George Stubbs
George Stubbs was a British painter from 1724-1806. He is most well known for his incredible paintings of horses, which are arguably the best horse paintings that England had ever seen.
https://www.wikiart.org/en/george-stubbs/mares-and-foals-in-a-river-landscape-1768
However, he was just as outstanding at painting other animals.
https://www.wikiart.org/en/george-stubbs/hound-and-bitch-in-a-landscape
https://pixels.com/featured/the-anatomy-of-the-horse-george-stubbs.html
He was a genius in anatomy which resulted in him becoming a teacher of this subject at a hospital in York. He knew the anatomy of horses so well that he decided to share his studies, and analyze horse anatomy in the form of a book. His book was successful and his horse paintings soon became a hot commodity to rich men who wanted some of their own.
Stubbs was a self taught painter; however, he briefly studied with an artist in 1741. His most famous painting is of a horse being attacked by a lion. He managed to show the frightening emotions of the animals and the power that a lion has over the horse.
https://www.wikiart.org/en/george-stubbs/horse-attacked-by-a-lion
I believe his paintings are truly outstanding. He was so great at what he did because he loved animals so much. He painted them in such a way that you can’t help but see their emotions.
http://www.tate.org.uk/art/work/N04696
For example, in Horse In The Shade of a Wood, the stallion is without an owner and is free, however he looks sad. Stubbs depicts his animals in a way that people can understand them and wonder what they are thinking.
Taken from: https://www.britannica.com/biography/George-Stubbs, https://www.tate.org.uk/kids/explore/who-is/who-george-stubbs, and http://www.artnet.com/artists/george-stubbs/biography