Tapinocephalid Dinocephalians From Middle Permian Zambia Show Both Lucas & Benton Wrong

Tapinocephalids (Therapsida, Dinocephalia) from the Permian Madumabisa Mudstone Formation (Lower Karoo, Mid-Zambezi Basin) of southern Zambia

Authors:

Sidor et al

Abstract:

Permian tetrapods from Zambia are best known from the Luangwa Basin, which was the subject of sporadic geological and paleontological work throughout the 20th century (Wallace, 1907; Dixey, 1937; Drysdall and Kitching, 1962, 1963; Attridge et al., 1964; Kemp, 1975, 1979; Davies, 1981; King, 1981; King and Jenkins, 1997; Lee et al., 1997). Based on its fossil content, the rocks of the upper member of the Madumabisa Mudstone Formation in the Luangwa Basin are considered Late Permian in age and contemporaneous with those of the Cistecephalus Assemblage Zone (AZ) of the Karoo Basin of South Africa (Angielczyk et al., 2014). Recent field work has demonstrated that a broadly distributed and relatively homogenous tetrapod fauna can be found wherever rocks of Cistecephalus AZ age are exposed across southern Africa (e.g., Malawi, South Africa, Tanzania, Zambia, and likely Mozambique; Sidor et al., 2013; Sidor, 2013).

Until recently, older tetrapod fossils from southern Africa were much rarer, with only South Africa and Zimbabwe recognized as yielding Middle Permian taxa (Catuneanu et al., 2005; Rubidge, 2005). The Karoo Basin has produced the most diverse fauna with the Eodicynodon and Tapinocephalus AZs including dicynodonts, dinocephalians, gorgonopsians, pareiasaurs, and therocephalians (Smith et al., 2012), although new radiometric dating suggests that the base of the overlying Pristerognathus AZ should be considered Middle Permian as well (Rubidge et al., 2013). Boonstra (1946) described the first dinocephalians from Zimbabwe. Unfortunately, this material now appears to be lost (Van den Heever and Grine, 1981; King, 1988). More recently, Lepper et al. (2000) described newly recovered material from the upper part of the Madumabisa Mudstone Formation of Zimbabwe and recognized both anteosaurid as well as tapinocephalian occurrences. The most recent discovery of Middle Permian tetrapods was reported by Simon et al. (2010), who noted the presence of isolated tapinocephalid remains from the middle portion of the Ruhuhu Formation of southern Tanzania. Endothiodont dicynodonts and temnospondyl amphibian remains from the same locality are currently under study by our research group.

Between 1951 and 1953, geologists from the Geological Survey Department of Northern Rhodesia were assigned to map coal reserves in the Mid-Zambezi Valley. Vertebrate fossils discovered in the course of their work were sent to S. H. Haughton for identification, and were subsequently published by Gair (1959:36) as “Dinocephalian and typical of the Tapinocephalus zone, possibly even Tapinocephalus itself.” Later, Drysdall and Kitching (1963:38) suggested that the fossils were fragmentary and unidentifiable. Unfortunately, none of the fossils was formally described and the collection now appears to be lost.

In 2010, members of our team relocated Gair's fossil site, and in July 2011 and June 2012 we collected additional tetrapod fossils there (Fig. 1; Table 1). Among them are numerous teeth that can be unambiguously referred to the tapinocephalid Dinocephalia (Boonstra, 1962; King, 1988). The discovery of this novel tetrapod assemblage provides useful biostratigraphic data for this portion of the Madumabisa Mudstone Formation in the Mid-Zambezi Basin.