Hello fellow graptolite workers,

I'm having a little bit of difficulty in distinguishing between Stimulograptus sedgwickii (Portlock, 1843) and Stimulograptus halli (Barrande, 1850), and to some degree with Campograptus lobiferus (Mc'Coy, 1850) as well. What is the best way to distinguish between these species - are there any new re-definition or diagnostic that could help?

Also, in Zalasiewicz et al. (2009) in the section discussing the St. sedgwickii Biozone, the study noted how the suggestion of earlier appearance of St. sedgwickii have not been substantiated. Can someone clarify for me on this?

Thank you so much.