Cichlid fish biodiversity in an Oligocene lake

Abstract

The Baid formation (Ad Darb locality, Tihamat Asir. SW Saudi Arabia) is Oligocene in age. The sediments have been deposited in one of a series of several alkaline continental lakes that once flanked the early Red Sea Rift. So far seven specimens of cichlid fish have been discovered there. They represent at least three different species. One species from endo-and exoskeletal characteristics can be assigned to the basal grade of cichlids, today represented mainly in Madagascar and India. The other two species seem to belong to two different clades within the African assemblage that today comprises more than 1000 species.

†Tugenchromis pickfordi, gen. et sp. nov., from the upper Miocene—a stem-group cichlid of the ‘East African Radiation’

“…dabanensis, 'Form C,' yP. kuluensis, and ?Heterochromis most probably have two predorsal bones (Van Couvering, 1982;Lippitsch and Micklich, 1998) and are therefore unlikely to be closely related to the Lake Tanganyika tribes (to which yT. pickfordi is assigned; see above), which generally have only one predorsal (this study).…”

“…All other fossil cichlid species from North and East Africa (Van Couvering, 1982) and from Saudi Arabia (Weiler, 1970;Lippitsch and Micklich, 1998) share some characters with yT. pickfordi.…”

“…pickfordi is assigned; see above), which generally have only one predorsal (this study). Moreover, ?Heterochromis sensu Lippitsch and Micklich, 1998, shows ctenoid rather than cycloid scales. 'Form D' can be separated from yT.…”

“…pickfordi and several fossil cichlids described in open nomenclature, because their lateral line and meristic counts are not known. Among these latter forms are 'Tilapiini Group 2' and 'Tilapiini Group 3' from the Oligocene of Saudi Arabia (Lippitsch and Micklich, 1998) (Table 3). Given their older age (Oligocene) and their geographical origin (Saudi Arabia), it is unlikely that yT.…”

The oldest fossil cichlids (Teleostei: Perciformes): indication of a 45 million-year-old species flock

“…Species £ocks in lacustrine habitats have been described for tilapiine and haplochromine cichlids from extant populations in Africa and a`riverine £ock' of cichlids has been described from South America (De Lucena & Kullander 1992). Other fossil cichlids from an Oligocene lake in Saudi Arabia were considered as belonging to several di¡erent lineages and, therefore, do not constitute a species £ock (Lippitsch & Micklich 1998). The Mahenge cichlids provide the ¢rst fossil evidence to indicate that the ability of the cichlids to form species £ocks arose prior to 40 Myr ago.…”