Unfortunately I will not be blogging for the next two or three weeks because there is quite a bit going on my end that needs sorting out. However, I will keep my absence to the absolute minimum because I love doing this and want to get back as soon as possible.
Fortunately, I will still be in touch with things because of the social networks and mailing lists etc and I will certainly try to keep up by reading as much as I can via the Mesozoic blogosphere. In addition to that the conference season is just about to swing into action, there are more field trips in the offing and there are bound to be one or two news stories that break so there will be plenty to blog about. Until then, be safe, thanks for reading and I'll be back real soon.
Friday, 24 August 2012
|Cover art by Giang T. Nguyen|
I first became aware of Prehistoric Times (PT) back in 2001. At the time I was looking around to see if there were any magazines dedicated to dinosaurs and prehistoric life as a whole. I found two, of which one was the aforementioned Prehistoric Times, whilst the second was the ill-fated Dinosaur magazine.
The first edition of Dinosaur magazine was actually pretty good and featured a multitude of articles and stories backed up by copious amounts of images and I looked forward to the next edition. Unfortunately this never materialised and it appears that there were allegedly strange circumstances and rumours of management malpractice that were behind the disappearance of the magazine. I did here that a few people, as well as contributors, got their hands burnt during this venture and, even today, Dinosaur magazine has left a sour taste in the mouth.
However, Prehistoric Times had been around since the 1990’s and had a very respectable track record. I managed to source a sample copy of PT which was issue 47 and featured a couple of Karen Carr created dromaeosaurids on the cover – featherless still at that point. These can be seen in the Cretaceous Coastal Environment mural in the Sam Noble Oklahoma Museum of Natural History.
|Cover art by Karen Carr|
I was sufficiently impressed that I took out a subscription to the magazine and have remained a staunch supporter ever since. The man behind PT is Mike Fredericks and I must say that the amount of time and effort that Mike has put in over the years has bordered on superhuman and it appears obvious to me that is has been a struggle at times but, never the less, he has persevered and we have today a very impressive and finely crafted magazine.
PT has something for everyone who has an interest in the prehistoric world but, for me, is primarily an excellent source of information, technique and inspiration for the palaeoartist, whether he is an aspiring amateur or seasoned campaigner. I have never made any secret that my artistic abilities are relatively poor but I am constantly amazed by the quality of work that features in the magazine – not only by the top artists but also by so many amateurs out there. Indeed it is often the new and upcoming palaeoartists that come up with refreshing new ways of depicting past life.
And do not be misled that I am simply referring to artwork for there are always ample examples of superb models and kits to admire and these are also quite spectacular to look at. And, like the science of palaeontology itself, both artwork and models are constantly evolving in an effort to capture the latest depictions of prehistoric life based upon the latest scientific discoveries and, of course, any newly discovered animal is always a favourite for reconstruction.
|Cover art by Fabio Pastori|
PT, however, also caters for the enthusiast and collector as a whole and has featured a multitude of interesting articles. There are interviews with all sorts of palaeo-people which are always fascinating. Tracy Ford has been a fixture in the magazine since I have been reading PT and his How to Draw Dinosaurs has always been a favourite of mine. Another mainstay of the magazine has been Mesozoic Media which, as the name suggests, reviews books, DVD’s and other media.
There are many other cool articles (too many to highlight) which look at collectibles, TV and film, museums and exhibitions and there are always “featured” prehistoric animals in the magazine where upon readers are invited to send in their artwork to be displayed with an upcoming article about the animal. Some of the short stories are pretty good too. Those interested in the science of palaeontology are not left out and there have been interviews with various palaeontologists over the years, features on fossils and new discoveries and, at the end of the year, Steve Brusatte presents a review of the dinosaur discoveries of the year.
So, all in all, PT is an excellent palaeo-read and I readily endorse the magazine and am happy to confirm that I have been a subscriber since that first issue I bought back in 2001. If you are interested then please support Mike and PT by subscribing but only do so directly at Prehistoric Times which, incidentally is now also available for download to a multitude of devices. Highly recommended – especially to all you talented palaeoartists out there who are looking for ideas and inspiration.
|Cover art by Raul Martin|
Friday, 17 August 2012
Looking back through my blog posts over the last couple of months, it appears that things have been dominated by paper reviews and descriptions of fossils so perhaps it is now time to lighten up things for a week or two. After all, conference season is just around the corner now and there will be copious amounts of research to report on throughout autumn and into the winter.
So with that in mind I thought I would pay a little homage to the guys of Love in the Time of Chasmosaurs and feature some images from a book that I have had in my possession for many years – the aptly named Prehistoric Animals. Published by Octopus back in 1975 and edited by Ellis Owen, this book is copiously illustrated with photographs of both fossils and fascinating models and dioramas.
This is a seriously dated book in so many ways but, never the less, it is still a beautiful book to behold and brings back fond memories. The book contained many images of real fossils and it was for this reason that I kept it when all of my other books were thrown out. Strangely, all those other books that I got rid of tend to turn up on LITC anyway and it has been great to see them again.
The models have featured in other books but some in this one are probably absent from many people’s memories and are worth a look. Let’s take a look at Pteranodon first.
What a sturdy pterosaur this is – just look at that head. Not sure what to make of that crest but in combination with its distended belly and fat little drumsticks one wonders how this got off the ground.
Not dinosaur but appealing never the less (should that say appalling?) – this is the Triassic cynodont Thrinaxodon and just take a look at that expression! Modern restorations of this animal reveal a very mammalian look with a reasonable coverage of fur. This poor guy looks like he has been put together using a selection of artificial crocodilian hand bags.
This is not too terrible mind and is one of my favourite models in the book. This is Ceratosaurus feeding on what appears to be the remnants of some poor sauropod. Love the bloody carnage and the traditional tail dragging theropod design. Hard to tell in the image but it looks like the manus may actually have the right digit count.
Not so fortunate are these stegosaurs that remind somewhat of friendly cuddly hedgehogs. Do you like the neck? Erm……what neck? And the plates look like they have been driven into the unfortunate beasts back with a sledge hammer.
Getting back to a reasonable restoration of a dinosaur and this Styracosaurus is almost acceptable except for the lack of frill!
And, finally, we have, according to the caption, Anatosaurus – better known today as Edmontosaurus. Unfortunately this image is enormous and I cannot get it all in the scanner but this is the guy who counts. Makes me laugh every time I see it and, if dinosaurs said “peek-a-boo!”, then this is surely the animal that said it.
Despite all the glaring inaccuracies and appalling models, this book, and others like it, are always nice to revisit and always make me smile. It is easy to look at them and dismiss them as ridiculous, inaccurate and embarrassing but they demonstrate how the world of palaeontology is fluid and continually evolving and as such represent a part of the history of our science and so should be celebrated.
Friday, 10 August 2012
The Alioramus monograph has provided a comprehensive and meticulous description of specimen IGM 100/1844 – Alioramus altai. The comparisons throughout with other tyrannosauroids have provided more insight into what is actually the rather complex systematics of the group but still leaves questions unanswered.
One thing that is certain, however, is that A. altai is a derived tyrannosaurine tyrannosaurid for sure. This may be glaringly apparent to some but the monograph takes any lingering doubt out. But is Alioramus a genus in its own right or perhaps, as some have maintained, a juvenile Tarbosaurus? There are a few issues here.
As the authors state, the elongate skull of Alioramus appears to be diagnostic of the taxon and I would tend to agree with this. We know that all tyrannosaurids went through significant morphological change throughout ontogeny but what evidence there is suggests that the skull of Alioramus is not aberrant and that the skull length is a genuine diagnostic feature. Certainly, using the classic skull/femur ratios of Currie (2003b) and comparing the skull proportions of Alioramus with other tyrannosaurids appears to support this conclusion.
Looking at the lengthened skull, it may be that we make things more complex than they really are and ignore the obvious. I understand this, however, and we must always make our assumptions based upon the evidence. After all, let us not forget the amount of ontogenetic change there is within ceratopsids by way of example. This can be extreme so it would not be that much of a surprise if Alioramus turned out to be another ontogentic stage of Tarbosaurus or maybe another, as yet unknown, tyrannosaurid – no matter how unlikely.
But, and for the sake of argument, I believe that this is very unlikely. These beds are amongst the most heavily sampled (and poached) beds in the world and it seems improbable that there is yet another large tyrannosaurid waiting to be discovered. There is, however, a pretty complete growth series of Tarbosaurus bataar and there are indeed specimens of juveniles similar in age to A. altai – estimated to be nine years old at time of death. None of these are truly comparable as Tarbosaurus increases skull depth throughout ontogeny and it is hard to visualise Alioramus as a growth stage of this very well sampled taxon. I support the authors in considering the elongate skull of Alioramus as diagnostic.
In addition, and to bolster their argument, the authors highlight morphological disparities of the maxilla, postorbital, surangular, tibia and jugal when comparing these elements from both Alioramus and those of Tarbosaurus specimens of comparable size thus increasing the likelihood of generic separation.
Are A. altai and A. remotus the same animal? This would seem likely and yet the authors are happy to keep the two taxa separate pending further research. There are similarities in the two specimens with the most obvious being the elongate skull and both specimens are immature individuals although A. remotus appears to be a little older. There is enough detail, however, to confirm that A. altai is indeed Alioramus.
However, the holotype of A. remotus is somewhat poorly preserved when compared to A. altai thus proper comparison is difficult. The authors list several differences between the two specimens but the differences in preservation between the two is significant and is the primary reason why the authors chose to keep the two specimens generically separate for now.
A. altai also displays various ontogenetic characters that support its juvenile status and the authors compared these with specimens of both Gorgosaurus and Tyrannosaurus. Interestingly, and perhaps unsurprisingly, these shared features aptly demonstrate that these tyrannosaurids shared a common ancestor and that these same ontogentically driven morphological changes are not altered even when taxa change the entire shape of the skull.
The elongation of the skull itself is interesting since it demonstrates that skull morphology in tyrannosaurids, whilst based upon a rather consistent morphological blueprint, could actually be diversified without compromising what are considered standard tyrannosaur biomechanics. In addition, the skull displays eight cephalic horns as opposed to the usual tyrannosaur count of six and the authors suggest that these were probably for intraspecific communication and recognition as is generally considered for all derived tyrannosaurids.
Assuming then that Alioramus altai is indeed a valid taxon then what sort of animal was it and where did it fit in the Late Cretaceous environment of Nogon Tsav? Well, for me, one of the most interesting points here is that it appears we have yet again evidence for sympatric large carnivores in the palaeoenvironment – Alioramus and Tarbosaurus. So we should really put to bed any lingering doubts that sympatric large theropods are a rarity since there are now multiple examples to cite. It is only the latest Maastrichtian of North America that there appears to be the one genuine example of an environment dominated by one large carnivore – Tyrannosaurus rex.
The authors suggest that the elongate skull, the un-tyrannosaurid like teeth, the lightly built and heavily pneumatised skeleton all point to Alioramus filling an alternative predatory niche when compared to other tyrannosaurids. This makes a lot of sense when comparing Alioramus with juvenile specimens of other tyrannosaurids and there is a growing consensus amongst tyrannosaur workers that juvenile animals utilised speed and agility to take down smaller prey than the adults and that their feeding habits consequently changed throughout ontogeny (eg Tsuihiji et al 2011). Regardless of this, Alioramus is certainly different to mainstream tyrannosaurids and, as the authors point out, could not employ the classic “puncture-pull” technique employed by other tyrannosaurids.
Ultimately, we have to remember that both A. altai and A. remotus, regardless of taxanomic affinities, are only represented by the two specimens discussed and they are also both juveniles. An element of caution must be taken in this case because we do not have anywhere near a complete specimen or, more importantly, an adult animal to compare with. In addition, the holotype of A. remotus is in serious need of preparation and needs a substantial redescription. There are other skulls in existence but, as the authors point out, these are in private hands. The skull I have featured throughout this series of posts is also in private hands although only a small portion is actual bone.
Until there are more specimens available, we still have to take a cautious view regarding this enigmatic tyrannosaurid. However, with the evidence presented in this monograph, I am happy to currently accept the validity of Alioramus altai and look forward to finding out more about this intriguing animal.
The Alioramus monograph is a triumph and sets the standard for all future monographs to follow. Granted, 197 pages of anatomical detail may be deemed excessive but that would do this fine work a great injustice. You can think of it, if you like, as a car maintenance manual where every part is stripped down and photographed and described in detail – it really is very similar.
Even if your knowledge of the anatomical details of tyrannosaurs is limited, I implore you to take a look and learn because that is what it is all about. I needed extra time to come to terms with the descriptions of the cervical vertebrae of Alioramus – there were lots of going backwards and forwards and rechecking the images but you get there in the end. You will learn.
For me, the monograph actually highlights what an odd tyrannosaur Tarbosaurus is – quite primitive in fact. Quite often the aberrant morphologies here are not displayed by Alioramus but by Tarbosaurus and will make for some interesting discussions that are coming up in the next few months and, I believe, has palaeogeographical implications regarding the origins and radiation of Tyrannosauridae as a whole.
Read this monograph!
As is often the way with my posts, and whilst I have been writing this particular one, the Society of Vertebrate Paleontology have released their program for their annual meeting in October this year and, lo and behold, we have another Alioramus altai session that looks at pneumaticity in the skull followed a little later by Thomas Carr’s look at cephalic ornamentation in tyrannosauroids. No doubt more details will come to light about Alioramus and I can genuinely say that I am really looking forward to them.
Brusatte, S.L., Carr, T.D., and Norell, M.A. 2012. The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria: Theropoda)from the Late Cretaceous of Mongolia. Bulletin of the American Museum of Natural History, 366, 1 – 197.
Currie, P.J. 2003b. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the
Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40: 651–665.
Tsuihiji, T., et al. (2011). Cranial osteology of a juvenile specimen of Tarbosaurus bataar from
the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia. Journal of Vertebrate
Paleontology 31: 497–517.
Thursday, 2 August 2012
Alioramus remotus was first described by Kurzanov in 1976. The holotype (PIN 3141/1) was recovered from the Late Cretaceous Maastrichtian beds of Nogon Tsav in Mongolia and is very incomplete. A partial skull, a few cervical vertebrae, partial lower leg bones and bones from the pes are all that were found. As a result the very validity of Alioramus has often been questioned over the years with some authors suggesting the remains may represent a different ontogenetic stage of Tarbosaurus (eg Currie 2003a).
This new specimen of Alioramus (IGM 100/1844) is exquisitely preserved and very much more complete than the holotype. The skull is virtually complete but disarticulated and behind this there is what appears to be a complete series of cervical vertebrae. These are complemented by an array of both axial and appendicular elements and all together these have enabled the authors of this monograph to examine nearly every bone in depth.
The monograph is set out in a clear and concise manner. After the initial introductions that set the tone for the paper, the next sections are set out exactly as you would expect with descriptions of the skull, axial and appendicular skeleton in that order. A contents section enables you to highlight a particular bone(s) with ease so that it is easy to navigate. After the descriptions come the usual discussion topics, conclusions and references. However, what sets this monograph apart from all others are the magnificent images that accompany the text. The photographer, Mick Ellison, took over 300 images of the specimen in RAW format which has provided unparalled clarity for this work.
I also have to mention the preparation of this specimen – it is absolutely magnificent. The preparator, Amy Davidson of the American Museum of Natural History, has worked on many specimens from Mongolia in the past and her familiarity and expertise with the fossils from this region shines through. I was fortunate to meet Amy and discuss her work with her on other specimens such as Shuvuuia deserti and Citipati osmolskae and I can tell you that her resolve and attention to detail with these specimens is second to none and Alioramus altai will have been exceptionally well prepared and every available detail exposed and preserved. It really is top drawer prep work.
So then to Alioramus altai. The most apparent difference between A. altai and other tyrannosaurids is the low profile elongate skull which is mainly a product of the elongation of the bones in the snout. The skull is also highly rugose and displays multiple horns which make for a very strange looking beast. It is mainly the shape of the skull that has led other palaeontologists to suggest that Alioramus may be a different ontogenetic stage of another tyrannosaurid – particularly Tarbosaurus. However, this is hard to quantify either way since although this specimen is superbly preserved the lack of substantial postcranial remains, just as with the holotype, makes clarification difficult.
But what makes Alioramus altai? Well there are many characteristics of note and, more importantly, perhaps several autapomorphies. For example, one interesting character is that the jugal and lacrimal form an articulation that appears to be unusual in tyrannosauroids. Despite displaying what appears to be the standard condition for this articulation, the ventral ramus of the lacrimal is relatively wide compared to other tyrannosauroids and may be unique although the authors recognise that this process is liable to erosion and may not be so well preserved in other tyrannosauroids as it is in A. altai.
Despite the fact that only the left jugal remains, it is very well preserved and displays a unique laterally projecting hornlet. This feature is not found in any other tyrannosauroid although, of course, it is likely that A. remotus also possessed this structure. However, the description by Kurzanov (1976) regarding this specimen is unclear.
The ectopterygoid displays a clear autapomorphic condition in A. altai. A thickened ridge that separates twin fossae on the dorsal surface of the bone which, although may be present in other tyrannosaurids such as Albertosaurus and Daspletosaurus, is very much thinner or, indeed, absent in some cases. Intriguingly the authors still quantify this by suggesting that this thickened ridge may be an artefact of crushing but this does not appear likely to me and I suggest that this autapomorphy is real.
The splenial is located lingually on the mandible and reveals another unique condition. There is a large foramen situated anteriorly which demonstrates distinctive characteristics. It is elongate and narrow when compared to the usual circular foramen of other tyrannosaurids and is situated more or less horizontally which, again, displays a different orientation from other tyrannosaurids.
The splenial displays another likely autapomorphy. The dorsal flange of the splenial trends anteroventrally at a much shallower rate and is not is not as tall dorsoventrally as is found in other tyrannosaurids.
Unusually for a derived tyrannosaurid, laterally located teeth from both the maxilla and dentary in A. altai are narrow and recurved and resemble those found in other theropods as opposed to tyrannosaurids. This may be due to ontogeny since this specimen is clearly a juvenile but, for me, this is unlikely since other tyrannosaurids of similar age do indeed display teeth that are already thickening up as they approach the classic incrassate condition.
The cervical vertebrae display a few interesting characteristics. Firstly, the epipophyses are narrow and end in a sharp point and are considered autapomorphic in Alioramus by the authors although this may be revised since preservation of the epipophyses are rare and the condition in Alioramus may actually be a more common characteristic in other theropods than is currently known. Another possible autapomorphy is a posterior facing foramen located at the junction ventral of the postzygapophysis and dorsally of the supradiapohyseal fossa. Finally, the cervical vertebrae of A. altai are highly pneumatic and, when compared to other tyrannosaurids, the degree of pneumaticity displayed is almost excessive.
There are only three sections of dorsal vertebrae preserved and yet even here there may be a couple of unique characters present. It is possible that a fossa that leads into a foramen located ventrally to the hyposphene may be autapomorphic although the authors suggest that this may equally be an artefact or evidence of random pneumaticity. There is also a robust lamina present on the left side of one of the dorsals that partitions the posterior surface of the postzygapophyseal fossa. There is no lamina on the right side and this too may be an autapomorphic condition.
One clear autapomorphy is to be found in the only recovered dorsal rib. There is a clear pneumatic foramen on the proximal flange of the rib situated ventrally of the tuberculum and pnuematopores of this description are absent in all other tyrannosaurids.
So it can be seen that, on the face of it, there are many characters displayed in A. altai that are highly indicative that the taxon is valid but, equally, it can also be seen that many of the suggested autapomorphies are subject to various caveats. In part three we will look at what this all means with regards to the validity of Alioramus altai, its overall position within Tyrannosauridae and how this animal fitted into the Late Cretaceous ecosystem of Nogon Tsav.
Brusatte, S. L., Carr, T. D., and Norell, M.A. 2012. The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Mongolia. Bulletin of the American Museum of Natural History, 366, 1-197.
Currie, P.J. 2003a. Cranial anatomy of tyrannosaurid dinosaurs from the late Cretaceous Alberta, Canada. Acta Palaeontologica Polonica 48: 191–226.
Kurzanov, S.M. 1976. [A new Late Cretaceous carnosaur from Nogon-Tsav, Mongolia]. Joint Soviet-Mongolian Paleontological Expedition Transactions 3: 93–104, [in Russian, English summary].