Trocholina conica (Schlumberger, 1898)

Bucur, Ioan I. & Lazăr, Iuliana, 2023, Upper Jurassic To Lowermost Cretaceous Microfossils From The Hăghimaş Mountains (Eastern Carpathians, Romania), Acta Palaeontologica Romaniae 19 (1), pp. 13-26 : 16

Numerous specimens of Trocholina conica (Schlumberg- er) have been identified at the lower part of the succession. Originally attributed by Schlumberger (1989) to the genus Involutina , the species was later transferred to the genus Trocholina (e.g., Henson, 1947; Reichel, 1955) a genus recently emended by Rigaud et al. (2013) based on the presence of reduced lamellae on the spiral side and papillose lamellae on the umbilical side of the test. The papillae on the umbilical side, delimited by a marginal groove, are also visible on our material ( Fig. 6a, b, e, f ).

Saccocomid crinoid ossicles: The lower part of the succession is rich in fragments of Saccocoma sp. These are represented almost exclusively by sections of secondary brachial parts (secundibrachials). A detailed description and illustration of Saccocoma remains was made by Benzaggagh et al. (2015) based on numerous specimens collected from France, Tunisia and Morocco.

Agglutinated Annelid tubes: We identified Terebella lapilloides Münster in Goldfuss, 1833 in longitudinal ( Fig. 8l ), longitudinal-oblique ( Fig. 8k, n ) and transverse (fig. 8j, m) sections. Assigned to annelid worms that build agglutinated tubes, Terebella lapilloides has been described in detail by Kaya & Altiner (2014). Hughes (2018) reported the species from the Kimmeridgian- Tithonian of Saudi Arabia. The maximum length observed in the specimens from Hăghimaş is 3.6 mm; the external diameter ranges between 0.63-0.73 mm and the internal one between 0.2-0.46 mm; the thickness of the wall is 0.15-0.16 mm.

Organisms with an uncertain systematic position: Crescentiella morronensis (Crescenti, 1962) ( Fig.8 a-i) is frequently associated with Saccocoma and Terebella in the lower part of the succession. Originally (Crescenti, 1962) assigned to the genus Tubiphytes , this microorganism was reassigned to the new genus Crescentiella by Senowbari-Daryan et al. (2008) and considered a symbiosis between a nodophthalmiid foraminifer and cyanobacteria. The cyanobacterial “cortex” has variable thickness (around 0.5 mm in Hăghimaş specimens) and a laminar structure within which tubular formations are sometimes distinguished ( Fig. 8c ), an additional argument of the cyanobacterial nature of the “cortex”.

Muranella parvissima ( Dragastan, 1966) ( Fig. 9i ): Initially assigned to the genus Clypeina ( Dragastan, 1966) , these remains were reassigned to the genus Didemoides (Misik & Borza, 1978) , the genus Enigma ( Eliašová, 1981) and later to the genus Muranella ( Eliašová, 1985) . They are small spherical or ovoid corpuscles, often grouped in clusters, made up of calcite prisms developed around a micritic center with an irregular outline. Their nature remains uncertain.

Microbial crusts: the studied limestones are rich in microbial structures ( Lazăr et al., 2011). They sometimes develop in the form of laminated stromatolite crusts ( Fig. 9a ) or microbial-ferruginous crusts (9h).

Planktonic microorganisms: in thin section FO4 we identified rare calpionellids, some of which certainly belong to the species Calpionella alpina Lorenz ( Fig. 9g ), representing small globular forms characteristic of the Upper Tithonian.

Figures

Fig. 6 Foraminifera. a-c, e, f Trocholina conica (Schlumberger). Subaxial (a-c), and oblique (e, f) sections; a – thin section FO2-A1(3); b – thin section FO1-C(1); c – thin section FO2-A1(2); e – thin section FO1-F2; f – thin section FO2-A1. d?Saracenaria sp., thin section FO2-B8. g Mohlerina basiliensis (Mohler), oblique-tangential section; thin section FO-10A. h, i Coscinoconus alpinus Leupold in Leupold & Bigler, subaxial sections; thin section FO-10A. j, l-o Epistominidae. j – thin section FO2-B5; l – thin section FO1-A1; m – thin section FO1-F(1); n – thin section FO1-D; o – thin section FO2-B3. k Longitudinal section through a nodosariid foraminifera; thin section FO3. p, q Spirillina spp. Axial sections. p – thin section FO1-A0(1); q – thin section FO2-B4. r, s, v Lenticulina spp. Subequatorial (r, v) and subaxial (s) sections; r – thin section FO2-B10; s – thin sections FO2-A1; v – thin section FO1-C1. t, u Encrusting foraminifera. t – encrusting agglutinated foraminifera, thin section FO1-E; u – Bullopora sp., thin section FO1-F92).

Fig. 8 Incertae sedis microorganisms and agglutinated worm tubes. a-i Crescentiella morronensis (Crescenti) in longitudinal-oblique (a, c, i), oblique (b, d, e, f), and transverse (e, h) sections; a, c – thin section FO1-B (c = closeup view of the middle part in a); b – thin section FO2-B8; d – thin section FO2-A1(3); e, f – thin section FO1-E (f = close-up view of the middle part in e). g – thin section FO1-A1; h – thin section FO2-A1; i – thin section FO1- F2(2). j-n Terebella lapilloides (Münster). Longitudinal (l), longitudinal-oblique (k, n), and transverse (j, m) sections; j – thin section FO2-B10; k – thin section FO1-B; l, m – thin sections FO1-A0; n – thin section FO2-A1.

Fig. 9 Microbial crusts and sponges. a Laminated, fine-peloidal stromatolitic structure; thin section FO1-F2(2). b Lithistid(?) sponge; thin section FO2-B6(2). c-e Microbial crust around a sediment fragment containing different bioclasts showing encrusting Koskinobulina socialis Cherchi & Schroeder (white arrows in d and e = close-up views of c). The arrow in c points to a saccdocomid ossicle); thin section F1-G. f Rivularia/Cayeuxia type cyanobacteria; thin section FO1-10B. g Calpionella alpina Lorenz; thin section FO4. h Microbial-ferruginous crust; thin section FO2-A1. i Muranella parvissima (Dragastan); thin section FO1-H(2).