Hi everyone. Happy weekend. It's going to be a beautiful one (at least that's what the weather people are saying) in my area. I hope to get outside a lot and maybe finish a few chores too.👍
Just a warning-this is a LONG post.
Back in Monday's post (when I talked about part 2 of my recent trip to Quebec), I mentioned a park we visited that had lots of fish fossils. I didn't include it in Monday's post because I wanted to tell you a bit about the park. Miguasha tells an important chapter in the story of the evolution of life.
Miguasha National Park is also World Heritage Site. In the park is a cliff where a lot of fish fossils have been found. Not just any fish fossils, but fossils from the "Age of Fish" in the Devonian Period. This time period came long before there were even dinosaurs, because during the Devonian period the only animals to inhabit dry land were insects. Fish would have been the only vertebrate or back-boned animals to be alive, because fish were the first vertebrates to evolve. The world had yet to see amphibians, reptiles, birds or mammals.
In the Devonian the world was a very different looking place. Notice how much of Europe and North America (which were combined at this point and very much under water) were south of the Equator.
For those of you who like dates, the Devonian was 419.2 until 358.9 MILLION years ago. And just to give you a comparison to when classic dinosaurs roamed the Earth, those reptiles lived 252 until 66 million years ago. It would be over a million years after the Devonian ended before there were any dinosaurs. I only use dinosaurs as my reference point because most everyone seems to have heard of them.
I find it very very hard to imagine how much time a million years is, especially since our human time frame is so short. The end of the Ancient Egyptian era (Cleopatra's death) in 30 BCE was only a little over 2050 years ago. To me the Ancient Egyptian times seem like a very long time ago, so it is hard to comprehend how much time has passed and how many changes have happened since 419 million years ago.
During the Devonian there were all types of things living in the oceans including many fish we wouldn't recognize today.
However, at the very end of the Devonian Era, vertebrate life appeared on land. According to what the fossil record has shown us, the first vertebrate life on land would (most likely) have been some kind of amphibian. Modern amphibians include frogs, toads, salamanders and newts. For a long time scientists have been looking for missing link fossils, those long extinct animals that made the trip onto land and had the traits needed to stay and live on land. In other words, they've wanted to find fossils of animals who were no longer typical fish and could have lead to the evolution of amphibians.
Here's a photo of a frog I took earlier this summer. What makes a frog different from a fish? For the sake of brevity and since this is a blog post not a journal article, I'm going to go very very basic here. Fish have scales, and frogs do not. Fish have fins, and frogs have legs. Fish have gills, and frogs have lungs. For amphibians to appear on land, some types of fish would have had to get rid of their scales, lose their gills, develop lungs, lose their fins and actually grow legs.
All of these are huge changes and would have taken many many many generations to happen.
And once again, for the sake of brevity since this is a blog post, I'm going to focus on legs.
Think about how a fin needs to change into a leg. I found this diagram online in an article in the scientific journal Science. (https://www.science.org/doi/10.1126/sciadv.abc3510) You don't need to be an expert nor have to look at it carefully to see what I mean by a fin turning into a leg.
The fin on the left is a typical fish fin. The fin in the middle is from a fish we call the Coelacanth and then finally there's the leg on a mouse. Notice the typical fish does not have any bones in its fin that relate to frog or human arm bones. The Coelacanth has tiny bones. And in some missing link(s) those bones would have evolved into the arm bones we (including mice) all have: the red humerus, the purple radius and the blue ulna.
And in case you're wondering what a Coelacanth is, here's a photo of a model of one. Notice the fins. It's really clear if you look right behind the head that the side (pectoral) fin has a little arm-like structure before the actual fin. However, the Coelacanth still has the same number and position of fins that typical fish do.
And here's a coelocanth like fish fossils that is in the museum at the park.
Now back to the park. Miguasha is the site where not only lots of Devonian organisms have been found, but also, some of a very special fish. There is a partial skeleton referred to as the prince of Miguasha which is a fish with arm bones like the coelocanth has. But an even more important complete fossilized skeleton was found in 2010 and is referred to as "le roi des poissons" or the king of the fish.
Here is a model of this king of the fish. What makes him so special? First notice how many fins he has. He has 2 in the front and then 2 in the back.
Think of a frog. They have 2 legs in the front and then 2 legs in the back. Notice also how the eyes are on top of the head more like a frog than on the sides of the head more like a fish. And I don't see any gill openings or a gill cover along the side of the head. I'm not certain about this last point I bring up, but the 2 slits behind the eyes could be for breathing in air.
From what ichthyologists now know since finding this complete skeleton in 2010, this fish is the closest missing link to the connection that shows that fish evolved into amphibians.
This find is still being researched, so this fossilized skeleton still has a lot to show us.
The king of the fish in this above model is named Elpistostege watsonii. But there are 2 other important fish fossils found at Miguasha besides the prince and the king. One of those 2 fish is
Miguashaia bureaui which is similar to modern day coelocanths, and the other fish is Scaumenacia curta which has both gills and lungs.
Considering how rare it is for something to actually become a fossil (since most living things would completely decay), and considering how many important fossils were found here, this is a pretty special place. I was actually surprised how small the actual fossil site was also.
Having a degree in biology and having worked in fishery research during my undergrad years, I found this place fascinating. I hope I didn't bore you too much with this post, but I assume that if I did, you would have moved on before you got to this point. 😏
FYI-I don't know why my font changed towards the end of the post, it's not that way in my post before I posted it. Hmmmmm. That's stranger than the fish in this post.
Have a great rest of your weekend.
