Diverse assemblages of thecamoebians are reported here from the Early Permian Manjir Formation of the northwest Himalaya in India. These thecamoebian tests were found in palynological preparations and are assigned an Early Permian age based on co-occurrence of age-diagnostic palynomorphs. Several of them show very close morphological affinity with extant thecamoebian genera, such as
Thecamoebians characterize a special group of testate protists (agglutinated or autogenous) which belong to the Subphylum Sarcodina (
Distribution of fossil thecamoebian tests ranges from the Neoproterozoic through to the Holocene but their occurrence is patchy with wide gaps in the fossil record. The oldest undisputed record of thecamoebians is described as vase-shape microfossils (VSMs) from the Neoproterozoic rocks of Grand Canyon, USA by
Since thecamoebian tests are secreted (autogenous) and are proteinaceous, they are acid-resistant and have been reported in palynological preparations by
The Chamba Basin (Himachal Pradesh) ( Location map of the Khundi–Maral–Raula section in Chamba District, Himachal Pradesh, India. Lithostratigraphy of the Manjir Formation along the Khundi–Maral–Raula section (Siul River) in Chamba District, Himachal Pradesh, India.
Sample number (
Formation
Lithology
Thickness (m)
Black pyritized shale, carbonaceous shale, minor siltstone bands
Not measured
MANJIR FORMATION
Pebbly Unit P-4
Foliated calcareous, matrix-supported, bluish-grey pebbly horizon, matrix dominantly arenaceous, clasts of quartzite, shale and carbonate range from granular to small-pebble size.
341
12–11
Non-Pebbly Unit NP-3
Non-pebbly, non-calcareous, greyish-black slate and phyllite with occasional siltstone bands
428
Pebbly Unit P-3
Foliated calcareous, bluish grey matrix-supported pebbly slate/phyllite, clasts often have sericitic envelope ranging in size from granular to medium pebble, clasts include quartzite, shale and carbonate
157
10–6
Non-pebbly Unit NP-2
Black, greyish-black, non-calcareous bleached and limonitized pyritiferous shale/slate and siltstone with minor pockets of dolomite/dolomitic limestone
356
Pebbly Unit P-2
Grey, bluish-grey, calcareous, matrix-supported phyllite/slate and greenish quartzite, medium and small pebble clasts of quartzite, shale and dolomite/dolomitic limestone, stretched clasts conspicuous
315
5–1
Non-pebbly Zone NP-1
Grey, bluish-grey, non-calcareous, slate and phyllite with subordinate siltstone and black shale with occasional limonization
417
Pebbly Unit P-1
Foliated calcareous, matrix-supported pebbly slate/phyllite and quartzite with sparsely distributed translucent quartz vein granules in lower part
715
Fine-grained, greyish-green quartzite and phyllite
Not measured
Some samples from the pebbly units were also macerated for thecamoebians but were found to be barren. The present study is based on twelve samples that were collected along the Khundi–Maral–Raula section along the Siul River (
A total of 12 samples, five each from NP-1 and NP-2, and two from NP-3 were studied (
For the purposes of identification of Manjir Formation thecamoebians, and to compare their morphological affinities with extant thecamoebians, several modern lake/pond sediments were also studied from various parts of India. Sediment–water interface samples were collected mainly from the periphery of the lakes/ponds. Some 10g of air-dried sediment was warmed in 5% potassium hydroxide (KOH) to remove organic matter coagulation. After sieving through a 150 mesh (∼105 µm), the filtrate was kept overnight and the supernatant was decanted. The residue was acetolysed (
The three non-pebbly units NP-1, NP-2 and NP-3 yielded fairly good assemblages of thecamoebian tests ( Thecamoebian spectrum in Non-pebbly Units of the Manjir Formation, Himachal Pradesh, India. Some rare taxa omitted.
This lithological unit overlies the pebbly unit P-1 and is characterized by grey to bluish-grey, non-calcareous, slate and phyllite with subordinate siltstone and black shale. The thecamoebians show low counts but are dominated by
Separated by pebbly unit P-2, this non-pebbly unit is a black to greyish-black, non-calcareous shale/slate and siltstone with minor pockets of dolomite/dolomitic limestone. The overall thecamoebian count and taxonomic diversity are higher in this non-pebbly unit. The highest percentage occurrence was of
This unit is again separated by a pebbly unit (P-3) and is similar to NP-1 with a similar thecamoebian community. The sediment is non-pebbly, non-calcareous, greyish-black slate with occasional siltstone bands. The highest percentage of
During the Early Permian the uplands in Oman witnessed changes from a glacial monosaccate pollen-producing flora to a warmer climate bisaccate pollen-producing flora. A similar trend was also observed in Early Permian Manjir Formation palynomorph assemblages dominated by monosaccate pollen, such as
Late Carboniferous–Early Permian glaciation was widespread over Gondwana and sequences of marine and non-marine sediments are common in Permo-Carboniferous deposits. Widespread distribution of glacial sediments occurs in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia. During the Early Permian the location of the Chamba Basin would have been around 50–55°S latitude, making it a very cold region at that time ( Palaeogeography of Late Carboniferous–Early Permian Gondwana and distribution of glacigenic deposits (black shading). Location of Chamba Basin indicated by grey triangle. Modified after
Extant thecamoebians inhabit a wide variety of terrestrial environments, for example, fresh-water bodies such as lakes, ponds and rivers, slightly brackish and estuarine environments, and salt- and fresh-water marshes (
As discussed earlier, the oldest thecamoebians were described as VSMs from the Neoproterozoic rocks of Grand Canyon, USA by
Although extant testate amoebae are predominantly terrestrial, they are not totally absent from marginal marine environments, and members of both Testacealobosa and Testaceafilosa inhabit tidal pools and beach sands (
Kumar thanks King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia, and Farooqui and Jha thank the Director, Birbal Sahni Institute of Palaeobotany, Lucknow, India for permission to publish this paper. The authors also thank Profs Franco S. Medioli and David B. Scott of Dalhousie University, Canada for their constructive comments which have improved this paper. Dr Lameed Babalola of King Fahd University of Petroleum and Minerals kindly redrafted
Scientific Editing by Alan Lord.