Thursday, October 18, 2018

Deinocheirus - What the Heck is it Anyways?



Can Deinocheirus do kung fu? Or is Mongolia to far away?

Deinocheirus is perhaps the embodiment of dinosaurian diversity itself. It shows a variety of different features, including:

  • Hooked thumb claws (present in Spinosauridae)
  • Duckbill (present in some of Hadrosauridae)
  • A heavily enlarged mandible (present in Shantungosaurus)
  • Elongated arms (present in Therizinosauria)
  • A pygostyle (present in Oviraptorosauria and Aves)
  • A dorsal sail/ridge/hump (present in Spinosauridae, some of Carcharodontosauridae, and Ouranosaurus)
  • Shortened legs (present in Majungasaurinae, Metriacanthosauridae, Spinosaurinae, and Therizinosauridae)
  • Strongly arched dorsal series (present in Hadrosauridae)
So, more or less, it's basically a display case of Theropoda's weirdest and a few odd ornithopod features chucked in there. To truly appreciate how strange it is, it might be nice to show it with some other giant Asian theropods.
Same image as before, but Deinocheirus now has a few friends (and enemies... get outta there, Tarbosaurus)!
Let's go through them one-by-one:

Therizinosaurus: This guy rivals Deinocheirus in mass, but was definitely shorter (in length), although apparently taller. With its stubby tail and pot belly, Therizinosaurus was one of the most devoted non-avian herbivorous theropods. Therizinosaurus has immense arms that were about 3.5 meters long (a good meter longer than in Deinocheirus), and they were tipped with sword-like claws. The peculiar thing about these two browsers was that they were contemporaries, both sharing the Nemegt Formation. Perhaps the lack of Asian titanosaurs had something to do with theropods moving in?

Tarbosaurus: If Tyrannosaurus was king, then Tarbosaurus was emperor. The biggest specimens could exceed lengths of 10 meters, and it would have been a formidable beast. This giant theropod was also a resident of the Nemegt Formation, and probably was the main enemy of Deinocheirus (and Therizinosaurus, too). Tarbosaurus is interesting since it has a proportionately bigger head than Tyrannosaurus. It also had a close relative called Zhuchengtyrannus that lived in China. Deinocheirus seems to have been longer and heavier (although I might do a follow-up post on the validity of this statement).

Yangchuanosaurus: For whatever reason, Yangchuanosaurus is often overlooked in arguing over who was the biggest theropod. But this odd theropod was quite large, reaching lengths of 10-11 meters. It was from way back in the Jurassic, and one of the largest theropods of that time, too. It had somewhat shorter legs than other allosaurs, and a rounder head.

Gigantoraptor: This is yet another theropod that grew to giant sizes and assumed an herbivorous lifestyle. At 8 meters long, it was not very big compared to Deinocheirus, but considering that the next largest oviraptorosaur (Anzu) was not even half as long as Gigantoraptor, it was by no means small (unless we start talking about sauropods). The eggs of this giant were each half a meter long and were laid in nests 3 meters across! Unlike Deinocheirus and Therizinosaurus, Gigantoraptor retained long legs.

Ichthyovenator: This enigmatic beast from Laos is a spinosaurid. This critter had a peculiar bifuricated ridge/sail/hump on its back. Like other spinosaurs, Ichthyovenator would have spent its days around or in large bodies of water, hunting a variety of prey items, especially fish. While Deinocheirus was primarily herbivorous, it also ate fish (based on gut contents).

Gallimimus: This slender, cursorial omnivore was a giant among its fellow ornithomimids, at 6 meters long. Gallimimus had very long legs for a theropod, although they actually were on the short side for ornithomimids. It probably was not as fast as Ornithomimus or Struthiomimus, but it still was a dinosaurian speed demon. Ornithomimids are unusual, since they entirely lost their hallux (commonly referred to as a dewclaw). This is one of the many features that allies it with Deinocheirus, and, perhaps surprisingly, is the closest relative of Deinocheirus out of all the theropods in the second image.

Monolophosaurus: The earliest and most basal theropod in our little collection is Monolophosaurus. This five and a half meter long carnivore had an unusual crest on its head, composed of the ridges on its snout. This crest would have been used for display. Monolophosaurus is from the Middle Jurassic, and is one of many odd crested theropods, with the Asian Sinosaurus and the Antarctic Cryolophosaurus also having bony head crests.

Achillobator: This 5 meter animal was a dromaeosaurid, the family of dinosaurs that includes several of our favorite feathered non-avian friends, including Velocriaptor, Deinonychus, and Utahraptor. While not as big as Utahraptor, Achillobator was still huge for a dromaeosaur (although the South American Austroraptor surpassed them both in length). Achillobator seems to be a fairly typical dromaeosaurid, albeit a very large one.

File:Deinocheirus Scale.svg
MPCD-100/127's willing to talk but /18 and /128 are still trying to figure out what that puny biped is. These size comparisons sure can look a little odd sometimes!
So there you have it. There were several large theropods that roamed Asia in the Mesozoic Era, but Deinocheirus actually seems to be the biggest of the bunch. So what does this mean?
  1. Give Deinocheirus the honor of appearing in your mega-theropod size chart (which we're all doomed to make someday) ;)
  2. Even among the giants, theropods still displayed incredible diversity. Wings, tail fans, and herbivory clash with the stereotypical view of claws, teeth, and insatiable carnivory. But that isn't a bad thing. It shows that even among the tyrants and the carchars, it's hard to ignore how mindbogglingly successful dinosaurs were as a whole.
It's a real shame that these wonderful giants are eclipsed by the giant theropods from elsewhere. Rarely do we get to appreciate the levels of diversity achieved by Asian theropods.

References:
  • Paul, Gregory S. The Princeton Field Guide to Dinosaurs. 2nd ed. Princeton, NJ: Princeton UP, 2016. Print. ISBN 9780691167664
  • Since WP:OR doesn't apply to the world of blogging, I've taken the liberty to really closely compare these creatures and draw some parallels.
Skeletals:
Without these guys, I'd be helpless and this post would never exist. Special thanks to the work of all those skeletal drawers out there!
(NOTE:The Ichthyovenator was taken from my old image here. If you're looking for a skeletal of this guy then this one by PaleoGeekSquared is rather good.)

Monday, August 6, 2018

Tylosaurus Strikes Back

Caution: MAY BITE! Image by me, Slate Weasel, published under a CC BY 4.0 license. The main reference for this image was Scott Hartman's skeletal.
Ugh... dinosaurs, pterosaurs, plesiosaurs, ichthyosaurs, pelycosaurs, nothosaurs, protorosaurs, archosaurs... considering that "saur" means "lizard," these names are all rather deceptive and frustrating, especially when people dismiss dinosaurs as "giant lizards." But mosasaurs actually are lizards!

FINALLY!

And it is a mosasaur that currently decorates the banner of Delta, and what better choice is there than Tylosaurus? Tylosaurus is not the largest mosasaur, but is still one heck of a bruiser, and not something that I'd envy meeting while swimming. Sadly enough, marine reptiles aren't featured very prominently in reference books, making digging up information about them rather difficult. However, I've thrown together a small amount of information about this monstrous lizard.

The species that you see above and below is T. pembinensis, currently one of the few mosasaurs that I've found a good skeletal for (maybe I'll find some more someday...). Since T. pembinensis is not as formidable (I mean big) as its relative T. proriger, it appears to be a less popular animal to restore.


That said, it's not like T. pembinensis was small, either. This one is really mad about something related to "his" diver. Image by me, Slate Weasel, published here under CC BY 4.0.
Mosasaurs are often misinterpreted as serpentine swimmers, but that was not the case. A recent study analyzed a specimen of Platecarpus that preserved various soft tissue impressions. The tail had a downward bend, and skin impressions from the upper fluke were preserved. The shape suggests an asymmetrical caudal fin, good for more advanced types of swimming. This tail shape is rather common among marine reptiles, seen also in ichthyosaurs and metriorhynchids (marine crocodiles).

But, since we haven't yet escaped weird taxonomic problems, we're just going to go over the taxonomy of Tylosaurus. T. pembinensis, the species in the two images above, was originally named as a species of Hainosaurus before becoming a species of Tylosaurus. However, Hainosaurus may be Tylosaurus or it may be distinct. It isn't very clear. Even T. proriger failed to escape the chaos. It was given the name Rhinosaurus by Marsh, renamed Rhamphosaurus by Cope (both of which were preoccupied), until it finally received the name of Tylosaurus.

So these are the mosasaurs. Awesome giant marine lizards that get misunderstood and underestimated. Not much progress has been made, even the "frill-backed" version still exists in modern media. Then again, popular media has a knack for getting things wrong. Until the next time, here's one more mosasaur:
Platecarpus, the modern way. By me, Slate Weasel, originally published here under CC BY 4.0.
This is Platecarpus, the one featured by the study I mentioned above. It doesn't look all that lizard-like anymore, to be honest. However, it does look much more streamlined and fast, which is a good thing if you're a marine predator. Oh, and here's one more:
Goronyosaurus, a tough-looking mosasaur. By me, Slate Weasel, oringinally published here under CC BY 4.0.
Okay, I'm really done now.

References

Friday, August 3, 2018

Suchomimus - Random Spinosaurid Theropod

Suchomimus tenerensis, an African spinosaur, goes for a swim. It's been popular to restore Spinosaurus this way but I don't understand why it's not been shown very often with other spinosaurids. This image is by me, and in the Public Domain.

Spinosaurids are very unusual theropods that evolved to feed on aquatic prey, primarily fish. They were an odd bunch, with a variety of specialized features for their unusual lifestyle. These include long, crocodile-like snouts (in fact, Suchomimus means "crocodile mimic"), enlarged and hooked thumb claws, shorter legs, long torsos and conical teeth.

This enigmatic group sure got around, too. In South America, there's the bizarrely-named Irritator (its fossils had plaster added to them to make them look like those of a pterosaur!) from the Santana Formation of Brazil. Additionally, the giant Oxalaia, which is one of the largest theropod dinosaurs, is also known from another Brazilian locality. There also is an indeterminate spinosaurid from Argentina.

In Europe, there was Baryonyx. One of the first spinosaurs that was discovered, many older books (and some poorly-researched newer ones, too) claim that it was the ONLY dinosaur that ate fish. This, obviously, is no longer considered to be the case. Baryonyx was present in England and Spain. Another English spinosaurid, Suchosaurus, was originally thought to be a crocodile, and may be synonymous to Bayonyx.

Africa (specifically Egypt and Morocco, and possibly Kenya and Tunisia) was home of the enormous Spinosaurus, the largest theropod. Its holotype was destroyed in WWII, but more material has been found. This reveals a very wierd animal with stumpy legs and powerful arms. However, that new material is classified as Sigilmassasaurus by some. Further south was Niger, home of Suchmomimus, which you can see above. It was similar to Baryonyx but it had a short sail, unlike its relative which had no sail. Another spinosaurid from the same locality, Cristatusaurus, is known from only a small number of bones and may be synonymous to Suchomimus. Suchomimus may, in turn, be synonymous to Baryonyx.

Asia had no shortage of spinosaurids, either. The most complete is Ichthyovenator, a split-sailed spinosaurid from Laos. The nearby Thailand was home to Siamosaurus, which originally was thought to be a fish! More material and study has confirmed its status as a spinosaurid. Additionally more than one unnamed spinosaurids are known from China, and there's even evidence of a Japanese spinosaurid!

There even is an unnamed spinosaurid from Australia that seems to be related to Baryonyx. Unlike many others, it is known from a cervical vertebra, not teeth. No spinosaurids are known from Antarctica, but I suspect that they will eventually be found there.

And North America? Well, so far all of the above spinosaurids were from the Cretaceous period. A Jurassic record is known but rather tentative and dubious. However, a possible spinosaurid is known from the Morrison Formation. Additionally, I'm not going to deny you another post about the Tendaguru, as another possible spinosaurid (Ostafrikasaurus) is known from there.

So that's a definite distribution across five continents, and potentially six. Spinosaurids definitely got around. I may eventually do a post on their unusual anatomy. Until then, more random dinos will come!

References

  • Paul, Gregory S. The Princeton Field Guide to Dinosaurs. 2nd ed. Princeton, NJ: Princeton UP, 2016. Print.
  • Holtz, Tom. "Genus List for Holtz (2007) Dinosaurs". See here.
  • Benson RBJ, Rich TH, Vickers-Rich P, Hall M (2012) "Theropod Fauna from Southern Australia Indicates High Polar Diversity and Climate-Driven Dinosaur Provinciality." PLoS ONE 7(5): e37122. https://doi.org/10.1371/journal.pone.0037122
  • The Paleobiology Database Navigator, using the filter of Spinosauridae.

Tuesday, July 31, 2018

Giraffatitan - Random Tanzanian Sauropod

Life restoration of Giraffatitan brancai. By me (Slate Weasel), CC BY 4.0. Scott Hartman's skeletal was an invaluable reference while drawing this. Scale bar = 1 meter.
If you're not too familiar with dinosaurs, you may not recognize the name of Giraffatitan... but the shape is recognizable... perhaps enough to make you ask, "is that Brachiosaurus?" The answer is complicated. Read on if you want to know why. If you don't want to know why, or if you just don't want to read, the short answer is no.

Last post, I discussed Kaijiangosaurus and how we may be a bit overzealous when naming dinosaurs. However, sometimes we're actually too cautious when naming dinosaur genera. Brachiosaurus is a prime example of this, and why not discuss taxonomy that has been resolved to a point where it is reasonably stable today? You'll probably feel a lot less confused by it while still getting a feeling of how taxonomy is not set in stone (even if the evidence is!).

So, Elmer S. Riggs described some fossils that were found in Colorado as Brachiosaurus altithorax in 1903. These elements were few in number, and mostly centered around the rump. They were composed of two caudals, the sacrum, seven dorsals, some dorsal ribs (I'm not sure how many), right illium, partial left illium, right femur, left coracoid, and right humerus. This rather small collection is surprising for an animal as famous as Brachiosaurus.

Various other material has also been taken out of the Morrison, including various parts of sauropod postcrania that have been tentatively referred to Brachiosaurus. Whether or not they truly belong to Brachiosaurus is uncertain due to the sheer lack of associated material. There even is a partial skull that was found by Othniel Charles Marsh that he attributed to Brontosaurus, but is now generally considered to probably belong to Brachiosaurus.

However, much better specimens were unearthed in the Tanzanian Tendaguru Formation by German expeditions that started in 1909 and ended in 1912. Jaensch named two species based on this material, Brachiosaurus brancai and B. fraasi, although the latter was synonymized with the former by Jaensch in 1929. With all of the material added up, virtually the entire skeleton is represented. This is very impressive for a sauropod, as a large number of them lost their heads (and frequently other distal bits) during fossilization.

Since B. brancai was considerably more complete than B. altithorax, it was obviously the main model used for illustrations and models of Brachiosaurus. However, its placement in Brachiosaurus was dubious, and it was finally formally seperated by Gregory S. Paul in 1988, and a 2009 paper by Mike Taylor reinforced this.

Because of this taxonomic separation, many skeletal mounts are labeled as Brachiosaurus when they're really Giraffatitan, and many books list Tanzania as a locality of Brachiosaurus. But it's not necessarily over yet. In his 2016 field guide, Greg Paul claimed that G. brancai might be further dividable into more species.

It should also be noted that there's another brachiosaurid from the Tendaguru Formation. It currently has no formal name, but it seems like it's huge, bigger than either of the two brachiosaurids discussed here. Additionally, a third brachiosaurid of Brachiosaurus-type size called Lusotitan is known from Portugal.

Well, that's all for now. I'll probably return to the topic of brachiosaurids and the Tendaguru, they seem like they're good for discussion. And that giant brachiosaurid that I mentioned above? Work's being done on it...

References
If you like reading about sauropods, you should check out SV-POW.

Sunday, July 29, 2018

Kaijiangosaurus - Random Chinese Theropod

One of my first digital restorations was of this animal... strange choice.

Since there's nothing like writing about random dinosaurs, I'll use this post to describe Kaijiangosaurus. Why choose Kaijiangosaurus? Who the heck knows? It's known from a small amount of material and has uncertain classification. So let's go down this strange pathway...

The first time that I ever encountered the name of Kaijiangosaurus was in Dougal Dixon's The Illustrated Encyclopedia of Dinosaurs. Without that book on hand, I'll reference the 2011 book known as The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. It gets mentioned as an "obscure theropod" that hunted sauropods and was from the Dashanpu Formation.

Now we have something that we can discuss in detail! The Dashanpu Formation is a geological formation in China. Using Paul's 2016 book, it seems that this formation includes the Shaximiao and Shangshaximiao. These beds are famous for yielding several sauropods and stegosaurs, such as Shunosaurus, Mamenchisaurus, Omeisaurus, and Tuojiangosaurus. There are also large theropods there, including Yangchuanosaurus... which does raise some interesting thoughts.

According to Dixon's book, Kaijiangosaurus is known form seven cervical vertebrae, (which is more than most dinosaurs are known from!) which "are definitely" those of a carnosaur. However, Holtz's 2011 Appendix (which is incredibly useful) only states that it could be a carnosaur. Interesting. Both, however, estimate its length at 6 meters. But there are many other carnosaurs from the Dashanpu, including Yangchuanosaurus, Szechuanosaurus, Xuanhanosaurus, and Gasosaurus (at least).

That's quite a large number of theropods, most of which don't seem to be known from outstanding remains. It's quite possible that Szechuanosaurus is a junior synonym of Yangchuanosaurus (although the species would still be valid), and this is what Paul lists in his 2016 book. Additionally, Dixon states that it's sometimes thought that Kaijiangosaurus may be the same animal as Gasosaurus, although I'm not sure where the source for that claim comes from.

I'm not stating that the synonymy is absolutely true or absolutely false, but it may be wise to not be too overzealous when naming dinosaurs. Many genera have been named only to have their species sunk into a different genus. It's too bad that we don't have a very clear look at theropod diversity in the Dashanpu. More material could mean more clarifications. Time will tell...

Sources
  • Paul, Gregory S. The Princeton Field Guide to Dinosaurs. 2nd ed. Princeton, NJ: Princeton UP, 2016. Print.
  • Dixon, Dougal. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House, 2011. Print.
  • Holtz, Tom. "Genus List for Holtz (2007) Dinosaurs". See here.
I'm planning on doing more random dino posts, so stay tuned if you like this...

Updates may be added if I find things of moderate significance.


Monday, July 10, 2017

Theropod Lengths

The image you see above is a size comparison of Ornithomimus, or ostrich dinosaur. Just in case you didn't notice, there are a lot of confusing bars. So what's up with that?

Dinosaur Size
The first step in creating an image like this is to figure out big the dinosaurs are. Using The Princeton Field Guide to Dinosaurs, I got the lengths 3.8 and 4.8 meters. The next step is to draw out the dinosaur's outline, which is easy, right? Heck no...

Outlines
Shrink wrapping is not good!
Outlines are a very controversial part of dinosaur paleontology, and very hard to make. First of all, you must figure out what the dinosaurs muscles looked like, then you need to think about the dinosaur's integument (scales, quills, fuzz, feathers, etc.). The dinosaur must not be too skinny, like the ones in the image you see on the right. It also must not be to bulbous. Also, it needs to be in a realistic postition for it to actually look trustworthy. After that, there are even more things to consider...

The Vertebral Column
The original (wrong) drawing, with the dinosaurs being too big.
Even length is hard. When I said O. edmonticus was 3.8 meters long, that most likely means means its vertebral column was 3.8 meters long. Since this guy held its neck upright, that reduces its overall length. Also, if the dinosaur has a feathered tail, that can give the illusion that it is even longer than it really is. This is very problematic, as you need to create a copy of the dinosaur's vertebral column and stretch it out. After you finish that, you scale the length of the line to the length of the dinosaur, shrinking the dinosaur with the line. This is a complicated process, and I recommend using an SVG image editor to do it.

Lots of Complicated Markings...
Next, we will move on to complicated lines crisscrossing the image. The image you see on the right has two lines for each dinosaur, the thick, floating one indicates the vertebral column's length, while the thin one on the dinosaur indicates where the vertebral column is. The second line isn't really necessary, so I removed it in the final version of the image. The final draft is at the top of the page. Enjoy!

Sources
Most of this was based off a discussion on Wikipedia about this image. Some of the information comes from a book called All Yesterdays, by Darren Naish, John Conway, C. M. Kosemen, and Scott Hartman, published by Irregular Books.

-This file is available in SVG format on Wikimedia Commons.
-This post is in the public domain, including all the images.