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Tag Archives: Late Cretaceous
I know that it’s been a while, but here is my latest addition of paleo-art to this blog. Behold – Alamosaurus, a behemoth of a sauropod that roamed Texas during the late Cretaceous Period. Alamosaurus was a member of the “titanosaur” family, which is more well-known from species found in South America, Europe, and Africa. No complete skeleton of Alamosaurus has ever been found, so we only have a rough idea about what it looked like, and we’re not even sure how big it was when it was fully grown. The most common estimate that I’ve seen is that it was somewhere around 65 – 70 feet long, but it might have been bigger than that.
Because no complete specimen of Alamosaurus has been found, you’re going to see a lot of variation in paleo-art reconstructions of this animal. From what I’ve gathered, a lot of the pictures that are visible on the internet these days are inaccurate. Alamosaurus had a massively thick neck, but its tail was not correspondingly long or massive. The presence of osteoderms along its back are a guess, since other titanosaurs, notably Saltasaurus, were known to have had them.
In January, I published a post in which I hypothesized that Dryptosaurus, a Late Cretaceous theropod found in Eastern North America, was misidentified. For the longest time, Dryptosaurus was believed to be a tyrannosaur, possibly a rather primitive one. However, with discoveries made within the past two decades, I came to question this taken-for-granted identification.
The megaraptorids are a weird bunch, since nobody knows for certain where exactly they fit. When the type species Megaraptor was found in Argentina by the paleontologist Fernando Novas, it was believed to be a giant dromaeosaur – hence the “raptor” name – measuring at least 25 feet long, which would have made it the largest raptor ever discovered up to that point.
Then in 2010, a study conducted by Benson, Carrano, and Brusatte claimed that the megaraptorids were more related to the allosaurs than the dromaeosaurs. Specifically, the study stated that the megaraptorids were very closely related to Neovenator. It certainly helped when a complete arm was discovered, which showed that the 15-inch long killing claw didn’t come from the foot, but actually came from the hand, similar to Baryonyx.
In 2012, Fernando Novas conducted his own study of Megaraptor and its relatives. He and his colleagues said that while Neovenator and the carcharodontosaurids were close relatives of each other, and that both belonged within the superfamily Allosauroidea, he also stated that Megaraptor and its ilk did not belong in this group. Instead, he stated that the megaraptorids were actually coelurosaurs, and were more closely related to the tyrannosaurs.
In 2014, more evidence to back up a connection between the megaraptorids and the tyrannosaurs came to light when a juvenile Megaraptor was described by J. D. Porfiri, Fernando Novas, and others. Porfiri even placed Eotyrannus, long thought to be a primitive tyrannosaur, as a member of Megaraptora. Because of this, the megaraptorids are thought of by some to be either close relatives of the tyrannosaurs or possibly even an offshoot of the tyrannosaur family.
As a result of learning all of this, I began to wonder if Dryptosaurus was actually a member of Megaraptora, and I published a post saying as much. However, Chase Brownstein, a paleontologist specializing in eastern North American dinosaurs who works at the Stamford Museum, and who I have been in contact with on a fairly regular basis, immediately challenged my hypothesis. He stated that while Dryptosaurus might have had some features that made it visibly look like a megaraptorid, the animal itself was not a member of the megaraptorid family. He put these physical similarities down to convergent evolution – when two different kinds of animals evolve in such a way that they look similar to each other. Convergent evolution is most often brought about by environmental conditions, which infers that both Dryptosaurus and the megaraptorids lived in similar environments, had similar lifestyles, or both.
I recently discovered that my hypothesis was not unique. An internet search showed that at least by 2014, other people had been looking at Drytposaurus with questioning eyes and were wondering if it was actually a megaraptorid. Damn, this happens all the time. Every time that I think I’ve come up with a new idea, it turns out that some has already thought of it before. Oh well.
While my assessment of Dryptosaurus as a megaraptorid may or may not be correct – we’ll never know the real answer until more Dryptosaurus specimens are found and analyzed – I feel that my drawing of Dryptosaurus is nevertheless accurate. A phylogenic analysis conducted in 2013 placed Dryptosaurus between Raptorex (which, according to some, is actually a misidentified juvenile Tarbosaurus) and Alectrosaurus. Both Raptorex and Alectrosaurus had similarly-shaped skulls, so I gave my rendition of Dryptosaurus a skull that was very similar to these two species. I gave it the massive thumb claws that are seen on the holotype specimen. I also gave my creation a mane of fibrous feathers, since many primitive three-fingered tyrannosaurs are known to have had feathers covering some or most of their bodies.
Figure 1. Skull of Alectrosaurus. Illustration by Tracy Ford (I think). http://www.paleofile.com/Dinosaurs/Theropods/Alectrosaurus.asp.
Figure 2. Skeleton of Raptorex. Photo by Kumiko (September 24, 2011). https://commons.wikimedia.org/wiki/File:Raptorex_vs_Psittacosaurus.jpg.
Figure 3. My own drawing of Dryptosaurus.
Behold my masterpiece.
This is the fifth T. rex drawing that I’ve posted to this blog, and it is the hardest drawing that I have ever had to make. Every individual scale was done by hand, one by one. This drawing took me months to finish. To give you a better idea about the utterly insane amount of detail, the actual drawing of the dinosaur itself from the tip of its nose to the tip of its tail measures precisely 24 inches. Most of the drawn scales measure at only one millimeter in diameter.
As you can see, it is done in the same pose as my previous two full-body T. rex drawings, but I made some noteable improvements:
- Slightly changing the shape of the skull – my original one looked a little too much like Tarbosaurus rather than Tyrannosaurus.
- Not making the face as shrink-wrapped as the original head drawing was.
- Making the neck more detailed and fuller.
- Changing the position of the hands to be more anatomically correct.
- Making its body fatter – the original was too skinny.
- Making the tail thicker and fatter to properly counter-balance the now-heavier front half of the body.
- Changing the shape of the feet.
This drawing was made on several sheets of 8.5 x 11 printer paper, with just an ordinary No. 2 pencil…and a whole lot of patience.
A while back, I asked you, the reader, if you had any requests for articles and artwork that you would like me to do, but I received no reply. However, I recently looked at the search terms that come up on this blog’s administration page. Most of the terms concern subjects that I’ve already written about or illustrated, but there were a few others on subjects that I haven’t touched yet, or have only just alluded to. Terms which showed up frequently were (in order of frequency):
- Alamosaurus (12)
- Caenagnathus / Chirostenotes (9)
- Pterosaurs (8)
- Liopleurodon (7)
- Mosasaurs (6)
- Dakotaraptor (5)
- Velociraptor (in color) (5)
- Suchomimus (4)
- Carnotaurus (3)
- Oviraptor (3)
Others caught my interest as potential future art or writing projects, including:
- Allosaurus courting
- Allosaurus head
- Allosaurus walking
- Dinosaurs of Texas
- Dracorex head
- Iguanodon head
- Pachycephalosaurus keeping shelter
- Triceratops eating
- Tyrannosaurus juvenile
- Lacrimal horns on dinosaurs
- Mesozoic turtles
- What dinosaurs lived on Long Island?
The last three sound like interesting research projects. Anyway, based upon what I have seen, I think that I can gauge what you would like me to do. So, I’m treating these statistics pretty much like a to-do schedule. Right now, I’m really hammering on a super-detailed drawing of a full-body T. rex, which I hope to have finished within one or two weeks, and then put up here for you to admire and comment on. After that, I’ll focus on the items on these two lists – the “frequency list” will take priority. I’m happy to say that some of these terms are on things that I’ve had in the back of my mind for a while, so this will give me the impetus to do them. Take care everybody, and keep your pencils sharp.
A new feathered terror has been added onto an ever-growing list. Boreonykus, “the northern claw”, is a new species of dromaeosaurid theropod discovered in Canada in rocks dated to 72 MYA. It was one of the larger of the Late Cretaceous rapors, with an estimated length of 13 feet. Its contemporaries would have been such well-known creatures as Albertosaurus, Daspletosaurus, Dromaeosaurus, Ornithomimus, Chasmosaurus, Styracosaurus, Centrosaurus, and Parasasaurolophus.
For more info, look here:
Philip R. Bell and Philip J. Currie (2016). “A high-latitude dromaeosaurid, Boreonykus certekorum, gen. et sp. nov. (Theropoda), from the upper Campanian Wapiti Formation, west-central Alberta”. Journal of Vertebrate Paleontology, vol. 36, no. 1; doi: 10.1080/02724634.2015.1034359
Chasmosaurus was a common genus of ceratopsian dinosaur found in North America, especially Alberta, Canada circa 75 MYA. This creature is so recognizable due to its rectangle-shaped frill that it has given its name to a whole slew of other ceratopsians that are related to it – the “chasmosaurine” ceratopsians.
Made with regular no. 2 pencil on plain white printing paper. The actual drawing of the creature from the tip of the beak to the tip of the tail measures just a smidge over seven inches. Scanned at 600DPI to show as much of the detail as possible.
Keep your pencils sharp, everybody.
Two weeks ago (though I’ve just heard about it today), paleontologists published a report that they had discovered a new species of dinosaur which inhabited eastern North America during the late Cretaceous Period. Dinosaur fossils from this region are extremely rare, and so any discovery is bound to generate excitement. I’m certain that paleontologist and fello paleo-blogger Chase Brownstein, who is a specialist in eastern North America during the Mesozoic Era, will be geeking out about this discovery very shortly, if he hasn’t been already.
The creature was named Eotrachodon orientalis, “the dawn Trachodon of the East”. It lived in Alabama 83 million years ago, and measured about 25 feet long. Hadrosaurs had only appeared a few million years earlier, so Eotrachodon would have been one of the earliest hadrosaurs not only in North America but globally. Phylogenics suggest that it was a sister taxon of the family Saurolophidae, meaning that it was only slightly more evolved than the most basic hadrosaurs. It is also noteworthy for being found with a mostly intact skull, which gives us a good look as to how an early hadrosaur would have appeared. Contrary to the name “duck bill”, Eotrachodon did not have a broad flat duck-like skull. Instead, its skull was deep with a rounded nose. The fossilized remains, consisting of a partial skeleton and most of the skull, were discovered in 2014 in a creek not far from the city of Montgomery, Alabama.
That fact in itself explains much of why so few dinosaur bones have been found east of the Mississippi River – so much land is covered with cities, farms, highways, and other forms of human development. This significantly limits where a person can dig, and often, the places where you CAN dig don’t contain dinosaur fossils.
For more info, see here:
Albert Prieto-Marquez, et al (2016). “A primitive hadrosaurid from southeastern North America and the origin and early evolution of ‘duck-billed’ dinosaurs”. Journal of Vertebrate Paleontology, published online January 13, 2016; doi: 10.1080/02724634.2015.1054495. http://www.tandfonline.com/doi/abs/10.1080/02724634.2015.1054495?journalCode=ujvp20.