Nicollidina, Dzik, 2002

Dzik, Jerzy, 2002, Emergence and collapse of the Frasnian conodont and ammonoid communities in the Holy Cross Mountains, Poland, Acta Palaeontologica Polonica 47 (4), pp. 565-650 : 602-603

Genus Nicollidina nov.

Type species: Spathognathodus brevis Bischoff and Ziegler, 1957 .

Derivation of the name: In honour of Robert S. Nicoll, who restored the apparatus of the type species.

Diagnosis.—Minute elements with reduced medial process in S 0 (tr) element and shortened processes in S 1 (lo) and S 2 (pl) elements which still preserved linear arrangement.

Remarks.—Species included here in this new genus were previously classified in Ozarkodina Branson and Mehl, 1933 , the type species of which is a Silurian primitive ozarkodinid with biramous S 0 (tr) elements. Its lineage probably survived to the late Palaeozoic ( Dzik 1991b) being represented there by species of Hindeodus Rexroad and Furnish, 1964 and Synclydagnathus Rexroad and Varker, 1992 (misspelled Syncladognathus in Dzik 1997). They all show angular profiles of bases of S 0 (tr), S 1 (lo) and S 2 (pl) elements, unlike N. brevis . In the latter, the ramiform elements of the apparatus look rather like early juvenile elements of typical polygnathids. Most likely, evolutionary diminution in size resulted in a secondary reduction of the medial process of the S 0 element. Nicollidina gen. nov. is thus a secondarily simplified member of the Polygnathidae , not the Spathognathodontidae sensu Dzik 1991b . This is not a unique case. Similar evolutionary transformations took probably place in the evolution of the early Carboniferous Siphonodella ( Dzik 1997) .

Species included.—Along with type species also N. raaschi ( Klapper and Barrick, 1983) and N. postera ( Klapper and Lane, 1985) .

Distribution.—Eifelian to Frasnian ( Klapper and Barrick 1983; Nicoll 1985; Klapper and Lane 1985; Racki 1992).