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Orbit Size Does Not Always Equal Eyeball Size

Thursday, February 9, 2017 11:58
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(Before It's News)

Earlier we looked at the two-part orbit of Baphetes and Megalocephalus. I put forth a ‘shifting eyeball’ hypothesis, but I don’t buy into it, just to set things straight. I think the eyeball was in the dorsoposterior, more rounded portion. As we saw even earlier, basal tetrapods were evolving rostral loss of bone. So that sort of thing happened then.

Today we’ll talk about
an extreme case of tiny eyeball and enormous orbit.

Andrias davidianus (Blanchard 1871; 1.8m in length; extant) is a sister to Rana, the bullfrog and derived from a sister to Gerobatrachus. The jugal is absent. The orbit is much larger than the eyeball.

Figure 1. Skull of Andrias with skull bones identified. The jugal is absent. This extant amphibian has a tiny eyeball.

Images of the living
Andrias can be found here. You’ll be lucky if you do see the eyeball. It is very tiny. I probably overemphasized the size of the eyeball in figure 1.

References
Blanchard É 1871. Note sur une nouvelle Salamandre gigantesque (Sieboldia Davidiana Blanch.) de la Chine occidentale. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences. Paris 73: 79.



Source: https://pterosaurheresies.wordpress.com/2017/02/10/orbit-size-does-not-always-equal-eyeball-size/

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