Bakalovaella xizangensis ( Mu, 1986 ) Sun & Schlagintweit, 2025

Sun, Qi, Schlagintweit, Felix & Li, Xianghui, 2025, New records of Dasycladales (green algae) from the Aptian-Albian Langshan Formation of Tibet, Comptes Rendus Palevol 24 (20), pp. 381-395 : 390-391

Bakalovaella xizangensis ( Mu, 1986) , comb. nov.

( Fig. 9 A-E, H)

Heteroporella xizangensis Mu , Bulletin of Nanjing Institute of Geology and Paleontology, Academia Sinica 10: 97, pl. 4, figs 1, 4-6 ( Mu 1986).

STRATIGRAPHY. — Mu (1986) reported Heteroporella xizangensis from the northern slope of Langshan Mountain in the Duoba District, Baingoin County. The type-level is indicated as belonging to the lower part of the Langshan Formation containing Morelletpora turgida (Radoičić) and Palorbitolina lenticularis (Blumenbach) indicating an early Aptian age.

DESCRIPTION

The alga has a cylindrical thallus with a main axis that corresponds to about 1/3 of the total diameter ( Fig. 9H). Sterile laterals and fertile whorls are arranged perpendicularly towards the axis in an alternating manner. In the last third (towards the algal surface), the fertile ampullae are touching each other (vertically and horizontally) appearing as a contiguous undulating micritic bands between the levels of sterile laterals ( Fig. 9C). The fertile ampullae are inflated with a flattened distal end thereby occupying the space between the sterile laterals almost completely.. The inner surface of the main axis is smooth.

REMARKS

Heteroporella xizangensis Mu was originally described as belonging to Heteroporella Praturlon, 1967 . Mu (1986) designated one holotype (PB 10994, pl. 4 [wrongly indicated as pl. VI = 6], fig. 1) and two paratypes (PB 10995, pl. 4, fig. 4 and PB 10696, pl. 4, fig. 5). Although validly described, it has neither been included in the critical literature inventory of species ( Granier & Deloffre 1993; Bucur 1999) nor the taxonomic revision of the genus Heteroporella and its “species” ( Granier et al. 1994). This led to the reduction of the inventory of the genus Heteroporella to its type-species H. lepina Praturlon , while all other species previously described as belonging to it were assigned to other genera. Heteroporella xizangensis Mu is herewith assigned to the genus Bakalovaella Bucur, 1993 . This genus is characterized by thalli bearing alternating sterile and fertile whorls that are connected to the former that exhibit a distal widening to form a cortex (see also Granier & Bucur 2019). Bakalovaella xizangensis has been observed only in the Mendang section (upper Aptian-middle Albian). COMPARISONS

Bakalovaella elitzae (Bakalova) (Barremian-Aptian of Bulgaria), another species of the genus that may be associated to B. xizangensis , is much smaller and displays almost spherical fertile ampullae ( Fig. 9I, J). Bakalovaella benizarensis (Fourcade et al. ex Jaffrezo in Bassoullet et al. 1978 (Barremian of Spain) represents a small-sized species (mean D: 0.60 mm to 0.85 mm) with six subspherical ampullae per vertical and a reduced vertical spacing (h: 0.13-0.18). Bakalovaella deloffrei Granier & Bucur, 2019 (Hauterivian of western France) represents another small representative of the genus (mean D: c. 0.70 mm) displaying a subcylindrical main axis bearing deeply imbricated verticils of 5 to 8 laterals each. Bakalovaella filipovici ( Radoičić, 2006) (Cenomanian-Turonian of Kosovo) represents a species with a comparably narrow main axis (d: 0.075 -0.177 mm) and subspherical fertile ampullae.