Jaws and teeth of american cichlids (Pisces: Labroidei)

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Abstract
The morphology of the upper, lower, and pharyngeal jaws is very similar among American cichlids. Common conditions are: (1) the presence of a premaxillary dentigerous arm shorter than the ascending arm (exceptions are Astronotus, Cichla, and Crenicichla semifasciata), (2) a narrow coulter area; in contrast, a broad coulter area is found in the Crenicichline Group, in certain chaetobranchines, and in Apistogramma, (3) the mandibular sensory canal exists to the skin through five or six simple pores; in contrast, it exits through numerous small pores that increase in number during ontogeny in the Chaetobranchine Group, certain crenicichlines, such as Cichla, Crenicichla lepidota, Crenicichla proteus, and Crenicichla vittata, and certain genera of the Cichlasomine Group A, such as Caquetaia, Petenia, Neetroplus, and “Cichlasoma,” and (4) the premaxilla and dentary of American cichlids commonly bear unicuspid, conical teeth with a few exceptions such as Neetroplus (with scraping blade teeth) and “Cichlasoma” facetum, “C.” cyanoguttatum, “C.” guttulatum, and “C.” spilurum (with bicuspid [hooked] teeth). In contrast to the near uniformity of the upper and lower jaws, the upper and lower pharyngeal jaws present a great diversity of tooth shapes. At least seven types are found in American cichlids; usually, several types exist on a single tooth plate, but the combination of tooth types differs among some genera.The pharyngobranchial 4 tooth plate has significant evolutionary transformations in labroids. The caudal margin of the pharyngobranchial 4 tooth plate bears the frayed zone in cichlids and embiotocids. The presence of a broad frayed zone bearing one to seven concavities represents a synapomorphy for the family Cichlidae, whereas a deep, narrow frayed zone is a synapomorphy of Embiotocidae. The absence of the frayed zone is a synapomorphy of Pomacentridae, whereas the loss of the pharyngobranchial 4 is a synapomorphy of Labridae.