Blogozoic

Diving Into the Past

How long can you hold your breath underwater? I’ll wager it wouldn’t be for much longer than a minute or two at most. The world record for a human is an astonishing 22.3 minutes set by Tom Sietas in June 2012 (link here). He did accomplish this with the aid of breathing pure oxygen for 30 minutes beforehand. The record without any aid is still an amazing 11.5 minutes. These extreme examples aside, the majority of the world’s population would struggle to achieve anything over two minutes. However, not all our mammalian cousins are as inept at staying submerged as us humans, especially those lineages that have returned the sea, such as the cetaceans (whales and dolphins), pinnipeds (seals) and sirenians (dugongs and manatees). These animals have evolved to be able stay underwater for much longer periods of time, with the longest dives undertaken by the northern elephant seal and the sperm whale, both of whom can dive for over an hour on a single breath! Marine mammals have evolved a whole suite of anatomical and physiological adaptations to enable themselves to undertake these long dives but key to their underwater exertions is the increased ability to store oxygen in their muscle tissues.

A model of a myoglobin molecule from a sperm whale. Image from en.wikipedia.org
A model of a myoglobin molecule from a sperm whale. Image from en.wikipedia.org

The protein molecule that allows mammals to store oxygen in their muscle tissues is known as myoglobin (in your blood oxygen is carried by haemoglobin). You can tell when this respiratory pigment is present in tissue as it gives it its red colour and, as any of you who have dissected a whale, dolphin or some other marine mammal will know, the elevated concentrations in their tissues cause their tissues to be very dark, even almost black in colour. Myoglobin is one of the best known and studied proteins but researchers were still unsure how marine mammals could use myoglobin in such high concentrations as it tends to clump and stick together when present in large amounts, therefore obviously making it difficult for it to be able to store oxygen in the body’s tissues.

A new paper published in the journal Science just over a week ago claims to have unravelled how marine mammals can take advantage of the elevated myoglobin concentrations and not get their tissues clogged up by the protein (Mirceta et al, 2013). What the researchers found was that mammalian divers have higher net surface charges on their myoglobin molecules, namely higher positive charges. What this does is cause the myoglobin molecules to stay apart from each other as (remember your high school physics) like charges repel, allowing there to be lots more myoglobin without it clumping together.

Graph showing how as the net surface charge (Zmb) increases, so does the concentration of myoglobin (Mbmax). Image from Mirceta et al. 2013.
Graph showing how as the net surface charge (Zmb) increases, so does the concentration of myoglobin (Mbmax). Image from Mirceta et al. 2013.

But what has this got to do with fossils I hear you ask? This is meant to be a palaeontology blog, not a physiology one! Well this is where an already interesting paper becomes even better. As the relationship between this increased net surface charge of the myoglobin molecules and the increased levels of myoglobin was statistically very robust, this allowed the researchers to use a process called ancestral sequence reconstruction to estimate what the myoglobin sequences of extinct mammals were and therefore estimate their diving capabilities!

Cool figure showing the evolutionary reconstruction of myoglobin net surface charge in terrestrial and aquatic mammals. Image from Mirceta et al. 2013.
Cool figure showing the evolutionary reconstruction of myoglobin net surface charge in terrestrial and aquatic mammals. Image from Mirceta et al. 2013.

There were several interesting results obtained from the ancestral sequence reconstruction, which was conducted for a 130 species phylogeny. It suggests that some extant terrestrial mammals actually may have had an amphibious ancestry. This may not sound immediately intriguing but when you consider that the groups they imply are taxa such as echidnas and moles, both of whom are very well adapted to a fossorial (digging/underground) lifestyle then it really does become more noteworthy. Interestingly, close relatives or even members of both groups (e.g. the platypus and the star nosed mole) still have an amphibious lifestyle. Another group which was found to have an amphibious ancestor was the Paenungulates. This large group contains terrestrial animals such as elephants and hyraxes as well as aquatic taxa such as dugongs, manatees, and the extinct desmostylians. Aquatic ancestry has long been debated for elephants and their kin (known as the Proboscidea) and this study provides evidence for a fossil species of proboscidean possessing a higher net surface charge of its myoglobin, with the modern levels representing a secondary reduction in net surface charge.  The authors themselves note that an aquatic ancestry for the hyraxes may seem surprising when current diversity is considered, but there are much larger fossil species for which a semiaquatic lifestyle has been proposed in the past. Another interesting point is that if the common ancestor of the Paenungulates was indeed aquatic, it would represent the earliest placental mammal radiation into the aquatic realm. At an estimated 64 million years ago it would predate the cetaceans and the pinnipeds reinvasion of the water.

Figure showing the evolution of myoglobin net surface charge and aquatic habits in Afrotheria. Note how the fossil proboscidean Moeritherium was more aquatic than modern taxa. Image from Mirceta et al. 2013.
Figure showing the evolution of myoglobin net surface charge and aquatic habits in Afrotheria. Note how the fossil proboscidean Moeritherium was more aquatic than modern taxa. Image from Mirceta et al. 2013.

Furthermore, by using the relationship between maximum dive time, muscle myoglobin concentration and body mass in extant (living) species, they also estimated maximum dive time in extinct species too (using estimates of body mass for the extinct species). This type of ecological information has been nothing more than an educated guess based on morphology and internal bone structure until now, where Mirceta et al. have constructed a robust model to estimate the dive times of extinct taxa. From their model the team have estimated that one of the earliest known cetaceans, the early Eocene Pakicetus could only hold its breath for 1.6 minutes, whereas by the late Eocene, cetaceans had evolved to the point where Basilosaurus was capable of staying submerged for 17.4 minutes, a figure comparable to modern dolphins. In pinnipeds, the earliest known taxon Enaliarctos has an estimated maximum dive time of 4.7 minutes, which is poor compared to modern seals, perhaps reflecting the fact that it hunted in shallower waters than its modern counterparts? In the proboscideans (the group containing elephants, mammoths, mastodons etc.), the secondary change back to a terrestrial lifestyle (already mentioned above) is reflected in the result that a fossil proboscidean (Moeritherium) had an estimated dive time of 10 minutes, compared to 2.5 minutes in the modern Asian elephant.

Graphs showing diving capacity in ancestral whales, seals, and sea cows. Image from Mirceta et al. 2013.
Graphs showing diving capacity in ancestral whales, seals, and sea cows. Image from Mirceta et al. 2013.

This is a really fascinating paper and the best thing about it is that it gives researchers a whole new raft of hypotheses to go away and test. This shows what can be done when a multidisciplinary approach is used in the right way, integrating molecular technologies and fossil data to produce insights that would have been thought impossible previously, giving scientists a new way to think about their fields. Science, you’ve done it again.

References

Mirceta S, Signore AV, Burns JM, Cossins AR, Campbell KL, Berenbrink M (2013) Evolution of Mammalian Diving Capacity Traced by Myoglobin Net Surface Charge. Science 340: 1234192.

Australian Megafauna A-Z: A is for Alkwertatherium

This blog has been going for just over four months now and a couple of weeks ago I broke through the 2,000 hits barrier. Whilst that may be a drop in the ocean for some of the more popular blogs on the internet, the fact that my inane ramblings about palaeontology have been viewed over 2,000 times feels pretty cool and definitely spurs me on to keep writing the blog. So if you’re someone who’s been here before, thank you, I hope you’ve enjoyed my articles and will continue to do. If this is your first time here, welcome!

Now that there are least a trickle of people who read the blog on a semi-regular basis, I wanted to start the first regular feature on Blogozoic. Since I’m a palaeontologist (in training) working in Australia I thought that I should write a series of posts showing off some of Australia’s extinct beasties. So this is the first post in the Australian Megafauna A – Z. Every now and again there will be a new post covering an extinct megafauna taxon whose name begins with a different letter. I do also have an ulterior motive for doing this as it means I will become more familiar with the Australian megafauna whilst I write the series; having not grown up in Australia (I’m originally from Belfast, Northern Ireland and have lived in Melbourne for the past six years), I’m not as clued up on this group of animals as I would like to be.

Before I introduce the first species of the series, I’ll quickly define what I mean when I say Australian megafauna. They were a of group large animal species that existed in Australia until sometime in the Pleistocene. They weighed at least 30 kg, with the largest taxa weighing up to an estimated 2,000 kg! What exactly caused the Australian megafauna to go extinct is still the subject of very intense debate here in Australia, with research continually providing new perspectives on the matter (e.g. a PLOS One paper that came out last week showed via isotope analysis of kangaroo and diprotodontid teeth that southeastern Queensland in the late Miocene and Pliocene was less arid than previously thought, with tropical forests, wetlands and grasslands all present (Montanari et al 2013)). The Australian megafauna were comprised mostly of marsupials, but also contained reptiles and birds, some of which we’ll meet in subsequent posts. Let’s meet the first species in this series then shall we? The first taxon under the spotlight is Alkwertatherium webbi.

Alkwertathrium webbi is a zygomaturine diprotodontid known only from the Alcoota Local Fauna in Northern Territory. The diprotodontids were medium to large sized herbivorous marsupials that included the largest known marsupial, the rhino sized Diprotodon opatum (you may hear about it in a few posts time). There are two currently recognised sub-families of diprotodontids, the Diprotodontinae and the Zygomaturinae, of which A. webbi belongs to the latter. The two sub-families are distinguished mainly on the basis of differences in the structure of their third premolar.

Alkwertatherium webbi was a small zygomaturine, around the size of a horse. The holotype specimen, found at the famous fossil bearing site at Alcoota Station, includes a skull with lower jaws and measured just over 40 cm in length. The features of Alkwertatherium’s skull show similarities to several other zygomaturine taxa, causing confusion to those who have attempted to decipher its phylogenetic position. Some workers (Black and  Archer, 1997) have placed it within the Zygomaturinae, whereas Murray (1990), in the paper where he described the holotype specimen, suggested it was in fact the sister taxa to all other zygomaturines, a claim that would mean it was the sole survivor of this ancestral group due to its Late Miocene age. Mackness (2010) follows the placement of Black and Archer (1997), in addition to stating that the archaic features of Alkwertatherium support the view that the Zygomaturinae evolved from basal Diprotodontinae.

The holotype skull of Alkwertatherium webbi. Apologies for the crappy picture quality, this is a scan from Wildlife of Gondwana by Pat & Tom Rich.
The holotype skull of Alkwertatherium webbi. Apologies for the crappy picture quality, this is a scan from Wildlife of Gondwana by Pat & Tom Rich.

Despite not being as well-known as other extinct megafauna taxa, Alkwertatherium gives a glimpse into past diversity in Australia. That’s the first in the Australian Megafauna A – Z Series; stay tuned for more to come in the following months!

References

Black, K and Archer, M (1997) Silvabestius gen. nov., a primitive zygomaturine (Marsupialia, Diprotodontidae) from Riversleigh, northwestern Queensland. Memoirs of the Queensland Museum 41: 193-208.

Mackness, B (2010) On the identity of Euowenia robusta De Vis, 1891 with a description of a new zygomaturine genus. Alcheringa 34:455-469.

Montanari S, Louys J, Price GJ (2013) Pliocene Paleoenvironments of Southeastern Queensland, Australia Inferred from Stable Isotopes of Marsupial Tooth Enamel. PLoS ONE 8(6): e66221. doi:10.1371/journal.pone.0066221

Murray, PF (1990) Alkwertatherium webbi, a new zygomaturine genus and species from the late Miocene Alcoota Fauna, Northern Territory (Marsupialia, Diprotodontidae). The Beagle, Records of the Northern Territory Museum of Arts and Sciences 7: 53-80.       

My Academic Ancestry

Apologies for the long gap between posts readers (all three of you), it has been a combination of PhD work, other research, grant writing and my own sheer laziness that has caused it. Hopefully the lull will be a temporary occurrence and I will get back to posting once a week again from now on. But I digress…

A few weeks ago I received an interesting email from one of my PhD supervisors. In it he explained how he had traced his (and by extension my) academic ancestry. That is, who his PhD supervisor was supervised by, and who their supervisor was etc. After reading the list of names (and discovering a few missing links myself), the pressure I’m already feeling about my project increased quite a bit! There are some big names in my academic ancestry, I’ve got my work cut out if I want to accomplish even a portion of what these guys achieved. Here’s my academic ancestry:

My academic ancestry. No pressure there then!

Some names you may be extremely familiar with, some perhaps not so much. So here’s a little bit about each of them to give you an idea of whose shoulders I’m attempting to stand on.

Erich Fitzgerald: My current PhD co-supervisor (the other being Alistair Evans from Monash University). Erich is senior curator of vertebrate palaeontology at Museum Victoria in Melbourne. He also co-supervised me for my honours research on Australian fossil penguins and has been a co-author on all three papers I’ve written so far. In addition to trying to do the impossible and make a palaeontologist out of me, Erich’s research focuses on marine mammals, but he also works on birds, sharks, dinosaurs (non-avian), aquatic reptiles and terrestrial mammals. He received his PhD from Monash University in 2008 and was also a Postdoctoral Fellow at the National Museum of Natural History (Smithsonian) as well as the Harold Mitchell Fellow at Museum Victoria before taking up his current position.

EMGF MV pic
My PhD co-supervisor (and for the purposes of this post my academic father), Erich Fitzgerald. Image from Museum Victoria.

Tom Rich: Tom was and still is one of the heavyweights of Australian palaeontology.  After studying at University of California, Berkeley, and Columbia University, New York Tom moved to Australia to take up his current position as senior curator of vertebrate palaeontology at museum Victoria. With his wife Pat Vickers-Rich (who still teaches at Monash University) they embarked upon a 23 year long quest to find Toms overriding passion; Mesozoic mammals, which involved them blasting a tunnel into the rock at the base of a 30 m high cliff at what is now known as dinosaur cove in the Otways here in Victoria (click here for a previous post by me detailing the most recent field trip to a nearby locality). Tom eventually got his Mesozoic mammal (and plenty more since then) but along the way has revealed more about the vertebrate palaeontology of Victoria than just about anyone else.

My academic grandfather, Tom Rich. Image from Museum Victoria.
My academic grandfather, Tom Rich. Image from Museum Victoria.

Malcolm McKenna: one of the most prolific palaeontologists in America in the 20th century, McKenna was curator of the prestigious American museum of natural history in New York. Like his mentor, George Gaylord Simpson he specialised in mammals and in 2000 he published a voluminous new edition of Simpson’s 1945 tome the classification of mammals with Susan bell. Also in 2000 he received the Alfred Romer medal from the SVP, the highest honour they give out. He also was a pioneer of the use of cladistics in palaeontology, a method which has since become a fundamental part of the field. He passed away in 2008.

My academic great-grandfather, Malcolm McKenna. Image from ucmp.berkeley.edu.
My academic great-grandfather, Malcolm McKenna. Image from ucmp.berkeley.edu.

Donald Elvin Savage:  Born in Texas in 1917, Don Savage completed his undergraduate studies in his home state before moving to Oklahoma to undertake his Masters research. After WWII (where he spent six years in the U.S. Air Force), Savage relocated to University of California, Berkeley to complete his PhD. After completing his PhD in 1949, he took up a position at the University Of California Museum Of Palaeontology, where he eventually became the Director of in 1966. Like the majority of the scientists on this distinguished list, Savage specialised in the study of fossil mammals, with his research taking to locations such as Colombia, France and all over the USA, making an incredible contribution to the understanding of mammalian evolution as well as helping to develop and refine collection techniques of small vertebrate fossils. Savage died of pancreatic cancer in 1999, aged 81.

My academic great-great-grandfather, Donald Savage. Image from ucmp.berkeley.edu.
My academic great-great-grandfather, Donald Savage. Image from ucmp.berkeley.edu.

Ruben Arthur Stirton: Another name, another mammalogist! Stirt, as he liked to be called was born in Kansas in 1901. After studying zoology at the University of Kansas, Stirton took part in expeditions to El Salvador before heading to University of California, Berkeley to complete his PhD. In 1930 Stirton became the Curator of fossil mammals in the University Of California Museum Of Palaeontology, where he also lectured courses on fossil mammals. Stirton eventually rose to become Director of the museum in 1949 and held the position until his death in 1966. Whilst his early work looked at horses and beavers from western USA, Stirton also returned to El Salvador in 1941 to continue his previous work there. He continued his South American exploits in 1944 when he conducted a search for fossil mammals in Colombia, work that was continued by Savage afterwards. Stirton then shifted his focus to Australia in 1953, discovering several new Cenozoic faunas with the assistance of the South Australian Museum. This work was instrumental in Tom and Pat Rich’s decision to relocate to Australia several decades later. Stirton died of a heart attack in 1966.

My academic great-great-great-grandfather, Ruben Stirton. Image from ucmp.berkeley.edu.
My academic great-great-great-grandfather, Ruben Stirton. Image from ucmp.berkeley.edu.

William Diller Matthew: Taking my academic ancestry into the 19th century is the Canadian William Diller Mathew. Born in New Brunswick in February 1871, Matthew’s love of the earth sciences appears to have run in the family as his father was a geologist. After completing his PhD at Columbia University he, like McKenna after him, took the position of curator at the American Museum of Natural History, where he remained for some 33 years until he became the founding director of the University Of California Museum Of Palaeontology in 1927.  Matthew, like his academic offspring, specialised in mammals but he also wrote papers on invertebrates, geology, mineralogy and even botany! As distinguished and successful a palaeontologist as Matthew no doubt was, he (understandably considering the lack of evidence in his time) got some things wrong, most notably arguing against continental drift and supporting the theory of an Asian origin for humans. Had he the evidence at his disposal that we do today; no doubt he would have abandoned his theories too.

My academic great(x4)-grandfather, William Diller Matthew. Image from commons.wikipedia.org.
My academic great(x4)-grandfather, William Diller Matthew. Image from commons.wikipedia.org.

Henry Fairfield Osborn: Born into a wealthy family in 1857, Osborn is one the best known figures in the history of vertebrate palaeontology. After studying at Princeton University, he became both a professor of zoology and the very first curator of vertebrate palaeontology at the American Museum of Natural History in New York, where so many of his academic descendants would also reside. Another mammal specialist, he also became the US geological survey’s senior vertebrate palaeontologist in 1924, and ended up becoming president of the American Museum of Natural History, playing an instrumental part in building its amazing collections. Perhaps his defining achievement came in 1905 when he named none other than Tyrannosaurus rex itself, surely the most well-known dinosaur in the world. Osborn’s legacy will forever be tainted however as he attempted to use his scientific knowledge to validate his own racist and eugenicist beliefs. Had he not done this then perhaps history would remember the great scientific work he did more fondly.

My academic great(x5)-grandfather, Henry Fairfield Osborn. Image from junglekey.fr.
My academic great(x5)-grandfather, Henry Fairfield Osborn. Image from junglekey.fr.

Edward Drinker Cope: Born in 1840, this behemoth of the palaeontology world published his first scientific paper at the young age of nineteen, by the time he died in 1897, he had amassed 1,400 publications to his name, a truly phenomenal feat regardless of whether every single paper has stood the test of time (some have since been discovered to be inaccurate). Cope is best known for his longstanding rivalry with fellow palaeontologist Othniel Charles Marsh, the period from the 1870’s to the 1890’s known as the “Bone Wars”. Cope didn’t actually publish his first palaeontological paper until 1864 (having published mainly on reptiles and amphibians previously) but certainly made up for lost time afterwards, managing a remarkable 76 publications in a year spanning 1879-1880. His efforts competing with Marsh drove him to the point of exhaustion and bankruptcy and he ended up having to sell a large proportion of his fossil collection. His legacy lives on in the vast literature he wrote as well as the many species of animals that have since been named after him, including amphibians, dinosaurs, lizards and fish.

My academic great(x6)-grandfather, Edward Drinker Cope. Image from commons.wikipedia.org
My academic great(x6)-grandfather, Edward Drinker Cope. Image from commons.wikipedia.org

Joseph Leidy: The last of my academic ancestors is one of the founding fathers of vertebrate palaeontology in America, Joseph Leidy. He produced some of the earliest works on extinct vertebrates from North America, naming well known taxa such as Hadrosaurus, the dire wolf and the American lion. He was a professor of anatomy and natural history during his career and in addition to his palaeontological work also was renowned for his research on parasites. Whilst not as prolific as his academic son Edward Drinker Cope, he still managed to write an incredible 553 publications during his scientific career.

My academic great(x7)-grandfather, Joseph Leidy. Image from commons.wikipedia.org.
My academic great(x7)-grandfather, Joseph Leidy. Image from commons.wikipedia.org.

So that’s my academic ancestry! As you can see, there are some truly great names there. Do you know who your academic ancestors are? I’d be interested in hearing what other peoples academic ancestry reveals. Feel free to drop me an email (address at the top of the blog homepage) or leave a comment. You never know, we could be academic relatives!

Palaeos of a Feather, Communicate Together!

No feathers. #JP4. With that short sharp statement on 21st March via Twitter, Colin Trevorrow, the director of the forthcoming instalment of the Jurassic Park franchise has sent the palaeo community into a frenzy of disbelief and dismay. But after going to see Jurassic Park 3D (it’s still awesome) on Saturday night and being painfully reminded of it every time a theropod was on-screen, I believe that since there doesn’t seem to be any chance of the feathered dinosaurs being accurately portrayed in the new JP we, the palaeo community, should try to turn this disappointing situation to our advantage and communicate how dinosaurs actually were in life.

Even large theropods such as this Yutyrannus huali have been found with some sort of fuzzy covering. Artwork by Brian Choo.
Even large theropods such as this Yutyrannus huali have been found with some sort of fuzzy covering. Artwork by Brian Choo.

In the coming year there will be a wave of publicity as the release of JP4 nears. We should be riding the crest of this wave and using it as a soapbox to communicate to the public that no, dinosaurs were not just scaly monsters, but as we’re coming to realise, multiple species had feathers, feathers were a common characteristic of dinosaurs and some sort of fuzzy covering appears to have been have even more widespread across the various dinosaur lineages.

Let me be clear though, when I read the news that there would be no feathers in JP4 I was as aghast as the next evidence appreciating person. But having had time to reflect on the decision (which appears to be based on “continuity”) I am determined to not let this prevent the truth that many dinosaurs were feathered from getting communicated to as many members of the public as possible. I’m aware it’s not like scientists have hid these finds away from the public until now, but judging by the amount of people commenting on the various articles covering this announcement that actually support the decision and don’t seem aware of it, there are still people who don’t realise just how prevalent feathers were and how the behaviours and traits they associate with birds only were already there in dinosaurs (I know they are actually the same thing). Just because the dinosaurs you imagined in your childhood were scaly dragon-esque creatures doesn’t mean that they have to remain that way forever (or else they would still be swamp dwelling, tail dragging leviathans).

Citipati is shown here brooding on its nest of eggs in a pose that you can still see today in living birds. Image from Clark et al. 1999.
Citipati is shown here brooding on its nest of eggs in a pose that you can still see today in living birds. Image from Clark et al. 1999.

So consider this as a call-to-arms (of the communicational variety). I know that a lot of science writers will already be planning to do this or already have done so to a certain extent. So this may seem to some people like I’m stating the obvious here. But I’m not just talking about people like myself who are regularly communicating science via blogs, Twitter etc. If we, as a community, make as much noise as we can, via as many media as possible when the public is just about to see the new movie, then we can ensure that more people than ever before are aware not only that many dinosaurs were feathered, but also convey to the public how much our understanding is improving of these magnificent creatures. The biggest success story of vertebrate palaeontology in the past two decades is the overwhelming confirmation that birds are in fact living dinosaurs. If Colin Trevorrow isn’t going to show the world just how awesome feathered dinos were, then it’s up to us.

Field trip to the Otways

Another post, another field trip! I’ve been quite fortunate so far this year, this trip was my third already and it’s only March (I think my fiancé has forgotten who I am)! In my defence though, this trip was only a short two night stay, with a day and a half worth of field work.

But enough already, where did I go? The locality we were digging at is known as Eric the Red West and it is situated on the southern coast of Victoria’s Otways ranges, around four hours west of Melbourne. The name of the site comes from a famous ship known as Eric the Red that wrecked there in 1880, whose anchor lies just east of our dig site, hence the Eric the Red West! The rocks at this locality are similar to those found at the site of my last field trip at Flat Rocks, Inverloch, which is on the other side of Melbourne. However the rocks in the Otways, although also Early Cretaceous, are around 10 million years younger than those found at Inverloch. They would have once been part of the same single unit but geological events in the Miocene have split them into two separate groups. The fossils found from the Otways are from the Eumarella Formation, Otways Group and the Flat Rocks fossils are from the Wonthaggi Formation, Strzelecki Group (Benson et al., 2012). This temporal difference between the two areas gives us a unique opportunity to study the evolution of life here in Victoria during the early Cretaceous as we can compare the two sites and look for differences in the flora and fauna.

Map showing not only the Eric the Red West site and the Flat Rocks site at Inverloch, but other fossil localites from Victoria. Image from Benson et al., 2012.
Map showing not only the Eric the Red West site and the Flat Rocks site at Inverloch, but other fossil localities from Victoria. Image from Benson et al., 2012.

Another bonus of a field trip to the Otways is the camp we get to stay in. Called Bimbi Park, it is situated right in the middle of the Otways Ranges National Park (so no Internet, hence the lateness of this blog post) where you are surrounded by trees full of Koalas, although at night when you’re trying to sleep and the males won’t stop bellowing they can lose their appeal momentarily! It really is a beautiful picturesque spot for getting away from it all and I’d definitely recommend it should you ever find yourself in that neck of the woods.

Picture of the campsite at Bimbi park. You really do get to sleep with Koalas above your head! Image from planbooktravel.com
Picture of the campsite at Bimbi park. You really do get to sleep with Koalas above your head! Image from planbooktravel.com

Tourism plugs aside, there have been several notable finds at the Eric the Red West site since it was first prospected in 2005 (Kool, 2010). There tends to be fewer finds at the Otways site, but the material is often of better quality than Flat Rocks. One of the best came on that very first day of prospecting when an articulated tail and complete right foot of a small ornithopod dinosaur was discovered. In 2006 Inverloch and Otways dig stalwart Mary Walters found a mammal jaw (not her first one either) and more recently, dig regular Alanna Maguire has found the first upper mammal jaw from the Cretaceous of Australia (something that is still being researched at present).

The mammal jaw Mary Walters found at the Eric the Red West site in 2006, prompting an annual field season there every year since. Image from the 2007 Dinosaur Dreaming Field Report.
The mammal jaw Mary Walters found at the Eric the Red West site in 2006, prompting an annual field season there every year since onwards. Image from the 2007 Dinosaur Dreaming Field Report.

This field season is proving to be a very profitable one with the record for number of bones found in one day at the site being broken on the Monday I was there, and just prior to writing this post I read (via the Dinosaur Dreaming blog) that they had found two ornithopod jaws! There are some very exciting fossil layers being chased into the rock at present and hopefully they keep finding more cool stuff!

Now, where should I go for my next field trip…?

References

Benson, RBJ, Rich, TH, Vickers-Rich, P, Hall, M (2012) Theropod Fauna from Southern Australia Indicates High Polar Diversity and Climate-Driven Dinosaur Provinciality. PLOS One 7(5): e37122. doi:10.1371/journal.pone.0037122.

Kool, L (2010) Dinosaur Dreaming. Exploring the Bass Coast of Victoria. New Artworx, Melbourne. 95pp.

Ukrainian fossil giant salamander provides new insights into group’s origins

Amphibians are perhaps one of the less popular tetrapod groups. Most people would rather look at a furry mammal or feathered bird than a slimy newt or toad. This doesn’t mean that the group, consisting of frogs, toads, salamanders and the limbless caecilians, aren’t interesting. In fact, the first vertebrates that made the transition to life on land some 370 million years ago were amphibians so we all owe a debt of gratitude to our moist-skinned cousins! Since then, they have continued to successfully adapt and survive, with around 7,000 species alive today. The largest amphibians in the world today are the Chinese giant salamander (Andrias davidianus) and the Japanese giant salamander (Andrias japonicas), which can reach lengths of over 1.5 m. In the video below (narrated by the one and only, legendary, awesome and über-cool David Attenborough) you can see how amazing these animals really are and why they should maybe get more attention than they do.

But what is even cooler than giant salamanders? Fossil giant salamanders of course! And a new paper by Vasilyan et al. published in the most recent issue of the Journal of Vertebrate Paleontology has just described a new species of giant salamander from Ukraine and revealed new insights into the origins of the group (known scientifically as Cryptobranchids). The new species, Ukrainurus hypsognathus is middle-late Miocene in age (around 11.5 million years) and was found in an abandoned quarry just southeast of the village of Grytsiv, western Ukraine. The holotype is a left dentary (shown below) and other cranial elements and several postcranial elements have also been assigned to the same individual.

The holotype dentary of Ukrainurus hypsognathus shown in A, lingual; B, dorsal; C, labial; D, ventral views. Scale bar = 1 cm. Image from Vasilyan et al. 2013.
The holotype dentary of Ukrainurus hypsognathus shown in A, lingual; B, dorsal; C, labial; D, ventral views. Scale bar = 1 cm. Image from Vasilyan et al. 2013.

By studying the dentary and other cranial elements of U. hypsognathus, Vasilyan et al. were able to establish that it would have had a considerably strong bite force, with which it would have used to feed on prey such as fish, frogs and even other salamander species that are also known from the locality. They also found that the jaw of U. hypsognathus would have been less flexible than that of modern giant salamander species, meaning its method of prey capture may have differed slightly from that of modern taxa.

The phylogeny of Vasilyan et al. 2013. You can see that Ukrainurus hypsognathus is sister to all crown Cryptobranchids. Image from Vasilyan et al. 2013.
The phylogeny of Vasilyan et al. 2013. You can see that Ukrainurus hypsognathus is sister to all crown Cryptobranchids. Image from Vasilyan et al. 2013.

This paper is also the first study in which the relationships between fossil and recent species of giant salamanders have been analysed in a phylogenetic context. The results of the phylogenetic analysis show that U. hypsognathus is the sister taxon to crown group Cryptobranchidae. The single living American species Cryptobranchus alleganiensis was also found to be the sister taxon of all Eurasian cryptobranchids. A fossil cryptobranchid from Saskatchewan, Canada (excluded from the final phylogenetic analysis) was found not to be closely related to C. alleganiensis, but would have placed more basally in the phylogeny, closer to U. hypsognathus.

What this all implies is that Cryptobranchidae originated in Asia and dispersed to North America on two separate occasions. In terms of the timing of these events, the oldest crown Cryptobranchid is Aviturus exsecratus from the Palaeocene of Mongolia. This means that the split between crown and stem Cryptobranchidae would have had to occur in the Palaeocene at the latest and possibly even in the Late Cretaceous. When exactly the C. saskatchewanensis and C. alleganiensis lineages dispersed to America remains uncertain however.

With the majority of fossil cryptobranchids being known from Central rather than Eastern Europe, it would appear that there could well be more new insights to come on the evolution of the giant salamanders, surely an interesting group of amphibians if there ever was one.

Reference

Davit Vasilyan , Madelaine Böhme , Viacheslav M. Chkhikvadze , Yuriy A. Semenov & Walter G. Joyce (2013): A new giant salamander (Urodela, Pancryptobrancha) from the Miocene of Eastern Europe (Grytsiv, Ukraine), Journal of Vertebrate Paleontology, 33:2, 301-318.         

Getting inside the head of a fuxianhuiid

If you were to look at the diversity of life on Earth today, you could be forgiven for thinking that animals have always been around and have dominated the planet since time memorial. However, you would in fact be completely wrong! Animals have only been around for roughly 600 million years whilst life first evolved over 3.5 billion years ago and remained in single-celled form for the majority of the Earth’s history.

The period when animals rapidly diversified into the majority of extant phyla is known as the ‘Cambrian explosion’, which began approximately 545 million years ago during the Cambrian period. One particularly enigmatic example of this is the Burgess Shale, where beautifully preserved animals, some of which are unlike anything alive today, have been found.

This odd looking creature is Opabinia, one of the enigmatic products of the Cambrian explosion. It possessed five eyes which were on stalks, and a long proboscis which it used to grab its food! Image from paleobiology.si.edu
This odd-looking creature is Opabinia, one of the enigmatic animals of the Burgess Shale. It possessed five eyes which were on stalks, and a long proboscis which it used to grab its food! Image from paleobiology.si.edu

Until the past few decades, the Burgess Shale has stood out as our best glimpse into this stage of the evolution of life on Earth. However in China, several localities (e.g. Chengjiang) have been found, producing fossils of equally exquisite detail which scientists have been excitedly studying. The advantages of localities like these is that we can decipher how living groups first evolved and what would most likely have been the ancestral state for our modern animal groups.

Two new fossil species, described this past week in the journal Nature give us just such an insight for arthropods, the group containing animals such as insects, crustaceans, centipedes, spiders and the extinct trilobites. The fossils, named as Chengjiangocaris kunmingensis and Fuxianhuia xiaoshibaensis are from a group known as the fuxianhuiids, which are regarded as representatives of early arthropods.

Chengjiangocaris kunmingensis, the image on the left shows a reconstruction of the animal with the feeding tube and nerve cord shown running the length of the animal. The image on the right shows a specimen with the head 'taphonomically dissected', allowing the researchers to see the limbs and nerve cord properly for the first time. Images from Yang et al. 2013.
Chengjiangocaris kunmingensis, the image on the left shows a reconstruction of the animal with the limbs shown on the head of the animal and the feeding tube and nerve cord shown running the length of the animal. The image on the right shows a specimen with the head shield ‘taphonomically dissected’, allowing the researchers to see the limbs and nerve cord properly for the first time. Images from Yang et al. 2013.

The fossils, which were found in a Lagerstätte (a locality of exceptional preservation) near the city of Kunming in the Yunnan province of China, have been dated to approximately 520 million years old, meaning they are from a relatively early stage of the ‘Cambrian explosion’. Previous specimens of fuxianhuiids have had their heads covered by their head shield, part of the tough exoskeleton that is synonymous with arthropods. This has meant that debate over what exactly the paired post-antennal structures in other fuxianhuiids actually represented has never had a clear resolution. Until now that it is. In a stroke of geological good fortune, numerous specimens of the two new fuxianhuiid species have experienced ‘taphonomic dissections’, where the conncective tissues of the head shield have softened before final burial allowing the head shields to rotate forwards, exposing the structures underneath and making them visible to scientists for the first time.

The holotype specimen of Fuxianhuia xiaoshibaensis. At the top of the image you can see where the head shield has rotated forward, revealing the structures underneath. Image from Yang et al. 2013.
The holotype specimen of Fuxianhuia xiaoshibaensis. At the top of the image you can see where the head shield has rotated forward, revealing the structures underneath. Image from Yang et al. 2013.

The fossils are so well-preserved that the functional articulation of these post-antennal structures can be explained. The limited range of movement in the limbs means that they would most likely have been used to sweep detritus into the mouth, where the food particles would then have been filtered out of it.  The nerve cord is also the first documented
case of a preserved post-cephalic central nervous system in a stem group arthropod. It is simple in structure, especially compared to animals alive today (perhaps as expected).

The locality these fossils were found has just begun to be explored. With the potential for more insights into this pivotal period in the evolution of life and finds with this quality of preservation, I could very well be writing more articles on invertebrates sooner than I think!

References

Jie Yang, Javier Ortega-Hernández, Nicholas J. Butterfield, Xi-guang Zhang. Specialized appendages in fuxianhuiids and the head organization of early euarthropods. Nature, 2013; 494 (7438).

Field trip to Flat Rocks, Inverloch

For the past week I’ve been at a dinosaur dig I’ve been fortunate enough to attend every February since 2010. The dig, jointly organised by Monash University and Museum Victoria, is known as Dinosaur Dreaming and has been running every summer for the past 20 years, making it potentially the longest running dinosaur dig in the world!

The Dinosaur Dreaming site is approx. 113 km SE of Melbourne and has yielded numerous fossils for the past two decades. Image from Google maps.
The Dinosaur Dreaming site is approx. 113 km SE of Melbourne and has yielded numerous fossils for the past two decades. Image from Google Earth.

The locality is dated as Aptian (Early Cretaceous, ~120 Ma) and represents a a floodplain that existed in the rift valley formed by the gradual separation of Antarctica and Australia, a process that wasn’t completed until over 80 million years later. The supercontinent that these two continents formed part of (along with South America, Africa and India) was known as Gondwana. The fossils are found in layers in the light grey sandstone and conglomerate, along with abundant coal, fossilised tree stumps and other plant material. It is believed that the fossil material would have been swept in from locations upriver during episodes of flooding that caused the main rivers nearby to burst their banks. These fossil layers are what we look for when we dig at this site. It usually means having to clear off a sizeable amount of sand each morning to reaccess the fossil layer! Once we’ve cleared off the overburden a few crew members then use sledgehammers to break large chunks of rock out of the ground which is then passed to other crew members who break it down into sugar cube sized pieces searching for the fossils within.

Yours truly examining a rock to see if there any fossils inside. I almost look like I know what I'm doing! Image by Darren Hastie.
Yours truly examining a rock to see if there any fossils inside. I almost look like I know what I’m doing! Image by Darren Hastie.

And what type of fossils are we looking for exactly? Well, so far finds have included: dinosaurs (ornithopod and theropod), mammals, turtles, freshwater plesiosaurs, pterosaurs and fish, giving us a reasonably good idea of what made up this Early Cretaceous ecosystem. The downside is however that, as the material has been swept in by flooding, it is very rarely that complete elements are found (although keep your eyes peeled at the end of 2013/start of 2014 for something truly amazing coming from the site…). It is much more common to find small fragments of fossils that researchers then have to use all of their experience to piece the animal back together again, both literally and figuratively!

Another plus about the dig is that it provides school children from right across the state the chance to come and see what a real life dinosaur dig looks like (I wish I had that when I was a kid), they even get the chance to have a look for some fossils themselves!

The dig has its very own blog too, which keeps the public up to date with the goings on of the dig and what the diggers get up to during the rest of the year. Check out this video on the dinosaur dreaming blog, which shows the dig site and what we do, it even includes a short appearance by yours truly right at the end!

A massive thank you must go to Lesley, Gerry, Dave, Wendy, John and Lisa for all their hard work in keeping the dig going for as long as they have, hopefully it can last another 20 years!

 

The Lark Quarry Trackway: Thulborn Strikes Back

UPDATE: I made a slight mix up when writing this article last week. I have stated that Thulborn, 2013 is responding to the claims of Romilio et al. 2012. This is actually incorrect. The paper to which Thulborn is responding is Romilio and Salisbury, 2011, where they dispute the identity of the large track maker at Lark Quarry and its consequences for the interpretation of the trackway. Thulborn has not yet responded to the new claims in Romilio et al. 2013, although he may do so in future. The core message of the article however is still the same. Romilio et al. do not believe that the trackway at Lark Quarry represents a dinosaur stampede, whereas Thulborn maintains it does. This intriguing topic will no doubt continue to provide ample material for debate in the years to come. This article has been edited from its original and second versions. For anyone who wants to see the original version, email me at the address at the top of the blog.

Regular readers of this blog (if there is such a thing) may recall that I wrote an article about a new paper by Romilio & Salisbury where they disputed the claims made by Tony Thulborn, who stated that the dinosaur trackways at Lark Quarry, Queensland were made by stampeding dinosaurs. In their paper they proposed that in fact the trackways were made at different times and showed dinosaurs crossing a river.

Perhaps a stampede after all? Thulborn certainly still seems to think so. Image from abc.net.au.
Perhaps a stampede after all? Thulborn certainly still seems to think so. Image from abc.net.au.

Now, Thulborn has responded to the claims made by Romilio & Salisbury, 2011, rejecting their analysis. In his rebuttal, Thulborn criticises their application of the multivariate analysis method, pointing out that they didn’t actually compare trackways of ornithopods and theropods but rather studied a single trackway, meaning that the only variation they could obtain would be between the individual tracks themselves. He also states that the multivariate analysis “appears to be based on fabricated data and is, therefore, worthless”.  The outlines of these tracks would have also deteriorated over time (Thulborn and Wade, 1984).

Thulborn also takes issue with how Romilio et al. have portrayed Thulborn’s initial interpretation of the site as a prey-pursuit scenario. Thulborn makes the distinction that he has never said it was this particular scenario (except when explicitly speculating), but rather that it was merely a stampede in general, regardless of the identity of the large track maker. Indeed, he argues that the whole premise of the recent paper by Romilio et al. seems to be to declare the larger tracks were in fact made by a large ornithopod, a fact that Thulborn declares is a “separate matter of secondary interest”.

So is the trackway at Lark Quarry evidence of a dinosaur stampede or not? Well, it depends on who you ask at the moment! Further study will no doubt show which of the two parties were closest to being correct. This debate is sure to continue; I’ll keep you all updated when the next developments arise!

References

Romilio A, S. W. Salisbury (2011) A reassessment of large theropod dinosaur tracks from the mid-Cretaceous (late
Albian-Cenomanian) Winton Formation of Lark Quarry, central-western
Queensland, Australia: A case for mistaken identity. Cretaceous research 32: 135-142.

Romilio A, Tucker, R. T. and S. W. Salisbury (2013): Reevaluation of the Lark Quarry dinosaur Tracksite (late Albian–Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede?, Journal of Vertebrate Paleontology, 33:1, 102-120.

Thulborn, R.A. (2013): Lark Quarry revisited: a critique of methods used to identify a large
dinosaurian track-maker in the Winton Formation (Albian–Cenomanian), western Queensland, Australia, Alcheringa: An
Australasian Journal of Palaeontology, DOI:10.1080/03115518.2013.748482

Thulborn, R. A., and M. Wade. 1984. Dinosaur trackways in the Winton
Formation (mid-Cretaceous) of Queensland. Memoirs Queensland
Museum 21:413–517.

The Dromornithids: An Introduction

Australia has been separated from the rest of the world for the majority of the last 65 million years, with complete separation occurring around 30 million years ago. This has given the various forms of life on the continent plenty of time to evolve into their own unique groups. One particularly fascinating and enigmatic group is the family of extinct, giant flightless birds known as the dromornithids.

A reconstruction of Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler. In this image they have been reconstructed as herbivores.
A reconstruction of Dromornis stirtoni by the fantastic palaeo-artist Peter Trusler. In this image they have been reconstructed as herbivores.

Australia today is famous for a group of flightless birds known as the emus; and for a long time the dromornithids were believed to be members of the same group of birds (the ratites). However, in 1998 a study by Murray and Megirian demonstrated that dromornithids are in fact neognathous birds in the Anseriformes. Nonetheless, it remains debatable as to which anseriform group is sister to the dromornithids (Murray & Vickers-Rich 2004, Olson 2005, Agnolin 2007). With a fossil record spanning around 25 million years, dromornithids are known from the late Oligocene through to the late Pleistocene (Field & Boles 1998, Nguyen et al. 2010). An ancient origin for the group is implied by a possible dromornithid foot impression from the early Eocene (approx. 50 million years ago) of Queensland (Vickers-Rich and Molnar 1996). Following an overdue taxonomic revision of the Dromornithidae (Nguyen et al. 2010), the family includes seven accepted species in four genera, with a geographic distribution including every state in Australia. The largest species, Dromornis stirtoni, is estimated to have stood at 3 m tall and weighed up to 500 kg, potentially even larger than the famous elephant bird of Madagascar.

A skeletal reconstruction of Dromornis stirtoni with human for scale showing just how big these animals could have been. Image from www.carnivoraforum.com.
A skeletal reconstruction of Dromornis stirtoni with human for scale showing just how big these animals could have been. Image from http://www.carnivoraforum.com.

There has been some debate as to whether the dromornithids were herbivorous or carnivorous, with features of the skull hinting at the potential for either way of life. Skull material is not known from every species however, and all members of the group may not have shared the same feeding ecology. Gizzard stones have been found in association with dromornithid remains, suggesting they needed the stones to help process plant material, although carnivores such as crocodiles are also known to possess them.

The dromornithids went extinct in the late Pleistocene and it is still unclear what combination of human hunting, landscape changing or climate change was the ultimate cause of their demise.

This is another Peter Trusler reconstruction, this time of the late Pleistocene species Genyornis newtoni. This species could well have encountered the first humans to arrive in Australia, but were they the cause of their extinction?
This is another Peter Trusler reconstruction, this time of the late Pleistocene species Genyornis newtoni. This species could well have encountered the first humans to arrive in Australia, but were they the cause of their extinction? Image from Museum Victoria.

I have also had a personal interest in the dromornithids as myself and Dr. Erich Fitzgerald published a short paper on the Dromornithids last year (Park and Fitzgerald, 2012). In it we detailed the oldest known occurrence of the dromornithids in Victoria, a poorly preserved partial tarsometatarsus (one of the bones in the legs of birds). This bone appeared to represent a new species as it could not be referred to any of the known taxa elsewhere in Australia. Previously, the earliest known dromornithids in Victoria were from the late Pleistocene ( approx. 30,000 years ago) Lancefield Swamp locality, so this find pushes their presence in Victoria back in time considerably. It also cautions against deriving evolutionary patterns solely on the basis of fossils from northern Australia.

The dromornithids as a group still retain a lot of mystery and unanswered questions, and are long overdue for a thorough reanalysis. In fact, one of my colleagues plans to do exactly that over the next few years and I for one look forward to seeing what new details he can reveal about these ‘magnificent Mihirungs’.

References

AGNOLIN, F.L., 2007. Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno medio de
Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales 9, 15–25.

FIELD, J.H. & BOLES, W.E., 1998. Genyornis newtoni and Dromaius novaehollandiae at 30,000 b.p. in central northern New South Wales. Alcheringa 22, 177–188.

MURRAY, P.F. & MEGIRIAN, D., 1998. The skull of dromornithid birds: anatomical evidence for their relationship to Anseriformes. Records of the South Australian Museum 31, 51–97.

MURRAY, P.F. & VICKERS-RICH, P., 2004. Magnificent Mihirungs: the Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press, Bloomington, 410 pp.

NGUYEN, J.M.T., BOLES, W.E. & HAND, S.J., 2010. New material of Barawertornis tedfordi, a dromornithid bird from the Oligo- Miocene of Australia, and its phylogenetic implications. Records of the Australian Museum 62, 45–60.

OLSON, S.L., 2005. Review of Magnificent Mihirungs: the Colossal Flightless Birds of the Australian Dreamtime. The Auk 122, 367–371.

Travis Park & Erich M. G. Fitzgerald (2012): A late Miocene–early Pliocene Mihirung bird (Aves: Dromornithidae) from Victoria, southeast Australia, Alcheringa: An Australasian Journal of Palaeontology, 36:3, 419-422.

VICKERS-RICH, P. & MOLNAR, R.E., 1996. The foot of a bird from the Eocene Redbank Plains Formation of Queensland, Australia. Alcheringa 20, 21–29.