When was the first mammal fossil found

Follow Helen on Twitter. Image source, Mark Witton. The mammals ventured out at night to hunt insects. They date back million years. Image source, Steve Sweetman. Researchers from the University of Portsmouth made the discovery. View comments.

To make that possible, mammals evolved a wide variety of complex teeth for biting and grinding food. Drinking milk is made possible by the ability to suck and swallow, aided by the hyoid bones in the throat and muscles that support them. This apparatus also forms the voice box. In July, Luo published a paper revealing a million-year-old vole-sized docodont — a close relative of true mammals — that had the hyoid bones of its throat preserved Microdocodon gracilis is the earliest animal known to have been able to suckle like a modern mammal.

This level of detail is rare, and — similar to the study of the Kayentatherium hatchlings — the work on both the ear and throat bones has been made possible only through advances in microCT scanning techniques, says Krause.

The technique has also revealed details about the olfactory abilities and brains of early mammals. Much of the constellation of features we think of as defining mammals — complex teeth, excellent senses, lactation, small litter size — might actually have evolved before true mammals, and quite quickly.

Although the experts concur on many points, there is still much debate about how early mammal groups are related, and which groups are true mammals. That leads to uncertainty about how key traits evolved, says Hoffman. One sticking point between Meng and Luo, who have each developed their own evolutionary trees, is the haramiyids. The oldest known haramiyids are from million years ago in the Triassic.

If they are true mammals, then mammal origins date back at least that far — if not, then the oldest known mammal is million years old, well into the Jurassic. More fossils will help to resolve such questions, and bring more surprises. Krause and Meng say they are both studying exciting fossils, but are yet to publish their findings on them, and tens of unstudied specimens lie piled in the offices of their Chinese colleagues.

Palaeontologists have many items on their wish lists. One characteristic that Luo wants to understand is growth rates. Reptiles grow slowly throughout their lives, whereas mammals grow in bursts in youth and then plateau. Both Hoffman and Meng agree that embryos and more babies would be significant finds — and, like the Kayentatherium discovery with its dozens of hatchlings, they would help us to pinpoint the date that mammal-style small litter sizes appeared.

Download the full infographic. Hoffman, E. PubMed Article Google Scholar. Hu, Y. Meng, J. Luo, Z. Meng, Q. Science , — Ji, Q. Krause, D. Allin, E. Google Scholar. Zhou, C. Download references. Article 10 NOV News 05 NOV Article 27 OCT Editorial 26 OCT News 30 SEP Although we thought we were studying only one animal, Asaphestera intermedia , one of our major findings was recognizing that what previous paleontologists had thought was a single animal was actually a composite of multiple fossils of at least three very different animals!

We could only be certain of two of them: a new reptile we named Steenerpeton silvae and an early synapsid, Asaphestera platyris , with evidence of a single temporal opening in the skull. The original convolution of these species highlights how subtle the differences were between early mammal ancestors and early reptiles, and the value of re-evaluating historic fossil collections to appraise their identity in light of more recent work. Asaphestera platyris provides the oldest evidence of mammal-like reptiles in the fossil record, establishing a firm date for their diversification around million years ago.

Photograph A and interpretive drawing of the new Joggins reptile, Steenerpeton silvae. Letter abbreviations refer to different anatomical elements. The fossil cliffs at Joggins preserve a time right before a period of drastic climate change. Around million years ago, the Earth began a process of global warming. At the time, much of the equatorial region was covered in rainforests and tropical swamps, which were later fossilized as extensive coal layers across North America and Europe.

When the warming began, these habitats dried up in an event called the Carboniferous rainforest collapse , which triggered a minor mass extinction in these biodiversity hot spots.

Read more: Rainforest collapse in prehistoric times changed the course of evolution. The survivors were all early representatives of modern animal groups , such as modern amphibians and modern reptiles, and showed adaptations for surviving in drier environments.

Joggins is unique in preserving an early glimpse of some of these modern groups before the Carboniferous rainforest collapse. What we find are animals that survived the rainforest collapse were living alongside many of the animals that went extinct, but were rarer, smaller and harder to identify, like Asaphestera.