Article: The Ordovician graptolites Azygograptus and Jishougraptus in Scandinavia and Britain
Two groups within Azygograptus are identified on the presence or absence of adpressed growth of th 11(superscript) along the sicula. The second group has an unusual facies association and this is interpreted to reflect adaptation to a shoreward, and possibly r-selective environment. Adaptation to such an environment is argued to have the potential to affect proximal development and consequently the evolutionary origins of this group are obscure. The subgenera previously erected are not used because of difficulties with the type species. Features of the proximal development are the main characters used to distinguish the species, and all the previously named Scandinavian and British species are redescribed except for A. coelebs for which no reliable specimens can be found. Three new species are described, Azygograptus minutus, Jishougraptus novus and J. lindholmae. Jishougraptus is recognized for the first time outside China, and the first specimens of Azygograptus from South America are illustrated.