Dictyomitra, Zittel, 1876

Kochhann, Karlos G. D., Baecker-Fauth, Simone & Fauth, Gerson, 2013, Late Maastrichtian Radiolaria from ODP Leg 165 - Site 999 B, Colombian Basin, Geodiversitas 35 (1), pp. 5-20 : 10

Dictyomitra sp. 2

( Fig. 4F )

FIGURED SPECIMEN. — ULVG-7324.

MATERIAL. — 23 specimens (recovered with the hydrogen peroxide method); two specimens (recovered with the acetic acid method).

DESCRIPTION

Multi-segmented form (six to eleven segments), with test elongated and conical shape. Well-developed and vertically aligned costae obscured on cephalis. Cephalis slightly acute apically. Between adjacent costae, a single parallel row of aligned sub-circular pores or sub-circular depressions is present. Deep and well-developed constrictions occur at joints between segments, formed possibly by one or two transverse pore rows, and are followed by the costae outline. Costae are normally obscured at strictures. One transverse depressed row is present on the central part of each abdominal and post-abdominal segment. Lateral outline of the test strongly lobulated at segmental division levels. Chambers gradually increasing in length and width distally. Distal margin ragged, having, or not, small costal projections.

REMARKS

Dictyomitra sp. 2 differs from both D. multicostata Zittel, 1876 and D. formosa Squinabol, 1904 by the transverse depression in the central part of each abdominal and post-abdominal segment. Likewise, D. formosa normally presents the first postabdominal segment inflated, producing a kind of ledge neck, and does not have constrictions at the apical (proximal) region. Dictyomitra multicostata has slighter constrictions. This species presents some similarities to Dictyomitra sp. 2, recorded by Aumond et al. (2009) from Maastrichtian strata of ODP Hole 1001B, but it has segments more angular in outline.

Figures

FIG. 4. — SEM images of Radiolaria recovered from the sample 999B/60/2W/70-74 cm: A, Archaeodictyomitra cf. A. squinaboli Pes- sagno,1976 (H2O2 method);B, Archaeodictyomitra cf. A. lamellicostata (Foreman, 1968) (H2O2 method); C, Archaeodictyomitra? sp. 1 (H2O2 method); D, Archaeodictyomitra? sp. 2 (H2O2 method); E, Dictyomitra sp. 1 (H2O2 method); F, Dictyomitra sp. 2 (H2O2 method); G, Mita regina? (Campbell & Clark, 1944) (CH3COOH method); H, Amphipyndax tylotus Foreman, 1978 (H2O2 method); I, Stichomitra asymbatos Foreman,1968 (H2O2 method);J, Stichomitra? sp.1 (H2O2 method); K, Stichomitra? sp. 2 (H2O2 method); L, Rhopalosyrin- gium magnificum Campbell & Clark,1944 (H2O2 method). The chemical compound after each species indicates the chemical method applied in the recovery of each figured specimen. Scale bars: 100 µm.