Fossils identified as zeiform fishes are confined to marine habitats and are relatively young, ranging in age from Oligocene to Holocene deposits. They have been found in Europe, the West Indies, South Africa, and Indonesia. The phy-logenetic relationships of the Zeiformes were explicated by Johnson and Patterson in their 1993 publication on the phy-logenetic relationships of the percomorph fishes. They recognized Zeiformes as a monophyletic taxon characterized by the following shared derived characters. There is a distinctive configuration of upright columnar processes on the dorsal elements of the gill arch skeleton. Baudelot's ligament originates immediately under the vagus foramen of the exoccipitals. The distal part of the proximal middle radials of the dorsal fin ptery-giophores is expanded laterally. The palatines have a specialized, mobile articulation with the ectopterygoid, which is truncated dorsally. The metapterygoid is extremely reduced, and a continuous median cartilage extends below the frontals and between the ethmoid cartilage and pterosphenoids.
Based on what they term "admittedly tenuous evidence," Johnson and Patterson considered the Zeiformes to be the sister taxon of a group making up the order Beryciformes and a huge conglomeration of spiny-rayed fishes known as the "percomorpha," including the Perciformes, Pleuronecti-formes (flounders, soles, etc.), Tetraodontiformes (trigger-fishes and pufferfishes, among others), Scorpaeniformes (scorpionfishes, gurnards, flatheads, and so on), Dactylopter-iformes (helmet gurnards), Synbranchiformes (swamp eels, spiny eels, and others), Elassomatidae (pygmy sunfish), Gas-terosteriformes (pipefish, trumpetfish, etc.), Mugiloidei (mullets), and Atherinomorpha (Atheriniformes, Beloniformes, and Cyprinodontiformes).
The order Zeiformes comprises six families: Zeidae, Parazenidae, Zeniontidae, Oreosomatidae, Grammicolepidae, and Caproidae. In their 1966 seminal paper on the phyloge-netic relationships of teleost fishes, P. H. Greenwood and collaborators included the boarfishes (family Caproidae) in the Zeiformes, but they presented no evidence to support this assignment. Heemstra excluded the Caproidae from the Zeiformes in his 1980 taxonomic revision of the zeid fishes of South Africa, and in the book Smiths' Sea Fishes, Heemstra included the Caproidae in the order Perciformes. For the purposes of this publication, the Caproidae are included in the Zeiformes.
Much work remains to be done on the systematics of the Zeiformes, and the classification adopted here is tentative. The composition, definitions, and distinction of the families Zeidae, Zeniontidae, and Parazenidae are unsettled. The genus Cyttomimus (Gilbert, 1905) appears to be related closely to Capromimus (Gill, 1893). Although these two genera seem to be placed correctly in the Zeiformes, their affinity with any of the families recognized here is unclear. The genus Macruro-cyttus (Fowler, 1933) may belong in the Zeniontidae, but the head of Macrurocyttus acanthopodus (Fowler, 1933) looks very different from those of the two species of Zenion that are known.
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