Chemical Ghost of 50 million year old invisible teeth!

On Friday last week our research group published another paper in Applied Physics A that reinforces the use and application of our synchrotron-based imaging technique. The technique permits us to tease-out chemical information from fossils…information that you simply cannot see with the naked eye. Such chemical maps can help us see 'ghosts' of original biological structures that only remain in very dilute concentrations in the fossil.

(a) Optical photograph of BHI-045A (main slab) containing preserved, almost complete fossil reptile skin (Squamata (Reptilia). The reptile consists of intricately preserved skin formed of individual scales, but no visibly preserved hard-tissues (i.e., endoskeleton, inset of boxed area in a). SRS-XRF map of copper (b) and sulfur (c) of BHI-045A resolving the biological material including individual scale detail (insets). Scale bar = 1cm.

The fossil specimen we study in this paper was thought to be a 50 million year old skin moult from a lizard….of some unknown variety. Our work was able to map the presence of teeth that could not be seen in visible light. Our x-ray mapping technique showed the presence of phosphorus from teeth and their precise location relative to the rest of the head and body. This is VERY important as now, our fossil skin cannot be a moult….lizards do not moult their teeth when shedding their skin….so we now know something has wiped-out (disolved) the bone, post-mortem, but preserved the skin…along with a whiff of the original skeleton, albeit the teeth. This changes how we view the taphonomy (from the Greek taphos 'burial' and nomos 'laws')…but also allows us to identify the type of lizard for the first time, based upon the geometry of the teeth.

(a) Magnified view of jaw region of lizard (BHI-045A) in phosphorus showing preserved dentition chemistry. (b) Interpretation of arrangement of preserved dentition red interpreted as teeth belonging to one jaw, blue to another; it is difficult to tell which is the upper and lower jaw. Scale bars = 5mm

This means we can now start looking for traces of animals that are totally invisible in visible light, but shine a bright chemical signature under the powerful gaze of the synchrotron. This 'x-ray vision' will enable palaeontologists to add important information on the biology, anatomy and preservation of ancient life.

Our new paper can be downloaded from this link: N.P. Edwards, R.A. Wogelius, U. Bergmann, P. Larson, W.I. Sellers, P.L. Manning. 2012. Mapping Prehistoric Ghosts in the Synchrotron. Applied Physics A, DOI 10.1007/s00339-012-7484-3

Dinosaur of Paradise....

Yesterday I found myself in the hallowed halls of the University of Cambridge Zoology Museum. This is a stunning museum...one that mere photographs would simply fail to do justice. This is a museum that everyone must visit at some point in their life. Laid before you is one of the most diverse displays of endless forms most beautiful that elegantly tells the tale of the evolution of life on Earth.

Occasionally in my line of work you get the opportunity to kneel at the alter of evolution and bow ones head in reverence...yesterday was one such day. The collections manager at the Museum, Matthew Lowe, kindly showed me an object from the Cambridge collection that was both stunningly beautiful, but also historically priceless. Matt carefully lifted a glass top from a beautifully crafted case, containing the preserved remains of some Great Bird of Paradise collected in the latter half of the 19th Century...this should be the first clue as to their import. Those of you who have read my prior posts, will have heard my rants on the amazing adaptations and diversity that we see in modern avian theropods (who most call birds). The Great Bird of Paradise almost certainly possesses the most incredible array of feathers to have evolved from dinosaurian stock. Their striking plumage has long captured the eye and imagination of poets, writers and natural historians...but it is the latter that played a key role in the acquisition of this particular specimen.

As I peered at the lifeless form, that is still breathtakingly beautiful even in death...Matt drew attention to the label. I did a double take and realised this sample had been collected by one of the most iconic and influential naturalists to have lived!

Coll. A. R. Wallace.......Splendid!

Ruffled feathers in Palaeontology...

That well-known 'palaeontological' journal, The Economist, recently entered the less than subtle debate on the preservation of fossil feathers, with a report called 'Feathers Fly'. This article tells a story that is sadly not new to our field. It seems that some science actively courts controversy, especially when palaeontological plumage is at stake. The rare circumstances that give rise to the preservation of feathers is now being explored by several research groups, including my own. We all share more than a passing interest in the pigments and structures that once bestowed colour upon the now dull fossil plumage that occasionally make it into the fossil hall of fame. How we come to unpick, quantify and identify colour is now being hotly debated.

There seem to be three major camps in this debate (at least). Those who map the morphology of both extant and extinct feathers to compare and contrast the presence, absence and shape of the biological paint-pots (melanosomes) that once might have held pigment (remember that an albino would have no pigment, but still have melanosomes). The second group of folks seem to favour chemistry, given it might well be possible to identify the remnant chemistry of pigments, locked in the degraded keratinous tissues of fossil feathers. The third group, looks at both structure and chemistry.

Biological paint-pots or bacterial contamination, that is the question?

There are some potential problems when you have to base your interpretation of colour solely on morphology (group 1), as there is still debate on the origin/affinity of these structures. Some suggest they might be bacterial in origin and have nothing to do with melanosomes, this is something that only chemistry can really resolve/verify. However, extensive statistics borne from the study of feathers fom extant species of birds supports the first groups approach. This first technique does show huge potential and has been widely published in high-impact journals....here comes the 'but'....the technique relies upon using an environmental scanning electron microscope (ESEM) that often limits the size of sample and the total area of sample to be mapped. To map a whole fossil bird, say the early Cretaceous Confuciusornis, using ESEM would take an operator thousands of hours (if it fits in the ESEM chamber in the first place). Not very practical...and quite mind-numbing. Inevitably, this technique leads to the extrapolation of colour, based upon a fraction of the overall surface area of the fossil available. It also often entails the removal of samples from the surface of stunning fossils...something we try to avoid. Try imaging less than 1% of a zebra skin and reconstructing the colour and patterns...you might get stripes, but there would be a strong chance that white or black dominated your reconstruction.

The  eumelanin pigment molecule with its central copper atom.

Group 2 have been using chemistry to aid in their interpretation of possible pigments preserved in fossil feathers. This is a powerful technique, if it is possible to constrain elements/compounds that are linked to, or are breakdown products of original pigments. Some chemical techniques can only map small areas of fossils and are often not sensitive enough to detect the dilute concentrations of trace-metals that might well be associated with pigments. The x-ray analysers (such as EDAX) on many ESEM's only allow a rough guide as to the presence or absence of elements and are often difficult (if not impossible) to map over large areas. The EDAX is also unable to constrain the oxidation state of elements, which is so critical to the elucidation of their organic or inorganic origins.

ESEM and EDS can provide valuable information, but not to the same resolution or
sensitivity of synchrotron based imaging.

Group 3 takes the approach of using both structural information from ESEM analysis and the chemical mapping of whole fossils, using synchrotron-based imaging. This has the advantage of being able to identify structures that look like melanosomes (via ESEM), but then also verify their possible identity through chemistry (via synchrotron-mapping). This might be the best approach that we have to date, as it allows 100% of a fossils surface to be mapped, but there are many more approaches in development that might aid, refine and further unlock the colour palette of fossils. The synchrotron-based approach also provides the unique ability to undertake the spectroscopic analysis of fossils providing key information on the oxidation state of elements...meaning we can gauge if they were organic in origin, or not.

Print me out and download the FREE App 'Chemical Ghosts' from  the iTunes store....and watch me come alive!

It is clear that the different groups are all generating new and exciting data. This is splendid.  As more data gets published, more information becomes available to the wider scientific community.  Hopefully within this growing sink of evidence, more robust hypotheses can be constructed as to the preservation of feathers and the possibility of a whiff of colour.

Stormy skies over New York City

My trip back from Grand Cayman managed to fly me right over hurricane Sandy, leap-frogging the said storm and getting back to the UK safe and sound. I simply could not believe the news the following days as images of the impact of Sandy started to filter through the media. Many of the places I have worked or played from Delaware to the Jersey Shore and up to New York City, all were heavily impacted by this severe storm.

This past week I have been back in the USA, working in Philadelphia (at the University of Pennsylvania) and also in New York City (at the American Museum of Natural History (AMNH)), as these are both close research/field partners for my team and I. Philadelphia seems to have gotten through the wrath of Sandy relatively unscathed, but as I travelled north to New York...it was clear they had faired much worse. It seems that the media had not exaggerated the impact, as some might suggest they have with past storms. Last year I sat through hurricane Irene, when still working in Philadelphia,  and other than very heavy rain, high winds and some local flooding, the storm (thankfully) did not live-up to the media-hype...Sandy however, was different.

Sat on my Amtrak train from 30th Street in Philly to Penn Station (NYC) the effects of the hurricane  become more and more apparent as I traveled north into New Jersey. Entering Newark, I could clearly see vast roofs torn from the tops of skyscrapers, closer to ground many buildings offered a hagard look with doors hanging from their hinges, streets strewn with debris... the tell-tale signs of water damage and high winds. Many who had been without power for a week were now suffering a cold blast courtesy of an unforgiving Norwester. The East coast is more than used to such inclement winter storms, but not immediately following a hurricane. This was another cruel blow to the region.

As I walked toward the familier environs of the AMNH, torn-up tree-roots, felled branches and small drifts of snow made me realize how gentle the UK maritime climate is when compared to the USA. It is a sobering thought that geography plays a crucial role in the climatological hand that we might be dealt. Even the hallowed halls of the AMNH had taken a 'gentle' punch from Sandy. One of the curators had his window blown-in and his office walled 'gently' shunted outward...nothing moved in the office...just the window and the wall. When you see the thick, solid stone walls of the AMNH...it makes you think about the power of such storms. I just hope the meteorological deck has played its worst hand for some time and that the folks of the Eastern Seaboard get a chance to rebuild their homes and lives.

Blown away by Sandy...but the fossils are fine!

Forgive the lack of blogs these past few days, but I am en-route back to Manchester...via a very windy route. You can imagine my joy when I logged into Weather Underground to see this....

...the awfully nice folks at Weather Underground have allowed me to use this image. All I can say, the image is much prettier than the look on my face, when I found that my flight path was taking through the inner bands of Hurricane Sandy. Thankfully, I am now sat in Washington DC, awaiting my flight for Manchester...not feeling too hungry after a rather lumpy flight. I clutched my precious fossils tight to my chest, as I have promised a few colleagues back home some samples from my new locality...hmmmm, methinks I forgot to mention this new locality in my blogs? Oh well, I had better work on the fossils first and then tell you the full story at a later date. Sorry, but that is how it has to be....but patience is something any budding palaeontologist is more than used to.

Grand Cayman Blue Iguana: A success story in conservation

When was the last time that you heard some sad news about an endangered species and a little piece inside of you quietly wept. That helpless feeling that so often fills you with sadness that another species is going the same way of the dinosaurs. Not so the Blue Iguana. Here is a conservation tale that will hopefully leave you with a little warm glow of success inside. This is the tale of a species that stared extinction square in the face and delivered a salty-sneeze at its doom....with the splendid help of the Blue Iguana Recovery Program (Grand Cayman) (BIRP). This priceless band of eco-warriors have turned the tide for a whole species. Meeting such folks is a humbling experience...but I was lucky to find myself in their hallowed halls (well...enclosures) in the last few days.

The Blue Iguana (Cyclura lewisi) is a breathtakingly beautiful blue beastie... one that the awfully nice folks at BIRP have teased back from the brink of extinction. This was a species that was critically endangered, but is now merely endangered (honest... this is a very good thing!). The population teetered on the brink of extinction only a handful of years ago, with a mere 100 or so individuals left on Earth...now their number exceeds 1000. The folks at the BIRP know a thing of two about what makes their precious charges breed. More importantly, they have carefully constructed a program that ensure genetic diversity and strength ...a case of watching/controlling who breeds with who! In the case of this species, if you breed with someone too close to the family, your offspring will be infertile...not good for any species, especially one starring into the abyss of extinction.

These beautiful blue blighters struggle on the reproduction front, when compared to their Green Iguana (Iguana iguana) cousins who produce larger egg clutches at least three times a year, compared to the solitary or few eggs produced by the Blue. It must be said that they do get better at producing eggs when they get older, but...in terms of competition for space and food, the Green's win.

However, the Blue Iguana still has something to smile about. With the committed work of the BIRP, this species has recovered its numbers and is ready to go wild again. This is the most incredible facet of this conservation program...it is so rare that a conservation program is so successful that it has to evolve or become extinct. In this rare, but oh so satisfying, moment in the conservation of this species, the BIRP team is looking to change its spots to become managers of a wild population, as opposed to one that has to bump-up numbers. The story of the Blue Iguana is far from over, as there is this interesting transition from breeding in captivity to management of a species in the wild...I dock my hat to the wonderful folks at BIRP for achieving what so many have tried to do..but who have so miserably failed. Methinks there is a trick or two we should learn from this team of interpreted conservation stars!

Green Iguana or Blue Iguana...that is the question?

Dinosaurs were successful…very, very, very successful. They formed one of the most diverse terrestrial beasties with a backbone to have walked on Earth. There were few ecological niches that they did not thrive in during the Mesozoic era (otherwise known as the ‘Age of Reptiles’. Their ‘piggy-in-the-middle’ position between reptiles (crocodilians, etc.) and birds has made resulted in a great deal of interest in the biology of this group. There has been much debate concerning the metabolism of this group, often resulting in scientists getting a tad hot under the collar!

It is quite clear that “cold-blooded” reptiles and “warm-blooded” mammals are quite different in many ways; both modern groups are likely to differ greatly from their dinosaurian relatives. Lucky for us, the same physical laws apply to all land animals and the physical building blocks (biomaterials) used by dinosaurs are almost certainly relatively conservative in composition when compared to their living relatives. These laws that have built, controlled and honed the bodies of living and extinct animals controls certain distinct characters that dinosaurs might have possessed….this helps us reconstruct these long extinct beasties.

Given half a chance, you will fund many palaeontologists chasing living beasties that form one or the other side of this evolutionary ‘bracket’ that provides the missing pieces of information to help us reconstruct dinosaurs. This week, I have been lucky enough to observe a rather large terrestrial (land-based) reptile…the Iguana….in my own attempts at understanding more about the physiology and behavior of living reptiles. As an aside, it was the teeth of the living Iguana that helped Gideon Mantell come-up with a name for his Lower Cretaceous Iguanodon (literally, ‘Iguana tooth’), based solely upon their similarity in tooth morphology (shape). This was the 2^nd dinosaur to be named in 1825 a year after Buckland had described Megalosaurus. So, you can imagine my excitement for getting to see Iguana in the field!

The Cyaman Brac Iguana (Cyclura nubila caymanensis) you see in these images are all from Cayman Brac Island (not surprising)…as I have yet to see the famous and despicably endangered Blue Iguana (Cyclura lewisi) of Grand Cayman. I hope to see my first Blue Iguana this weekend…damn exciting!

A fun thing to note with the Iguana is the typical reptilian sprawl of their limbs. This has been used by some to suggest that dinosaurs (with their more upright 'mammalian-type' limbs) were very different when it came to metabolism....oops...I must run to give a lecture. I must finish this thought later!

Caves, humidity, bugs and beasties

My arms and legs look like successful taget practice for the bug and mosquito bite-fest that was seemingly taking place in Cayman Brac. My blood is clearly the preferred diet of beasties as my colleagues appear untouched...so much so, I am now considered the best insect repellent to have along in the field. Trying to avoid bugs, we started to explore some of the subterranean lairs of the 'Brac'...with our splendid local guide, TJ. As we climbed the relatively sheer wall of the Brac, it was clear there were dark recesses lurking in some of the karst limestone. This was where we were now headed.

As we climbed higher up the sheer wall of the Brac, we could finally see the ocean again as we topped-out over the canopy that cloaked the base of the cliff. TJ then disappeared ...into a hole in the wall (Alice in Wonderland style!), just large enough to scramble inside on your belly. Looking back over our shoulders  all you could see was the bright light of day, however the direction of travel was rather dimmer...

This was no tourist attraction, but a cave that had only been visited a few times by TJ and very few others. In terms of caving, you rarely get a chance to tread where only a few have trodden...humans that is! All we had to light our way were a few flashlights that our friendly guide had brought along. Every now and then TJ would call back offer say helpful advice, like..'This is a tight squeeze...you might have to breathe in a bit' or 'This is a great entrane, I got stuck here for half an hour last time...till I could free myself!'...I looked at TJ's stature and realised I was approximately twice his body mass and circumference...this was going to be a fun and rather tight subterranean trip!

As we pushed deeper into the limestone caverns, I could see we were travelling back in time though a coral reef system that was once teeming with life. The fossil evidence of corals and shells was all around us. We were literally walking on shells...albeit fossil ones. I have to admit, that crawling on my belly in the pitch-black, in what seemed 100% humidity and 35 Celsius plus...is not usually my idea of fun...but then a cavern or two would open-up and make the trip so worth while....

The caverns and tunnels have been etched away through the action of ground waters over the past few thousands of years, fuelled by slightly acidic rain and the organic rich soils that cap the whole of the Brac...courtesy of all that vegetation. This was one of many sites that TJ kindly extruded our bodies to see though the sharp, karst limestone...but I also promised you some animals of the Brac...this will be my next blog....as it is some of these animals that might hold clues into dinosaur physiology.

Fossilised giant that replays ancient sea-levels

This weekend I visited Cayman Brac, a small island a mere 90 miles northeast of Grand Cayman. One of the largest fossil structures that can exist on a continent is preserved here on these azure shores. This is no giant sauropod or bleached bones of an enormous whale, but the echo of an ancient shoreline. Yes, a beach can become a fossil, if you know where to look!

The island, like the rest of the Cayman Islands, is there due to the same submarine ridge that forms the carbonate backbone of these coral-aproned islands. The first thing that you notice about the 'Brac' (a gaelic word for bluff) is the relatively high and sheer limestone cliffs that hoists the main portion of the island ~100 feet above sea level.

As you stand on the road that follows the southern shore of the island, you cannot help but notice the land-shapes or geomorphology. Facing west along the line of the Brac, you stand on what is clearly an almost level surface that gently dips to the south by a few degrees into the beach area and tidal zone.  Facing north, you are met with an almost sheer cliff of the Brac, that runs from east to west, that meets the platform on which you are stood at a sharp 90 degree angle. The base of the cliffs are hidden by dense vegetation, that you have to scramble through to see a geomorphological feature that has a curious explanation. When you reach the cliff base, you see there is a concave notch, seemingly cut-out from the base of the cliff, that runs the whole length of the Brac...both north and south facing walls.

To understand what this feature represents, you only have to walk towards the present-day shoreline of Cayman Brac and watch the waves pound the limestone shoreline. The constant wave action slowly carves a neet concave ridge, just above the gentle slope of the wave-cut platform that allows the waves to continuously roll in from the Caribbean Sea. The feature that so defines this high wall of the Brac, is simply a function of wave action from an earlier time, when sea-level was higher than present day. Around 120,000 years ago the globe was a tad warmer and was basking in the sun of a interglacial phase...literally 'between ice'. The water that was not locked-up in ice-caps caused a global rise in sea-level of a few metres, raising the ancient wave-action to cut the notch at the base of the Brac....what we see today. The subsequent glacial phase, in which we still live, resulted in a global fall in sea-level...stranding the wave-cut platform and distinctive notch as a vast, fossil beach....even a beach can become a fossil...and you too can find them where ever you are around the world, you just have to know what you are looking for!

My next blog will explore the caves and wildlife of Cayman Brac.

Past forward: Mangroves, reefs and Archaeopteryx?

The present can be a key to the past. This is something that the 18th Century Scottish Geologist James Hutton raised when viewing the surficial processes that have sculpted the land-shapes of the United Kingdom. This idea was refined and liberally applied by the famous 19th Century geologist Charles Lyell whose pivotal book, Principles of Geology, accompanied a young Charles Darwin on his voyage of discovery. This basic assumption that many palaeontologists apply to the fossil record relies on the uniformity of natural and physical laws that have governed our planet in both the past and present. This principle of 'uniformitarianism' often drive my colleagues and I to study the tissues, behavior, environments and ecology of living species, so that we may better understand the same in extinct organisms.

This week, I find myself on Grand Cayman…I just pinched myself…and yes, I am still sat on Grand Cayman. I am here to explore some of the most pristine carbonate environments in this corner of the world, so that I might better understand similar environments that I often sample from the fossil record. The submarine ridge that supports the Cayman Islands defines its geology, topography, as well as the rich environments that support a diverse flora and fauna. The carbonate shelf that fringes the islands support prolific coral reef communities while the lagoons and mangrove swamps inland support a vibrant terrestrial community. It is times like this that I realize how little we have to work with when reconstructing ancient communities, of which a fossil assemblage only represents but a fraction of the extinct ecosystem.

Stingrays at Stingray City (Grand Cayman) Image courtesy of Jim 'Rayman' Gobetz

The geological record of life also has a nasty habit of time-averaging samples, so that a fossil assemblage might represent hundreds or even thousands of years, albeit in a single unit of lithified sediment (rock). At the same time, the subtle variation in species and their distribution through time and space can be blurred due to the cumulative affects of taphonomic processes acting upon and concentrating, filtering and/or refining a fossil assemblage…all this and more adding to the difficulties of unpicking the past for palaeontologists. Hopefully, my wading through lagoons, swimming with stingrays, trekking through mangrove swamps and diving into reef systems will provide me with some new insights on this particular fraction of life on Earth…and not a dinosaur in sight! However, I am VERY keen to see if a seabird manages to meet a sticky end in one of the back-bay hypersaline lagoons…maybe a gentle echo of similar environments and taphonomic processes that preserved its distant Jurassic ancestor Archaeopteryx. I am sure that James Hutton would approve.