Anabarella Explained

Anabarella is a species of bilaterally-flattened monoplacophoran mollusc, with a morphological similarity to the rostroconchs.^[1] Its shell preserves evidence of three mineralogical textures on its outer surface: it is polygonal near the crest of the shell, subsequently changing to both spiny and stepwise.^[1] Its internal microstructure is calcitic and semi-nacreous.^[2] Its name reflects its provenance from Anabar, Siberia.^[1] It has been interpreted as ancestral to the rostroconchs, and has been aligned to the Helcionellidae.^[3]

The genus is closely related to Watsonella, with which it bears many morphological similarities, including a laminar internal shell microstructure said to connect it with the early bivalves Fordilla and Pojetaia.^[4]

Notes and References

1. Kouchinsky . A. V. . 1999 . Shell microstructures of the Early Cambrian Anabarella and Watsonella as new evidence on the origin of the Rostroconchia . Lethaia . 32. 2 . 173–180 . 10.1111/j.1502-3931.1999.tb00537.x.
2. Vendrasco . Michael J. . Porter . Susannah M. . Kouchinsky . Artem . Li . Guoxiang . Fernandez . Christine Z. . New data on molluscs and their shell microstructures from the Middle Cambrian Gowers Formation, Australia . Palaeontology . 53 . 1 . 97–135 . 2010 . 10.1111/j.1475-4983.2009.00922.x . free .
3. Gubanov . A. . Skovsted . C. . Peel . J. . Anabarella australis (Mollusca, Helcionelloida) from the Lower Cambrian of Greenland . Geobios . 37 . 6 . 719–724 . 2004 . 10.1016/j.geobios.2003.05.009 .
4. Vendrasco . M.J. . Checa . A.G. . Kouchinsky . A.V. . Shell microstructure of the early bivalve Pojetaia and the independent origin of nacre within the Mollusca . Palaeontology . 54 . 4 . 825–850 . 2011 . 10.1111/j.1475-4983.2011.01056.x . free .