Sunday, 22 December 2013

Tyrannosaurs at Christmas




Despite SVP being understandably mammal-centric this year, there was still plenty of dinosaur related presentations and posters to keep us all happy. As usual, I was focussing mainly on marine reptiles (not a lot this year unfortunately) and theropod research – particularly tyrannosaurids and, in this particular instance, there were a few really interesting pieces of research on show.
Regular readers are aware that I have often discussed the importance of the tyrannosaurid Daspletosaurus and how continuing research into this animal is important – especially when it comes to tyrannosaurine evolution and the dispersal of Tyrannosauridae throughout North America. We have known for some time now there are multiple species of Daspletosaurus and here, for the first time, Tetsuto Miyashita, of the University of Alberta, and colleagues presented their research into one of these new tyrannosaurids.
The new taxon is represented by multiple skulls and skeletons and displays several characters that are distinctive from Daspletosaurus torosus. These include features in the premaxilla, nasal, postorbital boss, and lacrimal (amongst others). Remains are found in both the Dinosaur Park Formation and the temporaneous uppermost Oldman Formation and are thus more recent than D. torosus.
The authors’ phylogenetic analysis reveals that this taxon, as well as Daspletosaurus sp. from the Two Medicine Formation, forms a clade which is comprised of tyrannosaurine tyrannosaurids that are more derived than those from Campanian deposits in Utah and probably New Mexico. Interestingly, this analysis also recovered Bistahieversor as a tyrannosaurid which is just what the comprehensive analysis recently documented in the Lythronax paper (Loewen et al 2013) also found.
Here it is interesting that the authors favour Daspletosaurus as being derived with both Tarbosaurus and Tyrannosaurus but Loewen et al regard Daspletosaurus as a basal northern clade and separate from the southern Laramidian radiation of tyrannosaurids. They favour a southern distribution for more derived tyrannosaurids and suggest that both Tyrannosaurus and the Asian Tarbosaurus evolved from this dispersal event in the south.
This is intriguing because there are obvious differences between these two analyses and it raises yet more questions than there are answers. Personally, I remain open minded about tyrannosaurid dispersal events and, make no mistake, there were probably several. But perhaps there is now more evidence about Daspletosaurus being “northern” and it comes in the form of another unexpected new tyrannosaurid announced at SVP.
Anthony Fiorillo and Ron Tykoski, both of the Perot Museum of Nature & Science in Dallas, presented their research on skeletal remains of large theropods in the Upper Cretaceous Prince Creek Formation of Alaska. The Prince Creek crops out along the bluffs of the Colville River and the sedimentology reveals deposits that were laid down in a wet/dry seasonal environment. There are several sites of which one, the Kikak-Tegoseak Quarry, has yielded some extremely interesting elements from a tyrannosaurid.
One of these, DMNH 21461, is a skull roof displaying a bifurcated sagittal crest and would seem to indicate a total skull length of around 0.6 metres. Other elements include a partial dentary and are indicative of a derived tyrannosaurine and are quite diagnostic indicating that a new taxon is involved. The authors are naturally enough a little wary at the moment about confirming or naming the new taxon and, when questioned about the height of the sagittal crest by Thomas Carr, declined to answer in public. That is fair enough but my observations of the fossils on display, and the sagittal crest in particular, suggest that this may yet be another species of Daspletosaurus. And there is more.
The Liscomb Bonebed, another site in the Prince Creek, has also yielded tyrannosaurid elements and these display an unusual condition for their size. These include specimens DMNH 2012-25-31 (a neural arch), DMNH 2012-25-30 (a partial radius) and DMNH 2012-22-20 (a pedal phalanx) and  their overall morphology is indicative that they represent an adult tyrannosaurid – but this particular individual is only about 40% the size of what a conventional large adult tyrannosaurid would be.
This should actually not be a surprise considering the conditions that would have been endured in the palaeoenvironment of northern Alaska back in the Late Cretaceous and dwarfism would have been a logical response when resources are limited. As research progresses it will be interesting to know how these tyrannosaurids relate to each other and, as I mused earlier, how they will further enlighten our knowledge of the tyrannosaurid radiation throughout the Late Cretaceous.
Thomas Carr’s contribution to SVP this year was a poster looking at the sister group relationship between Daspletosaurus and Tyrannosaurus. Just in case you are unaware, Carr is still working on a quite significant monograph on Daspletosaurus which was, when we were chatting at SVP, over 1000 pages long – a significant contribution. So it was not surprising to see this poster featuring his research into testing the evolutionary lineage of these tyrannosaurids and whether a case for anagenesis can be made.
A comprehensive cladistic analysis was undertaken to compare both phylogenetic and ontogentic sequences and patterns. Unsurprisingly, perhaps, there are several factors that are suggestive of an anagenetic tyrannosaurine lineage but, equally, there is that question of the dispersal of Tyrannosaurinae in the first place. As Carr points out, Tyrannosaurus is phylogenetically removed from Laramidian species by some Asian taxa in the first place and the fact that, as I have already alluded to, there were several dispersal events between Asia and North America and then the case for anagenesis in Laramidian tyrannosaurines becomes very complex indeed .
Interesting again is how this analysis tends to support that of Myashita et al from earlier and contrasts with that of Loewen et al which favours a southern radiation for Laramidian tyrannosaurines. The origins of these formidable tyrannosaurids looks set to be undetermined for some time to come.
Finally, and moving away from tyrannosaurids, Joseph Sertich, of the Denver Museum of Science & Nature, and his colleagues unveiled another giant theropod but this time in the form of a primitive abelisaurid. This specimen has proven to be remarkably popular and there were lots of extremely interested workers at SVP and, again, in the palaeoworld since the meeting.
The specimens derive from the Lapurr sandstone in the Turkana Basin of Kenya and are rocks of Maastrichtian age. Elements include some from the skull and those from both axial and appendicular skeleton. Unfortunately, a lot of this material is scrappy and poorly preserved but is diagnostic enough to be able to refer these specimens to the Abelisauridae.
However, the size of the animal is readily evident and is confidently predicted to be in the region of eleven metres long – maybe more but there appears to be no significant cranial ornamentation on this taxa unlike other abelisaurids. This large theropod was part  of a diverse fauna that is now coming to life as more fossils are found and include sauropods, ornithopods, theropods, pterosaurs and crocodiles and, despite most of the fossils that have so far been recovered being scrappy, there is every likelihood of yet more surprises to come from this intriguing part of Africa.
Footnote
Well it is the time of year when the season of goodwill should be the order of the day. It has been a very busy year for me and, as a result, I have not been able to post as often as I would like but, rest assured, I will always endeavour to post as often as I can. Between the amount of work I have and also looking after the interests of the group (which is important for all of us) time is of a premium just now - but we will get there in the end.
Thanks for all your support over the last year and now it just remains for me to say that, to those of you who celebrate it, I hope you all have a happy and peaceful Christmas. Enjoy!  

References

Carr, T. 2013. Using ontogeny and phylogeny to test hypotheses of anagenesis in the vertebrate fossil record: a case study of the sister group relationship between Daspletosaurus and Tyrannosaurus (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp101.
Fiorillo, A & Tykoski, R. 2013. Distribution and polar palaeoenvironments of large theropod skeletal remains from the Prince Creek Formation (Early-Late Maastrichtian) of Northern Alaska. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp127.
Loewen MA, Irmis RB, Sertich JJW, Currie PJ, Sampson SD (2013) Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE 8(11): e79420. doi:10.1371/journal.pone.0079420
 Miyashita, T., Currie, P. & Paulina Carabajal, A. 2013 A new species of Daspletosaurus (Theropoda: Tyrannosauridae) from the Campanian of southern Alberta represented by a growth series of well-preserved skulls and skeletons. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp178.
Sertich, J., O’Connor, P., Seiffert, E. & Manthi, F. 2013. A giant abelisaurid theropod from the latest Cretaceous of Northern Turkana, Kenya. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp211.

Wednesday, 4 December 2013

Guest Post: A Night With a Legend


 
Ever wonder what it would be like to spend some time with probably the worlds’ greatest living naturalist, Sir David Attenborough? I was delighted when my friend and colleague Mark Graham, preparator at the Natural History Museum in London, offered up this wonderful post describing his time with Sir David and a film crew as they filmed various sequences for the upcoming documentary,  David Attenborough’s Natural History Museum Alive 3D.
The post brings to life what it is like for a large institution like the NHM to cope with the rigors of a fully loaded professional film crew whilst all the time looking out for the specimens in your care and, of course, being able to converse with Sir David. I know I speak for so many in saying that I would absolutely love to be able to do that one day and I am incredibly jealous!
But this is the next best thing so read on and enjoy. Please note that all images are courtesy of the Natural History Museum and are used WITH PERMISSION.
 
A Night with a Legend...  
 
16 & 17th August 2013
 
I jumped at the chance to be present in the lab for a filming session by Sir David Attenborough ( surely a candidate as 'the greatest living Englishman'), even though it meant working right through Friday night and into Saturday morning. Arianne Burnucci, my conservator colleague, was also excited to meet the great naturalist and, although only we two wanted to  be on hand throughout, everyone in the Conservation Centre got involved and spent a great deal of time during the week in clearing up the lab in readiness for the film crew.
 This was no mean feat as the Conservation Centre services the needs of  the entire museum, following a restructuring which saw its remit change from fossil preparation and conservation as  the 'Palaeontology Conservation Unit' to that of  a facilities function for all the earth and life sciences, including for example, mineralogical,  zoological and botanical specimens. And the facility, which is a busy and well-used space, is showing its age, so getting it to look fit for state of the art 3D filming by the world's favourite naturalist (and everyone's favourite uncle) took up an enormous amount of everyone's time.
 
Before the floor could be deep cleaned by an external contractor (which itself had to be spread over two early start mornings) a mountain of plastezote (support foam) and cortex (corrugated card) offcuts had to be graded, stored or disposed of and a multitude of tools and other paraphernalia put away out of sight in various cabinets, drawers and adjoining offices. Work benches were stripped of their old worn paper covers and fresh new ones cut and taped into place. Fume cupboards, grinding booths , cutting tables and sinks were cleared and then attention turned to the various specimens around the lab, as each would need to be protected from potential damage during the organised mayhem that  results from a fully kitted out film crew going about its business.
 
These included a full sized stuffed lioness, a stuffed adult stag, hyaena and a deer - not to mention both marine reptile and dinosaur fossils as well as botanical specimens. And there was the small matter of bringing an adult sauropod femur up from the dinosaur collection in the sub-basement to the lab, which took 3 people and a hydraulic forklift.
 
Apart from one specific specimen (which I will not disclose as it would spoil everyone's fun), the selection of fossils for 'dressing the set' was left to me. The production company wanted a selection of skulls, dinosaur bones, trilobites and other interesting three dimensional fossils and so, with the help of curatorial colleagues, I plundered the collections for some of the best and most iconic specimens.


Bones awaiting preparation.

 
The film crew and their attendant entourage (amazingly around 40 people) turned up in their lorries around 7pm at our loading bay and traipsed through the lab and upstairs for a briefing. Arianne accompanied them and the lab was suddenly quiet again, when in walked Sir David and the production company director. It was a wonderful moment when I introduced myself to them and made them comfortable in one of the lab offices, which served as David's private space for the duration (I asked his PA and he prefers to be addressed as David - not 'Sir David', which didn't surprise me). He is very informal and easy going around everyone, which made for a great atmosphere straight off the bat.
 
After a little while, as the crew were setting up the cameras and deciding where various fossils were to be placed, I was asked if I could give David a look around the collections as he loves to see behind the scenes. And so we wandered off - (the godfather of natural history, whose programmes, DVDs and books have enraptured me for all my adult life, and me), down to the dinosaur collection - accompanied by a cameraman who was shooting 'making of the programme' footage.
 
But what to show someone who has been everywhere around the world and has seen everything in the natural world? I decided to re-acquaint him with two specimens that I knew he had an association with; a sauropod he helped collect on a field trip during the 1980s, Baryonyx, which he had seen during its preparation and Spinops, which I had prepared 5 years previously. And, just like all of us who work with dinosaurs, he was completely absorbed. Then, as he had mentioned an incident in our acid lab many years ago, when, following a series of time- lapse photographs, he had dropped his camera into a tank of acid and ruined it, I took him there to see some resin transfer fossil fishes that I am currently acid preparing.
 
After showing him back to one of the offices where he could relax between filming, I found myself much in demand from the crew members - could this bench be moved out of shot, could that specimen be angled differently, would it be ok if we described what you do in these terms, could I find some colourful equipment to put on display, could the air extractors be switched off, could the lab doors be set open, could the hydraulic table be lifted to show the large specimen to best effect - so on and so forth. But it was great fun and, more importantly they all treated the specimens with absolute respect, which was my main concern and they went about their business carefully and very professionally, so I felt confident that nothing untoward was likely to happen.
 
The first shot was set up and out came David to take his position by the main specimen and prop (I won't say what they were as I don't want to spoil the surprise for anyone ahead of broadcasting). 'Clap' went the clapper board and suddenly, in a nano-second, there was that so familiar voice, part science buff, part actor, all enthusiasm. I was grinning from ear to ear - entranced and not quite believing that here I was involved in helping one of my heroes. After three or four takes the crew were satisfied, and David got up and went back to the office, with his PA 'guarding' the doorway while he read the script and notes.
 
The crew went back into overdrive, moving all the camera tracks, lighting and sound gear to the next part of the lab. Several 'set pieces' were organised to enhance the special effects and, for the next shoot, David showed off his acting prowess - and he had everyone laughing in the process.

Specimens laid out for filming
While all this was going on, other crew members, who had set up a super-high definition camera in one of the collection areas, requested the first of the iconic dinosaur specimens that I had selected with them earlier. So, down I went with Ari and a trolley to the collections and out came the massive left dentary of T. rex, which we positioned carefully under the slow whirring camera that took a full 20 minutes to scan the specimen. One of the crew, a young guy, was absolutely in awe of the great jawbone with its array of killer teeth "it's the first time I've got a real sense of the timescales involved with these fossils" he said to me - he was almost dumbstruck to be standing inches away from the wrong end of the Tyrant King - it really affected him.
 
At some point (just before midnight I think) the catering crew announced that a curry was ready, and everyone went up to the common room to eat. We all sat round and David discussed the lives of some of the Victorian scientists associated with the museum and all manner of things palaeo.
 
Surprisingly, I was asked by the producer to be interviewed and the roving cameraman, who was taking the 'making of the film and behind the scenes' footage spent about 20 minutes asking me  questions about the museum and the filming experience - I hope that at least a few seconds make the final edit for posterity!
 
Next up for the hi-definition camera treatment was the Baryonyx claw - more open mouths from the crew...
 
The filming took 12 hours and, at the end of it all, David was understandably looking a bit tired and was ready to get away.  I felt a bit embarrassed, but he had earlier agreed to sign a couple of books for me and I also got a photo taken with him.
 
I'm happy to say that the old adage 'you should never meet your heroes' didn't hold true in this instance - he was as interesting and charming as I knew he would be and it was one of those very special experiences that I'll always remember and cherish.
 
Then, the crew quickly packed up all their kit, made a point of thanking us and made their exits and Ari and I set about placing the specimens back in their cabinets, tidying up and securing the lab before we left on Saturday morning.
Note 
David Attenborough’s Natural History Museum Alive 3D premiers on New Year's Day on Sky 1, Sky 1 HD and Sky 3D.
 
video


 
Mark and the great man himself.

 

Wednesday, 27 November 2013

The Bizarre Deinocheirus.....


 
Deinocheirus mirificus – a dinosaur that we are all familiar with and now, thanks to the disclosures at this year’s SVP meeting in Los Angeles, an animal that we are now much more able to visualise in life. I first learnt about Deinocheirus as a kid and I was mystified by the huge arms of the type specimen. For me, at the time, it represented the ultimate theropod but for palaeontologists it was inconceivable that the rest of the animal could be simply scaled up from the huge arms as you might restore a conventional theropod - it was just too big.
There was even a train of thought that Deinocheirus was a kind of giant reptilian sloth using its arms to pull down vegetation. Eventually, as the science of phylogenetics came to the fore, we got nearer to the truth and Deinocheirus was generally regarded as a basal ornithomimosaur but even then there were still discussions about whether this diagnosis was accurate and a few of us were always secretly hoping that it would indeed turn out to be some kind of super predator. One thing that everybody agreed on – we needed more fossils.
Eventually they were found and Yuong-Nam Lee, of the Korean Institute of Geoscience & Mineral Resources, and colleagues presented their findings to a large and expectant audience. Two specimens were displayed – MPC-D 100/127 and MPC-D 100/128 – recovered from the Upper Cretaceous Nemegt Formation at Altan Uul IV and BuginTsav in 2006 and 2009 respectively. Much of the missing post cranial material that had eluded fossil hunters of the years was recovered although one of the specimens had already been illegally plundered which is both disturbing and unfortunate to say the least.
Of the material that was displayed there were a series of cervical vertebrae in full articulation complete with the atlas vertebra (C3 – C10) which are very ornithomimosaur-like and a similar series of dorsal vertebrae which display tall anterodorsally facing and highly pneumatic neural spines. The dorsal ribs are fairly straight and are indicative of a narrow body.  The sacral vertebrae (S1 – S6) also demonstrate tall neural spines and are fused (except for sacrals S1 and S6) and form a strong plate of bone.  This appears to demonstrate the presence of a hump in Deinocheirus akin to those found in other dinosaurs and is somewhat unexpected in this taxon.
There is also a series of caudal vertebrae preserved whilst the ilium is quite distinct and displays a raised anterior dorsal margin. The pubic region, as a whole, is strongly developed. The femur is well developed, robust and longer than the tibia and is clearly both unique and diagnostic of Deinocheirus.  Also of interest is the presence of gastroliths in the gastralia of MPC-D 100/127 (well over a 1000) and this is indicative that the animal was probably herbivorous.
Despite the fact that there is still no skull material for Deinocheirus, this new post cranial material looks wonderfully preserved and has allowed us to confirm that Deinocheirus is indeed a basal ornithomimosaur and is, therefore, a stunning vindication and endorsement of phylogenetics – a real triumph. The real surprise, however, is the visual reconstruction of the animal that drew audible gasps from the enthralled audience. There are a number of reconstructions already circulating but, in my opinion, not one of these has got the proportions or appearance of the animal correct.
I do not intend to add further fuel to the fire, and I am certainly not talented enough to produce my own image but if I said to you that Deinocheirus looks like a cross between an ornithomimid, a therizinosaur and Concavenator then you will appreciate just what a bizarre animal this really is. We all look forward to the paper which, at time of writing, still unfortunately appears to be some way off.
Next up - tyrannosaurids but before that I will be publishing a guest post which is a terrific article about the filming at the Natural History Museum in London for David Attenborough’s new programme, David Attenborough’s Natural History Museum Alive 3D, to be broadcast on New Year’s Day so watch out for this one.
Reference
Lee, Y., Barsbold, R., Currie, P., Kobayashi, Y. & Lee, H. 2013. New specimens of Deinocheirus mirificus from the Late Cretaceous of Mongolia.  Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2013, pp161.

Wednesday, 6 November 2013

SVP Reflections


As many of you are aware, the Society of Vertebrate Palaeontology’s latest annual meeting has recently ended in Los Angeles. This was one of the biggest and most well attended yet with early estimates during the meeting predicting an attendance of over 1500 delegates from all over the world. I was fortunate enough to be able to attend again this year and I was part of a large contingent from the UK who made the trip.
I still consider it a privilege to be able to attend this meeting and I am very aware that many people find the cost prohibitive and are unable to make it and so I consider myself very lucky. It was also the last meeting in the US until 2015 since next year’s meeting is to be held in Berlin and I knew that there is a strong likelihood that some of my friends and colleagues from North America were unlikely to make 2014 for the very same reasons of cost.
This was why I made the sacrifices necessary to attend this years’ meeting since next year’s meeting will be a relatively short trip for us by comparison – and without the jet lag! The Westin Bonaventure Hotel and Suites made an ideal venue in my opinion except that it took a long time to get to grips with the multitude of nooks and crannies of the hotel and there were still many of us taking wrong turns, getting off at the wrong floor and using the wrong escalator even at the end of the meeting.
The session halls appeared ideal and there did not appear to be any technical glitches that I was aware of. The exhibitors were not so lucky and found their space restricted compared to recent meetings but, small as the spaces were, they were still very expensive for the vendors to procure. I felt particularly sorry for the guy from Skulls Unlimited who, already constricted by the designated space, also had a support stanchion to contend with – he looked as if he was displaying out of a cupboard.
Poster space appeared good although it did get rather crowded during the author present session but this is a natural tendency at SVP and all the sessions were well attended and good humoured. Coffee was present leading up to the morning sessions and at the morning interval but not during the afternoon session and I always think that is a little strange. Water was always readily available.
The welcome reception at the Los Angeles County Museum of Natural History was an excellent event. Coaches were laid on for delegates but the wait for these was somewhat long and it appeared to me that the organisers may have underestimated the demand. Some of us went by taxi in the end and shared the cost and this was a very cost effective way of getting to the museum.
The reception had no such issues and I was impressed by the organisation, and the food provided was both plentiful and of reasonable quality. The museum itself is stunning and a credit to the city. It will take an article to describe the museum and some of the exhibits but the T. rex growth series, which is the central display in the main dinosaur hall, is superb and many of us took copious amounts of photographs of many of the specimens for reference.

 
The silent and live auctions were good fun although I missed the silent auction on this occasion due to a prior dinner engagement. I arrived just as people were paying for their successful bids but everybody appeared well pleased with their goods. The live auction was the usual raucous affair with the theme for this year’s auctioneer’s dress code, unsurprisingly, being Halloween based. There was lots of money raised with the highlight being a replica of the crocodile Stegochampsa, donated by Triebold Palaeontology, going for just over $4000.
The awards banquet went off really well with several awards being handed out with the obvious highlight being the Romer Medal awarded to Jack Horner for his services to palaeontology and there was a nice moment as he and both his former and present students got together for  a few photographs. It was nice, from a UK perspective, to see Andrew Milner receive a well deserved Honorary Member Award as well. 
The after hours party, the traditional closure to the meeting, took place straight after the awards ceremony in the same hall as the auctions had taken place in. While the venue was fine for the auction it did not seem to me to be an ideal venue for the party. It was like a huge underground garage to be honest and, although it was easily big enough to accommodate us all, it was hard to generate a party atmosphere early on unlike in Raleigh last year when the party started almost immediately.
There were no disco lights to create that party vibe and the drinks at the bars were prohibitively expensive – which brings me to the fun part of the evening. Very early on many of us had cottoned on that there was a shop on the fourth floor where you could buy beer at a greatly reduced cost. The flow of people visiting the shop started lightly at first and then soon became a torrent as more and more people caught on.
Eventually, the hotel management decided to stop people going back into the hall with their bargain beer with the result, at one point, that there were nearly as many people outside the hall as there was in it. And then the challenge was to smuggle the beer in without getting caught which many of us managed quite successfully.
To be honest, many of us felt that this reaction was a little over the top and unnecessary. Even when the bars had closed they would not even sell us a bottle of water – for goodness sakes it wasn’t alcohol was it? “Bar’s closed” – “All I want is a bottle of water?” – “Bar’s closed”. Charmless and rude – thank you very much.
Criticisms? Well, as mentioned above, some (but not all) of the staff could do with a little more training and being a little more helpful instead of keep answering in a couple of syllables with no charm attached. Many people have already bemoaned the lack of free Wi-Fi for the conference although it was available in the lobby but this did not help those people who wanted to disseminate information to the palaeoworld as it happened – in real time so to speak. We hope the organisers have taken note of this in preparation for Berlin next year.
Controversies? There were one or two but the most controversial surrounded Pete Larson’s poster on the validity of Nanotyrannus. Not that there was actually anything wrong with the poster (everybody has an opinion) but the fact that he was supporting his claim by actually adding a further poster displaying the tyrannosaur from the soon-to-be-auctioned Duelling Dinosaurs and displaying cast fossils from the beast.
This appears to conflict with SVP ethics and left many people aghast. For a more comprehensive retrospective account of this issue I urge you to pop over to Brian Switek’s post here for the detail. Personally, I made a point of avoiding the poster when I had heard about this occurrence but I appreciate that it was difficult for the organisers to realise that he would take the opportunity to, in effect, promote the sale of the Duelling Dinosaurs.
The last poster session featured David Peter’s poster on a “flightless” pterosaur. Now I understand that there was a chance of a few heated discussions regarding this poster and to say that Peter’s vision of palaeontology, and the science behind it, leaves something to be desired   is an understatement. However, authors are required to be present at their poster from 4.15 to 6.15 to discuss their work and answer questions – Peters was not.
At least Larson had the guts to stand by his poster but for Peters to have somebody else to stand in for him speaks volumes about his so called “science”. And, I have to say, there were other authors also away from their posters during the session. Now I appreciate that drinks are required and that a comfort break may very well be needed and that it is good to catch up with friends but there were two posters where I returned repeatedly to talk to the authors - and they were nowhere to be seen. I found this somewhat disappointing.  
There have been one or two discussions regarding the content of this year’s SVP with a few people suggesting there may be a lack of innovation and ground breaking techniques although others have countered these thoughts. I have no thoughts on this either way and I have not attended enough SVP meetings to know or make comment. I did notice one thing however.
It appeared to me early on that many discussions focussed on gathering data and doing research on various subjects whether ontogeny, taxonomy or describing new specimens perhaps using new analytical techniques and some very clever digital programs as is the norm these days. However, many questions and theories that were posed at the beginning of these presentations were not actually answered by the end of them. In other words, here is the question, this is what we have done but we have not actually been able to find the solution – in fact more questions were posed.
Initially I found this a little odd and felt, at the time, perplexed since I was listening to interesting people talking about interesting processes regarding always interesting taxa but without a satisfactory conclusion. But later, after thinking about it, I realised that I was missing the point and acknowledged that, at the very least, all of these researchers were expanding the dataset and increasing our knowledge of a much bigger picture, perhaps for other researchers to complete the tasks.
It is worth pointing out again a couple of pretty weird occurrences via the society this year – not necessarily involving the host committee. Firstly, the abstract volume was available to all and sundry quite early on, in effect open access, which is peculiar since the abstracts are embargoed until their presentation at the meeting and are only normally available to SVP members. They were lucky that, as far as I am aware, that the embargo was not broken. Add to that even the index in the volume is wrong. The pre-meeting list of those who were attending turned up via email half way through the meeting when normally emailed in advance. It is strange this has happened this way and there has not been a single comment about this, as far as I am aware, by the society as to whether this was a mistake or if they are leaning toward a more open access style. It would be nice if they were to clarify the situation.
 
A room with a view.
 
 In conclusion I have to say that I really enjoyed the meeting and, despite the aforementioned one or two issues, was really very well organised and committee deserve great credit. It was great to see so many friends and colleagues again and, of course, I was delighted to make new ones. I was again lucky that so many of them were generous with their time and not only were glad to discuss their work and plans with me but were often equally interested in how my fledgling research group was proceeding.
There is one particular instance that, I must admit, both surprised and overwhelmed me. I will not embarrass my colleague by naming him but I had already watched him present his talk at one of the technical sessions when I bumped into him later in the day. He preceded to tell me how much that he had been influenced by my writing and how it had help him develop his own career. He said some other nice things as well – I could hardly believe what I was hearing.
This was something that I did not seek and certainly did not expect – I really did not know what to say. I almost felt a lump come to my throat as we shook hands and he walked away. This is something that you just cannot buy and I am absolutely delighted to have helped someone, who obviously has a very bright future ahead of him, with his early career.
As I was saying, copious amounts of thanks to everyone who gave up their generous time to talk to me at this meeting but special mentions this year go to Thomas Carr, Richard Butler and especially my roommate, Roger Benson, who allowed me to tag along on so many occasions, listening in on so many of his discussions and helped me to learn so much.
Normally, after SVP, I tend to provide a pretty intense review of the meetings proceedings but since the abstract volume has been in the public domain for a long time now I will provide an edited form of my previous reports.  Coming up then - some of the meat and drink of the meeting featuring, amongst others, two new tyrannosaurids, a giant abelisaurid and, of course, Deinocheirus.

Wednesday, 23 October 2013

Important New Spinosaur Material From the IoW


 
Back in September, two of us from the group were fortunate enough to attend the first Jehol-Wealden International Conference held at the National Oceanography Centre in Southampton. This was a two day event comprising of a day of talks and posters followed by a day of field visits on the Isle of Wight to a few of the better known fossil localities.
For a more comprehensive report on the meeting please check out Stu Pond’s blog, Paleo Illustrata, and see just how much there that was going on. We were delighted to see so many familiar faces and I was glad to make some new friends as well.
We were very lucky that our day on the Isle of Wight was largely dry and the temperature was pleasant although, by the end of the day, some low cloud and a thickening sea mist made it quite murky. We visited Yaverland and Hanover Point and most people found a few bits of pieces, mostly rolled bone, although a couple of us managed to eke out a couple of lepidotid teeth. We were also very lucky that we got to see a large quantity of dinosaur footprints in situ and some of these were large and very impressive indeed – Martin Lockley commented that they were amongst the biggest he had ever seen.
However, the highlight, for me, was our visit to the Dinosaur Isle Museum on Culver Parade right near Yaverland. We were warmly welcomed by the staff and after a drink and a welcome speech by Steve Hutt we were able to check out all the exhibits on display – and very impressive some of them were too.
There were also some local collectors on site who were there to display some of their most recent finds - a couple of elements on display had only been found on that very morning. Chief amongst these was a superb ankylosaur specimen of which one of the spikes on display was very impressive indeed.
But the real stand out fossils on display were new specimens of what would appear to be Baryonyx sp. Stu Pond has already published one image over on his blog and I am delighted to share more images with you now. This must be the first decent UK skull material (that I am aware of) of a baryonychine since the original discovery of Baryonyx on the UK mainland back in 1983.
This appears to be a truly significant discovery since there are the remains of two individuals coming out of the quarry which is currently (and understandably) a secret location. The collector in question, who will remain nameless for obvious reasons, is currently preparing a lot of the material right now and he is genuinely hopeful (and very excited!) and believes that there is much more material from these two individuals to come to light.
I have been very fortunate to be able to observe the original material from the type specimen and I have to say, from my limited time with the new specimens, that they appear to be almost identical in many aspects to Baryonyx although, naturally, this would need to be quantified when the specimens are researched after preparation.
Either way, this is an extremely significant find and I look forward to more news of these specimens as they come to light. Overall the conference was very well received by those who were in attendance and there were already tentative whispers suggesting that this may become an on-going fixture – perhaps taking place every other year. But for now I suggest we let the organisers, particularly the industrious Gareth Dyke, a moment to reflect on a job well done and say how much we all enjoyed it.



 

 

 

 
 
 

Friday, 18 October 2013

Theropoda Sympatrico Pt.3



So we now know that palaeoenvironments with sympatric large theropods are not that unusual and that there are many examples of such ecosystems in the fossil record. The most spectacular examples of these are the previously mentioned  Late Cretaceous fauna of the Kem Kem Formation in Morocco and, perhaps even more remarkable, the Late Jurassic fauna of the Morrison Formation in North America. 
So how was it possible for so many large predators to co-exist in the same ecosystems? Well the most obvious solution to reduce competition amongst contemporary large theropods would be a form of niche partitioning. This may seem potentially easy to spot when comparing spinosaurids with generic build theropods but it is not so easy to discriminate when comparing, for example, tyrannosaurids of similar size and morphologies. This is a common problem when trying to identifying niches for sympatric theropods since the majority of them are actually quite similar to each other.

If you have been following this series of posts then you will know that Andrea Cau has pointed out that niche partitioning is somewhat complicated by the fact that many theropod genera, but particularly the largest theropods, were morphologically variable  throughout their ontogeny and were probably changing their feeding habits as the grew (eg Tsuihiji et al 2011). This is particularly noticeable in tyrannosaurids as we have seen in the past and is one of the principle arguments against the validity of Nanotyrannus.
Simple enough to postulate perhaps but does this not complicate things even further throughout the trophic ladder? Specifically this means that there were several carnivores of similar stature and morphology, whether at a specific ontogenetic stage or adult morphs, that were surely competing for the same resources? As usual these forms of questions are incredibly difficult to answer.
We still have to assume that there may be an element of bias in the taphonomic indicators and stratigraphy of these formations and this should be stressed time and time again. Perhaps more intriguing is the possible taxanomic distortion that undoubtedly exists and that we should consider the possibility that some named theropod taxa may actually be different ontogenetic stages of the same species - and how many times have we been down this road over the last few years?
The simplest solution may be that there was simply enough meat to go around and that this abundance of prey species was such that it was driving theropod diversity and numbers. This is perhaps indicated by the various ways in which it appears theropods may have despatched their prey. Tyrannosaurs most likely killed with their crushing bite, allosauroids with multiple slashing bites and claw raking and the smaller theropods probably used a similar methodology although there is a much greater variety of form in these taxa. And I am not even considering the thought here of the possibility of group hunting theropods.
Size is generally thought of as a governing factor when considering how sympatric theropods may have coexisted. It seems reasonable to assume that big carnivores would require large prey and the theropod body plan, in general, is actually quite conservative and does not enable us to identify differences easily. So perhaps the more likely answer to this issue may lie in behavioural and intraspecific processes whereby the trophic ladder is reinforced and a simple pecking order was enough to maintain the status quo.
As we pointed out in the previous post we noted that large theropods would very likely have needed extended home territories to be able to maintain their nutritional requirements. Now regardless of individual, or whether there were group territories involved, it is almost certain that large theropod territorial overlap would have taken place so this would have limited the amount of large theropods that a territory could support otherwise there would simply not be enough prey animals to go around.
Things now start to get a little complicated. It would seem that there must have been a precarious natural balance to maintain viable breeding populations of large theropods since the larger the animal gets, then the fewer animals would have been supported by the ecosystem which then reduces the chances of perhaps finding a mate. This gets really tricky if large theropods were endothermic since their nourishment requirements would be even greater.
What is seldom realised when discussing this issue is that the same trophic relationship between large theropods and their prey is repeated between their prey and the flora they feed upon. That is that there was a greater mass of available vegetation when compared to the biomass of herbivorous animals that fed on it which, in turn, would have affected the necessary increases in the range of large theropod territories.
So what we have is something of a paradox. That is what would appear to be required to enable a simple niche partitioning hypothesis to hold true actually does not hold water very well. Not that niche partitioning was unlikely, far from it, but there are many other factors which appear to contradict it and make the whole issue of sympatric large dinosaurs, in general, problematic let alone considering sympatry in large theropods.
Niche partitioning is not only restricted to large theropods and the same processes in large herbivorous dinosaurs has been looked at over the last few years and it appears that they did indeed evolve a number of adaptations in both their feeding and masticating abilities as well as cropping plants at different heights (eg Mallon et al 2012, Mallon & Anderson 2013).   However it seems that, in real terms, these adaptions are actually relatively minor and that this may be a primary reason why so many dinosaurian species had a relatively brief temporal distribution and longevity – usually in the region of one million years – sometimes considerably less, sometimes a little more (sampling bias allowing). It is certain that competition between these herbivores accelerated faunal turnover and drove evolution forward.
So now we can get an idea, perhaps, of how rapidly dinosaurs and other animals evolved due to the pressures of intense competition and natural selection. It is again important to highlight how all of these dinosaurian clades interacted with each other and unquestionably affected each other throughout the entire ecosystem.  And sometimes, when the environment they inhabited became isolated due to earth movements, climate change or river formation then this faunal provincialism becomes more amazing.
Nowhere else is this scenario dramatically highlighted than in the provinces of Laramidia where it appears that some of these provinces were incredibly small and yet were able to support a great biomass of large dinosaurs. We have looked at Laramidia before on this blog so we will not go into great detail here but it is obvious that dinosaur provincialism was extremely likely and that a great many pocket ecosystems flourished successfully for millions of years.
In the end it is not simply a matter of hypothesising about sympatric large theropods because that focusses on too narrow an area. Instead we need to look at the entire trophic package and come to realise just how unique dinosaurs were. We have to strive to understand dinosaurs more in every respect and at all levels which leads us onto their physiology.
It appears that although we understand a great deal about dinosaurian metabolic rates we still cannot say with any degree of certainty exactly what they were. I actually wonder now that perhaps the dinosaurs displayed a combination of metabolic rates – that is a kind of “niche partitioning” in dinosaurian physiology. In other words, some dinosaurs were endothermic, some were ectothermic and, as is the general belief these days, that they were something “in between”.  Whether any dinosaur could be described as truly ectothermic is unlikely since all dinosaurs appear to be fast growing and very active animals (as bone histology quite clearly shows) and yet, even if there were only the two variable metabolic rates utilised by dinosaurs, this could still help sustain unusually high populations of large animals.
For example, different dinosaurs could eat at different rates and at different times and probably reproduce in different ways during different seasons. Plants, by their very nature, would also be represented by an enormous variety and there is no doubt that some flora was highly nutritious while other forage was not so good. It seems that the herbivorous dinosaurs were able to utilise all kinds of vegetation and variable metabolism would have certainly helped their ability to do this and may have been another primary driver of the various feeding, jaw and cropping mechanics developed by these dinosaurs.
In conclusion, we have to accept that there are still so many questions that remain unanswered. We can be certain, however, that an incredible combination of factors which include geographical constraints, climate and micro-climates, plant evolution and growth, and ultimately the extraordinary physiology and evolution of the dinosaurs allowed for these remarkable ecosystems to flourish in must what have been a constant state of flux.
It is no wonder that dinosaurs evolved into so many varied forms and that species turnover was so rapid.

Note 
Just a reminder that these posts are just an example of what goes through your head sometimes when you confront the success of these animals. Sure there is a lot of science in here but there is still a great amount of conjecture as well. In other words, it may not necessarily be so – but there just may be a possibility that it is and so on…

References

Jordan C. Mallon, David C. Evans, Michael J. Ryan, Jason S. Anderson, Megaherbivorous dinosaur turnover in the Dinosaur Park Formation (upper Campanian) of Alberta, Canada, Palaeogeography, Palaeoclimatology, Palaeoecology, Volumes 350–352, 15 September 2012, Pages 124-138, ISSN 0031-0182, http://dx.doi.org/10.1016/j.palaeo.2012.06.024.
Mallon JC, Anderson JS (2013) Skull Ecomorphology of Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada. PLoS ONE 8(7): e67182. doi:10.1371/journal.pone.0067182
Tsuihiji, Takanobu , Watabe, Mahito , Tsogtbaatar, Khishigjav , Tsubamoto, Takehisa , Barsbold, Rinchen , Suzuki, Shigeru , Lee, Andrew H. , Ridgely, Ryan C. , Kawahara, Yasuhiro and Witmer, Lawrence M.(2011) 'Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia', Journal of Vertebrate Paleontology, 31: 3, 497 — 517 DOI: 10.1080/02724634.2011.557116

Monday, 30 September 2013

Theropoda Sympatrico Pt.2



In the previous post we had started to look at the importance of theropods within the ecosystem and I suggested that the possible extinction of large carnivorous dinosaurs may have been the catalyst for selective extinction for some animals and also the consequential acceleration and proliferation of others. In other words, large theropod extinction may have had direct implications for faunal turnover within ecosystems.
Although I have essentially been looking at large theropods it is worth remembering that the diversity of theropods in most ecosystems was generally very complex. Regardless of size and/or niche even the disappearance of a small theropod may have caused limited environmental problems (more of this later). In simple terms, and if we use a large predator as an example, if a particular carnivore was in decline or on the road to extinction, for whatever reason, then it is likely that the herbivorous animals that they preyed upon would increase in numbers. This, in turn, would have added pressure to the plants, trees and other flora since, as the herbivores increased in number, and then there would be less chance of a successful germination by those plants affected.
When plants are affected then, not only non-avian dinosaurs, but  everything becomes affected including, in Mesozoic times, insects, pterosaurs, mammals and birds and these effects would have changed their distribution, relative abundance  and, most importantly of all, their intraspecific behaviour. The loss of a single large theropod therefore would have had enormous effects on an ecosystem.
Another interesting thought is whether theropods displayed variable feeding tendencies like we see in carnivores today. It is certain that the majority of carnivorous theropod dinosaurs could at least be termed as hypercarnivorous – that is their diet would have consisted of at least 70% meat and it is fair to say that the majority of stereotypical theropod teeth are blade like and serrated for exactly this kind of diet.
However, it is difficult to comprehend that theropods, by their very nature, would have been able to utilise the other 30% worth of plant matter and fungi to be genuinely referred to as hypercarnivores and the vast majority of theropods should, indeed, be known as obligate carnivores since it is certain that they had neither the dentition or, even more importantly, the digestive capability to assimilate such matter.
But theropods were still exceptionally diverse and we have discovered many weird and wonderful animals now that were indeed cosmopolitan in their tastes. Ornithomimids appear to be clearly omnivorous, therizinosaurs were certainly herbivorous and the peculiar oviraptorids appear to be capable of consuming a great variety of foodstuffs. The fascinating Alvarezsaurids seem ideally suited to be insectivores whilst, at the other end of the scale, we have the great baryonychines and spinosaurs that appear to be both great fish and flesh eaters.
Regardless, the largest carnivorous theropod in any given ecosystem would still have been the most important ecological factor in determining the health and prosperity of the system. They were at the very top of the trophic cascade and would exert a level of influence on those species at the next level down – their prey. These animals too exert influence on those species below them and so on until we reach the very bottom of the trophic ladder. This is known as top-down regulation.
Large theropod dinosaurs, although relatively few in number, would have exerted considerable pressure on species below them. Fear would have been a strong driving force and their presence alone would have indirect effects on prey animals and, of course, predation would have very direct effects indeed. These effects would have had a ripple action throughout an entire community of animals so that the entire ecosystem was affected.   
And yet, as we have already observed, palaeocommunities were also inhabited by smaller theropods and these were much more diverse and common than their larger cousins. Although not at the apex of the trophic ladder they would have filled many varied predatory niches and it was this adaptability that enabled them to diversify and, as a consequence, their numbers would have been far greater than their giant cousins.
However it does seem likely that a small theropod’s disappearance would have only had a moderate effect on the ecosystem. Many of the smaller carnivores’ predatory niches would have almost certainly overlapped thus the effect on the environment would have been reduced as opposed to those effects caused by the loss of an apex carnivore.
Large apex theropods would have needed large territories to fulfil their nutritional requirements especially as it is now generally accepted that they were active fast growing animals - if not fully endothermic. In an extant mammalian ecosystem, the rule of ecological efficiency suggests that there needs to be ten times the amount of prey animals to support a modest carnivorous population. Even if dinosaurs were not fully endothermic we do understand their physiology enough to realise that this general rule of thumb would probably apply to large theropods but perhaps on a slightly lesser scale.
Allowing for sampling bias and other taphonomic distortions the fossil record for large theropods in various ecosystems tend to support this equation and that they are generally found in low population densities and would therefore have required large territories. So what were the implications for ecosystems if a top carnivore declined in numbers on the road to extinction?

Because of their limited numbers, any decline in large sized theropod populations would have been keenly felt – sooner rather than later. Their numbers would have become increasingly scattered thereby decreasing the likelihood of intraspecific encounters with others of their own species which, in turn, greatly decreased their chances of a successful mating. This leads to an accelerated rate of decline as the animals that remain may inbreed leading to further genetic complications and disease. This whole process would likely have been extremely rapid leading only to the one conclusion – extinction.  
As the large theropod population declined it is certain that the population of their main prey animals would boom and the effects on the flora and fauna would be dramatic. Plants and trees would be seriously compromised and degraded due to increased and unregulated grazing. The unchecked herbivorous dinosaurs, without fear of predation, would have also probably increased their own ranges which, in turn, would have enabled them to perhaps exploit other food sources leading to yet more environmental consequences for other species. So many things would have changed including those that would even seem to be relatively mundane such as longer feeding spells at different feeding times and, of course, the sizes of the groups and herds as they got bigger.
Would the disappearance of the giant apex theropods affect their smaller brethren?   The answer to this is an uncompromising yes. Not only did the giants keep the herbivorous population in check but it is very likely that their presence kept the numbers of their smaller carnivorous cousins under control. Released of these shackles then small carnivorous theropods may have also gone through something of a population boom which, naturally enough, would have increased predation of other taxa thus increasing further the pressure on the ecosystem. These smaller prey animals are often essential parts of ecological stability that filter right through to the bottom of the trophic ladder.
And just as the herbivorous dinosaurs behaviour would have changed so the behaviour of the smaller theropods would have changed too. It is fairly certain that the small theropod population would have been fearful in the presence of their larger cousins and very likely kept their distance. Freed of this fear factor small theropods would also probably have changed their behavioural patterns and this would also have added yet more pressure to an already distressed ecosystem.
So we can see how the sudden loss of a group of large apex theropods could possibly be the spark that leads to the degradation of an ecosystem which affects every kind of plant and animal on the trophic ladder. Understanding the trophic ladder is key to understanding ancient ecosystems and it is this realisation that everything is linked together from top to bottom that helps us see life for what it was – and is.
So perhaps you may be thinking that there may be something to all this - and I believe there is. Certainly there is every reason to believe that localised extinction events and regular faunal turnover were almost certainly driven when large theropod carnivores came under pressure and started to disappear. There are a number of factors that may have led to large theropod extinction and these include, for example, disease and environmental stress.    
And yet, as I have alluded to before, dinosaurian ecosystems represent something of a conundrum in as much that a quite a few of them now seem almost impossible to have functioned efficiently – and yet they obviously did. In the final part of this mini-series we will try and work out some of the permutations that led to the success of these ecosystems, try to understand the apparent high faunal turnover levels and why sympatry in large theropods is still kind of weird.

Tuesday, 10 September 2013

Theropoda Sympatrico Pt.1



When the Dinosaur Renaissance gathered momentum during the Seventies, its biggest proponent and champion was one Robert T. Bakker – a palaeontologist who needs no introduction. Bakker was instrumental in displaying dinosaurs in a new light. Gone were the old depictions of cold blooded, slow moving, dim witted reptiles of the primeval swamps and in their place came this new dynamic clade of animals – animals that were fast, agile, rapidly evolving and, above all, warm blooded. Indeed, things would never be the same again and we all got swept away in this new glorification of the dinosaurian race.
Chief amongst Bakker’s evidence for proclaiming the existence of endothermian dinosaurs were the use of predator/prey ratios (PPR’s).  Simply put, in any specific ecosystem, the amount of carnivores that can be supported by any given population of herbivores can be measured as a ratio. Because cold blooded carnivores generate their body heat from the sun they can eat much less frequently and, as a result, larger numbers of carnivores can exist contemporarily. But because warm blooded carnivores need to generate their heat internally they must eat much more frequently so the amount of carnivores that can be supported in the ecosystem is much much lower.
Bakker argued at the time that by comparing, not only extant mammalian communities, but also Permian reptilian faunas with dinosaurian faunas, that because PPR’s in dinosaur communities were so low, and those in the Permian were so high, that dinosaurs must have been warm blooded. At the time this was seemingly ground breaking research and there were many believers but this was clearly wrong and we now know that there are many variables that rendered the hypothesis redundant.  Not only is it flawed to compare extant mammalian communities with extinct ones but sampling in the different formations is highly variable and problematic and thus it is difficult to formulate any ratio with any confidence.
Dinosaurs may very well have been warm blooded and there is a weight of evidence now that supports that they were, at the very least, more than ectothermic if not fully endothermic. However, there was a curious by product of the predator/prey hypothesis and that was that it was commonly accepted that you would generally expect to find, in any sampled dinosaurian fauna, only the one large predator in residence. This persisted for some years probably perpetuated by the fact that Tyrannosaurus rex, as one of the best known and well researched theropods, is, indeed, the only large carnivore in the Late Maastrichtian of North America.
It was strange too that the revelation that Daspletosaurus and Albertosaurus were contemporary large tyrannosaurs in both the Dinosaur Park and Two Medicine Formations was simply accepted as unusual. The most popular explanation was that this was evidence of niche partitioning with Albertosaurus primarily feeding on hadrosaurs while the more heavily built Daspletosaurus preyed upon ceratopsids (Russell 1970).
But eventually, as more and more formations became better sampled, it became apparent that, actually, sympatric large theropods are the norm with, perhaps, the most extreme example being the population of the Late Cretaceous Kem Kem Formation in Morocco which has produced Carcharodontosaurus, Deltadromeus, and Spinosaurus amongst others.
These co-habiting theropod populations bring their own unique problems to the table and continue to fascinate palaeontologist’s in trying to work out how these large carnivores managed to share out the various resources available. These issues are amplified when we look at the amazing populations of Laramidia which displays several much smaller pocket environments where it appears virtually impossible for there to be enough resources to go around for all dinosaurs – let alone the carnivores.
Dinosaurs are freaks then and this is precisely why you cannot simply compare extant faunal communities with dinosaurian faunas. It appears almost impossible in some cases for dinosaurs to be able to coexist at all – but they obviously did and what a magnificent race of creatures they are. So how can we explain how large theropods co-existed successfully in what would appear to be extraordinary circumstances? There are many things to consider but perhaps we should look at the nuts and bolts of the carnivorous dinosaur – what is a carnivorous dinosaur, what were their functions and, most importantly of all, how important were they to the ecosystem?
Theropod dinosaurs are spectacular – from the smallest raptorial forms right through to the largest tyrannosaurs. And it is safe to assume that, when compared to their herbivorous contemporaries, that they were relatively more “intelligent”. I have put the word intelligent in quotation marks because it is important to make the distinction between intelligence, as displayed by extant mammals, and that hypothesised for dinosaurs for it is unlikely that any dinosaur was capable of intelligent reasoning in comparison, for example, to a dolphin.
But it is obvious that they would have been smarter than their prey because their predatory nature demanded it and, I believe, it is safe to assume that this would also entail a degree of complexity. How complex, again, remains a matter of conjecture but it is a possibility (some of us believe likely) that there was a degree of social complexity within Theropoda whether they were solitary hunters or hunted in groups. This is highly suggestive that there would have been a significant variety in their behavioural patterns which would have included their hunting techniques, their courtship and mating rituals and even how they may have raised their young. We only have to look at birds to get, perhaps, a hint of what may have been a variety of different behaviours displayed by their dinosaurian ancestors.
Large theropods must truly have been a sight to behold. The largest of them would certainly have nothing to fear in their ecosystem aside, perhaps, from another of their species. Other dinosaurs may have been as equally impressive and many were indeed far larger than even the biggest theropod but for me they have no equal. And despite the fact that we know so much about them it is still the vast amount of information that we don’t know about them which is so fascinating. But the one thing we can be sure of, as with any ecosystem, theropods, and large theropods in particular were at the top of the food chain - the very peak of the trophic pyramid.
Carnivorous dinosaurs were essential components of their ecosystems and it is easy to think that all they did was eat prey animals – but this is far from the truth. Without the carnivores then chaos would soon ensue. Theropods evolved to eat their contemporaries -not withstanding therizinosaurs which we will come to a little later – and they were obviously very successful at it since they were dominant throughout the dinosaurs reign but we often forget, that throughout the Mesozoic, there were a multitude of different environments. Theropods evolved in tandem with deserts, forests, coastal plains, uplands, lowlands and everything else in between and every single ecosystem depended on them to function correctly.
Theropods were the major controllers of herbivorous dinosaur populations and it is safe to assume that the rules that govern the trophic pyramids of today would have applied to those of the past. I find it particularly interesting that we consider many aspects of dinosaur extinction, not only at the K-T boundary, but also the various phases of dinosaur extinction throughout the Mesozoic without often considering environmental disruption because a species, particularly a carnivore, became extinct. We all consider environmental change due to volcanoes, earthquakes, mountain building and even the occasional meteor strike, and no doubt these were considerable influences on the environment, but extinction due to the disappearance of species is well documented – even today.
In the next part of this mini-series we will look at the cause and effects of theropod extinction on an ecosystem and consider whether this too was a major driver in dinosaurian evolution and species turnover.
Reference
Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology 1: 1–34.