Ediacaran complex acanthomorphic acritarch assemblage from the Owk Shale of the Kurnool Group: Morphological insights through Confocal Laser Scanning Microscope

The Organic-Walled Microfossils (OWM), especially acritarchs, are essential in understanding eukaryotes’ early evolution and diversification in the Proterozoic Era. The study reports the fine-scale morphological features of the complex acanthomorphic acritarchs recovered from the Owk Shale of the Kurnool Group, Cuddapah Supergroup, South India. The acritarchs include Weissiella grandistella, Galeasphaeridium bicorporis, Galeasphaeridium sp., Germinosphera bispinosa and Tanarium tuberosum , which are characteristic of the Ediacaran age. Morphological features of all the recovered fossil forms were studied under high-power binocular microscopes and a Confocal Laser Scanning Microscope (CLSM), a new, non-destructive, non-intrusive method for detailed cellular morphology and anatomy, providing insight into three-dimensional morphology at micron-scale resolution. Many features were left unrecognised under the Transmitted-Light Microscopy (TLM). The present acanthomorphic acritarch assemblage of the Owk Shale closely resembles the Ediacaran Complex Acanthomorphic Palynomorphs (ECAP), which are of Ediacaran age. The rise in the complexity and diversity of the morphological features has been documented in the complex acanthomorphic acritarchs from the late Neoproterozoic sedimentary successions worldwide. The new assemblage strengthens the age of the Kurnool Group in favour of the Ediacaran. It adds information about the presence of the ECAP in the southern part of the Indian subcontinent.