Similiclypeina aff. somalica Conrad, Peybernès & Masse, 1983

Bucur, Ioan I., Jovanovic, Divna, Radoicic, Rajka, Sudar, Milan & Mircescu, Cristian Victor, 2021, Lower Cretaceous Carbonate Deposits From The Derezna Borehole (Carpatho-Balkanides, Eastern Serbia) And Remarks On Some Dasycladalean Algae, Acta Palaeontologica Romaniae 17 (1), pp. 3-14 : 5-12

Similiclypeina aff. somalica Conrad, Peybernès & Masse, 1983

Fig, 5h(Ss)

Remarks

This alga was first illustrated by Bucur (1993, pl. 3, fig. 7, 9b, 10, 12-25) from limestones located in the median part of the Reșița- Moldova Nouă zone. It was described as a species which is similar to Clypeina somalica ( Conrad, Peybernès & Masse, 1983) , but with generally smaller dimensions, and was attributed to the genus Similiclypeina Bucur, 1993 . The same alga was illustrated by Bucur et al. (2000, pl. VII fig. 19-24) from the eastern Pontides ( Turkey). The specimen identified in Eastern Serbia has dimensional values within the variation range of the specimens described from the Reșița- Moldova Nouă Zone by Bucur (1993) and the Kirkaova section, Kale-Gümüshane region, NE Turkey ( Bucur et al., 2000) (see Table 2 ).

The genus Similiclypeina was introduced by Bucur (1993) in order to reunite the Clypeina -like dasycladaleans which contain non-spaced whorls that touch each other and are often vertically welded. The genus diagnosis was the following ( Bucur, 1993, p. 105): „Thallus made up of overlapping whorls of primary ramifications. Ramifications slightly tilted with respect to the axial cavity, welded at their proximal part and, usually, loose at their distal end. Overlapping whorls touching one another, partly welded into a more or less compact calcareous sheath“. Some species doubtfully attributed to the genus Clypeina Michelin (e.g., Clypeina ? alrawii Radoičić, 1978; Clypeina? somalica Conrad et al., 1983 ) have been transfered to the genus Similyclypeina , and a new species, Similiclypeina conradi was introduced ( Bucur, 1993).

Sokač (1996) created the genus Piriferella with Piriferella spinosa as type species from the Lower Cretaceous of Croatia. He introduced the species Clypeina somalica in the new combination as Piriferella somalica . According to Sokač (1996, p. 29): „By the arrangement and density of branches and their independent mode of growth, all of which results in a similar general appearence of the thallus, Piriferella nov. gen. comes more closely to Similyclypeina , which is however, characterized by Actinoporella type ramifications (i.e., gradually widening toward exterior) and by vertically flatened coronas.“ We have to underline here that in the diagnosis of the genus Similiclypeina ( Bucur, 1993, p. 105) , no information is given on the presence of Actinoporella type ramifications (i.e., laterals), or possible coronas. Further comments on the genus Similyclypeina are made by Sokač, 1996 at page 30 where he describes „ Piriferella somalica “ stating: „Therefore, Similyclypeina would include forms with different characteristics: forms with horizontally, elongated corona- or vestibule-like swellings in the proximal part of the ramifications ( S. conradi and S? iustiniani), forms with no such swellings at all ( S. alrawii and S. somalica ) and forms with two types of secondary ramifications, one growing out from the cylindrical stalk of the thallus (sic!), another on the primary branches ( S. pupnatensis). As basal swelling of ramifications is generally agreed to be crucial for distinguishing Actinoporella from Clypeina , and thus became, by general consensus, a criterion of generic rank, it would be illogical to erect a genus that would unite forms with and without such an important feature“. In fact, Sokač (1996) transfers the characterstics of the species S. conradi to the entire genus without taking into account the given diagnosis of genus Similiclypeina . In addition, he mentions corona located inside the whorls, between the laterals. The enlarged portion at the base of the laterals of S. conradi is interpreted as two coronas. Bucur et al. (2000, p. 452) commented on these aspects, showing that (translated from French): „The presence of ″corona″ in Similiclypeina conradi (type species of the genus Similiclypeina ) underlined by Sokač (1996), who consider that the author neglected this character in the generic diagosis is, in our opinion, inacceptable. Following Berger and Kaever (1992) „... Corona superior = the total of the circularly arranged processes at the upper side of a cap at the insertion of the cap rays into the stalk (main axis). Each cap ray bears one corona segment, each corona superior segment bears a speciesspecific number of protuberances... Corona inferior = the total of circulary arranged processes at the underside of the cap surrounding the insertion of the cap rays into the stalk. If a corona inferior is present, one corona process belongs to each cap ray. The corona inferior is always devoid of protuberances“. Starting from this definition we can ask how could a ″corona″ be formed between the laterals of the same verticil? Because it is not corona, the specific aspect of the laterals of S. conradi was not considered as a character of generic value, and was not mentioned in the genus diagnosis...“ In other words, if we follow the logic of the existence of corona on the lateral basal side of the laterals, we have to speak about „left corona“ and „right corona“, an assumption that does not correspond to any of the known characteristics of dasycladalean algae. Otherwise, the characteristic aspect of the laterals of Similiclypeina conradi could result from the presence of non-calcified reproductive cysts in the lower part of the laterals. Regarding Humiella ? pupnatensis Sokač, 1987, [synonymized by Bucur (1993) with Similiclypeina somalica ], we question the existence of "secondary ramifications" starting directly from the stalk. Probably the author ( Sokač, 1996) was refering to sterile and not secondary ramifications. In addition, Sokač (1987) speaks about secondary short ,,ramifications,, located in the distal part of the primary fertile ,,ramifications,,. However, these secondary laterals are difficult to observe and they may correspond to simple irregularities of the calcareous sleeve.

The genus Piriferella ( Sokač, 1996) was created based on the typical ,,pyrifer,, (pyriform would be better) shape of its laterals ( Sokač, 1996, p. 28). In fact, neither the type species ( P. spinosa ) nor „ P. somalica “ are characterized by typical pyriform laterals. The laterals of Piriferella spinosa have a variable shape that ranges from ovoidal to vesiculiform or slightly phloiophorous/rarely pyriform (see Sokač, 1996, pl. XXI). Otherwise, if we consider the laterals of Piriferella as typical pyriform then this genus would become a junior synonym of the Triassic genus Physoporella Steinmann, 1903 emend. Grgasović 1995 (see also Bucur et al., 2000, p. 452). Based on the considerations stated above on the genus Similiclypeina, Bucur (2000) transfered the species Heteroporella? paucicalcarea Conrad, 1970 to the genus Similiclypeina in the new combination Similiclypeina paucicalcarea (Conrad) . Controversies concerning the two genera ( Similiclypeina and Piriferella ) and their attributed species continued in the following years. In an abstract published in the abstract volume of the 6th regional symposium on calcareous algae, held in Milano, Conrad et al. (2009) restricted the componence of the genus Similiclypeina to the type species. All the above mentioned species were attributed to the genus Piriferella . Moreover, the authors ( Conrad et al., 2009) proposed the synonymization of the species Clypeina somalica Conrad, Peybernès & Masse, 1983 , Piriferella spinosa Sokač, 1996 , and Salpingoporella verrucosa Sokač, 1996 under the combination Piriferella somalica (Conrad, Peybernès & Masse) . On the poster presented by the same authors ( Conrad et al., 2009) during the Milano symposium the species Heteroporella? paucicalcarea was also transfered to the genus Piriferella in the combination Piriferella paucicalcarea (Conrad) . Finally, the author’s initiative ( Conrad et al., 2009) to publish a paper on this subject was abandoned. However, this approach was accepted without any objections by Bucur (2011), at least for Piriferella paucicalcarea . It was rightly rejected by Granier (2013). Granier ascribed the species Clypeina somalica to the genus Holosporella (see also Granier, 1992), restricted the interpretation of the genus Similiclypeina to its type species ( S. conradi ) and ascribed the species Heteroporella? paucicalcarea to the genus Clypeina in the new combination Clypeina paucicalcarea (Conrad) . In fact, the shape of the laterals of Heteroporella? paucicalcarea has nothing to do with the pyriform shape. Thus, even if one accepts the well establishment of the genus Piriferella , the species paucicalcarea cannot be assigned to this genus.

It is obvious that even Granier (2013) eludes the diagnosis of the genus Similiclypeina ( Bucur, 1993) by interpreting it in the sense of the type species, S. conradi . The author ( Granier, 2013, p. 60) mentions: „...it would be safer to revert to Bucur's (2000) view: Heteroporella? paucicalcarea is a Clypeina -like species the verticils of which are set rather close together. Because the species lacks the typical pattern of the laterals in Similiclypeina conradi Bucur, 1993 , it should "naturally" be relocated among the representatives of Clypeina ( Michelin, 1845) .” Or, the reason to erect the genus Similiclypeina ( Bucur, 1993) was to group together species with Clypeina -like verticils but with closed-set verticils. Frequently, Clypeina species are preserved as separate whorls spread in the sediment. The large distance between successive whorls leads to a rare potential of preservation within the succession (see the example of Clypeina besici Pantić in Granier & Deloffre, 1994 ( Pantić, 1965), or Clypeina helvetica Morellet & Morellet, 1918 from Eocene (cf. Schlagintweit et al., 2013); see also Clypeina in Genot, 1980; 1987; 2009, and in Granier & Lethier, 2019). By contrast, Heteroporella? paucicalcarea presents a compact skeleton since its whorls are welded in their vertical succession (see for instance the detached specimens in Bucur, 2011, pl. 1, fig. 6). As a consequence, the generic affiliation of these controversial species still remains open.