Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic ...Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and tria-romatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.展开更多
Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds...Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference.展开更多
文摘Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and tria-romatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.
文摘Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference.
