Tag Archives: Mesozoic

Home Again – Dispatches from Montana 3 (The Photo Edition)

Missed the previous Dispatches from Montana? see them here and here.

Well I’m back in jolly ol’ England and as promised here’s the photographic edition of the Dispatches from Montana. I’ll try to explain all the photographs as and where they need it.

click for big!

First off here’s the field crew as a group, Liz was the crew chief (the dig boss if you will) with Cary as second in command, Denver was the only other member of MOR staff with us. Danny, Will, Nick, Tom, Dana and Bobby were all undergraduates of various universities and Cracker is the Redding family’s dog.

Click for big!

On my first night in Montana we had a fabulous thunderstorm which provided ample opportunities to get frustrated by human/camera reaction times, the above and below pictures being the best results I could get that night!

Click for Big

Before the storm hit however I was just able to snap this shot of the Redding Field Station’s camp, you can just make out the storm-clouds to the left (south-west) and our flimsy patch of tents to the left of the quansit hut (the grey WWII hangar style building). The practically-bomb-proof ranch house is out of shot on the right.

Click for Big!

The next photograph was taken from behind the afore-mentioned quansit hut, and shows a small section of Kennedy Coulee, the river valley to the north of the Redding Field Station, where all the dinosaurs can be found…Click for Big!

Here’s another panorama showing a small finger of Kennedy Coulee, including the “Rocky” dig site in which I was to spend the last three weeks digging. To give some idea of the scale of the operation, this site has been excavated for only the last 3 years, and at the start of that time, the left of this photograph would have looked pretty much just like the right hand side…

Click for Big!And here’s a view from inside the quarry itself, to give some more perspective on it and also to show you how much of the overburden mentioned in “The Adventure Begins” we had to remove… at the start of the field season, ground level was at the level of the white-grey sandstone layer!

Click for Big!

This photograph zooms in on the area that I and two of my compatriots were working (on the right of the previous picture). I myself was working the middle section with the chisel, brush and oyster-knife. It is a surprisingly slow process because you never know when you will hit another fragment of bone (as Nick, working to my left, was finding out. every piece of tin-foil represents another bone uncovered).

Click for Big!Another panoramic photograph for you now, this one again showing Kennedy Coulee, but also some lovely Virga – that is to say rain that evaporates before it touches the ground – to the north of the site.

Click for BigHere’s another photo of Cracker – affectionately known as the Cracker-the-quarry-dog, enjoying the sun and generally getting in the way!

Click for BigSo moving on to more palaeontological topics, here’s a field jacket… It’s what you do to the finds before they get transported to a museum or prep-lab. The first step is to cover all the bones in a consolidant (Vinac in this case) then a layer of wet tissue (to act as a buffer and a barrier to the next layer. Finally a mixture of plaster of paris is concocted and infused into burlap (hessian for us UK people) sacking. This was the first field jacket of this year’s season to be excavated.

Click for Big!A couple of days after the jacket was made it was dry and ready to flip (in order to remove excess rock and jacket the bottom). Here’s a photo of Dana with the flipped jacket. You can also see where it stood before it was flipped!

Click for Big!The strata in which the bone-bed is found is a mudstone approximately a metre thick, capped by a shelly sandstone layer containing bivalves up to 20cm across and many varieties of gastropod. This cap-rock can be seen below:

Click for Big!

Here’s another panoramic shot, this one taken at lunch time (hence all the sleeping dino-nerds) from above the working face of the quarry on the penultimate day of my short stay at the Redding Field Station.

Click for Big!And finally… The night before I was due to fly out of Great Falls we had a rather close call with a thunderstorm that passed within a couple of miles of camp – all we had was a slight drizzle – but I had the chance to take this gorgeous photograph at about midnight…

Click for Big!

I hope you enjoyed the post.

Ben D. Brooks

28.06.2012

Advertisements

A rare summer find in Lyme Regis

About two weeks ago, after the Lyme Regis Museum‘s fossil walk on the 27th August, there was an interesting find on the Church Cliffs landslip east of Lyme Regis.

Paddy Howe, fossil walk leader and the museum’s resident geologist was walking back from the end of the walk with myself and Chris Andrew (the museum’s education officer) when he spotted something in the shales of the landslip…

Line of ribs visible in the shale

Rib cross sections visible in the shales of the church cliff landslip.

…There were only three small (approximately 5mm in diameter) cross sections of ichthyosaur rib bone that could be seen in the shale layer he had spotted. When some of the shale was removed however there could be seen a small number of holes in the shale where other ribs had been. This immediately caught Paddy’s attention as it meant that there could be a significant portion of an animal fossilised in this spot, but with the tide rapidly approaching it was necessary to return the next day, so the find was carefully covered to prevent further erosion and we burned the location in our minds, determined to return on the Sunday.

Paddy Howe Digging out the Ichthyosaur

Paddy Howe digging out the Shale Slab.

Had the fossil survived the night? Had another fossil collector discovered and excavated it? or worst of all, had it been destroyed by the tide?

After some not inconsiderable trepidation during the Sunday mornings fossil walk, we three returned to excavate the slab containing the ribs that had been spotted the day before. To my amazement – and I am sure; Paddy’s relief – the slab had survived relatively undamaged and so the excavations began.

The first task was to remove as much of the surrounding material as was possible, and this was done through the liberal use of a hammer, chisel and shovel… and took about 30 minutes to complete. This done, a more careful investigation of the slab could be made, which raised far more questions than answers because at first inspection there appeared to be no further bones in the rock! Had we wasted our time digging around this slab when all we would find were a few rib fragments?

Thankfully not, more bones were eventually seen, after some mud and shale was washed off of the newly exposed surfaces, so now the task was to remove the block – preferably  in one piece – for preparation and exposure of the whole fossil.

Ichthyosaur Slabs on the Stretcher

Slabs of rock collected together on Paddy's stretcher. (this is only half of them!)

Disaster – or near disaster at any rate – struck a few minutes later when the slab split, not once, but many times, leaving us with a large number of small blocks and a jumble of loose bones at the bottom of the hole. This was a mixed blessing in that it made the fossil easier to get onto the stretcher (the only method of transporting the remains) but as the hole was rapidly filling with water and all of the bones of the skull (the lower-most bones in the slab) had been disarticulated. Sifting them from the mud may have resulted in some being lost lost in the pool of muddy water. Sadly we will never know.

The final task now facing us was to get the remains of the slab off of the beach, which was to take an inordinately long time thanks to both the weight of the slabs, and the ungainly and distinctly uncomfortable nature of the ex-army stretcher we were using. This process took approximately an hour and a half, and yet we only travelled about half a mile along the coast back to Lyme Regis. Including some impromptu outreach along the way to interested tourists!

Paddy and the Fossil talking to Tourists

Paddy undertaking some impromptu outreach with holiday-makers and the Ichthyosaur fossil.

The slabs have now been passed to a local fossil preparator, who will work hard for a couple of months to release the fossil from it’s muddy tomb and carefully piece the jigsaw back together. Unfortunately we won’t be able to identify the animal to a species level until this work is completed, and even then only if all the diagnostic features are available… only time will tell if that’s possible.

Ben Brooks

07/09/2011

Short-Link for this post: http://wp.me/pFUij-dh

Convergent Mososaur/Ichthyosaur evolution. – [Retrospective Post]

Mososaur

reproduction of a painting of a mososaur but Charles R. Knight (1897) | via wikimedia commons.

A research team from Sweden, Canada and the US have recently published a paper in the PLoS one journal which looks set to redefine the way vertebrate palaeontologists look at a whole group of mesosoic marine reptiles. Unlike the recent reclassification and demotion of the Torosaurus genus there has been little reaction to this online.

The paper; entitled “Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur” describes the exceptional preservation of a mososaur specimen of the species Platecarpus tympaniticus, including significant soft-body preservation. The researchers then go on to discuss the convergent evolution that this mososaur species exhibits with other marine vertebrates.

The largest single paradigm shift in the paper is the observation that the fossil’s tail vertebrae fall into four distinct sections and that the tail bends downward approximately three fifths of the way down the tail (posterior to the animal’s rear paddles). This downward bend in the vertebral column is something that is shared with other marine reptiles including the Ichthyosaurs and Metriorhynchidae. Modern sharks show a similar – but upward – bend in their cartillaginous skeletons.

Shark Skeleton

Shark Skeleton Diagram illustrating the up-bend in the vertebral column, Re-drawn from Gottfried, Compagno, and Bowman 1996 (via /www.elasmo-research.org/)

This “kink” in the tail of the animals is indicative of the existence of a caudal fin (or tailfin), like those seen in modern fish such as sharks. Mososaurs had until recently been considered to be very crocodilian in their body plan; so much so that historically the tails had routinely been straightened by overzealous palaeontologists; incidentally you can still buy a model Ichthyosaur skeleton from National Geographic which amongst other inaccuracies displays a straightened tail.

One other mososaur skeleton is known to have exhibited a caudal fin, that being the  mososaur described by Lindgren et al. in 2007 as Plotosaurus which existed later in mososaur evolution and was highly specialised. Platecarpus however is a much older animal (preceding Plotosaurus by 20 million years) and helps to demonstrate the evolutionary path taken by this taxon that led to more fish-like descendents such as Plotosaurus. The interesting part of all this has already been pointed out by Brian Switek over at the Guardian Science Blog that this is another example of marine reptiles adopting the downward tail-bend in preference to any other… which begs the question why? what caused this evolutionary preference?

Platecarpus Skeleton image from scientific paper.

Illustration of Platecarpus tympaniticus, including downward "kink" in the tail vertebrae. Image from figure 8 of Lindgren J, Caldwell MW, Konishi T, Chiappe LM (2010), PLoS ONE 5(8): e11998. doi:10.1371/journal.pone.0011998

Another notable conclusion of the research is that there is not only convergence in the evolution of marine reptiles and cetaceans (whales) but also in the rate of evolution, with all four major animal groups (Ichthyosauria, Metriorhynchidae, Mososauridae and Cetaceans) attaining a streamlined, piscine (fish-like) shape within the first ten million years of divergence from land antecedents.

This Story Features in PalaeoNews : Webisode 3 (18th Aug – 05th Sept)

Sources and Related Articles:

Of beginnings and biases

So it’s the summer holidays for me – or at least it is for another week, then it’s back to Southampton University for my last year as an undergraduate student. As part of the summer break I have been doing some (though not nearly enough) work on my Masters of Science project which I explained not very well in my post “My Msci Research Project – Macroecological changes in offshore shelf seas” and now seems as good a time as any to review what I’ve done; and to do so publically in the name of open access science!

Essentially the upshot of the work I have been doing has been to look at the project as described in the previous post and thinking about the methodology and the approach that I will use in undertaking the research. The result of this? I now have a two page list of biases for which I will have to find solutions, adjustments or reasons to discount them and options as to my methodology.

Geological time-scale represented in spiral form

Geological time-scale, the past being at the base of the spiral, image from USGS

Scope

The scope of the project – if taken to it’s pedantic conclusion – is epic, and far beyond either my research experience and the time-frame in which I am able to undertake it. Taking a census of every publically owned fossil from every one of the deposits that I could study would be not only prohibitively expensive due to air fares etc, but very, very time consuming. The solution? to do what other researchers have done when studying palaeoenvironment, take the smallest reasonable stratigraphic unit, in some cases this will be at the level of the formation (such as the Blue Lias) and for others the member (such as the Oxford Clay, where the Peterborough Member is promising), this will also hopefully give a more accurate set of size structure profiles for the study as it will be closer to taking a snap-shot of the palaeo-ecosystem at any one time.

Resolution

The second and last problem for which I have a definitive solution at present is how best to get a suitable resolution for the project, there were two approaches to this and both had their merits:

The pragmatic approach is to look only at the most complete fossil records within palaeontology’s current appraisal of the fossil record.

The idealistic approach is to take the 200 million year scope of the project and split it into “sensible” intervals, and take a sampling at each… say… 40 million year step.

Now if the fossil record was perfect (or even near representative) the decision would be a no brainer, the idealistic approach would be best, and the most scientifically defensible. The idealistic option is certainly what you would do if you were undertaking a study whose study period started tomorrow as it gives the best temporal resolution (or view of changes over time). The record is demonstrably inappropriate for the task, as anyone who is familiar with the palaeontological importance of lagerstätten to the field will understand – most animal carcasses never preserve, and most fossil sites are heinously misrepresentative of the original ecosystem. So in this instance it is more sensible to forego temporal resolution in favour of the best fossil records, with the hope that it will produce a more accurate result in terms of the ecosystem. The risk being that there may be large gaps which make the study less useful in studying changes over time.

Now to move on to some of the problems for which I have no solution as yet…

Scaling of partial specimens

How does one go about using a fossil for a body size metric if you only have a skull? Well in practice when it comes to skulls it is quite simple as most animals have a complete fossil somewhere and the scaling is simple as a proportion of body length – so long as you find the right paper! What about Ichthyosaur paddles, fish ribs or other less simple fossil body parts?

One option is obvious… ignore partials… but by heaven that is the worst solution and would discredit the study before anyone got beyond the abstract! So what else can I do? some people have said that if you know the number of a vertebrae (i.e.: where it comes from along the vertebral column) you can work out a vague size… is that good enough? What about anything other than skulls and vertebrae; can I ignore them?

Prominent British geologist and palaeontologis...

William Buckland | Image via Wikipedia

Collection Biases

Many of the deposits I’ll be studying have the same problem, their fossil collections were mostly excavated in victorian times, when science was done by country gentlemen or rich folks who wanted the biggest, most interesting vertebrates or even other fossils.

Chris Andrew (Lyme Regis fossil expert) related to me a story about William Buckland‘s coprolites (fossilised excrement). When they were surveyed approximately 1 in 20 had Ichthyosaur remains in them. The survey suggested that this is the proportion in reality within the blue lias, yet any of the miriad fossil hunters on the coast can tell you that this isn’t even close to true, finding many coprolites and maybe being lucky to have one a year with such remains within them. The cause of the disparity? The collector had only purchased coprolites that they thought interesting… ambiguous ones with nothing “interesting” were not bought, so biasing the result.

Similarly institutions are going to be more willing to buy specimens that show something different to what they already have in their collections, because if they bought everything they would run out of space! Should I consider all museum collections biased? How does one adjust one’s research outcomes to counter this? Should I even try?

Preservation Biases

On a very similar (but non-human) level and as already stated, not all animal carcases preserve. Some types of animal preserve better than others (e.g.: Ichthyosaurs compared to fish), how can this be tackled?

Actually there is a lot of research on this, it has it’s own field within palaeontology – “Taphonomy” –  but I haven’t researched it yet, and even then the aforementioned Chris provided me with another option which I may describe elsewhere if I use it, or even if I don’t.

In closing, this just gives you an idea of the miriad of problems anyone would face when they are trying to come up with a piece of research, and by golly I can understand why researchers spend so very long on research applications, justifying every decision you have to make is a real eye-opener. Long gone are the days of GCSE science classes when I could say I thought it was the best option because the teacher had advised it!

Ben Brooks

My Thanks to Dr Tim Ewin (Natural History Museum), Mr Paddy Howe (Lyme Regis Museum) and Mr Chris Andrew (The Fossil Workshop, Lyme Regis) for being willing to discuss my project with me and helping me identify the many problems that I now know of, though I’m sure there are more to come!

Short-Link for this post: http://wp.me/pFUij-7R

Hip Hip Huzzah for Science Education…

…well for Biology at any rate.

It has been announced by the powers that be (they being the current Labour Government under the cyclops… Gordon Brown) that from september 2011 it will be a legal requirement for all state-owned primary schools to teach the basics of Darwinian Evolution.

This is,  needless to say; a fantastic advance for science education in the UK, and I must admit to having trouble remembering what if any science I studied at my C of E primary schools… but I still hold some reservations about this great announcement.

Firstly, why are private/public schools exempt from this? Surely science, being the search for fact and mechanisms within the universe, should be taught to everyone at primary and lower secondary, and those who want to study it beyond?  More to the point, why should private/publics be allowed to add a non-scientific bias to their teaching and instill stupification (Religious “schools” I am looking at you) in those most likely to lead our nation in the future?

Secondly, what controls are going to be placed on the curriculum at the state schools? and how are Ofstead going to guard against the “teach the controversy” imbiciles that plague the modern world?

But I shall not dwell on these worrying questions, but shall move on to another great “Huzzah” moment for biology, indeed for medicine – Stem Cell Research is at long last starting to be sanctioned, and hopefully the trend towards pro-science governance will continue long into the future… I dare say if it reverses I will be emigrating as soon as I can!

Also a little bit of Palaeo for the rock-hounds out there that do read this blog, either here on wordpress, or on Facebook or Windoze Live Space… Friday’s copy of The Times ran an article about Paul Sereno’s work on Mesozoic African Crocodilians after his team published some post-expedition papers.

Their expedition found a total of four new species from present day Niger and Morocco, the crocs were found in strata ~100Ma (The Albian Stage of the Early Cretaceous) and include forms varied and wonderful, from “Pancake Croc” (Laganosuchus thaumastos) that was supposedly an ambush piscivore (fish eater), lying open mouthed for hours or days until an unsupecting fish swam into it’s jaws, to “Boar Croc” (Kaprosuchus saharicus); a 20 foot long obligate carnivore whose comparative anatomy suggests it could literally bowl over its prey before dispatching it with its one metre long jaws.

Here’s the link to the Times article: http://www.timesonline.co.uk/tol/news/science/biology_evolution/article6923503.ece

and an old, but related National Geographic article: http://ngm.nationalgeographic.com/2008/09/supercroc/sereno-text/1