MUIRHEAD`S MYSTERIES: Snakes with three heads

It is well known that snakes can turn up with two heads, what is much less well known (including by myself until yesterday) is that very very occasionally snakes with three heads are born!

I typed in the phrase "snakes with three heads " in the Geneaologybank.com database on September 10th and six examples turned up using that phrase. I reproduce some of them below. The first example is from the Jeffersonian (Stroudsburg, Pennsylvania) of July 7th 1853, the one below that is from the Mirror and Farmer (Manchester, New Hampshire) of Jan 23rd 1858. Robert Twomley, an American herpetologist who also happens to be a Facebook Friend, passed on the following information to me:"The Aberrancy of two heads within snakes is scientifically referred to as axial bifurcation, dicephalism and somatodichotmy. Axial bifurcation is not unfamiliar within herpetofauna. The first known example of axial bifurcation within Reptilia is of a 120 million-year-old Choristoderm (semi-aquatic diapsid) fossil found within the Yixian formation of Northern China. With the earliest known example in historical times been"

"The Aberrancy of two heads within snakes is scientifically referred to as axial bifurcation,  dicephalism and somatodichotmy. Axial bifurcation is not unfamiliar within herpetofauna. The first known example of axial bifurcation within Reptilia is of a 120 million-year-old Choristoderm (semi-aquatic diapsid) fossil found within the Yixian formation of Northern China. With the earliest reliable reports in historical writing, history was documented by Aristotle in BC 350 and Aelianus in BC 250."

Eleven possible cause has been proposed for the condition of axial bifurcation. 

1. Incomplete division of a simple embryo 

2. Partial fusion of two embryos.  

3. Abnormally low or high temperatures during incubation or gestation. 

4. May occur due to regeneration after an embryonic lesion 

5. Anoxia (low oxygen supply) during embryonic development 

6. Toxic effects of metabolic secretions during a prolonged sojourn in the oviduct 

7. Inbreeding depression from a small gene pool 

8. Hybridization 

9. Environmental pollution 

10 Chemical toxins in captivity (1)

1. E-mail from Robert Twomley and Facebook message, September 3rd 2017.