Ornithothoraces
Encyclopedia
Ornithothoraces is a clade
of bird
s which includes all enantiornithines
and modern birds
(Neornithes).
The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds. This anatomy includes elongated coracoids, a large, keeled sternum
, and modified glenoid joint of the shoulder, along with a semirigid dorsal
rib cage. The earliest known member of the group is Protopteryx fengningensis, from the Sichakou Member of the Huajiying Formation
of China
, which dates to around 140 Ma ago.
, which together with the Palaeognathae and Neognathae
comprised the Neornithes. In 1994, Chiappe and Calvo forwarded a phylogenetic
definition of Ornithothoraces as the common ancestor of Iberomesornis romerali
and extant birds, plus all their descendants. This was followed by Chiappe in 1996. This definition gives a node-based clade
.
Sereno (1998) defined Ornithothoraces in the same node-based way, but used Sinornis santensis instead of Iberomesornis
.
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of 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...
s which includes all enantiornithines
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...
and modern birds
Modern birds
Modern birds are the most recent common ancestor of all living birds and all its descendants.Modern birds are characterised by feathers, a beak with no teeth , the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton...
(Neornithes).
The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds. This anatomy includes elongated coracoids, a large, keeled sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
, and modified glenoid joint of the shoulder, along with a semirigid dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
rib cage. The earliest known member of the group is Protopteryx fengningensis, from the Sichakou Member of the Huajiying Formation
Huajiying Formation
The Huajiying Formation is a geological formation in Hebei, People's Republic of China. Known for its fossils including primitive birds, the age of the ormation is uncertain. It may represent an early portion of the Jehol Biota, dating to somewhere in the early Cretaceous or late Jurassic periods...
of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, which dates to around 140 Ma ago.
Definition
Under older classifications, the primitive toothed members of the group was united in the superorder OdontognathaeOdontognathae
Odontognathae is an extinct superorder of birds found widely in Kansas. The superorder was originally proposed by Alexander Wetmore, who attempted to link fossil birds with the presence of teeth, specifically of the orders Hesperornithiformes and Ichthyornithiformes...
, which together with the Palaeognathae and Neognathae
Neognathae
Neognaths are birds within the subclass Neornithes of the class Aves. The Neognathae include virtually all living birds; their sister taxon Palaeognathae contains the tinamous and the flightless ratites....
comprised the Neornithes. In 1994, Chiappe and Calvo forwarded a phylogenetic
Phylogenetic nomenclature
Phylogenetic nomenclature or phylogenetic taxonomy is an alternative to rank-based nomenclature, applying definitions from cladistics . Its two defining features are the use of phylogenetic definitions of biological taxon names, and the lack of obligatory ranks...
definition of Ornithothoraces as the common ancestor of Iberomesornis romerali
Iberomesornis
Iberomesornis is a monotypic genus of enantiornithine bird of the Cretaceous of Spain.In 1985 the fossil of Iberomesornis was discovered by Armando Díaz Romeral in the Early Cretaceous Calizas de La Huérguina Formation at Las Hoyas, Cuenca Province, east central Spain, which dates to the late...
and extant birds, plus all their descendants. This was followed by Chiappe in 1996. This definition gives a node-based clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
.
Sereno (1998) defined Ornithothoraces in the same node-based way, but used Sinornis santensis instead of Iberomesornis
Iberomesornis
Iberomesornis is a monotypic genus of enantiornithine bird of the Cretaceous of Spain.In 1985 the fossil of Iberomesornis was discovered by Armando Díaz Romeral in the Early Cretaceous Calizas de La Huérguina Formation at Las Hoyas, Cuenca Province, east central Spain, which dates to the late...
.