Smithsonian.com

A restoration of Gigantspinosaurus. Art by Conty, image from Wikipedia.

Stegosaurus was a weird dinosaur. We’ve known that for well over a century, but, as Darren Naish has often pointed out, Stegosaurus was strange even compared to its Jurassic relatives. The dinosaur’s arrangement of broad, alternating plates is a departure from the arrangements of smaller plates, back spikes and accessory spines seen on many other stegosaurs, including the perplexingly well-armed Gigantspinosaurus sichuanensis.

Ornamented with a double row of short, narrow plates along its back, the roughly 160-million-year-old Gigantspinosaurus generally resembled other stegosaurs from Late Jurassic Asia, such as Tuojiangosaurus. But, as you might be able to guess from the dinosaur’s name, the feature that immediately sets Gigantspinosaurus apart from similar species is a enormous hooked spine that jutted out from behind the shoulder blade. These striking spikes were found close to their life position on the first skeleton of this dinosaur to be found–erroneously attributed to Tuojiangosaurus, before being redescribed as Gigantspinosaurus in 1992–although their exact orientation isn’t entirely clear. Did the shoulder spikes curve straight backward, or were they tiled slightly upwards? And, more significantly, how did such prominent ornaments evolve? No one knows.

As yet, we know relatively little about the natural history of Gigantspinosaurus. The dinosaur has a name, and skin impressions have helped researchers restore what the stegosaur looked like, but many aspects of the spiky herbivore’s biology remain mysterious. In the grand scheme of stegosaur evolution, though, the ornamentation of Gigantspinosaurus has sometimes been taken as evidence that similar forms had shoulder spikes. In addition to paired spikes along its tail, the Late Jurassic stegosaur Kentrosaurus possessed an extra pair of spikes along its side. These were originally placed over the hips, but, due to the discovery of Gigantspinosaurus, some researchers have argued that the spikes truly belong at the shoulders.

Frustratingly, paleontologists have yet to find a Kentrosaurus skeleton with side spikes in place. But the discovery of Gigantspinosaurus doesn’t necessarily mean that its cousin Kentrosaurus had the same arrangement. Among stegosaurs, the two genera were relatively distantly related, and it’s entirely possible that more than one side spike arrangement evolved. As paleontologist Heinrich Mallison has argued, the hips of Kentrosaurus seem to possess areas where the spikes could have articulated, and this arrangement would be consistent with the dinosaur’s ornamentation pattern–small plates at the front give way to spikes along the stegosaur’s back and tail. Indeed, the side spikes on Kentrosaurus more closely resemble the same structures along the dinosaur’s back and tail and the shoulder spike of Gigantspinosaurus. If Kentrosaurus had plates up front and serially homologous spikes along the back, then why shouldn’t the hip spikes remain a reasonable hypothesis? Together, Gigantspinosaurus and Kentrosaurus might represent different alternatives in the stegosaur armory.

When it came time to pick a 2011 Christmas tree ornament, the choice was clear - I needed a dinosaur. Photo by the author.

When it came time for my wife and me to pick this year’s Christmas ornament, there was no question what it had to be: We needed a dinosaur. After all, this year we left New Jersey to settle in the fossil-rich state of Utah, and so it was only appropriate to celebrate our successful move with a dinosaurian decoration. We settled on an Allosaurus pendant from Dinosaur National Monument. This Late Jurassic theropod—one of my favorite dinosaurs—is the official state fossil of my new home, and my first visit to the geologically wonderful national park two years ago was what inspired me to head west. Perfect.

But my wife and I aren’t the only ones to adorn our tree with dinosaurs. Friends have been sending me snapshots of their own tannenbaum dinosaurs over the past few weeks, and yesterday I put out a call for more merry Mesozoic ornaments. I was not disappointed.

Photo by Michael Barton.

Long-time reader Michael Barton tweeted this Cretaceous scene wherein a Triceratops faces off against a Tyrannosaurus. C’mon, guys—don’t you know that this is the time of year for peace on earth and goodwill towards dinosaurs?

Photo by John Pomeranz.

Among other dinosaurs, John Pomeranz nestled this particularly colorful Triceratops among the branches of his Christmas tree. With no predators around, this dinosaur clearly doesn’t need camouflage.

Photo by Aline McKenzie.

Even though pterosaurs aren’t dinosaurs, I couldn’t say no to this photo of one of the flying archosaurs decked out in a Santa hat, sent by Aline McKenzie.

Photo by Helen Fields.

What’s flashier than a Stegosaurus? A sequin-covered Stegosaurus ornament, of course. Thanks to freelancer Helen Fields—who has written about dinosaurs for Smithsonian herself—for this one.

Photo by Matthew Cobb.

Those sparkly stegosaurs sure do get around. This one, tweeted by Matthew Cobb, had been shuffling around the Christmas tree since 1986.

Photo by Twitter user @scurvygirl.

A vintage theropod reaches out from @scurvygirl’s Christmas tree.

Photo by Twitter user @ArtfulMagpie.

Given their probable diet of conifers, I’m surprised there aren’t more holiday sauropods in the mix.  Fortunately for us, though, @ArtfulMagpie has shared this lovely pink sauropod from her Christmas tree. She says “He was a brontosaurus when I got him as a child. I suppose he’s an apatosaurus now!”

Photo by Alexandra Witze.

A cute little Triceratops lives in Alexandra Witze’s Christmas tree, but where there’s Triceratops…

Photo by Alexandra Witze.

…Tyrannosaurus is not far behind. Though, based upon the lipstick, I’d say this one is ready to make love, not war.

Photo by Marc Vincent.

Of course, the fellows at Love in the Time of Chasmosaurs have unique dinosaur decorations, too. These two dinosaurs, sent by Marc Vincent, are out for a nice winter sleigh ride…

Photo by David Orr.

… and LITC founder David Orr has this fuzzy Spinosaurus, crafted by his wife.

Photo by Flickr user cali4niadreamn23.

Even museums have jumped in. This tree—inhabited by many origami dinosaurs—is on display at the American Museum of Natural History in New York. I think this tree wins the category of “most dinosaurs per square inch.” Thanks to fellow science writer Alexandra Witze for the tip about this one.

Do you have holiday dinosaurs in your home? Don’t hesitate to send them to us at dinosaursightings@gmail.com. We will create an end-of-the-year roundup for whatever other dinosaurs might appear. Until then, all of us here at Dinosaur Tracking want you to wish you warm and happy holidays, wherever you are.