Ernst et al.—Mississippian bryozoans of New Mexico


Table 7. Descriptive statistics of Minilya sp. (2 colonies). All measurements in mm unless otherwise noted. Abbreviations as in Table 1.


Branch width


Dissepiment width Fenestrule width Fenestrule length


Distance between branch centers


Aperture spacing along branch Aperture spacing diagonally Maximal chamber width Node width


12 0.18 0.034 19.09 0.14 0.26 9 0.25 0.029 11.48 0.22 0.30 7 0.67 0.159 23.63 0.56 0.98 10 0.58 0.050 8.67 0.50 0.66


N X SD CV MIN MAX 8 0.38 0.042 11.27 0.30 0.43


591


Table 8. Descriptive statistics of Laxifenestella sp. (2 colonies). All measure- ments in mm unless otherwise noted. Abbreviations as in Table 1.


Branch width


Dissepiment width Fenestrule width Fenestrule length


Distance between dissepiment centers 12 0.91 0.176 19.33 0.74 1.15 Aperture width


Distance between node centers


8 0.11 0.012 11.38 0.09 0.12 9 0.36 0.024 6.60 0.34 0.41 4 0.32 0.018 5.71 0.30 0.34 8 0.18 0.012 6.74 0.16 0.20 15 0.06 0.014 22.97 0.04 0.09 15 0.20 0.020 10.11 0.15 0.23


Apertures per fenestrule length (no.) 7 2.6 0.535 20.79 2.0 3.0


Diagnosis.—Reticulate colonies consisting of relatively wide, thick branches and moderately wide dissepiments. Autozooecia arranged in two rows on branches, rectangular to pentagonal in midtangential section. Axial wall between autozooecial rows weakly undulating. Both superior and inferior hemisepta pre- sent. Narrow keel with single row of nodes developed (modified after Morozova, 2001, p. 44).


Occurrence.—Lower Devonian–upper Permian; worldwide.


Remarks.—Laxifenestella differs from Fenestella Lonsdale, 1839 in the rectangular to pentagonal shape of its autozooecia in mid- tangential section and the presence of well-developed hemisepta.


Laxifenestella sp. Figure 8.3–8.6; Table 8


Occurrence.—Tierra Blanca Member, Lake Valley Formation, Mississippian (Osagean); Sierra County, New Mexico, USA.


Description (exterior).—Reticulate colony formed by straight branches joined by relatively narrow dissepiments. Fenestrules oval to rectangular. Autozooecia arranged in two rows on branches. Autozooecial apertures circular, with low peristome; 4 or 5 apertures spaced per fenestrule length. Rounded nodes on the low keel, regularly spaced. Reverse side finely striated.


Description (interior).—Autozooecia relatively long, roughly pentagonal to rectangular in midtangential section, with short to moderately long vestibule in longitudinal section. Axial wall between autozooecial rows straight to weakly undulating; aperture positioned at distal end of chamber. Superior hemisepta long; inferior hemisepta indistinct. External laminated skeleton well developed, traversed by microstyles on both obverse and reverse sides. Microstyles 0.003–0.005mm in diameter. Het- erozooecia not observed.


N X SD CV MIN MAX 8 0.36 0.020 5.60 0.33 0.39


Distance between branch centers


Aperture spacing along branch Aperture spacing diagonally Maximal chamber width Node width


7 0.16 0.041 25.06 0.13 0.24 6 0.29 0.050 17.17 0.22 0.35 3 1.05 0.050 4.76 1.00 1.10 7 0.61 0.034 5.63 0.56 0.65


Distance between dissepiment centers 3 1.24 0.090 7.25 1.15 1.33 Aperture width


Distance between node centers


15 0.10 0.007 7.00 0.09 0.11 15 0.28 0.031 11.03 0.25 0.37 15 0.30 0.014 4.71 0.28 0.32 20 0.12 0.008 6.69 0.11 0.13 8 0.06 0.017 26.43 0.03 0.08 5 0.38 0.023 6.00 0.36 0.41


Apertures per fenestrule length (no.) 6 4.5 0.548 12.17 4.0 5.0 Materials.—NMMNH P-79604 and P-79607.


Remarks.—Laxifenestella sp. differs from L. juxtaserratula (Trizna, 1958) from the Mississippian (Tournaisian) of the Kuznets Basin in having wider branches (branch width 0.33– 0.39mm vs. 0.25–0.30mm in L. juxtaserratula) and larger fenestrules (fenestrule width 0.22–0.35mm vs. 0.20–0.22 in L. juxtaserratula; fenestrule length 1.00–1.10mmvs. 0.45–0.55 in L. juxtaserratula). The present species is similar to L. snyderi Gilmour and McColloch, 1995 from the Otter Formation (Viséan) of Montana, but differs from it in its spacing of 4 or 5 apertures per fenestrule length instead of 3 of 4 in the latter species, as well as in having wider spacing of branches (average distance between branch centers 0.61mm vs. 0.47mm in L. snyderi).


Genus Spinofenestella Termier and Termier, 1971 1971 Alternifenestella Termier and Termier, p. 42.


Type species.—Fenestella spinulosa Condra, 1902, by sub- sequent designation (Termier and Termier, 1971). Lower Per- mian (Wolfcampian); North America.


Diagnosis.—Reticulate colonies with relatively wide, thick branches and relatively thin dissepiments. Autozooecia arran- ged in two rows on branches. Autozooecia triangular in mid- tangential section, triangular to pentagonal proximal to bifurcations. Narrow keel with single row of nodes.


Occurrence.—Lower Devonian–upper Permian; worldwide.


Remarks.—Spinofenestella differs from the genus Rectifenes- tella Morozova, 1974 by the triangular shape of the autozooecia in midtangential section.


Spinofenestella sp. Figures 8.7–8.9, 9.1–9.5; Table 9


Figure 8. (1, 2) Minilya sp.: (1) NMMNH P-79598, oblique tangential section showing autozooecial chambers and apertures and alternating keel nodes; (2) NMMNH P-79599, oblique tangential section showing autozooecial chambers, apertures (arrow = stellate structure), and alternating keel nodes. (3–6) Laxifenestella sp.: (3, 4, 6) NMMNH P-79604: (3) tangential section showing autozooecial chambers, apertures, and keel nodes (arrow); (4) tangential section showing autozooecial chambers with superior hemisepta (arrows) and apertures; (6) midtangential section showing autozooecial chambers and keel nodes (arrow); (5) NMMNH P-79607, midtangential section showing autozooecial chambers;. (7–9) Spinofenestella sp., NMMNH P-79581: (7, 8) tangential section showing autozooecial chambers, apertures, and keel nodes; (9) tangential section showing chambers, apertures, and keel nodes. Scale bars = 1mm (1–3, 5), 0.5mm (4, 6, 9), 2mm (7, 8).


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