And they're principally insectivores, meat eaters, but they do play a very important role when it comes to maintaining the plant community in this ecosystem.
Paleontologists aren't sure what they ate, as their forearms were in between those of their carnivorous ancestors and the later specialized insectivores.
This seems like it could be a possibility, because there are modern insectivores, like some species of shrews, that use ultrasound for communication or navigation.
While there is some debate about it, paleontologists think that Alvarezsaurus was an insectivore that used its finger claw to rip into logs in search of termites.
And one reason this trait might've been important for early mammaliaforms and then for the first crown mammals is that many of them were small insectivores who probably hunted at night.
And the reason for that is probably because they were good strategies for survival in the niches that they occupied: being small to medium-sized insectivores living in a world full of large reptiles.
Some 180m years ago, during the early part of the Jurassic period, this site was a lake where mayflies lived and swarmed to mate, as they do today, providing, as a side-effect, a feast for local insectivores.