Episode 176 is all about Stygimoloch, a dinosaur with awesome spikes around the back of its head which some think is a juvenile Pachycephalosaurus.

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In this episode, we discuss:

News:

The dinosaur of the day: Stygimoloch

Phonetic: Stij-e-mol-ok.

An official Snapchat post for Jurassic World Fallen Kingdom confirmed that Stygimoloch will be in the movie

Pachycephalosaurid that lived in the Cretaceous in what is now the U.S. (found in the Hell Creek Formation, Ferris Formation, and Lance Formation)

Several individuals have been found

Described in 1983 by Peter Galton and Hans-Dieter Sues

Type species is Stygimoloch spinifer

Name means “Styx demon” and the name comes from the river Styx, which ran through the underworld in Greek mythology, as well as Moloch, the name of a Canaanite god, because it looked so bizarre

Herbivore that may have been about 10 ft or over 3 m long

Lived at the same time and place as Tyrannosaurus and Triceratops

Had an unusual looking skull

Had clusters of spikes on the back of the skull, with one long, central horn, surrounded by 2-3 smaller horns

Had short hornlets on its nose, and a pair of large backward pointing spikes on the back corners of its skull (not sure what it was used for)

Had a relatively small, flattened dome, so probably did not do much head butting

Skull ornamentation may have been for display, defense, or for shoving matchings (locking horns, like deer), or to inflict pain when butting flanks

One article referenced a Stygimoloch skull that was on auction in New York a few years back, but couldn’t find out what happened to it, or who ended up buying it

Part of a controversy

In 2009, Mark Goodwin and Jack Horner published a paper arguing that Pachycephalosaurus, Stygimoloch, and Dracorex were all Pachycephalosaurus, representing a growth series (proposed the idea at SVP in 2007). They considered Dracorex to be the juvenile, though Bob Bakker and others in 2006 had determined the Dracorex specimen to be an adult, based on the ornamentation on its skull and fused bones

Also, Williamson and Carr in 2002 agreed with Goodwin and others from a paper in 1998 that found these three taxa to be distinct based on horn size and head shape (Pachycephalosaurus had a larger, more round skull, Stygimoloch has longer horns and a narrower dome)

Dracorex (named in 2006) did not have a dome, had large horns, and large temporal holes in the skull

Horner argued that we don’t know exactly how big or how old any dinosaur species could get, and that juvenile skulls can look very different from adult skulls

The idea for lumping the three together was that long, sharp horns grew out of the back of the head for the first half of the dinosaur’s life, and then the horns were reduced as it reached maturity, and as the horns shrunk, the flat forehead grew and expanded into a solid dome. Also, the large openings in the skull closed when it aged. Dracorex would be a half-grown juvenile, Stygimoloch would be three-quarters grown, and Pachycephalosaurus would be an adult

Covered Pachycephalosaurus in episode 93

Bob Bakker said he has studied horn and dome growth in modern animals that butt heads and none of them show a reversal of horn development (same goes for well known horned dinosaurs, though Triceratops horns do grow larger and its skull changes a lot during growth). He also said they looked at a juvenile Pachycephalosaurus skull, about 2/3 the length of an adult skull, and that it had a very similar shape to the adult Pachycephalosaurus skull, with small horns, no holes in the skull, and a large dome. The skull is similar in size to the Dracorex skull found, but the two skulls look very different

Bob Bakker said he and a team compared Stygimoloch specimens with Dracorex and found their skulls were similar in size, so the differences in their skulls weren’t due to age differences (ontogenetic development)

He also said these pachycephalosaur dinosaurs (including Pachycephalosaurus, Stygimoloch, and Dracorex), probably all grew like Triceratops, where bumps and horns got bigger as they aged, but not growth reversal

Pete Larson posted photos of the Stygimolch he was working on between October 2016 and June 2017. Said he found enough differences in the skull to make Stygimoloch a distinct genus (though couldn’t find a paper of his findings, maybe not ready?) He found a pathology on the “longest” horn on the left squamosal (bacterial infection), stapes (bone in the middle ear) the first recognized disarticulated vomer in a pachycephalosaur (small thin bone that separates left and right nasal cavities), and elements of the scholortic ring that was around both its eyes

A comment in one of the papers said there’s a complication, in that a pachycephalosaur skull found in the same quarry where Sue the T. rex was excavated was about the same size as the Dracorex and Stygimoloch skulls found, with a dome size that was in the middle of the two (could show the ontogeny). But it short spiked nodes on the back of its head instead of long spikes, similar to adult Pachycephalosaurus. This could mean the long spikes vary within Pachycephalosaurus (seems to be variation in Pachycephalsaurus squamosal) or they are a distinct feature of Stygimoloch. Also, Pachycephalosaurus and Stygimoloch specimens were found in different stratigraphies, though this type of data was not really collected for historical Pachycephalosaurus specimens (would need more data)

Nick Longrich and others published a study in 2010 that suggested all flat-skulled pachycephalosaurs were juveniles

Need more fossils

Quote from Bob Bakker: “The key to accurate interpretations of a fossil species is to be prepared to be surprised; do not assume that all the ancient creatures and ecosystems fit neatly into the ecological typecasting of modern species.”

Fun Fact:

Paranthodon (Pah-RAN-tha-don) africanus was the first dinosaur discovered in Africa.

This episode was brought to you by:

TRX Dinosaurs, which makes beautiful and realistic dinosaur sculptures, puppets, and exhibits. You can see some amazing examples and works in progress on Instagram @trxdinosaurs.

Enter to win a TRX Dinosaurs-made 1:1 scale Velociraptor sculpture. It’s open to anyone in the US or Canada (except Quebec) ages 18 and older to win. Complete rules are at https://iknowdino.com/velociraptor-sculpture-sweepstakes-official-rules

This week’s link to enter is http://bit.ly/Velociraptor176

And by the Royal Tyrrell Museum, which is located in southern Alberta, Canada. Right now they are hosting their free-to-attend Winter speaker series (also on YouTube). More information can be found at tyrrellmuseum.com.