Evolutionary Patterns of Ammonoids: Phenotypic Trends, Convergence, and Parallel Evolution

Ammonoid Septa and Sutures

“…Reconstructing ammonoid phylogeny is hampered by several problems such as covariation between shell parameters as well as between shell shape changes and suture line morphology (Monnet et al 2015). As far as suture line course is concerned, its value for phylogenetic reconstructions has been discussed repeatedly.…”

Ammonoid Intraspecific Variability

“…All intermediates are available between these forms, but the extreme forms appear to be most abundant and the intermediate forms the least abundant. Tintant (1980) suggested that this might indicate polymorphism or even the presence of two species with similar evolutionary trends and convergence in their adult body chambers (compare Monnet et al 2015b). However, Tintant's (1976Tintant's ( , 1980 analyses were preliminary and more detailed analyses of the evolutionary history and intraspecific variability of these groups are necessary to corroborate such hypotheses.…”

“…If no intermediate morphologies are found, it would be more conservative to interpret these as separate taxa, but some authors have argued that such forms should be interpreted as cases of intraspecific polymorphism, when these two groups display parallel, evolutionary changes or trends (Tintant 1980;Atrops and Meléndez 1993) in other characters. Such assertions of evolutionary trends (Monnet et al 2015b) in these characters still have to hold to novel statistical methods which can analytically support the presence of evolutionary trends (Hunt 2006;Monnet et al 2011a) and test how parallel evolutionary (or ontogenetic) trajectories really are Collyer 2009, Collyer andAdams 2013; applied to ammonoids in Monnet et al 2011a;De Baets et al 2013a). Tintant (1963Tintant ( , 1976 has supported his claims not only by the study of numerous populations, but also with the discovery of a pathological macroconch displaying a "Zugokosmoceras" pattern on one side and a "Kosmoceras" pattern on the opposite side.…”

“…Frasnian diversity is based mainly on manticoceratid diversity, which was artificially inflated by taxonomic oversplitting (Korn and Klug 2007). Clearly, analysis of intraspecific variability is a prerequisite for many paleobiological and evolutionary studies (e.g., Monnet et al 2015b), and much more research in this field is needed.…”

Paleobiogeography of Late Cretaceous Ammonoids

“…Ammonoids have variable morphologies Monnet et al 2015). More and more studies show that, when large numbers of specimens of ammonoids with variable ribbing, nodes, and other surface ornament, and to some extent even coiling geometry are looked at anew, many seeming species are found to be only variants.…”