Cryptamphorella alieviana, 2022

Dumitrica, Paulian, Dieni, Iginio & Massari, Francesco, 2022, Valanginian Radiolarians Of Ne Sardinia (Italy) In The Frame Of The Weissert Event, Acta Palaeontologica Romaniae 18 (2), pp. 97-159 : 116-117

Arcanicapsa (?) alieviana Dumitrică n. sp.

Figs. 9p, r, s, s 1

1988 Williriedellum sp. A . – Thurow, p. 408, pl. 8, fig. 2.

2009 Hiscocapsa grutterinki (Tan) – Ishii et al., p. 347, pl. 20, fig. 9.

Description. Shell ovoid to conical, three-segmented, increasing very fast in diameter and length distally. Cephalis hemispherical, smooth and without apical horn, wall perforated by very small and sparse circular pores. Thorax twice as large as cephalis, with tubercles disposed in a single irregular circumferential row. Pores are very small, circular, distributed irregularly or in more or less regular circumferential rows. Collar boundary is rather well marked by the sudden enlargement of thorax. Sutural pore is not visible. Abdomen is very large, spherical or ovoidal and tuberculate, tubercles not interconnected by crests but by thicker intervening bars. Pores are circular and arranged in circumferential rows and quincuncially distributed. Pores are larger diameter at the middle part of the abdomen and smaller at the proximal and distal parts. At a greater magnification ( Fig. 9s 1 ) one can also see that the borders of pores are protruding and the middle parts of interporal areas are concave. Conversely, the bars at the top of the tubercles have the surface flat or convex. Lumbar boundary is rather well marked by the sudden increase in diameter of the abdomen. Distal part of abdomen has no aperture.

Studied material. Three illustrated specimens, two in sample OZ825, one in OZ837.

Holotype. Figure 9p , coll. MGP-PD, stub PD120 -OZ825- R12-4 .

Paratype 1. Figure 9s , coll. MGP-PD, stub PD120 - OZ825- R12-7 .

Paratype 2. Figure 9r , coll. MGP-PD, stub PD120 - OZ837- R06-16 .

Dimensions. Length of test 180-230 µm, of cephalis 20- 25 µm, of thorax 25-35 µm, and of abdomen 130-155 µm; diameter of cephalis 6 µm, of thorax 60-70 µm, of abdomen 150-175 µm, total length of shell 180-230 µm.

Etymology. The species is dedicated to K. S. Aliev for his research on the Lower Cretaceous radiolarians of Azerbaijan at a time when the electron microscope was not a common research instrument as today.

Remarks. Arcanicapsa (?) alieviana n. sp. differs from all congeneric species with tuberculate shell by having the pores of the middle part of abdomen larger than those of the proximal and distal parts and arranged in circumferential rows moreover, the pores of each circular row alternate with those of neighbouring circular rows. A very similar species was illustrated by Thurow (1988) as Williriedellum sp. A from the upper Hauterivian to lower Aptian assemblage of North Atlantic. In this species an arrangement of pores in circular rows and also a difference in the size of pores can be observed. Another specimen, quite similar to the Sardinian species, was illustrat- ed by Ishii et al. (2009, pl. 20, fig.9) as Hiscocapsa grutterinki (Tan) , from the Berriasian of ODP Hole 1213B-14R-1, 17-19 cm, North Pacific. On this specimen the difference in size between the abdominal pores of the middle part and those of the proximal and distal parts is also well visible.

Other species with which this new taxon can be compared and confounded are Tricolocapsa clivosa Aliev, 1967 , Cryptamphorella clivosa (Aliev) in O’Dogherty (1994, p. 211, pl. 35, figs. 1-8) or Williriedellum peterschmittae Schaaf, 1981 , and others, to cite only a few species with similar morphology occurring in the Lower Cretaceous. O’Dogherty’s specimens assigned to Tricolocapsa clivosa Aliev do not seem to be conspecific with the species described from the Valanginian of the eastern Caucasus (NE of Azerbaijan) by Aliev (1967). The first argument is the difference in age (early Aptian, O’Dogherty’s specimens, versus Valanginian, Aliev’s species, age based on foraminifera and ammonites). The second argument refers to morphology: T. clivosa is ovoid, whereas the specimens illustrated by O’Dogherty are rather spherical. In this situation, the best candidate for our species could be Aliev’s species that has the same age and also an ovoid shape with tuberculate wall. The problem is that we do not know exactly the typology of the abdominal pores of the specimen illustrated by Aliev, especially on the middle part of the abdomen. In his original description, he wrote that the pores are easily visible at a higher magnification and that they are circular in shape and disposed in a chess manner. This would mean “in square manner”, which is very strange for tuberculate shells. Probably he would have liked to say “in a regular manner” like a quincuncial disposition, as in the specimens illustrated later by O’Dogherty. Aliev did not mention a circular disposition and a difference in size between the pores from the equatorial and periequatorial circles and those disposed toward the distal and proximal parts of the abdomen. So, Aliev’s 1967 species Tricolocapsa clivosa is difficult to recognize not only in the SEM images of the specimens published by O’Dogherty, but also in our specimens. In this situation, despite the similar age (Valanginian), we prefer to consider our three specimens as belonging to a new species, that differs from Tricolocapsa clivosa by having the equatorial and “tropical” abdominal pores much larger than those disposed towards the proximal and distal parts of this chamber. As concerns Williriedellum peterschmittae Schaaf , it generally resembles Cryptamphorella clivosa (Aliev) of O’Dogherty 1994, from which it differs by having a distal aperture, which means that it belongs to another genus, as originally determined.

Other comparisons from generical point of view could be made with the middle-late Jurassic species Sethocapsa funatoensis Aita 1987 , the taxonomic place of which varied in time among Sethocapsa , Zhamoidellum , Hiscocapsa and Arcanicapsa , according to authors (see Odogherty et al. 2017, p. 45). With this species it has in common only the three-segmented shell, tuberculate abdomen, the absence of distal aperture and sutural pore and little encased cephalis and thorax, but differs by having also tuberculate thorax and abdomen. In this situation we assigned it questionably to the genus Arcanicapsa .

Occurrence. Upper Valanginian of Sardinia, samples OZ825 and OZ837 .

Figures

Fig. 9 a, b - Eucyrtidiellum sardoum Dumitrică n. sp.: a, a1 - holotype, OZ836; b - paratype, OZ839. c-e, g - Hemicryptocapsa capita Tan: c - OZ838, d - OZ824, e - OZ837, g - OZ839. f-f2 - Gongylothorax oculoporus Dumitrică n. sp.: OZ824 and OZ826. h – Gongylothorax (?) sp., OZ834. i-i2 – Gongylothorax verbeeki (Tan), OZ824; i1, i2 - details of apical and apertural parts. j, j1, j2 - Williriedellum buekkense (Kozur), OZ824: j – lateral view, j1 – apical view with sutural pore, jb – distal view. k – Arcanicapsa simplicissima Dumitrică n. sp., OZ836, k1 – distal view showing the apical rosette. l-o, t, t1, u - Kozurium hindei (Tan): l, l1 - OZ837, m - OZ839, n - OZ834, o - OZ836, t-t1 x300, OZ825, n1 – distal aperture of fig. 9n. p-s1 - Cryptamphorella alieviana Dumitrică n. sp.: p, s - OZ825, r - OZ837, s1 detail of test of fig. s. Figs. p-s x200; figs. c-e, g x250; figs. a, a1, b, f, f2, h, h1, i, k-o, t, t1, x300; i1, i2, m x400.

Fig. 1 Geologic map of the Siniscola area, NE Sardinia (from Dieni & Massari, 1971, updated in 1986). Legend: a - Recent and present alluvial deposits (Holocene). b - Scree deposits (Würm-Holocene). c - Detrital cones mostly composed of gelifraction limestone clasts (“éboulis ordonnés”) (Würm-Holocene). d - Uncemented alluvial cones mostly consisting of limestone clasts (Würm-Holocene). e - Terraced alluvial deposits composed of clasts of basement rocks (Riss?). f - Tightly cemented and dismembered alluvial cones mostly made up of gelifraction limestone clasts (Riss?). g - Cuccuru ’e Flores Conglomerate: polymict, chaotic and thick-bedded breccia and stratified sandstone (middle Eocene). h - Siniscola Marl: grey and grey-yellow marl and, in the upper part, alternating marl/marly limestone with ammonites and very abundant radiolarians and sponge spicules (late Valanginian). i - Schiriddè Limestone: light-brown cherty limestone and limestone with marly interbeds, containing ammonites, radiolarians, sponge spicules and calpionellids (early Valanginian). j - Monte Bardia Limestone: thick-bedded to massive white limestone in places bioconstructed, with corals, nerineids, etc. (early Tithonian - late Berriasian). k - S’Adde Limestone: light-brown to grey fine-grained, well-bedded limestone, condensed with hardgrounds near the base, cherty in the upper part, with ammonites and belemnites in the uppermost part (latest Bathonian - earliest Tithonian). l - Dorgali Formation: well bedded quartz-arenitic and locally ooidal brown dolostone (middle-late Bathonian). m - Crystalline basement (phyllite, micaschist, paragneiss, quartzite, etc.) (Palaeozoic). n - Fault. o - Attitude of beds and schistosity planes. p - Limits of slumped masses of Jurassic formations (Quaternary). q - Concave-upward slip surfaces delimiting rotational slumps (Quaternary). r - Edge of fluvial terrace. s - Quarry. A-A’ Trace of the geological section of Fig. 2. (extracted from Bottini et al., 2018).