|Limerick written by Annie Simminger about her nephew,|
Richard Marshall Eakin, and published in his 1983 book The Third Eye.
Eakin and Robert C. Stebbins performed and published many
experiments on the structure and function of the third eyes of lizards
Well, they're not nostrils. I don't think this has been scientifically evaluated before but maybe sensory related. Let's ask @SssnakeySci. https://t.co/uwfvdLuYwI— David Steen, Ph.D. (@AlongsideWild) January 17, 2017
|Parietal eye (black outline) and parietal scale (white outline)|
of Liolaemus bisignatus (Philippi's Tree Iguana).
From Labra et al. 2010
|The "chimney-like" pineal foramen of|
the extinct 3-foot-long 250 million year old
South African fossil therapsid Hipposaurus.
From Haughton 1929
|Endocast of the brain of the dog-sized 250-million-year-old|
dicynodont Lystrosaurus, the "humble badass of the Triassic",
showing the large parietal eye (dark structure at the top).
From Edinger 1955
|Paired parietal foramina in the parietal (ptl)|
bone of a Banded Krait (Bungarus fasciatus)
skull. From Scanlon & Lee 2004
|Developmental origins of the parietal ("median") eye and the lateral eye.|
The cilia are cellular structures that normally function for movement
(e.g., of debris out of the nose, of water over gills, of eggs into oviducts,
of sperm cells to the egg). In the eye, they have evolved into photoreceptors.
|Diagram of the lizard parietal eye|
From Solessio & Engbretson 1993
|Comparative morphology of the pineal complex in A) lamprey,|
B) frog, C) lizard, and D) human. From Edinger 1955
|The parietal eye of a Western Fence Lizard (Sceloporus occidentalis)|
C = cornea; CC = connective tissue; L = lumen;
LS = lens; PN = parietal nerve; R = retina
Light micrograph from Eakin 1970
|Parietal spots of a Copperhead|
|Dorsal view of a Copperhead skull, from DigiMorph|
|Pigmented apical pits of a ratsnake|
1 The function of vitamin A in eyesight was the basis for a WWII propaganda campaign that eating more carrots could improve human night vision. Although it's true that carrots and vitamin A are essential for good eyesight, the extent to which eating more carrots can improve a person's eyesight was apparently greatly exaggerated in 1940 to create a cover story for the novel abilities of Allied pilots to pinpoint Axis fighter jets at night, which in reality was due to on-board Airborne Interception Radar (although there is in turn some disagreement among historians as to how purposeful the deception was and how much both sides knew about the other side's radar capabilities).↩
2 Melatonin is synthesized from the amino acid tryptophan, which is the origin of another common myth: that eating a ton of turkey causes you feel sleepy.↩
3 Tilly Edinger was among the very last scientists of Jewish ancestry to leave pre-WWII Germany. A 1938 letter to the U. S. State Department in support of her immigration application from George Gaylord Simpson read "She is a research scientist of the first rank and is favorably known as such all over the world. She is everywhere recognized as the leading specialist on the study of the brain and nervous system of extinct animals and on the evolution of the gross structure of the brain. She is so preeminent in this field that she may really be said to have created a new branch of science, that of paleo-neurology, a study of outstanding value and importance”. She was the first female president of the Society of Vertebrate Paleontology, and authored over 1200 scientific papers and books, many sprinkled with sharp-witted, humorous phrases and observations. Her pioneering work in paleoneurology is well-chronicled here.↩
4 During embryonic development, the parietal eye and the pineal organ form together from a pocket formed in the brain ectoderm. The ancestral state is presumed to have been a possibly paired photosensory organ, as seen in extant lampreys. The parietal eye and the pineal gland of tetrapods are probably the descendants of the left and right parts of this organ, respectively. Some Devonian fishes have two parietal foramina in their skulls, suggesting an ancestral bilaterality of parietal eyes.↩
5 Crocodilians and some tropical lineages of mammals (some xenarthrans [sloths], pangolins, sirenians [manatees & dugongs], some marsupials [sugar gliders]) have lost both their parietal eye and their pineal organ. All amphibians have a pineal organ, but some frogs and toads also have what is called a "frontal organ", which is essentially a parietal eye. The word "pineal" comes from the shape of the human pineal organ, which resembles a pine cone.↩
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