Dinosauria Owen, 1842

Cavalcanti, Ramon, Candeiro, Carlos Roberto dos Anjos, Brusatte, Stephen Louis, Bandeira, Kamila Luisa Nogueira, Oliveira, Emerson Ferreira de, Vidal, Luciano da Silva & Gomes, Musa Maria Nogueira, 2021, First dinosaur record from the Marília Formation (Maastrichtian) in the Gurinhatã municipality, Minas Gerais state, Brazil, Papéis Avulsos de Zoologia 61, pp. 1-8 : 4

Systematic Paleontology Dinosauria Owen, 1842

Saurischia Seeley, 1888 Sauropoda Marsh, 1878 Titanosauriformes Salgado, Coria & Calvo, 1997 Somphospondyli Wilson & Sereno, 1998 Titanosauria Bonaparte & Coria, 1993 Lithostrotia Upchurch, Barrett, & Dodson, 2004 Lithostrotia indet. ( Fig. 3 )

Description

Paleo-UFG/V-0039 is recognized as a proximal fragment of the right ulna, based on its morphology. The bone is thin in its central portion and becomes robust proximally. The distalmost part of the fossil is slightly craniocaudally expanded. In a proximal view, the ulna is triradiate and ‘V’-shaped, a feature observed in other titanosauriforms (Upchurch et al., 2015). The irregular fractures in the most distal portion indicate a post-dia- genetic feature, a taphonomic signature less common for the Marilia Formation titanosaur bones (e.g., Bandeira et al., 2018).

Despite incomplete, this morphology indicates that the bone was genuinely wider at the proximal end and narrowed towards its distal end. The craniomedial and craniolateral processes are prominent ( Fig. 4 ); but, as in other sauropods, the caudal process is much more developed and larger than the former (e.g., Poropat et al., 2015; Upchurch et al., 2015; Ullmann & Lacovara, 2016; González-Riga et al., 2019).

Although this area is not completely preserved, the craniomedial process also is marked by the concave articular surface of the humerus ( Fig. 5 ), while the craniolateral process inclines ventrally, distancing itself from the olecranon, in lateral view ( Fig. 3 ). The caudomedial face exhibits a shallow medial concavity (for insertion of the flexor carpi ulnaris muscle). The ulna shaft is not preserved, but the cross section of the broken distal part of the bone shows that the shaft was subtriangular in this region, due to a caudodistally descending longitudinal crest of the olecranon. The proximal portion of the ascending crest of the olecranon curves slightly medially. In addition, a longitudinal relief ridge defines the medial border of the radial articular face in cranial view.

Figures

Figure 3. An indeterminate lithostrotian sauropod partial right ulna,Paleo-UFG/V-0039,in (A) AnteriorView; (B) Medial View; (C) PosteriorView; (D) Lateral View; (E) ProximalView;(F) Distal view.

Figure 4. Proximal view of different titanosauriforms for comparison. (A) Sonorosaurus (from D’Emic et al., 2016); (B) Wintonotitan (from Poropat et al., 2014); (C) Haestasaurus (from Upchurch et al., 2015);(D)Yongjinglong (from Li et al., 2014);(E) Angolatitan(from Mateus et al., 2011);(F) Atsinganosaurus(from Díez Díaz et al., 2018); (G) Dreadnoughtus (from Ullmann & Lacovara,2014); (H) Rapetosaurus (from Curry Rogers,2009);(I) Neuquensaurus (from Otero,2010);(J) Elaltitan (from Mannion & Otero, 2012); (K) Diamantinasaurus (from Poropat et al., 2015); (L) Malawisaurus (from Gomani, 2005); (M) Lohuecotitan (from Díez Díaz et al., 2016);(N) Mendozasaurus (from González-Rigaet al., 2018);(O) Lirainosaurus (from Díez Díaz et al., 2013);and (P) Paleo-UFG/V-0039.Not in scale.

Figure 5. An indeterminate lithostrotian sauropod partial right ulna, paleo-ufg/v-0039, in (A) anterior view; (B) proximal view; (C) explanatory drawning of the right ulna in anterior view.