Osteological revision of the holotype of the Middle Jurassic sauropod dinosaur Patagosaurus fariasi Bonaparte, 1979 (Sauropoda: Cetiosauridae)

Abstract

Middle Jurassic sauropod taxa are poorly known, due to a stratigraphic bias of localities yielding body fossils. One such locality is Cerro Cóndor North, Cañadón Asfalto Formation, Patagonia, Argentina, dated to latest Early−Middle Jurassic. From this locality, the holotype of Patagosaurus fariasi Bonaparte 1986 is revised. The material consists of the axial skeleton, the pelvic girdle, and the right femur. Patagosaurus is mainly characterised by a combination of features mainly identified on the axial skeleton, including the following: 1) cervical centra with low Elongation Index; 2) high projection of the postzygodiapophyseal lamina; 3) deep anterior pleurocoels that are sometimes compartmentalized in cervicals; 4) high projection of the neural arch and spine in dorsal vertebrae and anterior(most) caudal vertebrae; 5) deep pneumatic foramina in posterior dorsals which connect into an internal pneumatic chamber; and 6) anterior caudal vertebrae with 'saddle' shaped neural spines. Diagnostic features on the appendicular skeleton include: 1) a transversely wide and anteroposteriorly short femur; 2) a medial placement of the fourth trochanter on the femur; and 3) an anteroposteriorly elongated ilium with a rounded dorsal rim, with hook-shaped anterior lobe. The characters that are diagnostic for Patagosaurus are discussed, and the osteology of Patagosaurus is compared to that of Early and Middle Jurassic (eu)sauropods from both Laurasia and Gondwana.

New macronarian from the Middle Jurassic of Chongqing, China: phylogenetic and biogeographic implications for neosauropod dinosaur evolution

“…This condition is similar to some early diverging eusauropods (e.g. Shunosaurus and Patagosaurus) and some diplodocids such as Lingwulong [61,63,64]. Both anterior and posterior articular surfaces are dorsoventrally compressed, as occurred in most other macronarians [65].…”

“…It differs from that in some early diverging non-neosauropod eusauropods (e.g. Patagosaurus ) and Dashanpusaurus with internal cavities and lateral openings on the middle/posterior dorsal neural arch [34,63].…”

A new juvenile sauropod specimen from the Middle Jurassic Dongdaqiao Formation of East Tibet

“…The centra are relatively short, with an average elongation index (aEI: ratio of centrum length to the average of posterior centrum height and width) of about 1.5−2.1 ( Table 1 ). This ratio is similar in Shunosaurus (2.0−3.0) from the Middle Jurassic of Sichuan Basin ( Zhang, 1988 ), Tazoudasaurus (1.6) from the Early Jurassic of Morocco, Barapasaurus (about 2) from the Early Jurassic of India ( Allain & Aquesbi, 2008 ; Bandyopadhyay et al., 2010 ), and Patagosaurus (1−1.7) from the Middle Jurassic of Argentina ( Holwerda, Rauhut & Pol, 2021 ), but larger in Cetiosaurus (2.3−2.7), Bagualia (3.8−5.3) ( Pol et al, 2020 ; Gomez, Jose & Pol, 2021 ; Holwerda, Rauhut & Pol, 2021 ), and mamenchisaurids such as Analong ( Ren et al, 2021 ) and Omeisaurus tianfuensis (1.9−6.1) ( He, Li & Cai, 1988 ). The lateral surfaces of the three postaxial cervical centra bear pleurocoels that are partitioned by anterodorsally-trending ridges, as in some cervical vertebrae of Patagosaurus ( Holwerda, Rauhut & Pol, 2021 ), mamenchisaurids and neosauropods ( Wilson, 2002 ).…”

“…This ratio is similar in Shunosaurus (2.0−3.0) from the Middle Jurassic of Sichuan Basin ( Zhang, 1988 ), Tazoudasaurus (1.6) from the Early Jurassic of Morocco, Barapasaurus (about 2) from the Early Jurassic of India ( Allain & Aquesbi, 2008 ; Bandyopadhyay et al., 2010 ), and Patagosaurus (1−1.7) from the Middle Jurassic of Argentina ( Holwerda, Rauhut & Pol, 2021 ), but larger in Cetiosaurus (2.3−2.7), Bagualia (3.8−5.3) ( Pol et al, 2020 ; Gomez, Jose & Pol, 2021 ; Holwerda, Rauhut & Pol, 2021 ), and mamenchisaurids such as Analong ( Ren et al, 2021 ) and Omeisaurus tianfuensis (1.9−6.1) ( He, Li & Cai, 1988 ). The lateral surfaces of the three postaxial cervical centra bear pleurocoels that are partitioned by anterodorsally-trending ridges, as in some cervical vertebrae of Patagosaurus ( Holwerda, Rauhut & Pol, 2021 ), mamenchisaurids and neosauropods ( Wilson, 2002 ). A ventral midline keel is present on the anterior part of each centrum as in the cervical vertebrae of many early-diverging sauropods, such as Shunosaurus ( Zhang, 1988 ), Tazoudasaurus ( Allain & Aquesbi, 2008 ), Omeisaurus ( He, Li & Cai, 1988 ), Patagosaurus ( Holwerda, Rauhut & Pol, 2021 ), Bagualia ( Gomez, Jose & Pol, 2021 ), Spinophorosaurus ( Remes et al, 2009 ), Lapparentosaurus ( Upchurch, 1998 ), Amygdalodon ( Rauhut, 2003 ) and an unnamed sauropod from Morocco ( Nicholl, Mannion & Barrett, 2018 ), as well as in the anteriormost cervical vertebrae of the Rutland Cetiosaurus ( Upchurch & Martin, 2002 ), and also dicraeosaurids such as Lingwulong ( Xu et al, 2018 ).…”

“…The lateral surfaces of the three postaxial cervical centra bear pleurocoels that are partitioned by anterodorsally-trending ridges, as in some cervical vertebrae of Patagosaurus ( Holwerda, Rauhut & Pol, 2021 ), mamenchisaurids and neosauropods ( Wilson, 2002 ). A ventral midline keel is present on the anterior part of each centrum as in the cervical vertebrae of many early-diverging sauropods, such as Shunosaurus ( Zhang, 1988 ), Tazoudasaurus ( Allain & Aquesbi, 2008 ), Omeisaurus ( He, Li & Cai, 1988 ), Patagosaurus ( Holwerda, Rauhut & Pol, 2021 ), Bagualia ( Gomez, Jose & Pol, 2021 ), Spinophorosaurus ( Remes et al, 2009 ), Lapparentosaurus ( Upchurch, 1998 ), Amygdalodon ( Rauhut, 2003 ) and an unnamed sauropod from Morocco ( Nicholl, Mannion & Barrett, 2018 ), as well as in the anteriormost cervical vertebrae of the Rutland Cetiosaurus ( Upchurch & Martin, 2002 ), and also dicraeosaurids such as Lingwulong ( Xu et al, 2018 ). This feature is also present in some non-sauropod sauropodomorphs, including Yizhousaurus ( Zhang et al, 2018 ), Massospondylus ( Barrett et al, 2019 ), Isanosaurus ( Buffetaut et al, 2000 ), and potentially Antetonitrus ( McPhee et al, 2014 ) and Lamplughsaura ( Kutty et al, 2007 ).…”