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Biform tabularia and periaxial cones in Lonsdaleia McCoy, 1849 (Rugosa)
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Biform tabularia in rugose corals show different orientations of peripheral parts of tabulae situated on opposite sides of minor septa. Periaxial cones form irregular conical structures partly enclosing other structural elements of axial column and represent combination of steeply elevated, vertically extended axial parts of tabulae or periaxial tabellae with elongated axial tabellae. Both structures are characteristic of cerioid genus Cystolonsdaleia Fomichev, 1953, but also develop within the limits of variability in Lonsdaleia McCoy, 1849, including in some cerioid Lonsdaleia (Actinocyathus) d’Orbigny, 1849 species, thus suggesting that Cystolonsdaleia could have evolved from Actinocyathus. Among Lonsdaleia species from the uppermost Viséan-lower Serpukhovian of the Moscow Basin, biform tabularia are documented in L. (Actinocyathus) crassiconus (McCoy, 1849), L. (A.) lativesiculosa (Dobrolyubova, 1958), and L. (Actinocyathus) sp. A; periaxial cones in L. (A.) bronni (Milne Edwards et Haime, 1851) and L. (A.) rossicus (Stuckenberg, 1904); both biform tabularia and periaxial cones are documented in L. (A.) floriformis (Martin, 1809), L. (A.) borealis (Dobrolyubova, 1958), L. (A.) subtilis (Dobrolyubova, 1958), L. (A.) gorskyi (Dobrolyubova, 1958), L. (A.) sarytschevae (Dobrolyubova, 1958), L. (Actinocyathus) sp. A, and L. (Lonsdaleia) duplicata (Martin, 1809).
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About: Maria R. Hecker
Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya Str., 123, Moscow, 117997, Russia; Department of Palaeontology, Royal Belgian Institute of Natural Sciences, Rue Vautier1000, Brussels, Belgium; email@example.com, Maria.Hecker@skynet.be