PHYLOGENY 7 AULOSTYLUS PETALAXIS ACROCYATHUS STELECHOPHYLLUM FIGURE 1.-Morphology <strong>of</strong> the type species <strong>of</strong> the principal lithostrotionelloid genera. Acrocyathus: longitudinal and transverse thin sections ( x 4) <strong>of</strong> A. florijormis floriformis d'Orbigny (USNM 120235). Stelechophyllum: longitudinal and transverse thin section ( x 4) <strong>of</strong> S. venuk<strong>of</strong>fi altaicum (Tolmachev) (from Dobrolyubova and Kabakovich, 1966). Petalaxis: longitudinal and transverse thin sections (x 4) <strong>of</strong>P. maccoyanus Milne-Edwards and Haime (from Fedorowski and Gorianov, 1973). Aulostylus: longitudinal and transverse thin sections (x 6) <strong>of</strong> A. tubiferus tubiferus (Hayasaka) (from Sando, 1976).
8 REVISION OF LITHOSTROTIONELLA FROM THE CARBONIFEROUS AND PERMIAN questionably to Stelechophyllum and to regard them as possible derivatives <strong>of</strong> the Middle Devonian Endophyllum. If the Famennian forms in N ovaya Zemlya are referred questionably to Stelechophyllum, then there is a gap until the middle Tournaisian, when true Stelechophyllum appears and ranges into the upper Visean (fig. 2). In the. middle and upper Tournaisian, the axial structure was modified to an aulos in Aulostylus, which is a closely related <strong>of</strong>fshoot <strong>of</strong> Stelechophyllum. Increased complexity <strong>of</strong> the axial structure and the formation <strong>of</strong> conical tabulae took place in Acrocyathus, which ranges through most <strong>of</strong> the Visean. Acrocyathus seems to be an <strong>of</strong>fshoot <strong>of</strong> Stelechophyllum rather than a member <strong>of</strong> the Lonsdaleiidae, although it may have been the ancestor <strong>of</strong> Lonsdaleia (Actinocyathus). The earliest species <strong>of</strong> Petalaxis, which occur in the upper Visean, are similar to Stelechophyllum in the morphology <strong>of</strong> their septa and columella, but they have horizontal tabulae. Petalaxis . continues upward to the top <strong>of</strong> the Middle Carboniferous (Moscovian), but there is a gap in its record <strong>of</strong> occurrence in the Upper Carboniferous before it is seen again· in the Permian. The Permian species are very similar to Middle Carboniferous species. The significance <strong>of</strong> the gap is not now understood; the Permian forms may be merely homeomorphs in an unrelated phylogenetic stock. The second group <strong>of</strong> lithostrotionelloid corals includes two phylogenetic stocks that do not seem to be related to Stelechophyllum. Some species previously assigned to <strong>Lithostrotionella</strong> are herein placed in Lonsdaleia and Thysanophyllum, which are members <strong>of</strong> the Family Lonsdaleiidae. The origin <strong>of</strong> Lonsdaleia, which first appears at the top <strong>of</strong> the Tournaisian (Hill, 1940, p. 151), has been variously linked to Clisiophyllum (Vaughan, 1905, p. 184), Carcinophyllum (Vaughan, 1906, p. 148), and Thysanophyllum (Carruthers, in Garwood, 1912, p. 563; Smith, 1916, p. 235). However, E. W. Bamber (written commun., 1980) has pointed out that Acrocyathus pennsylvanicus and A. shimeri have axial structures and tabulation similar to those <strong>of</strong> the North American species <strong>of</strong> Lonsdaleia (Actinocyathus), that is, L. (A.) stelcki and L. (A.) peratrovichensis. Although these similarities suggest derivation <strong>of</strong> Lonsdaleia (Actinocyathus) from Acrocyathus in the Visean <strong>of</strong> North America, they are inconsistent with the earliest occurrence <strong>of</strong> Lonsdaleia in the upper Tournaisian <strong>of</strong> Great Britain. Thysanophyllum is characterized by a discontinuous axial structure and may be polyphyletic (Hill, ··1940, p. 161). For the present, the origins <strong>of</strong> Lonsdaleia and Thysanophyllum and their possible relationships to the Stelechophyllum stock remain obscure. · Other -Carboniferous corals previously assigned to <strong>Lithostrotionella</strong> are placed herein in Kleopatrina, a predominantly Permian genus. According to Minato and Kato (1965, test-fig. 4), Kleopatrina was derived from Durhamina, and all the members <strong>of</strong> the Durhaminidae were ultimately derived from the Lithostrotionidae in the Lower Carboniferous. Hence, Kleopatrina does not seem to be closely related to the main stock <strong>of</strong> lithostrotionelloid corals. SYSTEMATIC PALEONTOLOGY Morphologic terminology is generally that <strong>of</strong> Hill (1956). The term "tent-shaped" refers to tabulae that slope peripherally from their intersection with the columella at a slight angle to a distinct rounded shoulder, where they are vertical (see Stelechophyllum in fig. 1). These tabulae ordinarily terminate peripherally at a zone <strong>of</strong> horizontal tabellae without reaching the inner margin <strong>of</strong> the dissepimentarium and rest one upon the other. The term "conical" refers to tabulae that slope peripherally from their intersection with the columella at a moderate to steep angle without distinct shoulders and reach the inner margin <strong>of</strong> the dissepimentarium (see DEVONIAN LOWER CARBONIFEROUS /y-"'/ MIDDLE CARBONIFEROUS UPPER CARBONIFEROUS Serpu- Tournaisian Visean Bashkirian Moscovian Kasimovian Gzhelian khovian PEFIMIAN ACROCYATHUS (ACROCYATHIDAE) ? /sTELECHOPH'(LLUM (LITHOSTROTIONIDAE) ~-- \ \ AULOSTYLUS (LITH,STROTIONIDAE) PETALAX/S. (PETALAXIDAE) 7 _____ ---- ..;_ No record <strong>of</strong>l these corals ~· FIGURE 2.-Postulated phylogeny <strong>of</strong> the principal genera <strong>of</strong> lithostrotionelloid corals.
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