A predentary is found in all but perhaps the earliest ornithischian dinosaurs. Its occurrence ledOthniel Marsh to propose naming the group Predentata,[4] though this is now considered a synonym of Ornithischia.[5] The predentary coincided with thepremaxilla in theupper jaw. Together, they formed abeak-like apparatus used to clip off plant material. Inceratopsian dinosaurs, it opposes therostral bone. The predentary would have allowed the dentaries to move slightly independently of each other, aiding chewing.[6] The toothless, beaked tip of the dentary insilesaurids may have been a predecessor of the ornithischian predentary.[7][5]
The avian predentary arose in the clade Ornithuromorpha,[3] and is absent from earlier bird lineages such asenantiornitheans andArchaeopteryx.[8] It has been interpreted as asesamoid bone.[3] Members ofNeornithes, the group containing all modern birds, lack a predentary, unlike other ornithuromorphs, possibly because the fusion of the mandibular symphysis and loss of teeth rendered the predentary unnecessary.[9] Due to the independent origins of the predentary in ornithischians and birds, the avian predentary has alternatively been called theintersymphyseal ossificiation,[10] although this term is not entirely appropriate because it is not strictly intersymphyseal in position.[3]
An ossified predentary has arisen in two lineages of fish, the extinct Saurodontidae and the extant Istiophoridae (marlin), and a cartilaginous pre-mandibular element occurs in several other groups.[11] The istiophorid predentary differs from other predentaries in bearing denticles.[11]
^Fierstine, Harry L.; Applegate, Shelton P. (1968). "Billfish remains from southern California with remarks on the importance of the predentary bone".Bulletin of the Southern California Academy of Sciences.67 (1):29–39.
^abNorman, David B; Baron, Matthew G; Garcia, Mauricio S; Müller, Rodrigo Temp (2022-09-01). "Taxonomic, palaeobiological and evolutionary implications of a phylogenetic hypothesis for Ornithischia (Archosauria: Dinosauria)".Zoological Journal of the Linnean Society.196 (4): –062.doi:10.1093/zoolinnean/zlac062.ISSN0024-4082.
^Nabavizadeh, Ali; Weishampel, David B. (2016-08-04). "The predentary bone and its significance in the evolution of feeding mechanisms in ornithischian dinosaurs".The Anatomical Record.299 (10):1358–1388.doi:10.1002/ar.23455.ISSN1932-8486.PMID27490958.
^O'Connor, Jingmai K.; Wang, Xuri; Chiappe, Luis M.; Gao, Chunling; Meng, Qingjin; Cheng, Xiaodong; Liu, Jinyuan (2009). "Phylogenetic support for a specialized clade of Cretaceous enantiornithine birds with information from a new species".Journal of Vertebrate Paleontology.29 (1):188–204.Bibcode:2009JVPal..29..188O.doi:10.1080/02724634.2009.10010371.JSTOR20491078.
^abBardack, David; Sprinkle, Gloria (1969-08-28). "Morphology and relationships of saurocephalid fishes".Fieldiana Geology.16 (12).
