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. 2012 Dec 5;9(1):20120949.
doi: 10.1098/rsbl.2012.0949. Print 2013 Feb 23.

The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania

Sterling J Nesbitt  1 , Paul M Barrett, Sarah Werning, Christian A Sidor, Alan J Charig
Affiliations

The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania

Sterling J Nesbitt et al. Biol Lett. .

Abstract

The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister-taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria.

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Figures

Figure 1.
Figure 1.
Holotype (a–h; NHMUK R6856) and referred (i–j; SAM-PK-K10654) specimens of Nyasasaurus parringtoni gen. et sp. nov. Right humerus in (a) anterior and (b) posterior views. Histological section of humerus in (c) complete cross-section in transmitted light, (d) cross-section through the entire cortex in crossed Nicols, and (e) cross-section through the outer portion of cortex in crossed Nicols. (f) Rearticulated sacrum in right lateral view with interpretive drawing (below). (g) Posterior presacral vertebra in right lateral view. (h) Partial posterior presacral vertebra in dorsal view. (i) Anterior cervical vertebra in left lateral view with interpretive drawing (below). (j) Anterior cervical vertebra in left lateral view with interpretive drawing (below). Arrows point anteriorly. Scale bars, (a,b,f–j) 1 cm, (c) 4 mm, (d) 1 mm, (e) 500 nm. Dep, depression; df, deep fossa; dia, diapophysis; dp, deltopectoral crest; epi, epipophysis; hs, histology section; hyp, hypantrum; no, notch; ns, neural spine; par, parapophysis; pre, prezygapophysis; pz, postzygapophysis; r, ridge; s1–3, sacral vertebra number; sr1–3, sacral rib number; st, striations.
Figure 2.
Figure 2.
Possible phylogenetic position of Nyasasaurus parringtoni gen. et sp. nov. as either within, or the sister-taxon of, Dinosauria (indicated by the medium grey box), illustrating the decrease in the dinosaurian ghost lineage. Dashed bars represent uncertainty. In, Induan; Olen, Olenekian.
See this image and copyright information in PMC

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