Pycnonemosaurus Nevesi Is the New King
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Cretaceous Research 69 (2017) 71e89 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Allometry and body length of abelisauroid theropods: Pycnonemosaurus nevesi is the new king * Orlando Nelson Grillo a, Rafael Delcourt b, a Museu Nacional/Universidade Federal do Rio de Janeiro, Departamento de Geologia e Paleontologia, 20940-040, Rio de Janeiro, RJ, Brazil b Museu de Zoologia da Universidade de Sao~ Paulo, Laboratorio de Paleontologia, Avenida Nazare, 48, Ipiranga, 04263-000, Sao~ Paulo, SP, Brazil article info abstract Article history: Abelisauroid dinosaurs normally reached an average body length (BL) of 5e9 m, but there are contro- Received 30 May 2016 versies due to the incomplete or fragmentary nature of most specimens. For Ekrixinatosaurus, for Received in revised form example, BL was estimated as 10e11 m or 7e8 m; for Pycnonemosaurus it was proposed 7e8 m, however 1 September 2016 its preserved bones are larger than any other described abelisauroid. The lack of a consistent method- Accepted in revised form 4 September 2016 ology complicates comparisons of estimated BL, so we reevaluated the estimative for the seven most Available online 7 September 2016 complete specimens of abelisauroids and compared the values against 40 measurements from the skull, vertebrae and appendicular elements using bivariate equations. It allowed estimating the BL of other 30, Keywords: Abelisauroidea less complete, specimens of abelisauroids and to evaluate the allometric scaling of the skeletal parts. 2 > Abelisauridae Strong correlations (R 0.96) were obtained for all vertebrae and hindlimb measurements, as well as Pycnonemosaurus nevesi skull height, and length of skull roof, lacrimalesquamosal, scapulocoracoid and humerus; other skull and Body length forelimb measurements present weak correlation due to extreme morphological transformations Allometry observed in Abelisauridae and were not adequate for BL estimation. Abelisauroids gradually increased in size during evolution: the mean BL was 3.3 ± 2.5 m for basal abelisauroids and Noasauridae, 5.4 ± 1.8 m for basal Brachyrostra and Majungasauridae, and 7.1 ± 2.1 m for Furileusaura. Despite this variation, diversity of BL on each geographic region and stratigraphic epoch was relatively constant (BL usually varied from 4 to 8 m). The smallest noasaurid and abelisaurid are, respectively, Velocisaurus (1.5 ± 0.1 m) and Genusaurus (3.6 ± 0.0 m). The largest abelisaurids is Pycnonemosaurus nevesi (8.9 ± 0.3 m) followed by Carnotaurus (7.8 ± 0.3 m), Abelisaurus (7.4 ± 0.7 m) and Ekrixinatosaurus (7.4 ± 0.8 m). Skull mea- surement scale negatively at a similar rate but the height scales almost isometrically and the skull roof length scales more negatively; this probably caused a bending on the skull that may explain the upward orientation of the snout in large taxa. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction also recognized by the reduced forelimb, characteristic of the more derived taxa (Burch and Carrano, 2012; Pol and Rauhut, 2012; Abelisauroidea (Bonaparte, 1991) is a diverse group of theropod Novas et al., 2013). dinosaurs phylogenetically positioned within Ceratosauria. They Abelisauroids are traditionally divided into two main branches, inhabited the Gondwana during the Cretaceous, but remains were Noasauridae and Abelisauridae (Novas et al., 2013), but two species, also recovered from Europe (Novas et al., 2013). Abelisauroids are Eoabelisaurus mefi and Ligabueino andesi, are outside this di- best known by their characteristic derived skull, that undertook chotomy, as basal abelisauroids (Filippi et al., 2016; see also Farke several morphological transformations that include reduction of and Sertich, 2013; Gianechini et al., 2015 for Eoabelisaurus phylo- the snout and ornamentations on the nasal and skull roof (e.g., genetic position). According to estimates from literature, the basal Bonaparte et al., 1990; Sampson and Witmer, 2007), but they are abelisauroid Ligabueino was very small (0.74 m; Bonaparte, 1996), but Eoabelisaurus had a medium body size (6e6.5 m; Pol and Rauhut, 2012). Noasauridae includes gracile and small-sized ani- mals (Novas et al., 2013) with a maximum body length of approx- * Corresponding author. imately 2.5 m (Machado et al., 2013), such as Masiakasaurus E-mail addresses: [email protected] (O.N. Grillo), [email protected] knopfleri and Velocisaurus unicus. Abelisaurids were larger animals (R. Delcourt). http://dx.doi.org/10.1016/j.cretres.2016.09.001 0195-6671/© 2016 Elsevier Ltd. All rights reserved. 72 O.N. Grillo, R. Delcourt / Cretaceous Research 69 (2017) 71e89 compared to noasaurids, with body lengths usually estimated at Remains of theropods from Brazil deposits are scarce and most more than 5 m. Medium sized abelisaurids (5e7 m) include Skor- represent small to medium size animals (Bittencourt and Langer, piovenator bustingorryi (6e7m;Canale et al., 2009), Majungasaurus 2011). Recently, isolated abelisauroid materials were described by crenatissimus (6e7m;Rogers et al., 2007), Arcovenator (5e6m; Novas et al. (2008) from the Marília Formation (Bauru Group), Tortosa et al., 2014) and Aucasaurus (5.5e6 m; estimated from including a complete dorsal vertebra (CPP 893; referred in this figure in Coria et al., 2002). The length of Xenotarsosaurus bona- paper as “Marília abelisaurid”), distal portion of a left femur (CPP partei was also estimated as 5 m by Lamanna et al. (2002), but this 174) and a pedal phalanx (CPP 692). Also from the Marília Forma- estimative is doubtful because it was based on a comparison to the tion, Machado et al. (2013) described a complete right tibia (MCT length of the femur of Carnotaurus sastrei that was partially 1783-R; referred in this paper as “Cambara abelisauroid”). Mendez reconstructed from rock impressions (Bonaparte et al., 1990; Juarez et al. (2014) described isolated axis, fibula, ilium and ischia that Valieri and Porfiri, 2010). Some abelisaurids reached bigger sizes, as correspond to three different abelisauroid individuals from the Rio is the case of Carnotaurus sastrei with 8e9m(Bonaparte et al., Preto and Marília formations. Abelisaurids were also described for 1990). Ekrixinatosaurus novasi was initially estimated at 7e8m the Adamantina Formation (Bauru Group): a fragmentary left ilium (Calvo et al., 2004). However, posterior analyses, based on com- (DGM 927-R; Brum et al., 2016) and a distal articulation of a right parison of the proportions of cranial, axial and hindlimb elements femur (MCT 1857-R; Brum et al., 2016). The only formally named to Majungasaurus and Carnotaurus, suggested it was 10e11 m long abelisaurid from Brazil is Pycnonemosaurus nevesi, also from the (Juarez Valieri and Porfiri, 2010), but Novas et al. (2013) disagreed Bauru Group, and has axial and hindlimb elements preserved with this value. Recently, there were report of two giant abelisaurid (Kellner and Campos, 2002). from the uppermost Cretaceous of Northern Turkana, Kenya, with According to Kellner and Campos (2002) Pycnonemosaurus an estimated total length of 11e12 m (Sertich et al., 2013) and from reached 7e8 m. However, if the tibia of Pycnonemosaurus is the Upper Cretaceous of Morocco with body size similar to Carno- compared to that of other abelisauroid specimens (Fig. 1) it is clear taurus and Ekrixinatosaurus Chiarenza and Cau (2016), but they that it is the biggest, both in length and diameter of the shaft, were not formally described. indicating that it belongs to a much larger animal than Carnotaurus, Fig. 1. Variation in the size of the tibiae of abelisauroids. A, Pycnonemosaurus DGM 859-R (right tibia; lateral view); B, Ekrixinatosaurus MUCPv 294 (left tibiotarsus reflected; lateral view); C, Aucasaurus MCF-PVPH 236 (right tibiotarsus and fibula; lateral view); D, Skorpiovenator MMCH-PV 48 (right tibiotarsus and fibula; cranial view); E, Xenotarsosaurus UNPSJB-PV 184/612 (left tibiotarsus reflected; medial view); F, Quilmesaurus MPCA-PV-100 (right tibia; lateral view; modified from Juarez Valieri et al., 2007, Fig. 2A); G, Arcovenator MHNA-PV-2011.12 (right tibia; lateral view; modified from Tortosa et al., 2014, Fig. 6A); H, Cambara abelisauroid MCT 1783-R (right tibia; lateral view; modified from Machado et al., 2013, Fig. 1D); I, Masiakasaurus FMNH PR 2122 (left tibia reflected; lateral view; modified from Carrano et al., 2002, Fig. 15D); J, Eoabelisaurus MPEF PV 3990 (proximal end of right tibia; lateral view; modified from Pol & Rauhut, 2012, Suppl-fig. 11A); K, Majungasaurus FMNH PR 2424 (proximal end of left tibia reflected; lateral view; modified from Carrano, 2007, Fig. 6A) and L, Carnotaurus MACN-Pv-CH 894 (proximal end of left tibia reflected; lateral view; modified from Bonaparte et al., 1990, Fig. 33A). 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