R.I.P, Paul S. Martin

I recently learned of, and was saddened by, the death of one of my favorite paleontologists, Paul S. Martin, originator of the Overkill Hypothesis. I had hoped to meet him one day. Sadly, this will now never happen.

He wasn't just important for his bold theory, however. The University of Arizona sums up his life simply, and elegantly:

Paul's work bridged ecology, anthropology and paleontology is a way that had never been done before. He added deep time to ecological thinking, put prehistoric humans alongside now-extinct animals, and gave paleontology an environmental relevance it hadn't previously had. Paul was always a good friend and will always be my favorite paleontologist.

He will be missed.

Besides The Dinosaurs

I'm currently taking an undergrad class on the Mesozoic, that focuses on dinosaurs. I don't really have anything against dinosaurs; they were my childhood gateway into science, and will always hold a special place in my heart (especially the sauropods and pachycelphalosaurs).

But the downside to dinosaurs is that their allure blinds us to the amazing diversity of animal life in the Mesozoic, and overshadows other, equally cool creatures (some of whom are themselves mistakenly identified as dinosaurs in pop culture).

Take, for instance, the crocodiles.

I'd always known that crocodiles' lineage could be traced back to the early Mesozoic. But, like a lot of folks, it never really occurred to me to think of crocs as anything other than, well, crocs as they presently exist.

But boy, was I wrong! I was reminded a few weeks ago that crocs and their relatives were astonishingly diverse during the much-lauded "age of dinosaurs," particularly early on, during Triassic time... even producing herbivores! So, among my many other lines of paleo-reading, I've been checking out the croc family, properly known as the Crurotarsi.

I now have a crush on Crurotarsi, and I'm not alone. Susan Drymala, who apparently has my dream job, maintains a neat blog dedicated to the forgotten archosaurs.

Crurotarsans may just supplant the pterosaurs as my favorite Mesozoic animals. Not least because there are few things cuter than a living, baby croc.

Terrible Head: The History Of Your Teeth, Part V

First, a refresher, an apology and a slight correction. As school starts to consume my life again, my work here has started drifting to the back-burner. I'm sorry about this, but fair warning: it'll probably be the dominant pattern for the next 16 weeks.

Since I've picked up a few new readers in the last couple of weeks -- hello! :) -- here are some links to the first four parts of this series.

Part I
Part II
Part III
Part IV

And now, the slight correction: at the end of the previous article, I said that the pelycosaurs were followed by the dinocephalians; while true, this isn't as precise as it should have been. The dinocephalians were only one group (albeit among the earliest) of therapsids, the great collection of animals originally defined as "mammal-like reptiles," and who ultimately include actual mammals, as well. (Yep, you and your dog, too, are therapsids).

I suspect I made this slip because I'm enamored of the name dinocephalian, which means "terrible head," and couldn't resist using the inherent double entendre potential in a title. So, I did it anyway.

The therapsids were an amazingly diverse group of protomammals who came to dominate all terrestrial ecological niches from the mid-Permian to end-Permian times. They include one of all-time my favorite prehistoric beasties, the Gorgonopsids, and arguably one of the ugly-cutest creatures in the fossil record, Tetraceratops insignis.

Dmitry Bogdanov's reconstruction of ugly-cute T. insignis.

No single blog post could do justice to all the Permian therapsids, but T.  insignis is a good place to start. She is likely a transitional form between the sphenacodontid pelycosaurs and the later, more-advanced therapsids who weathered the end-Permian extinction and eventually became mammals [though this is an unsettled question; Laurin & Reisz (1996) argue that she was a full-fledged, though primitive therapsid; while Connor & Sidor (2001) classify her as a sphenacodontid].

Tooth-wise, T. insignis had a couple of important innovations that brought her and her descendents closer to true mammalian heterodonty.

First, she appears to have had only one canine-like tooth on each side of her upper jaw, giving her a single pair. Previously synapsids often had multiple pairs of caniniform teeth. Secondly, she had one large pair of pre-maxillary teeth, with the rest being relatively small and uniform. This tooth pattern brought her line one step cloer to the mammalian pattern of incisor-canine-premolar-molar, and distinguished her from contemporary synapsid species like Haptodus, a primitive sphenacodontid related to the mighty Dimetrodon, who sported two pairs of canine-like teeth, uniform pre-caniniforms and post-caniniforms that were graded to smaller sizes and non-specialized.

T. insignis, like A. florensis before her, is very likely on your direct family free. She is thought to have evolved in a dry upland environment, well away from the moist, marshy areas favored by the pelycosaurs. Thus, she was resistant to fossilization, and we have very little to work with.

Her descendents, the aforementioned, naughtily-named dinocephalians, radiated and diversified in the mid-Permian, evolving both herbivores and carnivores with diverse sets of teeth. From their line came the more-advanced theriodonts (including the gorgonopsids), who in turn eventually produced our direct mammalian ancestors during the age of dinosaurs.

The dinocephalians and the theriodonts will each be given their own installments in this series.

Dromaeosaurs Of Dracula Country

Scientists in Romania have uncovered and named a new relative of Velociraptor from Transylvania -- Balaur bondoc, which means "stocky dragon."

Link to the paper in PNAS.

The artist's reconstruction is pretty terrifying, if you ask me. I often daydream of chickens and turkeys unlocking some of their dino DNA to take revenge on the humans who torture and exploit them in factory farms.

Creationism Watch: Evolution Wins Big In TX

After a long fight, the crazies concede defeat.

BLOG UPDATE: I've started a new semester this week, so blogging might fall behind for a bit. I will post my article on the dinocephalians this weekend.

I'm also working on a new article series idea, inspired by PETA's Meet Your Meat campaign, but with a more celebratory focus: an evolutionary history of the animal species that humans exploit for food. Most of them are being covered (indirectly) in History Of Your Teeth, but they deserve a spotlight to themselves.

First up will be chickens, ducks, turkeys and all the other feathered friends we slaughter and consume by the billions.