Diverse Headgear Of Hoofed Mammals Evolved From A Common Ancestor

From the small ossicones of a giraffe to the gigantic antlers of a moose, they all evolved from the same ancestor but are dramatically different in size and shape due to differences in gene expression

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A diverse array of mammal headgear is on display in the Museum’s Richard Gilder Center for Science, Education, and Innovation as part of the Louis V. Gerstner, Jr. Collections Core. (Credit: Alvaro Keding / ©AMNH)

Cranial appendages, or “headgear,” come in many different shapes and sizes in ruminant mammals. In the fossil record, antlers, horns, and similar growths were first seen on ancestral ruminants in the Cervidae family — deer, bison and their relatives. Where did this fancy headgear come from? Was there just one common ancestor, or many, that gave rise to all the ruminant mammals that grow such a vast array of bony headgear?

“Horns and antlers are incredibly diverse structures, and scientists have long debated their evolutionary origins,” said the lead author of a new study, paleontologist Zachary Calamari, an assistant professor at Baruch College and the CUNY Graduate Center and a research associate at the American Museum of Natural History.

Although these bony growths are collectively known as ‘headgear,’ biologists use different names for them because their tissue composition and growth patterns are distinct to each taxonomic family (Figure 1).