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Monolophosaurus

By ScottHartman
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Because the internet never loses anything, the very old (2003) version that I had pulled from my website years ago still turns up in search engine results. So here's an updated one that reflects the basal-tetanuran pedigree that most researchers agree on these days.
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© 2015 - 2020 ScottHartman
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anonymous's avatar
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PedroSalas's avatar
Might the function of the crest be related to the housing of air sacks? I thought of that after having observed the two foramina on the rear, before the lacrimal and having read in wikipedia how heavily pneumatised that area of the skull is.
ScottHartman's avatar
The crest certainly does house airsacs, but it's not clear why that would be an advantage. I think some combination of species identification/mating behavior are most likely. So why put air sacs in it? Bone is the most energetically expensive tissue during growth, so making less of it (plus saving on weight in the skull) are good things to do.
PedroSalas's avatar
I don't know whether it is too bold on my part to suggest that the airsacs were there to refrigerate the brain and so they needed a bony crest to be housed close to the braincase? Apart from the display function, of course.
ScottHartman's avatar
It's not too bold, but you'd have to explain why Monolophosaurus was in greater need of brain refrigeration than other theropods.
PedroSalas's avatar
In order to do that I'd have to have access to the skeleton so as I could study it by myself...and perhaps I'd need to take a college degree in paleontology too.
Paleo-reptiles's avatar
while we see many di8nosaurs like Ceratosaurus have such bone in their snout, it is difficult that imagine it as a device for show off. for such action, we do not need to a hard bone...please see our nose. it is enough. therefore, I imagine, such bone add more place for muscles ...maybe for having a powerful bite? even I imagine Spinosaurus sail or Dimetrodon sail help to power of bite. probably, their skull have a problem for a powerful bite that exsit such parts solve this problem. it is just my opinion without any document for prove it. What is your opinion?


Other member of this family:

Kileskus aristotocus(Averianov et al. 2010)
Holotype: ZIN PH 5/117

Proceratosaurus bradleyi(Woodward, 1910/ Huene 1926)
Holotylpe: NHM R 4860

Guanlong wucaii (Xu et al. 2006)
Holotype: IVPP V14531

Sinotyrannus kazuonsis (JI  et al. 2009)
Holotype: Kzv 001
theropod1's avatar
Hi, I’m not Scott Hartman, but perhaps this is of interest to you:
Rayfield (2011) included the skull of _M. jiangi_ in her 2D Finite Element Analysis of tetanuran skulls and also tested the impact the crest had on cranial stress patterns. It turned out that this region experienced very little stress, both in the original configuration and in an altered model that saw the crest removed. This suggests that whatever the role of this structure was, it wasn’t to reinforce the skull against biting stresses, since we’d expect reinforcement to be where stresses without it are high.

That is not wholly unexpected, since generally among theropods it’s only tyrannosaurs in which biting stresses culminate prominently in the nasals (which are fused and reinforced), while that isn’t the case in carnosaurs or coelophysids (Rayfield 2005).

–––References:
Rayfield, Emily J. (2005): Aspects of comparative cranial mechanics in the theropod dinosaurs Coelophysis, Allosaurus and Tyrannosaurus. Zoological Journal of the Linnean Society 144 pp. 309-316
Rayfield, Emily J. (2011) Structural performance of tetanuran theropod skulls, with emphasis on the Megalosauridae, Spinosauridae and Carcharodontosauridae. Special Papers in Palaeontology 86 pp. 1-13
ScottHartman's avatar
Thanks - Emily's stuff is generally really great, and this is not an exception.
theropod1's avatar
Definitely agreed!
Teratophoneus's avatar
Personally I always thought of Monolophosaurus´ crest to funtion in similar matter to a  modern cassowarys crest, for display and for pushing plants away when moving through dense jungle
X-StreamChaos's avatar
Yes! An up-to-date Monolophosaurus skeletal reconstruction!
Teratophoneus's avatar
this has alway been one of my favourite theropods, love the reconstruction, I always thought it ued its crest like modern cassowarys do-for display but also for pushing plants away when walking in dense jungles.
Manuelsaurus's avatar
As always an awesome job .
I always use your work as a reference for my models.
True-Leveller's avatar
Wow! Looks like a megalosaur, infact that was my first guess when seeing it previewed in my notes.  Much beefier and small-headed than it is often imagined.
ScottHartman's avatar
It looks like very basal megalosaurs - I don't think it looks much like Torvosaurus, or like spinosaurids. And at least one paper did find Monolophosaurus to be a basal megalosaur, so that's not crazy. Most now find it to be more primitive than the megalosaur/avetheropoda split, down there with Chuandongocoelurus, Sinosaurus, and even Cryolophosaurus (depending on the study). As I mentioned above, it now looks eerily like Sinosaurus to me - even the thick, narrowly double-crests of Sinosaurus are only narrowly separated and highly ornamented/pneumatized. 
TKWTH's avatar
Speaking of Sinosaurus, have you ever considered doing a skeletal for it?
ScottHartman's avatar
Yeah, it's on the short list of skeletals I'd like to do personally, but I rarely get to do skeletals due to personal preference these days.
TKWTH's avatar
Fair enough.
True-Leveller's avatar
I was thinking a bit of Megalosaurus, and, first and foremost, of Marshosaurus. Which would fit with basal megalosaur, but I can also see Sinosaurus.
Kazuma27's avatar
Lower head than usually portrayed, must say, and quite allosaur-ish too... So this guy was a megalosaur of some sort, a basal carnosaur or...?
ScottHartman's avatar
You mean a lower head than my ancient (but often used) previous skeletal? Because it's taller than Brusatte et al's (2010) reconstruction. I don't personally see much allosaurish in it anymore - the trunk is longer and lower, the neck is straighter, the pelvis is much more primitive, etc. Some have suggested that it was a basal megalosaur, but most now recover it as more primitive than the megalosaur/avetheropoda split, down near say Sinosaurus (which I actually find it surprisingly similar to, even in the skull).
Kazuma27's avatar
Yeah, i meant your previous skeletal :)

Interesting that they recovered as an even more basal form... Close to Sinosaurus, ya say? Wasn't Sino a dilophosaurid of some sort?
ScottHartman's avatar
It was suggested to be very close (it was even informally referred to as "Dilophosaurus" sinensis) but I think it's pretty much unanimous that it's a basal tetanuran. So you have coelophysoids like Tawa, Coelophysis, and Dilophosaurus (some think it's a true clade, others that it's successive outgroups). After that it splits into Ceratosauria and Tetenurae, and Sino, Monolopho, and a few others seem to be close to the base of Tetanurae (and soon after that is the split between megalosaurs and avetheropodes, so the fact that basal megalosaurs look like Monolophosaurus isn't really too surprising).
anonymous's avatar
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