The size of this thing is an indication that Earth’s atmosphere was different in ancient times, with a higher oxygen content.
Insects don’t have lungs. Oxygen gets to cells inside their bodies through tiny tubes going through their bodies, which creates an upper limit on size in the current atmosphere.
https://askabiologist.asu.edu/how-insects-breathe
https://en.wikipedia.org/wiki/Arthropleura
—
Oxygen may not have accounted for the size.
—
Perhaps gravity was less?
Yup.
A Chicxulub-sized event rings the planet like a bell, any fault that is near its critical strain is apt to let loose.
Doctors and coroners have a term, coup contrecoup, that means damage to the opposite side of the brain from where the skull was struck.
Imagine you are standing on the spot exactly on the opposite side from the strike. The shock waves race around the globe and come together (focus, if you will) right under your feet!
On a lower gravity bodies such as the moon, big impacts have delivered sufficient coup contrecoup force to jet material off into space.
I don’t doubt that nearby magma would be squirted up through the resulting shattered bedrock.
Add to that the fact that Chicxulub was a shallow water strike and the surrounding sea formed a wall around the white hot crater as it attempted to flood in. It was like a 120 mile wide rocket nozzle jetting vaporized seawater and any entrained atmosphere into space. Global atmospheric pressure and sea level drop permanently. As the crater was quenched, the force of the boiling reduced, and the remaining flood of sea water and air steam-cleaned half the planet.
It was a bad day.
On land nothing larger than a house cat survived. I suspect all the surviving animals were burrow dwellers or nesters, animals already used to breathing lower oxygen content than their larger peers. The thinned atmosphere was a final insult to the bigger surface dwellers.
They all died off as a result of Globul Schwarming.
We need to get those bugs back. They are bioweapons against lefty liberals!
also the air pressure was much higher.
Study hyperbaric therapy. You will know one reason why we used to live longer, and animals and plants used to be bigger.