582
Journal of Paleontology 92(4):577–595
Table 1. Descriptive statistics of Cystomeson sierraensis n. gen. n. sp. (18 colonies). All measurements in mm. N=number of measurements, X=mean, SD=sample standard deviation, CV=coefficient of variation, MIN=minimum value, MAX=maximum value.
Branch width Exozone width Endozone width Aperture width Aperture spacing Vesicle diameter
N X SD CV MIN MAX 18 1.44 0.291 20.23 0.95 2.25
Axial zooecia diameter 12 0.25 0.039 15.51 0.17 0.30
18 0.31 0.108 34.85 0.15 0.50 18 0.82 0.213 25.92 0.51 1.25 25 0.14 0.022 15.75 0.11 0.19 20 0.33 0.060 18.10 0.24 0.49 20 0.12 0.032 26.34 0.05 0.17
Holotype.—NMMNH P-79594. Tierra Blanca Member of the Lake Valley Formation, Mississippian (Osagean); northwestern slope of Apache Hill, north of the Lake Valley mining district in the southwestern part of Sierra County, New Mexico, USA (type locality of the Lake Valley Formation: see Krainer and Lucas, 2012).
Paratypes.—NMMNH P-79579, P-79580, P-79583, P-79586, P-79589 to P-79593, P-79595 to P-79599, P-79601, P-79606, P-79609, P-79610 to P-79612, P-79614, P-79615, P-79618, and P-75158 to P-75160.
Diagnosis.—As for the genus.
Occurrence.—Andrecito and Tierra Blanca members, Lake Valley Formation, Mississippian (Osagean); Sierra County, New Mexico, USA.
Description.—Erect branched colonies, 0.95–2.25mm in dia- meter, with 0.15–0.50mm wide exozones and 0.51–1.25mm wide endozones. Two to five long, large zooecia developed in axial region, polygonal in transverse section. Autozooecia deriving from axial zooecia, recumbent at their bases, semi- circular to trapezoidal at their bases in endozone. Diaphragms in axial zooecia present, straight, widely spaced. Hemiphragms in exozone abundant, spine-like, arranged in alternating pattern. Lunaria horseshoe-shaped, laminated, positioned proximally, with ends not inflecting autozooecial chambers. Vesicles com- mon, flat, low, restricted to exozone, up to eight surrounding each autozooecial aperture. Layer of laminated calcitic material developed on colony surface, 0.10–0.25mm thick. Acanthos- tyles in calcitic layer, 0.02–0.03mmin diameter, with laminated sheaths and hyaline cores. Heterozooecia absent. Maculae absent. Autozooecial walls granular, locally crenulated, 0.010– 0.015mm thick.
Etymology.—The species name refers to Sierra County, the place where it was discovered.
Remarks.—As for the genus.
Family Cystodictyonidae Ulrich, 1884 Genus Cystodictya Ulrich, 1882
Figure 5.
Type species.—Cystodictya ocellata Ulrich, 1882, by original designation. Lower Mississippian; Kentucky, USA.
Diagnosis.—Bifoliate colony, strap-like, branching in plane of mesotheca. Autozooecia with peristomes and lunaria. Ridges between autozooecial rows lacking. Mesotheca thin to moderately thick, indistinctly laminated to granular-prismatic, with low ridges, running parallel to ranges of autozooecia. Autozooecia teardrop-shaped at their bases, quadrate in trans- verse section, partly isolated by box-like vesicles; recumbent portion short; blunt proximolateral hemisepta at zooecial bend, indenting zooecial cavity and producing slight hook-shaped appearance of autozooecia in deep tangential section. Diaphragms lacking. Walls laminated; boundary serrated; tubules in cortex. Lunarium in exozone, light-colored, lami- nated, some with core and proximal rib. Compound range walls thin in endozone with dark boundaries continuous into dark central layer of mesotheca; thick in exozone with many flexures and irregular tubuli. Vesicles small, box-like, in endozone; low blisters in inner exozone; stereom in exozone; laminated with tubuli and flexures.
Occurrence.—Middle Devonian–Pennsylvanian; worldwide.
Remarks.—Cystodictya differs from Sulcoretepora d’Orbigny, 1849 by its teardrop-shaped apertures, straight mesotheca, and autozooecial walls, which are distinctly tripartite in Sulcoretepora and more homogenous in Cystodictya. Further- more, Cystodictya possesses hemisepta, which are absent in Sulcoretepora. Cystodictya differs from Dichotrypa Ulrich in Miller, 1889 by the absence of acanthostyles in exterior stereom.
Cystodictya lineata Ulrich, 1884 Figure 5.1–5.4; Table 2
1884 Cystodictya lineata Ulrich, p. 37, pl. 2, figs. 4, 4a–c.
Holotype.—USNM PAL 43652, Keokuk limestone, Mississippian; Kings Mountain Tunnel, Kentucky, USA
Occurrence.—Tierra Blanca Member, Lake Valley Formation, Mississippian (Osagean); Sierra County, New Mexico, USA (present paper). Keokuk Limestone (Osagean), Mississippian; Kentucky, USA.
Description.—Bifoliate branches, 3.13–3.25mm wide and 0.9–1.0mm thick. Mesotheca 0.025–0.030mm thick, three- layered with two light-colored partitions separated by dark median lining; median tubules absent. Autozooecia tubular, teardrop-shaped at their bases, trapezoidal to semicircular in transverse section, quadrate in cross section, recumbent on mesotheca for relatively short distance, then bending upward at low angles in exozone and intersecting surface almost perpen- dicularly. Diaphragms lacking; long proximolateral hemisepta present at zooecial bend. Autozooecial apertures circular to oval,
(1–4) Cystodictya lineata Ulrich, 1884: (1, 2) NMMNH P-79594, tangential section showing autozooecia with hemisepta and vesicles;
(3, 4) NMMNH P-79617, transverse section showing autozooecia, mesotheca, and vesicles. (5) Sulcoretepora nitida (Ulrich, 1890), NMMNH P-79605, oblique section of a branch showing autozooecia, stereo, and mesotheca. Scale bars = 0.5mm.
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