Baurutitan britoi Kellner, Campos & Trotta, 2005

Silva Junior, Julian C. G., Martinelli, Agustín G., Marinho, Thiago S., da Silva, João Ismael & Langer, Max C., 2022, New specimens of Baurutitan britoi and a taxonomic reassessment of the titanosaur dinosaur fauna (Sauropoda) from the Serra da Galga Formation (Late Cretaceous) of Brazil, PeerJ (e 14333) 10, pp. 1-44 : 31-35

Baurutitan britoi Kellner, Campos & Trotta, 2005

Syn. Trigonosaurus pricei Campos et al., 2005 (a complete list of synonyms is provided on the supplementary)

Type-species: Baurutitan britoi Kellner, Campos & Trotta, 2005

Holotype: MCT 1490-R (Series C): last sacral vertebra articulated with a sequence of eighteen caudal vertebrae.

Referred specimens: MCT 1488-R (Series B; holotype of T. pricei ): five cervical and 10 trunk vertebrae; sacrum and ilium. Forty-four specimens, possibly constituting a single individual, recovered from BR-262 locality, including: CPPLIP-035 (middle cervical vertebrae), CPPLIP-039 (middle cervical vertebrae), CPPLIP-040 (posterior cervical vertebrae), CPPLIP-049 (posterior cervical vertebrae), CPPLIP-014 (cervical rib), CPPLIP- 110 (anterior trunk vertebra), CPPLIP-036 (anterior trunk vertebra), CPPLIP-103 (middle trunk vertebra), CPPLIP-111 (middle trunk vertebra), CPPLIP-037 (middle trunk vertebrae), CPPLIP-458 (middle trunk vertebrae), CPPLIP-43 (posterior trunk neural spine), CPPLIP-044 (trunk rib fragment), CPPLIP-097 (trunk rib fragment), CPPLIP-108 (trunk rib fragment), CPPLIP-109 (trunk rib fragment), CPPLIP-102 (anterior caudal vertebra), CPPLIP-046 (middle caudal vertebra), CPPLIP-047 (middle caudal vertebra), CPPLIP-061 (middle caudal vertebra), CPPLIP-096 (middle caudal vertebra), CPPLIP-091 (posterior caudal vertebra), CPPLIP-093 (middle caudal vertebra), CPPLIP-094 (posterior caudal vertebra), CPPLIP-095 (posterior caudal vertebra), CPPLIP-045 (posterior caudal vertebra), CPPLIP-055 (anterior chevron), CPPLIP-056 (anterior chevron), CPPLIP-098 (anterior chevron), CPPLIP-099 (anterior chevron), CPPLIP-112 (anterior chevron), CPPLIP-188 (anterior chevron), CPPLIP-057 (posterior chevron), CPPLIP-100 (posterior chevron), CPPLIP-038 (right scapula), CPPLIP-140 (right coracoid), CPPLIP-138 (right sternal plate), CPPLIP-007 (fragment of left humerus), CPPLIP-008 (right humerus), CPPLIP-010 (right metacarpal I), CPPLIP-042 (left ischium fragment), CPPLIP-069 (right ischium), CPPLIP-011 (left metatarsal II), CPPLIP-054 (left metatarsal III).

Type-locality and horizon: MCT 1490-R was collected from the Serra da Galga Formation ( Soares et al., 2021), in the site known as “Caieira”, “Quarry 1”, or “Ponto 1 do Price”, Serra do Veadinho area, near Peirópolis, Uberaba-MG ( Campos & Kellner, 1999; Martinelli & Teixeira, 2015).

Revised diagnosis: titanosaur diagnosed based on a set of autapomorphic features, i.e.: expanded postzygodiapophyseal laminae on mid-posterior cervical vertebrae (newly proposed here) and first caudal vertebra with strongly pointed and laterally directed processes intercepting the spinoprezygapophyseal lamina ( Kellner, Campos & Trotta, 2005).

Reassessment of MCT 1719-R

The redefinition of the specimens referred to Ba. britoi implies that MCT 1719-R cannot be associated to that taxon, as these caudal vertebrae clearly differ from those of MCT 1490-R and the BR-262 specimens. As discussed above, the BR-262 caudal neural spines lean posteriorly, as also seen in Ba. britoi ( Kellner, Campos & Trotta, 2005, figs. 8, 12, 16 and 19), but not in MCT 1719-R, the spines of which lean gently anteriorly or stand nearly vertical ( Figs. 21 , 22 ). MCT 1719-R also lacks another trait shared between Ba. britoi and the BR-262 specimens: transverse processes that turn into a lateral ridge on the middle of the series. Below, we further revise the features of MCT 1719-R that Campos et al. (2005) used to diagnose T. pricei .

Campos et al. (2005) proposed that the centra of the anterior tail vertebrae possess thin ventral margins that broaden towards the top and transverse processes with pronounced dorsal depressions, two in the anterior (2–5) and one in the middle caudal vertebrae.

The 2 nd caudal vertebra possesses a deep muscular scar on its lateral face, followed by centra with lateral faces more deeply excavated than those at a similar serial position in Gondwanatitan faustoi ( Kellner & Azevedo, 1999; fig. 6), Panamericansaurus schroederi ( Porfiri & Calvo, 2010; fig. 3), and U. ribeiroi ( Silva Junior et al., 2022; fig. 10). Also, anteriorly extended caudal prezygapophyses, with wide (dorsoventrally expanded) articular faces, are unique to MCT 1719-R among titanosaurs from the Serra da Galga Formation. These are about 70% the centrum length in middle caudal vertebrae, a proportion similar to that found on some Aeolosaurini, such as Aeolosaurus rionegrinus (72%; Powell, 1987) and Arrudatitan maximus (76%; Santucci & Arruda-Campos, 2011). The latter also shares wide articular facets ( Santucci & Arruda-Campos, 2011; fig. 4) with MCT 1719-R, as well as with Punatitan coughlini ( Hechenleitner et al., 2020) .

As mentioned by Campos et al. (2005), MCT 1719-R has articular surfaces for the haemal arches that are strongly developed from the third caudal vertebra until the last preserved element (20 th caudal vertebra). Although suggested as a unique feature of MCT 1719-R, a similar condition is present in Rocasaurus muniozi ( Salgado & Azpilicueta, 2000; figs. 6 and 8) and U. ribeiroi ( Silva Junior et al., 2022; fig. 10). Finally, the presence of well-developed transverse processes along the anterior and middle (1–20) caudal vertebrae was also proposed as unique to MCT 1719-R ( Campos et al., 2005). In fact, some other titanosaurs— e.g., Ar. maximus ( Santucci & Arruda-Campos, 2011; fig. 4) and U. ribeiroi ( Silva Junior et al., 2022; fig. 9)—possess transverse processes as long as those of MCT 1719-R ( Figs. 21 and 22 ), almost reaching the posterior margin of the condyles, although less developed in more posterior vertebrae. Yet, those of MCT 1719-R are unique because they are strongly expanded dorsoventrally, to almost half the centrum height, including those of middle caudal vertebrae. As for the persistence of the transverse processes minimally until the twentieth caudal vertebra; this feature is also present in Overosaurus paradosorum ( Coria et al., 2013; fig. 6) and P. coughlini ( Hechenleitner et al., 2020; fig. 2).

Our comparative review has shown the presence of yet another unique feature of MCT 1719-R: the presence of deep postzygapophyseal-centrodiapophyseal fossae, expanding anteromedially on the dorsal margin of the neural arch ( Figs. 21 , 22 ). This condition differs from that of other titanosaurs, in which this fossa is present but does not expand medially, as for instance in Ba. britoi ( Fig. 20D : Kellner, Campos & Trotta, 2005; fig. 18), U. ribeiroi ( Silva Junior et al., 2019; fig. 9), and the BR-262 specimens. Awell-developed postzygapophyseal-centrodiapophyseal fossa is also present in Adamantisaurus mezzalirai ( Santucci & Bertini, 2006; plate 1), but restricted to the most anterior vertebrae and not as deep as in MCT 1719-R. Deep postzygapophyseal-centrodiapophyseal fossae are also present in Narambuenatitan palomoi ( Filippi, García & Garrido, 2011; fig. 8) and Mendozasaurus neguyelap ( González Riga et al., 2018; fig. 9), although these are dorsoventrally expanded in the former, reaching the neural canal, and limited medially by a centropostzygapophyseal lamina in the latter.

In conclusion, the uniqueness of MCT 1719-R among Bauru Group and other South American titanosaurs, including the presence of autapomorphic features (see below), warrants the proposition of a new taxon to accommodate the specimen.

Figures

Figure 20 Caudal elements of Baurutitan britoi and BR-262 specimens. (A) Anterior caudal vertebra of BR-262 specimens in left lateral and dorsal views.(B) Anterior caudal vertebra of B. britoi in left lateral and dorsal views. (C) Mid-posterior caudal vertebrae of BR-262 specimens in left lateral views. (D) Mid-posterior caudal vertebrae of B. britoi in left lateral views. (E) Chevrons of BR-262 specimens in anterior view. (F) Chevrons of B. britoi in anterior view. Abbreviations: alc, anterolateral projecting crest; hc, haemal canal; ns, neural spines; sprl, spinoprezygapophyseal lamina; tp, transverse process. Scale for anterior vertebrae: 20 cm; scale for mid-posterior vertebrae: 15 cm; scale for chevrons: 10 cm. Full-size DOI: 10.7717/peerj.14333/fig-20

Figure 21 Anterior caudal vertebrae of Caieiria allocaudata (MCT 1719-R). In (1) left lateral; (2) anterior; (3) dorsal; (4) right lateral; (5) posterior and (6) ventral views. Abbreviations: ns, neural spine; pocdf, postzygapophyseal centrodiapophyseal fossa prz, prezygapophyses; sprl, spinoprezygapophyseal lamina; tp, transverse process. Full-size DOI: 10.7717/peerj.14333/fig-21

Figure 22 Middle caudal vertebrae of Caieiria allocaudata. In (1) left lateral; (2) anterior; (3) dorsal; (4) right lateral; (5) posterior and (6) ventral views. Abbreviations: ns, neural spine; pocdf, postzygapophyseal centrodiapophyseal fossa; poz, postzygapophyses; prz, prezygapophyses; prsl, prespinal lamina; tp, transverse process. Full-size DOI: 10.7717/peerj.14333/fig-22