Field of Science

Conical Problematica

Scattered throughout the fossil record are little mysteries, organisms whose remains have been preserved but which are not obviously relatable to any more familiar group. Either their remains are too simple to preserve much evidence of their affinities (as with the 'tubular problematica' I've discussed before), or they are too distinct from other organisms for their affinities to be clear, or both, or some other reason. Unless they are particularly common or otherwise significant, most of these problematica are probably doomed to remain so. Case in point:

The figures above show Asymmetroconus splendidus, described by Korde in 1975 from the Albian (early Cretaceous) of the Crimea. The photos are of thin sections of the fossils; the complete skeleton would have probably been shaped rather like a wine goblet. The largest specimens of Asymmetroconus were just under 8 mm in height. In the same paper, Korde described a number of similar fossils aged from the Albian to the Danian (earliest Palaeocene), assigning them all to the new order Asymmetroconida. Korde attributed the asymmetroconidans to the Hydroconozoa, a group of similar fossils he had himself described previously from the early Cambrian. Hydroconozoa have generally been assigned to the Cnidaria, though their exact position therein remains obscure. Asymmetroconida resembled hydroconozoans in being small and goblet-shaped, with a conical interior to the cup and a basal globular hollow below the point of the cone. However, they differed from Cambrian hydroconozoans in their skeletal microstructure and in the asymmetry of the cup, with one side much thicker than the other. Rozanov & Zhuravlev (1992) later dismissed the idea of Mesozoic hydroconozoans, stating simply that structures described as such had 'little in common with this group'. No alternative identification of the Asymmetroconida has ever been proposed, and they do not appear to have been properly studied since Korde's original description.

Reconstruction of the hydroconozoan Hydroconus mirabilis, from Rozanov & Zhuravlev (1992). Whether actually related or not, the Asymmetroconida would have probably looked superficially similar.


Korde, K. B. 1975. [Hydroconozoa from Cretaceous and Palaeocene deposits of the Crimea]. In: Shimansky, V. N., & A. N. Soloviev (eds) Razvitie i smena organičeskogo mira na rubeže Mezozoâ i Kajnozoâ. Novye dankye o razvitii fauny pp. 32-38. Nauka: Moscow. [in Russian]

Rozanov, A. Yu., & A. Yu. Zhuravlev. 1992. The lower Cambrian fossil record of the Soviet Union. In: Lipps, J. H., & P. W. Signor (eds) Origin and Early Evolution of the Metazoa pp. 205-282. Plenum Press: New York.


  1. If the microstructure doesn't resemble hydroconozoans, does it resemble anything else?

  2. Not a question I'm able to answer, unfortunately. There's been no discussion of the structure since the original publication (in which Korde referred to the distinction). Not being conversant with Russian myself, I was making do with cutting and pasting blocks of text from the description in Google Translate, so I wasn't able to follow the exact technical details. Korde didn't compare the Asymmetroconida with anything in the description other than hydroconozoans.

  3. I don't reckon this is a cnidarian as the stem is articulated, and your image shows a solid stem. Cambrian to cretaceou is plenty of time for ditantly related phyla to converge superficially on a assymetrical cone morphology. What's more, I recon it's not a rhodophtye either (grr, my points!!) as the articulation is too delicate. So it still needs a phylum capable of producing articulated skeletal elements...I'm sticking with an animal, but if it's not an aberrant (asymmetric!) microcrinoid, then what.. (for thin-sections of supposedly 'stemless' roveacrinids, look up Farinacci's paper on the turkish fossils)? Someone needs to take a trip to the Crimea, find these asymmetricone fossil beds, and give us a beautiful 3-d SEM. Volunteers?

  4. A crinoid identity doesn't really seem appropriate because of (a) the irregularity of the articulation, and (b) the absence of a plate division between the two sides of the cup. I'm still at a loss; I think that some comparisons with algae would definitely be worth making, but Korde refers to these fossils being found in association with Codiaceae and Corallinaceae so presumably he was not entirely unfamiliar with fossil algae.

    To confuse matters, the figures of other asymmetricones (I like that vernacularisation, tah) in Korde (1975) don't seem to show the same basal articulation-like line (trying to use neutral terms here). Of course, being thin sections, there is always the potentially complicating factor of angle and position relative to the original fossil.

  5. Congratulations on rescuing the beleaguered Asymmetroconida from digital oblivion - now THREE pages on Google!

  6. I really like this points stealing rule (sorry, Reprobus).

    As for the Cretaceous Crimean calcareous cones, maybe it is possible that they are just an odd resting phase of a life cycle of a more familiar organism, say for instance an egg-case. The open top could just mean that all known specimens had hatched before preservation.

  7. Is it possible these are very young rugose corals before the first septa start growing, with asymmetry due to taphonomic processes?

    except they are too recent to be rugose coral

  8. Or a part of a bigger and more complex animal...? Anyway, the only way to find out is to find more fossils and get them out of their matrix so we can have a good look at them. My bet is that Assymetroconida would merge into something very familiar and we'd all be kicking ourselves.


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