Re: [dinosaur] Adratiklit, new stegosaur from Middle Jurassic of Morocco

[Tim Williams <tijawi@gmail.com>]

Not to take anything away from _Adratiklit_, the first North African stegosaur, but the claim that it's "the oldest definitive stegosaur from anywhere in the world" depends on whether or not _Isaberrysaura_ is a stegosaur. Maidment &c's own phylogenetic analyses (MPTs) recover _Isaberrysaura_ as a basal stegosaur (not the first study to show this, as they note). Their basal _Isaberrysaura_-_Gigantspinosaurus_ clade actually has more support than their _Adratiklit_-_Dacentrurus_-_Miragaia_ clade (Figure 12). Nevertheless, Maidment &c don't seem particularly convinced that Isaberrysaura_ is a definitive stegosaur ("however, further study and a postcranial description of the skeleton, are needed to elucidate the taxonomic status of the specimen."), which is fair enough.

Regarding Gondwanan stegosaurs, from the Discussion: "The vast majority of eurypodan taxa so far recognized have been described from Laurasia, with just three stegosaurs (_Isaberrysaura_, _Kentrosaurus_, _Paranthodon_) and two ankylosaurs (_Antarctopelta_, _Kunbarrasaurus_) being known from Gondwanan continents throughout the entire Mesozoic (Fig. 14). The discovery of _Adratiklit_ in Africa therefore adds significantly to the known diversity of Gondwanan eurypodans."

Poor _Minmi_ is not included in this list of Gondwanan ankylosaurs. Instead, _Kunburrasaurus_ is regarded as the sole valid ankylosaur from Australia. This is no doubt following Arbour & Currie (2016), who regarded _Minmi_ as a nomen dubium; but Arbour & Currie (2016) regarded _Antarctopelta_ as a nomen dubium as well. (Arbour & Currie, 2016, were quite brutal when it came to assessing the validity of ankylosaur taxa.) Leahey et al. (2016) re-asserted that _Minmi_ is a valid and distinct genus, and I wouldn't write off _Minmi_ quite yet (or the family Minmiidae, as a clade of basal ankylosaurs).

Also, Galton & Ayyasami (2017) are pretty convinced that there are stegosaur remains (_Dravidosaurus_ ?), from India (Coniacian); but without the promised re-description, I can see why Maidment &c are keeping an open mind.

On Sat, Aug 17, 2019 at 2:03 PM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler

bcreisler@gmail.com

A new paper:

Adratiklit boulahfa gen. et sp. nov.

Susannah C. R. Maidment, Thomas J. Raven, Driss Ouarhache & Paul M. Barret (2019)
North Africa's first stegosaur: Implications for Gondwanan thyreophoran dinosaur diversity.
Gondwana Research (advance online publication)
doi: https://doi.org/10.1016/j.gr.2019.07.007
https://www.sciencedirect.com/science/article/pii/S1342937X19302217

Highlights

Adratiklit boulahfa is a new genus of stegosaur from Morocco.
Adratiklit is the oldest definitive stegosaur and the first from north Africa.
It is closely related to the European stegosaurs Dacentrurus and Mirigaia.
The dinosaur fossil record of Gondwana is biased.
Armoured dinosaurs may have been as diverse in Gondwana as they were in Laurasia.


Abstract

Eurypoda, the major radiation of armoured dinosaurs, comprises the ankylosaurs and their sister group, the stegosaurs. As the earliest-branching major clade of ornithischian dinosaurs, the evolutionary history of Eurypoda is significant for understanding both the palaeobiology of bird-hipped dinosaurs and the composition of middle Mesozoic ecosystems. Eurypodans were diverse and abundant throughout the Late Jurassic and Cretaceous in Laurasia; in contrast, their remains are extremely rare in Gondwana. Herein, we describe a new genus and species of stegosaur from the Middle Jurassic of Morocco, Adratiklit boulahfa. Adratiklit is the first eurypodan from north Africa and the oldest definitive stegosaur from anywhere in the world. The genus is more closely related to the European stegosaurs Dacentrurus and Miragaia than it is to the southern African taxa Kentrosaurus and Paranthodon. Statistically significant correlations between the number of dinosaur-bearing formations, dinosaur-bearing collections, and eurypodan occurrences in Gondwana indicates that their fossil record is biased by both geological and anthropogenic factors. Tantalizing but fragmentary remains and trackways suggest that eurypodan diversity in Gondwana may have been as rich as that of Laurasia, and the prospects for future discoveries of new genera across Gondwana are therefore very good.

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