Science and Technology Production
Congress
Authorship
APALDETTI, GRACIELA CECILIA
;
Ezcurra, Martín D.
;
Martinez, Ricardo Nestor
;
Cerda, Ignacio Alejandro
;
Peyre de Fabreguès, Claire
;
Abelín, Diego
Date
2025
Publishing House and Editing Place
Asociación Paleontológica Argentina
Summary
Information provided by the agent in
SIGEVA
The Sauropodomorpha clade includes the long-necked, herbivorous dinosaurs, some of which attained the largest body sizes ever recorded for a terrestrial animal. The acquisition of gigantism entailed a series of anatomical and physiological transformations, during which the limb bones underwent significant modifications. The first giant sauropodomorphs are classified within the Lessemsauridae, a group of early sauropods that flourished in Gondwana during the Late Triassic and Early Jurassic. The...
The Sauropodomorpha clade includes the long-necked, herbivorous dinosaurs, some of which attained the largest body sizes ever recorded for a terrestrial animal. The acquisition of gigantism entailed a series of anatomical and physiological transformations, during which the limb bones underwent significant modifications. The first giant sauropodomorphs are classified within the Lessemsauridae, a group of early sauropods that flourished in Gondwana during the Late Triassic and Early Jurassic. The largest Triassic lessemsaurids have been estimated with a body mass of 8–9 tons (Lessemsaurus sauropoides from the Los Colorados Formation of Argentina), while Early Jurassic lessemsaurids reached 12 tons (Ledumahadi mafube from the upper Elliot Formation of South Africa). Accordingly, there was a notable increase in the upper limit of sauropodomorph body size following the Triassic/Jurassic boundary. In this report, we document the proximal half of a left femur ( PVSJ 1095, Paleovertebrados del Instituto y Museo de Ciencias Naturales, San Juan) from the Upper Triassic (upper Norian–Rhaetian) Quebrada del Barro Formation of the Marayes–El Carrizal Basin, San Juan Province. This specimen is assigned to Lessemsauridae based on a distinctive paleohistological feature of the clade: the presence of thick zones of highly vascularized fibrolamellar bone within a cyclical growth pattern. No femur is currently known for Ingentia prima, the other lessemsaurid previously reported for this geological unit. Consequently, comparisons with the new specimen are currently precluded. A linear regression was conducted between the minimum shaft circumference (MSC= 55cm) and femoral length (preserved length= 62cm; R2= 0.9539, p < 0.001), as well as MSC and body mass (R2= 0.9872, p < 0.001) of 89 sauropodomorph species. The results of this regression predicted a femoral length of ~1300 cm and a body mass of ~13 tons for PVSJ 1095. The optimization of the body mass in the phylogeny of Sauropodomorpha after the inclusion of PVSJ 1095 demonstrates a notable increase from ~5 kg in the late Carnian period to ~13 tons in the late Norian–Rhaetian, which represents a linear increase of 400–1000 kg per million year. The evolution of the body mass of early sauropodomorphs is best described by a multi-trend model with local optima, and there is a distinct increase in its rates during the middle–late Norian. Consequently, PVSJ 1095 propels the upper limit of Triassic sauropodomorph body size to values previously believed to have been attained solely following the Triassic/Jurassic mass extinction.
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Key Words
SAUROPODOMORPHADINOSAURIAGIGANTISMTRIASSIC