Yungavolucris
Encyclopedia
Yungavolucris is a monotypic
genus
of enantiornithine
bird
. It contains the single species
Yungavolucris brevipedalis
which lived in the Late Cretaceous
(Maastrichtian
, c.70.6-65.5 mya). The fossil bones were found in the Lecho Formation
at estancia
El Brete, Argentina
.
Little is known about it because the only remains discovered so far are 6 tarsometatarsi
, only one of which is nearly complete. This single foot bone, however, differs from all other birds in being very flat, and also very wide at the lower end. The specimens are small, just over 4 cm long, and if its legs and feet were not excessively shortened in relation to the body, the bird was about the size of a large blackbird in life.
Y. brevipedalis had short, wide, and dorsoplantarly flattened "legs" (actually ankles) with disproportionally broad and splayed "feet" (actually the front part of the feet only) which seem to have pointed markedly outwards (Chiappe 1993). This must have resulted in a somewhat Charlie Chaplin
-like waddle if the bird walked on the ground. It was thus probably better adapted to swimming or even perching in trees than for running around in its richly vegetated shoreline habitat that was dotted by - possibly brackish - lakes and/or small rivers (Chiappe 1993).
Y. brevipedalis was an advanced enantiornithine and is sometimes considered to be closely related to Avisaurus
. This is quite unlikely however; it certainly lacks the backwards-projecting growth of the trochlea
where the middle toe attaches that is typical for Avisauridae
. Moreover, as opposed to the undisputed avisaurids which apparently all were fairly large carnivore
s, it was a much smaller animal and almost certainly did not hunt vertebrates.
Due to the peculiar autapomorphies of the present species' remains, the question of its affinities is hard to decide however. It seems somewhat closer to the avisaurids than Lectavis bretincola, another enantiornithine discovered in the same deposit (Chiappe 1993). On the other hand given that the Spanish
Early Cretaceous (Barremian
, 130-125 mya) enantiornithine Concornis lacustris appears closer to the avisaurids than either Yungavolucris or Lectavis (Sanz et al. 1995), a close relationship between the two El Brete taxa and Avisaurus seems highly unlikely.
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of enantiornithine
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
. It contains the 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...
Yungavolucris brevipedalis
which lived in the Late 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...
(Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
, c.70.6-65.5 mya). The fossil bones were found in the Lecho Formation
Lecho Formation
The Lecho Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation....
at estancia
Estancias
Estancia or Estância is a Spanish and Brazilian Portuguese term describing a large rural estate with similarities to the English term ranch. The term is used in Argentina, Uruguay and southern Chile...
El Brete, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
Little is known about it because the only remains discovered so far are 6 tarsometatarsi
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
, only one of which is nearly complete. This single foot bone, however, differs from all other birds in being very flat, and also very wide at the lower end. The specimens are small, just over 4 cm long, and if its legs and feet were not excessively shortened in relation to the body, the bird was about the size of a large blackbird in life.
Y. brevipedalis had short, wide, and dorsoplantarly flattened "legs" (actually ankles) with disproportionally broad and splayed "feet" (actually the front part of the feet only) which seem to have pointed markedly outwards (Chiappe 1993). This must have resulted in a somewhat Charlie Chaplin
Charlie Chaplin
Sir Charles Spencer "Charlie" Chaplin, KBE was an English comic actor, film director and composer best known for his work during the silent film era. He became the most famous film star in the world before the end of World War I...
-like waddle if the bird walked on the ground. It was thus probably better adapted to swimming or even perching in trees than for running around in its richly vegetated shoreline habitat that was dotted by - possibly brackish - lakes and/or small rivers (Chiappe 1993).
Y. brevipedalis was an advanced enantiornithine and is sometimes considered to be closely related to Avisaurus
Avisaurus
Avisaurus is a genus of enantiornithine bird from the Late Cretaceous of North America.Two species are known; the type species A. archibaldi and A. gloriae...
. This is quite unlikely however; it certainly lacks the backwards-projecting growth of the trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
where the middle toe attaches that is typical for Avisauridae
Avisauridae
The Avisauridae are a family of extinct Enantiornithine birds known from Cretaceous North and South America. They are represented by eight genera.Avisauridae was erected by Brett-Surman and Paul in 1985...
. Moreover, as opposed to the undisputed avisaurids which apparently all were fairly large carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s, it was a much smaller animal and almost certainly did not hunt vertebrates.
Due to the peculiar autapomorphies of the present species' remains, the question of its affinities is hard to decide however. It seems somewhat closer to the avisaurids than Lectavis bretincola, another enantiornithine discovered in the same deposit (Chiappe 1993). On the other hand given that the Spanish
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...
Early Cretaceous (Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...
, 130-125 mya) enantiornithine Concornis lacustris appears closer to the avisaurids than either Yungavolucris or Lectavis (Sanz et al. 1995), a close relationship between the two El Brete taxa and Avisaurus seems highly unlikely.