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DrScottHartman — Majungasaurus - redux
Published: 2008-06-06 22:39:01 +0000 UTC; Views: 36716; Favourites: 286; Downloads: 0
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Finally! After an eternity of revisions and attempts to reconcile the proportions of specimens of different ages that frequently didn't overlap, I feel confident I've nailed the general proportions.With generous aid from several people ("credits" below) I figured out that the legs weren't actually too short in my original skeletal - in fact I ended up making them too long in my most recent attempt. Instead, the vertebrae and ribs based on UA 8678 (that would be the cervicals, dorsals, sacrals, and 5 anterior caudals) were scaled up too large.
That's an important distinction, as scaling them down had a chain-reaction on the relative size of the head, pelvic and pectoral girdles, etc.
It's still a strange and somewhat low-slung theropod, but nothing like my previous attempts. I should note that there weren't any mathematical scaling errors - rather, the way I chose to reconcile the axial series of UA 8678 to the larger tail and head of FMNH PR 2100 was wrong (the latter has proportionately taller neural spines, which is probably an ontogenetic feature).
Obviously newer data could require some nips or tucks, but I honestly think you are safe to illustrate Majungasaurus now. I know I plan to!
Special thanks (in alphabetical order) go out to Matt Carrano, David Krause, Adam Pritchard, and Scott Sampson, all of whom who provided excellent critiques and made this version possible (not to mention the research and publications the restoration is based on).
Now I'm going to go find a bottle of champagne to pop...
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Comments: 164
Tras ser conocido por numerosos cráneos y esqueletos bien preservados, el Majungasaurus ha llegado a ser uno de los dinosaurios terópodos más estudiados del Hemisferio Sur. Aparentemente estaba más relacionado con los abelisáuridos de la India que con los de Sudamérica o África continental, lo cual tiene importantes repercusiones biogeográficas. El Majungasaurus era el superpredador de su ecosistema, cazando principalmente saurópodos como el Rapetosaurus, y siendo también el único dinosaurio del cual hay evidencia directa de canibalismo.Aunque los brazos no disponen de mucha evidencia, se reconoce que estos eran muy pequeños, mientras las patas eran largas y robustas me gusta.
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En realidad, los brazos y cintura escapular están completamente conocida después de que el Burch y el papel Carrano a principios de este año: [link]
Pero gracias por el comentario!
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Hi Scott! I was wondering if you remember Grillo & Delcourt (2016)? the one about abelisaurid body size, they used a modified version of this skeletal of yours with a bigger head, I originally didn't pay much attention to that but eventually got curious and decided to check against O'Connor (2007) and while I was able to replicate your inter-bone scaling and cross scaling between UA 8678 and FMNH PR 2100 of the dorsals and caudals, I did got a proportionally bigger head like them (and bigger hips) so I think it's worth investigating further if you have free time, perhaps I'm missing something.
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Maybe ask again in the fall, I don't have time to dig back into this right now. I can say that I ended up working with several of the authors and preparators of the material during my last major revision, and we ended up in agreement back in 2012 (including O'Connor).
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i have a quetion. how much would you think a roughly ~7 meter long majungasaurus weigh?
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I really can't say without doing a graphic double integration calculation, but in the ~1 tonne range I would think.
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Almost all predators (and many herbivores and omnivores) have individuals that will engage in cannibalism from time to time, especially in the case of scavenging. We know that some Majungasaurus individuals apparently did the latter, but there's no evidence that Majungasaurus was particularly given to cannibalism, so it didn't seem worth mentioning in my description.
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I doubt there is a single non-cannibalistic predator
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I know, but it's thanks to this dinosaur that cannibalism has been proven in dinosaurs.
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I guess, but that's sort of like saying that finding eggs proves that some dinosaurs reproduced - of course they did. Same with cannibalism, especially in predators.
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I have a theory about its short legs, balance. The shorter legs would lower its centre of gravity.
I heard somewhere its teeth (or skull) were made to hold on to struggling prey, so maybe that's where the need for the balance comes from.
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It certainly lowered the CoG. I'm not sure if the stiffer neck (from the enlarged cervical ribs) would make it better or worse for holding on to struggling prey - but it's an interesting idea.
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Aren't those ossified tendons?
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No, they are enlarged cervical ribs. Now cervical ribs are themselves an ossification of where some of the neck muscles attach, so in one sense developmentally they are, but no more so than any other dinosaur.
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The leg look long, after watching "new spinosaurus."
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This thing has even shorter legs than the new Spino. At least that thing's taller than a person (if barely).
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who would've guessed a 7 meter theropod had shorter legs than a 15 meter theropod?
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Still, it has longer legs.
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Where are its limbs?
*gets out microscope*
Oh, there they are.
Seriously, WTF evolution, reducing this to near limblessness and hen giving it a really weird head?
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Does anyone have an explanation as to why the coracoid is apparently so big in Majungasaurus (and at least some abelisaurids)? What did they need it for?
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Lots of abelisaurids, and there's no widely agreed upon explanation. FWIW the anterior length of the scapula ahead of the glenoid fossa probably supported expanded lower neck muscles, so the expansion of the coracoid area below it may simply have followed along. On the other hand, increased acceleration of the neck may have also necessitated enlarged pectoral and latissimus muscles to counteract it, so perhaps that played a role.
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Not really. They might be used for sexual tickling. Anacondas have claws in their bodies used solely for that purpose. As for the legs, the idea proposed in All Yesterdays sounds really interesting.
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For the short legs and lengthened body, it looks like it would be a great swimmer. With its hands to its side, long neck and tail (which is in line with the rest of the body) it must have been a habitual swimmer, its horizontal gait is similar to a swimming varanid. Who knows how far back the legs can be pulled back. Abelisaurs and their large caudofemoral muscles would make great surface swimmers with their powerful hind leg strokes. Having short legs means less dangling legs (fossilized claw marks indicate that toes were pointed down for theropod swimming and was a problem) which would mean less slow wading.
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Seeing how many abelisaur heads and necks are designed for powerful sustained bite grips, they may have used this at times to drown their prey. As for having rough, armored and uneven scales, crocodilians use this to reduce water disturbance.
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I dont know if this helps, but this is a common problem when dealing with composite skeletons that consist of differing ontogenetic ages. My solution involved the dimensions of the centra of the overlapping portions of the common elements of FMNH PR 2100 and 8678. after everything was at the same scale, i came up with two reduction ratios one was centrum height, one was centrum length. I then superimposed the vertebrae accoding to each parameter and noted what was different, larger, thicker, taller, etc. I ended up going with the cntrum length ratio. I then modified the remaining FMNH PR 2100 vertebrae to backdate them ontogenetically based on the changes seen in the superimposed common vertebrae.
I filled in the space underneath and between the articulations of the haemeal arches, added mass to the tops of the neural arches, and increased the height of the neural spines and their width at the base. This recreates what I beleive would be these vertebrae in the ontogenetic state of the younger animal. Centrum dimensions seem to be more conservative measurements for this purpose than measurements of any other part of the vertebra.
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Yes they are. It's a really strange animal.
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They really were. I can now say that with a bit more certainty than before.
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Then that would mean it couldn't run very fast. Probably not more than 15 mph.
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Perfectly accurate. When you live in a densely forested environment, you don't really need speed or agility.
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You do need agility in such an environment.
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Majungasaurus was a largely built animal with poor vision, yet it was somehow the apex predator of prehistoric Madagascar.
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Who says it had poor vision? Most extant theropods and nearly all the extinct ones had good vision.
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Scientists performed a CAT Scan on the skull of a Majungasaurus and found that the parts of the brain associated with vision weren't as well developed as the rest of the brain. It could see clearly when standing still, but when on the move it would have to tilt its head from side to side in order to keep a straight line of sight. If it was hunting and the prey managed to outflank it, the dinosaur would completely lose it due to having no peripheral vision.
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And when the only prey you have is Rapetosaurus, which is not a fast moving animal either by any means.
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Majungasaurus was an interesting abelisaurid, because his legs were much short, probably, because they ate sauropods, so they didn´t have to run much fast to catch his food, but, other abelisaurids, like carnoturus, could be fast runners, so it makes me thinking what carnotaurus ate...
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it seems that the longer/larger the neck/head is on a predator is, the less necessary arms become.
Needless to say, i feel bad for these guys. If they had an itch on their head, then what? XD
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HMMMMM....what about Saurophaganax, Suchomimus, and the larger neovenatorids?
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Those have much longer arms.
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