Talk:Carcinosomatoidea

Status of Megalograptidae

Ichthyovenator, I am in doubt about whether the megalograptids are really separated into a different superfamily or are in Carcinosomatoidea. In the description of Diploperculata, Lamsdell et al. declare that Megalograptus is definitely a diploperculate and places it in the same group as Carcinosoma and Mixopterus in its cladogram. In the Systematic paleontology section of the description of Pentecopterus, Lamsdell et al. classified Megalograptidae as part of Carcinosomatoidea, without mention of Megalograptoidea. It looks like the arachnid summary is based on Tetlie (2007), which placed the megalograptids with doubt, stating that Megalograptoidea has never been recovered in a phylogenetic analysis. I am also beginning to doubt the validity of Merostomata, since more recent studies classify the eurypterids in "Sclerophorata", but this will be discussed later. I think it would be better to redirect Megalograptoidea to Carcinosomatoidea, but I would like to know your opinion about this. Super Ψ Dro 21:09, 15 September 2018 (UTC)

I'm going to have to read up on this but I thought that the Megalograptids were pretty well accepted as a primitive group of eurypterine eurypterids (being Ordovician and all). "Megalograptoidea" might very well be invalid but let's not be too quick to make massive edits here. Ichthyovenator (talk) 22:30, 15 September 2018 (UTC)

Reading the sources you use it does seem that (1) "Megalograptoidea" has never been recovered as a valid phylogenetic group and its position as primitive is based on a few inferred traits, (2) the position of the Megalograptidae tends to shift between primitive or close to either Eurypteroidea or "Mixopteroidea" (e.g. Carcinosomatoidea) from analysis to analysis and (3) the megalograptids are clearly diploperculate. In addition to this we have several papers classifying Megalograptidae within Carcinosomatoidea. Also, Holmipterus seems to share characteristics of both Megalograptidae and Carcinosomatidae which would not be surprising if both groups were closely related. So yes, I'm redirecting Megalograptoidea to Carcinosomatoidea and making the necessary edits elsewhere as well. Thanks for bringing this to light!

As for Merostomata and Sclerophorata, the individual eurypterid articles on the genus, family, superfamily or even suborder level do not really discuss how eurypterids relate to other arthropod groups so this is only really relevant for the main Eurypterid article I think but definitely something that should be discussed in it. Ichthyovenator (talk) 09:48, 16 September 2018 (UTC)

Thanks for taking care of the changes! Now Eurypterina seems a bit empty, I had become accustomed to Megalograptoidea... Soon I will open a thread in Chelicerata about Sclerophorata and the other new clades, you can participate if you wish. Super Ψ Dro 10:15, 16 September 2018 (UTC)