Andrey Yu. Ivantsov

Reconstructing Rangea: New Discoveries from the Ediacaran of Southern Namibia

Abstract Rangea is the type genus of the Rangeomorpha, an extinct clade near the base of the evolutionary tree of large, complex organisms which prospered during the late Neoproterozoic. It represents an iconic Ediacaran taxon, but the relatively few specimens previously known significantly hindered an accurate reconstruction. Discovery of more than 100 specimens of Rangea in two gutter casts recovered from Farm Aar in southern Namibia significantly expands this data set, and the well preserved internal and external features on these specimens permit new interpretations of Rangea morphology and lifestyle. Internal structures of Rangea consist of a hexaradial axial bulb that passes into an axial stalk extending the length of the fossil. The axial bulb is typically filled with sediment, which becomes increasingly loosely packed and porous distally, with the end of the stalk typically preserved as an empty, cylindrical cone. This length of the axial structure forms the structural foundation for six vanes arranged radially around the axis, with each vane consisting of a bilaminar sheet composed of a repetitive pattern of elements exhibiting at least three orders of self-similar branching. Rangea was probably an epibenthic frond that rested upright on the sea bottom, and all known fossil specimens were transported prior to their final burial in storm deposits.

First finds of problematic Ediacaran fossil Gaojiashania in Siberia and its origin

We describe the first occurrence of the problematic fossil Gaojiashania outside China, in the Ediacaran Yudoma Group of the Siberian Platform. In both areas, Gaojiashania characterizes the lower upper Ediacaran strata and precedes the appearance of Cloudina and other skeletal fossils, which highlights its significance for the Ediacaran subdivision and correlation. Features of this fossil such as indeterminate length, the absence of a distinct growth pattern, and self-avoiding behaviour indicate its trace fossil origin but do not necessarily imply metazoan affinities for its producers. Several organisms including stem-group social amoebozoans and unicellular protists may have been Proterozoic trace fossil producers.

Discussion of 'First finds of problematic Ediacaran fossil Gaojiashania in Siberia and its origin'

Y. Cai & H. Hua comment: Zhuravlev, Gamez Vintaned & Ivantsov (2009) reported the problematic Ediacaran fossil Gaojiashania annulucosta in Siberia and they considered that this is the first find of Gaojiashania outside China, since Gaojiashania had previously only been reported from the Gaojiashan Member of the middle Dengying Formation in the Ningqiang area, southern Shaanxi Province, South China. However, we believe that the so-called Siberian Gaojiashania was mis-identified, and what was described as Gaojiashania annulucosta by Zhuravlev, Gamez Vintaned & Ivantsov (2009) is more appropriately ascribed to Shaanxilithes ningqiangensis , another problematic Ediacaran fossil that has also been known from the Gaojiashan Member in Shaanxi Province of South China (Chen, Chen & Lao, 1975; Xing et al . 1984), as well as the stratigraphically equivalent Taozichong Formation in Guizhou Province (Hua, Chen & Zhang, 2004) and the Jiucheng Member (Dengying Formation) in Yunnan Province of South China (Zhu & Zhang, 2005), the Zhoujieshan Formation in Qinghai Province (Shen et al . 2007), and the Zhengmuguan Formation in Ningxia Hui Autonomous Region of North China (Shen et al . 2007).

First macrobiota biomineralization was environmentally triggered

Why large and diverse skeletons first appeared ca 550 Ma is not well understood. Many Ediacaran skeletal biota show evidence of flexibility, and bear notably thin skeletal walls with simple, non-hierarchical microstructures of either aragonite or high-Mg calcite. We present evidence that the earliest skeletal macrobiota, found only in carbonate rocks, had close soft-bodied counterparts hosted in contemporary clastic rocks. This includes the calcareous discoidal fossil Suvorovella, similar to holdfasts of Ediacaran biota taxa previously known only as casts and moulds, as well as tubular and vase-shaped fossils. In sum, these probably represent taxa of diverse affinity including unicellular eukaryotes, total group cnidarians and problematica. Our findings support the assertion that the calcification was an independent and derived feature that appeared in diverse groups where an organic scaffold was the primitive character, which provided the framework for interactions between the extracellular matrix and mineral ions. We conclude that such skeletons may have been acquired with relative ease in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran biomineralization may have been either changing seawater Mg/Ca and/or increasing oxygen levels. By the Early Cambrian, however, biomineralization styles and the range of biominerals had significantly diversified, perhaps as an escalating defensive response to increasing predation pressure. Indeed skeletal hardparts had appeared in clastic settings by Cambrian Stage 1, suggesting independence from ambient seawater chemistry where genetic and molecular mechanisms controlled biomineralization and mineralogy had become evolutionarily constrained.

Molecular fossils from organically preserved Ediacara biota reveal cyanobacterial origin for Beltanelliformis

The Ediacara biota (~575–541 million years ago) mark the emergence of large, complex organisms in the palaeontological record, preluding the radiation of modern animal phyla. However, their phylogenetic relationships, even at the domain level, remain controversial. We report the discovery of molecular fossils from organically preserved specimens of Beltanelliformis, demonstrating that they represent large spherical colonies of cyanobacteria. The conservation of molecular remains in organically preserved Ediacaran organisms opens a new path for unravelling the natures of the Ediacara biota.Organic preserved biomarkers in specimens of Beltanelliformis reveal that these enigmatic members of the Ediacara biota were benthic colonial cyanobacteria.

Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals

Confirming the identity of early animals The first complex organisms emerged during the Ediacaran period, around 600 million years ago. The taxonomic affiliation of many of these organisms has been difficult to discern. Fossils of Dickinsonia, bilaterally symmetrical oval organisms, have been particularly difficult to classify. Bobrovskiy et al. conducted an analysis using lipid biomarkers obtained from Dickinsonia fossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals (see the Perspective by Summons and Erwin). Thus, Dickinsonia were basal animals. This supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago. Science, this issue p. 1246; see also p. 1198 Lipid biomarkers extracted from organically preserved Ediacaran macrofossils unambiguously clarify their phylogeny. The enigmatic Ediacara biota (571 million to 541 million years ago) represents the first macroscopic complex organisms in the geological record and may hold the key to our understanding of the origin of animals. Ediacaran macrofossils are as “strange as life on another planet” and have evaded taxonomic classification, with interpretations ranging from marine animals or giant single-celled protists to terrestrial lichens. Here, we show that lipid biomarkers extracted from organically preserved Ediacaran macrofossils unambiguously clarify their phylogeny. Dickinsonia and its relatives solely produced cholesteroids, a hallmark of animals. Our results make these iconic members of the Ediacara biota the oldest confirmed macroscopic animals in the rock record, indicating that the appearance of the Ediacara biota was indeed a prelude to the Cambrian explosion of animal life.

PaleoParks - The Protection and Conservation of Fossil Sites World-Wide

The world-famous Vendian (Ediacaran) fossil biota in the White Sea - Arkhangelsk region of Russia contains some of the most exquisite fossils of the earliest macrobiota (560-545 million years old) on Earth. Over 600m of continuously fossiliferous strata consisting of fine sand, silt and mud crop out at many localities along the White Sea. The fossils have been under study for decades in Moscow and that work continues. These fossils represent unusual taxa of early metazoans, algae, microbial mats, and strange sedimentary impressions that represent a very early stage of development of animals on Earth. These unique fossils have been well publicized through exhibitions, newspaper articles, scientific research papers and various web sites. As a result and in spite of their remote location, they are endangered by unauthorized fossil collectors. These paleo-pirates violate local and national laws, destroy fossils and fossil sites, and leave debris and garbage in the area. Some scientific papers are, surprisingly, based on illegally-collected fossils. Other illegal fossils have been offered for sale by commercial fossil dealers, chiefly at meetings or through web purchases. Paleo-piracy of the Vendian biota must be stopped. The collection of fossils has been illegal since February 2000 by the authority of the Administration of the Arkhangelsk Region and the Northern Committee of Natural Resources of the Russian Ministry of Natural Resources. Presently, the Ministry of Internal Affairs and Federal Security Service are prepared to protect the Vendian localities by arresting pirates. Recommendations to control paleo-piracy in the White Sea region include finalizing the establishment of World Heritage Site status, educating the local people in the values of the fossils and the need for their protection, establishment of a procedure for licensing for the collection of some fossils, and the notification to sellers of Vendian material by Russian authorities that the fossils were obtained illegally and hence are the property of Russia.