Protomonaxonid sponges standing around (as sponges do) on the enthusiastically bioturbated sediment of the Fezouata Shale, 478 million years ago in the Antarctic Circle.
These early demosponges have been given the rather cumbersome designation of 'Hamptonia' christi Form B, pending a formal description. Standing a few centimeters tall, they (and several other sponges found in Fezouata) formed dense but single-species assemblages interpreted as rapid and repeated colonization events in a hostile environment (Botting 2016).
I could not resist giving them the same coloration as their fossils, which are beautifully rendered in hues of iron oxides. Surely reds and oranges aren't unusual colors for sea sponges?
References:
Botting, J. P. (2016). Diversity and ecology of sponges in the Early Ordovician Fezouata Biota, Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology, 460, 75–86. https://doi.org/10.1016/j.palaeo.2016.05.018
Van Roy, P. (2006). Non-trilobite Arthropods from the Ordovician of Morocco. Gent University.
Odaraia alata, (yet another) strange arthropod of the Burgess Shale.
Unlike many of the 'weird wonders' of the Burgess like Hallucigenia or Opabinia, Odaraia was quickly identified as an arthropod (although its precise position remains unclear) but what sets it apart is its completely unique functional morphology: in addition to a very unusual telson with three flukes (quite reminiscent of the tail of a plane), Odaraia had a bivalved carapace that almost completely enclosed its body (Briggs & Whittington, 1981), like a living burrito with many legs.
Since the legs were unable to reach out beyond the shield, Odaraia must have spent its life swimming (possibly on its back like a fairy shrimp, based on its center of gravity), using its legs to create currents to guide food particles into the shield space and towards the mouth; the tail flukes likely assisted in stabilizing and steering. The whole animal was about 15 cm long (Briggs & Whittington, 1981).
In the background are Pirania muricata sponges, contemporary to Odaraia and also found in the Burgess Shale (Walcott, 1924).
References and notes about the reconstruction:
The cephalic appendages of Odaraia are poorly known; this reconstruction is based on the interpretation of Briggs & Whittington (1981), which consists of a pair of denticulated, mandible-like structures and, anterior to it, two possible pairs of simple segmented appendages - but the latter are highly uncertain and should be taken with caution.
Briggs, D. E. G., & Whittington, H. B. (1981). The arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 291(1056), 541–582. https://doi.org/10.1098/rstb.1981.0007
Budd, G. E. (2008). Head Structure in Upper Stem-Group Euarthropods. Palaeontology, 51(3), 561–573. https://doi.org/10.1111/j.1475-4983.2008.00752.x
Charles D. Walcott. (1924). Middle Cambrian Spongiae. In Cambrian Geology and Paleontology (Vol. 67, pp. 261–364). Smithsonian Institution. https://www.biodiversitylibrary.org/item/9442
