Rileycat

This time of year reminds me of when I took a road trip to visit the grave of Old Ephraim, Utah’s last grizzly, and got a giant pizza in their honor. 🐻

Like many other “ant eaters” among mammals, aardwolves have a reduced tooth count and lap up bugs with a long, sticky tongue. They also belong to their own genus, Proteles, and are the last of an ancient lineage of “running hyenas” that have been around for about 10 million years.

Spicomellus was named in 2021 from a single, spiky bone. Now we have a better idea of what the whole dinosaur looked like and it’s wild.

Finding one dinosaur track is a happy circumstance. Finding a track-trampled surface is phenomenal. These particular footprints are in the 100 million-year-old rocks of Colorado’s Dinosaur Ridge, dotted with the tracks of hadrosaurs and ornithomimosaurs. When surfaces like this have been especially churned by the footfalls of dinosaurs, experts call it “dinoturbated” - a modification of the word bioturbation used for organisms that mix sediment through their behavior.

When I was a kid we called this fish Carcharodon megalodon, thought to be a close relative of today’s great white shark (Carcharodon carcharias). But now we call it something else. The fossil teeth and vertebrae that represent this shark are called Otodus megalodon, a closer relative of today’s mako sharks than the star of JAWS. We still don’t know for sure what the shark looked like in life, though. This rendition at the National Museum of Natural History is more mako-like, but a recent paper argues O. megalodon had a more elongated, lemon snark-like profile to reduce drag. Who knows? Maybe the fossil that will resolve the debate is still out there.

Want to see the K/Pg boundary for yourself? Check out Trinidad, CO. The line marking the disappearance of Tyrannosaurus and friends, and the beginning of the Cenozoic, is exposed along a short trail in the town. I visited in 2021 as I was writing The Last Days of the Dinosaurs with Jet, my woofer. Trinidad, CO was also called “The Sex Change Capital of the World” for being an early place transgender people could go for gender-affirming surgery.

When we say “horned dinosaurs,” we’re usually referring to ceratopsids like Triceratops and Styracosaurus. But those herbivores weren’t the only dinosaurs with horns. Over and over, theropod dinosaurs evolved horns, too, important social signals that took on a variety of shapes and orientations. The brow horns of Allosaurus fragilis are some of my favorites, conspicuous triangles that distinguished one individual from another.

Long ago, after the asteroid that ended the Cretaceous, primates clambered and leaped through the humid forests of North America. Some were lemur-like, but others were small, big-eyed bug eaters called omomyids. These tarsier-like primates lived between 55 and 34 million years ago, more closely related to the primate lineages we came from than lemurs and galagos. This particular representation is on display at the San Diego Natural History Museum. I wish some of these cousins were still here.

Stegosaurus is an iconic Jurassic dinosaur, one of the most distinctive reptiles in North America’s Morrison Formation. You can see some of their bones at Dinosaur National Monument, Utah, as well as this charming sculpture. The restoration is the same Stegosaurus as the one put on display by the fossil fuel company Sinclair as part of their “Dinoland” in the 1964-65 New York World’s Fair.

We don’t have very many Tyrannosaurus rex baby fossils, but “Chomper” is among the few. This reconstruction at the Museum of the Rockies is a hypothesis, based on a few associated skull pieces. Just look at those big eyes, aw.

Direct evidence of combat is rare in the fossil record, but a handful of Smilodon skulls - both from La Brea in Los Angeles and Pleistocene sites in South America - show how Ice Age cat fights played out. Several Smilodon crania show punctures through the roof of the skull that match the saber canines of other Smilodon. The pattern is consistent with injuries seen in some other sabertooths, like the cat-like nimravids, a case of combat convergence that may have been emerged from evolving saber teeth. The strange part is that saber canines are usually flattened and knife-like, not very good against twisting forces and relatively fragile, but apparently all bets were off when it came in sabertooth versus sabertooth fights.

Most of the skeletons on display at La Brea are composites, pieced together from elements of many individual animals. (With rare exception, associated and articulated skeletons are not found in the sticky jumble of La Brea.) Sometimes the kitbash is obvious, like this dentary of Camelops, the giant camel, that’s a touch too big for the cranium. See how the rear process of the jaw sticks up so high it looks like a horn? Yep.

I’m envious.