Hi everybody! My name is Ray and we're here
with the Greater Cleveland Aquarium getting
ready for Fin Fest and getting excited about
prehistoric sharks. Where are we right now,
Caitlin? Well, Ray, you're at the Cleveland
Museum of Natural History in the Vertebrate
Paleontology Department and we're going to
talk about some of the sharks that lived in
Cleveland 360 million years ago. Wow! That's
impressive. I didn't realize there were sharks
here that long ago. I know. And they weren't
in Lake Erie there was actually an ocean here
at the time and there were sharks all over
the place and there was this giant creature
right next to us. This is Dunkleosteus. That's
quite a set of jaws on that guy. Is this a
shark? No. Dunkleosteus is not a shark. Dunkleosteus
is a arthrodire or an armored-jawed fish that
are now extinct. They went extinct at the
end of the Devonian Period like 360 million
years ago. And your turtle looks a bit scared
of it. That's definitely a bigger thing than
he's ever looked at before in our collection.
So, we're talking about this not being a shark
but he clearly was a predator, right? He's
got some pretty gnarly teeth there. Yeah.
It was a predator. It was probably one of
the biggest predators at the time. It was
actually probably going around and eating
sharks. There is a little bit of controversy
about whether or not these are actually teeth.
They may just be bone that they sharpened
and then acted like teeth. Oh, interesting.
That actually changes up differently than
sharks now that have teeth that are not bone.
That's pretty much the converse. Yeah. And
we have some sharks that have teeth and we're
going to show you some right now. Awesome.
Let's go look around. One of the most common
sharks that we find from the Devonian Period
here in Cleveland is Cladoselache and this
is the jaw of Cladoselache and you can actually
see all of the teeth here and you can see
the replacement teeth as well. You can see
the actual rows of teeth preserved in the
fossil. Yeah. So that lines up with our modern
sharks. Sand tigers, which are these bigger
teeth I brought with us, that's the largest
of species of shark on-site [at the Aquarium]
and you can see an entire row of teeth that
came out of one of them. They are always losing
and they're always producing new ones behind.
That's really cool. We can see that in the
fossil record. How big is this shark? Oh,
sand tigers, they'll get about 8 foot to 10
foot long and the record sizes are going to
be about 12 foot or so. Wow. I think Cladoselache
was on like around that big so their teeth
are not that much smaller but they are definitely
smaller. That's a little bit more on par with
a smallest species of shark at the Aquarium
which is our brownbanded bamboo shark. He's
only about that long. Okay, so that sounds
a little bit more like Cladoselache. Okay,
so were these guys bottom-dwelling or were
they ocean swimming? That's a good question.
I don't know and I don't know if anybody does
know. Um, but they were definitely little
predators that were swimming around in the
ocean a the time. Although they were probably
getting eaten by Dunkleosteus more than they
were chewing on Dunkleosteus. That size difference
between them, I can see that. I mean, we do
find evidence of sharks that have been chewed
on. You've got another tooth over here. What's
that one from? So this is from Ctenacanthus,
which is another shark that we find from the
Devonian Period in the Cleveland shale. It
is a little bit bigger than Cladoselache and
we don't find it as often as Cladoselache
but we do find a lot of the teeth. It caught
my eye because the tooth is very similar to
our sand tiger teeth in the fact that it tri-cusp,
meaning that it has 3 points to it. With modern
sharks, that's one of the ways we identify
them. I am guessing it's the same for you
guys with fossil records, that you use different
shape mechanisms for identification? That's
kind of neat that they have a similar structure.
That's interesting. Any idea why that is a
thing? With sand tigers, it's based on feeding
behavior. These guys ... all these long, sharp,
spiky teeth are good for grabbing and basically
spearing their food and then they kind of
gulp it down whole versus slicing it up with
more slender teeth like I imagine might have
been what our Megalodon would have, yeah?
I guess so. I know that when we look at Cladoselache
and Ctenacanthus we do find whole prey preserved
in their stomachs sometimes too, so I think
it's similar that they would swallow them
whole but I have a feeling that Megalodon
was pretty chompy with these teeth. I think
so. We have some sandbar teeth here and it's
a very similar, smaller, but similar structure
to it with very slight serrations on the edges
much like steak-knife-like where it's going
to slice through its food and take bites and
chunks. Interesting. How big are those guys?
These sandbars are around 6 foot or so but
they'll max around 8 foot. And they're your
more stereotypic gray, sleek, jet fightery
sharks, you know? So this is a specimen of
Cladoselache and these specimens are so well-preserved.
We find soft tissues preserved, we can see
the fins and we can see the whole soft body
outline. These are preserved in concretions.
So unlike the big fish that we were talking
about which are found in shales, these are
normally found in big rocks essentially in
the shale and when you break it open there's
a shark [fossil] inside. What's interesting
about them too is that they're always preserved,
well, not always, but the majority of the
time they're preserved ventral side (or tummy
side) up, so we don't get to see the dorsal
fin or the dorsal spine. We know that these
also had dorsal spines although we do find
them separately. This is Cladoselache and
I am going to point out some of the cool features
on this specimen. Here we have the sclerotic
ring, which is the bony eye. You're saying
that's not a thing? That's not something that's
transitioned, to my knowledge, to modern sharks.
My experience with sharks, anyway, the ones
I've worked with . . . that's not a structure
we find in those animals. Interesting. So
we see that in Dunkleosteus, Dunkleosteus
also has that eye, and we also see it in birds
and reptiles a lot. That's really interesting
that you haven't seen it in modern sharks.
So #5 here is showing the Meckel's cartilage,
or the gill arches, which are preserved which
is really rare for a fossil record. And then
we have the fins. So your fins here match
up to modern sharks and modern fish. We've
got 2 paired ones, a pectoral and a pelvic,
so think shoulders and hips on humans, and
then you've also got the singular ones of
the anal fin and the caudal fin (which is
the tail fin) and then your dorsal fin would
be upside down in the table right now. So
that's really cool that that structuring and
general body formation and shape is still
prevalent. That's super cool. It's a shame
that we can't see the dorsal fin but what
we can see here marked by this #7 here is
stomach contents. You can see all the little
sparkly bits. Those are actually fish scales.
This was basically the shark's last meal before
it died. Yeah. I can see those. You move a
little bit and you can see those reflecting
the light in the room. Exactly. This is Cladoselache
and this is a model of Cladoselache so you
can see about its size. One of my favorite
things about this model is that its teeth
were actually based on one of our specimens.
Correctly modeled. Yeah. Very nice. Now, with
the soft tissue preservation. I've always
learned that with cartilaginous fish you don't
get a lot of that occurring typically. Your
Megalodons it's just teeth and we don't actually
find any bits and pieces otherwise. Is that
very unique to the Northeast Ohio area? This
type of preservation is really unique, just
generally in the fossil record it's unique.
We call that a Lagerstätte, which is where
you find exceptional preservation so you find
things like soft tissues, stomach contents,
hair or feathers, things like that preserved
as a fossil. This is 1 of only 2 Devonian-aged
Lagerstätte in all of North America. Wow!
Super rare then. That's awesome. Yeah, really,
really rare. And you guys have examples like
these up on the main floor to have guests
come and look at? Yeah. We have shark [fossils]
up on the main floor and a bunch of shark
spines so you can see what those look like
and we also have Dunkleosteus of course and
a lot of other arthrodires too. Cool! So guys,
come out here to Cleveland Museum of Natural
History, learn about where the sharks came
from, learn about these prehistoric guys and
then come see us for Fin Fest and see the
real deal live ones at the Aquarium.
