. al. (2014).

These results all indicate that the body of an ichthyosaur was a dark grey/black. The areas sampled all showed a similar result which suggests that there is no counter shading with lighter underparts, but were completely dark. Many modern large open ocean organisms are this dark grey/black colour such as whales and dolphins and this result is consistent.

However, it is important to remember that, although the results are sound, the analusis has only been conducted on a single specimen from a single species of ichthyosaur so far. It will be interesting to see if any other colours or colour patterns emerge in future studies.

As always, thanks for reading. Feel free to leave any feedback.

Sam Bennett

Twitter: @Didgeman83

References

Lindgren, J., Sjovall, P., Carney, R. M., Uvdal, P., Gren, J. A., Dyke, G., Schultz, B. P., Shawkey, M. D., Barnes, K. R. & Polcyn, M. J. 2014. Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles. Nature. 0:1-4

McNamara, M. E., Briggs, D. E. G., Orr, P. J., Noh, H. & Cao, H. 2012. Original colour of fossil beetles. Proc. R. Soc. B. 279:1114-1121

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Made in China

I know it has been a while since I last posted a blog but life has been busy, with a fossil festival in Lyme, a thesis to write and a beer festival thrown into the middle. Apologies for the absence but luckily for you, here I am with another installment.

A new specimen of a Triassic ichthyosaur has been discovered in South China. This alone is not huge news as lots of new Triassic specimens are coming out of China. However, this particular specimen is a lot more interesting than that. This is a mostly complete specimen of Phalarodon atavus (Fig. 1).

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Fig. 1: Remains of the ichthyosaur and interpretive drawing from Liu et. al. 2013.

Although useful information can be gathered from the skull alone, this is typically just about the genus and species to which the animal belongs while teeth can provide some information about diet The fact that this specimen is nearly complete provides a lot more information than just cranial elements. The size of the organism can be shown, the paddles are preserved, as are the vertebrae. As a result of all this, information can be gleaned about the swimming style and abilities of the animal.

So, lets talk swimming styles. The typical body shape of an ichthyosaur is what’s known as ‘Thunniform’ body shape. This is the typical semi-lunate (crescent) tail shape and a ‘stiff’ body, such as in Tuna and Sharks and the like. This body shape and swimming style is ideally suited to pursuit predators and sustained swimming. This type of body plan is not thought to have evolved until the late Triassic. It is currently thought that earlier ichthyosaurs would have a more ‘reptilian’ body plan and would swim by moving the whole body side to side like a typical crocodile swimming motion.

However, in the new specimen the centra (vertebrae) are quite long and high, similar to some sharks today. This suggests a ‘rigid’ body as seen in the thunniform ichthyosaurs, potentially allowing this ichthyosaur to have a sustained swimming ability. Furthermore, the teeth of this specimen are relatively well preserved. They are quite small and bluntly pointed with no cutting edges. There are however longitudinal ridges along the crown of the tooth. The blunt points suggest a more ‘crushing’ type feeding strategy but the longitudinal ridges suggest at least some ability to hold onto a prey item. Therefore, it is most likely that this ichthyosaur would favour prey items with a relatively soft outer body, such as belemnites or fish with very few scales and would forage for them. The rigid body, allowing sustained swimming, would suit a wide-ranging forager and seems plausible for this specimen

I am sure you are all overwhelmed and very excited with all the information and stuff that’s been said so far in this blog but get this, there’s more! This particular species of ichthyosaur is only known from Muschelkalk Basin in Germany, and due to an assumed inability for sustained swimming as well as geographic barriers, that it was endemic (limited to one area).

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Fig. 2: Global palaeogeographical reconstruction showing the distribution of Phalarodon atavus from Liu et. al. 2013

The new material from China suggests that this is not the case and the geographical distribution was much larger than previously thought (Fig. 2). Again, this supports the idea of a sustained swimming style, made possible by a rigid body and potentially, a tail beginning to resemble the classic crescent shape. It’s a fun time to be into ichthyosaurs.

As always, thanks for reading. I hope you enjoyed it. Feel free to leave feedback, good or bad.

Cheers,

Sam

Twitter: @didgeman83

References

Liu, J., Motani, R., Jiang, D-Y., Hu, S-X., Aitchison, J. C., Rieppel, O., Benton, M. J., Zhang, Q. Y. & Zhou, C. 2013. The first specimen of the middle Triassic Phalarodon atavus (Ichthyosauria: Mixosauridae) from south China, showing post-cranial anatomy and pero-Tethyan distribution. Palaeontology. pp. 1-18 DOI: 10.1111/pala.12021

Engaging the public

So it has been a little while since I did my last blog post and I thought it was about time I did another one. Instead of looking at another paper I though it would be a good idea to talk about something that I particularly like about being a scientist. That is public engagement, and specifically, two things that I am involved in in the near future.

The first of these is the Lyme Regis Fossil Festival. Firstly, some information. This is taking place on the 3-5th of May, in Lyme Regis, Dorset. The website with all the information is here: http://www.fossilfestival.co.uk

This is a fantastic opportunity for anyone, of any age, the meet and talk to experts in various fields, from palaeontology to mineralogy. Several groups of people, including myself, come from the Natural History Museum in London as well as people from other institutions, the National Trust etc etc. The NHM runs various activities including an ID table where you can ask experts to identify fossils you have found. Furthermore, there are also talks given (including one by myself) by scientists talking about their research. I do not yet know if the schedule is confirmed, but keep checking the website for more information. This is a fantastic opportunity to hear some new research, presented for the general public.

“Well, that all sounds good” I hear you cry “but I am in London and can’t get to Lyme Regis!” Do not fear, this leads me nicely onto the next thing. (It’s almost like I planned that link huh). This is a Nature Live event. These events are hosted by the NHM, at the NHM by an amazing team. These events are completely free to anyone and everyone and last for 30 minutes. This is similar to a chat show where a researcher from the Museum (any department) is there to talk about their research and answer any and all questions from the audience. (Yes, I am doing one of these on ichthyosaurs). More information about Nature Live events can be found at this web address here: http://www.nhm.ac.uk/nature-online/nature-live/

So why do I think this is important? These events, and any events such as these provide an opportunity for make science accessible to the general public, in such a way that anyone can understand whether you’re 4, 14 or 40 years old. I think this is a very important thing to do. New and amazing discoveries and insights are being made in every field of science and I think that it is great shame if these discoveries remain available in expensive journals that are inaccessible for most people as well as being written in scientific language that can be difficult to understand. It is therefore, in my opinion, something that all scientists should try and do.

Feel free to let me know what you think about these events and public engagment in general. If you’re a scientist and think it’s good or bad, let me know. Same, if you would attend an event like this, let me know.

Hope you guys don’t mind the lack of science stuff in this post, i’ll do something else in the near future (next month, after the fossil festival).

Hope you’ve enjoyed reading. Follow me on Twitter if you want @didgeman83

Big, bad beast in the bigger picture

Welcome to my latest blog post. This one is going to have a look at a new big and bad ichthyosaur as well as what this actually means in a bigger picture. The paper I am looking at is by Fröbish et. al. and was published this year.

The authors of the paper describe a new ichthyosaur from the early Middle Triassic (244 million years old) which they have named Thalattoarchon saurophagis. The specimen they examined comprises most of the skull and axial skeleton, parts of the pelvic girdle (hips) and  parts of the hind limbs. The ichthyosaur is very large, estimated to be larger than 8.6 metres long. This is about the same size of a modern killer whale which is awesome.

However, the size is not the coolest thing about this specimen. By far the best aspect (to my mind) of this specimen is the teeth. The teeth are labiolingually flattened with two cutting edges and are slightly recurved. This just means that they are flatted and sharp, similar to those of a shark, but without a serrated cutting edge (Fig. 1). Furthermore, the largest tooth measures a minimum of 12cm tall from root to tip with a crown of 5cm.

ImageFig. 1 from Fröbish et. al., 2013 showing the teeth. Scale bar measures 1cm.

The flattened teeth is an unusal feature of ichthyosaurs. The vast majority of ichthyosaurs have conical teeth, ideally adapted to piercing and holding onto small prey items such as fish or belemnites (an ancient squid-like beastie). The flattened teeth suggest a different prey type. The teeth are designed for cutting through flesh and indicate that this ichthyosaur was capable of attacking and eating prey of a similar size to its self. Ichthyosaurs with conical teeth would likely swallow their prey whole as unlike this one, they would have been unable to cut and bite through flesh.

So despite being very cool, is it such a big deal that this ichthyosaur is big and capable of eating large prey? Well, there’s more to this story than that. A short time (in geological time anyway) before this specimen was alive, one of the biggest extinction events in Earth’s history had just taken place, the Permian – Triassic extinction, where an estimated 96% of ALL LIFE in the sea died. Crazy huh! It takes time for life to recover, and in terms of trophic groups (levels in a food chain, eg producer, grazer, predator, scavenger etc) this starts from the bottom up where producers and grazers would recover first with predators recovering from an event like this last. The ichthyosaur in this paper would sit at the highest trophic level as top predator. The presence of this specimen means that the oceans had recovered from this huge extinction event. This indicates a rapid evolution and recovery in the seas. The seas recovered within 8Ma of the extinction event and only 4Ma after reptiles first invaded the seas. This is a faster recovery than previously expected. Up until this point, the modern trophic network in the seas had not been properly established with large predatory tetrapods at the top of the food chain.

So there you go. New specimens and new species are always very interesting and usually pretty damn cool but it is also important to think of the bigger picture and the implications that a specimen may have.

As ever, thanks for reading. Until next time fossil fans!

References:

Fröbish, N. B., Fröbish, J., Sander, M., Schmitz, L. & Rieppel, O. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. PNAS. 110(4):1393-1397

Eye eye, what’s going on here?

So here is the third installment of my blog. As I am still new to this kind of thing, I am sticking with familiar territory. For me, this is ichthyosaurs (not surprising). For this blog we are going to look at their eyes, and one paper, Motani and co’s interpretation as to the reasons behind why they are so big.

Ichthyosaurs are marine reptiles from the Mesozoic, around 259 million – 90 million years ago. They are exceptional among Mesozoic marine reptiles as they evolved a fish-shaped body (they look similar to dolphins, except with an upright tail fin like sharks). They also had exceptionally large eyes for their size (Fig. 1) and are completely awesome. But what is the purpose of such large eyes?

ImageFig. 1 – Pic by Sam Bennett. Red line showing the eye socket in a specimen of Stenopterygius from the Statliches Museum fur Naturkunde. Stuttgart, Germany

Motani et. al. (1999) say that the absolute size of an eye is important. This is because the bigger the eye, the more photoreceptor cells they can hold, and therefore the more light the eyes can receive. Also, in an evolutionary context, the size of an eye in an organism can reflect on how important the use of eyesight is. Some animals that live in caves in perpetual darkness have lost the use of their eyes. In such cases the eyes are either tiny, or non-existent. We can infer then that the eyes were big in ichthyosaurs as they are important.

The authors compared eye size to body length for ichthyosaurs (using the sclerotic ring, a circle of plates in the eye) to infer eye size in ichthyosaurs (Fig. 2).

ImageFig. 2. Graph showing eye size to body length for ichthyosaurs and other organisms (Motani et. al., 1999).

The graph illustrates how much larger the eyes are  compared to other organisms. The authors go on to use f-numbers compared to eye opening size. This is the same measure that is used for cameras. The results of this show that the ichthyosaur with the lowest f-value would have been capable of seeing in low light conditions, up to 500m depth. A conservative estimate would give it a similar visual range as a cat. It is inferred that light point sources could be spotted at depth. This means that an ichthyosaur could spot bio-luminescence from prey.

From the general ichthyosaur body plan, we can safely infer that they were mainly pursuit predators, similar to dolphins and some fish today. The results of this paper show that they were capable of hunting prey at depth and would dive to get a meal. This conclusion is further supported by evidence of the bends seen in the humerus and femur (upper arm and thigh bones) of the organism. This provides a valuable insight into the feeding strategies of these large reptiles.

As ever, if you’ve got here, thanks for reading. I hope you enjoyed it. Tune in next time for whatever takes my fancy.

References

Motani, R., Rothschild B. M. & Wahl, W. J. 1999. Large eyeballs in diving ichthyosaurs. Nature. 402:747-750

The curious case of imploding ichthyosaurs

Fossils are rarely found in the exact position that they are deposited, with all the bones in the correct positions. Processes that affect the fossils, such as water currents, scavenging etc are known as taphonomic processes. For weird remains, the taphonomic processes have to be understood in order to explain how a fossil came to be in the position that it is seen in the rock. In this post, I am looking at a new theory that may explain some unusual ichthyosaur remains.

The remains in question are unusual in the fact that they consist of a well articulated, well preserved adult specimen that was pregnant when it died. The odd part is that the remains of the embryos (ichthyosaurs gave birth to live young) are scattered and some are preserved outside of the parent (Fig. 1). What could cause this type of positioning of the bones??

ImageFig. 1: Scattered embryonic bones lying outside of the mother from van Loon, 2013

Previous theories have suggested that ocean bottom currents could have relocated the lighter bones. However, this would result in the smaller lighter bones of the parent also being moved (such as smaller vertebrae towards to tip of the tail, or small phalanges (finger bones) located at the tips of the paddles). This is not always the case.

Another suggested theory was carcass explosion caused by sudden release of gases built up in the body as a result of decomposition. A recent paper by Reisdorf et. al. (2012) showed that (a) ichthyosaurs would likely sink on death, and (b) it would be impossible for a carcass explosion to happen in deeper water (which is a shame, because explosions are cool). This is because of high water pressures surrounding the remains. However, Reisdorf did not suggest a mechanism that could explain the features of the fossil in Fig. 1.

A paper this year by van Loon (2013) offers an alternative explanation, implosion! van Loon agrees with Reisdorf and co. that the corpse would sink and that decomposition would begin. However, van Loon goes on the say that at some point, when gases have built up, the outer wall of the ichthyosaur would break. (This could either be through scavenging or natural decomposition). When this happens it would result in an in-rushing of water due to high pressures outside the body compared to inside. This in-rushing of water would be turbulent enough to move some of the small embryonic bones and deposit them near the parent. It is suggested that this small movement of water would not affect the remains of the parent, resulting in the fossil seen above.

There are many other remains of ichthyosaurs where this process has not happened and embryos are still contained within the abdomen of the parent or appear as though they are giving birth (Fig. 2).

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Fig. 2: Ichthyosaur ‘giving birth’. Photo by Sam Bennett from the Staatliches Museum fur Naturkunde Stuttgart, Germany.

It is likely that the ichthyosaur in Fig. 2 did not die whilst giving birth but that the embryo was pushed along the natural path by decomposition gases. However, from the two specimens shown in this post, it is clear that not all specimens underwent the same taphonomic processes after death. There are many different scenarios that can make life of a palaeontologist harder, but also more interesting!

If you’ve reached this part, thank you for reading it all, or maybe just quickly scrolling to the bottom. Either way, you deserve a cup of tea/coffee and biscuit! Enjoy.

References:

van Loon, A. J. 2013. Ichthyosaur embryos outside the mother body: not due to carcass explosion but to carcass implosion. Palaeobiodiversity and Palaeoenvironments. 93:103-109

Reisdorf, A. G., Bux, R., Wyler, D., Benecke, M., Klug, C., Maisch, M. W., Fornaro, P. & Wetzel, A. 2012. Float, explode or sink: postmortem fate of lung-breathing marine vertebrates. Palaeobiodiversity and Palaeoenvironments. 92:67-81

Introduction

As a researcher, I am often asked to ‘write a brief introduction about myself’. This can be for a website, a conference, a poster or whatever. This is something that I do not enjoy doing. However, I have just started this blog and it is forcing me into writing something straight away. Therefore, here is an intro about me and my blog (Wish me luck).

Lets start with the facts. My name is Sam Bennett and I am PhD researcher at Royal Holloway, University of London and the Natural History Museum in London. My research is on ichthyosaurs, an extinct group of marine reptiles alive during the Mesozoic when the dinosaurs were doing their thing on land. I am researching their ontogeny (physical changes with age) and sexual dimorphism (physical differences between males and females). I am in my 3rd year and can usually be found writing my thesis, or drinking coffee/beer while worrying about writing my thesis. The basics, check!

OK, now that is out the way, lets follow the what with the why! Why am I doing this blog? Admittedly, it is partly procrastination. However, the main reason is to help fulfill my desire to share palaeontology based science with a wider audience. I feel that it is a shame if advances in science stay within the scientific community, or are portrayed in a way that makes it difficult to comprehend etc. Therefore, this blog is my attempt to share my interests and passion to anyone that is interested enough to read all of this. I hope to talk about my own research as well as the research of others and whatever else tickles my fancy.

If you’ve read this far, thanks. Please keep and eye out for an actual post about fossils and what not, coming to an internet near you.

Me at my desk. I am smiling because I have coffee

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