Ancient life · Mammals and their kin
Brasilodon
Possibly the oldest mammal, or one of its closest relatives.
Our sources give no reliable size for Brasilodon, so this outline of its body shape is not drawn to scale.
DebatedWhether Brasilodon was a true mammal. One 2022 study says yes; other palaeontologists have challenged it.
- When
- About 225 million years ago, in the Late Triassic
- Where
- Southern Brazil
Brasilodon was a tiny animal from southern Brazil, about 225 million years ago. It is usually classed as a cynodont, part of the group that mammals came from. In 2022 a study of three of its jaws found that it grew only two sets of teeth, milk teeth and then adult teeth, as mammals do. In living mammals that goes with suckling young and warm blood.
On that evidence the study, and the Natural History Museum, called Brasilodon the oldest known mammal, with teeth dated to 225.42 million years ago. Not everyone agrees. In 2023 other palaeontologists published a reply questioning how the study had sorted and read the fossils, and many still count Brasilodon as a close relative of mammals rather than a mammal.
It lived at the same time as the oldest known dinosaurs, 25 million years after the Great Dying, and probably lived in burrows like shrews do today.
Read more in Before the dinosaurs.
Also in mammals and their kin
- Dimetrodon A sail-backed hunter on our side of the family tree
- Morganucodon A tiny early mammal named after Glamorgan
- Pakicetus One of the first whales, with four legs
- Dorudon An early whale that lived wholly in the sea
- Blue whale The largest animal ever to live
- Woolly mammoth An Ice Age elephant of the far north
Sources
- Cabreira, Schultz and others, Journal of Anatomy 241(6) (2022), Diphyodont tooth replacement of Brasilodon: a Late Triassic eucynodont that challenges the time of origin of mammals
- Abdala, Norton and others, Journal of Anatomy 242(4) (2023), On taxonomic issues, ontogenetic series and tooth replacement: comments on the Brasilodon study
- Bonaparte and others, Revista Brasileira de Paleontologia 8(1) (2005), New information on Brasilodon and Brasilitherium (Cynodontia, Probainognathia) from the Late Triassic, southern Brazil
- Natural History Museum, London (press release), Earliest known mammal is identified using fossil tooth records