Late tomorrow we look forward to bringing you a Big Project Announcement (well, more of a Big Project Promotion). So, tune in then for more details.
In the meantime, enjoy this new plot of our data. The other day Tor Bertin suggested we take a look at MT III and MC III ratios. So, here’s a chart showing the MT III:tibia ratio versus the MC III: ulna ratio. A few things to note:
- Hadrosaurs are still very, very bizarre. Their MC IIIs are relatively longer than in any other ornithischian.
- The vertical spread in ceratopsians is probably because both small, bipedal forms as well as large, quadrupedal forms are included in that category.
- Basal ornithischians have very long MT IIIs. Is this a consequence of their generally small size?
- We need more thyreophorans (stegosaurs, ankylosaurs, and the like) with MC and MT data! This group, for various reasons, is one of the remaining holes in the data set.
In the interests of full transparency, I deleted the point for for the ornithopod Lurdusaurus arenatus. Its metatarsal III length seems far too small for the size of the tibia. This may be an error in the original paper (I even went back to triple-check it!), or it could be that this taxon has tibia:metatarsal proportions completely unlike any other ornithopod.
Want to See Some Other Plots?
We’re always looking for new ways to present the data on the blog. If you have any requests, feel free to note them in the comments section.
Or better yet. . .don’t forget that the data are freely available to everyone! There is absolutely nothing stopping you from playing with the data yourself. In fact, we encourage it. Odds are quite good that, like many project participants, you’ll pick up something nobody else has noticed yet.
The Open Dinosaur Project 
Hmm… some at-a-glance comments (oh, am I nosy and noisy ;p )
(1) This ratio to ratio graph does not inherently indicate the size of the animal (represented by the dots), however much we subjectively assume.
(2) This graph alrealy substantiates (pending statistical analysis though) that basal ornithischians were bipeds (a distintive cloud of data with elongated hindlimbs and “standard” i.e. plesiomorphic forelimb proportions). I will bet if we enter outgroup data (basal dinosauromorphs, basal saurischians) they will fall in the same field.
(3) Subsequently down the evolutionary paths the quadrupedal condition appeared independently in every sub-clades (as evidenced from fossils) and the MTIII:titia ratio stabilized at around 0.4.
(4) Along the line of tenontosaur-camptosaur-iguanodontid-hadrosaurid evolution there was apparently a punctuation of the equilibrium with a sudden increment of MCIII:ulna ratio. This could be correlated with (if any) the explosion of hadrosaur diversity +/- the appearence of migration capability.
(5) Interestingly, predators took a leap in cursoriality, too. Coelurosaurs esp. tyrannosaurs invented the actametatarsalian pes plus elongated MTIII:titia ratio cf allosauroids. Okay, I sound like Bob Bakker in “Dinosaur Heresies”, but that could be a prey response evolved.
(6) The high vertical spread of ceratopsian may be just that – we’ve artificially lumpsummed a continuum of biped-to-quadruped evolution story into one data group. Anyhow, their MCIII:ulna ratio are quite stable (taking into account the biped to quadruped transition) – which plainly says that they’d like to fight, no flight.
Would like to hear your valuable comments.
A Big Project Promotion? Tomorrow? Really? Not Thursday?
Yes, really tomorrow! Even a broken clock is right twice a day. 😉 (I double checked my email notifications) 🙂
The femur seem to be longer in Ankylosauria than in other clades. Plot femur vs MT III, femur vs. fibula, and femur vs. tibia. (e.g. http://old.oru.edu/cccda/sl/opendino/odp.php?xaxis=Femur&yaxis=Fibula)
Also a scapula vs tibia plot (http://old.oru.edu/cccda/sl/opendino/odp.php?xaxis=Scapula&yaxis=Tibia) shows that Ankylosauria seem to have a different scapula/tibia ratio than other clades.
The radius bone in Theropoda seems to be shorter, see radius vs. tibia and radius vs. MT III. (e.g. http://old.oru.edu/cccda/sl/opendino/odp.php?xaxis=Radius&yaxis=Tibia)
Another interesting thing about Hadrosauridae is that they seem to have shorter humerus/radius, humerus/ulna ratios than other clades (e.g. http://old.oru.edu/cccda/sl/opendino/odp.php?xaxis=Humerus&yaxis=Radius).
Another way to use these images is to note that outliers may correspond to transcription/measurement errors and those entries may need to be checked one more time.
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