Field of Science

Arcusaurus pereirabdalorum, A New Basal Sauropodomorph From The Early Jurassic Of South Africa

Yates, A. M., Bonnan, M. F., and J. Neveling. 2011. A new basal sauropodomorph dinosaur from the Early Jurassic of South Africa. Journal of Vertebrate Paleontology 31:610-625. DOI: 10.1080/02724634.2011.560626

Abstract - A new basal sauropodomorph dinosaur, Arcusaurus pereirabdalorum, sp. nov., is named and described on the basis of a partial, disarticulated but associated skull and dispersed cranial and postcranial elements from at least two individuals. Arcusaurus is part of a distinctive local fauna from the upper Elliot Formation (Lower Jurassic) in the Senekal District, Free State, South Africa. It can be diagnosed by various details of the premaxilla, nasal, and dentary in the skull and the shape of the distal caudal vertebrae. The taxon displays an unusual mix of characteristics. It lacks several synapomorphies of Plateosauria (Plateosaurus + Massospondylus and all descendants of their most recent common ancestor) but does display other derived characteristics that are otherwise known only from less inclusive clades within Plateosauria. In a cladistic analysis a position outside Plateosauria as the sister group of the clade of Efraasia + more-derived sauropodomorphs is supported; however, this position was not found to be a significantly better explanation of the data as a relatively derived position within Plateosauria. If the basal position for Arcusaurus is accepted, then a divergence from other sauropodomorphs in the middle Norian and a ghost lineage up to 35 Ma is implied. No other non-plateosaurian sauropodomorphs are known from the Jurassic, making Arcusaurus a potentially relictual taxon in the Early Jurassic.

8 comments:

  1. Arcusaurus is a new genus, they did a mistake by not writing "GEN. ET sp. nov"

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  2. Oops, dammit you are right, how did THAT slip by? At least is is gen. et sp. nov. in the Systematic Paleontology where it really counts.

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  3. I didnt mean to be mean, it just that i was a bit confused when i saw the abstract on informaworld (i dont unfortunately have access to anything) and spent almost 30 minutes looking for the "supposed type" species of Arcusaurus in internet, just for realizing it doesnt exist

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  4. Seems like new basal sauropodomorphs are popping up all over the place in the last few years. One wonders if this reflects an actual explosion in diversity (back in the Jurassic) or we just haven't been as lucky with other groups.

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  5. Does Arcusaurus have any effect on the following synonyms of Massospondylus: Pachyspondylus, Leptospondylus, Hortalotarsus, Gyposaurus, Gryponyx, Aristosaurus, Aetonyx, Dromicosaurus? How does Arcusaurus compare to Ignavusaurus?

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  6. Arcusaurus means Rainbow Reptile, right? Like in Rainbow Nation? But I don't get the "pereirabdalorum" part. Those are two people? Did they find the fossil?

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  7. @Dinogirl -- that species name was at my insistence ... the two combined last names of the student and postdoc who actually unearthed the specimen.

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  8. A question for Adam and Matt: I haven't had a chance to read the paper yet, but what's the chance that Arcusaurus and Ignavusaurus are the same taxon? Both are gracile taxa from the upper Elliot that are fairly basal phylogenetically between Saturnalia and Efraasia.

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