Aleodon from Africa Present in Brazilian Triassic Rocks

A team of international researchers have reported the discovery of fossils attributed to the African cynodont Aleodon in Middle-early Late Triassic rocks from several locations in the state of Rio Grande do Sul (southern Brazil).  Prior to these fossil finds, this protomammal (a member of the Probainognathidae family), a distant ancestor of modern mammals, was only known from Africa.

A Scale Drawing of the Skeleton of Aleodon (A. cromptoni)

The known bones of Aleodon are shown in yellow.

Picture credit: PLOS ONE

In the picture above the known bones attributed to Aleodon (A. cromptoni) are shown in yellow and a cat provides a scale comparison.

A Curious Cynodont Living Alongside Dinosaur Precursors

Writing in the on-line academic journal “PLOS ONE”, the researchers, which include Agustín Martinelli (Universidade Federal of Rio Grande do Sul, Brazil), conclude that fossils previously thought to represent another cynodont – Chiniquodon actually are Aleodon specimens, as such they are the first of this genus to be found outside of Africa.  The carnivorous Aleodon lived alongside basal members of the Dinosauria and other types of archosaur, as well as numerous mammal-like reptiles, including the giant herbivore Dinodontosaurus.  The fossils of Dinodontosaurus are so numerous that they are used to date the relative age of the strata in this part of southern Brazil.  All the fossils ascribed to Aleodon, including cranial material and teeth come from the Dinodontosaurus Assemblage Zone.

Aleodon Skull Material and Line Drawing (Aleodon cromptoni)

Skull in left lateral view with accompanying line drawing. Scale bar = 50 mm.

Picture credit: PLOS ONE

Namibian and Tanzanian Fossils

The Aleodon genus was first erected based on fossil material discovered in Tanzania and Namibia.  The South American material was compared to the African specimens and a new species of Aleodon, a sister taxon to the African species was named.  The new Aleodon species honours Dr Alfred “Fuzz” Crompton, who established the genus in 1955 with the naming of A. brachyrhamphus.

In a reassessment of the African fossil material, a specimen form Namibia which was thought to represent a member of the related family, the Chiniquodontidae or possibly a member of the Traversodontidae may actually be an Aleodon.  The scientists also identified as Aleodon a total of seven specimens from the Rio Grande do Sul region.  Phylogenetic analysis indicated that Aleodon cromptoni may be, as suspected, a species in the Chiniquodontidae family.

Whilst the research work was hampered due to the incomplete and partial specimens, the authors note that the identification of these Late Triassic Aleodon fossils in Brazil strengthens the correlation between probainognathians from this epoch in South America and in Africa.

Part of the Upper Jaw of A. cromptoni with Line Drawing

Photographs and accompanying drawings of right maxilla MPDC-501-117 in lateral (A), ventral (B), and medial views (C). Scale bar equals 10 mm

Picture credit: PLOS ONE

For Triassic prehistoric animal models and figures: Prehistoric Animal Models and Figures.