Carnivore Skulls Evolution in 3D: Photogrammetry in Action

Photogrammetry 

Photogrammetry is a technique that creates a 3D model of an object using many overlapping 2D photos. First, pictures of the objects are taken from all around it to capture all its sides. Then, using a powerful computer, it`s possible to reconstruct the object`s shape and surface in 3D. 

At the Natural History Museum in Oslo, we use a photogrammetry setup that allows us to scan objects safely and accurately. Our setup consists of a shooting tent with lights, a turntable and several cameras. After taking many pictures, we process them into a 3D model, obtaining an accurate digital copy of the object. In our case the objects are skulls in the mammal collection at the museum.

We are using photogrammetry to study the evolution of the size and shape (called morphology) of the skull of some specific mammals, the Carnivores. This group of mostly meat‑eaters includes animals such as bears, cats, dogs and seals. Carnivores can eat other food beyond meat, but they share a similar skull and tooth structure that originally evolved for catching and processing preys.

Skull Morphology of Carnivores

Polar bears (Ursus maritimus) and brown bears (Ursus arctos) are mammals that belong to the order of Carnivora. They split from a common ancestor approximately 0.5 -1.1 million years ago (recently in evolutionary terms) and today they live in different habitats and have adapted to different lifestyles.

Polar bear – the hypercarnivorous of the Arctic

Polar bears are specialists: they are adapted to live in the harsh Arctic environment. They are described as hypercarnivores, meaning that most of their diet is composed by meat.

Brown bear – the generalist feeder

Brown bears are generalists: they can live in many habitats and eat a wide range of foods. They are opportunistic omnivore, meaning that their diet varies, and, depending on the season, it can space from plants, berries and nuts to insects, fishes (such as salmon) and small mammals.

Different lifestyles but similar skulls

Even though polar bears and brown bears have different lifestyles, their skulls show some broad similarities that reveal how closely related they are.

1. Similar cranial morphology: they have a large skull of similar size and shape.
2. Same types of teeth: their typical tooth pattern includes canines, long and pointed teeth for grabbing and tearing flesh.
3. Strong jaws: they are anchored by jaw and neck muscles that allow them to process food.
4. Enlarged nasal region: gives them a developed sense of smell.