Body Wall Hairs are short, fine (longer in winter), implanted singly and associated with copious sweat glands.
Only mane and tail hairs are longer.
The eyelashes are long, and bristles are present on the snout.
The panniculus carnosus is very well developed. Skeletal System The vertebral formula is: seven cervical, 18 or 19 thoracic, 5–6 lumbar, 5–6 sacral and 15–20 caudal vertebrae.
There is no clavicle.
The skull is elongated preorbitally, but shortened postorbitally (Fig. 58.2).
The orbit is ringed by bone and is tubular.
The nasal passages are elongated and incompletely separated by the vomer.
The turbinal bones—one maxillary and one ethmoid—are simple and 3 58.
EQUIDAE Figure 58.1.
External features of the Donkey, a typical equid.
The long face bears prominent mobile nostrils and lips.
The snout is hairy, without a naked rhinarium.
The prominent eyes are well-placed on the side of the head for allround vision and the ears are conspicuous, mobile and pointed.
The mane extends down the dorsal midline from between the ears to the withers.
The spine is prominent between withers and sacrum.
From the loins to the tailroot, the region called the croup or crupper, the profile slopes down at a 30– 45° angle, straight and bony in the Donkey, more rounded (unless malnourished) in the Horse.
The body bulges out to the sides below the spine.
The tail of the Donkey is tufted; in Horses the tail is enclosed in long hair from the root. (© Environment Australia) [K.
The nasal bones are long and taper anteriorly and their free ends do not reach as far forward as the incisors.
The premaxillae are large, containing the incisors, with a long ascending branch that borders the anterior margin of the maxilla on either side of the nasal aperture and sutures with the nasal bone.
The bilateral frontal, superior and inferior maxillary, sphenoidal and ethmoidal sinuses are large.
The superior temporal lines are very prominent, but usually do not unite to form a sagittal crest.
However, a very prominent nuchal crest is formed. Locomotion The whole axis of each limb runs through digit III (Fig. 58.3) – only the proximal ends of digits II and IV remain as splint bones and no trace remains of digits I and V.
The femur has a third trochanter.
The ulna is fused partially with the radius, the fibula partially fused with the tibia.
The hoof is cylindrical, folded inwards behind, obliquely truncated at the base, with a separate keratinised sole 4 58.
EQUIDAE 30 mm Figure 58.2 Skull of Equus. (© ABRS) [S.
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