Archaeodictyomitra massarii Dumitrica & Dieni & Massari 2022, nov. sp.
Creators: name: Dumitrica, Paulian
name: Dieni, Iginio
name: Massari, Francesco
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Chromista
Radiozoa
Polycystina
Nassellaria
Archaeodictyomitridae
Archaeodictyomitra
Archaeodictyomitra massarii

description: Archaeodictyomitra massarii Dumitrică nov. sp.   
Figs. 13 g-k,?14l  
 1982 Archaeodictyomitra sp. – Okamura & Uto, pl. 1, figs. 16-19; pl. 5, fig.7; pl. 6, fig. 2.   
 1989 Mita sp. A – Tumanda, p. 8, pl. 3, fig. 13.   
 Description. Shell long ovoid with usually 6-8 segments and about the two apical thirds conical with slightly convex sides, and the distal third narrowing. Surface with 9 to 11 continuous and deep costae from top to distal end on half the perimeter. Wall thick, of commonly cavernous structure, with rather deep intercostal areas, each one with a row of dense circular pores on the inner side of wall, and oval or transversally elongated and usually very complicated sculpture on the outer surface. Sculptures resulted from the cavernous structure of wall. Distal part without a neck.   
 Studied material. Six illustrated specimens.   
 Holotype. Figure 13i, coll. MGP-PD, stub PD120 - OZ839- R02-12.   
 Dimensions. Length of shell 140-200 µm, maximum diameter 86-96 µm.   
 Etymology. The species is dedicated to Prof. Francesco Massari for his contribution to the knowledge of the geology of eastern Sardinia.   
 Remarks. What is interesting in the population of this new species is that most pores of some specimens are slitshaped and transversally positioned on the surface of shell, and the surface is sculptured (Figs. 13g 1, k 2) whereas on the inner side of the wall the pores are circular (Fig. 13k). This difference is the result of the cavernous structure of wall (Figs. 13k, k 1), which seems to be original, not secondary, resulted from a differential dissolution of the shell. The same kind of superficial sculpture and transversally or obliquely directed slit-like pores are present in some specimens of Archaeodictyomitra mitra Dumitrică 1997, a species quite close morphologically to this new species, from which it differs by having a slightly spindle-shaped shell and the distal end without a neck, and also in the specimens of Eucyrtidium brouweri illustrated by Tan (1927) in pl. 11, figs. 90 and 91. The cavernous structure of shell, that was never mentioned in Radiolaria, seems to be characteristic of several Lower Cretaceous archaeodictyomitrid species or only specimens illustrated by Thurow (1988, pl. 6, figs. 18-22; pl. 7, figs. 7), O’Dogherty (1994) on his pl. 5, figs. 4-6, 12, 23, 25-27, 31-33; pl. 6, figs. 1-4, 10, 15, Jud (1994) on Thanarla guta Jud (1994, pl. 23, figs. 4, 5, Thanarla pulchra, pl. 23, figs. 6, 7) or other authors. Some specimens of these species in his pl. 5, figs. 4, 23, 26), to cite only the most visible, have also pores on the top of costae. We do not know whether this cavernous structure has a taxonomic meaning or a palaeobiological one. All these specimens are archaeodictyomitrids. Anyway, it is interesting to mention it, radiolarian skeleton being known to be compact, by comparison with that of Phaeodaria, that has an alveolar or porous structure (Takahashi & Hurd, 2007; Dumitrică, 2016).   
 Range and occurrence. Berriasian to Barremian of Masirah Island, Oman, and upper Valanginian of Sardinia.
description: Published as part of Dumitrica, Paulian, Dieni, Iginio & Massari, Francesco, 2022, Valanginian Radiolarians Of Ne Sardinia (Italy) In The Frame Of The Weissert Event, pp. 97-159 in Acta Palaeontologica Romaniae 18 (2) on pages 136-138, DOI: 10.35463/j.apr.2022.02.06, http://zenodo.org/record/12583131