Geology Reference
In-Depth Information
Fig. 10.15.
Position of the reproductive organs in dasyclad algae. After Berger and Kaever (1992).
Plate 59 Dasyclad Green Algae: Taxonomic Criteria
Main criteria in the differentiation of dasyclads are the growth form and shape of the thallus and the central stem,
the arrangement, shape and the number of branching of laterals, and the position of reproductive organs (see
Figs. 10.14 and 10.15). The plate shows examples of some of the diagnostic morphological criteria.
1
Eovelebitella occitanica
Vachard. Cross section (CS), longitudinal (LS) and tangential sections (TS). Rod-shaped, annu-
late thallus. Primary branches (white arrows) are arranged in clusters of regular whorls (metaspondyl), forming a succes-
sion of subspherical articles, black arrows). The laterals increase in size towards the periphery (phloiophore type). The
genus is locally abundant in Tournaisian and Viséan shelf carbonates. Early Carboniferous (Viséan). Southern Spain.
2
Diplopora phanerospora
Pia
.
Cross section and longitudinal section. Club-shaped articulated thallus. Primary poikilophore
and vesicular branches of one single order are grouped into tufts (metaspondyl). Calcified reproductive organs (cysts,
arrow) are situated within the main axis (endospore type). Late Triassic (Zlambach beds, Rhaetian): Bavarian Alps,
Germany.
3
Neoteutloporella socialis
(Praturlon). Longitudinal section of densely spaced autochthonous dasycladacean thalli that
form algal meadows and biostromes in outer platform settings of the Alpine-Mediterranean Tethys (Dragastan et al. 1987;
Bodeur 1995). Cylindrical articulated thallus with short primary and long secondary branches (black arrows) arranged
oblique to the main axis (white arrow) in close-set euspondyl whorls (W). Laterals become thinner at their distal ends
(trichophore type). Stem cell with swellings and narrowings (annulation). The species is commonly associated with corals
and 'hydrozoans' (e.g.
Ellipsactinia
, -> Pl. 81/5). Species range Oxfordian to Tithonian. Late Jurassic (Tithonian): Abruzzi
National Park, central Apennines, Italy.
4
Mizzia velebitana
Schubert. Oblique and tangential sections (TS). The thallus consists of spherical articulated segments.
The central stem is barrel-shaped and has constrictions at the joints between segments (annulation). Only primary branches,
arranged in concentric rows. Branches enlarge in diameter near the exterior, producing a honeycomb pattern on the
surface. Late Permian: Bergama, western Turkey.
5
Mizzia
wackestone. Isolated spherical segments. Note the difference in size, indicating transport of the algal fragments.
Late Permian: Taurus Mountain Range, Turkey.
6
Anthracoporella spectabilis
Pia. Longitudinal (LS), cross section (CS) and tangential section (TS). Rod-shaped, tube-like
thalli. Closely spaced irregularly arranged (aspondyle) primary laterals. The thalli of this species are conspicuously large
and are several centimeters long. Late Carboniferous (Lower Pseudoschwagerina beds, Gzhelian): Hüttenkofel, Carnic
Alps, Austria.
7
Clypeina jurassica
Favre. Star-shaped cross sections (CS) and chain-like oblique sections (OS) of isolated whorls. The
cylindrical thallus consists of basket-shaped superposed whorls. The whorls are composed of jointed fertile branches
bearing sporangia that almost touch each other, and broadening toward the periphery (arrow). Packstones and wack-
estones with mass accumulations of
Clypeina jurassica
are diagnostic of lagoonal inner platform environments with
restricted circulation and sometimes also reduced marine salinity (-> Pl. 28/2, Pl. 62/5-6, Pl. 134/5). The species is widely
distributed from the Late Kimmeridgian to the base of the Late Berriasian. Late Jurassic: Vrhnica, Slovenia.
