Fossilisation of organic material was long thought to result in the complete loss of original content. However in the last 20 years, several high-profile publications reported the discovery of proteins, blood vessels, blood cells and even DNA. But for as long as these arguments have existed, so too has a counterargument as to the validity of the discoveries.
In this episode, we’re joined by Dr Evan Saitta of the Field Museum of Natural History, Chicago, lead author of a recent paper seeking to discover and evaluate the preservation of putative original organic materials within dinosaur bones.
Organic content from the demineralisation of Centrosaurus bone. Such structures as these have previously been interpreted as organically-preserved blood vessels.
To determine the validity of these claims, Dr Saitta led a study to collect and analyse ‘fresh’ samples of dinosaur bone.
Ridge on which Centrosaurus samples were collected. Looking East at mouth of Jackson Coulee, Dinosaur Provincial Park, Alberta, Canada.
Here many specimens of Centrosaurus have been discovered, with bone fragments commonly found littering the surface.
Having removed the overlying sediments, samples were taken of freshly-exposed bone and surrounding sediments.
A Centrosaurus tibia (lower leg) analysed in this study.
Whilst it would be impossible to collect the fossils in a sterile manner, aseptic techniques were used to minimise modern contaminants.
The samples of dinosaur bone were ‘demineralised’ in acids, leaving behind just the organic tissues, and their chemical composition was compared to that of a similarly-demineralised sub-fossil shark tooth and recent chicken bone. Whilst the organic structures seen in the dinosaur bones (D & E) superficially resemble blood vessels, their chemical composition (H – K) was different: the shark (B,F,L) and chicken (C,G,M) organics possessed more Carbon, Oxygen, Nitrogen and Sulphur. This suggests that the dinosaur ‘vessels’ are relatively inorganic in composition and were chemically consistent with a mineralised biofilm.
The organics originating from within the dinosaur bones were also stained with propidium iodide, a chemical which makes DNA glow red under UV flourescence. Interestingly, the concentration of DNA was 50x higher in the dinosaur bone than in the surrounding sediments. The source of the DNA was however modern.
A comparison of the microbial communities of freshly-exhumed Centrosaurus bone and adjacent sediments (mudstone) with two analyses per sample.
16S rRNA gene amplicon sequencing revealed the predominance of Actinobacteria and Pro- teobacteria in subterranean Centrosaurus bone. Nitriliruptoria and Deltaproteobacteria were more abundant than in adjacent sediments or even the surface scrapings from the bone itself. This is evidence that bone, even in pristine conditions must be considered an ‘open system’, and even cultures its own unique microbial community.
Whilst these results cast serious doubt over previous claims of the preservation of original organic content in dinosaur bones, it is good news for microbiologists who can now learn more about this exciting new microbial habitat.
One of palaeontology‘s great themes of questioning is the rise of novelty: how new structures and functions arise in specific lineages. In this episode we speak with Neil Shubin, Professor of Organismal Biology at the University of Chicago, who has been studying novelty in the context of the vertebrate transition from water to land.
Neil studies the fossil record of early tetrapods, the first vertebrates with limbs, to understand what changes underpinned this great transition. The other half his lab uses molecular techniques on living organisms to see how changes to the development of appendages (and their underlying genetic architecture) effected the shift from a fin to a limb.
In this interview, we hear about his fieldwork in the Arctic and Antarctic, how palaeontologists decide where to look for key fossils, why development matters, and about his deep involvement in science communication.
Much of Neil’s fieldwork has seen him working at polar latitudes. His most recent fieldwork was in Antarctica. Pictured is Aztec mountain showing exposures of wind-weathered, fossiliferous Devonian rock above the snow layer.
He has also worked on the Triassic of Greenland. Here, Neil’s team sits above a 1000-meter drop to the East Greenland Sea , the lunch break vistas accompanied by narwhals and polar bears on the ice below.
Neil’s most famous find, Tiktaalik roseae, was in the Devonian rocks of Ellesmere Island, Nunavut, Canada.
Incidentally, here you can find Palaeocast’s report on fieldwork in Arctic Canada.
The Tiktaalik quarry where Neil, Ted Daeschler and Farish Jenkins first discovered and described the original Tiktaalik specimen.
Top Left: Extraction of the holotype of Tiktaalik roseae; Top Right: Skull of the specimen in situ; Bottom Left: The extracted specimen in its plaster jacket; Bottom Right: The prepared specimen.
Scientific reconstruction of Tiktaalik roseae.
Reconstruction of Tiktaalik roseae. Artwork by Flick Ford using colors and patterns of modern predatory fish living in shallow freshwater ecosystems.
Phylogenetic analysis of early tetrapods puts Tiktaalik between the finned, fish like Eusthenopteron– which has no recognizable neck, for example, and Acanthostega, which has four recognizable limbs complete with individual digits.
Details of the transition from fin-to-limb . The fins of most ray-finned fish, e.g. a zebrafish, have large amounts of fin webbing and many bones at the base. Lungfish are lobe-finned fishes and have just one bone at their base. Eusthenopteron has bones that compare to our upper arm and forearm and began to fill in the gaps between fin and limb. Acanthostega shares the same pattern of bones as Eusthenopteron but with the addition of fully-formed digits.
The forelimb of Tiktaalik, showing a recognizable humerus, radius and ulna- all homologous with bones in tetrapods like dinosaurs or mammals.
A reconstruction of Tiktaalik with inset of front limb bones in life position.
The overall picture is that Tiktaalik sits between ‘fish’ and tetrapod.
Alligator gar feeding animation - YouTube
UChicago grad student Justin Lemberg’s reconstruction of suction feeding and biting in gars- created by combining video recordings of live animals with specially contrast enhanced CT scans. The feeding mechanics of the gar are suggested as a good analogy for those of Tiktaalik.
Prof. Neil Shubin and a cast of the Tiktaalik holotype at its discovery site on Ellesmere Island, Nunavut, Canada.
From 1:1 scale whales to microfossils scaled up to the size of a house, there are few model-building projects that 10 Tons are afraid to take on. At the helm of this business is Esben Horn and in this episode, he joins us to discuss the process of model building, from concept to museum display.
We also talk about some of the exhibitions 10 Tons have led themselves, including the successful ‘Rock Fossils on Tour‘ exhibition which showcases some of the different fossils named in honour of rock/metal musicians.
Huayangosaurus was a genus of stegosaurian dinosaurs from the Middle Jurassic. It lived during the Bathonian to Callovian stages, around 165 million years ago, some 20 million years before its famous relative Stegosaurus appeared in North America.
Fossils were found in the province of Huayang in China, and Huayangosaurus were one of the smallest stegosaurians, and measured only 4,5 metres from head to tail.
Huayangosaurus was a quadrupedal herbivore with a small skull and a spiked tail. Like Stegosaurus, Huayangosaurus bore the distinctive double row of plates rising vertically along its arched back. However resembling Stegosaurus, the plates of Huayangosaurus were more spike-like, as well as its skull being broader.
Two plates in the back were formed into large spikes above its hips. These may have been used for deterring an attack from above, considering as it was fairly short in height compared to later stegosaurians.
Sketches for the model were produced by world-renowned palaeoartist John Sibbick.
The body was then sculpted.
Fine details were produced in clay.
The model was then moulded in silicone.
A more permanent cast could then be produced and finished.
The final reconstruction.
Detailing of the skin and eye.
Model made for NaturBornholm and Natural History Museum in Oslo, Norway.
Megalosaurus was a genus of large carnivorous theropod dinosaurs of the Middle Jurassic period (Bathonian stage, 166 million years ago). The first fossils were found in 1676 in Oxfordshire in what is now Southern England. The first naturalists who investigated Megalosaurus mistook it for a gigantic lizard of twenty metres length – hence its name meaning “Great Lizard”. They portrayed it as what can resemble the now living comodo dragons; large dinosaurs walking heavily on all four legs. It was later discovered that Megalosaurus was about 7 metres long and weighing about 1.1 tonnes. It was bipedal, walking on stout hindlimbs, its horizontal torso balanced by a horizontal tail. Its forelimbs were short, though very robust. Megalosaurus had a rather large head, equipped with long curved teeth. It was generally a robust and heavily muscled animal. It most likely had proto-feathers. Megalosaurus was the first genus of non-avian dinosaur to be validly named in 1824. It was perhaps also the first dinosaur, apart from modern birds, to be described in the scientific literature, with a published illustration of a femur bone in 1676 by Robert Plot. At the time, Robert Plot correctly identified the bone as a femur, but incorrectly described it as a Roman war elephant, as the bone was too large to belong to any living species known to be found in England at the time.
The sketches were again created by John Sibbick.
The head was sculpted and cast from a flexible polyurethane that hairs could be punched into.
Detail of the handmade eye.
Each individual tooth was handmade and set in the jaw.
To make the proto-feathers, Yak hair was used. 10 Tons ordered a very loose and open fur and painted between the hairs. Fossil feather and colouration expert Jakob Vinther advised on the process.
Made for Lapworth Museum of Geology, Birmingham.
Individual elements of the Marella appendages.
These were painstakingly added to the model one by one.
Rock Fossils on tour
Rock Fossils - YouTube
‘Rock Fossils On Tour’ is a travelling exhibition of fossils named after rock, punk and heavy metal singers.
When the exhibition opened for the first time at Geomuseum Faxe in 2013, it attracted a surprisingly large amount of attention in the media all over the world, despite the fact that it only consisted of two reconstructions and a couple of posters. Since then, it has grown and it now consists of several reconstructions touring in customised Marshall stack look-a-like flight cases with wheels and aluminium corners, which are easily transformed into exhibition display cases.
First stop on the tour was the Museum of Natural History in Oslo. Since then, the exhibition has visited Natural History Museum Bern, Fossilienmuseum Dotternhausen, NaturBornholm, Natural History Museum Chemnitz, Geomuseum Faxe, Geocenter Møn and Natural History Museum Luxembourg.
Reconstruction of the Jurassic brittle star (ophiuroid) Melusinaster arcusinimicus made for the Rock Fossils on Tour gig at Natural History Museum, Luxembourg summer 2018. Etymology. Species name corresponding to the Latin translation of Arch Enemy, Swedish death metal band, for producing some of the heaviest melodic death metal songs such as “We will rise” and “Reason to believe”.
As if this wasn’t metal enough, 10 Tons made this ‘metal version’ of M. alissawhitegluzae, which was presented as a gift to the lead singer of Arch Enemy after whom the species was named.
ARCH ENEMY - Reason To Believe (OFFICIAL VIDEO) - YouTube
Opsins are the photosensitive proteins in the eye, responsible for converting a photons of light into an electro-chemical signals. Different opsins react to different wavelengths of light, each corresponding to a different band of colour. In humans, the ‘visible spectrum’ of light (a very anthropocentric term) is covered by three opsins, receptive to red, green and blue wavelengths. Other animals have opsins that are capable of subdividing the ‘visible spectrum’ and responding to a large number of very specific wavelengths of interest. All in all, the ability to detect light and recognise colour is not the same throughout the animal kingdom.
In this episode, we are joined by Dr James Fleming of Keio University, Japan to discuss the evolution of opsins in the ecdysozoa (the group containing arthropods and a fair few worms). We talk about the fundamentals of light detection and how, using phylogenetics, we are able to tell which colours certain extinct animals were capable of detecting.
The ecdysozoa are a Superphylum of animals that contains the arthropods, onycophorans (pictured), tardigrades, loriciferans and nematode worms to name a few. All ecdysozoans grow by moulting: a process called ecdysis. Vision is incredibly important to many ecdysozoans and whilst their eyes may be viewed as ‘primative’ compared to those of us vertebrates, they can be remarkably well-adapted to incredibly specific tasks. The compound eyes of mantis shrimp (pictured) are fantastically complex and capable of performing a whole range of visual tasks.
Compound eyes are fixed and immobile, so we are able to reconstruct the visual performance of extinct animals using the same simple optical principles that govern the study of modern compound eyes. We have excellent knowledge of the visual ecologies of animals such as trilobites. Image courtesy and copyright of Peter Cameron. All rights reserved.
We know that vision has been incredibly important to the Ecdysozoa throughout their entire geological history. This anomalocaridid eye from the Early Cambrian Emu Bay Shale has incredibly high resolution, featuring a huge number of tiny lenses (see inset), each of which responsible for monitoring a unique area of space around the eye. Image courtesy of Dr John Paterson.
Unfortunately, from the physical eye we can only interpret such visual factors as its resolution and light gathering capabilities. Information such as which colours it was capable of seeing are held only in the opsins, which are lost in the fossilisation process. Compound eye of the Antarctic krill Euphausia superba (Photo by Gerd Alberti and Uwe Kils) (CC BY-SA 3.0).
Through study of the different types of opsins in modern ecdysozoans, along with an understanding of the relationships between its subgroups, it is possible to make predictions as to which groups had which opsins. From the tree above it is possible to assume that the diplopod and chilopods had the opsins represented by the light blue, green and purple circles, although it isn’t possible to say about the black, pink or dark blue circles. Other opsins may have been independently gained or lost. This kind of inference is called phylogenetic bracketing.
The previous tree only shows the modern animals, whereas there were a whole range of historically important, but now extinct, animals that fall between the modern groups. The stem group arthropods for instance (including the charismatic anomolocaridids) would fall between the onychophorans and the chelicerates on the previous tree, so show could we infer which opsins they had?
To do this, the first step is to see how closely all the modern opsins are related. Then, based on the amount of genetic difference between them, you can estimate how long ago each opsin diverged, on the assumption that differences are acquired at a steady rate. This is termed a genetic clock. In this tree, you can see the different opsins and how they are related. Each branch of the tree is given an estimated divergence date; the bigger the difference between two opsins, the longer ago they diverged.
Through a combination of all the trees and data, you can then make estimates as to the likely opsin groups present in these extinct stem arthropods (left tree). Furthermore, the timing of the origin of different opsins can be placed in geological context (right tree). Here you can see the estimated origin time of the full complement of arthropod opsins (519 -540 million years ago) occurred immediately before the onset of the Cambrian explosion (541 million years ago).
Such evidence lends weight to the theory that the Cambrian Explosion was, in part, caused by the evolution of highly visual predators that sparked an evolutionary arms race.
Decapods are a group of crustaceans that include such well-known families as crabs, lobsters and shrimp. Whilst crustaceans are known from as early as the Cambrian, we don’t see the first decapods until Devonian. Over the course of their evolutionary history, decapods have remained relatively conservative in their morphology with the exception of some interesting forms in the Mesozoic.
In this episode, Dr Carrie Schweitzer, Kent State University, gives us a run-down of the taxonomy and evolutionary history of the decapods and we explore the Middle Triassic Luoping Biota.
Morphological terminology of crabs and lobsters. Cheliped = appendage with a claw; pereiopods = walking legs. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2016. Species of Decapoda (Crustacea) in the fossil record: patterns, problems, and progress, p. 278-300. In W. D. Allmon and M. M. Yacobucci, Species and Speciation in the Fossil Record. University of Chicago Press, Chicago.
Composite reconstruction of the Late Devonian lobster Palaeopalaemon newberryi. Reconstruction by Evin Maguire and Jessica Tashman. Originally published in: Jones, W. T., R. M. Feldmann, J. T. Hannibal, C. E. Schweitzer, M. C. Garland, E. P. Maguire, and J. N. Tashman. 2018. Morphology and paleoecology of the oldest lobster-like decapod, Palaeopalaemon newberryi Whitfield, 1880 (Decapoda: Malacostraca). Journal of Crustacean Biology, 2013: 1-13. Doi:10.1093/jcbiol/ruy022.
Excellent preservation in a concretion of Maeandricampus starri from the Oligocene Lincoln Creek Formation, Washington, USA. Originally published in Feldmann, R. M., C. E. Schweitzer, and J. L. Goedert. 2018. A new species of Carcinidae (Portunoidea) and preservation with a complex taphonomic and depositional history, Washington State, USA. Journal of Crustacean Biology, 38: 579-586.
Arrow indicating tiny, poorly exposed crab, which are very difficult to see in rocks. Late Jurassic Casimcea Formation, Piatra, Romania. Photo by R. Feldmann. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2016. Species of Decapoda (Crustacea) in the fossil record: patterns, problems, and progress, p. 278-300. In W. D. Allmon and M. M. Yacobucci, Species and Speciation in the Fossil Record. University of Chicago Press, Chicago.
Specimen of Jurassic shrimp, Blaculla nikoides, from Bayerische Staatssammlung für Paläontologie und Geologie. Arrow a indicates poorly preserved pleonal somite and Arrow c indicates multisegmented cheliped (leg with a claw). Note that preservation of the carapace (body) is generally poor.
Faunal turnover in the major groups of clawed decapods, the Clawed Lobsters, podotreme crabs (more primitive), and heterotreme crabs (more derived. Anomura include hermit crabs and relatives and thoracotremata include the most derived crabs. Originally published in Schweitzer, C. E., and R. M. Feldmann. 2015. Faunal turnover and niche stability in marine Decapoda in the Phanerozoic. Journal of Crustacean Biology, 35: 633-649.
Upper levels of Quarry 3 Luoping Formation, middle Triassic, Yunnan Province, China. Mapping grid to left of Carrie Schweitzer. Photo by R. Feldmann.
Mapping bedding plane at Quarry 1 of Luoping Formation, middle Triassic, Yunnan Province, China. Huang Jinyuan, Rod Feldmann (standing), and Carrie Schweitzer. Photo by S. Hu.
0.5 m x 0.5 m grid on bedding plane of Quarry 1, Luoping Formation, middle Triassic, Yunnan Province, China. Wen Wen, Huang Jinyuan, and Carrie Schweitzer, pointing at shrimp. Photo by R. Feldmann.
Slab from the Luoping Formation, middle Triassic, Yunnan Province, China with numerous oriented specimens of Tridactylastacus sinenis, suggesting bottom currents. Letters indicate well-preserved specimens, and orientation of specimens measured against arbitrarily designated arrow. Originally published in: Schweitzer, C. E., R. M. Feldmann, H. Karasawa, N. A. Wells, S. Hu, Q. Zhang, J. Huang, W. Wen, C. Zhou, and T. Xie. 2016. Morphology, systematics, and paleoecology of Tridactylastacus (Crustacea, Decapoda, Glypheidea, Litogastridae). Journal of Paleontology, doi: 10.1017/jpa.2016.116.
Field work in southern Patagonia, Argentina, in the Miocene 25 de Mayo Formation, March 2017. Evin Maguire, Silvio Casadío, and Carrie Schweitzer. Photo by. R. Feldmann.
The interaction between plants and atmosphere forms the basis of the carbon cycle and is amongst the most important processes for maintaining life on the planet today. Photosynthesis removes carbon dioxide from the atmosphere and in return forms the base of the food chain and produces the oxygen we, as animals, need to breathe. Equally, the composition of the atmosphere influences the climate and thus the availability of resources, governing where plants are able to survive.
The relationship between the two can be committed to the fossil record by such physical proxies as the number of stomata in leaves and by the palaeolatitude of different species. Other chemical proxies, such as isotopic ratios, can also help elucidate what the atmosphere was like at the time a plant was preserved. Similarly, atmospheric proxies can also be used to make inferences about past plant life in the absence of fossil remains.
Joining us to discuss the link between plants and atmosphere is Prof. Jennifer McElwain of Trinity College Dublin*, Ireland.
Plant growth chamber facilities are used to conduct plant experiments in simulated paleoatmospheric and paleoclimatic conditions.
A reconstruction of East Greenland, Astartekloft in the early Jurassic showing fern dominated vegetation following the Triassic-Jurassic extinction event. Image: Marlene Hill Donnelly.
A leaf fossil of Lepidopteris ottonis, a seed fern from the Late Triassic that goes extinct at the Triassic-Jurassic boundary
Confocal image of epidermal peel from Osnunda regalis (royal fern) showing red chloroplasts in the kidney shaped guard cells and jigsaw shaped epidermal cells. Changes in the density of stomata are used to reconstruct paleo-CO2 concentrations through earth history.
Fossil stomatal complex imaged with epifluorescence . Leaf sample is Toarcian (Lower Jurassic) in age from Borneholm Denmark.
*Correction: Dave mistakenly says University College Dublin in the audio which was Prof. McElwain’s previous institution until fairly recently.
The Carboniferous was a time of huge swampy forests, big trees, and lots of life both on land and in the ocean. One world-renowned fossil site from approximately 300 million years ago is the Joggins Fossil Cliffs, located on the Bay of Fundy in Nova Scotia Canada. Joggins is one of Canada’s five palaeontology-based UNESCO World Heritage Sites, and is one of the best places in this world to find fossils from this time period.
Why are the Joggins Fossil Cliffs so important? What makes this locality unique?
In this episode, Liz speaks with Dr. Melissa Grey, the curator at the Joggins Fossil Centre to learn more about why this region is so important. We discuss the variety of fossils, from plants to invertebrates to vertebrates, and how the interesting preservation has resulted in virtually an entire ecosystem being preserved.
Lower Cove at Joggins Fossil Cliffs. Image copyright Joggins Fossil Institute.
Cliff section of the Lower Cove. Image Copyright Joggins Fossil Institute.
Curator Dr. Melissa Grey looking at a lycopod tree root (Stigmaria) in situ in the cliff. Image copyright Joggins Fossil Institute.
A seed fern, Alethopteris, on a stem from Joggins. Image copyright Joggins Fossil Institute.
Hylonomus lyelli, found at Joggins in the 1850s, housed at the Natural History Museum (London). Image copyright Joggins Fossil Institute.
Artists reconstruction of Hylonomus, by John Sibbick.
A lycopod tree embedded in the cliffs. Image copyright Joggins Fossil Institute.
The view of the Joggins Fossil Centre from above. Image copyright Joggins Fossil Institute.
“I went to see a forest” display at the Joggins Fossil Centre. Image copyright Joggins Fossil Institute.
Inside the Joggins Fossil Centre. Image copyright Joggins Fossil Institute.
Palaeontology has an ability to grab the public’s attention like no other subject. Perhaps it’s the size and ferocity of something like a T. rex, or maybe it’s the alien nature of something like Hallucigenia. Irrespective of whatever it is that makes the subject interesting to any given individual, it’s important because palaeontology is a great gateway into STEM subjects and is, in itself, one of the few ways in which we can understand about the evolution of life and the planet.
But how has the public’s perception of palaeontology changed with the times? Was it more popular in its infancy, when huge questions were still left unanswered, or is it more popular now, in the era of Jurassic Park, where animatronics and CGI can bring fossils ‘back to life’?
Joining us to discuss how palaeontological outreach has been conducted and received throughout its history is Dr Chris Manias, King’s College London. Chris is a historian of palaeontology and founder of ‘Popularizing Palaeontology‘, a network of scholars, scientists, museum professionals, artists, etc. who reflect on trends in palaeontological communication and build future collaborations.
An example of a museum archive, with folders full of documents. It is within archives such as these that Chris is able to piece back together historical events and perspectives.
An early natural history museum: the Gallery of Palaeontology in Paris, from Albert Gaudry, Les ancêtres de nos animaux dans les temps géologiques (1888). Image from the Biodiversity Heritage Library. Digitized by Harvard University, Museum of Comparative Zoology, Ernst Mayr Library. www.biodiversitylibrary.org
Early-twentieth century interest in dinosaurs frequently revolved around Sauropods. “Children viewing Brontosaurus (Apatosaurus) exhibit, 1927.” Image from Research Library | Digital Special Collections, American Museum of Natural History, accessed June 27, 2018, http://lbry-web-007.amnh.org/digital/index.php/items/show/22670.
Discussions at the first Popularizing Palaeontology workshop, held at King’s College London, September 2016.
“The Art of Extinct Animals” Pop-up Palaeoart Exhibition at King’s College London, December 2017, held as part of Popularizing Palaeontology Workshop 2 (Photography by Katya Morgunova)
Introduction from the first PopPalaeo workshop. Three workshops in total are available here.
PopPalaeo Workshop I, Paper 1: Chris Manias, Introduction - YouTube
Welcome to this special series of podcasts relating to a fieldtrip that I have been invited on by Dr Martin Brazeau of Imperial College London.
I’m being flown out as the Palaeozoic arthropod “expert” of the team and I’ll be there to deal with all the eurypterids and phyllocaridids we come across, along as documenting the whole process for outreach and hopefully your enjoyment.
In all, this trip will last around 6 weeks, during which time we’ll have no internet, electricity, running water or even any toilets. It’s going to be a gruelling trip, but hopefully one that will give you an insight into what life is like in the field. You will join us as we discuss the science, prepare for the trip, arrive in the field, go out digging and finally wrap things up. You will experience all the highs of discovering new and exciting fossils and the lows of when we’ve just all had enough. This expedition is a unique opportunity to share with you a single research project from start to finish, rather than just the results.
In this first episode, we contextualise why we’re going into the field. What is the current lay of the research landscape? What we already know? and what are we aiming to find out about the early evolution of the jawed vertebrates, a group to which we ourselves belong?
The vertebrate evolutionary tree. (a) the origin of jawed vertebrates, (b) the origin of crown-group gnathostomes (i.e. the common ancestor of all living jawed vertebrates + all descendants). Ostracoderms are a grade of jawless vertebrates covered in boney armour. Placoderms are the earliest jawed vertebrates and are also possess boney armour. They are currently thought to comprise an evolutionary grade, rather than a true group . Image from Qu et al. 2013, Scales and Dermal Skeletal Histology of an Early Bony Fish Psarolepis romeri and Their Bearing on the Evolution of Rhombic Scales and Hard Tissues.PLoS ONE 8(4) CC BY 2.5.
Vancouver Aquarium Hagfish Slime - YouTube
Hagfish are a group of living jawless vertebrates with the disgusting ability to secrete a microfibrous slime, which expands on contact with water. One of the uses of this slime is to clog potential predators gills.
Lampreys are another group of living jawless vertebrate. Their mouth has evolved into a sucker-like disc lined with horny ‘teeth’ made of the structural protein keratin. Some species of lamprey are parasitic. They attach to unsuspecting fish using their sucker-like mouth and rasp at the flesh using a horny tongue. Image from Wikimedia Commons CC BY-SA 3.0
Recent advances in the study of early jawed vertebrates from the Silurian and Early Devonian have changed perspectives on the evolution of the bony exoskeleton. Janusisicus from the Early Devonian of Siberia revealed a combination of features form bony fishes and placoderms, corroborating a hypothesis that the scaly exoskeleton of sharks and their relatives is an ‘advanced’ feature, rather than an ancestral state of jawed vertebrates. Image: Giles et. al. 2015.
Placoderms came in all shapes and sizes. One of the largest was Dunkleosteus, which lived during the Late Devonian period, about 358–382 million years ago. The largest species, D. terrelli, is estimated to have reached 6 meters in length and approximately 1 tonne in weight. Dunkleosteus belongs to a group of placoderms called arthrodires, the oldest of which have been found in the Silurian of China. Image from Wikimedia Commons, Public Domain.
The placoderm Bothriolepis was one of the most abundant early vertebrates during the Middle to Late Devonian. It belongs to a group of placoderms called the antiarchs. The oldest antiarchs so far discovered have been found in Silurian-aged sites in China.
Acanthodians, also known as ‘spiny sharks’, are a group of early jawed vertebrates known from the Silurian to Devonian periods, approximately 440 – 360 million years ago. Their evolutionary relationships have been the subject of much debate. Historically, it was though they represent a true group that diversified close to the origin of jawed vertebrates. It has also been suggested that some acanthodians might be more closely related to the boney fishes. More recently, it has been suggested that acanthodians represent a grade more closely related to living sharks and rays. Pictured is Obtusacanthus, an acanthodian from the earliest Devonian of Canada.
As well as looking for jawed vertebrates we are also on the hunt for ostracoderms, which are boney, jawless fishes. As their name suggests they lacked the classic vertebrate feature of a jaw and many other diagnostic characteristics, such as paired fins and a boney internal skeleton. Instead, many of the different ostracoderm groups had a boney ‘dermoskeleton’ which encased their bodies from the outside. They are really important for understanding the assembly of the early vertebrate skeleton and were the dominant fishes in early vertebrate faunas (Silurian to early Devonian).
NMC.30417 Homalaspidella is a cyathaspidid heterostracan from the Pridoli (420 million years ago in the Silurian) is an example of a jawless fossil fish we may expect to find in the Canadian Arctic (housed in the Canadian Museum of Nature, Ottawa).
NMC.19713 Vernonaspis is another cyathaspidid heterostracan from the Pridoli (Silurian 420 million years ago) is also an example of a fossil we may expect to find in the Canadian Arctic (housed in the Canadian Museum of Nature, Ottawa).
The earliest jawed vertebrates were contemporaneous with the ostracoderms (armoured jawless fishes). There is some evidence that jawed vertebrates preyed upon their jawless cousins, however the community dynamics of early vertebrate faunas are largely unknown. Martin, Dave and the team hope that new discoveries from Cornwallis Island will help us understand how the evolution of the gnathostomes effected early vertebrate communities. Image from Choo et al. 2014, The largest Silurian vertebrate and its palaeoecological implications. Scientific Reports4. CC 4.0
We now move on to discussing the logistics of the trip. How do you go about making this kind of expedition happen? What are some of the challenges we will face? What will life be like in the camp? and how will we get our priceless fossils home?
We first arrived in Ottawa a few days before headed to Cornwallis Island to make our final preparations. We still needed to get the last bits of equipment, practice safety procedures and squeeze in a visit to the Canadian Museum of Nature to check out their fossil collections.
The single most important thing was to bring along enough chocolate. Dave is here helping Martin’s mom prepare $120 worth of almonds in chocolate. Having such calorie rich food is important because we will be trekking many kilometres in the daytime, breaking rocks and carrying heavy loads, all in cold temperatures.
Another important thing we are taking are maps, we therefore stopped in at the World of Maps to get ours printed. We will be needing these, not only to find our way around the island, but to record the position of the discoveries and also the nature of the rocks we encounter. Geological mapping 101.
Here Anthony points out Cornwallis island on the globe. It’s pretty far north…
Another important thing, from a safety perspective, is to get familiar with the weapons we will be taking into the field. The team therefore headed to the shooting range to get hands-on experience of the rifles, ammunition and reloading process.
Since the condition of a gun changes with every round shot, we had to calibrate each rifle so that we can be sure of hitting what we’re aiming at. Our lives may depend on this if we encounter an aggressive polar bear.
Initially, our shots were a little off…
But soon we managed to get these to a good level of accuracy over 90m.
Here, Martin, Emma and Anthony look through drawers of Canadian Arctic fossils at the Canadian Museum of Nature’s Collections in Gatineau, Quebec.
It was important for us to visit the collections held in the Canadian Museum of Nature to get our eye in for the types of fossils we may be finding.
A jaw from a small Acanthodian jaw: a spiny shark from the Canadian Arctic, Canadian Museum of Nature
A frontal appendage of a carcinosomatid eurypterid. Each segment of this leg (top margin) possesses large sickle-shaped spines that were used for prey capture. Eurypterids, such as this, would have been amongst the top predators in the Silurian, but in the Devonian, the ‘age of the fishes’, they took a big hit to their diversity.
The field area showing the kind of environment we’ll be working in. These rocks were formed in shallow coastal waters during the Late Silurian, recording barrier reefs and muddy carbonate lagoons. They’re made up of limestone muds with corals and sponges providing a framework, similar to what is seen in the modern day reefs. Image: Jeff Packard
The upside to the conditions is that there will be huge amounts of exposure and access to rocks is guaranteed. On the downside, these rocks will likely be weathered, so there will be plenty of splitting required to get fresh surfaces. Image: Jeff Packard
Access into the field is only feasible by air, given the amount of equipment we are to be carrying. Aircraft capable of landing in the field are helicopters and the Twin Otter plane, the latter of which can be seen here flying over our field area.
CC-138 Twin Otter in Nunavut - YouTube
Check back here in a couple months to see what life was like in the camp and to see the amazing fossils that we’ve (hopefully) found!
Squamates are a group of reptiles that include lizards and snakes, with the earliest fossils occurring in the Jurassic, despite molecular studies dating the group back to the Triassic. The study of their origins has been contentious because of this gap, and the lack of fossils during this time period.
However, a new look at a previously-known fossil has changed our view of squamate origins, and discussing this animal and what it means about reptile relationships and squamates is Dr. Tiago Simões of the University of Alberta. This episode is based on a new paper published in Nature by Dr. Simões and colleagues.
Specimen of Megachirella wachtleri from the Middle Triassic of Italy, in dorsal view.
Computed tomography (CT) reconstruction of Megachirella, in dorsal view. From Simões et al. 2018.
CT reconstruction of the skull of Megachirella, in dorsal view. Image from Simões et al. 2018.
Life reconstruction of Megachirella wachtleri. Image copyright Davide Bonadonna.
Dated phylogenetic tree showing the relationships of major diapsid and squamate groups. From Simões et al. 2018.