So what are doing with your time exactly Mr Hauser?

Hello Luke here, here it is then my first post on fish related to my research, sorry it’s so late folks but it’s been quite hectic. But before I introduce the cast of characters I will just mention what my PhD is on. I am looking at the Downton bone bed from the welsh borders; some of you may be wondering “Downton bone bed? Well I have heard or the very famous Ludlow bone bed”. This is kind of the point of my research, when you look at the Ludlow bone (fig.1) you can see this grey lithology and all those black grains…their fossils and in particular fish fragments. This is also true of the Downton bone bed however if you were to see it you would not clearly see the fossils, this is because all the fossil grains are of a similar colour to the lithology (a tan/brown colour) and this is why it has been missed for full investigation for the last 150+ years. So the next few sections for you delectation are some brief summaries of the types of fossil fish that I will come across, of course one the most exciting aspects of my PhD is the potential of finding new things, now this does not necessarily mean new species but possibly fish that are not known from this part of the world or at this time or who knows what. So without further ado here are the cast of characters I will become familiar with over the next possible 6 years and hopefully you guys will learn to love them, these odd bunch of early fish.

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Figure 1 Ludlow Bone Bed

Condonts

So these little jawless beauties appear in the Cambrian and make it all the way to the end Triassic! That is very impressive when you consider a lot of these fish don’t make it past the P/T mass extinction let alone animals getting past the Devonian. While on the subject of “animals” let’s clear things up about condonts and conodont animals, now condonts have been know about since 1856 when Christian Pander a Latvian embryologist and palaeontologist first identified them but, they were not the whole animal. They are calcium phosphate (or to be all fancy like calcium carbonate fluroapatite) microfossils known as conodont elements (fig.2)

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Figure 2. Conodont elements: (a, b) coniform elements, (c, d) ramiform elements, (e, f) pectiniform blade elements, (g, h) pectiniform platform elements, (i) bedding-plane assemblage.

which would have been found in the mouth of the animal (fig.3) Now these elements can be categorised by shape into different types protoconodonts, paraconodonts and euconodonts and due to taxa like Ozarkodina whose apparatus has been found complete and articulated we know how they looked in the living animal (fig.4).

So what about the living animals well the conodont animal or as some

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Figure 3. (A) Dorsal view of the reconstructed, closed apparatus of Novispathodus.(B) Orientation of the apparatus within the conodont’s head.

researchers are suggesting they should be called Conodontophora (conodont bearers), either works for me. These were eel like fish (fig.5) ranging from a less than a centimetre to those gigantic Ordovician monsters of the Soom shale which were 10’s of centimetres. Now it is at this point I should explain some of the many controversies with conodonts, so first off; what are these chaps (and chapettes) eating, well the main idea is that these were filter feeders using that complex apparatus in the mouth to filter out plankton from the water column. However in more recent years researchers have found that the elements have microwear patterns and this tells us that these guys are grasping prey so they are more likely swift little hunters.

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Figure 4 (a) natural assemblage of conodonts from the Carboniferous of Illinois (×24); and (b) the conodont animal from the Carboniferous Granton Shrimp Bed, Edinburgh, Scotland, with the head at lefthand end (×1.5).

Other blog posts in the works for these critters are; Conodonts: are they vertebrates? (yes and here’s why) and were conodonts venomous?

Thelodonts

Ah thelodonts or to translate their name ‘nipple tooth’, these jawless fish (agnatha) ranging from a few centimetres to meter in length and make up the bulk of the bone bed fauna so far seen. Now I apologise if I wax lyrical about these guys but in terms of my project I have come across hundreds of these guys but like 4 conodont elements so you can understand if these get a tad more press but worry not fans of conodonts they will get their own post.

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Figure 5. Reconstructions of Conodontophorans in life

So let’s get into them, they appear in the Middle or Late Ordovician and sadly bit farewell and join the choir invisible in the Late Devonian. We find their fossils can be found all over the world and we can find them as complete articulated specimens but the majority of their fossils (and certainly this is the case with my material) they are found as isolated micro fossils (fig. 6). I should at this point explain what thelodonts are; they are fish with an endoskeleton of cartilage and then there skin is covered in dermal denticles (fig.7) in a slightly analogous way with sharks. The denticles, as the dent part of the word suggests are related to teeth…that is for want of a better word they are teeth in the skin (hence the dermal bit). In the fossil record they usually “rock” (no pun intended) up as isolated denticles in sediment most famously in the Late Silurian bone beds but occasionally as entire articulated specimens found in places like Canada, Scotland and Scandinavia with all their denticles in place. While on the subject of places we find their remains add to the list Russia, Australia, South East Asia, Europe and finally North and South America. They are a monophyletic group although one group the Furcacaudiformes from Canada are morphologically very different and there is debate on their position in thelodonti and represent a new order of thelodonts (Märss, 2006a).

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Figure 6. thelodont fish in life

Overall thelodont affinities remain somewhat unclear, it has been suggested that they are the sister taxa to the osteostracans and could also be close to chondrichthyes but the way thelodonts have their micromeric squamations (scales) is different from both. Ultimately when it comes to where these fish fit one must remember there we are talking about a group of animals mostly known from there isolated dermal denticles in fact in most decent phylogenetic analyses only contains24 to 25 taxa because that’s how many we have articulated. Now that’s not to say that that makes it invalid I am unsure how many characters were generated but 24 taxa is quite a small selection but does once again highlight the challenges one faces when dealing with the fossil record.

On a final foot note for now diet wise these chaps are probably eating plankton, algae and rubbish (well deposit and suspension feeding on sediment) in fact the Furcacaudiformes with their deep bodies and large eyes were suggested to be predators. Right well not top of the line predators but still taking on small prey items however it is more likely the large eyes were used to help select only the tastiest bits of detritus….also helps in spotting predators, like giant sea scorpions.

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Figure 7. thelodont denticles Loganellia scotia

Acanthodians

The final group of fish that I will be looking at and discussing here are the “spiny sharks” or acanthodians (fig. 8) named in 1844 by Agassiz (for more information about Agassiz’s life and work click here). This group gets its name from the Greek word akanthos which means spine and it’s well placed as they are the only fish that processed spines on all their fins. They appeared in the Silurian which is handy for me and disappeared when coprolite hit the fan with end Permian extinction. However one of the most notably features of the acanthodians are jaws…yes these are some of the first jawed vertebrates but at the time of my research (roughly 420 ma) they are not the dominant fish fauna it’s still the agnathans. There found in the fossil record like thelodonts both as, in my case isolated fragments of denticles or as articulated specimens and they are found in all corners of the globe. In terms of there relationships with other early fish we rule out early sharks (although the spiny sharks  name came from morphological similarities) placoderms and early actinopterygians, but of the jawless ancestors only thelodonts come close to a similar micromeric squamation but it is unlikely the two are that closely related. It now seems that they share a lot of specialized characters with osteichthyans compared to other groups, some of the characters are: similar shaped brain case, nature of the gill filaments (hemibranchs) along the gill arch and the presence of brachiostegal rays. Although (Davis et al 2012), found that they are somewhat split between the osteichthyans and the chondrichthyans, so once again this shows that with dealing with fish this far back getting a complete resolution of their origins can be difficult.

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Figure 8. Example of an acanthodian Climatius reticulatus, Illustrator Arthur Weasley

There are three subgroups of acanthodians the first is the Climatiiformies which were I guess the “standard” acanthodian although were more heavily armoured than the other two. The next it is the Ishnacanthiformes which had robust jaws and big teeth and assumed to be the predators of the group and finally the Acanthodiformes which were the most successful of the groups and despite developing jaws became filter feeders (turns out have jaws is not just handy for grabbing food items). The final bit of classification is the scale morphology there being two types, one is the Acathodes type which is a crown made of true dentine and a thick acellular bone base and Nostolepis type that has a dentine crown penetrated by vascular canals and a base of cellular bone.

Others

Now there have also been chondrichthyan scales found in bone beds of this age in the welsh borders but apart from saying “there are sharky things in them there hills” I can’t expand really, I also may come across material from other types of agnathans and as soon as the thesis or paper is accepted I will be blogging about it, I also plan to do more in depth posts on these groups but all in good time.

So yes there we are that’s the sort of fish I will be working on hopefully Chris will tell you about his fish soon so until next time (which will be a special post) take care.

References

Davis, S. P.; Finarelli, J. A.; Coates, M. I. 2012. “Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes”. Nature 486 (7402): 247.

Janvier. P, 1996. Early Vertebrates, Clarendon press. Oxford. Pp.393

Long. J.A, 2010. The rise of fishes: 500 million years of evolution, Johns Hopkins University Press. pp.304

Märss, T. Turner, S. & Karatajūtė-Talimaa, V. 2007. Handbook of paleoichthyology Volume 1B “Agnatha” II Thelodonti, pp.141.

Märss, T., 2006a. Exoskeleton ultrasculpture of the early agnathans and fishes. – Journal of vertebrate paleontology. 26(2), p.235-252.

All taken from Google images apart from figure 4 taken from http://www.blackwellpublishing.com/paleobiology/figure.asp?chap=16&fig=Fig16-5&img=c16f005.

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The SVPCA 2012 spectacular!

Yes yet again apologies for the delay from the last blog post but we have been busy bee…fish? Anyway yes Chris is preparing to start his PhD and I have been rushing around and for the last two weeks so here is the belated SVPCA blog post oh and for those wondering what does SVPCA mean (symposium of vertebrate palaeontology and comparative anatomy).

Ok so let us start with a very brief overview of the week, the conference this year was held in the beautiful city of Oxford one of the Holy Grail’s of early British palaeontology. The venue was the fantastic Oxford University Natural History Museum which in terms of a venue for this sort of thing is just the tops. So it was a weeklong lecture series and how this works is thus day one: fish, days two and three: reptiles and days four and five: mammals (terms and conditions may vary please ask in store for full details). So course for this blog please understand it’s just fish talks and posters discussed here, however there were loads of talks I would love to discuss, sadly I cannot though do check out the links at the bottom of this post for other blogs discussing other talks. The other side of SVPCA is the social this is not purely a bunch of academics getting ratted….honest; no it’s more of a networking session, a chance for fellow workers to meet and or catch up. I alone have some exciting projects in the pipe line thanks to these casual chats over free coffee and wine (incidentally my love for wine increases directly in relation to its price….so at SVPCA I LOVED the wine). So that is the extra bits of SVPCA done, now on to the meat and potatoes of the event.

So the way I’m going to tackle these talks and posters is somewhat alphabetically according to the author however may not be in the order I heard them etc. So first up was a talk entitled:

An overview of the hybodont record of the Cameros Basin (northwest of Iberian Range, Spain), Dr. David Didier Bermúdez-Rochas presented this thought provoking talk on the diversity of hybodont (fig.1)

Figure 1 Hybodont reconstruction

sharks in the Cameros basin of Spain which to be honest according to the talk was rubbish but that could be due to the continental sediments. The basin’s previous taxa were referred to Asteracanthus ornatissimus, Hybodus polybrion and Hybodus sp. so yeah not the vast assemblage you might expect. However surface prospecting in a new locality showed a much larger assemblage Lonchidion (which is represented by the highest number of elements), Lissodus, Parvodus, Hybodus, Planohybodus and Egertonodus, that’s more like it and these provide a window into a freshwater community of hybodonts being the dominant freshwater sharks (and we thought we had problems with just bull sharks). This new data provides evidence that the faunas of northwest Spain now have similarities with other regions of Spain as well as the classic Wealden localities of Britain. It was suggested by colleagues that this flush of new taxa may be due misidentification in not accounting for the change in teeth within parts of the mouth. Now certainly this is true of in the jaw reconstruction of sharks like Carcharocles megalodon as workers did not account for the dental pattern, however this is not a fair argument for this talk as that is more to do with size than morphology so I am confident with the identification of these sharks.

3D textural analysis of microwear and trophic ecology of placodermsfirst of all congrats to Mr Laurent Darras whose talk this was who has just passed his viva with minor corrections so now he is Dr. Laurent Darras. Now to the talk given not by Laurent but by his supervisor Dr. Mark Purnell, the talk discussed the work Darras has done on morphospace on fossil aquatic gnathostomes (jawed vertebrates). The idea of morphospace analysis is that by simply plotting points on a jaw or a whole fossil you can create shapes these shapes can be plotted and basically you get pretty graphs which can suggest what ecology these animals have. The problem he points out is that sometimes what the morphospace suggests is not always what the animal actually feeds on so you need independent evidence to either to confirm the morphospace data or not. In the discussion the placoderms, that’s fish like Dunckleosteus(fig.2)

Figure 2 Dunkleosteus

were used as a model to test if microwear analysis could be used to test the idea of microwear being a good bit of independent analysis. The other questions this could answer like ecomorphology, ontogenetic shift in diet and predation driven macroevolution events. He has been able to prove that microwear analysis can be used to test and constrain specific hypotheses of the diet and trophic diversity in all kinds of fish. I remember at progressive palaeontology he discussed this with Pycnodont fish…..via the medium of lord of the rings….you had to be there!

Evolution of bone repair via invasive growth of dentine in a 380 million year old fish, this talk was present by Dr. Zerina Johanson who in my very short career I have already had the pleasure of working with, So this talk centres around a specimen of Psammolepis (fig.3)

Figure 3 Psammolepis

a Heterostracan (one of the many groups of jawless fish I will talk about in the next post). Now this specimen is interesting because of the damage on the dorsal surface of the fish not necessarily because of the predator-prey interactions, but as the title suggests from the point of view of the repaired damage. The skeleton of these jawless fish are dominated by dermal done in a form known as aspidin which is a precursor to bone as we would know it, on the surface however there are many dentine tubules (fig.4). The deep injury to the Psammolepis is cool because it shows evidence of healing this in itself is not surprising (an animal healing injury ruddy Nora!) no what is interesting is that the fish has used dentine to heal the wound, literally flooding it. The bone (aspidin) appears to have not been involved at all like the fat kid never picked for sports. The dentine is produced and laid down in a chaotic manner by ondontoblasts which are found in the tubercle pulp cavities as well as in the surrounding flask shaped crypts in the bone. Ok now at this point I could talk about the idea in the talk about stem cells and pore canal systems etc, but what I personally found amazing is that sand grains managed to get included in the healed wound this inclusion is not so shocking as you can see from the image of Psammolepis it’s flatted body is indicative of a modern flat fish and I can easily imagine these chaps partially buried in the sediment of the seafloor and this is how the sand ended up in the wound and being covered in dentine.

Figure 4 The simplifed structure of Psammolepis demal plate

Beating the bends: The spare ribs of Big Meg now this talk was given by the ever so entertaining Dr. Jeff Liston, and concerned the large amount of bones belonging to the giant Jurassic pachycormid Leedsichthys (fig.5) (and yes you guessed it were going to do a post on these guys too). Now without getting to bogged down these are BIG fish some estimates go up to 53 feet (Liston, 2005) and being fish they have a truck load (literality!) but a lot are broken and fragmented and ultimately what you end up with is a load of ‘rib-shaped bones’…not that helpful. So what Jeff has tried to do is to reverse engineer the bones so that we can see where they may been on the body as the idea being that a bone reflects the stresses and pressures that is was under during life so if you normalise the bone you can have a better idea where is goes. So here is the maths: normalised bone curvature = X/2L x 100…….ok got that good simply what he found is that this by using some Argentinean specimens where we know the accurate position of the bones and there curvature, he could plot the Leedsichthys elements into three size clusters which showed that many came from the anterior. A slight curve ball here is the fact, and I was unaware of this is that the older the pachycormid in age (which sometimes meant the larger they were) the less the skeleton is ossified which makes sense when you think about the sheer size of these leviathans (in weight saving etc).

Figure 5 Leedsichthys & Liopleurodon

New specimens of Symmoriidae sharks from the Carboniferous limestone of the Derbyshire Peak District the shark themed talk was presented by the lovely Kelly Richards who is a PhD student at Cambridge University and was an introduction of her project, what she has done and what she hopes to do. We learn that fossils are full of ‘bucket taxa’, synonymies, inadequate diagnostic descriptions etc and this is very true in the Palaeozoic shark family Symmoriidae. Within the talk new material from two horizons in Derbyshire were mentioned one Stethacanthus altonensis(fig. 6)

Figure 6 Stethacanthus

which until this point has only been known from Bear gulch in Montana and is represented by quite substantial material which will help clear things up and Akmonistion zangerli(fig.7) known previously from Bearsden deposits Scotland. Again this taxon is represented by substantial material which should help build a better picture of the palaeobiology and paleogeography of the Symmoriidae. Over all being a fellow PhD I always enjoy these talks, that is ones explaining the aims of the projects and being able to see the projected direction of the PhD so kudos to Kelly there.

Figure 7 Akmonistion

Lazarus Shark taxa in the Triassic of Australia Dr. Sue Turner came with another shark talk (because sharks are cool!) and this as the name suggests is on a ‘Lazarus taxa’, now some of you reading this may be wondering what Lazarus taxa means well Lazarus was a brother in the Bible who came back to life (no not a zombie!) and this case it’s when a taxa disappears from the fossil record only to reappear later on either in the fossil record or in the modern day. The coelacanth is a prime example of a Lazarus taxa, but back to the matter at hand, xenacanthiform sharks what about them, well Sue told us how new material have been found and this with material already known and described in 1908 by Arthur Smith Woodward. The talk raised an interesting point that the fossil record of xenacanths (fig.8)

Figure 8 Xenacanthus

is well known in the Lower Carboniferous of Queensland but none are known from the later  Palaeozoic expect for these new and old specimens from the Triassic. So how did these sharks get through the Permo-Triassic extinction and was Australia a refuge for the sharks, hopefully further investigation of this new material will in time answer these questions

Phew well there we are….oh wait hold on forgot the posters so without further of do:

New chondrichthyan-like scales from the Lower Silurian of Mongolia it was nice to see this poster by Plamen Andreev, being a fellow Silurian micro vertebrate worker, the take home message I got from this poster is that a new chondrichthyan has been found this however is based on scales rather than a complete fossil animal. I was intrigued by the use of micro-CT and it’s something I would be tempted to possibly try this on my own scale material in the future.

New details about the Ordovician jawless fish Sacabambaspis janvieri Marco Castiello who I have chatted to many times before SVPCA (check out his blog here) was there with his beautiful poster featuring artwork from the very talented Stefano Broccoli. There poster was very exciting as the work concerned the agnathan (jawless) fish Sacabambaspis(fig.9)

Figure 9 fossi of Sacabambaspis

one of the first well preserved vertebrates whose remains have been found across the world. It always amazes me that even something like this well known fish…..honestly it’s well known, is not exactly what we thought and the study carried out suggests the oral paltes are composed by some small platelets that are similar to lepidotrichia as well a number of other features.

Evolution and development of a morphological innovation: The pufferfish beak (Tetraodontiformes; Teleostei)this poster by Gareth Fraser was frankly a brilliant piece of work and as the title suggests looked at the beaks of pufferfish (fig.10)

Figure 10 Pufferfish

using normarsky optics, micro-CT and optical projection tomography to show that although the pufferfish beak looks like an innovative structure it’s not made from a new genetic blueprint, oh no it’s just evolution tinkering with the general osteichthyan dentition, truly the beauty sometimes is in the detail.

So that’s about it folks for this post, oh I did have a poster there but I don’t like sounding my own trumpet but I think it went down well…ish. Hope you enjoyed this review hopefully soon I will post up my PhD fish related goodness until then stay safe and say no to drugs.

 

Blogs with SVPCA posts

Mesozoic monsters

Ichthyosaurs: a day in the life…..

gimpasauria

Paleostories

References

Liston, JJ (2005). Homologies amongst the fragments: searching for synapomorphies in shattered skulls. In: Poyato-Ariza FJ (ed) Fourth International Meeting on Mesozoic Fishes – Systematics, Homology and Nomenclature, Extended Abstracts. Servicio de Publicaciones de la Universidad Autónoma de Madrid/UAM Ediciones, Madrid, pp 141–145.

All images from Google images