584
Journal of Paleontology 92(4):577–595
Table 2. Descriptive statistics of Cystodictya lineata Ulrich, 1884 (2 colonies). Measurements and abbreviations as in Table 1.
Aperture width
Aperture spacing along branch 10 0.60 0.059 9.86 0.55 0.70 Aperture spacing diagonally 10 0.49 0.029 5.97 0.45 0.52 Vesicle diameter
10 0.07 0.021 30.12 0.04 0.10
arranged in 7 or 8 alternating rows on the colony surface. Lunaria distinct, horseshoe-shaped. Vesicular skeleton well developed, covered in exozone by thick stereom. Vesicles small, rectangular in tangential section, with rounded roofs, partly separating auto- zooecia at mesotheca, completely separating them in exozone in 1 or 2 rows. Stereom well developed, 0.19–0.30mm thick, con- sisting of laminated material, completely separating autozooecia in exozone.
Materials.—NMMNH P-79593, P-79594, and P-79617.
Remarks.—Cystodictya lineata differs from C. ocellata Ulrich, 1882 in having longer distances between aperture centers (0.40– 0.60mm vs. 0.40–0.50mm in C. ocellata). Cystodictya lineata differs from C. elegans Harlton, 1933 from the Mississippian of Oklahoma, USA, in having wider branches (3.13–3.25mm vs. 0.67mm in C. elegans).
Genus Sulcoretepora d’Orbigny, 1849
1884 Arcanopora Vine, p. 204. 1955 Mstania Schulga-Nesterenko, p. 175. 1960 Acanthopora Vine; Morozova, p. 86, incorrect subse- quent spelling.
Type species.—Flustra ? parallela Phillips, 1836, by sub- sequent designation (d’Orbigny, 1849); Mississippian; White- well, Yorkshire, England.
Diagnosis.—Colony of narrow bifoliate ribbons, dichot- omously branched in plane of mesotheca. Elongate, rounded autozooecia in ranges, rhombically arranged on lateral sides of branches. Lunaria elevated on proximolateral sides of autozooecia; range walls elevated; monticules absent; branch margins narrow, noncelluferous. Mesotheca with dark central layer and laminated outer layers; sharply folded in center, undulatory near branch margins; median tubules absent. Autozooecia full width and rec- tangular to parallelogram-shaped in deep tangential section; con- tiguous; alternating across
mesotheca.Compound range walls with dark median zone continuous into boundary zone in mesotheca; lateral zones laminated; branched dark zones and tubuli in thickened range walls in exozone. Autozooecia subquadrate to subhemispherical in cross section at mesotheca; angular, teardrop- shaped in deep tangential section in midexozone and partially isolated between range walls by small, blister-like vesicles. Lunaria laminated, indistinct. Vesicles adjacent to mesotheca only at
N X SD CV MIN MAX 10 0.18 0.011 6.11 0.16 0.19
noncelluliferous margins. Stereom laminated with tubules in endozone.
Occurrence.—Devonian–Permian; Europe, North America, and Asia.
Remarks.—The genus Sulcoretepora differs from the genus Cystodictya by the absence of hemisepta.
Sulcoretepora nitida (Ulrich, 1890) Figures 5.5, 6.1, 6.2; Table 3
1890 Cystodictya nitida Ulrich, p. 493, pl. 81, figs. 4, 4a–c.
Syntypes.—ISGS (ISM) 2737. Keokuk Group, Mississippian; Bentonsport, Iowa, USA
Occurrence.—Tierra Blanca Member, Lake Valley Formation, Mississippian (Osagean); Sierra County, New Mexico, USA (present paper). Keokuk Limestone, Mississippian; Iowa, USA.
Description.—Branched, bifoliate colonies, 1.6–2.5mm wide and 0.53mm thick. Autozooecia short, budding from straight mesotheca, trapezoidal to semicircular in transverse section at bases, rectangular in deep tangential section, becoming rounded in exozone. Mesotheca 0.005–0.010mm thick. Rare planar diaphragms present in autozooecia. Autozooecial apertures cir- cular to oval, arranged in 6 or 7 alternating rows on colony surface. Lunaria obscure. Vesicles common, flat, with rounded roofs, polygonal in midtangential section, moderate in size. Stereom weakly developed, laminated, containing small tubules. Autozooecial walls compound, 0.008–0.015mm thick in endozone. Indistinct longitudinal crests dividing apertural rows.
Materials.—NMMNH P-79603, P-79605, P-79607 to P-79609, and P-75159.
Remarks.—Sulcoretepora nitida differs from S. commutata Balakin, 1975 from the lower Viséan (Mississippian) of Uzbe- kistan in having narrower branches (1.6–2.5mm vs. 2.25– 4.25mm in S. commutata) and smaller autozooecial apertures (aperture width 0.10–0.13mm vs. 0.12–0.16mm in S. commu- tata). Sulcoretepora nitida differs from S. curvata Nekhor- oshev, 1956 from the Mississippian of Altai in having smaller autozooecial apertures (aperture width 0.10–0.13mm vs. 0.16– 0.20mm in S. curvata).
Order Cryptostomata Vine, 1884
Suborder Rhabdomesina Astrova and Morozova, 1956 Family Nikiforovellidae Gorjunova, 1975
Genus Nikiforovella Nekhoroshev, 1948
Type species.—Nikiforovella alternata Nekhoroshev, 1948, by original designation. Mississippian; Altai, Russia.
Figure 6. (1, 2) Sulcoretepora nitida (Ulrich, 1890), NMMNH P-79603, tangential section showing autozooecial apertures and vesicles. (3–5) Nikiforovella sp., NMMNH P-79580: (3) oblique section of a branch; (4) tangential section showing autozooecial apertures, metazooecia, and acanthostyles; (5) longitudinal section showing autozooecial chambers and metazooecia. Scale bars = 1mm (1, 3), 0.5mm (2, 4, 5).
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