Arouxina pluricellata

Hussain, Rowshi, Rogers, Steven L. & Blackburn, Joel A., 2022, Ovummuridae (calcareous microfossils) from the Much Wenlock Limestone Formation, Shropshire, UK, Palaeontologia Electronica (a 27) 25 (2), pp. 1-24 : 10

Arouxina pluricellata

Munnecke, Servais, and Vachard, 2000

Figure 5 A-F

Derivation of name. Latin, pluri -, several; cella, small chamber.

Material. 10 specimens

Diagnosis. Test composed of two initial chambers separated by a pseudo-septum and a relatively small to medium number of hemispherical additional chambers. Each chamber presents an apical cylindrical non-protuberant aperture. Wall is calcitic and lamellar typical of the Ovummuridae .

Description. An Ovummuridae characterised by two symmetrical or asymmetrical chambers separated by a septum like-structure. Initial chambers can be equal in size like Ovummurus or bilocular like Minourella . The larger chamber is globular and oval shaped with the long axis parallel to the septum. The small chamber is globular and oval/elongated-oval shaped similar to the dorsal chamber. The aperture within the dorsal chamber is not always present. The initial chambers are surrounded by free and disjointed hemispherical smaller chambers that occasionally build upon each other.

Dimensions. Overall test height of 48–37 μm and an overall test width of 47–137 μm long. Large dorsal chamber height of 14–75 μm and a diameter of 18–67 μm with a surrounding wall thickness of 4– 29 μm. The smaller ventral chamber has a height of 3–24 μm and a width of 10–48 μm and the thickness of the wall surrounding the chamber is 0.9–13 μm thick. The septum thickness is 2–31 μm with an aperture ranging from 1–7 μm. The hemispherical chambers are approximately 13–25 μm in diameter and 6–13 μm height, the thickness of the surrounding wall measures between 4–10 μm.

Remarks. Various specimens observed here have fewer than 14 chambers as described by Munnecke et al. (2000). Here, we observe between 2-6 chambers. Munnecke et al. (2000) describe Arouxina pluricellata to resemble Ovummurus , however, we note morphologies that resemble Minourella gotlandica . The chambers are sometimes bulbous rather than hemi-spherical, and specimens that exhibit these bulbous growths tend to have several walls. Munnecke et al. (2000) suggest measurements are similar to those of Ovummurus and Minourella , noting overall chamber lengths of 80– 100 μm and total widths of 50–80 μm. It is noted that the Wenlock Edge specimens have longer lengths and width measurements exceeding the 100 μm in length and 80 μm in width that was originally observed. Comparison of the hemispherical chambers is not possible as no measurements were provided by Munnecke et al. (2000).

Stratigraphical range. Lower Silurian (Homerian)

Figures

FIGURE 5. Photomicrographs of Arouxina pluricellata (A-F) and Samtlebenella circumcamerata (G-H) within the MWL Fm., these specimens are from Longville Stanway Track (A), Moorwood Quarry (B, C, E and H), Harton Hollow (D and G) and Strefford Quarry (H). (A) = Sectional cut through A. pluricellata highlighting the multiple hemispherical chambers (HC) surrounding the globular dorsal chamber (DC) and ventral chamber (VC). HC can form concentrically. Occasional apical apertures (ap) are observed within the DC.The bulbous growth are associated with several walls. (B) = Thickened A. pluricellata specimen with six HC surrounding the central DC and VC. Note the presence of pyrite within a few of the HC. Matrix comprised solely of sparite. (C) = An elongate A. pluricellata test with three HC. (D) = Specimen of A. pluricellata highlighting the disjointed nature of the surrounding HC. (E) = A. pluricellata with a single HC chamber but exhibits an ap within both VC and DC. (F) = A. pluricellata specimen with thinner walled HC compared to the walls surrounding the DC and VC. (G) = S. circumcamerata resembling Darth Vader’s helmet. Presence of HC within the walls surrounding the DC. (H) = Thick walled specimen of S. circumcamerata with a partially preserved VC and two chambers (c) are visible within the walls surrounding the DC. Sparitic matrix = (sp). All scale bars equal 50 µm.