Protechiurus

Discovery

Fossil material of Protechiurus was discovered in the Aar Farm Member of the Dabis Formation, Kuibis Quartzite, in the Nama Group, Namibia in 1963, and was formally described and named in 1979.

Etymology

The generic name Protechiurus derives from the Greek word protos, to mean "first"; and the generic name Echiurus, a genus of spoon worm. The specific name derives from the Latinised surname of Dr. Stanley Joe Edmonds of the Department of Zoology, University of Adelaide and South Australian Museum.

Description

Protechiurus edmondsi is an elongated, hexahedral organism, growing up to 74 mm in length and with a width of 19 mm at its widest point. It is considerably narrow at one end and wide at the other, previously interpreted as the anterior and posterior ends respectively as an echiurid worm, now interpreted as the closed and open ends respectively as a tubular cnidarian. The body is also noted to be compressed, which may have been due to the body being made of an elastic material, along with six longitudinal ridges on the body, with the ones on the flatter sides being more prominent, although do not feature plates like Vendoconularia. Although more poorly preserved, there are also transverse lines along the length of the body, being tuberculate in shape.

Affinities

When originally described in 1979 by Martin Glaessner, the overall appearance of the Protechiurus saw it being assigned to the worm phylum Echiura, with the thinner end of the fossil being seen as a proboscis, and the longitudinal ridges being a feature only known to echiurid worms. In 1994, Protechiurus was then placed as a "vendobiont", alongside other similar bag-like organisms such as Ernietta and Pteridinium, in support of the Ediacaran fauna representing a distinct phylum, separate from modern phyla seen today. Later, in 2003, the placement as an ecdysozoan was then suggested for Protechiurus, again based on the appearance of the then singular fossil.

This all came to a head in 2019, when Ivantsov et al. had decided to not only restudy Protechiurus, but also the previously described Vendoglossa and Vendoconularia. They had noted many similarities between all organisms, from the general conical morphology, longitudinal ridges to transverse lines. Here the researchers synonymised Vendoglossa with Protechiurus, and erected a new family, Protechiuridae, which they postured may be a basal group to the cnidarian scyphozoans, being ancestral to both the conulariids and anabaritids, two families that share a similar appearance to the protechiurids like Protechiurus with tubular to conical bodies. Subsequent studies done after have noted that whilst a more detailed analysis is needed for Protechiurus to confidentially place it next to Vendoconularia phylogenetically, it does give support for Protechiurus (and Vendoconularia) possibly being a stem-group conulariid.

References

References

1. Seilacher, A.. (2007). "The Rise and Fall of the Ediacaran Biota".
2. (1979). "An echiurid worm from the Late Precambrian". Lethaia.
3. (December 2019). "Conical Thecae of Precambrian Macroorganisms". Paleontological Journal.
4. (2003). "Anatomical Information Content in the Ediacaran Fossils and Their Possible Zoological Affinities". Integrative and Comparative Biology.
5. (1994). "The Phylum Vendobionta: A Sister Group of the Eumetazoa?". Paleobiology.
6. (Mar 16, 2007). "The Rise of Animals: Evolution and Diversification of the Kingdom Animalia". JHU Press.
7. (July 2022). "Nonmineralized triradial conulariids from the lowermost Cambrian Stage 2 of the Olenek Uplift, Siberian Platform". Journal of Paleontology.