. Bulletins of American paleontology. 76 Bulletin 314 Tabellae that are convex upward are present in the septal region. They are inclined up toward the axis in early stages and become less steeply inclined with in- creased height in the coral. They are oriented hori- zontally in late stages. Tabulae in the axial region are mostly complete, moderately spaced, often dilated, and approximately horizontal (PI. 13, fig. 2). Microstmcture.—Septal fibers are well developed, and lamellae are present in the stereozone. Discussion.—The following specimens oi Lobocor- allium trilobatum trilobatum (Whitea
. Bulletins of American paleontology. 76 Bulletin 314 Tabellae that are convex upward are present in the septal region. They are inclined up toward the axis in early stages and become less steeply inclined with in- creased height in the coral. They are oriented hori- zontally in late stages. Tabulae in the axial region are mostly complete, moderately spaced, often dilated, and approximately horizontal (PI. 13, fig. 2). Microstmcture.—Septal fibers are well developed, and lamellae are present in the stereozone. Discussion.—The following specimens oi Lobocor- allium trilobatum trilobatum (Whiteaves, 1895) from the Gunn and Penitentiary Members of the Stony Mountain Formation at Stony Mountain, southern Manitoba, have been examined (Elias, 1981, p. 12): GSC 6825 (collected by T. C. Weston in 1884; this specimen is probably a syntype), 60757, 60763-60771. L. trilobatum vaurealense (Twenhofel, 1928) differs in having less pronounced trilobation, a larger axial structure that is slightly less dilated in the latest stages and consists of septal lamellae in addition to lobes, and in possessing fewer major septa at a particular cross-sectional area (Text-fig. 38). If L. trilobatum vaurealense was the immediate ancestor of L. trilo- batum trilobatum, it can be added to the possible evo- lutionary sequence Grewingkia robusta (Whiteaves, 1896) —> G. haysii (Meek, 1865) -^ L. trilobatum vau- realense -^ L. trilobatum trilobatum (see Elias, 1981, p. 6). L. trilobatum vaurealense could also have been a contemporary geographic variant of L. trilobatum trilobatum. It is closer to L. trilobatum trilobatum than to G. haysii, which is generally not as markedly trilobate and has less pronounced septal dilation and a better developed axial structure (see Elias, 1981, pp. 17, 18, pi. 5, figs. 1-15, pi. 6, figs. 1-12). These corals are therefore included in Lobocorallium, and are not considered sufficiently different from L. trilobatum trilobatum to constitute a separate species.
Size: 3243px × 771px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpaleontologicalresearchinstitutionit, bookcentury1900
