The mouse-sized mammal that lived alongside dinosaurs 166 million years ago on an ancient Scottish island

Transcript

00:00I'm Dr. Elsa Panchiaroli and I'm a research associate here at National Museum Scotland.

00:05We've got these two incredible specimens from the Isle of Skye in Scotland, around 166 million years old,

00:12that's the middle of the Jurassic, and they represent an adult and a juvenile of the same species.

00:18It would have been about the size of a squirrel or a chipmunk, but the juvenile is of course smaller than the adult

00:25and this lets us compare them and see how they grew.

00:27This animal is called Crusatodon kirtlingtonensis, which is a bit of a mouthful,

00:32but it's a really important animal because of where it sits in the mammal tree of life.

00:37So what's really fascinating is that mammals today grow very rapidly when they're young to reach adult size

00:43and then they don't really grow after that point.

00:46Whereas what we've discovered by having this juvenile and adult specimen from Skye

00:50is that it took a very long time for the juvenile to grow to adult size

00:55and then it potentially even grew slightly as an adult.

00:58So this is really quite a different pattern from what we see today in living mammals of similar body mass.

01:04One of the first things we had to do was try and figure out how old this juvenile was.

01:08So it had about 50% of its adult teeth grown in and some of its baby's teeth were still in the jaw

01:14and we worked out by looking at the cementum rings, this is a tissue that's found in the teeth,

01:20that it was as much as two years old at this point.

01:23So for an animal that's only the size of a squirrel, you would expect this tooth replacement to happen much, much earlier.

01:29So the site on the Isle of Skye is really unique.

01:32It's proven to be one of the most important vertebrate fossil sites from the time of dinosaurs in the UK.

01:37So at National Museum Scotland, we hold the majority of the collection of specimens ever found at that site

01:43and the two specimens that were in this study, one was one of the first specimens ever found there in the 1970s

01:50and the other one was found much later by my team in around about 2016

01:55and it was amazing to discover that they were the same species because it then allowed us to do this direct comparison

02:01between a juvenile and an adult specimen.

02:04The really unique thing about having both a juvenile and an adult is that you can compare them

02:09and you can start to look at how this species would have grown

02:12and this is something that we really want to know because modern mammals have a very unique way of growing.

02:16Did they grow like that in the time of dinosaurs? Well, this is what these specimens tell us.

02:21This is a really big deal, a big discovery because we already knew that mammals lived to a much later age in the Jurassic

02:29but we didn't know, did they get there quickly in their growth or was it a very long and continuous growth?

02:36And this really matters because it's part of piecing together how the modern world has come to be

02:41and how the animals that we see today grow and develop.

02:44So that's one of the reasons that it became a major paper in Nature

02:48is that it's of international significance for our understanding of the evolution of mammals.