Cretaceous sponges from the Campanian of Misburg and Höver |
Figure 1 - Polyopesia angustata. Teutonia Nord, Misburg. Figure 2 - Polyopesia angustata. Alemannia, Höver. Figure 3 - Polyopesia angustata. Teutonia Nord, Misburg. Figure 4 - Polyopesia angustata. Alemannia, Höver |
Synonyms:
Hexactinella angustata Schrammen 1912 The nomenclature of the genus Polyopesia is confused and its taxonomic position is subject to dispute. (See below.)
Occurence: Alemannia, Höver, Lower Campanian (senonensis zone). Rare. Teutonia, Misburg, Upper Campanian (spiniger zone). Rare.
Figure 1 shows the most complete specimen of Polyopesia angustata found to date. Figure 2 shows a top-section with a growth margin, and Figure 3 shows a well preserved lower section with root stubs. Considering all available material, typical individuals of Polyopesia angustata consist of a single tapering tube, some 200 to 300 mm tall and 20 to 40 mm wide, with a 6 to 10 mm thick wall. Senior individuals may develop a widened, trumpet-shaped top. The roots are conspicuosly strong and are constructed from dictyonal hexactines. Near-end cross sections of the roots reveal several (5 to 10) longitudinal channels up to 3 mm wide. The dermal surface consists of many irregularly disposed protruding wart-like (external) postica, each 1.5 to 2 mm wide and separated from its neighbors by about the same distance (Figures 1 to 3). Ostia are arranged in depressed positions around the postica and are thus invisible in unetched specimens. The gastral (atrial) side shows (internal) postica with quite large (4 to 5 mm) oval apertures, which are vaguely arranged in quincunx (Figure 4). |
Figure 5 - Polyopesia angustata. Alemannia, Höver Figure 6 - Polyopesia angustata. Alemannia, Höver Figure 7 - Polyopesia angustata. Alemannia, Höver Figure 8 - Polyopesia angustata. Alemannia, Höver Figure 9 - Polyopesia angustata. Alemannia, Höver |
Etched samples of Polyopesia angustata (Figures 5 and 6) reveal the ostia in the depressed positions between the wart-like postica. Figure 7 is a photomicrograph of an etched sample, showing two wart-like raised postica with constricted apertures in the middle of several ostia with variablly sized apertures. Figure 8 is a detail of Figure 7. Note the silica mantled hexactins which constitute a dermal cortex. Figure 9 (photomicrograph, etched sample) is an internal view of the dermal side, showing dyctional framework. Free thorn-like hexactine arms make up the inside of the aporhyses leading to the external postica. Note the reinforced dermal hexactins which also form the apertures if the ostia. |
Figure 10 - Polyopesia laevis, Alemannia, Höver Figure 11 - Polyopesia laevis, (etched specimen). Figure 12 - Polyopesia laevis, (etched specimen). Figure 13 - Polyopesia laevis. Detail of previous figure. Figure 14 - Polyopesia laevis, (etched specimen). Figure 15 - Polyopesia laevis, (etched specimen). Figure 16 - Polyopesia laevis, (etched specimen). |
Etched specimen of Polyopesia laevis (Figure 10), showing macroscopic structure of the dermal side, with larger ostia in depressed cavities between ridges, and smaller postica astride the ridges. The disposition of the dermal ostia appears more or less random. In other cases, a weak in quincunx arrangement of the dermal ostia may be recognizable. Figures 11 through 13 give an impression of the internal wall structure (dermal layer) and the schizorhysal channelization. Figures 14 and 15 show aspects of the gastral (atrial) layer of the "double wall". In figure 15, note chambers adjacent to postica in longitudinal (north-south) direction, which are part of the schizorhysal channelsystem. Figure 16 is a detailed view at the dictyonal framework. Note predominantly four-sided meshes. The nodes of the hexactins are not swollen in this case. However, in other samples more or less distinctly swollen nodes do occur. This feature therefore seems indistinctive for the species. |
For reasons of consistency, the author adheres to the taxonomic classification by Reid (2004) for the moment and uses the designation "Polyopesia" rather than "Hexactinella".
Schrammen (1902) errected the new genus Polyopesia, with the two new species Polyopesia angustata (Plate II, Fig 1) and Polyopesia radiciformis (Plate III, Fig. 4). At that time, he tentatively placed Polyopesia into the family Craticularidae RAUFF 1893.
In his later work, Schrammen (1912) separated the tube- to funnel-shaped Polyopesia-species from the branched to anastomosed tubular Tretodyctium-species, moved the former into the family Tretocalycidae SCHULZE 1904 (syn. Tretodictyidae SCHULZE 1886) and the emended genus Hexactinella CARTER and consequently renamed his former Polyopesia into Hexactinella.
At the same time, Schrammen (1912) described "Hexactinella laevis" as a new species and synonymized Polyopesia radiciformis with Polyopesia angustata.
Reid (2004), without provision of arguments, considered Schrammen's (1912) identification of Polyopesia with Carter's Hexactinella to be wrong and transferred Polyopesia to the family Cribrospongiidae ROEMER 1864.
Author's comment:
The evidence provided here by the present author suggests that Schrammen's (1912) taxonomic classification was fully justified, and that the name Hexactinella should be used instead of Polyopesia. Polyopesia angustata and Polyopesia laevis should be regarded members of the family Tretodictyidae SCHULZE 1886.