Before cats ruled and dogs drooled, the hyaenodonts were the top carnivores prowling around. They came in all shapes and sizes, from bear-sized on down, at least until they were supplanted by the carnivorans we know and love today. How this shift happened is still a bit of a mystery, and a new fossil from Tanzania comes to us from right at the cusp of this big change.

There isn't much of the hyaenodont just yet. It's part of an upper jaw with a piece of tooth still embedded in it. But the 25 million year old fossil is distinctive enough that paleontologists Matthew Borths and Nancy Stevens have identified it as something new - a bobcat-sized hyaenodont they've named Pakakali.

Based on the fossil, as well as details from other hyaenodonts, Borths and Stevens hypothesize Pakakali ate small vertebrates and invertebrates. This made the little hunter different from other hyaenodonts of its time, some of which had teeth and jaws specialized for shearing meat and crushing bone. Yet the dog-, cat-, and hyena-like carnivorans of those days were similar to Pakakali in size and dental anatomy, meaning that they might have been competitors in the small generalist niche. 

The overall picture, Borths and Stevens write, is that hyaenodonts accommodated their rivals by becoming more specialized and evolving into a different array of body sizes. And as hyaenodonts became more specialized, they became more vulnerable to sweeping environmental changes - they had unintentionally evolved themselves into a corner in response to carnivorans, with ecological disturbances to climate, forest makeup, and other shifts pulling the rug out from under them. 

The jaw fragment of Pakakali. Credit: Borths and Stevens 2017

Fossil Facts

Name: Pakakali rukwaensis

Meaning: Pakakali means "fierce cat" in Swahili, and rukwaensis is a nod to the Rukwa Rift Basin where the fossils were found.

Age: Oligocene, about 25.2 million years ago.

Where in the world?: Rukwa Rift Basin, Tanzania. 

What sort of organism?: An extinct form of mammal called a hyaenodont.

How much of the organism’s is known?: Part of the upper jaw with a tooth. 


Borths, M., Stevens, N. 2017. The first hyaenodont from the late Oligocene Nsungwe Formation of Tanzania: Paleoecological insights into the Paleogene-Neogene carnivore transition. PLOS ONE. doi: 10.1371/journal.pone.0185301

Previous Paleo Profiles:

The Light-Footed Lizard
The Maoming Cat
Knight’s Egyptian Bat
The La Luna Snake
The Rio do Rasto Tooth
Bob Weir's Otter
Egypt's Canine Beast
The Vastan Mine Tapir
Pangu's Wing
The Dawn Megamouth
The Genga Lizard
The Micro Lion
The Mystery Titanosaur
The Echo Hunter
The Lo Hueco Titan
The Three-Branched Cicada
The Monster of Minden
The Pig-Footed Bandicoot
Hayden's Rattlesnake Demon
The Evasive Ostrich Seer
The Paradoxical Mega Shark
The Tiny Beardogs
The Armored Fish King
North America's Pangolin
The Invisible-Tusked Elephant
The Mud Dragon
The Spike-Toothed Salmon
The Dream Coast Crocodile
Buriol's Robber
Ozimek's Flyer
The Northern Naustoceratopsian
The High Arctic Flyer
The Tomatillo From the End of the World
The Short-Faced Hyena
The Mighty Traveler from Egg Mountain
Keilhau's Ichthyosaur
Mexico's Ancient Horned Face
Mauricio Fernández's Plesiosaur
New Zealand's Giant Dawn Penguin
The Orange Sea Lion
Mongolia's Ginkgo Cousin
The Geni River Frog
Isabel Berry's Dinosaur
The Whale Caiman
The Moab Lizard
Yang Zhongjian's Lizard
The Little Anubis
The Shuangbai Lizard
The Wyvern Dinosaur
The "Need Helmet" Dinosaur
The Jianianhua Dragon
The Liaoning Hunter
The Dalian Lizard
Crompton's Aleodon
Jenkins' Amphibian Serpent From the Chinle
The Large Ancestor Lizard
The Crown Tooth
Currie's Alberta Hunter
The Elephant Bird Mimic
The Crested Thief
The Hiding Hunter
The Horned Lizard
The Silk Bird
The Sieve-Toothed Plesiosaur
The Defenseless Snout
Burian's Lizard
The Small Whaitsiid
The Beautiful Bird