Which of Today's Animals Lived Alongside Dinosaurs?

When the non-avian dinosaurs died out, a lot of other animals went with them -- but some sturdy species survived. Learn how they evolved and thrived in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/environmental/earth/geology/dinosaur-contemporary.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brainsty a production of iHeartRadio, Hey Brainstuff Laura
voleban here. According to the prevailing scientific theory, non avian
dinosaurs met their dramatic end after an enormous asteroid hit
the Earth near what's now Mexico about sixty six million
years ago, give or take. This mass extinction, known today

(00:26):
as the Cretaceous paleagen or the Cretaceous Tertiary extinction, event,
caused a huge amount of debris like dust and ash
to fill the atmosphere. This in turn created what's called
an impact winter, in which life giving light from the
sun was blocked. A plant life couldn't photosynthesize and thus
died off. The oceans acidified, the food chain was disrupted,

(00:49):
and some seventy to eighty percent of all life on
the planet was wiped out. It was the literal end
of an era, the Mesozoic to be specific. The mighty
non avian dinosaurs were perhaps the most famous of the
life forms that died out post asteroid, but many others
became extinct as well. These included aquatic reptiles like plesiosaurs,

(01:12):
the first vertebrate animals to fly by flapping their wings.
The pterosaurs, the vast numbers of oceanic invertebrates, and some
ninety percent of algae species. Life was never the same,
but some types of animals weren't hit nearly as hard.
At least a few members of about eighty four percent
of marine families and eighty two percent of land vertebrate

(01:34):
families made it through. So many life forms survived the
event that it would take way more than a podcast
episode to describe them all, and many of the animals
have descendants that still live today. Some of these species
look a lot like their Mesozoic counterparts. Others have changed
quite a bit, including birds, which are the descendants of

(01:55):
avian dinosaurs that managed to survive the extinction event. So
aside from birds, which of today's animals walked, crawled, slithered,
or swam alongside dinosaurs. Dinos lived on Earth during the
Mesozoic Era, which lasted from two hundred and forty eight
to sixty six million years ago. Geologists divide the Mesozoic

(02:18):
Era into three periods, from longest ago to most recent
the Triassic, Jurassic, and Cretaceous. Dinosaurs became more diverse as
time went by, and at the same time, other life
forms developed and became extinct. If the Mesozoic era was
the age of the dinosaurs, the next era, the Cenozoic era,

(02:39):
was the age of mammals. The first mammals were monotremes,
or mammals that reproduce by laying eggs. Mammals in general
are common today, but only three monotrem species still exist.
These are the duckbilled platypus and a couple of echidnas,
and you can see our past episodes on both of those.
Many types of reptiles species die during the extinction event,

(03:02):
but some snakes, lizards, and crocodilians persevered. Crocodilians have been
on the planet for about two hundred and forty million years.
There are twenty three crocodilian species today, including alligators, crocodiles,
and caymans. Mesozoic crocodilians were generally larger. Another prehistoric order
of reptiles is the Saphenodontians. Today there is one living sphenodon,

(03:27):
the Tuitara, a small, spiky, gray green reptile that lives
in New Zealand. The most likely evolutionary origin for these
reptiles is that in the distant past they arose from amphibians.
Very large amphibian species lived before and during the Mesozoic.
These are gone today, but in their place three primary

(03:50):
types of amphibians survived, frogs and toads, nuts and salamanders,
and celions, which are animals that mostly look like worms
but have skeletons. But not. Every family that lived during
the Mesozoic has only a few descendants left today. All
modern insect groups existed before or arose during the Mesozoic era,

(04:13):
and perhaps most notable of these is the usocial bee
of bees that live in colonies. Most likely these evolved
along with flowering plants, which started to develop in the
Cretaceous period. Without this code development, we humans wouldn't have
honey or a whole host of bee pollinated fruits, vegetables, nuts,
and grains today. Ferns and conifers were also widespread during

(04:36):
the Mesozoic era, and ferns actually experienced a huge population
spike after the extinction event. Then there's Gingo biloba. If
you see one of these trees but which has fan
shaped green leaves that turn golden yellow in the fall,
you're looking at a plant that's almost identical in appearance
to its Mesozoic ancestors, but the oceans were particularly devastated

(04:59):
by the event. Dinosaurs were not particularly aquatic, but there
were lots of sea dwelling animals during the Mesozoic. The
aforementioned pleasyosaurs were long necked, finned reptiles. Think of the
Lochness monster and you've got a pretty good idea of
what one looked like, though as far as science knows,
they did not survive. Other marine life forms experienced heavy

(05:21):
losses but eventually recovered and went on to thrive and diversify.
Those include the echinoderms like sea stars, sea urchins, and
sea cucumbers, plus mollusks with their soft bodies and hard shells.
The clams, snails, lobsters, crabs, and shrimp that make their
way to the mouths of oceanic carnivores, and the plates

(05:43):
of hungry humans come from predecessors that, one way or another,
lived through the extinction event. Sharks also inhabited the world's
oceans long before the first dino made its way across land,
and they're among the most well known oceanic predators today,
but a few of today's species are the only remaining

(06:03):
examples of long extinct marine families. The most famous may
be the Sila camp, the last known marines sarcopterrigian, which
were lobe finned bony fish. There are plenty of other
Sarcopterygians in the world, though. All of the four limbed
vertebrates on the planet, from turtles to tucans to humans,

(06:25):
arose from common ancestors that diverged from the sarcoptigians long
before the Mesozoic era. Scientists thought selacanths were extinct until
the nineteen thirties, so hey, it's possible that researchers may
one day find other remnants of Mesoic life out there.

(06:48):
Today's episode is based on the article which of today's
animals lived alongside dinosaurs on how stuffworks dot Com, written
by Tracy V. Wilson. Brain Stuff is production of by
Heart Radio in partnership with how Stuffworks dot Com, produced
by Tyler Klang. For more podcasts from my Heart Radio,
visit the iHeartRadio app, Apple Podcasts, or wherever you listen
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