Original scientific paper

Lower and Middle Liassic Calcareous Algae (Dasycladales) from Mt. Velebit (Croatia) and Mt. Trnovski Gozd (Slovenia) with Particular Reference to the Genus Palaeodasycladus (PIA, 1920) 1927 and Its Species

B. Sokač

Abstract

Based on the characteristics of individual species, the generic characteristics of Palaeodasycladus have been determined and enlarged. P. mediterraneus (PIA, 1920) 1927 comprises a broad array of varieties that have been taxonomically distinguished on the basis of the variable shape of primary and secondary branches and the way in which the secondaries emerge. The following varieties are represented: P. mediterraneus (PIA, 1920) 1927 var. mediterraneus, P. mediterraneus var. heraki (SOKAC & NIKLER, 1966) n. comb., P. mediterraneus var. illyricus (SOKAC & NIKLER, 1966) n. comb., P. mediterraneus var. gracilis (CROS & LEMOINE, 1967 ex GRANIER & DELOFFRE, 1993) n. stat., P. mediterraneus var. elongatulus PRATURLON, 1966, and P. mediterraneus var. calciticus n. var., and are characterised by specific skeletal form and easily recognisable calcification pattern. Also, the generic assignment of P. barrabei LEBOUCHÉ & LEMOINE, 1963 ex GRANIER & DELOFFRE, 1993 has been confirmed, in spite of its recent transferral to Eodasycladus by BARATTOLO et al. (1994). The following new species have been described: Palaeodasycladus alanensis n. sp., characterised by broadened, bowl-shaped or bushy swollen primary branches; P. multiporus n. sp., characterised by numerous higher-order branches on each primary branch; P. benceki n. sp., with very large primary branches with extremely variable distal ends; and P. asteriscus n. sp., with loosely spaced whorls and variously directed secondary branches, often growing in opposite directions from the same primary branch. Lower Liassic species, previously ascribed to Fanesella, F. dolomitica and F. anae, have also been assigned to Palaeodasycladus with enlarged generic characteristics and are named, consequently, Palaeodasycladus dolomiticus (CROS & LEMOINE, 1966) n. comb. and P. anae (SOKAC, 1988) n. comb., respectively. Fanesella sokaci BARATTOLO & BIGOZZI, 1996 is considered to be a younger synonym of P. dolomiticus. Phylogenetic relationships between various taxa have also been considered and a phyletic lineage P. barrabei - P. alanensis - P. benceki has been shown to exist.

As regards the relationship between Palaeodasycladus and Eodasycladus, the latter has been shown to have evolved directly from P. barrabei by enlarged and more pronounced bubble-shaped swelling of one of the secondary branches, which thus becomes a “sporangia-bearing” organ. Also, a new species tentatively assigned to the genus Selliporella, Selliporella? problematica n. sp., has been described. From its morphological characteristics it represents an intermediate form, and a phylogenetic link between Liassic Palaeodasycladus and Middle Jurassic Selliporella. Finally, a new species, Humiella japodica n. sp. has been described, thereby enlarging the stratigraphic range of the genus Humiella into the Lower Liassic.

Keywords

Calcareous algae (Dasycladales); Lower-Middle Liassic; Croatia; Slovenia

Hrčak ID:

3853

URI

https://hrcak.srce.hr/3853

Publication date:

28.12.2001.

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