Introduction to Skulls

Skull Features to Look for

While there is great diversity in skull morphology across the animal kingdom, many skull structures are present in a variety of species. These physical features are often related to behavior and ecology. Studying connections between these features, behavior and ecology in extant species is valuable research that informs theories on the behavior and ecology of extinct species. Some common skull structures are listed below - scroll down for tips on how to "read" a skull to learn basic information about the species from which it came.

Foramen magnum

This is the hole near the base of the skull which allows the spinal cord to connect to the brain. The location varies based on the skull's orientation to the spine and indicates locomotive patterns.
- - Hole on the underside of the skull: The head is balanced over the shoulders, like in animals that walk upright (bipedal).
  - Hole on the back of the skull: The head is held in front of the body, like in animals that walk on all fours (quadrupedal).

Human skull

foramen magnum centrally located under brain case

Male gorilla skull

foramen magnum located under back of brain case

Amur tiger skull

foramen magnum behind brain case

Mandible (lower jaw)

While the maxilla (upper jaw) is usually fused with the other bones of the skull, the mandible is often a separate structure connected to the rest of the skull by connective tissues (muscles and ligaments) that allow variable movement for chewing.
Snakes have a split mandible connected in the center by a ligament that enables the lower mandibles to move and expand laterally as well as vertically.

Python

split mandible

Orbits (eye sockets)

Carnivores: Usually forward-facing, providing improved depth perception for pursuing prey
Herbivores: Typically on opposite sides of the skull, providing a nearly 360-degree view of their surroundings to look out for predators.
Primates: Forward-facing, providing improved depth perception for locomotion

Amur tiger skull (front view)

orbits fully visible

Amur tiger skull (sideview)

orbits partially visible

Warthog skull (front view)

orbits not visible

Warthog skull (side view)

orbits fully visible

Male gorilla skull (front view)

orbits fully visible

Male gorilla skull (side view)

orbits not visible

Sagittal crest

This ridge along the center of the top of the skull creates room for jaw muscles to attach at the top of the skull, allowing for increased bite power.
A sagittal crest is typically found in primarily carnivorous species but may be present in other species as well, such as large primates with pronounced sexual dimorphism (e.g. gorillas, orangutans, baboons).

Human skull

no sagittal crest

Amur tiger skull

sagittal crest present

Male vs female gorilla skull

prominent sagittal crest in males only

nuchal crest present in both sexes

Teeth

Teeth can tell us about the diet of a species as well as the age of an individual.
Carnivorous mammals:
- - Long, sharp front teeth ideal for puncturing and shearing
  - Premolars with multiple ridges that fit together like scissors. This allows them to rip through muscles, tendons and even bones.
  - In most species, there are no gaps between teeth.
Insectivores:
- - Mostly fine, needle-like teeth
Herbivores:
- - Broad, flat molars ideal for grinding vegetation
  - Some have chisel-like front teeth for getting into tough seeds
  - Usually a gap between the front and back teeth
Carnivorous reptiles:
- - Usually all canine-like teeth of various sizes
  - They can catch and hold onto their prey, but they can't easily rip it apart, so they often swallow it whole or in large chunks.

Giant panda

large canines, no gaps

(herbivorous carnivore)

American alligator

all canine-like teeth

(carnivorous reptile)

White-tailed deer

gap between front teeth and molars

(herbivore)

Zygomatic arches

These are the bones that arc from the cheek area toward the ears.
The jaw muscles which connect the lower jaw to the rest of the skull attach here.
Larger, more prominent arches provide more attachment points for the muscles and are found in species that either use their teeth for defense or have tough diets that require lots of chewing or forceful biting.

Amur tiger

exceptionally wide zygomatic arches

Western lowland gorilla (female)

moderately wide zygomatic arches

White-tailed deer

narrow zygomatic arches

Identifying Natural vs. replica skulls

You can usually tell if a biofact is natural or a replica by examining the color, texture and teeth.

Antlers VS. Horns

Antlers and horns serve similar functions but are different in structure. In many species, only males grow horns or antlers, but there are several species where they are present in both sexes.

Antlers

Grow from bony supporting structures called pedicels that grow from the skull.
Go through seasonal growth patterns following hormonal changes. Typically, a surge of hormones in the spring triggers growth while a decrease in hormone production in winter causes them to fall off.
Antlers begin with high water content, but as they grow are covered with skin and soft hair called velvet. The velvet carries blood vessels and nerves.
Near the end of the annual growth cycle, the bone becomes more compact and the velvet dies. Most animals will remove it by rubbing their antlers on things in the environment (trees, vegetation, etc.). This is when antlers are stained and take on a woody appearance.
The antlers fall off after a decrease in hormones causes the pedicels to lose calcium.
Individuals are usually without antlers for a few weeks in late winter until the growth cycle begins again.

Horns

Composed of a bony core covered with a sheath of keratin. Neither are shed.
In many species, horns never stop growing.
Horns begin as small, bony growths in subcutaneous (under the skin) connective tissue, possessing their own center of ossification and fusing secondarily to the skull bones.
Horns are almost never branched.

Resources for Further Learning

California Academy of Sciences - View and interact with 3D scans of skulls from a variety of species
Animal Diversity Web: Differentiation of Teeth in Mammals

References

Ashton, E. & Zuckerman, S. (1956). Cranial crests in the anthropoidea (Summary). Journal of Zoology, 126(4), 581-634. https://doi.org/10.1111/j.1096-3642.1956.tb00454.x
BBC Wildlife. (n.d.). How to identify mammal skulls. Retrieved 24 August 2021 from https://www.discoverwildlife.com/how-to/identify-wildlife/how-to-identify-mammal-skulls/
Bies, L. & Myers, P. (n.d.). Horns and Antlers. Retrieved 24 August 2021 from https://animaldiversity.org/collections/mammal_anatomy/horns_and_antlers/
California Academy of Sciences. (n.d.). Skull Stories. Retrieved 24 August 2021 from https://www.calacademy.org/skull-stories
Laden, G. (2009). Why do some females have horns? Retrieved from https://www.smithsonianmag.com/science-nature/why-do-some-females-have-horns-17847645/
Whitson, M. (n.d.). Animal Adaptations: Hominid Skulls. Retrieved 24 August 2021 from https://www.nku.edu/~whitsonma/Bio120LSite/Bio120LReviews/Bio120LHominidRev.html
Whitson, M. (n.d.). Animal Adaptations. Retrieved 24 August 2021 from https://www.nku.edu/~whitsonma/Bio120LSite/Bio120LReviews/Bio120LAnimalRev.html

Updated October 2021

Page updated

Report abuse