Eoalulavis was an enantiornithine bird. It lived during the Aptian

Aptian

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 in the Early Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

, about 115 mya and is known from fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s found at Las Hoyas

Las Hoyas

Las Hoyas is a Cretaceous Konservat-Lagerstätten located near the city of Cuenca, Spain.It is dated as Barremian , and is mostly known from its exquisitely preserved dinosaurs, especially enantiornithines.- Taphonomy :...

, Spain

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

. Only a single species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 is known, Eoalulavis hoyasi.

At the time of its discovery, it was the oldest known bird to possess an alula

Alula

The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species...

, a batch of feathers on the thumb that can be separately moved to improve stability at low flight speeds. This feature evolve

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

d either independently in Enantiornithes and the ancestors of modern birds, or it is very ancient and dates back to soon after Archaeopteryx

Archaeopteryx

Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...

. The former is considered more likely, as an alula is not known from the most primitive Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 birds. The same seems to go for uncinate process

Uncinate processes of ribs

The uncinate processes of the ribs are extensions of bone that in birds project caudally from the vertical segment of each rib. These processes help to strengthen the rib cage of birds by overlapping with the rib behind them...

es, which are absent in this species but present in a few other contemporary birds, some of them (like Longipteryx chaoyangensis) also Enantiornithes.