Abstract

An assemblage of large-diameter vertical burrows interpreted as lungfish estivation burrows is documented from the Upper Cretaceous (Maastrichtian) Maevarano Formation of northwestern Madagascar. These burrows suggest that lungfish were present in the Maevarano Formation paleofauna, and they are the first lungfish estivation burrows described from the rock record of Gondwana. Over 100 large-diameter burrows penetrate a pervasively cross-stratified fluvial sandstone body intercalated near the top of the Masorobe Member. The surface of this sandstone body was mapped and 74 burrows were documented in an area spanning ∼110 m2. Burrows cut through and deform surrounding foreset laminae, and in some cases impact surrounding strata up to 8 cm from the edges of individual burrows. In map view, the burrows exhibit three distinctive morphologies: circular, elliptical, and figure-eight shaped. These three map view cross sections are very similar to the modern burrow morphology of the African lungfish Protopterus when its burrow is exhumed along its full vertical expanse. Combined, these transverse-section views provide indication of lungfish estivation, and they are supplemented by several additional key characteristics, including spatial clustering (reflecting gregarious behavior), possible fin traces, and oxidized burrow margins. The localized occurrence of 100+ lungfish estivation burrows is consistent with previous reconstructions that posit a dryland paleoenvironment with a markedly seasonal wet-dry climate for the Maevarano Formation.

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