A new phylogeny of Stegosauria (Dinosauria, Ornithischia)

Abstract

The stegosaurs are some of the most easily recognisable dinosaurs, but they are surprisingly rare as fossils. Consequently much remains unknown about their palaeobiology, and every new stegosaurian find contr ibutes to understanding the evolution of the clade. Since the last attempt to examine the evolutionary relationships of Stegosauria, new specimens have come to light, including the most complete individual of Stegosaurus ever found, new taxa have been desc ribed and, perhaps most importantly, new methods for analysis of cladistic datasets have been produced. In the light of these new data and technological advances, the phylogenetic relationships of the stegosaurs and basal armoured dinosaurs are investigate d. The inclusion of continuous data results in much better resolution than was previously obtained, and the resulting single most parsimonious tree supports re - erection of the genera Miragaia and Hesperosaurus , which had previously been synonymized with Dacentrurus and Stegosaurus respectively. The recently described genus Alcovasaurus is resolved as a basal thyreophoran, but this is likely to be due to a combination of a very high degree of missing data and the questionable ontogenetic stage of the speci men. Examination of the effects of continuous data on the analysis suggest that while it contains a phylogenetic signal congruent with that of discrete data and provides better resolution than discrete data alone, it can affect t opologies in unpredictable ways, particularly in areas of the tree where there are large amounts of missing data. The phylogeny presented here will form the basis for future work on the palaeobiology of the plated dinosaurs

Peer Review #2 of "The systematic position of the enigmatic thyreophoran dinosaur Paranthodon africanus, and the use of basal exemplifiers in phylogenetic analysis (v0.1)"

“…The most recent phylogeny of Stegosauria by Raven and Maidment (2017) showed Paranthodon and Tuojiangosaurus to clade together, a result that was found again here in the one most parsimonious tree of length 279.65 (Analysis E1). Isaberrysaura, the Argentinian dinosaur found as a neornithischian by Salgado et al (2017), was then found in a sister-taxon relationship with Gigantspinosaurus (Analysis E2).…”

“…Analysis D6 resulted in Isaberrysaura being found as a basal neornithischian, along with Paranthodon and the unambiguous stegosaurs Huayangosaurus and Stegosaurus. This surprising result is an artefact of the character distribution of the Boyd (2015) dataset; there are only seven characters that unite either Eurypoda, Eurypoda + Alcovasaurus, or Stegosauria in the Raven and Maidment (2017) dataset that are found in the Boyd 2015 is almost certainly due to the fact that the dataset of Boyd (2015) does not contain the character data required to rigorously test the phylogenetic position of taxa which may be derived members of clades. It is therefore likely that, as found by Han et al (2017), Isaberrysaura is a member of the Thyreophora.…”

“…In Analysis E1, the character list of Raven and Maidment (2017) was updated following a more thorough description of Paranthodon and character scorings were updated to include the dorsal vertebra. Pisanosaurus was used as the outgroup taxon and, as in the original analysis, the 24 continuous characters were ordered, as were the discrete characters 34, 111 and 112.…”

“…6). The most recent phylogeny of Stegosauria byRaven and Maidment (2017) was updated with new characters and character-PeerJ reviewing PDF | (2017:12:22703:1:1:NEW 28 Feb 2018)…”

The systematic position of the enigmatic thyreophoran dinosaur Paranthodon africanus, and the use of basal exemplifiers in phylogenetic analysis

“…The original analysis performed safe taxonomic reduction using TAXEQ3 (Wilkinson, 2001) to remove the taxa Bissektipelta archibaldi, Minmi paravertebra and Tianchisaurus nedegoapeferima, and so these taxa were also removed from all analyses here. The original analysis was repeated here, using the basal stegosaur Huayangosaurus as the exemplifier for Stegosauria, to ensure Baron, Norman & Barrett (2017); (E) stegosaurian phylogeny by Raven & Maidment (2017); (F) ankylosaurid phylogeny by Arbour & Currie (2016).…”