Diversity and evolution of the sacroiliac joint in Scinaxini.

• Grant number: 24/07182-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2025
• End date: March 31, 2027
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Principal Investigator: Célio Fernando Baptista Haddad
• Grantee: Mariana Vaini Marques
• Host Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil
• Associated research grant: 21/10639-5 - Center for Research on Biodiversity Dynamics and Climate Change, AP.CEPID

Abstract

In anuran amphibians, sesamoids are present in the joints of the pelvic girdle and limbs and have been studied through descriptive, ontogenetic, and functional approaches. The morphology of the sacroiliac joint in anurans is correlated with distinct patterns of mobility in the joint and locomotor behaviors. The Hylinae subfamily contains the Scinaxini tribe. This tribe has as one of its 13 phenotypic synapomorphies, the circular or trapezoid-shaped medial sesamoid of the sacroiliac joint. Scinaxini comprises the genus Julianus, which has as one of its phenotypic synapomorphies the medial sacroiliac sesamoid with a slight medial elongation, the length being half the width, with a modification in J. camposseabrai, presenting the medial sacroiliac sesamoid elongated medially, with its width at least three times the length. Although we already have some knowledge about the morphological diversity of sacroiliac sesamoids in Scinaxini, there is still a lack of information regarding the musculature and tendons associated with them, as well as the natural history of J. camposseabrai, limiting our understanding of this particular modification in the sacroiliac joint of the tribe. Therefore, the objective of this project is to contribute to filling these gaps and advancing knowledge about the osteo-tendomuscular variation of the sacroiliac joint in Julianus camposseabrai, comparing it with other species of the Scinaxini tribe, describing the variation in the shape of the sesamoids of the sacroiliac joint of the genus Julianus, and inferring locomotion capabilities of the described sacroiliac joints, as the morphological variability of the sacral sesamoid may be related to specific locomotion capacities.