Position of Developing Replacement Teeth in Teleosts
Most osteichthyans continuously replace their teeth throughout their lifetimes. Replacement teeth may develop in the soft tissue outside the bone to which they will attach (“extraosseous”) or in sockets within the bone (“intraosseous”) beneath their functional predecessor. This paper presents a systematic documentation of the position of developing replacement teeth in teleost fishes, based upon a literature review and examination of modern skeletal material. Plotting the distribution of this character on a cladogram of teleost phylogeny indicates that extraosseous development of replacement teeth is plesiomorphic. Intraosseous development, the derived state, has evolved in at least three clades: in branchial and palatal dentitions of the elopiform Albula; in oral dentitions of several characiforms; and in oral and/or pharyngeal dentitions of various acanthopterygians, especially many perciforms. Two interrelated changes are necessary for the evolution of this derived state: replacement teeth must move beneath their functional predecessors; and replacement teeth must be encased in bone. Intraosseous development of replacement teeth may affect the relation of the dermal and endochondral skeletons.Abstract
Cladogram of teleost phylogeny showing character distribution of location of developing replacement teeth. Intraosseous development of replacement teeth has evolved at least three times: in the elopiform Albula vulpes; in several characiforms; and in many acanthoperygians. Phylogeny follows the Tree of Life Web site (http://phylogeny.arizona.edu/tree/life.html)
Amia calva (UMMZ 182068): lingual view of left maxilla showing tooth caps in various stages of development, as well as attached functional teeth. This specimen was incompletely skeletonized, so that tooth caps may be seen adhering to soft tissue (striped area)
Osteoglossum bicirrhosum (UMMZ 213909): lingual view of right dentary showing tooth caps in various stages of development, functional teeth, and resorption features
Enchelycore nigricans (UMMZ 186982): lingual view of right dentary showing replacement teeth resting on top of bony ridge, forming at an angle of about 90° to functional teeth, and rotating into functional position
Hepsetus odoe (UMMZ 00152): dorsal view of dentary showing two tooth rows separated by a trench containing developing replacement teeth. Replacement teeth develop at about 90° to functional teeth, with most tips pointing toward the back of the jaw
Leporinus obtusidens (UMMZ 207871): dorsal view of dentary showing functional teeth with pleurodont attachment (to the lingual aspect of the jaw). There is a single replacement compartment on each side enclosed by bone labially and lingually but open above and beneath. Replacement teeth develop in about the same orientation as functional teeth
Fundulus similis (UMMZ 153579): dorsal view of lower pharyngeal showing several empty tooth sockets, and sockets with unerupted teeth still inside
Microspathodon chrysurus (UMMZ 187085): labial view of left dentary showing replacement trench on the labial side of the anterior aspect of the jaw. The trench is open dorsally, but otherwise enclosed in bone, and contains multiple replacement teeth. Further back along the tooth row, behind the trench, are several teeth erupting from inside the bone
Eopsetta jordani (UMMZ 176332): lingual view of right dentary showing replacement tooth caps beneath fully developed teeth, resting against lingual aspect of jaw. After the functional tooth is shed, the cap moves into the resorption pit and continues development
Hippoglossus hippoglossus (UMMZ 187304): labial view of right premaxilla showing teeth at various stages developing inside socketlike resorption areas. The tooth cap furthest to the left is located beneath and labial to its functional predecessor, near a small resorption area