Cyrtonellida HORNÝ , 1963

Horný, Radvan J., 2009, Patelliconus Horný, 1961 And Mytoconula Gen. N. (Mollusca, Tergomya) From The Ordovician Of Perunica, Acta Musei Nationalis Pragae Series B 65 (1 - 2), pp. 25-36 : 26

Order Cyrtonellida HORNÝ, 1963

Family Protoconchoididae GEYER, 1994 (orthographic variant, ex Protoconchioididae; = Patelliconidae FRÝDA, 1998 )

D i s c u s s i o n: The genus Patelliconus HORNÝ, 1961 was originally placed in the family Hypseloconidae KNIGHT, 1956 ( Horný 1961, 1963). Yochelson (1977) reported Patelliconus as a monoplacophoran of the family Hypseloconidae from the Ordovician of Norway. For the genus Protoconchoides SHAW, 1962 a separate family was established, Protoconchoididae , by Geyer, 1994 (spelled as Protoconchioididae)and located within the order Tryblidiida LEMCHE, 1957 . In 2002, Horný listed Patelliconus , although tentatively, as a gastropod under the family Archinacellidae KNIGHT, 1956 or?Protoconchioididae GEYER, 1994. The family Protoconchoididae is transferred here to the order Cyrtonellida HORNÝ, 1963 , which has priority over the order Kirengellida ROZOV, 1975 (see Peel 1991). Thus the superficially similar genus Kirengella ROZOV, 1968 , reported by several authors from Cambrian to Ordovician strata (e.g. by Doguzhaeva 1972, 1981, Rozov 1975, Stinchcomb 1986, Webers, Pojeta Jr., and Yochelson 1992, Geyer 1994, Stinchcomb and Angeli 2002) belongs in the same order. Unfortunately, the majority of the described species of Kirengella lack shells and their muscle scars are rare, poorly preserved or unknown. As already noted by Horný (2006a), the family Kirengellidae STAROBOGATOV, 1970 requires a detailed study of better preserved specimens and critically defined genera. An important criterion could be either presence of a muscle zone consisting of more or less equivalent muscle scars or coalesced muscle scars in a continuous band-like ring. This complicated situation can be illustrated by the well-known specimen of Rasetti´s Scenella sp. undet. (1954), tentatively assigned to Protoconchoides by Geyer (1994) as Protoconchioides? rasettii n. sp., and reinterpret- ed by Peel (1991) as a helcionellid.

Frýda (1998) established a new family Patelliconidae of unceratin class affinity, based on Patelliconus HORNÝ, 1961 and containing, besides Patelliconus , a Lower Devonian genus Chuchleconus FRÝDA, 1998 . Because the shell morphology and musculature of Protoconchoides SHAW, 1962 and Patelliconus HORNÝ, 1961 are almost identical, the family Patelliconidae is here synonymized with the family Protoconchoididae Geyer, 1994 .

I n c l u d e d g e n e r a: Patelliconus HORNÝ, 1961 ; Protoconchoides SHAW, 1962 ; Chuchleconus FRÝDA, 1998 ; Mytoconula gen. n.

D i s t r i b u t i o n: middle Cambrian; Ordovician; Lower

Devonian.