''Eoalulavis'' (from the Ancient Greek: ''Éōs'', "dawn"; ''alula'', "bastard wing"; ''avis'', "

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

") is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

genus of

enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...

bird that lived during the

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is precede ...

, in the

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

around 125 million years ago. The only known species is ''Eoalulavis hoyasi''. (1996)
An Early Cretaceous bird from Spain and its implications for the evolution of avian flight
''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' 382(6590): 442-445. (HTML abstract) (2002): "The birds from the lower Cretaceous of las hoyas (Province of Cuenca, Spain)", Mesozoic Birds: Above the Heads of the Dinosaurs.University of California Press, Berkeley, , pp. 209-229.

Discovery

Its remains came from the Konservat-Lagerstätte of Las Hoyas, Cuenca,

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

(LH13500), housed in the collection of , consists on both slab and counterslab preserving mainly the thoracic region, part of the neck and both almost complete forelimbs of an adult specimen. It also preserves remains of the

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

, primary, secondary feathers and a bastard wing which have been covered by layers of limonite as a result of the

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

ization process. The preservation is consistent with the taphonomic processes associated with obruption, stagnation and the action of

microbial mat A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts ...

s in the locality (1997): "The mineralization of dinosaur soft tissue in the Lower Cretaceous of Las Hoyas, Spain", Journal of the Geological Society, vol. 154, no. 4, pp. 587-588. that have yielded a wide variety of examples of soft-tissue preservation (e.g., connective tissues in fishes and

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

s or insect wings (2010): "A holistic approach to the palaeoecology of Las Hoyas Konservat-Lagerstätte (La Huérguina Formation, Lower Cretaceous, Iberian Ranges, Spain)", '' Journal of Iberian Geology'', vol. 36, no. 2, pp. 297-326.). Most of the osteological features of the

became apparent only after its acid preparation and transference to a

resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...

cast.

Description

Size

According to its initial description, ''E. hoyasi'' was roughly the size of a

european goldfinch The European goldfinch or simply the goldfinch (''Carduelis carduelis'') is a small passerine bird in the finch family that is native to Europe, North Africa and western and central Asia. It has been introduced to other areas, including Austral ...

(''Carduelis carduelis''), with the bony elements of its wings approximately 17 centimeters (7 inches) in length. Later studies estimated that it had a weight of approximately 45 grams (1.6 ounces) and total wingspan (including feathers) of about 26 centimeters (10 inches), giving it proportions similar to those of a

common kingfisher The common kingfisher (''Alcedo atthis''), also known as the Eurasian kingfisher and river kingfisher, is a small kingfisher with seven subspecies recognized within its wide distribution across Eurasia and North Africa. It is resident in much of ...

(''Alcedo atthis'').

Characteristics

One of the most unusual features of this genus lies in the shape of its bony

sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...

(breastplate). While most early birds had wide sternums, ''Eoalulavis'' had a very thin one, with an expanded front end tapering to a point as well as a rear tip with outward-pointing extensions. This form has been described as "spear-shaped" or "fish-shaped" by some. The morphology of the forelimb in ''Eoalulavis'' is remarkably primitive compared with that of other genera of

birds. (2011): "Pre-modern birds: avian divergences in the Mesozoic", Living dinosaurs: the evolutionary history of modern birds.Edited by GJ Dyke, and G.Kaiser.John Wiley and Sons Ltd., London, UK, , pp. 39-114. The alular and major digits both bear a large

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly ...

and the minor one bears two

. Also the alular digit extends until the distal end of the major

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ar ...

, which is considered a primitive trait within the clade Enantiornithes. At the time of its discovery, it was the earliest bird known to possess an

alula The alula , or bastard wing, (plural ''alulae'') is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ''ala'', meaning "wing". The al ...

, a batch of

feathers Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier ...

on the alular (first) digit that in

modern birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

can be separately moved to improve stability at low flight speeds. Later, more

specimens were discovered with

(2000): "A primitive enantiornithine bird and the origin of feathers", Science, vol. 290, no. 5498, pp. 1955-1959. (2005): "Anatomy of the Early Cretaceous bird Eoenantiornis buhleri (Aves: Enantiornithes) from China", Canadian Journal of Earth Sciences, vol. 42, no. 7, pp. 1331-1338. and this fact has consequently strengthen the

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

that these animals were able to develop a highly complex and active flight. The wide presence of this trait in both Enantiornithes and Ornithuromorpha, the clade which comprises

along with their

counterparts, suggest that the development of the

, and the flight capabilities that it implies, occur early in the avian

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

, presumably in the base of

Ornithothoraces Ornithothoraces is a group of avialans that includes all enantiornithes ("opposite birds") and the euornithes ("true birds"), which includes modern birds and their closest ancestors. The name Ornithothoraces means "bird thoraxes". This refers t ...

Paleobiology and Paleoecology

Flight

The presence of

and a complete set of

aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...

asymmetric feathers arranged forming a modern wing, (2012): "Primitive Wing Feather Arrangement in ''Archaeopteryx lithographica'' and ''Anchiornis huxleyi''", Current Biology, . indicate well develop flight capabilities, as in many other

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

. Its hindlimb morphology remain uncertain as no material of this kind referable to the genus has been found to date. A 2018 study analyzed the proportions of ''Eoalulavis'' and ''

Concornis ''Concornis'' is a genus of enantiornithean birds which lived during the early Cretaceous period, in the late Barremian age about 125 million years ago. Its remains are known from the Calizas de La Huérgina Formation at Las Hoyas, Cuenca prov ...

'' to determine the optimal flight pattern for those genera. The study found that they likely engaged in bounding flight, a form of flight popular among modern small and short-winged birds. A bird engaging in bounding flight alternates between upward-thrusting flaps and short dives with folded wings. The study also found that they were capable of continuous flapping flight, but were likely unable to glide due to having a high body mass to wingspan ratio. The study concluded that ''Eolalulavis'', ''Concornis'', and likely many other enantiornitheans alternated between the fast bounding flight and the slower but more efficient flapping flight depending on the circumstances, similar to modern

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

s and

woodpecker Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...

Diet

The

preserves concentrated remains of

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

cuticles A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

in the area of the abdomen, interpreted as its last meal. It provided the first direct evidence of feeding behaviour in Enantiornithes and in

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

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. This fact has been interpreted as evidence of an

ecological Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

role in ''Eoalulavis'' similar to that of extant

wader 245px, A flock of Dunlins and Red knots">Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflat ...

s; living mainly in the shore seeking for little

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...

in a similar way of modern

turnstone Turnstones are two bird species that comprise the genus ''Arenaria'' in the family Scolopacidae. They are closely related to calidrid sandpipers and might be considered members of the tribe Calidriini. The genus ''Arenaria'' was introduced by ...

Environment

The locality of Las Hoyas was in the

seasonal A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and po ...

subtropical

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...

ecologically dominated by fully aquatic organisms (e.g.:

holostean Holostei is a group of ray-finned bony fish. It is divided into two major clades, the Halecomorphi, represented by a single living species, the bowfin ('' Amia calva''), as well as the Ginglymodi, the sole living representatives being the gars ...

fishes). The avifauna of the locality includes so far two more enantiornithean

: the sparrow-sized '' Iberomesornis romerali'' (1988):
Unusual early cretaceous birds from Spain
, Nature, vol. 331, no. 6155, pp. 433-435. and the

starling Starlings are small to medium-sized passerine birds in the family Sturnidae. The Sturnidae are named for the genus '' Sturnus'', which in turn comes from the Latin word for starling, ''sturnus''. Many Asian species, particularly the larger ones, ...

-sized '' Concornis lacustris.'' ''Eoalulavis hoyasi'' is believed to be the most linked to a semi-aquatic environment of the three. (1992):
A new bird from the Early Cretaceous of Las Hoyas, Spain, and the early radiation of bird
s", Palaeontology, vol. 35, no. 4, pp. 829-845.

Classification

The

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

relationships within Enantiornithes are largely unsolved so far whilst several

analyses have been performed in the last decades. (2013): "A new enantiornithine from the Yixian Formation with the first recognized avian enamel specialization", Journal of Vertebrate Paleontology, vol. 33, no. 1, pp. 1-12.(2007): Glorified dinosaurs: the origin and early evolution of birds, John Wiley. However, some groups of Enantiornithes seem to have fairly strong statistical support. In the last cladistic analysis ''Eoalulavis'' groups with the Chinese genus '' Liaoningornis'' forming a monophyletic group of derived Enantiornithes. Nevertheless, this concrete grouping has not a high statistical support and the enantiornithean status of ''Liaoningornis'' remains currently controversial. (2002): "A new and primitive enantiornithine bird from the Early Cretaceous of China", Journal of Vertebrate Paleontology, vol. 22, no. 1, pp. 49-57. (2012): "A revised look at ''Liaoningornis longidigitrus'' (Aves)", Vertebrata PalAsiatica, vol. 5, no. 1, pp. 25-37. ''Eoalulavis hoyasi'' presents numerous synapomorphies that justifies the inclusion of the

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

within Enantiornithes and the less inclusive clade

Euenantiornithes The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...

. (2002): "Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes)", Mesozoic birds: above the heads of dinosaurs, , pp. 240-267. These traits include a groove in the inter-osseous surface of

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

or a conspicuous

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

in the dorsal surface of the strut-like coracoids.

References

{{Taxonbar, from=Q5381581 Enantiornitheans Euenantiornitheans Bird genera Cretaceous birds of Europe Cretaceous Spain Fossils of Spain Fossil taxa described in 1996 La Huérguina Formation