Hairy Museum of Natural History

Heterodontosaur Edition

These grumpy looking critters are Heterodontosaurus, the “differently-toothed dinosaur”. Unlike us mammals, who have been packing several different sizes and shapes of teeth into our mouths almost since we were sphenacodonts*, dinosaurs (and most other reptiles) generally made do with only one or two tooth styles, repeated throughout their mouths.

Tyrannosaurus, for example, had pointed, nipping teeth at the very front of its mouth with pointed, tearing teeth further back. Sauropods like Diplodocus had a row of uniform peg-like teeth for raking foliage into their mouths. Even the duckbilled hadrosaurs, who evolved a unique and efficient way to chew their food, had only one type of small, leaf-shaped tooth packed next to hundreds of teeth just like it in massive grinding surfaces.

So a little dinosaur with sharp nipping teeth, large tusks, and a row of closely packed plant-shredding teeth is just a bit unusual.

The shredding teeth (behind the cheeks in this restoration) were most likely used to process vegetation. And the nipping teeth could have worked with the slender beak at the front of the mouth to crop the greenest, freshest bits of leaves and fronds. But what about the large, fanglike tusks? One clue comes from different types of small deer that live today in the forests of Asia and Indonesia. Male muntjacs and mouse deer have sharp, tusklike canines that are used as weapons in fights over females or territory.

Heterodontosaurus seemed well equipped for such face-to-face combat. The heterodontosaur skull has prominent cheekbones that could have been used in shoving matches. The angry stare depicted here comes from a bar of bone that arched over the heterodontosaur eye socket (not unlike that seen in eagles today) that might have helped protect their eyes during scuffles.

In many of today’s tusked species, only adult males bear tusks. The same has been proposed for Heterodontosaurus. At least one tuskless heterodontosaurid skull is known, but it appears to be from a different animal (called Abrictosaurus). So the skull of Abrictosaurus could be female, juvenile, or a member of a heterodontosaur species that got along just fine without any tusks. Until more specimens are found, it is impossible to say whether or not heterodontosaur tusks were strictly a male trait. In this restoration, a slightly more colorful male stands watch over an equally-tusked female, reclining among the arid sandy dunes of an early Jurassic desert.

*The famous sphenacodont Dimetrodon is named for its two different sizes of tooth.

—Matt Celeskey.

File under: Dinosaurs, Jurassic.

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“Spike” is the nickname given to the life-sized bronze Pentaceratops that stands outside the entrance to the New Mexico Museum of Natural History & Science, and one Sunday morning each September hundreds of cyclists pass by his five-horned face as they embark on Spike’s Ride, an annual fundraiser for the NMMNH&S.

Each participant in Spike’s Ride gets all kinds of perks, like free museum admission, discounts at the gift shop, and the chance to sample dozens of chile sauces and stews from Albuquerque restaurants. And every participant gets a Spike’s Ride t-shirt, which features artwork depicting New Mexico’s favorite cycling ceratopsian.

I’ve been able to work on shirt art for the past five ‘Rides, and the challenge of squeezing a Pentaceratops onto a bicycle has yet to get old (the long tail and lack of opposable thumbs are easily overcome, but the ornithischian pelvis definitely did not evolve to rest on a bicycle seat). Just to keep it interesting, the last few shirts have portrayed Spike in some sort of prehistoric predicament based on new displays at the NMMNH&S. In 2003, after we completed our Cretaceous exhibit upgrade, Spike was shown outcycling the Bisti tyrannosaur. Last year, with the opening of the new Jurassic exhibit, Spike cruised beneath the legs of a startled Seismosaurus.

And this year, with the announcement of giant Arthropleura tracks from northern NM, Spike is forced to interrupt a Carboniferous cruise in order to “Make Way for Millipedes.” Click here to load this year’s full t-shirt art in a new window.

Click here for more information on how you can participate in Spike’s Ride. Even if you can’t make it down for the event, less than $20 will help fund the NMMNH&S educational programs, and get you a nifty 5 color tee not available anywhere else.

—Matt Celeskey.

File under: The Day Job.

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Some interesting articles, available online, have come to light with the recent research into sphenacodonts and such:

Sphenacodon Marsh, A Permocarboniferous Theromorph Reptile from New Mexico, a 1916 article by Samuel W. Williston in the Proceedings of the National Acadamy of Sciences.

And a PDF reprint of Case’s 1907 Revision of the Pelycosauria of North America, available as a free download from Arment Biological Press. They also have Samuel Williston’s 1911 American Permian Vertebrates available for a small investment, along with a slew of other titles.

—Matt Celeskey.

File under: Carboniferous, Permian, Synapsids.

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Sphenacodont Edition

With the latest changes to the Hairy Museum’s layout, it seems like a good time to try our own take on what’s become an Internet tradition—Friday animal blogging. And based on the experiences detailed here, our inaugural Dead Animal Blogging will feature those lovable Permian scamps, the Sphenacodonts.

The Sphenacodonts, or “Wedge Teeth” were a very successful group of animals that first evolved around 300 million years ago. Most people are already familiar with at least one member of this distinguished group—the sailbacked Dimetrodon.

Dimetrodon was undoubtedly one of the showiest members of the group, easily identified by the tall sail running down its back, which was likely either used for display or temperature control (or both). In fact, it could be said that the sail really is what makes Dimetrodon, because its close relative, Sphenacodon, is practically identical in every way except that its back has a ridge instead of a sail.

Although they differ in their dorsal decoration, all sphenacodonts have one thing in common: big fanglike teeth. All sphenacodonts were predators—in fact, animals like Sphenacodon and Dimetrodon were the first vertebrates to become large (2–3 meters long) terrestrial predators. Before them, the only carnivores were semiaquatic or small or both. Sphenacodonts created the niche that would later be filled by lions, tigers, and tyrannosaurs.

And if all that wasn’t impressive enough, its a good bet that you’ve got a sphenacodont somewhere in your family tree. The evolutionary line that led to mammals went right through the Sphenacodontia. The big, showy models like Dimetrodon were probably a little too specialized to be on the main branch of mammal evolution, but even the smallest, most conservative sphenacdonts were sharp-toothed predators. Just go back 300,000,000 years and we were all wedge-toothed terrors with big fangs and strong jaws, scampering into a whole new world of limitless potential.

—Matt Celeskey.

File under: Carboniferous, Permian, Synapsids.

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Back at the end of June, I jumped at the chance to dig up some fossils in northern New Mexico with a team of researchers, associates, & volunteers from the New Mexico Museum of Natural History and Science. We set up camp in historic Cobre Cañon, whose rocks date from the latest Carboniferous (Pennsylvanian) through to the Early Permian, which makes the rocks that form the canyon about 300,000,000 years old—a good 75,000,000 years older than the earliest dinosaurs.

During the day we baked under the summer sun, finding and excavating the fossils that had worked their way to the surface after having having been preserved in rock and mud for more than a quarter-billion years. In the evenings around the fire, we looked around the canyon and thought about what today’s dry New Mexico terrain would have been like back then. It was nearly on the equator then, and even hotter. It would have been wetter, too, at least during the rainy seasons when the rivers would rise, heavy with sediments carried down from the Ancestral Rocky Mountains pushing up to the north.

The rivers would haved enriched forests of tree ferns and giant horsetails. A visitor from modern North America would be hard-pressed to find a familiar tree, or a terrestrial vertebrate that would look out of place in a zoo’s Reptile House.

A visitor without the benefit of a few thousand millennia of hindsight might not think much of the vertebrates at all. The invertebrates would have been much more visible, and, in that oxygen-rich world, much larger. Giant, eight-foot-long millipedes would have been the largest animals around, and, to our ancestors’ dismay, they might have even been at the top of the food chain.

Inspired by fossils and conversation, I began a sketchbook of Permocarboniferous studies, to both familiarize myself with this distant world and plan some larger pieces to portray that time. I’ve created a gallery of the sketches here, and will update it with new sketches and finished pieces as time goes by.

I’d encourage anyone interested in this time and place to look into The Nonmarine Permian Symposium being put on this October at the NMMNHS.

I’m indebted to Dr. Spencer Lucas for setting up the trip, inviting me along, and encouraging the artwork. NMMNHS Preparator Larry Rinehart provided excellent conversation, enthusiasm, and showed remarkable understanding when my initial attempts at quarrying met with mixed success. Dan Chaney gave me a crash course in the relevant paleobotany, and Susan Harris patiently taught me how to see Paleozoic fossils. Josh Smith, Kevin Madalena, and Paul Sealy all graciously shared their thoughts and expertise in the field.

—Matt Celeskey.

File under: Carboniferous, Permian, The Day Job.

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