Ventogyrus [1] [2] [3] ( lat. Ventogyrus ) is a genus of organisms of the Ediacar biota , belonging to the type of petalons. Fossils were first discovered in the middle course of the Onega River of the Arkhangelsk Region by Leningrad geologist V.G. Chistyakov in the mid -1980s . Subsequently, V. G. Grazhdankin and A. Yu. Ivantsov discovered hundreds of fossils. Currently, it is one of the most studied Precambrian organisms [3] .
| † Ventogirus |
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| No rank : | Bilateral symmetrical |
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Ventogyrus
Ivantsov & Grazhdankin, 1997 |
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- Ventogyrus chistyakovi Ivantsov & Grazhdankin, 1997
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The ventogirus had an ovoid body, consisting of three identical lobes, separated by longitudinal partitions and possessing axial symmetry of the third order. Transverse partitions departed from the longitudinal partitions in two rows, dividing the body into separate cavities. The axial part of the body was a separate cavity in the form of a trihedral prism. On the surface of the longitudinal partitions and the central prism, imprints of a branched system of conducting vessels are preserved [2] . On each of the three faces of the central prism was the central trunk of the conducting system, from which the lateral branches departed in alternating order, bifurcated several times towards the outer surface of the body. A separate branch of the central trunk led into each transverse cavity of the body [3] .
Depending on the preservation of the partitions and the degree of filling of the chambers with sediment, the ventogirus forms fossils of various degrees of preservation [4] . Due to the softness of the wet sandstones of the Onega deposit, the fossils break on surfaces corresponding to partitions, which allows a detailed study of its internal structure [3] .
There is no unity among researchers regarding the ecology of ventogirus. Most likely, the ventogirus was a free-floating animal. There was a mouth at the pointed end of the body, and the central prism was a digestive organ. Swimming was carried out using cilia, covering the outer part of the body. Three large fields located at the posterior end of the body could carry tentacles driven by muscles, the presence of which is indicated by characteristic radially diverging folds. In many ways, the ventogirus is similar to modern ctenophores , with the exception of three-beam symmetry (ctenophores have two-beam or incomplete four-beam symmetry) [2] .
No organs for attachment to the bottom of ventogiruses were found, however, it is possible that they belong to the fragments of tubes found nearby, which acted as an attaching stem. M. A. Fedonkin also suggested that the ovoid body was a pneumatophore float that supported an organism or a colony of organisms unknown so far [3] .
