EDIT: Well this sucks. Sorry Fellefan this may not be as detailed as it was going to be because I accidently closed down that tab after I'd spent an hour typing up info on horse anatomy. :'C
So let's try this again.
1. "Straighter nose (your's was more like an Arabian's nose)". Remember that all horses come in different shapes and sizes. It's the inevitable part of different breeds and personalities but some are more definable than others. See when you drew your redline your horse had a more bent top and more flared nostrils to a degree. This is a lot like an Arabian's characteristics. Here is a good example of that. And another. I find most horse breeds have a longer nose BUT not straight all the way through. That gives it more of a reptilian/dragon look that you probably don't want. Horses have eyebrows of some sort just like use that affect the way their face is shaped when you look at a side profile.
Another thing you should notice is the big, I think it is a jaw muscle, that is right under the eye. There is a heavy bone and muscle mass there. Make sure you show all of that mass.

2. "Remember that a WELL ridden horse has more of an arch in their back". This is usually true. Remember that all horses are different. But just think, if you were ridden hard throughout your whole life your spine would become pretty misshapen. I have seen this fact many times, especially on this one horse at the barn I ride at. She is in her 30's and has such an arched back it almost looks painful. Spines can easily be misshapen by posture and such. Draft or work horses tend to have this as well from pulling such heavy loads back and forth. Here is an example of an arched back on a horse from being ridden and worked.
Also Wild horses tend to have less of an arch such as this horse I drew because of never being ridden or pulling anything.

3. "Horses have big butts". It is the inevitable truth! Horses have rather large bottoms. Granted, this differs from breed to breed but most horses do have this characteristic. Take for example the Quarter Horse. That horse is actually known pretty well in the horse community for its big bottom. x3 Here is an example of a one of the guys. Do you see?

4. "Rounded stomach". Horses do have more rounded stomachs than most animal. Take into count the Shetland pony. That adorable little pony is very rounded. Look and see. See what I mean? Horses have this because I mean look at them! Unless they are a Racing horse that has a lot of fast exercise they don't burn off ALL the food they eat. Most horses are built big like this, it's just part of their anatomy.

5. "The neck twists around so show it with lines". Horses have different muscles that do different functions just like use. When they twist around to look different ways, different muscles tend to bulge while others relax. For an example of this look here. BUT still look at the image. Did you notice that, that horse can't even twist its neck around as far as you and I drew it? Horses necks don't bend as well as we think they do. I mean you just sit there and turn your head. Can you bend it all the way backwards?

6. "Extra tid-bits."
BULK.
Horses have BULK.
This is the utter truth horses are bulky with either fat or muscle. What I am particularly referring to is the shoulders and back leg muscles. They are big and strong. They have to be like this to support heavy loads and their own bodies. Check out this photo for example. Look at how big that Draft's shoulders are! They contain a lot of mass. I haven't even drawn all the mass most horses have in my Blackline.

So I hope this helped. I know that is a lot of reading but at least I explained the anatomy better. ^^' If you've got any questions just ask. Remember, you can use lots of reference photos for there are a LOT of them out there! People are always taking reference photos, especially of horses. I prefer looking on deviantart because you can find a lot of junk on the regular Google search engine.
Blackline and little illustrations (C) me
Original redline (C) Fellefan
Refs: 1 2 3 4 5 6 7 8 9
So let's try this again.
1. "Straighter nose (your's was more like an Arabian's nose)". Remember that all horses come in different shapes and sizes. It's the inevitable part of different breeds and personalities but some are more definable than others. See when you drew your redline your horse had a more bent top and more flared nostrils to a degree. This is a lot like an Arabian's characteristics. Here is a good example of that. And another. I find most horse breeds have a longer nose BUT not straight all the way through. That gives it more of a reptilian/dragon look that you probably don't want. Horses have eyebrows of some sort just like use that affect the way their face is shaped when you look at a side profile.
Another thing you should notice is the big, I think it is a jaw muscle, that is right under the eye. There is a heavy bone and muscle mass there. Make sure you show all of that mass.

2. "Remember that a WELL ridden horse has more of an arch in their back". This is usually true. Remember that all horses are different. But just think, if you were ridden hard throughout your whole life your spine would become pretty misshapen. I have seen this fact many times, especially on this one horse at the barn I ride at. She is in her 30's and has such an arched back it almost looks painful. Spines can easily be misshapen by posture and such. Draft or work horses tend to have this as well from pulling such heavy loads back and forth. Here is an example of an arched back on a horse from being ridden and worked.
Also Wild horses tend to have less of an arch such as this horse I drew because of never being ridden or pulling anything.

3. "Horses have big butts". It is the inevitable truth! Horses have rather large bottoms. Granted, this differs from breed to breed but most horses do have this characteristic. Take for example the Quarter Horse. That horse is actually known pretty well in the horse community for its big bottom. x3 Here is an example of a one of the guys. Do you see?

4. "Rounded stomach". Horses do have more rounded stomachs than most animal. Take into count the Shetland pony. That adorable little pony is very rounded. Look and see. See what I mean? Horses have this because I mean look at them! Unless they are a Racing horse that has a lot of fast exercise they don't burn off ALL the food they eat. Most horses are built big like this, it's just part of their anatomy.

5. "The neck twists around so show it with lines". Horses have different muscles that do different functions just like use. When they twist around to look different ways, different muscles tend to bulge while others relax. For an example of this look here. BUT still look at the image. Did you notice that, that horse can't even twist its neck around as far as you and I drew it? Horses necks don't bend as well as we think they do. I mean you just sit there and turn your head. Can you bend it all the way backwards?

6. "Extra tid-bits."
BULK.
Horses have BULK.
This is the utter truth horses are bulky with either fat or muscle. What I am particularly referring to is the shoulders and back leg muscles. They are big and strong. They have to be like this to support heavy loads and their own bodies. Check out this photo for example. Look at how big that Draft's shoulders are! They contain a lot of mass. I haven't even drawn all the mass most horses have in my Blackline.

So I hope this helped. I know that is a lot of reading but at least I explained the anatomy better. ^^' If you've got any questions just ask. Remember, you can use lots of reference photos for there are a LOT of them out there! People are always taking reference photos, especially of horses. I prefer looking on deviantart because you can find a lot of junk on the regular Google search engine.
Blackline and little illustrations (C) me
Original redline (C) Fellefan
Refs: 1 2 3 4 5 6 7 8 9

