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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
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.
Cladoselache was one of the earliest vertebrates known to have had shark-like tooth replacement, with a series of widely spaced tooth rows constantly unfurling new teeth outward. There were around seven to nine closely packed teeth per tooth row, [ 10 ] [ 14 ] and about eleven or twelve rows arranged from front to back on each palatoquadrate.
The diagram is based on Michael Benton, 2005. [17] Dunkleosteus , among the first of the vertebrate apex predators , was a giant armoured placoderm predator . Amazichthys , a pelagic arthrodire from the Middle Famennian of the Late Devonian .
As in all true mammals, the tiny bones that conduct sound to the inner ear are fully incorporated into the skull, rather than lying in the jaw as in non-mammalian cynodonts and other pre-mammalian synapsids; this feature, too, is now claimed to have evolved independently in monotremes and therians, [9] although, as with the analogous evolution ...
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
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 three times in the ancestors of today's monotremes, marsupials and placentals. [38]
The adductor fossa or Meckelian orifice in reptiles and dinosaurs is the major opening into the lower jaw, located between the tooth-bearing region and the jaw articulation. It opens dorsally, and is laterally walled by the surangular and medially by the prearticular ; as the latter is usually much lower than the former, the fossa is visible in ...