Palaeophragmodictya

Palaeophragmodictya is an extinct genus of sponge-grade organisms from the Ediacaran Period. Originally interpreted as a hexactinellid sponge,[1] the organism also bears some coelomate characteristics, including bilateral symmetry.[2][3]

Palaeophragmodictya
Temporal range: Late Ediacaran, 558–555 Ma
↓
Fossil of P. spinosa
Scientific classification
Kingdom: Animalia
Phylum: Porifera
Class: Hexactinellida
Order: †Reticulosa
Genus: †Palaeophragmodictya
Gehling & Rigby, 1996
Species
  • P. reticulata
    Gehling & Rigby, 1996
  • P. spinosa Serezhnikova, 2007

Morphology

The organisms take the form of a rounded, dome-like bag, 7–68 mm in diameter, with an uneven margin. Radial grooves define sac-like compartments within the bag. The radial pattern has an element of bilateral symmetry. A stalk emerges from the central point of some specimens, at the top of the organism; in life, it probably extended into the water column. Ray-like filaments radiate outwards from the edge of the bag.[2] Some structures in the organism have been interpreted as spicules.[1][4]

Ecology

The organisms have been interpreted as tall suspension feeders, reaching 10 cm or more up into the sea water above them.[1][5]

Original description

The genus was originally considered to be a member of the Dictyospongiidae family (hexactinellia), and was among the first Precambrian sponges to be described.[1]

Distribution

First found in the Pound group of Australia, fossils have also been recovered from the White Sea region of Russia.[2]

Other Sponge-Grade Ediacarans
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See also

References
  1. Gehling, J. G.; Rigby, J. K. (1996), "Long expected sponges from the Neoproterozoic Ediacara fauna of South Australia", Journal of Paleontology, 70 (2): 185–195, ISSN 0022-3360, JSTOR 1306383
  2. Serezhnikova, E. (2007), "Palaeophragmodictya spinosa sp. Nov., a bilateral benthic organism from the Vendian of the Southeastern White Sea Region", Paleontological Journal, 41 (4): 360–369, doi:10.1134/S0031030107040028, archived from the original on 2016-02-22, retrieved 2008-08-16
  3. Botting, J. P. (2007), ""Cambrian" demosponges in the Ordovician of Morocco: Insights into the early evolutionary history of …", Geobios, 40 (6): 737–748, doi:10.1016/j.geobios.2007.02.006
  4. Ivantsov, A. Y.; Malakhovskaya, Y. E.; Serezhnikova, E. A. (2004), "Some Problematic Fossils from the Vendian of the Southeastern White Sea Region" (PDF), Paleontological Journal, 38 (1): 1–9, archived from the original (PDF) on 2013-07-20
  5. Yuan, X.; Xiao, S.; Parsley, R. L.; Zhou, C.; Chen, Z.; Hu, J. (2002), "Towering sponges in an Early Cambrian Lagerstätte: Disparity between nonbilaterian and bilaterian epifaunal tierers at the Neoproterozoic-Cambrian transition", Geology, 30 (4): 363–366, doi:10.1130/0091-7613(2002)030<0363:TSIAEC>2.0.CO;2, ISSN 0091-7613


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