Thecamoebians from Late Permian Gondwana sediments of peninsular India |
| |
Institution: | 1. Instituto Geológico del Sur, Universidad Nacional del Sur, Departamento de Geología, San Juan 670, B8000ICN Bahía Blanca, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;1. British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK;2. Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow 226 007, India;1. Minia University, Faculty of Sciences, Geology Department, El-Minia, Egypt;2. Geological Survey of Austria, Neulinggasse 38, A-1030 Vienna, Austria |
| |
Abstract: | The evolutionary history of thecamoebians (testate amoebae) extends back to the Neoproterozoic Era. However, until now, these have had a restricted, discontinuous and modest record across the world. The studied sediment of Raniganj Formation (Godavari Graben), Andhra Pradesh, India has been assigned as Late Permian on the basis of co-occurring age-diagnostic Late Permian palynomorphs. About sixteen thecamoebian species and one taxon incertae sedis have been recorded here in the palynological slides on the basis of shell morphology and morphometry. Out of these, five belong to the family Arcellidae, seven to Centropyxidae, two to Trigonopyxidae, one to Difflugiidae, one to Plagiopyxidae, and one is regarded incertae sedis. The morphometric characteristics of fossil forms resemble their corresponding extant species studied from ecologically diverse fresh water wetlands in India. In general, the ratio of shell diameter and aperture diameter of Late Permian fossil and extant specimens show significant correlation in all the studied species. Except that, the ratio of shell length and breadth is the distinguishing feature between Centropyxis aerophila and C. aerophila ‘sylvatica’, rather than the ratio of shell length and longest diameter of the shell aperture in both fossil and extant forms. The study elucidates the minimal morphological evolution in thecamoebians and their survival during mass extinction periods and stressful environmental conditions over the geological timescale. |
| |
Keywords: | Gondwana Late Permian Morphostasis Raniganj Formation Thecamoebians |
本文献已被 ScienceDirect 等数据库收录! |
|