Rossella rotunda

Figure 1 - Rossella rotunda Teutonia North, Misburg.
Flattened curved tubular sponge with near circular cross
fracture (bottom left end). Basket formed essentially by
two diagonal sets of diactines.

Figure 2 - Rossella rotunda Teutonia North, Misburg.
Curved tubular basket with several protruding prostalia.

Figure 3 - Rossella rotunda Teutonia North, Misburg.
Vertically compressed specimen?

Synonyms:

none

Occurence:

Teutonia, Misburg, Upper Campanian (polyplocum zone). Rare.

Rossella rotunda has been reported from the Upper Cretaceous of Bornholm and Poland (Brückner, 2006; Swierczewska-Gladysz and Jurkowska, 2013). Several recently recovered samples from the Upper Campanian of the Teutonia quarry are considered identical with this material. Lyssacinosid sponges have a very poor preservation potential, hence fossil representatives are exceptional occurrences.

The three samples shown here (Figs. 1 to 3) are tubular fragments only, without indications of sieve plates or root tufts. All three samples show some degree of curvature which could imply a helical rather than straight tubular axis.

Figures 1 and 2 reveal a preferred orientation of large diactin spicules (principalia) in two diagonal directions. Longitudinal principalia are present but are less dominant. In addition, laterally protruding, large spicules (pleuralia) are visible, particularly in Figure 2.

Figure 4 - Rossella rotunda Pyritized bundles of diactines
and interspersed ill-defined comitala.

Figure 5 a, b - Rossella rotunda
Pyritic relics of parenchymal hexatines or pentactines.

Figure 6 - Rossella rotunda Various styles of fossil
spicule preservation.
1: cryptocrystalline silica
2: solid pyrite
3: microcrystalline pyrite scales

Figure 7 - Rossella rotunda . Principal spicules, side view
and cross section (center left), showing axial
canal. Cryptocrystalline silica.

Figure 8 - Rossella rotunda .
Principal spicule, replaced by quartz.

Figure 4 is a close-up view of the relictic skeleton. The larger pyritic streaks are the former principalia (see below). The fine interspersed needle like objects are pyritized comitalia.

Figures 5 a and b are attempts to capture the hexactin nature of the comitalia.

Figures 6 through 8 show different modes of preservation of the spicules. The spicules originally consisted of amorphous opaline silica. This was dehydrated and transformed into cryptocrystalline silica (Fig 6 number 1 and Fig. 7) and ultimately into quartz (Fig. 8)

However, in other cases the spicular silica was dissolved and the empty space was subsequently filled by either solid pyrite (Fig. 6) or lined by microcrystalline pyrite (actually visible in all Figures).