From vampires to fruit bats, can examining bat teeth fill evolutionary gaps?

The diverse dental features found among bats might help fill gaps in our understanding of how mammal teeth evolved. 

Scientists from the University of Washington in the US, publishing in Nature Communications, analysed and compared the jaws and teeth of more than 100 noctilionoid bats, revealing the developmental rules that explain the diverse range of dental features.

From early cone-shaped teeth, mammals have evolved to develop four types of teeth – incisors, canines, premolars and molars – each with specific functions for food processing.

Noctilionoid bats – a group which includes the infamous vampire bats – emerged around 45 million years ago. The group rapidly evolved to develop a diverse range of skull, jaw and teeth configurations (including all four teeth classes) tailored according to each species’ dietary requirements. 

Within the group, each species dines on different foods, ranging from fruit, nectar, leaves and seeds to arthropods, small vertebrates, fish and even blood. 

Lead author Dr Alexa Sadier says: “There are noctilionoid species that have short faces like bulldogs with powerful jaws that can bite the tough exterior of the fruits that they eat. Other species have long snouts to help them drink nectar from flowers. How did this diversity evolve so quickly? What had to change in their jaws and teeth to make this possible?” 

To answer this question, the scientists used CT scans and other methods to compare and analyse facial and dental features of noctilionoid bats, including specimens from museum and wild bats. They compared the bats’ facial features with their diets and used mathematical modelling to trace how these characteristics might have developed.

The study reveals bat teeth configurations tend to follow developmental rules, with tooth number and size, based largely on jaw growth. 

Bats with longer or intermediate jaws usually had three premolars and three molars on each side. Whereas bats with shorter jaws had one less premolar, and/ or lost their back molar.

Put simply, “when you have more space, you can have more teeth,” says Sadier.

The authors write that delving into the diverse dentistry among this group of bats, contributes to the limited understanding of the mechanisms behind teeth evolution. It also helps explain how these bats rapidly evolved and diversified to their wildly distinct face, jaw and teeth structures.