Stomatopora sp.

Hara, Urszula & Taylor, Paul D., 2009, Cyclostome bryozoans from the Kimmeridgian (Upper Jurassic) of Poland, Geodiversitas 31 (3), pp. 555-575 : 561-563

Stomatopora sp. ( Fig. 4 )

MATERIAL EXAMINED. — Skorków Lumachelle, Małogoszcz Quarry: NHM BZ 5518(2).

MEASUREMENTS. — Transverseaperturaldiameter = 0.15-0.18 mm; longitudinalaperturaldiameter = 0.24-

0.27 mm; frontal wall length = 0.96-1.0 mm; frontal wall width = 0.36-0.45 mm.

OCCURRENCE. — Lower Kimmeridgian, Małogoszcz Quarry, Holy Cross Mts, Poland.

DESCRIPTION

Colony encrusting with uniserial, often curved branches bifurcating dichotomously, initially at about 180°, subsequently at lower angles; first internode contains ancestrula plus one budded zooid, later internodes 1-4 zooids. Ancestrula large, 0.78 mmlong by 0.30 mm wide, protoecium 0.36 mm wide; details of pseudopores and aperture not visible.

Zooids monomorphic, large, elongate, subcylindrical. Apertures longitudinally elongate ( Fig. 4G, H ). Pseudopores apparently subcircular.

REMARKS

Two colonies of this species encrust the dorsal valve of a brachiopod. Both colonies are small in size, the largestcontainingonly 11 zooids, andneither arewell preserved.Nevertheless, theirzooidsareclearlysignificantlylarger thanthose of S. dichotomoides described above.Thatthisdifferenceinzooidsizeisnotentirely ecophenotypic is shown by the presence of a colony of S. dichotomoides with smaller zooids on the same substrate as the two colonies of Stomatopora sp.

The available material of Stomatopora sp. is too sparse and poorly preserved to give a precise determination. Among named Jurassic species of Stomatopora , the species with the largest zooids is S. recurva Waagen, 1867 , recorded by Walter (1970) from the Upper Aalenian and Lower Bajocian of Germany, France and England. However, probable specimens of S. recurva from the Upper Bathonian or Lower Callovian of Poland ( Taylor 2008) have smaller zooids than the Lower Kimmeridgian species described here. For example, the protoecium in Balin material of putative S. recurva measures 0.25 mm wide (vs. 0.36 mm), and the ancestrula is 0.50 mmlong (vs. 0.78 mm).

Figures

FIG. 4. — Stomatopora sp.,NHM BZ 5518(2),Lower Kimmeridgian, Skorków Lumachelle,Małogoszcz Quarry,Holy Cross Mts,Poland: A, early astogeny with ancestrula at bottom right; B, autozooid. Scale bars: A, 1 mm; B, 500 μm.