Pseudoclypeina ? crnogorica RADOIČIĆ , 1972 – Stratigraphic revision and taxonomic note on a little known dasycladalean alga from Montenegro

Pseudoclypeina? crnogorica was first described in 1972 from the Lower, 
 Cretaceous limestone of the Njegos Mt. area, Montenegro, Dinaric Carbonate 
 Platform. It differs from other species of the genus Pseudoclypeina by its 
 calcification pattern, the shape and relative length of the first and second 
 order laterals, and by the presence in the type-material (a thin section 
 containing the holotype) of sections standing for the sterile portion of the 
 thallus. This is why in this paper, the generic name is left in open 
 nomenclature. On this occasion the species, whose presence is also reported 
 from southern Iran, is re-described and better illustrated, based on material 
 originating from other outcrops in Montenegro. The stratigraphic position is 
 reviewed as well. Pseudoclypeina? crnogorica occurs in shallow water inner 
 platform facies of early Neocomian age, along with Selliporella neocomiensis.

In many areas of western Montenegro, the Jurassic-Lower Cretaceous stratigraphic column is more or less reduced due to frequent subaerial exposures of different duration, resulting in the presence of significant stratigraphic gaps corresponding or not to the presence of white bauxite (RADOIČIĆ & VUJISIĆ 1970;RADOIČIĆ 1993).One of such successions, with white bauxite ranging from the Neocomian to the Upper Albian-Cenomanian, is found in the Velimlje area, south of the Njegoš Mt.The lower-middle part of the Neocomian column, with numerous subaerial exposures consists, first of a limestone containing Daturelina co-stata and Campbelliella striata, followed by a coprogenous limestone with Salpingoporella annulata, coprolites and rare foraminifers and, finally by a limestone with fragments of an unknown dasycladalean alga later identified as Pseudoclypeina?crnogorica.
In the region of Prekornica and Lebršnik Mts, in northern part of the Geological map sheet Titograd at scale 1:100000, the "Ttitonian-Valanginian" limestone-dolomite succession ("J/K") is largely distributed, transgressive on the Upper Triassic or Triassic-Liassic deposits (ŽivaljeviĆ et al. 1971, 1973).Location is in the southernmost part of the large Nikšićka Župa bauxite bearing region, north of the Zeta intra-platform furrow.A Neocomian limestone containing P.? crnogorica was found on the road east of the Lebršnik Mt.Southward along the same road, two outcrops of a limestone containing Selliporella neocomiensis, Clypeina neretvae and P.? crnogorica were sampled (the first sampling, near Lisac, is type locality of S. neocomiensis).In all known localities of Montenegro, P.? crnogorica occurs in Neocomian sediments, most probably dated Late Berriasian or Late Berriasian-Early Valanginian.RADOIČIĆ, 1970.Three species of the genus Pseudoclypeina have been described from southern Montenegro (Dinaric Carbonate Platform): P. cirici RADOIČIĆ 1975, non 1970, the genotype, P. farinacciae RADOIČIĆ 1975, non 1970, both from the Upper Kimmeridgian, and P.? crnogorica RADOIČIĆ 1972, from the "Barremian-Lower Aptian" (now dated Neocomian).Because P. cirici differs from the other two species in having three orders of branches, BASSOULLET et al. (1978), suggested that it would "préférable de signaler dans la diagnose du genre que Pseudoclypeina peut présenter deux ou trois ordres de ramification."Which, at once, is accepted in the present paper.

Genus Pseudoclypeina
A new species, Pseudoclypeina distomensis, was introduced by BARATTOLO & CARRAS (1990) from the Lower Kimmeridgian of the Parnassus Carbonate Platform, Greece.Accoding Barattolo and Carras "The 'tertiary branch', which Radoičić's diagnosis of Pseudoclypeina is referred to, is not considered in such a manner for the following reasons: it originates without ramification (absence of ramification); it is on the same extension of the secondary branch; branches of a same order bearing narrowings are already known and have been accepted by former authors [e.g.Palaeodasycladus mediterraneus (PIA)]".
In the opinion of the present first author (RR), the tertiary branch (lateral, segment) of Pseudoclypeina cirici (in prolongation of secondary which has integral inner calcification including mould of reproductive organ and the pore at the top) is rarely together preserved due to brittle joint with secondary.This part of the skeleton has the form to which term branch (lateral, segment) is more corresponding, in the same way as the term "narrowing" (constriction) more corresponds to Pseudoclypeina distomensis.Such distinction may be irrelevant if the biological function is the same, i. e. protection of the fertile organ.
Both species, P. cirici followed by P. distomensis occur in the shallow-water, Late Jurassic succession of the Distomon area, Parnassus Carbonate Platform.In the nearby Kallidromo Mt. they occur together as well (recent unpublished data, N. Carras).In the future, a detailed study may show to what extent the two species are reciprocally related.

Pseudoclypeina? crnogorica RADOIČIĆ, 1972
Fig. Diagnosis.Thallus cylindrical, relatively large, the main stem bearing regularly spaced shallow funnelshaped whorls of numerous laterals.Primary laterals ovoid, bearing a tuft of 4-6, rather large and long secondary laterals, gradually widened outwards and no further ramified.Primary and second order laterals equally inclined upwards.Calcification articulated, individually coating the whorls of laterals.Reproductive organs (cysts) not observed, presumably located in the primary laterals (cladosporous type).
Notes on the generic attribution.Pseudoclypeina?crnogorica differs from other species of the genus in the type of calcification, comparatively standard (originally aragonitic), made of an external coat of colorless sparry calcite.By contrast, in Pseudoclypeina cirici, P. farinacciae and P. distomensis an inner, yellowish coat of calcite is present, strongly recalling if not identical to the calcification pattern found in Clypeina jurassica.The thallus of P.? crnogorica is comparatively rather small, with a smaller number of laterals per whorl, noting that in P. farinacciae other biometrical values are incomplete because the skeleton is altered by dissolution.Finally the size ratio between primary and secondary laterals is almost opposite, denoting a substantial difference.This is why in this paper we prefer to put the species in open nomenclature.
Quoting BUCUR (2013) "P.crnogorica, the fourth species of the genus Pseudoclypeina, differs from the other species not only in its calcification pattern, i.e., blocky sparite, but also in the size ratio between the primary and secondary laterals.The primary laterals are half the length of the secondary ones and ovoid in shape; this is not typical for the genus Pseudoclypeina, and makes the assignment doubtful.Based on the morphology and size ratio of the laterals, this species is more likely to be affiliated to Selliporella, as emended by BARATTOLO et al. 1988.The general morphology of the thallus broadly resembles that of Selliporella neocomiensis (see BUCUR & SĂSĂRAN, 2003)".In P.? crnogorica however, the secondary laterals are phloiophore (widening out), as compared to pirifere (the opposite) in Selliporella.A possible transfer to Dissocladella is all the same rejected, because of different morphology and primary to first -second order laterals length ratio.That is why we prefer, at the moment, to assign the species with doubt to the genus Pseudoclypeina, avoiding creating another genus based on insufficient data.For the moment this standpoint is shared (pers.comm.) by two algologists, namely Filippo Barattolo (Naples) and Ioan I. Bucur (Cluj).
Two singular sections are illustrated in Pl. 3: Fig. 4 shows the oblique section of a fragment of whorl with smaller primaries, sparse and long secondaries); Fig. 5 shows the tangential section of strongly tilted second order laterals in cup-like arrangement.Most probably, these two sections belong to the youngest, sterile portion of the thallus, in a way similar to some recent genera.In the studied material the calcified main stem is not preserved.Membranes of the primary and secondary laterals are seldom preserved as a thin micritic coat (Fig. 2, the holotype).Calcification, made of colorless sparry calcite enclosing the primary and secondary laterals, becomes thinner at the thallus periphery and is usually not preserved distally.Partial recrystallization occurs, stronger around the top of the primary and proximal portion of the secondary laterals.Seldom, all of a whorl or fragment of whorl is completely recrystallized (Pl.2, Fig. 3; Pl. 4, Fig. 2).Located in the Srijede area, the type-level of P. crnogorica consists of an inhomogeneous limestone (wackestone, packstone, peloidal limestone, grainstone containing micrite lithoclasts).The species mainly occurs as isolated whorls and fragments.From this bed, 11 thin sections were made from sample 07753a (RR1922-1925/1-1926/1-1930).Also six thin sections were made from sample 06230 (RR1794-1795/1-1798) originating from another, neighboring location.Finally, two thin sections were made from sample 03669 (RR1542,1543) originating from the Lebršnik Mt. area and one thin section from sample 03681a (RR1567) south of Lebršnik.
Algae labeled Dasycladacea sp. by FOURCADE et al. (1972, pl. 2, figs. 5-8) illustrates a specimen originating from the upper Barremian of Benizar-Otis area, southeast Spain, which has been included in P. crnogorica by BASSOULLET et al. (1978, p. 217).The same taxon, most probably, was illustrated by MASSE (1995, pl. 2, fig. 16) under the name of Pseudoclypeina sp., from the upper Barremian of Orgon, SE France.Compared to P.? crnogorica the calcification pattern of these specimens is the same but the shape of the primary laterals differs (elongated versus ovoid), and the length ratio of the first and second order laterals is the opposite, indicating a new taxon.
Stratigraphic and geographic distribution.In Montenegro, Pseudoclypeina?crnogorica, Selliporella neocomiensis and Clypeina neretvae occur in an inner platform limestone-early diagenetic dolomite interval presumably dated Upper Berriasian-Lower Valanginian.Besides the foregoing species, P. crnogorica is associated with common Salpingoporella annulata, Salpingoporella spp., Clypeina spp., some other small and undetermined species, fine algal debris, Favreina spp.and microgastropods.In southern Montenegro, locations form a discontinuous belt extending from northwest of Nikšić to the south-east, in the mountains area north of Podgorica (Titograd).
Tangential section of whorl with, in the proximal part, laterally slightly compressed primary laterals, elliptic in section.Note the calcified membrane of primary laterals (black micritic line).Thin section RR1926/1.

Figs. 2-5.
Oblique sections of whorls.In Figs. 2, 3 recrystallization is stronger around the top portion of the primaries and proximal portion of the secondaries.Calcification is thinner in Fig. 5. Thin sections RR1924, 1928, 1925/1, 1925/1. Figs. 6, 12. Tangential sections of the secondary laterals.Thin section RR1926.Fig. 7. Fragment of whorl showing the ovoid first order laterals and long gradually widening outward secondaries; the section plane follows the inclination of laterals.. Thin section RR1926.
Tangential section of a partially recrystallized whorl.Note the micritic membrane in transverse sections of two primary laterals, and the more recrystallized proximal portion of the secondaries.Thin section RR1926/1, iso-Fig.2. Deep tangential section of a recrystallized whorl.Note the transverse sections of primary with micritic membrane.Thin section RR1796.Ill-preserved, fractured fragment of a whorl.The section plane more or less follows the inclination of the laterals.Left: most of the primary laterals are visible, as well as the slightly deformed secondaries and corresponding swollen distal part (arrow).Thin section RR1930, isotype.
Fig. 2. Tangential-oblique section progressively cutting three, partly recrystallized whorls.Only the primary laterals are visible in the upper, deeper cutting, whorl.Thin section RR1794.

Fig. 13 .
Fig. 13.Tangential-oblique section cutting the distal parts of three whorls in advanced degradation process.Note the micritic membrane in some of the second order laterals.Thin section RR1794.