XITOMITRIDAE

Suzuki, Noritoshi, Caulet, Jean-Pierre & Dumitrica, Paulian, 2021, A new integrated morpho- and molecular systematic classification of Cenozoic radiolarians (Class Polycystinea) - suprageneric taxonomy and logical nomenclatorial acts, Geodiversitas 43 (15), pp. 405-573 : 475

Family XITOMITRIDAE

O’Dogherty, Goričan & Gawlick, 2017

Xitomitridae O’Dogherty, Goričan & Gawlick, 2017 : 60.

TYPE GENUS. — Xitomitra O’Dogherty, Goričan & Gawlick, 2017: 62 [type species by objective designation: Stichomitra ? tairai Aita 1987: 72].

INCLUDED GENERA (CENOZOIC ONLY). — Dictyomitrella Haeckel 1887: 1476 (= Parvimitrella n. syn.).

DIAGNOSIS. — A multisegmented Nassellaria whose cephalis is both small and poreless. All of its segments, except for the cephalis, are covered with a latticed meshwork of uniform sized pores. The distal end of the test is open or nearly closed, without distal projections or appendages. The cephalic initial spicular system present at least a MB, A-, V-, D- and double L-rods. MB is rises obliquely to the A-rod side. Thus, the basal ring of the cephalis is also oriented obliquely. The A-rod extends upright in the cephalic cavity to attach itself to the cephalic wall or even penetrate the wall. An amphipyndacid-like divider is visible in the cephalis. The divider in the proximal upper-section is constructed by the MB, D- and double L-rods.

STRATIGRAPHIC OCCURRENCE. —Early Aalenian-late Middle Eocene.

REMARKS

The Xitomitridae were related with the Canoptidae , Parvicingulidae and Xitidae ( O’Dogherty et al. 2017) . The cephalic structure of the type species of Xitomitra O’Dogherty et al. 2017 (the Middle-Late Jurassic Stichomitra ? tairai Aita, 1987) is well recognized in its paratypes ( Aita 1987: pl. 3, fig. 8a). Referring to this photo, “the divider” in the proximal top is constructed by MB, D- and double L-rods. This does not correspond to the characteristics of the divider in Amphipyndacoidea . The proximal top of the Xitomitra tairai consists of a cephalis and thorax. The divider in Xitomitra is poorly developed in comparison to the basal ring of the cephalis in the Eucyrtidiidae . Conversely, Dictyomitrella , and the Paleogene member of the Xitomitridae appear to have a well-developed cephalis basal ring such as in the Eucyrtidiidae ; however, the MB of Dictyomitrella is obliquely oriented. The cephalic view of the type species (lectotype) of Dictyomitrella is also shown in pl. 22, figs 1e and 1f of Ogane et al. (2009b).

Phylogenetic Molecular Lineage II ( Sandin et al. 2019)

DIAGNOSIS. — Anatomically, one or two segments, but usually one segment, is observed. This is true for most cases except Lampromitridae and some members of the Artostrobiidae .If a subsequent shell develops, the final segmented part is not divided by an inner ring. This is unlike the Eucyrtidiidae . No common characteristics in the cephalic structure are recognized among the members. No feet are observed except in some members of the Acanthodesmioidea and Diacanthocapsidae .

REMARKS

Lineage II includes the Plectopyramidoidea (originally Acropyramioidea), Carpocanioidea (originally Carpocaniidae ), Artostrobioidea , and Acanthodesmioidea (originally Acanthodesmoidea in Sandin et al. 2019). Although the independency of the Lineage II from the other Lineages is supported with 100% PhyML bootstrap values with 10 000 replicates (BS) and>0.99 posterior probabilities (PP); the independency of superfamilies inside Lineage II is only supported for the Acanthodesmioidea with 100% PhyML bootstrap values with 10 000 replicates (BS) and>0.99 posterior probabilities (PP). The trees of the remaining three superfamilies have not been agreed upon within Lineage II. As for the Carpocaniidae and Artostrobiidae , both families have a common structure with very complex arches around the V-rods. Thus, it may not be necessary to separate them at the superfamily-level (see remarks for the Carpocanioidea , Carpocaniidae and Artostrobiidae ). However, this possibility should be carefully examined in consideration of the Mesozoic members.