A new fully marine, short-snouted lepisosteid gar from the Upper Cretaceous (Turonian) of North Africa

Abstract

Ganoine-scaled fishes belonging to the superfamily Lepisosteoidea, more commonly known as gars, are an ancient lineage with origins in the Mesozoic, first appearing in the Kimmeridgian, Late Jurassic. The Mesozoic gar fossil record is patchy, mostly consisting of disarticulated remains, with only a few partially or mostly complete specimens being extremely rare. Extant gars typically occur in freshwater and brackish environments, with rare observations of a few species frequenting saline waters although little is known of their marine ancestors. Here we describe a new genus and species, Grandemarinus gherisensis gen. et sp. nov., an unusually short-snouted gar from the Upper Cretaceous (Turonian) Akrabou Formation of Morocco. The short-snouted cranial bauplan is superficially convergent with the Eocene freshwater genera Cuneatus and Masillosteus, although a phylogenetic analysis resolves the new gar as the sister taxon to the Lepisosteini (Oniichthys, Lepisosteus, Atractosteus), falling outside of Masillosteinae (Masillosteus, Cuneatus). Gars likely originated as fully marine fishes during the Late Jurassic, and during Early Cretaceous times successfully invaded freshwater ecosystems. The new gar described here is likely a late surviving member of this early marine lineage. The new lepisosteiform is the first complete gar described from a Cretaceous marine deposit; representing a vital clue to help decipher the early evolution and ecology of Lepisosteidae. The taphonomy of the specimen is discussed within the context of a fully marine carbonate Konservat Lagerstätte.