Ontogenetic variation in an ornithopod femur from the Upper Cretaceous of Argentina :
Rodríguez-Borges, Airam (Universidad de Zaragoza)
González-Dionis, Javier (Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET))
Filippi, Leonardo S. (Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET))
Cerda, Ignacio A. (Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET))
Lee, Yuong-Nam (Seoul National University)
Cruzado-Caballero, Penélope (Universidad de La Laguna. Departamento de Biología Animal, Edafología y Geología)

Data:	2026
Resum:	The paleobiodiversity of Gondwanan ornithopods and the number of indeterminate remains attributed to this clade have increased markedly in recent decades, especially in South America. The femur is one of the most frequently preserved postcranial elements in the South American fossil record and often retains diagnostic features that have been used to establish new species. However, the effect of ontogenetic and intraspecific variation on femoral morphology remains poorly understood in South American ornithopods. Here we describe and analyze a small right femur (MAU-PV-CO-684) from the Bajo de la Carpa Formation (Santonian), recovered from the Cerro Overo-La Invernada area (Rincón de los Sauces, Neuquén, Argentina). Histological analyses indicate that the specimen is an early juvenile, probably less than one year old at the time of death. Despite its immature ontogenetic stage, the femur retains several features consistent with the Ornithopoda, including an anteroposteriorly curved diaphysis and a femoral neck that separates the femoral head from the greater trochanter. A preliminary phylogenetic analysis places MAU-PV-CO-684 within Rhabdodontomorpha, with alternative placements among early-diverging iguanodonts or early-diverging Neornithischians. However, several femoral characters with strong phylogenetic signal also exhibit ontogenetic variability, suggesting that developmental stage can influence phylogenetic inference when analyzing isolated elements. Therefore, its taxonomic assignment has been preferred as Iguanodontia indet. MAU-PV-CO-684 provides new insights into the ontogenetic variation of ornithopod femora in Gondwana, highlights the need to integrate histological data when evaluating fragmentary material, and underscores the taxonomic importance of femoral characters in South American ornithopods.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Iguanodontia ; Neuquén basin ; Intraspecific variation ; Histology ; Santonian
Publicat a:	Geologica acta, Vol. 24 (2026) , p. 1-28 (New contributions to the paleontology of Iberian Mesozoic tetrapods) , ISSN 1696-5728

Adreça original: https://revistes.ub.edu/index.php/GEOACTA/article/view/54338
DOI: 10.1344/GeologicaActa2026.24.17

45 p, 16.0 MB

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