Volumetric Body Mass Estimate and in vivo Reconstruction of the Russian Pareiasaur Scutosaurus karpinskii

Abstract

Pareiasaurs (Amniota, Parareptilia) were characterized by a global distribution during the Permian period, forming an important component of middle (Capitanian) and late Permian (Lopingian) terrestrial tetrapod biodiversity. This clade represents an early evolution of sizes over a ton, playing a fundamental role in the structure of middle and late Permian biodiversity and ecosystems. Despite their important ecological role and relative abundance around the world, our general knowledge of the biology of these extinct tetrapods is still quite limited. In this contribution we provide a possible in vivo reconstruction of the largest individual of the species Scutosaurus karpinskii and a volumetric body mass estimate for the taxon, considering that body size is one of the most important biological aspects of organisms. The body mass of Scutosaurus was calculated using a 3D photogrammetric model of the complete mounted skeleton PIN 2005/1537 from the Sokolki locality, Arkhangelsk Region, Russia, on exhibit at the Borissiak Paleontological Institute, Russian Academy of Sciences (Moscow). By applying three different densities for living tissues of 0.99, 1, and 1.15 kg/1,000 cm3 to reconstructed “slim,” “average” and “fat” 3D models we obtain average body masses, respectively, of 1,060, 1,160, and 1,330 kg, with a total range varying from a minimum of one ton to a maximum of 1.46 tons. Choosing the average model as the most plausible reconstruction and close to the natural condition, we consider a body mass estimate of 1,160 kg as the most robust value for Scutosaurus, a value compatible with that of a large terrestrial adult black rhino and domestic cow. This contribution demonstrates that barrel-shaped herbivores, subsisting on a high-fiber diet and with a body mass exceeding a ton, had already evolved in the upper Palaeozoic among parareptiles, shedding new light on the structure of the first modern terrestrial ecosystems.

Body mass estimate of Anancus arvernensis (Croizet and Jobert 1828): comparison of the regression and volumetric methods

“…In particular, as in previous contributions (Romano et al, 2022b), the work by Morfeld et al ( 2016) was used as a reference for fleshy masses in elephants in natural conditions (therefore avoiding obese or starving individuals) (Figures 6 and 7). Following a procedure recently applied in several clades of terrestrial tetrapods (Romano and Manucci, 2019;Romano and Rubidge, 2019b;Romano et al, 2021aRomano et al, , 2021bRomano et al, , 2022a the sculpted models were uploaded to the software 3D Studio Max which allows the models to be scaled to real sizes and both the surface and the volume of the reconstructions to be calculated. The models were scaled by using as a reference the best preserved long-bone elements.…”

Cranial osteology and a new diagnosis of the late Permian pareiasaur Nanoparia luckhoffi (Broom, 1936) from the Karoo Basin of South Africa, and a consolidated pareiasaurian phylogeny

“…The taxonomic framework of Lee (1994Lee ( , 1997a enabled successive researchers to produce detailed species-level anatomical studies and more advanced palaeobiological studies. Palaeobiological studies include an ontogenetic study of Deltavjatia (Tsuji, 2010(Tsuji, , 2013, bone microstructure, isotopic analyses, and histological studies of several species (Canoville et al, 2014;Rey et al, 2015Rey et al, , 2019Canoville & Chinsamy, 2017) and volumetric body mass estimates for Scutosaurus (Romano et al, 2021) and Bradysaurus (Van den Brandt et al, 2023). New species described since the mid-1990s, comprise detailed cranial descriptions of Arganaceras vacanti (Jalil & Janvier, 2005), Obirkovia gladiator (Bulanov & Yashina, 2005), Bunostegos akokanensis (Sidor et al, 2003;Tsuji et al, 2013), Elginia wuyongae (Liu & Bever, 2018) and a brief cranial description of a tentative new elginid based on the first complete pareiasaur skull from China, Shihtienfenia completus (Wang et al, 2019).…”

The Brazilian Pareiasaur Revisited

“…Pareiasaurs represent the reptiles with the largest body-size in the Permian, and included the first tetrapod species with a fully upright limb posture (Turner et al, 2015). 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).…”