Microporella bifoliata Ulrich & Bassler, 1904

Martino, Emanuela Di, Taylor, Paul D. & Gordon, Dennis P., 2020, Erect bifoliate species of Microporella (Bryozoa, Cheilostomata), fossil and modern, European Journal of Taxonomy 678, pp. 1-31 : 3-5

Microporella bifoliata Ulrich & Bassler, 1904

Fig. 1 ; Table 1

Microporella ? bifoliata Ulrich & Bassler, 1904: 417 , pl. 103, figs 6–8.

Microporella ? bifoliata – Canu & Bassler 1923: 121, pl. 20, figs 7–11.

Material examined

Lectotype (designated here)

USA • Syntype of Microporella bifoliata Ulrich & Bassler, 1904 ; Maryland, Cordova; Miocene ; Choptank Formation ; USNM 68592A ( Fig. 1 A–B).

Paralectotype (designated here)

USA • Syntype of Microporella bifoliata Ulrich & Bassler, 1904 ; Maryland, Cordova; Miocene ; Choptank Formation ; USNM 68592B ( Fig. 1 C–D) .

Other material

USA • 4 specimens, syntypes of Microporella bifoliata Ulrich & Bassler, 1904 ; Maryland, Cordova; Miocene; Choptank Formation ; USNM 68592C to 68592F .

Description

COLONY. Erect with bifoliate fronds up to several cm wide, curved; colony base and interzooidal communication not observed.

AUTOZOOIDS. Distinct, separated by narrow grooVes, rectangular, longer than wide (mean L/W = 1.76). Frontal shield flat; marginal areolae typically numbering about 16 (12–18), Variable in size (15–40 µm), funnel-shaped, sometimes subdivided internally; reduced number of non-marginal pseudopores, placed more centrally on the frontal shield, irregularly spaced.

PRIMARY ORIfICE. Terminal, semielliptical, widest medially, hingeline slightly concave, without teeth or condyles; oral spines lacking; no peristome.

ASCOPORE fIELD. A narrow, raised area of gymnocystal calcification beneath leVel of adjacent frontal shield but at approximately same leVel as orifice, located Very close to its hingeline; elliptical, ca 35 × 50 µm, distal margin with projecting, semielliptical tongue leaVing a crescent-shaped opening, ca 10 × 30 µm, with radial spines.

AVICULARIUM. Single, located at the same level of ascopore, oriented laterally; crossbar complete; opesia semielliptical; rostrum subtriangular, the distal end a little rounded, not channelled.

OVICELL. Prominent, circular in outline, not personate and not obscuring orifice; calcification similar to frontal shield; pseudopores variable in number, scattered over entire surface, variably spaced.

Remarks

This extinct species was described from the Miocene (Choptank Formation 12.6–14.4 Ma; Andrews 1988) of Maryland ( Fig. 1 ).

The form of the mandible is not known in this fossil species, but the fact that the avicularia have closed distal ends without channels may suggest that mandibles were not setose and had a shape identical to that of the rostrum.

Figures

Fig. 1. Microporella bifoliata Ulrich & Bassler, 1904, Miocene, Choptank Formation, Maryland, USA. A–B. Lectotype USNM 68592A. A. General view of the branch fragment. B. Group of zooids, mostly ovicellate. C–D. Paralectotype USNM 68592B. C. Group of autozooids. D. Close-up of an autozooid. Scale bars: A = 1 mm; B–C = 200 µm; D = 100 µm.