Thursday, November 12, 2009

I need help finding information on the horse's chestnut and ergot?

I am in a dinosaur/evolution class and I have a final term paper on a subject of my choice, and I have chosen to write about the evolution of the horse's chestnut as well as the ergot. I also am required to give a presentation on this subject, and I would like to discuss the different theories on the chestnut/ergot...ie caused by prenatal leg fusion, etc. I'd love some of the theories, as well as good places to search for info... since I keep coming up with this crap on the horse chestnut tree. Please don't be rude, or tell me how "bad" evolution is. This is a class assignment and I am just doing my duty. Please don't give me crap! Thanks in advance!!!!!

I need help finding information on the horse's chestnut and ergot?
This website describes it a vestige of a prehistoric toe. But I don't see how that is possible since it is so high on the leg.





http://horses.about.com/od/partsofthehor...





Here is something from another website I found:


The is a horse’s chestnut.





Chestnuts are horny growths located on the inside of a horse's legs, above the knees and below the hocks. The size and shape of the chestnuts are unique to each horse, like fingerprints.





It’s not a blemish or a scab. And no, it’s not a sensor so the horse can see at night,


as the old wives tale. Rather, it’s a remnant of evolution thought to be similar to a pad found


on dogs. Ancestors of the modern horse were four-toed, fox-size animals called Eohippus.


As they got bigger, their legs grew longer and several toes became one.








Essentially, the horse is now walking on its middle finger; the hoof is its fingernail.


Hmm … you know what it feels like to stub your toe. Imagine that being your only one.


Regular maintenance of the horse’s toes is vitally important to its continued health.








For more information about the evolution of horses, visit these Web


sites: http://www.talkorigins.org/faqs/horses/h...





http://www.amnh.org/exhibitions/expediti...








Fun fact: The favorite horses of both Alexander the Great and Julius Caesar both had extra toes.


Source: Nature Genetics
Reply:The first ancestors were five toed, then three toed. I believe the chestnut is the "thumb" and the ergot a "ring" or "pinkie" remnant.


Physically a horses knee is our wrist so the height of the chestnut makes sense that way. Another factor to consider are the splint bones which start just below the knee then taper off usually fusing to the cannon bone. These were most likely the the more recent second and third toes.


Something that is odd in the thumb/chesnut theory is the hind chestunts are also high on the leg but most animals do not have a toe set far from the rest on the hind feet, monkeys are one of the exceptions. In fact many animals have four main toes on the front and a dew claw/thumb and only four toes on the hind feet.


It's amazing how similar a horses leg structure is to our own hands and feet, they have almost entirely the same bones, tendons, ligaments and even arteries.





Have fun and good luck on your assignment. I like your topic choice.
Reply:PRS: It's so high on the leg because if you look at the evolutionary tree of the horse you will see as the metacarpals and carpals fused into what is now the canon bone - the other toes moved up on the leg.


http://www.mun.ca/biology/desmid/brian/B...


(You can see in this image where the lateral digit remnants reside in modern day Equus compared to its ancestors)





This is why the chestnut is close in composition to the hoof of the animal (only not nearly as hard because it doesn't need to be).





Here's an article that argues the viewpoint that these are not vestiges of toes but of sebaceous glands used for scent marking (because they smell similiar to the buildup in male genitalia and around mare's teets).


http://books.google.com/books?id=P1sCAAA...
Reply:The chestnut and the ergot were once toes that evolved.





Chestnut: http://en.wikipedia.org/wiki/Chestnut_(h...





Ergot: http://en.mimi.hu/horse/ergot.html


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