Friday, 13 March 2020


This well-preserved fossil fish skull is from Calamopleurus (Agassiz, 1841), an extinct genus of bony fishes related to the heavily armoured ray-finned gars.

They are fossil relics, the sole surviving species of the order Amiiformes. Although bowfins are highly evolved, they are often referred to as primitive fishes and living fossils as they retain many of the morphologic characteristics of their ancestors.

This specimen was found in Lower Cretaceous outcrops of the Santana Formation in the Araripe Basin UNESCO Global Geopark. The Santana Formation of north-east Brazil contains one of the most important Mesozoic fossil Konservat Lagerstatten on Gondwana (Maisey, 1991; Martill, 1993, 1997, 2001; Kellner, 2002; Fara et al., 2005). The formation crops out on the flanks of the Chapada do Araripe in southern Ceara´, western Pernambuco and a small part of eastern Piaui in the north-eastern Brazilian Caatinga. It forms part of a heterogeneous assemblage of spectacularly fossiliferous rocks of Cretaceous age (Gardner, 1841; Brito, 1984; Maisey, 1991; Martill, 1993).

Two formations within the basin are well-known as Konservat Lagerstatten; the Nova Olinda Member of the Crato Formation lies a few tens of metres below the Santana Formation, and both have contributed considerably to our knowledge and understanding of Gondwanan Cretaceous palaeobiotas (Martill, 1988, 1993; Wenz and Brito, 1990; Maisey, 1991, 1993; and many references herein). Only the age of the Romualdo Member of the Santana Formation, a dominantly silty shale sequence that includes the highly fossiliferous carbonate concretion-bearing unit, is considered here.

Although the Santana Formation concretions have been famous for their enclosed fossils, especially fishes, for over 150 years, in more recent times they have become known for a diversity of dinosaur and pterosaur remains in an excellent state of preservation (Martill, 1998; Martill and Unwin, 1989; Kellner, 1996a,b; Frey et al., 2003a,b) comparable with, and sometimes exceeding, that of the Jurassic Solnhofen Limestone of Bavaria (Barthel et al., 1990), especially in their three-dimensionality. Photo and collection of David Murphy.

References: Martill, David M. The age of the Cretaceous Santana Formation fossil Konservat Lagerstatten of north-east Brazil: a historical review and an appraisal of the biochronostratigraphic utility of its palaeobiota, Cretaceous Research 28 (2007) 895-920.