Geology Reference
In-Depth Information
Plate 79 Calcareous Sphinctozoan and Inozoan Sponges
Many coralline sponges are characterized by chambered, segmented skeletons (-> 4, 8), others are non-seg-
mented (-> 7). The former group has commonly been called Sphinctozoa, the latter Inozoa. These names are
now no longer used in a systematic context, but are still applied to separate morphological groups of polyphyl-
etic origin.
Sphinctozoans are differentiated according to external and internal morphological features. External features
include the shape (cylindrical, club-shaped, sheet-like or irregularly formed), the segmentation of the rigid skel-
eton, the pattern of chamber arrangement, and the inhalant and exhalant canal system of the outer wall. Internal
features seen in thin sections are internal segmentation (-> 2, 4), chamber shapes (-> 2, 4, 6, 8) and internal
fillings of the chambers (-> 1, 2, 3, 5) separating those parts of the skeleton which have been left behind by the
soft parts during growth, internal walls separating the chambers (-> 4, 8) and the central exhalant system (si-
phon, spongocoel). The latter corresponds to single or mul-
tiple openings appearing as defined central canal or canal
bundles (-> 3, 8).The schematic drawings on this page give
an idea of the complex internal morphology of a sphinctozoan
sponge (A), and demonstrate the possible relationship between
the calcareous skeleton (black) and the soft parts (stippled) in
a reconstruction (B). A - modified from Senowbari-Daryan
(1990), B - after Reitner (1992).
Most photographs display sphinctozoans (except -> 7,
which shows a section of an inozoan sponge). Sphinctozoan
sponges are abundant in Permian and Triassic reefs where
they formed rigid organic frameworks (-> 1, 5), sometimes
together with microbial crusts (-> 4).
1
Typical reef framework
formed by encrusting sphinctozoans. Cross section of
Jablonskya andrusovi
(Jablonsky) (J) and
Uvanella irregularis
Ott (U) growing on another sphinctozoan sponge. Both
sponges consist of microgranular High-Mg calcite skeleton (black in transmitted light). Note the
vesicular filling skeleton of
Jablonskya.
Late Triassic (Carnian): Dolomites, Southern Alps, Italy.
2
Morphological criteria of sphinctozoans.
Oblique longitudinal section of
Solenolmia manon
(Münster)
characterized by segments with a coarsely reticulate filling skeleton. Late Triassic (Carnian):
Molignon, Dolomites, Southern Alps, Italy.
3
Sphinctozoan morphology: Vesicocaulis reticuliformis
Jablonsky with central canal bundles (arrow)
connecting the catenulate segments and the reticular filling skeleton. Longitudinal section. Late
Triassic (Carnian): Huda Juzna, Slovenia. See schematic drawing on this page.
4
Sphinctozoan morphology:
Longitudinal section of
Colospongia dubia
(Laube). The moniliform
stem consists of stalked barrel-shaped segments with differentiated porate walls (PW) and vesiculae
(V) within the chambers. Note the different appearance of the originally aragonitic skeleton as com-
pared with originally Mg-calcitic skeletons (-> 1). Late Triassic (Carnian) patch reef: Huda Juzna,
Slovenia.
5
Sphinctozoan morphology:
Several densely spaced specimens of
Solenolmia manon
(Münster). The
segments contain a coarsely reticular filling skeleton. Internal walls of the segments are perforated.
Solenolmia
is a common sponge in Middle Triassic and Carnian reefs of the Alpine-Mediterranean
region. Late Triassic (Carnian): Huda Juzna, Slovenia.
6
Sphinctozoan morphology:
Alpinothalamia slovenica
(Senowbari-Daryan). Numerous glomerate
cyst-like chambers are arranged around the axial spongocoel. The wall consists of High-Mg calcite.
Late Triassic (Pantokrator limestone, Carnian): Hydra Island, Greece.
7
Inozoan sponge morphology:
Oblique section of
Sestrostomella robusta
Zittel. Similar to sphinctozoan sponges, inozoans
are characterized by the absence of segmentation. The sponge body is transected by axial canal bundles of the exhalant
system.
Sestrostomella
is known from Triassic and Late Jurassic-Early Cretaceous limestones. Late Triassic (Carnian):
Dolomites, Southern Alps, Italy.
8
Sphinctozoan and inozoan sponges:
Longitudinal section of the sphinctozoan
Discosiphonella lercarensis
(Senowbari-
Daryan and Di Stefano). The central cavity is surrounded by ringlike rows of hollow chambers. The internal walls are
perforated. The sphinctozoid sponge was competing for space with the inozoid sponge
Maeandrostia (
arrows). These
sponges occur in shelf habitats, not in reefs. Early Permian: Lercara, Sosio Valley, Western Sicily, Italy.
-> 2-8 and Figs. on this page: Courtesy of B. Senowbari-Daryan (Erlangen)
