Riograndia

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Riograndia
Temporal range:
Ma
↓
Scientific classification Edit this 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

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.[3] The genus defines the Riograndia Assemblage Zone.[1][4]

Description

postcanine teeth with approximately equal 5-9 sharp cuspules located along the almost semicircular edge of the crowns of the upper postcanine teeth and in the posterodorsal edge of the lower postcanine teeth.[2] Most specimens have skulls of approximately 35 mm long.[2] Study of the postcranial skeleton shows that Riograndia had a semi-sprawling forelimbs, similar to those of more basal synapsids. The limbs of more advanced cynodonts are positioned more straight. The body of Riograndia was held above the ground with the help of adductor muscles attached to the forelimbs.[1]

Classification

Riograndia was originally assigned to the monotypic family Riograndidae within

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,[3] with Tritheledontidae added after Ruta et al. (2013):[5]

A cladogram after Stefanello et al. (2023):[6]

Probainognathia

Paleoecology

Restoration of Brasilodon and Riograndia

All specimens of Riograndia come from the

archosaurian Faxinalipterus, and an assortment of mammaliamorphs including Riograndia, Brasilodon, and Irajatherium.[3]

References

  1. ^
    doi:10.1016/j.geobios.2019.02.006.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  2. ^
    doi:10.1111/1475-4983.00194.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  3. ^
    PMID 21437390
    .
  4. ^
    doi:10.1016/j.jsames.2020.102846
    .
  5. ^
    PMID 23986112
    .
  6. doi:10.1007/s10914-022-09648-y
    .

External links
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