Eoalulavis

Eoalulavis (from the Ancient Greek: Éōs, "dawn"; alula, "bastard wing"; avis, "bird") is a monotypic genus of enantiornithine bird that lived during the Barremian, in the Lower Cretaceous around 125 million years ago. The only known species is Eoalulavis hoyasi.

Discovery
Its remains came from the Konservat-Lagerstätte of Las Hoyas, Cuenca, Spain. The holotype (LH13500), housed in the collection of Museo de las Ciencias de Castilla-La Mancha (es), consists on both slab and counterslab preserving mainly the thoracic region, part of the neck and both almost complete forelimbs of an adult specimen.[1] It also preserves remains of the body, primary, secondary feathers and a bastard wing which have been covered by layers of limonite as a result of the fossilization process.[1] The preservation is consistent with the taphonomic processes associated with obruption, stagnation and the action of microbial mats in the locality[3] that have yielded a wide variety of examples of soft-tissue preservation (e.g.: connective tissues in fishes and theropods[3] or insect wings[4]). Most of the osteological features of the holotype became apparent only after its acid preparation and transference to a resin cast.

Paleobiology and paleoecology
E. hoyasi was roughly the size of a little fringilid with a wingspan of nearly 20 cm.[1] The presence of alula and a complete set of aerodynamic asymmetric feathers arranged forming a modern wing,[5] indicate well develop flight capabilities, as in many other enantiornithine taxa.[6] Its hindlimb morphology remain uncertain as no material of this kind referable to the genus has been found to date.

The holotype preserves concentrated remains of crustacean cuticles in the area of the abdomen, interpreted as its last meal.[2] It provided the first direct evidence of feeding behaviour in Enantiornithes and in Mesozoic birds in general, though, since then, more examples of undigested food associated with enantiornithine specimens have been discovered reporting a wide variety of feeding habits.[6] This fact has been interpreted as evidence of an ecological role in Eoalulavis similar to that of extant waders; living mainly in the shore seeking for little invertebrates in a similar way of modern turnstones.[4]

The locality of Las Hoyas was in the Barremian a seasonal subtropical wetland ecologically dominated by fully aquatic organisms (e.g.: holostean fishes).[4] The avifauna of the locality includes so far two more enantiornithine taxa: the sparrow-sized Iberomesornis romerali[7] and the pigeon-sized Concornis lacustris.[7] Eoalulavis hoyasi is believed to be the most linked to a semi-aquatic environment of the three.