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In some rodents, the alisphenoid strut is an extension of the alisphenoid bone that separates two foramina in the skull, the masticatory–buccinator foramen and the foramen ovale accessorium. The presence or absence of this strut is variable between species, but also within them; some Oryzomyini even have a strut on one side of the skull but ...
Yinotheria is a proposed basal subclass clade of crown mammals uniting the Shuotheriidae, an extinct group of mammals from the Jurassic of Eurasia, with Australosphenida, a group of mammals known from the Jurassic to Cretaceous of Gondwana, which possibly include living monotremes. [3]
In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, regardless of current functional differences. Evolutionary biology explains homologous structures as retained heredity from a common ancestor after having been subjected to adaptive modifications for different ...
The greater wings of the sphenoid are two strong processes of bone, which arise from the sides of the body, and are curved upward, laterally, and backward; the posterior part of each projects as a triangular process that fits into the angle between the squamous and the petrous part of the temporal bone and presents at its apex a downward-directed process, the spine of sphenoid bone.
Homology can be confidently compared even between phylogenetically distant species or highly rearranged species (e.g., gibbons). Using cladistic analysis rearrangements that have diversified the mammalian karyotype are more precisely mapped and placed in a phylogenomic perspective.
The epipterygoid is considered to be homologous to the alisphenoid bone of mammals. [2] Though present in many extinct archosaurs , it has been independently lost in modern crocodilians and birds. [ 3 ] [ 4 ]
Mammalian features that both groups inherited from a common ancestor include the loss of teeth on the palate, the expansion of the epipterygoid bone at the base of the skull (an area called the alisphenoid in mammals), and the narrowing of the skull roof to a narrow sagittal crest running between large temporal openings. [4]
Abdomen Abducens nerve Abomasum Acarinarium Accessory bone Acetabulum (morphology) Acicula Acidopore Acrodont Acromion Acrosome Adipose eyelid Adrenal gland Aedeagus Air sacs Alae (nematode anatomy) Albinism in biology Alisphenoid strut Alula Alveolar gland Ambulacral Amnion Amniotic sac Amphid Ampullae of Lorenzini Ampullary cupula Amygdala Anal gland Anal scale Anatomical terms of bone ...