A Comparison of the Skulls of a Lion and Horse

An animal’s skull is a highly diversified part of the body. It has evolved over thousands of years to suit the creatures eating habits, sensory organs, teeth and many other systems. Because of this skulls of different animals vary wildly, particularly those who have different diets. The most notable feature when first looking at a horse’s skull is their teeth. They have a large gap between their incisors (canines in males) and molars. This is called the diastema or interalveolar margin and creates a space where food can be held before chewing. The molars of a horse are large and flat; they enable the animal to grind down forage. They have ridged surfaces which give the tooth a higher surface area and allow forage to be grinded against the ridges. The large cropping incisors at the front of the mouth allow the animal to cut food such as grass. Horses have 24 molars and 4 premolars.

The canines in female horses are usually absent or may not develop at all, but male horses do usually have them. This is because they are herbivores and therefore don’t eat meat. This means that they do not need the sharp canines to kill and animal/tear away meat from the carcass. Canines are present in males as they will use them for fighting. From this, we can assume the horse is a male.

The zygomatic arch, commonly known as the cheek bone in humans, is the bone that joins the maxilla to the squamous temporal bone (flat bones next to the ear.) The size and shape of the zygomatic arch will determine how much bite pressure the animal will have. As can be seen, horses have a relatively short and thick arch. If the zygomatic arch bows away from the skull we can determine they have a large bite force as there is more room for muscle to contract. However, the zygomatic arch in a horse is relatively close to the face which means there is not much room for muscles and they therefore have a relatively weak bite force and use these muscles mostly for chewing. The relatively short distance can be seen. The parietal bones meet and create the sagittal crest. In horses there is no upwards extension which means there is not a large connection for the muscles that increase bite pressure. This again indicates the horses weak bite force.

The large maxilla bone shows that horses do a lot of chewing/grinding. We can tell this due to the fact that there is a large area of bone for the masseter muscles to attach to. Horses have small auditory bulla relative to the size of their heads which indicates they do not have an impressive hearing range. This is normal with herbivores as they only need to listen out for predators and communicate with other animals. A horses hearing is comparable to that of a humans. They eye orbits of a horse are located at the side of the skull. This means that they have monocular vision. Horses therefore have a large visual field (roughly 340°) so that they can see more of their environment and run away from predators. However, they will not have depth perception or 3D vision. The orbit size is relatively small when compared to the rest of the skull. This is because they don’t rely as heavily on sight as some animals – such as those that need good night vision. Horses rely more on smell than nearly any other sense. Because of this, their noses are extremely well developed in order to allow them better olfactory senses. They have a very long nasal passage, best seen on figure 1 and figure 3. The nasal passages of the horse have two spiralling turbinate bones on either side. This increases the surface area that inhaled air is exposed to, meaning that the sense of smell is enhanced.

Lions are carnivores, meaning that they need to kill their prey and be able to remove meat from the body. Their large canines as seen in figure 4 and 5 help them to do this. The rest of their teeth are sharp and pointed; this is because they do not need to chew foods such as grass so don’t ‘grind’ their food. Their back teeth – carnassals- instead fit together like scissors in order to cut flesh.

The zygomatic arches of the lion extend out quite far. From this we can tell that they have room for large muscles to contract, allowing them to have more pressure in their bite. Also, as seen in figure for their sagittal crest extends upwards which leaves more room for muscle attachment, further supporting the fact that their bite pressure is massive.

Lions have binocular vision – the eyes are at the front of the head – causing 3D vision and depth perception but a lower field of view. This helps them to detect prey. The eye orbits are extremely large when compared to other features of the skull. Lions need eyes this large due to the fact they have extremely developed eyesight – including vision at night. The auditory bulla are not excessively large as seen in figure 7 - roughly a quarter of the size of the eyes. The ears can swivel in order to enhance their hearing further. Hearing is still very important as they need it for both hunting and socializing, however their eyesight is much more developed than their hearing. The turbinate within the nose are elaborately scrolled and fold over themselves. This gives them a much higher surface area for sensory receptors. A close up of this can be seen in figure 8. They have an elongated nasal cavity.

These two skulls differ in many ways. This is mainly due to the fact that one is herbivorous and the other is a carnivore. This means that they have different needs as one needs to avoid predators and the other needs to catch prey. We can see that lions have much sharper teeth than that of the horse. This is because lions don’t need to chew or grind their food down. It is simply cut into pieces and swallowed. Also, lions need more developed canines in order to kill their prey. Horses have small or no canines as they will only use them in fighting and are not intended to kill.

Lions have a significantly higher bite pressure. They have much more space for muscle attachment on their sagittal crest as it extends upwards whereas it does not on the horse skeleton. However we can see that the horse is much better t chewing by the size of their mandible. It is also noticeable that the zygomatic arch of the big cat bows out much more than that of the horse in order to make room for these muscles. There is a massive difference in the eye orbits of these two skulls. The horse has eyes on the side of its head, whereas the lion has them on the front. The lion also has much more developed eyes as they rely on them more than the horse as they need to use them to locate food.

Both of these animals have relatively large auditory bulla. They both have a good sense of hearing and need this as they are both social animals. This helps them to communicate with others but will also be used for defence and hunting. The noses of each animal are very well developed. Although the horse’s nasal passage is longer, it is worth noting that the lions is also elongated. They both have some degree of scrolling of the turbinate bones within the nose which give them a better sense of small. The horses however are more spiralled which gives them a better sense of smell that that of the lion. Overall, we can see that although this skulls are used for different functions they still have the same basic structure and each animal has evolved in order to better suit their environment/lifestyle.