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Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. Most gnathostomes have retained ancestral traits like true teeth , a stomach , [ 2 ] and paired appendages (pectoral and pelvic fins, arms, legs, wings, etc.). [ 3 ]
The earliest deposited generations of accessory teeth in each row are located at the tip of the whorl spiral labially of the primary teeth. Unlike the continuously shedding teeth of modern sharks, [7] the tooth whorls of Qianodus retained their teeth and grew in size throughout the life of the animal. The recorded gradual enlargement of the ...
The bursovaginoids have paired sensory organs and are characterized by the presence of a penis and a sperm-storage organ called a bursa. [4] Gnathostomulids have no known fossil record, though there are (debatable) similarities between the jaws of modern gnathostomulids and certain conodont elements. (Ochietti & Cailleux, 1969; Durden et al ...
The three forms of teeth, i.e., coniform cones, ramiform bars, and pectiniform platforms, probably performed different functions. For many years, conodonts were known only from enigmatic tooth-like microfossils (200 micrometers to 5 millimeters in length [ 17 ] ), which occur commonly, but not always, in isolation and were not associated with ...
Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes).They are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and chimaeras.
Urbilaterian: the last common ancestor of xenacoelomorphs, protostomes (including the arthropod [insect, crustacean, spider], mollusc [squid, snail, clam] and annelid [earthworm] lineages) and the deuterostomes (including the vertebrate [human] lineage) (the last two are more related to each other and called Nephrozoa).
Supernumerary teeth were typically located distal to the cleft. [76] In a study of Jordanian subjects, the prevalence of dental anomaly was higher in CLP patients than in normal subjects. Missing teeth were observed in 66.7% of patients, with maxillary lateral incisor as the most frequently affected tooth.
A pulpal A-delta (noxious, short sharp pain) nerve fibre is either wrapped around the base of this process, or travels a short way into the dentinal tubule with the odontoblast process (max ~0.1 mm) This process lies in the dentinal tubule. In primates enamel spindles were observed where the odontoblast process reaches until the border between ...