Wednesday, November 30, 2016

Tyrannosaur Chronicles

I'm finishing up (probably today; I've only got about 35 pages to go) David Hone's The Tyrannosaur Chronicles, a very recently published (this year) popular science book about the tyrannosaur family.  It's quite good, and I certainly recommend it, but there are a few comments I have about it.  First; I find it curious that he presents the Loewen phylogeny as if it's an unusual alternate compared to the "standard" phylogeny, but on Wikipedia, the Loewen phylogeny of Tyrannosauroidea is the only one presented.  There's a lot of interesting "what-ifs" in the details of the phylogeny of the Tyrannosaurini clade in particular floating around.  A very recent phylogeny that I like is included here as an image; one thing that it also does is show in graphical form more or less where and when the various species lived, which is really important.  One recent theory (too recent to have appeared in the book, unless it's in the last few pages, which I doubt) is the notion that tyrannosaurines in particular underwent two distinct radiations; a North American (Laramidan) one, and an Asian one.  The North American radiation gave us classics like Daspletosaurus and as well as more recent finds like Teratophoneus, Lythronax and the odd Nanuqsaurus.  T. rex himself, while appearing in North America, of course, would be an interloper in this scenario; a member of the Asian clade that includes Tarbosaurus and Zhuchengtyrannus and who came to North America across the land bridge and basically out-competed the local tyrannosaurines and replacing them through the Maastrichtian.

One odd find in the cladogram attached, which is at odds with most that I've seen, is that it shows Bistahieversor as a sister-group to Tyrannosauridae rather than nestled comfortably within the tyrannosaurines.  Either way, however, it points to something different going on in the north vs the south of Laramida.  It may not require an Asian Invasion of T. rex itself (the invasion might have gone the other way, for instance—Zhuchengtyrannus and Tarbosaurus might be North American invaders of the same type as T. rex—perhaps descended from Daspletosaurus.

In any case, I encourage you to have a look at the various phylogenetic proposals and come to your own conclusions.  Even if you don't like the way the tyrannosaurines are positioned in the one I've attached here, you've got to admit that the graphical presentation of the geography and timeline are extremely useful.

Another thing that I was unaware of, because I hadn't really been paying close attention is the raising of the subfamily alioramines which would have played a similar ecological role, I suppose, in Asia as the albertosaurines did in North America; smaller, more slender predators which presumably had either a different hunting strategy or different prey targets than the tyrannosaurines.  Similar to leopards in the same region as lions or tigers, if you will, or coyotes or golden jackals in the same region as wolves.

However, the most disappointing thing that The Tyrannosaur Chronicles didn't include was a good catalog of the various members.  This was always one of my favorite parts of Greg Paul's old Predatory Dinosaurs of the World, and a brief catalog with time-frame, size, location and some description of both the animal itself and the environment in which it lived would be welcome.  I guess I'll have to do it myself; it shouldn't be too hard to start with Infogalactic, look at the primary sources from there to add, if necessary, and put my own little catalog together.

So... I guess that means I've got at least a few more PALEONTOLOGY tagged post coming up in the very near future...  Maybe while I'm at it, I'll even add the Megaraptorans just in case they end up belonging to the same family tree as well (as opposed to Neovenatoridae, as they are traditionally albeit hesitantly placed today.)

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