Search results
Results From The WOW.Com Content Network
The earliest recorded acanthodian, Fanjingshania renovata, [19] comes from the lower Silurian of China and it is also the oldest jawed vertebrate with known anatomical features. [19] Coeval to Fanjingshania is the tooth-based acanthodian species Qianodus duplicis [20] that represents the oldest unequivocal toothed vertebrate. Osteichthyes
The archicortex is most prevalent in the olfactory cortex and the hippocampus, [4] which are responsible for processing smells and forming memories, respectively. [5] Because olfaction is considered to be the phylogenetically oldest sensory modality, [6] and the limbic system, of which the hippocampus is a part, is one of the oldest systems in the brain, [7] it is likely that the archicortex ...
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
The mouth is located just behind the head, after a rostrum, on the underside of the body. It has a pair of cuticular jaws, supplied by strong muscles, and often bearing minute teeth. A "basal plate" on the lower surface that bears a comb-like structure is also present.
This arch divides into a maxillary process and a mandibular process, giving rise to structures including the bones of the lower two-thirds of the face and the jaw. The maxillary process becomes the maxilla (or upper jaw, although there are large differences among animals [11]), and palate while the mandibular process becomes the mandible or lower jaw.
One of these, the fossil jaw fragment of Dharragarra, is the oldest known platypus-like fossil. [ 50 ] [ 3 ] [ 65 ] The durophagous Kollikodon , the pseudotribosphenic Steropodon , and Stirtodon , Dharragarra , Opalios , and Parvopalus occur in the same Cenomanian deposits.
The pulp is a soft tissue area containing the nerve and blood vessels to nourish and protect the tooth, located within the pulp cavity. A tooth sits in a specialized socket called the alveolus. The tooth is held in location by a periodontal ligament, with the assistance of cementum. Teeth are surrounded by gingiva, or gums, part of the ...
The evolution of the mammalian middle ear appears to have occurred in two steps. A partial middle ear formed by the departure of postdentary bones from the dentary, and happened independently in the ancestors of monotremes and therians. The second step was the transition to a definite mammalian middle ear, and evolved independently at least ...