Sabellidites, the first annelid?

[connorp]

I have noticed lately that a lot of fossils of so called Sabellidites cambriensis are popping up on a lot of sites for sale. They're sold as basal annelid worms that arose during the terminal Ediacaran. They predominantly are coming from the Lontova formation, dated at ~541-545 Mya, which is more or less the Ediacaran/Cambrian boundary. I would think that such fossils would be of great interest to researchers since, assuming they are basal annelids, they would represent one of, if not the first, appearances of a modern phylum in the fossil record. Yet the literature on this species is very sparse, with no more than half a dozen papers having been published since it's initial description in 1926. Does anyone here have any information on this subject?

[stoodleypike]

Hi,

I made these notes about a Sabellidites in my own collection. Hope they may be of use to you.

 

 

The oldest Cambrian rocks in Estonia were formed during the Baltic stage of the basin development when most of present-day Estonia was underwater. By the end of the Lontova Stage the entire East European Platform had risen above sea level.

 

Writing of the Zone of The East European Platform, Moczydlowska and Vidal (1986) stated ‘We contend that this radiation event of algal plankters is synchronous in the investigated areas and suggest that it might be generally significant for defining the Precambrian-Cambrian boundary.’

 

In terms of Vendian stratigraphy, the Ediacaran/Cambrian boundary is customarily represented by the Rovno/Lontova boundary. However, in the opinion of Keller, Mens and Rozanov (in Rozonov and Lydka, 1987), ‘the data suggests that geologically the Rovno and Lontova Stages form more or less a single whole, and the appearance of platysolenitides and sabellidites in the Rovno Stage allows us to assign it to the Cambrian, rather than to the Vendian.’

 

In a study of the Dividalen Group of Northern Sweden, Jensen and Grant (1998) likewise found evidence of Sabellidites sp. in rocks that correlated in age to the Rovno Stage.

 

‘The Lower Cambrian siliciclastic rocks of the Lon­tova, Lükati and Tiskre formations are exposed in northern Estonia.The oldest rocks of Cambrian age in Estonia belong to the Lontova Stage. The name Lontova was introduced by A. Öpik in 1933 to designate the upper part of blue clay beds.The rocks of the Lontova Stage crop out at the foot of the North Estonian Klint and thus extend as a nar­row belt from Tallinn to Narva.The main exposures are the clay quarries at Kolgaküla (abandoned), Kunda and Aseri.The maximum thicknesses (close to 90 metres) of the Lontova Stage are recorded in NE Estonia and the beds thin out southwards due to post-depositional denudation.The Lon­tova rocks in Estonia overlie the thinly laminated Ediacaran claystones of the Kotlin Stage with the gap in sedimentation in between. Lithologically the rocks of the Lontova age are represented by siliciclastic rocks with a distinct gradual lateral variation: argillaceous claystones (Lontova Forma­tion) prevail in eastern and central Estonia… The following members have been distinguished in Lontova Formation from base to top: Sämi, Mahu, Kestla and Tammneeme’ (Bauert, 2013).

 

According to Mens and Isakar (1999), ‘The Lontova Formation occurs in northern, eastern, and central Estonia and is represented by greenish-grey and variegated argillaceous rocks with interbeds of coarse- to fine-grained sandstone in the lower- and uppermost parts’

 

The blue clays of the Kopli peninsula have served for centuries as raw material in the manufacture of rough ceramic products (roof tiles, bricks, etc.) and cement.The clay quarries are now closed.

 

Sabellidites was discovered near Petrograd in 1925 by M. E. Yanishevsky; he assigned it to the sedentary Polychaeta. Further examples were later found in other parts of the East European Platform, China, Serbia, Canada and northern Scandinavia.

 

According to Fedonkin (in Sokolov and Iwanowski, 1985) the order Sabellidites incorporates two families. ‘The family Sabelliditidae Soklov… includes several genera: Sabellidites Yanichevsky 1926; Parasabellidites Sokolov 1967; Paleolina Sokolov 1965. The family Saarinidae Sokolov 1965… includes two genera: Saarina Sokolov 1965 and Caluptrina Sokolov 1965.’

 

Two further species of Sabellidites have since been identified, both from Yunnan province in southern China: Sabellidites yunnanensis Luo and Zhang, 1986 and Sabellidites badaowanensis Luo and Zhang, 1986.

 

Ivapstov (1991) describes Sabellidites cambriensis as consisting of ‘slender tubules of organic matter, predominantly black with a glossy surface, usually flattened and, therefore, with a ribbon-like appearance. Evidentally, flattening of the tubule occurred before burial, since strongly flattened tubules are often twisted in longitudinal spirals or matted into balls. The width of the ribbons ranges from 0.5 – 2 mm, the length from 10 - 20 mm, sometimes up to 100 mm, but the latter are only fragments of longer tubules. Their surface is either nearly smooth, with fine furrows, or wrinkled. Coarse wrinkles give the appearance of segmentation, though whether it is actual segmentation is not entirely clear. Evidently a substational percentage of wrinkling was caused by longitudinal compaction or bending of the tubules.’

 

In the words of Ou (2016), ‘Sabellidites was a tubular animal that lived about 542 million years ago. It has a pure-organic tube, giving it a black and sometimes shiny look. The surface of the tube is either smooth, with fine furrows or wrinkled. The characteristically wrinkled tubes are 0.2–3.0 millimeters wide and up to 16 cm long. But flattening always happened during burying, so most of the Sabellidites fossils have a ribbon-like rather than a tubular appearance.

 

‘Contemporaneous to Sabellidites are other diverse animals, which have a hard bio-mineralizing skeleton, such as Sinotubulites, Cloudina, Namacalathus and Namapoikia. Quite different from them, Sabellidites is unique for its organic tube. The tube has discrete layers composed of differently orientated fibers embedded in an amorphous matrix.’

 

Moczydlowska, Westall and Foucher (2014) found that ‘The Sabellidites organic body is preserved without permineralization. Minerals have not replicated any part of the soft tissue and the carbonaceous material of the wall is primary, preserving the original layering of the wall, its texture, and fabrics.’

 

The organic parts of Sabellidites specimens are resistant to water, mineral solutions, and the processes of burial and diagenesis.

 

Its organic preservation in three-dimensions is due to ‘its robustness and its property as an organic material of biochemical resistance, as well as burial under anaerobic conditions at the water-sediment interface that was created by the bacterial decay of mass growth and the accumulation of microbial organisms and biofilms in a restricted, shallow marine basin below the wave-base level (Moczydlowska, Westall and Foucher, 2014).

 

A study of Sabellidites using high-resolution computed tomography (SEM) revealed that the surface is tubular and is  a 'regular cross-folded sculpture, without regular segmentation. Tubular walls consist the two layers. The framework of internal layer is a longitudinally oriented fibers and the framework of outer layer is a chaotically interwoven fibers. There are many crystals of pyrite (FeS₂) on the surface of tubular and inside of the body. However the walls of tubular are not pyritized. The pyrite is a result of replacement during post-mortam fossilization process… Composition of white spheres was determined by microprobe analysis. The replacement of organism body was not uniform - there are pyritization, calcification and siliceous with organic ingredient fragments intermixed. Probably the tubular was external skeleton and only soft tissues have been replaced. Nano-CT study shown two-layers structure of tubular’ (Plotkina, Kulkov, Golubkova and Kushim, 1990).

 

Along with other workers, Moczydlowska, Westall and Foucher (2014) note that, ‘The fossil Sabellidites cambriensis Yanishevsky, 1926, derived from the terminal Ediacaran strata, is the earliest known organically preserved animal that belonged to a newly evolving fauna, which replaced the Ediacara-type metazoans… The highly ordered and specific pattern of fiber alignment (i.e., the texture of organic matter) is similar to that of representatives of the family Siboglinidae.’

 

‘The phylogenetic affinities of S. cambriensis are unclear. Its morphology and presumed chitinous tube material led Sokolov (1972) to propose a pogonophoran affinity. Today the phyla Pogonophora and Vestimentifera are placed in the polychaete family Siboglinidae (Rouse and Fauchald, 1997)… Moczydłowska et al. (2014) revealed that the microstructure and biogeochemical features of the organic tubes in Sabellidites have a chitinous-proteinaceous fibrous composition matching that of extant siboglinid tubes’ (Hybertsen, 2017).

 

Evidence from biogeochemistry show that the organic tubes of  Sabellidites contain β chitin. The closest animal, which has both β chitin and is similar in its morphology is the family Siboglinidae. Thus some scientists group Sabellidites as an extinct member of the family Siboglinidae within the phylum Annelida.

 

Siboglinidae, also known as beard worms, are a family of extant polychaete annelid worms whose members make up the former phyla Pogonophora (the giant tube worms) and Vestimentifera. They live in sediments at ocean depths from 100 to 10,000 meters. Siboglinids are, on average, less than 1 millimeter in diameter and 10–75 centimeters in length. The tubes are often clustered together in large colonies. The worms have a complex closed circulatory system and a well-developed nervous system, but as adults, siboglinids lack a functional mouth, gut and anus. Their primary nutrition is derived from the sulphide-rich fluids emanating from hydrothermal vents. The sulphides are metabolized by symbiotic hydrogen sulfide- or methane-oxidizing bacteria living in an internal organ, the trophosome. One gram of trophosome tissue can contain one billion bacteria. Siboglinids are either male or female (dioecious.) The fertilized eggs hatch to produce small paramecium-like larvae which, upon maturing, lose the ability to move freely and become sessile.

 

Weiguo, Guixiang and Benhe (1986) found that Sinosabellidites Zheng ‘a worm-like organism of questionable metazoan’ from the Liulaobei Formation (850 Ma) bore a superficial resemblance to Sabellidites but doubted that the relationship went any deeper.