325 Mesozoic Fishes 5 – Global Diversity and Evolution, G. Arratia, H.-P. Schultze & M. V. H. Wilson (eds.): pp. 325-362, 21 figs., 2 tabs., 2 apps. © 2013 by Verlag Dr. Friedrich Pfeil, München, Germany – ISBN 978-3-89937-159-8 The first fossil shellear and its implications for the evolution and divergence of the Kneriidae (Teleostei: Gonorynchiformes) Matthew P. DAVIS, Gloria ARRATIA and Thomas M. KAISER Abstract A new genus and species of shellear (Gonorynchiformes: Kneriidae), †Mahengichthys singidaensis, is described from the Eocene Mahenge deposits in Tanzania, Africa. This work represents the first record of a fossil kneriid gonorynchiform fish. Previously, all gonorynchiform fossils have been attributed to either the families Chanidae or Gonorynchidae, with some taxa incertae sedis. We explore the phylogenetic position of †Mahengichthys singidaensis within the gonorynchiforms, utilizing parsimony and maximum likelihood methodologies that incorporate both morphological and molecular data. Our results indicate that †Mahengichthys singidaensis is a kneriid gonorynchiform within the tribe Kneriini, which includes the extant genera Kneria and Parakneria. This phylogenetic work provides a framework for estimating the divergence times of the Kneriidae for the first time using Bayesian methodology with calibrations that include information regarding extinct kneriids. We infer that the exclusively freshwater family Kneriidae most likely diverged and diversified during the Cretaceous to Paleogene in Sub-Saharan Africa, following the continent’s separation from South America. Introduction The order Gonorynchiformes includes seven extant and approximately seventeen extinct genera of fishes that exhibit incredible morphological diversity, with the clade dating back to the Early Cretaceous (FARA et al. 2010, POYATO-ARIZA et al. 2010a). There are three monophyletic families of gonorynchiform fishes, including the predominantly marine families Chanidae and Gonorynchidae, and the exclusively freshwater family Kneriidae distributed throughout Sub-Saharan Africa. While currently there is a general consensus regarding the monophyly of the order and each family, the relationships of the families to one another remains controversial, with conflict between molecular (LAVOUÉ et al. 2005, LAVOUÉ et al. 2012) and morphological (e. g., GRANDE & POYATO-ARIZA 1999, POYATO-ARIZA et al. 2010b) hypotheses. At present, the majority of previously described extinct genera are attributed to the families Chanidae and Gonorynchidae, with a few genera recognized as incertae sedis within the order (e. g., †Halecopsis, †Apul- ichthys). The only family that lacks a fossil representative is the exclusively freshwater family Kneriidae. In this study we describe the first fossil specimens of an extinct kneriid species collected in the fos- sil deposits of the ancient maar lake of Mahenge in Tanzania, Africa. The Cenozoic Mahenge deposits are considered to be one of the most important freshwater fish localities in Africa (GREENWOOD 1974, MURRAY 2000a, KAISER et al. 2006) due to the excellent preservation of the specimens, and the diver- sity of fish fauna previously described. Many taxa important to our broader understanding of teleostean relationships have been described from this locality, including the clupeid †Palaeodenticeps tanganikae GREENWOOD, 1960, two osteoglossomorphs †Singida jacksonoides GREENWOOD & PATTERSON, 1967, and †Chauliopareion mahengeense MURRAY & WILSON, 2005, a siluriform from the genus Chrysichthys (MURRAY 2003a), a characiform †Mahengecharax carrolli MURRAY, 2003b, and various cichlid taxa (e. g., GREENWOOD 1960, GREENWOOD & PATTERSON 1967, MURRAY 2000b) including the extinct genus †Mahengechromis MURRAY, 2000b, which are among the oldest cichlid fossils currently described from Africa. Additional material from the locality remains to be described, including non-cichlid percomorph taxa (KAISER et al. 2006).