Analysis of Oldest-known Plant-visiting Bat Suggests It Was Omnivorous

by AMNH on

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The oldest known nectar-drinking bat, Palynephyllum antimaster, was probably omnivorous.

A team of evolutionary biologists from the American Museum of Natural History, Stony Brook University, and the City College of New York published their findings in the journal Biology Letters. Their work is based on a new method that allows scientists to estimate skull length, and thus body size, bite force, and diet, from a single fossil molar. The study is the first to provide fossil data showing that the evolution of highly specialized nectar feeding in bats required an omnivorous transition. 

Painting of two Palynephyllum antimaster bats at night, one eating a plant and another trying to eat a bug, in a tree along with a mammal and a bird.
Palynephyllum antimaster bats thrived on a diet of insects and nectar amid the incredible biodiversity of South America during the Miocene epoch.
© M. Hanson

“Oftentimes, all we have to work with in the fossil record are one or two teeth, which can severely limit our knowledge about the behavior of an animal,” said paper author Nancy Simmons, curator in the Museum’s Department of Mammalogy. “But the models presented in this paper show how a single tooth can give us enough information to infer many aspects of what an extinct species was like, including what it ate when it was alive.”

Palynephyllum is represented by two molars, dating from the Miocene epoch and found in La Venta, Colombia, which was home to the most diverse vertebrate fossil fauna known from the mid-Miocene. Twelve million years ago, when Palynephyllum lived, this area of South America was teeming with biodiversity, including several types of bats. 

Feeding exclusively on nectar, which is basically sugar water, is very physiologically demanding and requires special metabolic adaptations.The molars analyzed in the paper are narrow, and their cusps are reduced and flattened, as they are in nectar-drinking relatives of the fossil living today. 

Antimaster tooth
Measurements from this upper molar fossil of Palynephyllum antimaster were used to predict the skull size of the oldest known plant-visiting bat.
© N. Czaplewski

“A longstanding hypothesis holds that species shift to nectar feeding gradually, by first eating a mix of insects and nectar, but this has not been tested with fossils,” said Liliana Dávalos, a professor in the Department of Ecology and Evolution at Stony Brook University and corresponding investigator on the new paper. “Our analyses show that Palynephyllum could not have fed exclusively on nectar, and it likely supplemented its diet with protein-rich insects, which supports this hypothesis.”

Based on their model, which was built by measuring the teeth and skulls of living nectar-feeding bats, the researchers estimated the skull length of the extinct species. They then used the skull length, which relates to key biological traits such as bite force and body size, to infer the diet of the bat.