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Re: [dinosaur] Psittacosaurus eye in the new "cute" model--how realistic?




Note that more photos of how the model was designed and built can be seen on Bob Nicholls' Facebook page, including additional views of the eye to show the proportions of the sclerotic ring and the enclosed iris and pupil.

https://www.facebook.com/Paleocreations/photos/pcb.938887196217233/938885956217357/?type=3&theater


[The model is fascinating, but it still looks to me as if the reconstructed "big" eye exposes the scleral area over the sclerotic ring surrounding the iris and pupil, making it look a bit "human" (and so "cuter")...]

On Sat, Sep 17, 2016 at 12:05 AM, Josh Cotton <greeni.fire@gmail.com> wrote:
It could be exaggerated, but even from a side view photograph that appears similar to the skeletal drawing it's a huge jump in lens length— from infinite (as skeletal drawings are orthographic) to say, 50mm. That's enough warp in the perspective field to make the eyes and other features look quite a bit bigger while not changing physical size at all. The orthographic skeletal drawing is a great tool for measuring, but a live animal with the same exact measurements will look quite a bit different, its features shifting based on lens length.

On Fri, Sep 16, 2016 at 3:31 PM Ben Creisler <bcreisler@gmail.com> wrote:

This illustration appears to give a sense of the proportion of the inside diameter of the sclerotic ring in a species of Psittacosaurus relative to the orbit and rest of the skull.



The side-on views of the new model seem to show the iris and pupil space as larger relative to the orbit and skull. Since the model is supposed to be an adult I presume, the size of eye looks possibly exaggerated, adding to the "cute" factor. 




On Fri, Sep 16, 2016 at 1:08 PM, Josh Cotton <greeni.fire@gmail.com> wrote:
Hmmm ... Looking at his 2D soft-tissue reconstruction, it looks like he is aware of the way it should work, but on the sculpt, I agree that it does look slightly bigger. I think though that part of this has to do with the very long lens assumed in an orthographic skeletal drawing. Everything in a skeletal is based on the physical measurements so that each element can be directly compared, which makes it superior to a photograph when studying proportions. However, when the same skeleton is dimensionalized, brought into the 3D realm with a human eye (~17 mm) or a camera lens, (any number of lengths) then all of the proportions are warped with perspective. Here's an example in an animated gif of a man's face that cycles through lens lengths to show how proportions change with lens distortion, a la the saying, "the camera adds 10 pounds." You'll notice that as the lens gets longer (approaching orthographic) his eyes seem proportionally smaller as well:
http://1pezeshk.com/wp-content/uploads/2016/07/Camera-Adds-10-Pounds.gif

When considering that an "orthographic" or flat-view skeletal drawing assumes a lens of infinite length, it's no wonder that the proportions of an object seem to change through a lens of any other length than infinite. It's counter-intuitive, but I see this frequently when digitally sculpting reconstructions. When I flip the switch from "orthographic" to "perspective" it looks like a completely different animal.

That's my thought, though to be sure you'd have to go physically measure the sculpt proportions compared with the skeletal drawing.




On Fri, Sep 16, 2016 at 1:40 PM Ben Creisler <bcreisler@gmail.com> wrote:

If you look at the skeletal drawings of Psittacosaurus in one of the photos and in the video, you can see the restored scleral ring. In birds and reptiles, the iris and pupil would be confined to the inside of the ring. The eye in the model appears to have the "iris" extending over the ring, making it larger. The bony ring would be under the sclera, which would be covered. Or am I looking at this wrong?

On Fri, Sep 16, 2016 at 12:32 PM, Matt Martyniuk <martyniuk@gmail.com> wrote:
I was under the impression that the yellow part is the iris. There does seem to be a slightly darker area just around the pupil but it grades into the yellow, indicating it's meant to be pigment variations in the iris. The sclera does not seem to be visible. Or am I looking at it wrong?

The eye does seem large relative to some other reconstructions but I'm not sure of the ontogenetic stage of this specimen. It would be expected in a young subadult.

I'm more confused about the supposed "patagia" behind the legs. Surely that would be filled in with fat/muscle/other tissue of the leg (or even the tissue connecting the femur to the body wall as in most non sprawling tetrapods) and not a simple, pterosaur-like skin flap, right?

Matt

On Sep 16, 2016, at 2:35 PM, Ben Creisler <bcreisler@gmail.com> wrote:


Ben Creisler

Depiction of the Psittacosaurus eye in new model: 

Picture gallery (note parrot eye in one slide)


video



The sclera appears to be shown as almost fully visible in front (as in humans), although virtually all other living tetrapods (including birds, crocodiles, turtles, lizards and mammals (notably non-human primates such as great apes)) have sclera that are covered by soft tissue in the form of eye lids or skin, and so only slightly visible around the edges if the eye moves. In Psittacosaurus (and in other dinosaurs and in birds) the eye was supported by internal sclerotic plates that surrounded the iris and pupil (crocodile and mammal eyes lack such plates).

The "cute" Psittacosaurus model appears to show the sclera (yellowish in color) as visible with the lids around a wide ring rather than exposing only the iris and pupil as in living non-human animals. This gives the dinosaur a "big, round eye" look, a bit  reminiscent of a cartoon baby face. 

Other artistic representations of Psittacosaurus typically show only the iris and pupil as exposed, with the sclera hidden. This covered sclera reconstruction is likely more accurate and gives the dinosaur a more birdlike (rather than babyish) look, maybe not quite as appealing and cuddly
(although the Ewoks of Star Wars fame had typical, sclera-hidden animal-like eyes, a bit like big-eyed waif paintings, which don't show much white around the eyes).

See:


Claims that this Psittacosaurus model is the most realistic depiction of a dinosaur ever may be a bit off, at least regarding the eyes...