Neural crest cells..

[kinyonga]

Filling in the phylogenetic gaps: Induction, migration, and differentiation of neural crest cells in a squamate reptile, the veiled chameleon (Chamaeleo calyptratus) ...

https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/dvdy.38

 

[TayloredExotics]

Whoa! Not the main topic of the article, but this is great information!
"Veiled chameleon embryos were previously thought to undergo an extensive period of diapause. However, it is clear that pre-gastrula stage veiled chameleon embryos do grow continuously, albeit at a slow rate for approximately 60 days during which time they gastrulate."

(I needed to look up the definition: according to biologydictionary.net "Gastrulation is the process during embryonic development that changes the embryo from a blastula with a single layer of cells to a gastrula containing multiple layers of cells")

I assume this is the part when the embryo fuses to the side of the egg, after which the egg cannot be turned/moved much for fear of killing the baby:
"In the egg, the developing embryo is initially positioned against the shell, with its ventral side facing the yolk...
By approximately 70dpo, ..., veiled chameleon embryos initiate the process of turning to their right side, starting with the cephalic region. This is the first morphologically apparent evidence for a break in left-right asymmetry. The embryo continues to fully turn to its right side, such that its left side becomes positioned against the yolk" (shortened for clarification).

 

[kinyonga]

@TayloredExotics ...I had to look up a few words/terms!
I found it interesting that the embryo turned too...but I'm not sure that turning the egg would kill the baby starting at this point. I'd like to find an article that proves or disproves that.

 

[Lindasjackson]

Interesting!

 

[TayloredExotics]

@TayloredExotics ...I had to look up a few words/terms!
I found it interesting that the embryo turned too...but I'm not sure that turning the egg would kill the baby starting at this point. I'd like to find an article that proves or disproves that.

Good point, I was more referring to the generally accepted statement that turning an egg (reptile, anyway) past a certain stage of development is likely to kill the embryo. Although bird eggs (at least the species I'm familiar with) have to be turned with regularity to prevent the chick from sticking to the shell...

 

[kinyonga]

Eggs laid in the ground and buried never (hopefully) to be disturbed until they hatch, would be expected to remain in one position...but eggs laid in a nest with the parent/parents going in and out of the nest, I wouldn't expect to remain in one position.