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A New Primitive Acanthomorph Fish from the Greenhorn Formation (Late Cretaceous) of Nebraska

Gloria Arratia and John Chorn
Journal of Vertebrate Paleontology
Vol. 18, No. 2 (Jun. 15, 1998), pp. 301-314
Stable URL: http://www.jstor.org/stable/4523900
Page Count: 14
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A New Primitive Acanthomorph Fish from the Greenhorn Formation (Late Cretaceous) of Nebraska
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Abstract

A new acanthomorph genus is described from the Greenhorn Formation (Turonian) of north eastern Nebraska. The type and only specimen of this genus is a nearly complete skull and postcranial skeleton characterized by an interesting combination of features such as a prominent, anteriorly thickened supraoccipital crest, protrusile upper jaw with well developed premaxilla, opercular bones without spines, 39 vertebral centra, pectorals very low on the flank, pelvic fins in abdominal position, medial pelvic process distally ossified, true dorsal fin-spines present, and spinoid scales covering the trunk. The Late Cretaceous acanthomorph †Aipichthys shares a few characters with the new genus including deeply cleft caudal fin and nine principal caudal rays on the upper lobe of the caudal fin. Characters are shared also with †Araripichthys from the Early Cretaceous of Brazil. The material described resembles in certain characters (e.g., supraneurals, abdominal vertebrae and probably paired fin placement) the acanthomorph †Ferrifrons rugosus, represented by a single incomplete specimen from the Niobrara Chalk (Santonian). Based on a few synapomorphies, the new genus and †Ferrifrons are included in the new fossil family Ferrifronsidae.

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