Geology Reference
In-Depth Information
10.2.1.3 Solenoporacean Red Algae
used as generic characteristics. The traditional species
differentiation only on the basis of cell dimensions is
highly artificial. The group has to be restudied. Vachard
et al. (1989) drew attention to the possibility that many
solenoporacean 'species' correspond to diagenetic
stages rather than to well-founded taxonomic units.
Definition, calcification and morphology:
Soleno-
poraceans are extinct encrusting calcareous algae that
developed nodular and branched growth habits rang-
ing in size from several millimeters to a few centime-
ters. The thalli consist of closely packed threads of ver-
tically divergent calcified cells, which appear circular
or polygonal in cross-sections. Solenoporaceans are
commonly preserved as Low-Mg calcite, but rare
records and the strong and patchy recrystallization in-
dicate a primary aragonitic composition. In contrast to
coralline algae no distinct differentiation of the cellu-
lar tissue exists. Undisputable reproductive structures
are not known. Cell diameter and length is commonly
larger than those of corallinaceans (about 10 to 100
m).
Taxonomic
differentiation
is based on zonation patterns,
the arrangement, shape and size of cells, partitions
within the filaments and walls and cell connections.
The presence/absence and regular or irregular spacing
of horizontal partitions within the filaments have been
Systematic position:
The Solenoporaceae are now
regarded as a subgroup of the red algal group Florideae
because of the existence of pit-like connections between
the cells (Moussavian 1989). The group has been con-
sidered to represent possible ancestral forms of the
Corallinaceae, but still distinct evidence for this inter-
pretation is missing.
Distribution:
Cambrian to Miocene. Solenopora-
ceans are constituents of Paleozoic and Mesozoic sub-
tidal open-marine shelf carbonates and reef limestones.
In some Silurian, Permian and Late Cretaceous reefs
the algae are concentrated near the open-marine reef
margin. They are common in Middle and Late Trias-
Plate 55 Solenoporacean Red Algae
Solenoporacean algae, known from the Cambrian to the Late Tertiary, are common thin-section fossils in Paleo-
zoic and Mesozoic platform and reef carbonates. The encrusting calcareous algae had nodular and branched
growth habits and range in size from several millimeters to a few centimeters. Solenoporaceans have been
regarded as possible ancestors of corallinacean red algae. Longitudinal sections show radially or vertically di-
vergent calcified filaments appearing as long 'tubes' (-> 3) or superposed cells within the filaments (-> 5). Cell
diameter (about 10-100
m) is larger than that of most corallinacean red algae. Taxonomic differentiation is
based on zonation patterns, the arrangement, shape and size of cells (-> 3, 5, 8), partitions (-> 4, 5) within the
filaments and walls and cell connections. The group has to be restudied regarding additional morphological
criteria (-> 8).
1 Solenporacean floatstone. The nodular algal thalli are bored and marginally micritized. Solenoporacean algae, often
associated with porostromate algae, are common constituents of small-scaled Frasnian and Famennian buildups. Latest
Devonian (Strunian): Dubic-Debnik near Krakow, southern Poland.
2
Solenopora.
Nodular thalli in life positon with distinct growth zonation. They occur together with dendroid corals (not
shown) and form a reef framework with sizes larger than 1 square meter. Late Triassic: Jabal Kawr, Oman.
3
Solenopora cassiana
Flügel. Longitudinal (LS) and cross-section (CS). Note distinct filaments exhibiting pearl-shaped
outlines (arrow) that correspond to lateral connections. Reef facies. Late Triassic (Cassian Formation, Carnian): Seeland
Alm near Cortina d'Ampezzo, Southern Alps, Italy.
4
Parachaetetes johnsoni
Maslov. Note different preservation obscuring the algal structure in the lower part of the thallus.
Same locality as -> 1
5
Parachaetetes johnsoni
Maslov. Horizontal partitions are situated at the same level between tubes, and separate the long
cells. The well-preserved alga is encrusted by foraminifera. Same locality as -> 1.
6 Transported solenoporacean red algae exhibiting the common preservation feature. Recrystallization of the originally
aragonitic thalli has obliterated the algal structure, which is only recognizable in traces. In contrast, micro- and macrobor-
ings (black and white arrows) are well preserved because of early infilling with calcite. Early Permian: Teufelsschlucht,
Karawanken Mountains, Slovenia.
7
Solenopora
. Longitudinal section. Note growth zonation and microborings (arrows). Early Cretaceous: Subsurface, United
Arabian Emirates.
8
Parachaetetes asvapatii
Pia
.
The filaments are differentiated into 'long' and 'short' cells (occurring in the dark zones)
similar to cell differentiation in modern floridean red algae. The cosmopolitan species is known from the Albian to the
Paleocene. Early Tertiary: Italy.
-> 2: Weidlich et al. 1993
