. Bulletins of American paleontology. 248 Bulletin 256. Text-fig. 7. — Adult septal suture of Strp/iaiioccras (Stcphanoccras) aif. S. humphricsianum (J. de C. Sovverby), at approximately 10 cm diameter, from Kemaboe Valley ( Leiden, st. 126191). confusion and grossly 'split' at the genus-group and species levels (Westeimann, 1964, p. 66 ff). Experience on several continents suggests that a small fraction (10-20 per cent) of the taxa would suffice. The 'planulate' S. JiumpJniesianiim, type species, almost certainly intergrades with the more inflated and involute and also more common 'plex
. Bulletins of American paleontology. 248 Bulletin 256. Text-fig. 7. — Adult septal suture of Strp/iaiioccras (Stcphanoccras) aif. S. humphricsianum (J. de C. Sovverby), at approximately 10 cm diameter, from Kemaboe Valley ( Leiden, st. 126191). confusion and grossly 'split' at the genus-group and species levels (Westeimann, 1964, p. 66 ff). Experience on several continents suggests that a small fraction (10-20 per cent) of the taxa would suffice. The 'planulate' S. JiumpJniesianiim, type species, almost certainly intergrades with the more inflated and involute and also more common 'plexus' of S. iimbilicum and S. rniitabile, Quen- stedt spp., [^ ? 5. brodiaei (J. Sowerby) ] all of which are usually associated; this group is characterized by moderately fast increasing, rounded subelliptical whorls with fine costae bearing tubercles. To this 'plexus' belongs also the northeastern Pacific S. cnamanoi (McLearn) from the .S'. JiinnpJiriesianwn Zone of Queen Charlotte Islands; it is generally restricted to the .S'. huinpJiriesinnnin Zone and derived from the 'serpenticone' but otherwise similar subgenus S. (Skirroceras) of the O. saiizei Zone. Stemmatoceras Mascke is difficult to separate and distinguished only by the more strongly de- pressed sublenticular whorls with well-defined lateral edge and more prominent primaries or bullae; however, there is intergrada- tion of probably interrelated features, intraspecifically as well as morphogenetically, with Slephanoceras s-s. on the one hand and Teloceras Mascke on the other, the latter becoming distinct usually only if large and fully grown. Consecjuently, Stemmatoceras and Teloceras are best distinguished from Slephanoceras at the subgen- eric level only. In the northeastern Pacific area, the Stemmatoceras- Teloceras complex of a single bed (Rock Creek Member) in the S. humphriesiaymm Zone of Alberta, for example, has been divid- ed into 12 (macroconchiate) 'species' comprising an apparently. Please note that
Size: 2604px × 959px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpaleontologicalresearchinstitutionit, bookcentury1900
