Language:
English
Description:
The number of publications on and discoveries of new fossil lungfish species and genera has generally shown, despite some fluctuations, an increase in numbers. This is particularly the case in Africa, Australia and South America, where lungfishes still survive as an extant group. Australian lungfishes have received the most attention, with one possible reason being the declaration that the surviving Australian lungfish is an endangered species, and the number of research expeditions and active researchers based there over a long period of time. While Australia has received a great deal of attention, the evolution of African lungfishes, while noteworthy, has not been studied with the same level of intensity. This study focuses on newly discovered fossil lungfish specimens from Kenya and Tanzania, and then looks at Africa lungfish biogeography in a broader context. The Cretaceous fauna of Turkana, Kenya, includes a lungfish pterygopalatine tooth plate, which is here described as Ceratodus due to the possession of multiple ceratodontid features, including six separate ridges on the occlusal surface of the tooth plate, the characteristic curvature of the tooth plate, and the specimen’s length to width ratio of almost 2:1. Tooth plates from in the Late Oligocene fauna in the Rukwa Rift Basin (RRB) of southwestern Tanzania are here assigned to two different genera; Ceratodus and Protopterus. The i from RRB is smaller in size as compared to the Cretaceous specimen from Turkana but retains features typical of ceratodontid lungfish, and it is sufficiently distinct to be described as a new species -- Ceratodus mbedeae. Protopterus lungfish specimens from the RRB exhibit typical features of that genus, which survived to day in Africa, including three blade-like protruding tooth ridges and a relatively flat posterior angle in the upper jaw. The RRB Protopterus are not here consider sufficiently distinct to justify erection of a new species. Mapping parsimony analysis of endemism (PAE) of lungfish biogeography indicates significant changes over time. Of note are the much broader geographic distribution of lungfishes early in their history, contrasts in composition of Paleozoic versus Mesozoic assemblages, and the abrupt turnover of major groups at the end of the Devonian. Modern lungfish are today restricted to tropical regions of Africa, South America and Australia. The similarity dendogram generated by the PAE study results in three major clusters (clades), the first cluster that constitutes Australia and Europe appears to be very distinct from the other two, namely Africa, Madagascar and South America, and Asia and North America. Madagascar is shown to be more similar to South America than to Africa within that cluster.
Subject(s):
Geology ; Paleontology ; Geobiology
ISBN:
1369432542
ISBN:
9781369432541
Source:
ProQuest Dissertations & Theses Global
Source:
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