Longicrusavis
Encyclopedia
Longicrusavis is an extinct genus
of basal
ornithuromorph
bird
within the family
Hongshanornithidae
. Remains have been found from the Lower Cretaceous Yixian Formation
in Liaoning Province, China
.
specimen PKUP V1069, which consists of shale
slab and counter slab
. The skeleton is nearly complete and belongs to an adult individual, with carbonized
feathers preserved around the head and forelimbs.
Like the closely related genus Hongshanornis
, Longicrusavis has hindlimbs that are very long relative to the forelimbs. Longicrusavis has a rostrum
that is more robust than that of Hongshanornis. The skull is roughly triangular in shape and the orbits
, or eye sockets, are large. In lateral view, the dorsal margin of the skull is slightly concave, but not as much as the dorsal margin of the skull of Hongshanornis, where there is an abrupt constriction at the rostrum.
Although no teeth are preserved, they were likely present because there appears to be alveoli, or tooth sockets, in the premaxilla
and maxilla
. Hongshanornis
also appears to have alveoli, despite being described as toothless when it was first named. No alveoli are found in the mandible, indicating that it was likely edentulous
. Longicrusavis most likely lacked a beak
because it does not possess groves and foramina that are indicative beaks in other taxa such as Archaeorhynchus
.
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 basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ornithuromorph
Ornithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
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...
within the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Hongshanornithidae
Hongshanornithidae
Hongshanornithidae is an extinct family of basal ornithuromorph birds from the Early Cretaceous of China. The family includes the genera Hongshanornis and Longicrusavis, from the Yixian Formation, in Inner Mongolia and Liaoning Province, respectively, and possibly Parahongshanornis from the...
. Remains have been found from the Lower Cretaceous Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
in Liaoning Province, 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...
.
Description
Longicrusavis is known from the holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen PKUP V1069, which consists of shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
slab and counter slab
Counter slab
Counter slab and slab are the matching halves of a fossil-bearing matrix formed in sedimentary deposits. When excavated the matrix may be split along the natural grain or cleavage of the rock. A fossil embedded in the sediment may then also split down the middle, with fossil remains sticking to...
. The skeleton is nearly complete and belongs to an adult individual, with carbonized
Carbonization
Carbonization or carbonisation is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation. It is often used in organic chemistry with reference to the generation of coal gas and coal tar from raw coal...
feathers preserved around the head and forelimbs.
Like the closely related genus Hongshanornis
Hongshanornis
Hongshanornis is a genus of ornithurine bird known from the early Cretaceous lake deposits of the Yixian Formation, Inner Mongolia, China. The only known specimen was recovered in 2005. It was likely a strong flier and due to its long legs, Hongshanornis appears to have been a wader, feeding in...
, Longicrusavis has hindlimbs that are very long relative to the forelimbs. Longicrusavis has a rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
that is more robust than that of Hongshanornis. The skull is roughly triangular in shape and the orbits
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
, or eye sockets, are large. In lateral view, the dorsal margin of the skull is slightly concave, but not as much as the dorsal margin of the skull of Hongshanornis, where there is an abrupt constriction at the rostrum.
Although no teeth are preserved, they were likely present because there appears to be alveoli, or tooth sockets, in the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
and maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
. Hongshanornis
Hongshanornis
Hongshanornis is a genus of ornithurine bird known from the early Cretaceous lake deposits of the Yixian Formation, Inner Mongolia, China. The only known specimen was recovered in 2005. It was likely a strong flier and due to its long legs, Hongshanornis appears to have been a wader, feeding in...
also appears to have alveoli, despite being described as toothless when it was first named. No alveoli are found in the mandible, indicating that it was likely edentulous
Edentulism
Edentulism is the condition of being toothless to at least some degree; it is the result of tooth loss. Loss of some teeth results in partial edentulism, while loss of all teeth results in complete edentulism....
. Longicrusavis most likely lacked a beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
because it does not possess groves and foramina that are indicative beaks in other taxa such as Archaeorhynchus
Archaeorhynchus
Archaeorhynchus is a prehistoric bird genus from the Early Cretaceous. The single known species, Archaeorhynchus spathula lived about 122 million years ago, in the Aptian...
.