Aspistor verumquadriscutis, a new fossil species of sea catfishes (Siluriformes; Ariidae) from the upper Miocene of Venezuela

Abstract

The Late Miocene Urumaco Formation, Northwestern Venezuela, one of the most fossiliferous units in the Neogene of tropical America, represents a shallow, marginal marine to deltaic wetland and fluvial system. A new extinct species of sea catfishes is described from the Urumaco Formation. Aspistor verumquadriscutis n. sp. is placed in the genera Aspistor based on five synapomorphies shared with modern congeners: epioccipital dorsally exposed, parieto-supraoccipital posterior margin convex, nuchal plates forming a large butterfly-shaped or moon-shaped structure, anterior margin of nuchal plate slightly concave, and nuchal plate overlapping parieto-supraoccipital. The new fossil species is distinguished from its modern congeners by having a shorter parieto-supraoccipital process, and a larger and longer nuchal plate, nuchal plate length 0.9–1.0 in parieto-supraoccipital process length (vs. 1.1–1.7 in A. luniscutis), and nuchal-plate width at medial area 0.9–1.0 in parieto-supraoccipital process length (vs. 1.1–1.5 in A. luniscutis); nuchal plate granulose over its entire surface (vs. with half lateral surface smooth in A. quadriscutis), nuchal plate subquadrangular shaped, almost as long as wide (vs. nuchal plate subtrapezoidal or butterfly shaped, anterior portion always narrower than the posterior portion in A. quadriscutis), and lateral margin of the nuchal plate straight (vs. with a constriction at the medial portion in A. quadriscutis).