Equus

I've added this image later, just because I stumbled across it and
because it's so bizarre (click to enlarge). It's from an 1816 book entitled:
E.D'Alton's 'Naturgeschichte Des Pferdes' from Anna Amalia Bibliothek.
I saw only one other illustration of a skeleton in normal stance.
An earlier edition has interesting schematic sketches.

All the above images are from the 5 volume set:
'Dizionario Ragionato di Veterinaria Teorico-Pratica..'
by Francesco Bonsi, 1795.

'Della Cavalleria' by Georg Engelhard Löhneyss, 1624.

'The Anatomy of the Horse: Finished Drawing of the Muscles
for the Fourth Anatomical Table' 1756-1758 by George Stubbs.

'Anatomia del Cavallo Infermita..' by Carlo Ruini, 1618.

Frontpiece from 'Equile, in Quo Omnis Generis..' by Johanes Stradamus, 1634.
(I'm 99.3% certain this is actually Johannes Stradanus, although he died in 1605
- either this is from a later edition or the engravings are after his drawings)

Frontpiece from 'La Methode et Invention Nouvelle de
Dresser les Chevaux' by William Cavendish, 1658
[published in english as 'A General System of Horsemanship' in 1747]

'Zodiac Horse' from 'Obras de Albeyteria..' by Martín Arredondo, 1704.

'De Humana Physiognomonia Libri IIII' by Giambattista della Porta, 1586.

• These are just a collection of random images sparked off by finding the Francesco Bonsi book. As it turns out, that became the excuse to post a link to the National Library of Medicine's exhibition site - 'The Horse: A Mirror of Man: Parallels in Early Human and Horse Medicine' (including thumbnail gallery page) which went online earlier this year. [The della Porta and Arreondo images come from here]
• The 5 volumes of 'Dizionario Ragionato di Veterinaria Teorico-Pratica..' by Francesco Bonsi are online at Centro Interbibliocario dell'Universita' di Bologna (click 'Accesso al full-text' at the bottom of the page and then choose one of the 5 'Tomo' from the pulldown menu and 'Tav.' from the other sidebar menu for an illustration.)
• It's rather disappointing to find that there are no highish resolution images* online of George Stubbs' famous and extensive portfolio of anatomical drawings of horses. The image above comes from a series of 17 drawings for 'The Anatomy of the Horse', on display at the Royal Academy of Arts. [*Addit: Some of the anatomy drawings can be seen with a zoom box at the Fine Arts Museums of San Francisco] {Artcylopedia}
• Carlo Ruini's 'Anatomia del Cavallo' was the first real treatise on equine anatomy and its illustrations are famed for their eccentric or outlandish presentation. The image above was snagged from the Danish Veterinary Library site. It isn't included with the higher resolution examples from Ruini at the NLM's Historical Anatomies on the Web exhibition. [also see: french exhibition site] [the whole 2 volume book is available in downloadable pdf chunks from Hannover Library but I didn't so can't vouch for the quality]
• The Strandanus 'Equile..' frontpiece is also from the Danish Veterinary Library - a series of naturally posed engravings of the then known breeds.
• The Cavendish frontpiece comes from Lista Oggetti (no other images available).
• The Georg Engelhard Löhneyss engraving, also from the Danish Veterinary Library, is from a series that were inspired by/copied from Carlo Ruini.
• Just to give a vague indication of the enormous body of literature relating to veterinary science, here's a bibliographic list of 5 centuries worth of monographs, journals, pamphlets, manuscripts, archival records, and ephemera, from the Washington State University Veterinary History Collection (they also have gallery pages with small images).
• I've previously posted a link to the Michigan State University Library Rare Veterinary Books exhibition - most of the illustrations are frontpieces.
• Good quality images of some old illustrations of horses by some master engravers.
• Just because I found them: A History of Veterinary Anatomy at Cambridge University (the last large image wouldn't have looked too out of place among the Industrial Anatomy post from the other day); 'The Tao of Horsemanship' Ch. 1 © Dr T Ritter; Farriery articles from (where else!?) horseshoes.com.