Elk are basically a big deer. Larger, maybe a bit thicker skulls, but not as heavy bone wise, as a bear skull. But I've never shot a bear, and only seen their skulls in displays, so I'd defer to GJM on that matter. I'll be honest and say that I'm surprised that .45 bullet didn't penetrate more, and just keep going. But I think it just proves the saying that rifles tear shit up, and handguns poke holes in things.
"The one thing that's consistent when it comes to shooting real live critters is how inconsistently bullets perform. " -- There is much truth in this statement.
I've seen a mule deer shot with a 250gr Nosler Partition Gold bullet from a .338WM run 1/4 mile or more down a canyon. Following it up we found a large pile of organs and intestines where the deer turned around some brush, and they apparently spilled out... the 6-8" hole in the off side. It was a quartering-to shot that was a bit far back, and IIRC, only got one lung. How it ever made it that far, I have no idea. That deer just didn't want to die. My buddy found a lucky rabbits foot within a couple feet of where his deer finally fell. I think he still has it.
On the other hand I've had some deer and antelope that took a 62gr Gold Dot to the boiler room that acted like they were hit with a far larger caliber. Dead within feet of where I shot them.