Cryptotretidae Pelman, 1979

Skovsted, Christian B., Kouchinsky, Artem, Bengtson, Stefan & Holmer, Lars E., 2014, The problematic early Cambrian fossil Tumulduria incomperta represents the detached ventral interarea of a paterinid brachiopod, Acta Palaeontologica Polonica 59 (2), pp. 359-365 : 362-363

Family Cryptotretidae Pelman, 1979 Genus Tumulduria Missarzhevsky in Rozanov et al., 1969

Type species: Tumulduria incomperta Missarzhevsky in Rozanov et al., 1969 from the Nochoroicyathus sunnaginicus Zone, Tommotian Stage, Cambrian Series 2, of the Aldan River area, southeastern Siberian Platform.

Emeded diagnosis.—Ventral valve with orthocline, flat, triangular interarea with a narrow pseudodeltidium. Interarea with low, transverse ribs and furrows and oblique, poorly developed flexure lines. Dorsal valve flat or slightly convex and gently sulcate. Catacline dorsal interarea reduced and developed as a low elongate ridge along the posterior margin; dorsal triangular notothyrium open.

Tumulduria differs from Aldanotreta Pelman, 1977 , Dzunarzina Ushatinskaya, 1993 , and Askepasma Laurie, 1986 in having an orthocline, triangular ventral interarea with a

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narrow pseudodeltidium and a low ridge-like dorsal interarea. It differs from Cryptotreta Pelman, 1977 in having more irregular transverse ornament on the ventral interarea and an open triangular notothyrium lacking a chilidium. It differs from Salanygolina Ushatinskaya, 1987 in its more strongly sulcate dorsal shell, small dorsal interarea with open notothyrium and in lacking the pustulose adult microornament.

Discussion.—The rationale behind the reinterpretation of Tumulduria incomperta as a paterinid brachiopod is outlined above. Based on the shared presence of an orthocline ventral interarea with a pseudodeltidium and an inferred foramen anterior to the umbo, Tumulduria is likely to be closely related to Cryptotreta from the Siberian Platform and Salanygolina from the lower Cambrian of Mongolia. The relationship of Tumulduria to other genera included in the Cryptotretidae is less clear.

Geographic and stratigraphic range.— Tumulduria is known from the Nochoroicyathus sunnaginicus Zone, Tommotian Stage (Terreneuvian Series, Cambrian Stage 2), southeastern Siberian Platform, from sections along the Aldan River and from the Uchur-Maya region representing the transitional facies belt ( Rozanov et al. 1969; Khomentovsky et al. 1990; Rozanov and Zhuravlev 1992; Khomentovsky and Karlova 2005).