Abstract
Provelosaurus americanus is the only known representative of the Pareiasauria in the Americas. This mid-size pareiasaur from the Rio do Rasto Formation of southern Brazil has been traditionally considered to be related to smaller forms from the South African Karoo known as the “dwarf pareiasaurs” of Lopingian age. P. americanus, however, co-existed with dinocephalians, which indicates a Guadalupian age. New fossils provide a nearly complete osteological account that forms the basis for a revised diagnosis and a test of phylogenetic relationships of P. americanus. Our results offer further support to the hypothesis that the Brazilian pareiasaur is the sister taxon of the Karoo “dwarf pareiasaurs,” being the earliest member of this group and one of the oldest pareiasaurs known so far. This is reinforced by a radiometric dating of the Morro Pelado Member of the Rio do Rasto Formation. In addition, the association of four individuals of various ontogenetic stages at the type locality supports some degree of social behavior in P. americanus.
Highlights
Pareiasaurs are a successful clade of large herbivorous parareptiles that achieved global distribution throughout the Permian, with oldest records in the Guadalupian, having survived the late Capitanian mass extinction (Day et al, 2015; Day and Rubidge, 2021) and becoming extinct during the end-Permian great biotic crisis
The topology of the majority rule consensus (Tree 1 in Supplementary Material) does not differ from the results obtained by Liu and Bever (2018, 5a) except for the placement of Shihtienfenia permica, which in our analysis is not grouped with the ‘dwarf pareiasaurs’ but rather with the genus Pareiasuchus, and for the position of Nochelesaurus alexanderi, which is basal to Bradysaurus baini rather than in a polytomy
Provelosaurus americanus is recovered within the ‘dwarf pareiasaurs’ or Pumiliopareiasauria sensu Jalil and Janvier (2005), forming a trichotomy with Nanoparia luckhoffi and the Anthodon serrarius-Pumiliopareia pricei dichotomy
Summary
Pareiasaurs are a successful clade of large herbivorous parareptiles that achieved global distribution throughout the Permian, with oldest records in the Guadalupian, having survived the late Capitanian mass extinction (Day et al, 2015; Day and Rubidge, 2021) and becoming extinct during the end-Permian great biotic crisis. Small forms like Nanoparia luckhoffi were size-equivalent to a living giant armadillo and large species such as Bradysaurus baini and Scutosaurus karpinskii had a mass comparable to a domestic bull, the latter with an estimated weight of up to 1.5 tons (Romano et al, 2021) They have been recorded in Brazil (Araújo, 1985b; Cisneros et al, 2005), South Africa (Rubidge, 2005; Van den Brandt et al, 2021a), Zambia (Lee et al, 1997), Niger (Tsuji et al, 2013), Tanzania (Maisch and Matzke, 2019), Morocco (Jalil and Janvier, 2005), Scotland (Spencer and Lee, 2000), Germany (Tsuji and Müller, 2008), Italy (based on footprints, Leonardi et al, 1974), Russia (Ivakhnenko, 1987; Bulanov and Yashina, 2005; Tsuji, 2013), and China (Li and Liu, 2013; Xu et al, 2014; Benton, 2016; Liu and Bever, 2018). Despite being relatively common in the geological record, specially in the Karoo Basin, their taxonomy and interrelationships have long been problematic, in part because their cranial sutural patterns are typically obscured by thick ornamentation
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