Étienne Geoffroy Saint-Hilaire became the Chair of Mammals and Birds at the Muséum National d’Histoire Naturelle, the National Museum of Natural History in Paris, when he was only 21 years old. The museum was founded in 1793 by the Convention Nationale, the legislative body during the French Revolution. The Convention combined the Jardin du Roi—renamed the Jardin des Plantes—with a new menagerie that would house live animals for study by scientists.

In 1795, Geoffroy invited Georges Cuvier to Paris, where he became a professor of anatomy at the museum. (Cuvier has a few mammals named after him, too, including this beaked whale.) The two were early contributors to the development of the theory of evolution, and they were intellectually rivals but socially friends. The subject they disagreed on most famously was whether, as Carl Zimmer puts it in Evolution: The Triumph of an Idea, “animals were similar to each other only when they functioned in similar ways.” Cuvier said yes, anatomy was explained by function; Geoffroy said no, all animals are based on the same basic plan. “There is, philosophically speaking, only a single animal,” Geoffroy said, according to Zimmer. Also, Cuvier didn’t believe that species could change over time, while Geoffroy thought they did.

Long story short, we now know that Geoffroy was basically right, but the dispute brought some exciting spectacle to the world of 19th-century biology. For two months in 1830, the two debated the issue in front of an audience every Monday morning at the Académie des Sciences. According to The Cuvier-Geoffroy Debate: French Biology in the Decades Before Darwin by Toby Appel, the debate became so rancorous that they finally had to call it off.

This week, we’ll be looking at some of the mammals named after Geoffroy. According to my new copy of The Eponym Dictionary of Mammals, a book I’ve been wanting for a while, Geoffroy is the namesake of 15 mammal species, as well as several birds (including one called Geoffroyus geoffroyi). For this theme week, I’ll be concentrating on seven of the eight species that honor him with their scientific names, rather than the ones that only have Geoffroy in their common names. (I drew Geoffroy’s black-handed spider monkey back in 2009.)

The first Geoffroy we’ll be meeting this week is this bat, known as the lesser nyctophilus or lesser long-eared bat. It lives only in Australia, and happily, it isn’t endangered or even particularly threatened. It roosts in both natural and man-made structures and particularly likes to use hollow eucalyptus trees for nurseries. Even when disturbed, it is loath to give up a good nesting site; this may account for why it’s able to live so successfully near humans. In the winter, the lesser long-eared bat may be active for only an hour a day, going into torpor—with a lower heart rate and decreased metabolism—to conserve energy the rest of the day.