Carinatae
Encyclopedia
This article is about bird taxonomy; for the topic in pottery and glassware design, see Carinate
.
The Carinatae are, in phylogenetic taxonomy, the last common ancestor of the Neornithes (modern birds
) and Ichthyornis
(an extinct seabird of the Cretaceous
), and all its descendants. Defined in this way, the group includes all modern bird
s, both living and recently extinct, and a few Mesozoic
forms.
(breast bone) has a keel
(carina). The keel is a strong median ridge running down the length of the sternum. This is an important area for the attachment of flight muscles. Thus, all flying birds have a pronounced keel. Ratite
s, all of whom are flightless, lack a strong keel. Thus, living birds were divided into carinates (keeled) and ratites (from ratis, "raft", referring to the flatness of the sternum).
The difficulty with this scheme phylogenetically
was that some flightless birds, without strong carinae, are descended directly from ordinary flying birds with carinae. Examples include the Kakapo
, a flightless parrot
, and the dodo
, a columbiform (the pigeon family). None of these birds are ratites. Thus, this supposedly distinctive feature was easy to use, but had nothing to do with actual phylogenic relationship.
. This sort of definitional problem is one reason why the use of physical characteristics to name taxonomic groups is now discouraged.
The characteristics that actually are unique to the Carinatae have little to do with the sternum. Rather, carinates are unique in having, for example, a globe-shaped, convex head on the humerus
and fully fused bones in the lower leg and outer arm.
They also have a pterygoid bone that articulates with the palatine by means of a joint. The vomer is reduced or absent.
Carinate
This article is about a topic in pottery design. For the article about birds, see Carinatae.Carinate is a shape in pottery, glassware and artistic design usually applied to amphora or vases...
.
The Carinatae are, in phylogenetic taxonomy, the last common ancestor of the Neornithes (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...
) and Ichthyornis
Ichthyornis
Ichthyornis is a genus of toothed seabirds from the Late Cretaceous of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian-Campanian ages,...
(an extinct seabird of the 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...
), and all its descendants. Defined in this way, the group includes all modern 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, both living and recently extinct, and a few 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...
forms.
Earlier definition
Traditionally, Carinatae were defined as all birds whose sternumSternum
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...
(breast bone) has a keel
Keel (bird)
A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight...
(carina). The keel is a strong median ridge running down the length of the sternum. This is an important area for the attachment of flight muscles. Thus, all flying birds have a pronounced keel. Ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s, all of whom are flightless, lack a strong keel. Thus, living birds were divided into carinates (keeled) and ratites (from ratis, "raft", referring to the flatness of the sternum).
The difficulty with this scheme phylogenetically
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
was that some flightless birds, without strong carinae, are descended directly from ordinary flying birds with carinae. Examples include the Kakapo
Kakapo
The Kakapo , Strigops habroptila , also called owl parrot, is a species of large, flightless nocturnal parrot endemic to New Zealand...
, a flightless parrot
Parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...
, and the dodo
Dodo
The dodo was a flightless bird endemic to the Indian Ocean island of Mauritius. Related to pigeons and doves, it stood about a meter tall, weighing about , living on fruit, and nesting on the ground....
, a columbiform (the pigeon family). None of these birds are ratites. Thus, this supposedly distinctive feature was easy to use, but had nothing to do with actual phylogenic relationship.
Current definition
The use of a term for keeled sternum to describe the Ichthyornis–Neornithine group turned out to be equally inapt. Various dinosaurs – apparently, remote ancestors and cousins of the Carinatae – do possess a keeled sternum. So, evidently the presence of this structure does not necessarily imply its use in flightFlight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....
. This sort of definitional problem is one reason why the use of physical characteristics to name taxonomic groups is now discouraged.
The characteristics that actually are unique to the Carinatae have little to do with the sternum. Rather, carinates are unique in having, for example, a globe-shaped, convex head on the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
and fully fused bones in the lower leg and outer arm.
They also have a pterygoid bone that articulates with the palatine by means of a joint. The vomer is reduced or absent.