Appendicular myological reconstruction of the forelimb of the giant titanosaurian sauropod dinosaur Dreadnoughtus schrani

Abstract

Soft tissues are variably preserved in the fossil record with external tissues, such as skin and feathers, more frequently preserved than internal tissues (e.g. muscles). More commonly, soft tissues leave traces of their locations on bones and, for muscles, these clues can be used to reconstruct the musculature of extinct vertebrates, thereby enhancing our understanding of how these organisms moved and the evolution of their locomotor patterns. Herein we reconstruct the forelimb and shoulder girdle musculature of the giant titanosaurian sauropod Dreadnoughtus schrani based on observations of osteological correlates and dissections of taxa comprising the Extant Phylogenetic Bracket of non‐avian dinosaurs (crocodilians and birds). Fossils of Dreadnoughtus exhibit remarkably well‐preserved, well‐developed, and extensive muscle scars. Furthermore, this taxon is significantly larger‐bodied than any titanosaurian for which a myological reconstruction has previously been attempted, rendering this myological study highly informative for the clade. In total, 28 muscles were investigated in this study, for which 46 osteological correlates were identified; these osteological correlates allowed the reconstruction of 16 muscles on the basis of Level I or Level II inferences (i.e. not Level I' or Level II' inferences). Comparisons with other titanosaurians suggest widespread myological variation in the clade, although potential phylogenetic patterns are often obscured by fragmentary preservation, infrequent myological studies, and lack of consensus on the systematic position of many taxa. By identifying myological variations within the clade, we can begin to address specific evolutionary and biomechanical questions related to the locomotor evolution in these sauropods.

Myological reconstruction of the pelvic girdle and hind limb of the giant titanosaurian sauropod dinosaur Dreadnoughtus schrani

“…Alternatively, Wilhite (2005) and Silva Junior et al (2019) suggested that this area could instead correspond to a ligamentous connection between the tibia and fibula. It is possible that this area could represent attachment of both muscle and ligament, as has been previously suggested for soft tissues connecting the radius and ulna via the interosseous ridge of the former bone (Voegele et al, 2020, and references therein).…”

“…Scarcity of myological investigations of sauropods, in general, including well‐preserved and fairly complete titanosaurian taxa (e.g., Rapetosaurus , Curry Rogers, 2009; Saltasaurus , Powell, 2003), combined with a general lack of quantity and quality of preservation for the clade as a whole, has greatly limited our understanding of titanosaurian appendicular musculature. Only a few previous species‐level myological studies have been completed for members of Titanosauria (Borsuk‐Bialynicka, 1977; Ibiricu et al, 2018; Klinkhamer et al, 2018, 2019; Otero & Vizcaíno, 2008; Voegele et al, 2020). Alternatively, descriptions of sauropod appendicular material occasionally include discussion of probable osteological correlates for muscle attachment (e.g., Curry Rogers, 2009; Gallina & Apesteguía, 2015; Harris, 2007; Silva Junior et al, 2019).…”

The postcranial skeleton of Cerrejonisuchus improcerus (Crocodyliformes: Dyrosauridae) and the unusual anatomy of dyrosaurids

“…Extant crocodylians are naturally used for morphological comparison when it comes to fossil crocodyliforms ( Langston, 1995 ; Denton, Dobie & Parris, 1997 ; Hua, 2003 ; Jouve, Bouya & Amaghzaz, 2005 ; Jouve et al, 2006 ; Schwarz, Frey & Martin, 2006 ; Schwarz-Wings, Frey & Martin, 2009 ; Hastings et al, 2010 ; Hastings, Bloch & Jaramillo, 2011 , 2014 ; Schwarz-Wings, 2014 ; Martin, Sarr & Hautier, 2019 ) or other archosaurs ( Maidment & Barrett, 2011 ; Liparini & Schultz, 2013 ; Voegele et al, 2020 ), and also serve as behavioral and functional archetypes (e.g. Hua & Buffetaut (1997) ; Jouve et al (2008) ; Schwarz-Wings, Frey & Martin (2009) ; Schwarz-Wings (2014) ).…”

The Postcranial Anatomy of Pachycephalosaurs (Ornithischia: Pachycephalosauria) and its Phylogenetic and Myological Implications

“…Luckily, direct evidence of muscles is often preserved by the surface texture of bones. Osteological correlates of muscles are created as a muscle exerts stress on the underlying bone (Bryant & Seymour, 1990;Frankel & Nordin, 2001;Voegele et al, 2020;Voegele et al, 2021). Such textures indicate where muscles would have attached to the bone, the minimum size of the attachment area, and even the type of attachment.…”

“…Such textures indicate where muscles would have attached to the bone, the minimum size of the attachment area, and even the type of attachment. Unfortunately, not all muscles will produce visible texturing, nor will the entire attachment area be preserved (Bryant & Seymour, 1990;Dilkes et al, 2000;Dilkes et al, 2012;Voegele et al, 2020;. As such, when reconstructing the myology of fossil organisms, it is often necessary to rely on comparisons with the extant phylogenetic bracket (EPB).…”