| Abstract: | Internal structure of Stenopopanoceras mirabilePopow, Parapopanoceras sp., P. mediumMcLearn, P. janaense (Popow), P. paniculatumPopow, P. asseretoiDagys & Ermakova, Indigirites krugiPopow, Nathorstites mcconnelli (Whiteaves), N. gibbosusStolley, N. lenticularis (Whiteaves), N. argatassensis (Popow) is described and also ontogenetic development of species I. krugiPopow and N. mcconnelli (Whiteaves) originating from middle triassic deposits of northern part of Middle Siberia, north-eastern part of the USSR and Svalbard is given. For the species mentioned above data is given on the position of siphuncle, shape and dimensions of protoconch, caecum, ammonitella, the angle of primary varix, structure of septal necks and the nature of their change in the course of ontogeny. Significance of these signs for taxonomy and phylogeny of triassic ammonoidea is analysed. Intergeneric difference of Stenopopanoceras and Parapopanoceras is established according to the position of siphuncle on the first whorl of the shell. On the basis of the analysis of internal structure and ontogenetic development of suture line and morphological signs Indigirites is considered to belong to the family Hungaritidae (subfamily Longobarditinae). Phylogenetic patterns of the ammonoidea species described are discussed. |
