why I hate theropods

A quick update

2009-11-07T15:39:00.001-05:00

Hi everyone,

Sorry for the blogging silence. It's been an interesting semester. I've been having some personal issues I'm trying to resolve, but that aside, things seem to be going good. I'm still waiting to hear about two manuscripts I submitted a couple of months ago. I also put in a grant that I'm waiting on hearing back about but I know that I probably won't hear anything positive or negative until early next year. I did receive some good news late last week. A small grant I submitted to WV NASA was accepted and I will be receiving a small award back on that, so I'm pretty happy to find this out, since especially after at the mid point of last week, I had come to suspect my grant had been rejected.

Lot of cool paleo papers have come out in the past few months but I've only had the chance to skim them, very exciting stuff. Also I wanted to take the time to make a note of this. There are a lot of good things out there in the paleoblogosphere, and I've enjoyed ~~intermediately~~ intermittently checking them from time to time over the past few months I've been on break. Keep up the good work everyone! Best wishes for the next few months.

Cheers,
Nick Gardner

Blogging hiatus

2009-09-21T13:26:00.000-04:00

Hi everyone,

I'm sorry the blog hasn't been as current lately. I'm back into classes and working hard. As such, I'm putting the blog on a break for the next few months. See you in the Winter!

Cheers,
Nick

Old news: Arenysaurus, new lambeosaurine from the Late Maastrichtian of Spain

2009-09-10T02:10:00.001-04:00

Tree presented in paper based on 57 characters derived from Godefroit et al (2008) and Evans and Reisz (2007)

Pereda-Suberbiola, X., Canudo, J.I., Cruzado-Caballero, P., Barco, J.L. López-Martínez, N. Oms, O. & Ruiz-Omenaca (2009) The last hadrosaurid dinosaurs of Europe: A new lambeosaurine from the Uppermost Cretaceous of Aren (Huesca, Spain), C. R. Palevol, 8(6): 559-572 doi:10.1016/j.crpv.2009.05.002

Arenysaurus ardevoli Pereda-Suberbiola et al. 2009

Matrix is derived from Godefroit et al. (2008)*, which the authors regarded as the most complete hadrosaurid phylogeny published... Uh-huh. Would be interesting to see where this taxon falls out in other analyses. It's weird because they cite both PrietoMarquez et al. (2006) and Horner et al (2004), both of which are much larger...

Plenty more information (including figures from the paper and photographs) is available here-
http://aragosaurus.blogspot.com/2009/08/arenysaurus-en-discovery.html
http://aragosaurus.blogspot.com/2009/08/arenysaurus-uno-de-los-ultimos.html
http://aragosaurus.com/galeria/main.php?g2_itemId=467

WeBlog Aragosaurus is a great resource!

other refs cited:
P. Godefroit, S. Hai, T. Yu, P. Lauters, New hadrosaurid dinosaurs
from the Uppermost Cretaceous of north-eastern China, Acta.
Palaeontol. Pol. 53 (2008) 47–74.

D.C. Evans, R.R. Reisz, Anatomy and relationships of Lambeosaurus
magnicristatus, a crested hadrosaurid dinosaur
(Ornithischia) from the Dinosaur Park Formation, Alberta, J.Vert.
Paleontol. 27 (2007) 373–393.

Serapods: The real mystery

2009-09-09T10:04:00.001-04:00

The real mystery is how they managed to typo "sauropod" as "serapod".
Discovery Channel- Dinosaurs: Serapods: A Mystery
Seriously. How hard would it have been to have checked how it was spelled?
Although if they'd looked at the definition from answers.com, would Discovery have tried to claim they were amphibious?

What the hell?

Thought for the day from the Fieldbook of Natural History

2009-09-09T10:00:00.001-04:00

p. 702 of Palmer and Fowler's "Fieldbook of Natural History":

It seems ridiculous to assume that any race of modern man incorporates all the worthy qualities of human beings. When one looks at the white race's record of wars and destruction, it is even more absurd that its members should consider themselves supermen.

Chimaerasuchus

2009-09-08T01:26:00.005-04:00

In terms of known and described fossils, not much is known about Chimaerasuchus, just partial mandibles and the front end of the snout... there's some limb material as well, but not much. It's an interesting taxon, usually regarded as a notosuchid or a close relative of notosuchids (Wu et al. 1995, Fiorelli and Bertini 2008-link to pdf, Turner and Buckley 2008), however, one recent analysis placed Chimaerasuchus in a different position. Jouve (2009) recovered it as the sister taxon to Edentosuchus, however, when longirostrine thalattosuchians are deleted from the matrix, it falls out as a basal notosuchian. The topology in these trees differs quite a bit from other analyses in other ways too, such as pushing peirosaurids and "sebecosuchians" as part of Neosuchia in both versions of the matrix.

(Click for larger version)

While Jouve's phylogenetic hypothesis that Chimaerasuchus represents an Edentosuchus-like form is interesting geographically, I don't think it's very likely. Chimaerasuchus looks very much like a notosuchid, especially with the forward facing nares which are not separated from each other. Edentosuchus and Chimaerasuchus do share some features (Pol et al 2004-link to pdf), but all other published analyses thus far haven't recovered them together. If Chimaerasuchus was better illustrated (not to knock the figures in the description, which are actually nice, just wish there were more views of some of the bones) or more fossils were known, we'd probably have a much better idea if it was related to "protosuchians" like Edentosuchus or to notosuchids.

C'est la vie...

Edit 9/9/09 11:14 am EST: The DOI for Jouve (2009) posted on BioOne isn't working, pointed the link to SVP's website instead... ugh.

New sauropod "Zac" discovered in Queensland

2009-08-27T11:53:00.001-04:00

From the BBC, Australia discovers new dinosaur:

Australian palaeontologists say they have discovered a new species of dinosaur on a sheep farm in the northern state of Queensland. The fossil remains of the large plant-eating sauropod, nicknamed Zac, are about 97 million years old. They were found near the town of Eromanga, in a fossil-rich area that was once covered by a vast inland sea. Palaeontologists say the find confirms Australia's importance as a centre for dinosaur discovery. The country's largest dinosaur, Cooper, was found on the same sheep farm in 2004. Cooper was almost 30 metres long and was a new species of titanosaur - enormous, armour-plated creatures. Queensland Museum palaeontologist Scott Hocknull said Zac's skeleton was smaller than Cooper's, but more complete. Zac, in common with other sauropods, had a very long neck, a small head and blunt teeth, and a long tail to counter-balance the neck. Mr Hocknull said the find was part of a new "dinosaur rush" in Australia. "We have got dinosaurs coming out of all parts of Queensland, and so Australia is really becoming this centre for dinosaur discovery." He said much of Zac's remains were sticking out of the ground, but there are further excavations planned in this dinosaur-rich area. "There will be hundreds of skeletons underneath the ground. The bone beds are so dense, you can hardly move for a dinosaur bone." Three new dinosaur species were found in the same area earlier this year, all dating to the same period as Zac - about 100 million years ago in the Early Cretaceous period.

If you're interested in more info on this story, it doesn't seem like there's a lot floating out right now, but check out The Outback Gondwana Foundation. Their site has more information on the "Cooper" specimen (direct link to "Cooper" page). Aside from that though, the site is a little thin, a lot of it seems to be under development, so I guess we'll have to keep checking back to see when it gets updated.

Of course, everyone is already familiar with the two new published titanosauriform sauropods which came out last July in PLoS, Diamantinasaurus and Wintonotitan. If you somehow managed to miss this, you can check out the original description of both of these taxa (plus the new theropod Australovenator) at the PLoS site.

*EDIT*: This could be a picture of some of the bones of "Zac" in a field jacket

Tail clubbing in a "dinosaur" and in a dinosaur

2009-08-26T15:22:00.001-04:00

Fun day for paleontology related news!

The Telegraph is running this story:
Dinosaurs hit rivals like athletes hit balls

Glyptodont dinosaurs had a finely-adapted tail with a "sweet spot" which clubbed rivals in the same way as tennis or cricket players hit balls, scientists say.
The two-ton prehistoric beast - which grew to the size of a small car - killed predators by swinging its spiked tail with the skill of an Andy Murray backhand.

The clumsy, bizarre-looking mammals were covered with a thick tortoise-like shell and roamed the planet up to 23 million years ago. They had bony tail 'clubs' that could be used as weapons to hit rivals in the same way tennis players such as such as Roger Federer, the Williams sisters and Andy Murray hit the ball.

New research now shows the tail was finely adapted to deliver accurate powerful blows with the largest spike - just like the "sweet spot" in tennis rackets and cricket bats.

I don't think the journalist is to blame though, notice that the rest of the article goes on to call them mammals, and even later in the article, they acknowledge that glyptodonts are fossil armadillo relatives-

Glyptodonts died out at the end of the last ice age 10,000 years ago were much larger relatives of the modern armadillo. They originated in South America and spread northwards as far as southern North America.

I suspect that unfortunately for the journalist, this is the fault of an editor's @$%# up. Glyptodonts aren't dinosaurs. This is something as simple as which could have been confirmed through something as simple as Wikipedia or a quick search using Google. Even the article itself (as I already noted) calls them mammals, so I'm fairly hard pressed to get why the headline calls them dinosaurs.

Photographs of a fossil mount of Panochthus, a glyptodontid mammal, taken by Ryan Somma via Wikipedia.

Now, on the other hand, here's a news story about tail clubs in actual dinosaurs!

From Wired, CT Scans Show Dinosaur Tail Was a Bone Crusher

An Ankylosaurus probably couldn’t kill a Tyrannosaurus rex with the club at the end of its tail, but new research suggests the bony bludgeon could definitely break its ankles.

To estimate just how hard Ankylosaurus could hit with its tail club, Canadian researchers examined CT scans of several fossilized tails from dinos of different sizes. Combining the imaging data with measurements of the dinosaur’s backbone, they determined the Ankylosaurus could swing its tail in a 100 degree lateral arc, and that larger clubs could generate forces strong enough to crush bone.

"The small ones would be like hitting something with a bowling ball,” said dinosaur researcher Victoria Arbour of the University of Alberta in Canada, author of the study, published Tuesday in PLoS ONE. “And you really wouldn’t want to be around when the bigger ones are swinging.”

Scientists have long speculated that heavily armored ankylosaurids used their tail clubs to fend off other dinosaurs, but until now, no one had studied whether the club was a biologically feasible weapon. Using CT data and three-dimensional computer modeling programs, Arbour calculated the volume, mass and impact speed of both small and large tail clubs from dinosaurs in the Ankylosaurus family.

A much better article than the one running in the Telegraph. Another plus is that there's a really awesome looking drawing in this article too. Check it out

For those of you who've forgotten what an ankylosaurid dinosaur looks like...

Life reconstruction of Ankylosaurus by Mariana Ruiz Villarreal, obtained via Wikipedia.

h/t to Michael Barton for noticing the article in the Telegraph about glyptodonts, and to Andy Farke for pointing out the new ankylosaurid paper

edit: added a trackback link (I think)...

Handedness in the feeding behavior of fossil whales

2009-08-24T23:50:00.000-04:00

Beatty, B. and Dooley, A. 2009. Injuries in a Mysticete Skeleton from the Miocene of Virginia, With a Discussion of Buoyancy and the Primitive Feeding Mode in the Chaeomysticeti. Jeffersonia, 20. (PDF)

A mostly complete skeleton of a mysticete from the Carmel Church Quarry displays some injuries, including a fractured and partially-healed left mandible, previously not reported in any fossil mysticete. The mostly healed nature of this non-union impaction fracture indicates that the animal died a significant amount of time after the injury. Additional injuries of the postglenoid process and left premaxilla, as well as the nature of the impaction fracture in the mandible suggest that the cause of this was some impact from the left anterior aspect. Possible scenarios for how this injury could have happened include intraspecific aggression and, more likely, impact with the seafloor during benthic feeding. The ribs of this individual are heavily osteosclerotic from dorsal to ventral ends, which would suggest that this taxon was a benthic feeder. In comparison with a sample of ribs from fossil mysticetes, it appears that Diorocetus may have been one of the last mysticetes with rib osteosclerosis, a feature possibly primitive to Mysticeti. Although this remains speculative, the presence of osteosclerotic ribs
in primitive mysticetes suggests that the feeding mode employed by the earliest Chaeomysticeti was one of benthic feeding.

I like papers where they infer behavior from the actual skeleton. And I like fossil whales. This paper is a two for the price of one. And if you didn't catch the hint from the beginning of my post, the price of this paper is *FREE*.

For a more astute discussion of this new paper, the primary author Brian Beatty has posted about this new paper on his blog, see The Aquatic Amniote. Alternatively, you can check out a popular press article here- Fossil whale offers clues on feeding, handedness (The Virginian-Pilot).
This new specimen of Diorocetus is mostly complete but lacks the fore limbs and the tail (too bad). Beatty's blog features some images not featured in the original paper, such as a photograph of the entire skull and a life reconstruction. I don't read too many mammal papers, but I enjoyed this one. This paper changed the way I saw filter feeding in whales, and led me to look up a few other papers on the subject.

It's worth your time to take a look at this.

The Great Pacific Garbage Patch

2009-08-23T09:34:00.003-04:00

I'm sure that you guys (like me) have been aware of this for awhile, but sometimes being able to see it helps drive the point home. Our planet as a viable place for human life can't last forever.

Cheers,
-Nick

SVP Climate Change Videos Now Online

2009-08-14T16:37:00.004-04:00

Re-posted from the SVP notice sent over the mailing list-

Today global climate change is altering not only the average global temperature and length of seasons but also sea level, rainfall, severe weather events, agricultural productivity, the spread of diseases and the distribution of plants and animals. Global-change scientists, including paleontologists, are developing models and acquiring data to understand the environmental and human consequences of modern climate change. The fossil record is a critical source of biological and environmental information for evaluating the effects of climate change on species, ecosystems and evolutionary processes.

In these three videos from the Climate Forum at the 2008 SVP annual meeting in Cleveland, three global-change scientists share how insights from the fossil record for ecological and evolutionary responses of plants and animals apply to climate changes underway today. The brief introduction at the beginning of each video is given by Catherine Badgley, University of Michigan (SVP Past President).

The videos can be viewed for free on the SVP website here:
Link to Global Climate Change: The Perspective from the Fossil Record.
Videos from the Climate Forum in Cleveland

Two Cent History Tour of Sebecosuchia

2009-08-09T03:07:00.005-04:00

Sebecosuchia was first named by Edwin (not Stephen) Colbert for Sebecus and Baurusuchus (Colbert 1946). Turner and Calvo (2005) recognized Stratiotosuchus, Ayllusuchus, Ilchunaia, Bretesuchus, Bergisuchus, Pabwehshi, Iberosuchus, Eremosuchus and their new taxon, Pehuenchesuchus as being sebecosuchians. Their analysis put placed Sebecosuchia as the sistergroup to the taxa we usually would call 'notosuchians' (though technically, the phylogenetic definition of Notosuchia would cover sebecosuchians as well). They did not recognize a distinct division of the Sebecosuchia into two separate clades (e.g. baurusuchids and sebecids), but instead for 'sebecids' to form a paraphyletic assemblage to the Baurusuchidae (incl. Baurusuchus, Pabwehshi, and Bretesuchus).

Larsson and Sues (2007) offered a very different arrangement in which sebecids (represented by Sebecus and Bretesuchus) were the sistergroup to the Peirosauridae forming a clade that they called "Sebecia". "Sebecia" was the sistergroup to the Neosuchia, and Baurusuchus was more basally placed relative to these groups, as was Araripesuchus, and the notosuchians (only represented by Notosuchus and Malawisuchus). They also offered two new phylogenetic definitions for the Sebecidae and the Peirosauridae which would not be very useful in other topologies since both were basically defined to exclude each other (e.g. Sebecidae as Sebecus but not Uberabasuchus or Peirosaurus and Peirosauridae as Uberabasuchus and Peirosaurus but not Sebecus), and in current more global analyses of crocodyliforms (where sebecids are derived members of a clade with notosuchians and peirosaurids are basal neosuchians), it would effectively make all notosuchians to be 'sebecids' and all neosuchians to be 'peirosaurids'. It seems very strange to me that Larsson and Sues (2007) also found Stolokrosuchus (an odd longirostrine form) to be a peirosaurid as well, this taxon is otherwise a basal neosuchian (Turner and Buckley 2008), but more on Stolokrosuchus later...since you can count on more of me giving my two-cents on crocodyliforms to come in the future.

Wargosuchus and Cynodontosuchus are two other baurusuchids which haven't been treated within a phylogenetic analysis to my knowledge, but are both from the Late Cretaceous of Argentina. And of course, there are the three Eocene Venezuelan sebecids... Langstonia, Zulmasuchus, and Barinasuchus. Knowing more about how these taxa really fit in would be good. The same goes for the poorly known trematochampsids for which we have no idea if they have anything to do with sebecosuchians or if they're closer to peirosaurids or something entirely different.

Old news, but a lot of new names for Cenozoic South American sebecosuchians

2009-08-08T12:03:00.004-04:00

Wow, I just got this paper today (and its lit cited has a lot of papers I'd never seen before too!)-

Paolillo, A. and Linares, O. 2007. NUEVOS COCODRILOS SEBECOSUCHIA DEL CENOZOICO SURAMERICANO (MESOSUCHIA : CROCODYLIA). CONTRIBUCIONES OCASIONALES EDITADA POR EL LABORATORIO DE PALEOBIOLOGÍA, numero 3

This paper has several new names-

1. Barinasuchus arveloi as a replacement name for Sebecus cf. huilensis.
2. Langstonia as a new genus for Sebecus huilensis (Langston 1965).
3. Zulmasuchus as a new genus for Sebecus querejazus (Buffetaut and Marshall 1991). They also sink Sebecus carajazus (Gasparini et al. 1993) into Z. querejazus.

According to these authors, Sebecosuchia is divided up into:
1. Baurusuchidae (Price 1945): Cynodontosuchus, Baurusuchus, Stratiotosuchus, Pehuenchesuchus.
2. Bretesuchidae (Gasparini et al. 1993): Bretesuchus, Zulmasuchus.
3. Sebecidae (Simpson 1937): Sebecus, Ilchunaia, Langstonia, Ayllusuchus, Barinasuchus.

The paper is in Spanish, so I'm sure as I read through it, I'll be posting more comments later. = )

For now, I leave you with some of their photos of Barinasuchus ...

Call the shot

2009-08-08T11:41:00.002-04:00

Hi readers,

What would YOU like to see more of on this blog? This is an open thread, go for it.

-Nick

Knowing your crocodyliforms

2009-08-06T23:57:00.002-04:00

For the purpose of this post (and subsequent related ones), I'm following Turner and Buckley (2008) and Pol et al. (2009) since these are the only large-scale published analyses of crocodyliforms that I'm familiar with. The purpose of this is to try and help familiarize readers with the different clades/grades in this group.

Crocodyliformes are pretty much just crocodylomorphs that are more derived than sphenosuchians. The most basal crocodyliforms are the protosuchids, e.g. Orthosuchus, Protosuchus, Hemiprotosuchus, and the herbivorous Edentosuchus. They span a large geologic range, from the Late Triassic to the Early Cretaceous. Mesoeucrocodylia includes forms that are closer to crocodylians than Protosuchus, such as the gobiosuchids (e.g. Zaraasuchus and Gobiosuchus) which are small Late Cretaceous forms from Mongolia and also more derived forms like Zosuchus and Hsisosuchus.

For now, I'm assuming that the Notosuchia/Ziphosuchia recovered by T&B/Pol et al is "real" (e.g. 'sebecians', 'notosuchians' etc), so this clade plus the Neosuchia are basically Metasuchia (e.g. Notosuchus + Crocodylia). As far as phylogenetic definitions go, basically, all taxa closer to Notosuchus than to crocodylians should be notosuchians, but croc PN (phylogenetic nomenclature) is incredibly FUBAR right now (something to sort out in a later post?), so forgive me if I lapse and mistakenly refer to these as 'ziphosuchians' (or some other name) . Araripesuchus, Mahajangasuchus, peirosaurids (incl. Hamadasuchus), and trematochampsids seem to float around near each other interchangeably, as basal members of either metasuchian clade, I tend to think of these of all these taxa as 'peirosaurs' more or less, they look very similar to each other (except for the bizarre Mahajangasuchus), if I recall right, these are all from the Cretaceous of Gondwana.

Within the Notosuchia, the taxa most people readily think of as 'notosuchians' don't form a clade to the exclusion of 'sebecosuchian'/'sebecians', Simosuchus is apparently the most basal, then candidodontids (e.g. Malawisuchus and Candidodon), notosuchids (Notosuchus, Comahuesuchus and Mariliasuchus), then sphagesaurids (Armadillosuchus, Sphagesaurus, and Adamantinasuchus) and Chimaerasuchus. The sebecosuchians, e.g. taxa like Sebecus and Baurusuchus are closest to the sphagesaurids. Most of the basal notosuchians are from Gondwana, but the sebecosuchians are more globally distributed. As far as I know, these are all from the Cretaceous, with no currently known earlier forms.

Neosuchians are where we first see aquatic forms (Mahajangasuchus is either an aquatic notosuchian or a basal neosuchian...), with the Jurassic thalattosuchians which are apparently closely related to the Cretaceous-Paleogene pholidosaurs. Moving closer to modern crocodilians, you get goniopholids from the Jurassic and Cretaceous around the world, hylaeochampsids (Hylaeochampsa and Iharkutosuchus), atoposaurids, and various eusuchians leading up to the crown clade (e.g. Isisfordia, Rugosuchus, Shamosuchus, Bernissartia). The position of Pristichampsus is variable with respect to whether or not it's within the crown clade (more derived than Gavialis) or outside of it.

More detailed posts to come, count on it.

Related posts

Picture post: Columba livia

2009-08-06T01:05:00.004-04:00

Click for full image

Yes, a theropod. Well, part of one. I found this while walking around outside my house. Hopefully this'll come in handy for someone out there.

New description of Hungarosaurus

2009-07-25T14:30:00.003-04:00

A new paper on Hungarosaurus is out, which offers additional description of new material, reconstructions of the entire skeleton and the dermal armor, body mass estimations as well as an updated phylogenetic analysis for which the topology is not any different from Osi (2005) or my ankylosaur composite matrix.

See: Osi, A. and Makadi, L. 2009. New remains of Hungarosaurus tormai (Ankylosauria, Dinosauria) from the Upper Cretaceous of Hungary: skeletal reconstruction and body mass estimation. Paläont. Z., 83: 227-245.

Modified from Figure 11 in Osi and Makadi (2009) - Top, skeletal reconstruction with dermal armor in left lateral view, Bottom, dermal armor reconstruction in dorsal view

With the new material, they found that Hungarosaurus also possessed paravertebral elements as in Minmi (either ossified tendons or sesamoids according to Molnar and Frey). A lot of the new material fills in the missing gaps not present in the original described material, letting them put together a skeletal reconstruction (see above).

For additional reading on Hungarosaurus...

Osi, A. 2005. Hungarosaurus tormai, a new ankylosaur (Dinosauria) from the Upper Cretaceous of Hungary. Journal of Vertebrate Paleontology, 25: 370-383. (peer-reviewed paper)
Darren Naish's post on Hungarosaurus from Ankylosaur Week 2008 on Tet Zoo (blog post)

Iharkutosuchus makadii: an unusual eusuchian crocodyliform

2009-07-25T10:38:00.005-04:00

Iharkutosuchus is very cool (and unusual). Three papers have been published on it, but it's a complete no-blip on the blogosphere radar. So I thought I'd take the time to post some information and images of this awesome eusuchian.

Figure 1 from Osi (2008)- Iharkutosuchus paratype, A-B skull in dorsal view; C-D skull in ventral view

Iharkutosuchus has a low, short, and moderately broad skull. Osi et al. (2007) ran a modified version of the matrix from Buscalioni et al (2001- Allodaposuchus). Their results show that Iharkutosuchus is a hylaeochampsid (Osi et al. 2007) based on the presence of a straight suture between the frontal and parietal, the prefrontal is longer than lacrimal, the pterygoid flanges are relatively small, and there is a vertical ridge on the occipital surface of the paroccipital process just lateral to the distal end. Osi et al. also ran a constraint based on molecular-morphological topologies from Gatesy et al. 2003, which resulted in Allodaposuchus being a hylaeochampsid. These taxa are close in other published trees (e.g. Pol et al. 2009). Only time (i.e. better fossils, better datasets) will tell.

Iharkutosuchus shows heterodonty (e.g. from anterior to posterior, the teeth transition from incisiviform to premolariform to molariform) and multicusped teeth, as well as tooth wear that seems to indicate that the mandible may have had some mediolateral movement while biting. Many other heterodont crocodyliforms do not have incisiviform anterior teeth, instead they are mostly conical (except being Simosuchus with its weird pseudo-ankylosaur teeth). Osi et al. regarded Iharkutosuchus as herbivorous, feeding on tough fibrous plants. Osi and Weishampel (2009) took this even further, presenting a detailed description of the microwear and mandibular mechanics.

Figure 9 from Osi (2008) - Reconstruction of Iharkutosuchus skull in A- ventral, B- dorsal, C- left lateral views, mandibles D- left in lateral view, E- both in dorsal view

Incidentally, Iharkutosuchus comes from the same formation as Hungarosaurus (a nodosaurid ankylosaur). Osi (2004) noted the presence of rhabdodontid and theropod teeth here as well. Polyglyphanodontine teiids (e.g. Bicuspidon were also crawling around here too. Azhdarchid pterosaur fragments have also been recovered here. Hopefully, this is enough to get some paleoartists interested in some scenes ;)

References on Iharkutosuchus

Osi, A. 2008. Cranial osteology of Iharkutosuchus makadii, a Late Cretaceous basal eusuchian crocodyliform from Hungary. N. Jb. Geol. Paläont. Abh., 248: 279-299.
Osi, A., Clark, J. M., and Weishampel, D. B. 2007. First report of a new basal eusuchian crocodyliform with multicusped teeth from the Upper Cretaceous (Santonian) of Hungary. N. Jb. Geol. Paläont. Abh. 243: 169-177.
Osi, A. and Weishampel, D. B. 2009. Jaw mechanism and dental function in the Late Cretaceous Basal Eusuchian Iharkutosuchus. J. Morph., online doi: 10.1002/jmor.10726

The relative phylogenetic position of Gracilisuchus in Dilkes and Sues (2009)

2009-07-23T11:33:00.004-04:00

Recently, Dilkes and Sues published a redescription of Doswellia in JVP. It is an attractively illustrated paper with a lot of informative text, but I noticed something that has bothered me for awhile...

+--Mesosuchus
`--+--Prolacerta
   `--+--Proterosuchus
      `--+--Euparkeria
         `--+--Erythrosuchus
            `--+--+--Doswellia
               |  `--Proterochampsidae
               `--+--Turfanosuchus
                  `--+--Yonghesuchus
                     `--+--+--Marasuchus
                        |  `--Scleromochlus
                        `--+--Gracilisuchus
                           `--+--Qianosuchus
                              `--+--Parasuchus
                                 `--Stagonolepididae

Dilkes and Sues noted that the "relative positions of Parasuchus and Gracilisuchus differ from previous studies where phytosaurs are placed near the base of Crurotarsi, below Gracilisuchus, stagonolepidids, crocodylomorphs, and the various "rauisuchian" taxa. In this study, Gracilisuchus is at the base of Crurotarsi whereas Parasuchus is placed as the sister taxon to Stagonolepididae above Qianosuchus".

While their data set does place Gracilisuchus as outside of the "Parasuchus+Qianosuchus+Stagonolepididae" clade, it doesn't necessarily mean that Gracilisuchus is actually closer to the base of Crurotarsi than those taxa. I believe this is a taxon sampling artifact (possibly character sampling too). If some of those various "rauisuchian" taxa or crocodylomorphs were added to the matrix, Gracilisuchus may easily float back up. Remember, how you look at taxa are entirely relative. For example, I could do this:

+--Ornithischia
`--+--Sauropodomorpha
   `--+--Tyrannosauridae
      `--+--Ceratosaurus
         `--Abelisauridae

And it doesn't mean that tyrannosaurids are necessarily basal theropods. ;)

I'm not implying that I think that phytosaurs and aetosaurs form a clade to the exclusion of all other crurotarsans, to be clear.

References cited:
Dilkes, D., and H.-D. Sues. 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29:58-79.

Nominate your favorite paleoblogging posts to Open Lab '09

2009-07-19T08:14:00.004-04:00

There's a lot of decent paleoblogging going on out there. It only makes sense to try to see it get put into some other form and to get more representation for paleontology and evolution out there. Start nominating your favorite posts by paleobloggers today. I've already started nominating others myself!

For more information check out this recent post on A Blog Around the Clock

Drag this link, Nominate to OpenLab '09, into your toolbar for easier nomination when you see a post on a paleontology blog that you like.

Cheers all,
-Nick

Turtle origins, worse than snake origins

2009-07-17T22:42:00.004-04:00

My previous post "The origin of snakes" was post #100 on why I hate theropods.

Since post #100 was on the vortex that is snake origins, then post #101 should be on the vortex that is turtle origins. :)

I usually try to avoid turtles. I've covered them once before on this blog [link]. The catch in covering that is that I was commenting on how a creationist blog was quote mining news articles on Odontochelys, a transitional turtle from China.

Now once again, Michael of "New Discoveries & Comments About Creationism" is providing us with more uninformed commentary regarding turtle origins. Read: "Morphology: The Quest To Explain A Turtle's Shell"

Michael oversimplifies and goofs on the differences between emergentist and transformationist views:
"Now transformationists believes there is a “morphological evolution as a result of natural selection working on variation.” On the other hand, emergentists, believe in looking for developmental stages of turtles to look for clues about their evolutionary history."

Michael is just basically paraphrasing Rieppel on tidbits to provide the necessary launching ground for his 'attack'.

When it came to explain Odontochelys researchers took the “emergentists” approach…"

"Not surprisingly, the researchers in this paper already were focused on Odontochelys being a ‘missing link’ rather than a specialized form. More glory in ‘missing links’ than specialized forms. They on with their explanation which turns out to be a very confusing statement"

First, Michael presumes the authors accepted a de novo origin of the shell a priori, which may not really matter given their developmental observations seems to strongly favor it. Maybe Odontochelys is a specialized aquatic proto-turtle that has little to do directly with the origins of the rest of the group, but that isn't what the developmental evidence suggests.

Second, I do not see anything confusing about the statement that Michael quotes (see his blog--but it's basically the last paragraph of Nagashima et al.'s paper), and it is not explaining away the 'biogenetic law while using it to explain turtle evolution'. 1. They are not claiming that turtle embryonic development complete recapitulates the evolutionary history of turtles. 2. They are claiming that their observations of developing turtle embyros shows that the carapace is formed from intramembranous bone around the ribs and vertebrae, rather than fusion of separate bones with each other and the underlying ribs as argued by the composite or transformationist viewpoint. 3. This claim seems to suggest that developmental observations agree with the "de novo" or emergentist hypothesis of the origins of the shell in an evolutionary context, to which Odontochelys also seems to support.

Perhaps if Michael had digested the paper in its entirety he would not have been confused. But from there, he spouts off the usual creationist spiel regarding Haeckel and 'ontogeny recapitulates phylogeny'. In response to that, I'll simply point to Talk Origin's Index to Creationist Claims--see "Haeckel falsified his embryo pictures" and "Recapitulation theory is not supported".

I've kept my comments relatively muted here because comments by 'Olorin' on Michael's blog have already taken him to task. See here, but in case Michael feels persecuted and decides to delete his comments, I've webcited the page as I saw it when I wrote this post. See here.

For even more uninformed commentary if you're feeling mentally masochistic, you might check out this story's coverage on Creation-Evolution Headlines [link]. It's not drastically different from Michael's comments, so I wouldn't recommend readers put themselves through the pain of reading the same type of nonsense twice.

So if you're looking for some relief from this garbage and would like to read some informed commentary on Nagashima et al.'s paper, look no further than Ed Yong's Not Exactly Rocket Science -- "How the turtle got its shell through skeletal shifts and muscular origami"

Way back when Odontochelys was first published, Matt Celesky put together a link list of articles and blog posts put out on it. See here

Some relevant/recent publications:
Joyce, W. G. et al. 2008. A thin-shelled reptile from the Late Triassic of North America and the origin of the turtle shell. Proceedings of the Royal Society B, doi: 10.1098/rspb.2008.1196
Li, C. et al. 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature, 456: 497-501. doi:10.1038/nature07533
Lyson, T. and Gilbert, S. F. 2009. Turtles all the way down: loggerheads at the root of the chelonian tree. Evolution and Development, 11: 133-135. [see the numerous references herein]
Nagashima, H. et al. 2009. Evolution of the turtle body plan by the folding and creation of new muscle connections. Science, 325: 193-196, doi: 10.1126/science.1173826
Reisz, R. and Head, J. 2008. Turtle origins out to sea. Nature, 456: 450-451, doi: 10.1038/456450a
Rieppel, O. 2009. How did the turtle get its shell? Science, 325: 154, doi: 10.1126/science.1177446

The origin of snakes

2009-07-16T21:47:00.004-04:00

This isn't going to be a very long post since I'm venturing far from my comfort zone, but I've wondered about the origin of snakes for awhile now.

There are two dominant ideas concerning the origin of snakes and their characteristics. The first is that snakes acquired their long, limbless bodies from burrowing ancestors, such as dibamids, amphisbaenians or burrowing scincomorphs. These taxa do share some similar osteological and soft-tissue characteristics. The second is that snakes are derived varanoids, such as the aquatic mosasauroids. This is based on some seeming similarities between the skulls of varanoids and snakes.

Most people nowadays are probably more familiar with the latter hypothesis because of the discovery of some fossil snakes with hindlimbs (ex. Pachyrhachis) and some molecular analyses have also found a relationship between varanid lizards and snakes.

So when Jack Conrad published a large morphological analysis of squamates (Conrad 2008) and found snakes to be resolved as scincomorphs, I admit I was a little skeptical.

But maybe burrowing scincomorphs are relevant to snake origins after all- see these articles in the NY Times and in Science.

Honestly for me, this falls more into the 'ain't it cool' news bit, since I'm not leaning one way or another, because I know I'm not well-informed enough on this topic to get out of the realm of the armchair, but I find both opposing hypotheses to be equally appealing.

Admittedly, I found reading Vidal and Hedges (2004) to improve some of my ignorance on the topic. Hopefully, my brief muddlings on the topic will encourage some of you to get out and read more about it, I know I will be.

Some relevant articles:
Caldwell, M. W. and Lee, M. S. Y. 1997. A snake with legs from the marine Cretaceous of the Middle East. Nature, 386: 705-709.
Coates, M. and Ruta, M. 2000. Nice snakes, shame about the legs. Trends Ecol. Evol., 15: 503-507.
Conrad, J. L. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History, 310: 1-183.
Maladen, R. D., Ding, Y., Li, C., and Goldman, D. I. 2009. Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard. Science, 325: 314-318.
Rieppel, O. and Zaher, H. 2000. The intramandibular joint in squamates and the phylogenetic relationships of the fossil snake Pachyrhachis problematicus Haas. Fieldiana (Geology) New Ser., 43: 1-69.
Rieppel, O., Zaher, H., Tchernov, E. and Polcyn, M. J. 2003. The anatomy and relationships of Haasiophis terrasanctus, a fossil snake with well-developed hind limbs from the Mid-Cretaceous of the Middle East. Journal of Palaeontology, 77: 536-558.
Vidal, N. and Hedges, S. B. 2004. Molecular evidence for a terrestrial origin of snakes. Proc. R. Soc. Lond. B (Suppl.-Biology Letters), 271: S226-S229.

Shamosuchus redescription available through AMNH

2009-07-13T13:03:00.002-04:00

The latest paper that I'm aware of on crocodylomorphs is out-

Pol, D., Turner, A. and Norell, M. 2009. Morphology of the late Cretaceous crocodylomorph Shamosuchus djadochtaensis and a discussion of neosuchian phylogeny as related to the origin of Eusuchia. Bulletin of the American Museum of Natural History, no. 324.

ABSTRACT: "We describe a new specimen of the fossil crocodyliform taxon Shamosuchus djadochtaensis from the late Cretaceous Djadokhta Formation. The new specimen consists of an almost complete skull found in association with postcranial material. Because it is considerably more complete than the holotype, the new specimen permits proper diagnosis of Shamosuchus djadochtaensis and offers new information for exploring its phylogenetic relationships. The phylogenetic analysis conducted here improves taxon sampling of neosuchian crocodyliforms with respect to previous approaches to crocodyliform systematics and reveals that Shamosuchus djadochtaensis bears important information toward an understanding of the relationships of advanced neosuchians and the evolutionary origin of Eusuchia. Shamosuchus djadochtaensis is found to be the sister group of Rugosuchus nonganensis, comprising an Asian clade diagnosed by the presence of a sagittal ridge on the dorsal surface of the frontal, confluent openings for the exit of cranial nerves IX-XI, a posterior region of the palatine bar between suborbital fenestra that is flared posteriorly, and a longitudinal ridge on the lateral surface of the angular. This clade is inferred to be the sister group of Eusuchia, to the exclusion of Bernissartia fagesii and the Glen Rose form, based on the absence of an acute anterior tip of the frontal that wedges between the nasals, the presence of rodlike neural spines in the posterior cervical vertebrae, procoelous cervical vertebrae, and the presence of hypapophyses in the three anteriormost dorsal vertebrae. Incorporating the new information into the phylogenetic analysis indicates the decoupled nature of the evolutionary history of procoely in different regions of the vertebral column and the eusuchian type of palate, both traditionally considered as diagnostic of Eusuchia. All these features have complex evolutionary histories with several cases of convergences and reversals. Finally, a review of all the available evidence on the diversity of advanced neosuchians suggests this group achieved a worldwide distribution and a remarkable morphological diversity, pushing their evolutionary origins back to the Jurassic."

The paper can be downloaded for free (hail Open Access?) here:
http://hdl.handle.net/2246/5977

Picture post: Odocoileus virginianus (Mammalia, Artiodactyla)

2009-07-11T10:32:00.000-04:00

Odocoileus virginianus

I took these at Mount Storm Lake, West Virginia a few weeks ago