Nicholsonella spinigera, Ernst & Carrera, 2022

Ernst, Andrej & Carrera, Marcelo G., 2022, A cool-water bryozoan association from the La Pola Formation (Sandbian, Ordovician) of Argentine Precordillera, Geodiversitas 44 (20), pp. 563-601 : 582-586

Nicholsonella spinigera n. sp.

( Figs 12G, H ; 13 A-F; Appendix 1)

urn:lsid:zoobank.org:act:29ECE5F7-47D8-4DF3-8375-4BFEF20F02DF

HOLOTYPE. — CEGH-UNC 27528 b, c.

PARATYPES. — CEGH-UNC 27507 a, b, CEGH-UNC 27512 a, b, CEGH-UNC 27522 a, b, CEGH-UNC 27530 e, CEGH-UNC 27533 d, CEGH-UNC 27538 a, c, CEGH-UNC 27539 g.

TYPE LOCALITY. — La Pola creek section near Albardon village, San Juan Province, Argentine Precordillera, western Argentina.

TYPE HORIZON. — La Pola Formation, Upper Ordovician, Sandbian.

DIAGNOSIS. — Ramose colonies with distinct exozones; secondary overgrowths occurring; autozooecial apertures angular with rounded corners; basal diaphragms abundant both in endozone and exozone, straight, or inclined; mesozooecia few, containing densely spaced thick diaphragms; acanthostyles large, 4-8 surrounding each autozooecial aperture, originating in endozone, having wide hyaline cores and narrow laminated sheaths; exozonal autozooecial walls thickly laminated, merged, showing reversal U-shaped lamination, without cingulum; maculae lacking.

ETYMOLOGY. — The species name refers to large and abundant acanthostyles of the new species (from Latin “ spiniger ” – spinose).

DESCRIPTION

Branched colony with secondary overgrowths, 3.5-11.0 mm in diameter, with 0.45-1.30 mm wide exozones. Secondary overgrowths 1.05-2.00 mm thick.Autozooecial apertures angular with rounded corners. Basal diaphragms abundant both in endozone and exozone, straight, or inclined. Mesozooecia few, containing densely spaced thick diaphragms. Acanthostyles large, abundant, 4-8 surrounding each autozooecial aperture, originating in endozone, having wide hyaline cores and narrow laminated sheaths, often indenting autozooecia and mesozooecia. Autozooecial walls granular, 0.005 -0.010 mm thick, irregularly undulating in endozones; thickly laminated, merged, showing reversal U-shaped lamination, without cingulum, 0.05-0.09 mm thick in exozones. Maculae not observed.

COMPARISON

Nicholsonella spinigera n. sp. is similar to N. irregularis Loeblich, 1942 from the Bromide Formation (Sandbian) of Oklahoma ( United States), but differs from it in more abundant acanthostyles (4-8 acanthostyles per autozooecial aperture vs 5-6 in N. irregularis ) and in more abundant autozooecial diaphragms. Nicholsonella spinigera n. sp. differs from N. pulchra Ulrich, 1893 from the Upper Ordovician of United States in less abundant mesozooecia.

Figures

FIG. 12. — A-F. Argentinopora robusta n. gen., n. sp.: A, B, longitudinal thin section showing autozooecial chambers with a cystiphragm, mesozooecia,acanthostyles, holotype CEGH-UNC 27511 a; C, tangential thin section showing autozooecial apertures, mesozooecia, and acanthostyles, holotype CEGH-UNC 27511 d; D, branch transverse section, paratype CEGH-UNC 27514 b; E, F, tangential thin section showing autozooecial apertures, mesozooecia, and acanthostyles, paratype CEGH-UNC 27514 c; G, H, Nicholsonella spinigera n. sp., branch longitudinal section showing autozooecial chambers with diaphragms, holotype CEGH-UNC 27528 c. Scale bars: A, D, G, 1 mm; B, F, 0.2 mm; C, E, H, 0.5 mm.

FIG. 13. — A-F, Nicholsonella spinigera n. sp.: A, B, tangential thin section showing autozooecial apertures, mesozooecia, and acanthostyles, holotype CEGH- UNC 27528 c; C, longitudinal thin section showing autozooecial chambers with diaphragms, holotype CEGH-UNC 27528 b; D, E, branch transverse thin section showing autozooecial chambers with diaphragms and mesozooecia, paratype CEGH-UNC 27538 a; F, branch transverse thin section showing autozooecial chambers and acanthostyles in endozone, paratype CEGH-UNC 27538 a; G-I. Arthroclema sp. A: G, H, branch transverse thin section showing autozooecial chambers, CEGH-UNC 27520 d; I, branch oblique thin section, CEGH-UNC 27529 b. Scale bars: A, E, I, 0.5 mm; B, C, F, G, 0.2 mm; D, 1 mm; H, 0.1 mm.