Remarkable New Genus of Tetraodontiform Fish with Features of Both Balistids and Ostraciids from the Eocene of Turkmenistan

Abstract

A new genus and species of tetraodontiform fish, <i>Eospinus daniltshenkoi</i>, is described from the Lower Eocene of Turkmenistan (Danatinsk Formation). It is referred to the Balistoidea because it has three large dorsal-fin spines; the pelvic fin reduced to a rudimentary but prominent structure apparently composed of two partially fused spines at the posterior end of the pelvis; and enlarged scale plates that form an incomplete carapace or loosely articulated armature around much of the body. It differs from all other balistoids in having a long median spine projecting forward from the snout and another spine projecting posteriorly from the middle of each side of the body; lower jaw teeth twice as long as the upper jaw teeth; and in lacking encasing scales around the rudimentary pelvic spine. <i>Eospinus</i> is the first record of a balistoid fish from the Eocene with three dorsal-fin spines and the pelvic spines fused together at the end of the pelvis, as otherwise only occurs in balistids, which are first recorded from the Oligocene.