Riograndia

Riograndia
Temporal range: Norian
~225.42 Ma
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Family: Tritheledontidae
Genus: Riograndia
Bonaparte et al., 2001
Species:
R. guaibensis
Binomial name
Riograndia guaibensis
Bonaparte et al., 2001

Riograndia is an extinct genus of tritheledontid cynodonts from the Late Triassic of South America. The type and only species is Riograndia guaibensis. Remains have been found in the Caturrita Formation of the geopark of Paleorrota. It was a small non-mammalian cynodont, with several advanced features also present in mammals. Several specimens of Riograndia guaibensis have been found in the towns of Candelária and Faxinal do Soturno in the Caturrita Formation. The genus defines the Riograndia Assemblage Zone.

Classification

Riograndia is currently classified as a basal genus in the family Tritheledontidae. Other tritheledontids include the related Irajatherium, and two clades, a more basal group including Sinoconodon, Brasilitherium, Brasilodon, and Morganucodon, and a more derived clade of Chaliminia, Elliotherium, Pachygenelus, Diarthrognathus, and Tritheledon. The below cladogram was found by Martinelli and Rougier in 2007 and modified by Soares et al. in 2011, with Tritheledontidae added after Ruta et al. (2013):

Brasilodon

Brasilitherium

Sinoconodon

Morganucodon

Tritheledontidae

Riograndia

Irajatherium

Chaliminia

Elliotherium

Pachygenelus

Diarthrognathus

Tritheledon

Paleoecology

Restoration of Brasilodon and Riograndia

All specimens of Riograndia come from the Late Triassic aged Caturrita Formation. The formation dates to about 225.25 million years ago. Dinosaurs from the formation only include the sauropodomorphs Unaysaurus and Guaibasaurus. Non-dinosaurian animals include the dinosauriform Sacisaurus; the dicynodont Jachaleria; an unnamed phytosaurian; isolated archosaurian teeth; an amphibian classified in Stereospondyli; and many common tetrapods smaller than 15 cm (5.9 in) long. Among the tetrapods is the procolophonid Soturnia; the sphenodontid Clevosaurus; the lepidosaurian Cargninia; the pterosaurian Faxinalipterus, and an assortment of mammaliamorphs including Riograndia, Brasilodon, and Irajatherium.


This page was last updated at 2023-11-07 01:46 UTC. Update now. View original page.

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