首页|Convergent evolution in planktic graptolites: independent origin of the dicranograptid morphology in the Hirnantian (latest Ordovician)
Convergent evolution in planktic graptolites: independent origin of the dicranograptid morphology in the Hirnantian (latest Ordovician)
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NSTL
Taylor & Francis
A new genus and species of planktic graptolite, Anjigraptus wangi gen. et sp. nov., is described from the Upper Ordovician (Hirnantian) sponge-dominated Anji Biota of Zhejiang Province, China. The new genus has a biserial proximal portion and two uniserial stipes distally, the same tubarium form as Dicranograptus. The new genus has probable pattern H development and lacks introverted thecae; it can thus be readily distinguished from the biostratigraphically important Late Ordovician graptolite Dicranograptus, the Late Ordovician Diceratograptus, and the Ordovician-Silurian Neodicellograptus. As Anjigraptus wangi gen. et sp. nov. appears to lack a nema in its uniserial portions and can be distinguished from all other biserial graptolites in the same assemblage, we conclude that the new taxon is not a teratomorphic form of a previously known species, but represents convergent evolution of the dicranograptid morphology. The holotypes of two species of Neodicellograptus (N. siluricus and N. spinosus) are re illustrated.
NSTL
Taylor & Francis
