O’Dogherty et al.—Jurassic radiolarians from the Eastern Alps


Remarks.—Loopus mexicanus is distinguished from other Loopus included by having a lobate outline with well- pronounced constrictions.


Loopus venustus (Chiari, Cortese, and Marcucci in Chiari et al., 1997)


Figure 7.67−7.70 1982? Unnamed multicyrtoid nassellaria Adachi, pl. 2, fig. 7.


1986a Pseudodictyomitra (?) sp. D Matsuoka, pl. 4, only figs. 2−6.


1986b Pseudodictyomitra (?) sp. D Matsuoka, pl. 2, fig. 11; pl. 3, figs. 12a–b.


1988 1988 1990 1997


1997 2006


Pseudodictyomitra sp. D Wakita, pl. 1, fig. 12. Pseudodictyomitra (?) sp. D Wakita, pl. 4, fig. 12. Pseudodictyomitra (?) sp.DMatsuoka and Oji, pl. 1, fig. 8.


Cinguloturris (?) venusta Chiari, Cortese, and Marcucci in Chiari et al., p. 66, pl. 2, figs. 4−5.


Cinguloturris (?) sp. Chiari, Cortese, and Marcucci in Chiari et al., pl. 2, fig. 6.


Dictyomitrella (?) sp. 3 O’Dogherty et al., p. 436, pl. 3, fig. 16.


2006 Loopus venustus;Danelian et al., p. S40, pl. 1, figs. 21–23.


Remarks.—We group a large variety of Loopus with complex irregular ornamentation of disconnected short costae and small polygonal depressions in L. venustus.This species clearly differs from L. primitivus,which has regularly distributted vertical costae, no polygonal depressions, and stronger strictures.


Genus Mizukidella new genus


Type species.—Dictyomitrella? kamoensis Mizutani and Kido, 1983.


Other species.—Canoptum hungaricum Grill and Kozur, 1986; ?Canoptum rudabanyaense Grill and Kozur, 1986; Mizukidella mokaensis new species.


Diagnosis.—Multicyrtid conical to subcylindrical shell.Cephalis dome-shaped without horn. Abdomen and post-abdominal cylindrical segments separated by nodose circumferential ridges, with paired pores just below and above the ridges. Abdomen and post-abdominal chambers have more or less regularly arranged rows of circular pits.


Etymology.—Achronym of parts of Mizutani, Kido, and Dictyomitrella; feminine gender.


Occurrence.—Bajocian to upper Berriasian.


Remarks.—Mizukidella n. gen. is distinguished from other par- vicingulids by having a characteristic surfacewith pits (very small depressions) on the medial part of post-abdominal segments, which are bounded by circumferential ridges and limited by one row of pores below and above. A possible origin fromCanoptum is suspected. Through the latest Jurassic, this genus may have


59


given rise to Svinitzium by the regularization of the size and arrangement of pores and pits around the circumferential ridges.


Mizukidella kamoensis (Mizutani and Kido, 1983) Figure 6.12−6.14


1983 Dictyomitrella (?) kamoensis Mizutani and Kido, p. 258, pl. 53, figs. 2−4b.


2006 Dictyomitrella (?) kamoensis;O’Dogherty et al., p. 435, pl. 3, fig. 15. [See for complete synonymy]


2009 Wrangellium oregonense Yeh; Yeh, p. 59, pl. 17, figs. 13, 22.


2013 Svinitzium kamoense; Chiari et al., fig. 14d.


Mizukidella mokaensis new species Figure 6.26−6.27


1998 Praecaneta ? sp. 6 Matsuoka, pl. 9, fig. 129.


Holotype.—The specimen illustrated on figure 6.27 from sample BMW-35, upper Tithonian of Sillenkopf Formation (Northern Calcareous Alps, Austria).


Diagnosis.—Parvicingulid with very small depressions (pits) arranged linearly on the medial part of post-abdominal segments. A middle row of pores is always present in distal segments.


Occurrence.—Middle Oxfordian to upper Berriasian.


Description.—Shell as with genus having commonly a conical shell with eight segments. Cephalis and thorax poreless, conical, and separated by rows of small pores. Distal segments increase gradually in width. Circumferential ridges strong and bearing vertical bars displaying a typical “H-linked” structure. Each segment has two rows of pits at the ridges and a row of small pores in the middle part. Two rows of bigger pores are always present just above and below the ridges. In well-preserved specimens (e.g., Mariana trench,Matsuoka, 1998, pl. 9, fig. 129), a velum on the distalmost segment may be preserved.


Etymology.—Mokaensis is an anagram of kamoensis, which is the other species included into this genus (see above).


Measurements.—(in micrometers; µm) maximum diameter of conical shell 226−263, mean 240; maximum length 113−119, mean 116, based on three specimens.


Remarks.—Mizukidella mokaensis differs from M. kamoensis by having a more regular shell structure. The pits are linearly arranged, pores are larger, ridges are stronger, and a middle row of pores is always present in distal segments.


Family Xitidae Pessagno, 1977b Genus Xitus Pessagno, 1977b


Type species.—Xitus plenus Pessagno, 1977b.


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