THE MAIN MAMMALS

Here are some of the key animals that help paint a picture of how modern mammals evolved

Castorocauda

SIZE: 500-800 grams, 43-50 centimetres long

ORIGIN: Inner Mongolia, Middle-Late Jurassic, around 166-157 million years ago

FACTS: Adapted for life in the water, this early mammal had paddle-like limbs, a flattened tail, and specialised teeth for eating fish. It’s one of the largest known Jurassic mammals, and although it somewhat resembles a modern beaver or platypus, it’s not closely related.

Kayentatherium

SIZE: Equivalent to a large cat or mid-sized dog ORIGIN: Southwestern USA, Early Jurassic, around 200-183 million years ago

FACTS: One of the closest relatives of true mammals. They had at least some hair, walked upright, and had a high metabolism.

Volaticotherium

SIZE: 70 grams, 12-14 centimetres long ORIGIN: Inner Mongolia, Middle-Late Jurassic, around 166-157 million years ago

FACTS: With its skin membrane (patagium) stretching between its body and limbs, Volaticotherium could have glided between trees. When it was discovered in 2006, it was the oldest known fossil of a flying mammal.

Litovoi

SIZE: 160 grams, 15-20 centimetres long

ORIGIN: Romania, Late Cretaceous, around 66-69 million years ago

FACTS: Litovoi is a multituberculate, an extinct group that thrived in the Cretaceous, survived the asteroid impact, then wasted away to extinction about 35 million years ago. It had one of the smallest brains, proportional to body size, ever for a mammal.

Periptychus

SIZE: 20 kilograms, size of a medium-to-large dog

ORIGIN: Southwestern USA, Early Paleocene, around 63.3-61.7 million years ago

FACTS: Periptychus is a ‘condylarth’, a member of a cluster of primitive hoofed mammals that proliferated after the dinosaur extinction. It had robust teeth to eat roots, stems and other tough plants, and a stout skeleton well-suited for moving on land and navigating forest vegetation.

45cm Although is relatively small by today’s standards – it was about the size of a grey squirrel – it is one of the largest known Jurassic mammals to be discovered to date Size isn’t everything Castorocauda

IN DETAIL: CASTOROCAUDA Flat, beaver-like tail for paddling through water Webbed feet for swimming Fur-covered body to keep it warm and waterproof 2mm M1 M1 Specialised teeth that curve backwards to help it hold onto slippery fish, as seen in modern seals Semi-sprawling limbs with large muscles for swimming and digging