Blogozoic has a new home and it’s at Scilogs.com, an online science blogging network. So whilst it may be goodbye to this site for now, if you want to continue reading my ramblings on the awesomeness of fossils, follow the link below:
Time for another entry in my Australian megafauna A-Z series. We’ve previously looked at Alkwertatherium and Barawertornis. Both these taxa have come from the north of the continent, so I think it’s only fair we give some attention to fossils from the southern end of the continent this time around. This fossil bird species was found in a cave in the south-eastern corner of South Australia. Ladies and Gentlemen, C is for Centropus colossus, better known as the giant coucal.
Coucals are closely related to cuckoos and roadrunners (it’s a real bird not just a cartoon). They are also related to the enigmatic South American bird the hoatzin, although exact relationships are still being debated. This makes the group one of the earlier diverging lineages of modern birds(Edit: thanks to David in the comments and also me going and doing some further reading, coucals are not closely related to the hoatzin. Moral of the story, check your sources! Thanks for the heads up David!). Today in Australia there is one living species of coucal, the pheasant coucal. However, this taxon only lives in the northern forests of Australia and when the fossil species was found in the late seventies, it came as a bit of a surprise to discover this group so far south.
Centropus colossus was described based on an almost complete left humerus by Robert Baird in 1985. Its reduced muscle attachment points on the pectoral crest of the humerus suggest that it was flightless. Modern coucals only fly when disturbed, but the giant coucal was a third larger in size than the pheasant coucal and may therefore have been completely flightless. The presence of the giant coucal in what is today relatively arid country suggests that in the past this region had much more plant cover.
A similar issue has arisen with the discovery of fossil coucal remains from the Thylacoleo Caves in the Nullarbor Plain, south-central Australia. These remains, which are from an undescribed species of coucal were discussed in a talk at CAVEPS 2013 (the conference I recently attended, see here for my quick round up of the week) by Flinders University PhD student Elen Shute (also see this article for further info). The presence of the coucal indicates that this region was thickly covered in vegetation in the past, despite it being desert at present.
The generic name, Centropus, comes from two Latin words; centro, meaning spine and pus, meaning foot. This is referring to the characteristic elongate nail on the hallux of other taxa in the genus. The specific name refers to the fact that this species is larger than other taxa of this genus.
Well that’s C done, D will be a slightly better known animal, if not the best known of all the Australian megafauna. All will be revealed in the near future…
Baird, Robert F., 1985. Avian fossils from Quaternary deposits in ‘Green Waterhole Cave’, south-eastern South Australia. Records of the Australian Museum 37(6): 353–370.
Baird, R.J.F. 1985. Centropus colossus Baird 1985, The Giant Coucal, Pp. 205–208 in Vickers-Rich P., and Van Tets, G.F. (eds), Kadimakara, Extinct Vertebrates of Australia. Princeton University Press: New Jersey. 284 pp.
Clode, D. 2009. Prehistoric giants, the megafauna of Australia. Museum Victoria Nature Series, Melbourne, 72 pp.
Other posts in the Australian Megafauna A-Z series:
It’s been a few weeks since I last posted anything, so I thought it’s about time to remedy that situation. The reason there’s been a lull in activity on the blog (other than the usual PhD and related research) is that all last week I was attending the 14th Conference of Australasian Vertebrate Evolution, Palaeontology and Systematics (better known as CAVEPS) in Adelaide.
The conference is held every two years (the previous meeting was in Perth) and it draws in almost every vertebrate palaeontologist in Australasia, as well as archaeologists, palynologists (fossil pollen people) and several palaeontologists from across the globe. It gives us fossil nerds a chance to catch up, discuss our research, perhaps plan some new collaborations and share a beer or two (or ten). It is exceptionally useful to students like me who have heard, seen or watched these big names in our field but have never met them. We can actually get the chance to put a face to the name and maybe even get to have a chat with them, in addition to meeting fellow students who may we not have even been aware of and make some connections. Palaeontology, like a lot of things in life, is all about who you know!
The conference started off with a series of workshops. There were drawing fossils, fossil casting, radiometric and luminescence dating and phylogenetic methods workshops to choose from. I went to the fossil casting workshop as this was something I had seen done but had never done myself. I had an attempt at casting the tooth row of a wombat which didn’t come out as horribly as I expected!
On the Tuesday the talks began. The first symposium was dedicated to Ruben Arthur Stirton, the man whose 1953 expedition is part of Australian palaeontological legend, and his subsequent researches have had a lasting and profound impact on palaeontology in this part of the world. The conference celebrated the 60th anniversary of the expedition. For the student poster session that evening, myself and Flinders University PhD student Sam Arman tried to quantify Stirton’s impact on Australasian palaeontology by tracing the academic ancestry of the attendees of CAVEPS 2013, finding that 26% of them could trace their lineage back to him. This poster stemmed from an earlier blog post of mine (see here), where I traced my own academic ancestry (Stirton is my great-great-great academic grandfather) and it was a very cool project to do that seemed to go down well with almost everyone at the conference.
Wednesday’s talks were very interesting, the main theme being phylogenetics. Colleagues of mine who aren’t particularly interested in the subject even found the talks interesting, so the speakers must have been doing something right! Wednesday night saw the conference auction, which saw several of my hard earned dollars depart from my wallet in exchange for a couple of books and some papers I look forward to reading.
I missed Thursday morning’s lectures due to being just a tad hungover from the night before (I was at a conference after all), but I heard from people who were there that they were very good! After enjoying the afternoon talks it was time for the conference dinner, where we were treated to a performance from Professor Flint and the Flintettes, an experience not to be missed! You can see an example of their work in the video below.
Friday was the last day of the conference, and also the day of my very own talk. This meant I got the unfortunate pleasure of having to wait all week before being able to finally relax! I presented on some fossil penguin research that I will hopefully be submitting soon. That night we relaxed with some dinner and a few celebratory drinks before departing off on the long drive back to Melbourne on Saturday morning. A great week; and I look forward to the next CAVEPS, which will apparently be held in Alice Springs of all places! Another road trip to look forward to then…
A massive thank you to the Flinders crew for putting on such a great conference, fantastic work!
When most people hear the word Mesozoic, they immediately think of dinosaurs. That’s fair enough, the “terrible lizards” have had the most research and media attention devoted to them out of all the Mesozoic vertebrate groups. But that doesn’t mean that other critters that were roaming the land and sea during that era weren’t as cool or as interesting as the dinosaurs. One particularly striking example of this is the crocodiles, or more precisely the broader group to which they belong, the crocodylomorphs. These, in turn, belong to an even broader group known as the crurotarsans, so named due to a specialized articulation between their fibula and tarsus (ankle bones). Crurotarsans were hit particularly hard in the end-Triassic extinction event 201 Ma; the only surviving members of the croup were those wily crocodylomorphs.
The crocodilians we are familiar with today are all part of the same group (Neosuchia) which first appear in the Late Cretaceous and are today all more or less the same in their morphology and lifestyle. In the Mesozoic however, things could not have been more different. These crocodylomorphs were far more diverse occupying ecological niches that saw dog-like and even herbivorous forms running around on land whilst in the seas there were obligate marine forms that were almost like sharks or killer whales. These ancient crocodiles would have been truly spectacular to see alive, their fossils are certainly impressive enough! Whilst this disparity (this term is used to distinguish morphological diversity i.e. lots of different body plans from taxonomic diversity i.e. lots of different species in sheer numbers, but who may all have similar body plans) has been studied in terms of variation in cranial (skull) cladistic characters it has yet to be quantified using morphological and biomechanical variation of the mandible (jawbone). That has all changed with the publication of a new (open access) paper in the journal Proceedings of the Royal Society B (Biological Sciences).
The team, led by Bristol University PhD student Tom Stubbs have examined the diversification of Mesozoic crocodylomorph feeding ecologies by quantifying morphological and biomechanical disparity in the mandible. As Tom explains: “The ancestors of today’s crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts. They were very different creatures to the ones we are familiar with today, much more diverse and, as this research shows, their ability to adapt was quite remarkable. Their evolution and anatomical variation during the Mesozoic Era was exceptional. They evolved lifestyles and feeding ecologies unlike anything seen today.”
A whopping one hundred and seven mandibles were examined for the study, giving them examples of the complete spectrum of shapes and sizes the Mesozoic crocodylomorphs occupied. Why the mandible I hear you ask? There are several reasons for this: one is that the mandible is particularly well suited to the types of analyses the team were planning to conduct; secondly, as the mandible plays such a fundamental role in the animal’s life, any change in morphology will likely represent an evolutionary adaptation; and lastly, as the mandible is made up of fewer parts than the complex skull, it is more likely to preserve complete, giving researchers a larger sample size.
So what did they find? Well, there were several interesting results. Firstly, Late Triassic taxa had high disparity both in terms of their morphology and their biomechanics. This shows that crurotarsans living at this time occupied many ecological niches and employed many different feeding ecologies. Secondly, morphological disparity declined following the Late Triassic extinction event, and remained low throughout the Jurassic. Crocodylomorphs were predominantly marine during this period, the end Triassic extinction event and (potentially also) the rise of the dinosaurs preventing them from remaining successful on land. However the breakup of the supercontinent Pangaea caused the formation of new epicontinental seas where one group of crocodylomorphs in particular, the thalattosuchians, thrived. The hydrodynamic demands of living in water meant that most taxa had a similarly shaped, elongated and dorsoventrally flattened skull morphology.
The third key finding concerns the final Mesozoic period, the Cretaceous. During this period crocodylomorphs radiated into the terrestrial realm once again. With this radiation came a whole host of new morphological disparity, with taxa occupying ecological niches that had remained vacant since the Late Triassic. Interestingly, despite this proliferation of morphological disparity, biomechanical disparity did not increase. The authors proffer some potential theories as to why this may have been the case: the lifting of hydrodynamic constraints meant they were now free to evolve these new morphologies; alternatively they have evolved new biomechanical disparity in other anatomical regions, releasing the mandible from selective pressures, making mandibular evolution less significant.
This excellent study reveals that morphological and biomechanical disparity are not as entwined as you would intuitively think, but have a rather more complex relationship. Factors such as diet and habitat affect these two measures of disparity differently. Co-author in the study, Dr. Stephanie Pierce, from the Royal Veterinary College, sums it up: “Our results show that the ability to exploit a variety of different food resources and habitats, by evolving many different jaw shapes, was crucial to recovering from the end-Triassic extinction and most likely contributed to the success of Mesozoic crocodiles living in the shadow of the dinosaurs.”
A really cool paper indeed, not least because there are several parallels with what I’m hoping to do in my PhD projectwith fossil cetaceans (so if any of you had any ideas about doing that, I’ve got dibs!), in addition to some new ideas reading this paper has given me. I reckon the new Jurassic World movie would benefit with having a few crocodylomorphs in it. I’m sure you lot wouldn’t complain either.
Quotations were taken from the EurekAlert! Media release.
Tom Stubbs, Stephanie Pierce, Emily Rayfield and Phil Anderson (2013) Morphological and biomechanical disparity of crocodile-line archosaurs following the end-Triassic extinction. Proceedings of the Royal Society B: Biological Sciences 280: 20131940. http://dx.doi.org/10.1098/rspb.2013.1940
Well, time certainly flies when you’re busy and before you know it, it’s been almost a month since you’ve last written a blog post. At least that’s what has just happened to me! I’ve been busy doing research on fossil whales, fossil penguins, talking fossil penguins at Museum Victoria’s latest SmartBar, giving a talk on Australian fossil seabirds as well as preparing and submitting abstracts for an upcoming conference, whew! But I haven’t been blogging and bringing you, dear readers, new and cool fossil discoveries. So let’s rectify that situation then shall we?
As you may have guessed from the title above, this post is about fossil dugongs, or more precisely, the lack of them in the Indopacific region. Whilst today the region is the centre of sirenian abundance and fossils are known from areas such as Madagascar, Somalia, India, Sri Lanka and Indonesia, fossil evidence from the Indopacific has been lacking with the only reported finds being a partial mandible from the Pliocene of South Australia, a partial rib from the Miocene-Pliocene boundary of Victoria and fossils of the extant Dugong dugon from the Quaternary of Papua New Guinea and Holocene of southeast Australia. There is no clear explanation for the scarcity of dugong fossils in the Indopacific region as the find from South Australia shows they were present in the area in the past. Furthermore, there are plenty of available outcrops of sediments of the correct age, the sediments also indicate the climate would have been suitable for dugongs to be present and the high densities of sirenian bones make them favourable for preservation. Therefore any new finds would be crucial to gaining a more detailed understanding of sirenian evolution in the Indopacific.
One such find was made but it was actually 30 years ago, with the fossils not being studied until only recently and published in the Journal of Vertebrate Paleontology this July by Erich Fitzgerald (who also happens to be one of my PhD supervisors) and colleagues from the Smithsonian, Howard University College of Medicine and Flinders University. The recovery of the fossils (consisting of three posterior vertebrae, one anterior caudal vertebra and seven partial ribs) is a story in itself. The fossils were found in a cave in the remote Hindenburg Range of the New Guinea Highlands, Papua New Guinea, but when the fossils were being recovered the cave suddenly flooded meaning the crew had to make a quick exit leaving some fossil material behind!
The fossils date to between 11.8–17.5 Ma, giving a minimum age of just before 12 Ma for sirenians being present in Australasian coastal marine ecosystems, and by implication their primary food source: seagrasses. As Dr. Fitzgerald explains, “Modern-day dugongs are major consumers of sea-grass, and, by doing so, have a tremendous impact on the structure of the ecosystem,” said Dr Fitzgerald. “They participate in a delicate balancing act: their feeding allows diversity in sea-grass and animal species that would otherwise be lacking. Previously, it was thought that sea cows were fairly new arrivals in Australasia, and that their relationship with sea-grass ecosystems here was a recent event. This new evidence suggests sea cows have been an important component of Australasia’s marine ecosystems for at least 12 million years and that their role in the long-term health of these environments may be substantial.”
So whilst we are still in the dark about an awful lot of the history of sirenians in Australasia, this new find does shed a little light their evolution and now we know that they were there around 12 Ma, researchers can start looking in shallow marine sediments of similar age to find the next illuminating discovery.
Dr. Fitzgerald’s comments are taken from the Museum Victoria media release.
Erich M. G. Fitzgerald, Jorge Velez-Juarbe & Roderick T. Wells (2013) Miocene sea cow (Sirenia) from Papua New Guinea sheds light on sirenian evolution in the Indo-Pacific. Journal of Vertebrate Paleontology 33: 956–963.
Most people would class the Cenozoic (the period of time spanning from 66 Ma to the present) as the Age of Mammals. Certainly the diversity of mammals exploded and the majority of modern groups evolved after the demise of the non-avian dinosaurs at the end of the Cretaceous. However, what a lot of people don’t realise when they think about mammals is that they have been around for a lot longer than 66 Ma. The oldest known definite mammals date to around 165 Ma but the actual origins of the group would have been some time previous to that but remains uncertain, primarily due to the fact that most early mammals are known only from isolated teeth.
Two remarkable new finds, both from the Middle – Late Jurassic Tiaojishan Formation in the Hebei Province of China, have provided new food for thought in this debate, whilst not necessarily providing any definitive answers. The two new species, described in separate papers in last week’s issue of Nature preserve not only teeth, but skull material and post-cranial elements such as vertebrae, limb bones and even fur. Both species belong to an extinct group of mammals known as the haramiyids.
The first new species, Arboroharamiya jenkinsi, described by Zheng et al., was an omnivore or herbivore that had several adaptations for living in trees, such as elongated digits. The morphology of its caudal (tail) vertebrae also hints at it possessing a prehensile tail. It has been dated to 160 Ma.
The second new species, Megaconus mammmaliaformis, described by Zhou et al., was herbivore that lived on the ground, with its morphology indicating it had an ambulatory (walking) gait similar to that of a modern day armadillo. Megaconus was more primitive than Arboroharamiya and is also slightly older, dating to around 164 – 165 Ma.
Now, so far so good. But where these two studies provide conflicting opinions about the early mammal evolution is in their phylogenetic analyses. The Zheng et al. paper groups Arboroharamiya and all other haramiyids as the sister group to the multituberculates within Mammalia. This puts the origin of mammals at around 215 Ma, in the Late Triassic, much older than most palaeontologists would estimate, but in agreement with molecular estimates. The Zhou et al. paper on the other hand, placed Megaconus and all other haramiyids outside of Mammalia, meaning they are not closely related to multituberculates and also estimates the origin of mammals at around 180 Ma, a figure more in line with palaeontologists expectations given what fossils are currently known.
So, which tree is the correct one? Well, neither probably. There are several factors why this will most likely turn out to be the case. One is that these two phylogenies don’t contain the other new species, a potential next move for the authors of these two papers is to combine their data a produce a phylogeny with both new taxa to see where the haramiyids place. Another is that although these fossils are relatively well preserved, there is still a lot of anatomical and morphological data missing from them, with Arboroharamiya possessing less than a quarter of the 436 characters used in the Zheng et al. study and Megaconus possessing less than half of the 475 characters used in the Zhou et al. study. A third factor is that whilst these two new taxa might be relatively well preserved, the majority of other early mammal taxa are poorly preserved or are only known from teeth. More fossils of the quality of these two new specimens would help resolve the origin of the mammals.
Finally, there is also a little lesson to be learnt here about cladistics, the method by which phylogenies are now generated. Whilst this method is undoubtedly the best and most powerful tool we possess for distinguishing relationships between species at present, there are many different cladistic techniques that scientists can employ, and it will often depend which technique is used as to which phylogeny they end up obtaining. So don’t always accept the phylogenetic position of taxa just because there’s a phylogeny showing it that way, try to look at what methods they’ve used to obtain their results. Remember, good scientists will question everything!
Cifelli, R. L. & Davis, B. M. 2013. Jurassic fossils and mammalian antiquity. Nature 500, 160–161.
Zheng, X., Bi, S., Wang, X. & Meng, J. 2013. A new arboreal haramiyid shows the diversity of crown mammals in the Jurassic period. Nature 500, 199–202.
Zhou, C.-F., Wu, S., Martin, T. & Luo, Z.-X. 2013. A Jurassic mammaliaform and the earliest mammalian evolutionary adaptations. Nature 500, 163–167.
Just over a month ago I started a new series here on Blogozoic, the Australian megafauna A-Z, in order to show people the weird and wonderful products of the evolutionary and geographic isolation of Australia. In the first post of the series I wrote about Alkwertatherium, a large marsupial that roamed the Northern Territory in the Late Miocene. Now we move onto the letter B and this time the animal, somewhat appropriately, is a bird.
The group to which this bird belongs is the Dromornithids. Those of you with very good memories may remember I wrote a post giving an introduction to these giant, extinct, flightless birds back in February (click here to read it). This time however I will focus on one species of dromornithid in particular, the species in question is Barawertornis tedfordi.
Barawertornis tedfordi isamong the oldest known dromornithids, dating to the Late Oligocene to Early Miocene. Its generic name means ‘ground bird’ and it specific name is in honour of the vertebrate palaentologist Richard Tedford, who was one of the first people to collect dromornithid remains in Australia. The holotype, a partial left femur, was described along with other partial hind limb fragments and a dorsal vertebra by Vickers-Rich (1979). Little more was discovered of the taxon until 2010, when Nguyen and colleagues described multiple partial femora, tibiotarsi and tarsometatarsi from the Riversleigh World Heritage Area in north-western Queensland. This new material allowed the researchers to better understand the relationship of B. tedfordi to other dromornithids as well as make some inferences about how this animal may have lived.
As well as being one of the oldest dromornithid species, B. tedfordi is also the smallest known species of dromornithid and would have been similar in size to the extant southern cassowary (Casuarius casuarius), with an estimated mass of around 45 – 65 kg (Nguyen et al. 2010). Furthermore, the relative proportions of the hind limb bones in are also most similar to that of the southern cassowary, suggesting that it may have been capable of similar cursorial (walking and running) abilities. With Australia being mainly covered by forest during the Early Miocene it makes sense that B. tedfordi would have converged upon a similar physique to the cassowary that today still roams the forests of north-eastern Australia and Papua New Guinea.
The phylogenetic position of B. tedfordi is also still not certain. Previous analyses (e.g. Murray & Vickers-Rich 2004) and the strict consensus of the analysis by Nguyen et al. (2010) found that B. tedfordi was the sister taxon to all other dromornithids. However, Nguyen et al. (2010) also found weak support for B. tedfordi forming a clade with Ilbandornis sp., I. woodburnei, Dromornis planei, and D. stirtoni. The fragmentary nature of most dromornithid material however prevents more definitive statements being made about their phylogenetic relationships at present.
So that’s B done, I’ll leave it up to you clever people to figure out what letter is coming next. Stay tuned…
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.
Other posts in the Australian Megafauna A-Z series: