José Antonio Gámez Vintaned

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.

A New Early Cambrian Lobopod-Bearing Animal (Murero, Spain) and the Problem of the Ecdysozoan Early Diversification

A new xenusian, Mureropodia apae gen. and sp. nov., is found in the lower Cambrian of the Murero Lagerstatte in the Cadenas Ibericas, NE Spain. In Mureropodia, the lobopod length/body width ratio reveals that this animal hardly was able to walk on the bottom surface. Possibly, it could use the limbs for anchoring the body to the substrate. A well-developed dermomuscular sac of circular and longitudinal muscular systems as well as probably retractile proboscis fit such an interpretation. The ground plan of the Xenusia includes a vermiform body; a proboscis or mouth cone; paired lobopods with claws; a cuticle displaying a repeated anatomical patterning; a straight digestive tract with terminal mouth and anus. Morphologically heterogeneous xenusians, which crawled with their lobopods along the bottom, might give rise to four morphofunctional lineages – to cephalorhynch worms by adaptation for burrowing with retractable proboscis; to tardigrades by adaptation for interstitial habitat; to euarthropods by adaptation to walking on joint appendages; and to anomalocaridids by adaptation to swimming with lateral flaps.

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).

Upper Vendian-lowest Ordovician sequences of the western Gondwana margin, NE Spain

Abstract The intra-Vendian (Ediacaran)–intra-Tremadocian succession of the Cadenas Ibéricas in NE Spain is divided into nine sequences. Overall, these are interpreted as second-order sequences. Those that encompass Lower and lower Middle Cambrian carbonates, with identified transgressive systems tract (TST) and highstand systems tract (HST) phases, may constitute elements of composite sequences. The lowermost sequence is of Late Vendian age. In Lower and lower Middle Cambrian units, sequence tops indicate drowning, reflecting extensional tectonics. Rifting effects are traceable up to mid-Mid Cambrian times. The remaining sequences probably represent a sag phase, either accentuating the preceding extensional local basin regime or heralding the Gondwana passive margin stage. Of the southerly Gondwana deposits those of other areas of the Iberian Peninsula and of the Moroccan Anti-Atlas fold belt show similar conditions during the Early Cambrian, that is, an Early Cambrian extensional regime, and, as for the Moroccan fold belt, four sequences imaging TST and HST phases.