My Prehistoric Saga: May 2018

Edit (11/9119): I remember when this topic REALLY irritated me. Today, it seems so trivial and kind of funny. I'm editing some information in this post, but what I really want to say is that I brought a copy of the book The Complete T. rex, and it does indeed say that Horner doesn't think that T. rex was only a scavenger. He even says he thinks that T. rex is a "part-time hunter" (pg. 218). I still don't understand why Horner kept going on and on about T. rex ONLY being a scavenger for decades, but at least I have seen it in his own words that he doesn't see T. rex as being only a scavenger.

T. rex vs. Triceratops:

Question: Was T. rex a hunter or a scavenger?
Answer: It did both. I mean, this question and debate shouldn't even exist anymore. Every carnivore has to either hunt or scavenge in order to survive. But hey, let's dive into this question and answer it, just for laughs!

For a long time now, it has been questioned whether or not the king of the dinosaurs, Tyrannosaurus rex, was a hunter OR a scavenger. Interestingly, paleontologist Lawrence M. Lambe (1917) said that the tyrannosaurid Gorgosaurus must have been a slow-moving scavenger (pg. 81).

Jack Horner:

Photo from Hugh Riminton (2016).

In the 1990's, paleontologist Jack Horner said that Tyrannosaurus rex must have been a scavenger. He has stated most of his opinions on T. rex in the documentaries Valley of the T. rex (2001), T. rex: Warrior or Wimp? (2004), Dinosaurs Decoded (2009), PaleoWorld: The Legendary T.rex (1994-1997), and The Ultimate Guide: Tyrannosaurus rex (1996). I've seen all of those documentaries. I've also read his co-authored book he wrote with fellow paleontologist Don Lessem called, The Complete T.rex (1993), and his paper that he wrote in 1994 called, Steak Knives, Beady Eyes, and Tiny Little Arms (A Portrait of T.rex as a Scavenger). In every one of those mediums, he's stated that dinosaurs like the dromaeosaurs, the raptor dinosaurs, were the real hunters. They had athletic legs for running, long arms for slicing and grabbing prey, and large eyes. Alternatively, he's said that T. rex had short legs and small arms that prevented it from chasing after, and grabbing, prey, and small eyes. (Horner, 1994, pg. 159-161). According to him, these were not the characteristics of a hunter, but for a scavenger.

Jack Horner is a paleontological consultant for the Jurassic Park/World films, and was the inspiration for the character Alan Grant (Bizarre Dinosaurs, 2009) (Hugh Riminton, 2016). It looks like he's the reason why the dromaeosaurs, especially Velociraptor are so famous today. However, the "Velociraptors" in the Jurassic Park films are really Deinonychus. This originated in paleontologist Gregory S. Paul's book, Predatory Dinosaurs of the World (1988) (pg. 366 and 369). For Jurassic Park III (2001), Horner told the filmmakers to replace T. rex with Spinosaurus (Bizarre Dinosaurs, 2009). In behind the scenes footage of Jurassic Park III, Horner also made sure that the filmmakers portrayed the T. rex as a scavenger, which is why there's a scene with the T. rex feeding on a dead dinosaur carcass before it fights the JPIII's interpretation of the Spinosaurus. Horner stated that the Spinosaurus was a true predator and T. rex was just a scavenger, and in the film Spinosaurus kills the T. rex. This has led to a debate that still continues to this day as to which dinosaur would win in a fight. I have engaged in it many times myself, and I have wasted precious time doing so. I will not get into it again. The JPIII interpretation of the Spinosaurus, or the Jurassic Park interpretation of almost every dinosaur in fact, is not scientifically accurate. It hurts me to say that because I am a longtime fan of the franchise.

P.S.: Horner says that T. rex is his least favorite dinosaur. He also says that the hadrosaurs are his favorite dinosaurs (Horner, 1994, pg. 162):

I agree that they are awesome creatures, but did (or does) Horner hate T. rex because it hunted hadrosaurs? If so, then tuff luck, Jack. T. rex had to hunt hadrosaurs in order to live. I'm not sure if that is the case though. However, something funny occurred to me. Thanks to Jurassic Park III, the Spinosaurus was my least favorite dinosaur for about a decade and a half because it killed the T.rex. I don't hate Spinosaurus anymore, but I blame you for making me do so in the first place, Jack Horner.

Anyway, there is evidence that goes against Horner's scavenger hypothesis for T. rex. Other paleontologists, like Dr. Thomas Holtz, Jr. for example, have stated numerous times that T. rex was capable of hunting. Here, I'll list the evidence that proves that T. rex was capable of predation:

1. Speed:
T. rex is said to have been able to run up to 10-29 miles per hour (Phys, 2011) (Sellers et al., 2017) (Science Daily, 2017) (Igor Nesteruk, 2018, pg. 46), with most calculations putting it in the 20-mph range (Phys, 2011) (Igor Nesteruk, 2018, pg. 46). Horner and Lessem (1993) said that fellow paleontologist Jim Farlow calculated T. rex's running speed at 25 miles per hour (pg. 200). Farlow et al., (1995) would then state 22 miles per hour. Paleontologist John Hutchinson would state 10-25 miles per hour in 2011 (Phys, 2011). Igor Nesteruk (2018) stated that T. rex would have ran 21-29 miles per hour. Therefore, T. rex could definitely reach a maximum top speed of up to 20-29 miles per hour. I would say that 25 miles per hour would be the best medium range. That range of speed would definitely allow T. rex to catch animals that were covered in armor (Ankylosaurus and Triceratops) or were the size of buildings (Alamosaurus). Snively et al., (2019) also stated that the tyrannosaurids were more agile than other theropod dinosaurs, so that means that T. rex was faster and more agile than Horner thought. Not 32 miles per hour like in Jurassic Park (1993), but still at a good speed for such a large animal.

2. T. rex Left Evidence on Its Victims, including Itself:
T. rex left behind some evidence on its victims that hint that it did a lot more than scavenging on dead carcasses. In 1998, paleontologist Kenneth Carpenter discussed an Edmontosaurus annectens skeleton, called DMNH 1493, that had a bite wound on one of its caudal vertebrae (pg. 140-142). Carpenter said the only culprit could have been a T. rex. He also stated that the bite resulted from the hadrosaur either fleeing from the predator, or the Edmontosaurus swung its tail at the T.rex and the T.rex caught it. Either way, the hadrosaur managed to escape the T.rex (pg. 142) (also in Carpenter, 2001, pg. 139-143).

Update 10/16/20: Tanke and Rothschild, 2014 say was caused by another Edmontosaurus, not a T. rex. If it was being hunted by a T. rex, then the wound would be even worse. Heck, the animal would probably be dead altogether ("Abstract," "Discussion" pg. 8-13).

In 2013, it was announced that another Edmontosaurus annectens skeleton, discovered in the Hell Creek Formation of South Dakota, had a tooth lodged in its tail. There were also other bite marks on the hadrosaur as well. Paleontologists have concluded that the tooth found in the hadrosaur's tail belonged to a T. rex. Surprisingly, the hadrosaur got away from the predator. Scientists said that the hadrosaur's tail showed signs of healing (Robert A. DePalma et al., 2013, "Abstract") (Kaplan, 2013). DePalma et al., (2013) also state that some Triceratops skeletons show combat wounds obtained from battles with T. rex. They show signs on healing, which means the herbivores got away ("Abstract").

T. rex also seemed to have a liking for its own species. Nicholas R. Longrich et al., (2010) states that several specimens of Tyrannosaurus show signs of predation from other Tyrannosaurus. It's not clear if these individual Tyrannosaurus were alive or dead when they were fed upon, but this means that T. rex wasn't a picky eater.

3. Carnivores Switch Roles:
The hyena is one of the most notorious scavengers of all time. It also has bone-crushing teeth, like T. rex. However, despite its nasty reputation, it also hunts. Henry Nicholls (2014) states that the Spotted Hyena, for example, hunts for food and that lions tend to scavenge from hyenas. Lions, "the kings of the jungle" and often considered the true predators, scavenge from hyenas! This proves that both predators and scavengers have to do whatever they can in order to get a meal, and this includes both hunting and scavenging. In fact, vultures do this too! According to the Hawk Mountain Hawk Mountain Global Raptor Preserve ("Turkey Vulture": "Raptor Bites"), and Andrea Zippay (2008), both turkey and black vultures hunt occasionally. The black vulture even hunts in packs and goes after livestock (Zippay, 2008) (Turner, 2016). The point is that no carnivore can do one or the other because they would starve.

4. The Arms of T. rex:
In Valley of the T. rex (2001), The Complete T.rex (pg. 208-209), and Bizarre Dinosaurs (2009), Horner says that T. rex didn't have the long arms of a predator. He says that T.rex couldn't bring food to its mouth, nor grab and hold on to prey, and thus its arms were useless. Yes, T.rex did have small arms. However, T. rex's arms don't seem to have been useless. They were wrapped in huge muscles and could lift 400-430 pounds each (Horner and Lessem, 1993, pg. 116) (Bjorn Carey, 2009) (Bizarre Dinosaurs, 2009). Together, that's about 900 pounds! It was also recently suggested that T. rex could dig its arms into the backs of its prey. Paleontologist Steven Stanley presented this argument in 2017 at the University of Hawai'i (Marcie Grabowski, 2017) (Jacqueline Ronson, 2017) (Peter Dockrill, 2017). So despite their awkward size, T.rex's arms apparently had some usage and could have helped it in hunting.

5. T. rex's Binocular Vision:
Horner (1994) said that T. rex had small eyes. However, paleontologist Dr. Thomas R. Holtz (2008) says that tyrannosaurid eyes grew as their skulls grew, and that some other theropods' eyes grew slower than the tyrannosaurids (pg. 375). Therefore, tyrannosaurids did not have really small eyes (pg. 376). Farlow and Holtz (2002) say that T. rex had really large eyes, stating, "...the dimensions of the orbit (eye) suggest that Tyrannosaurus had a big eye in absolute terms, which would have increased its light-gathering capacity and thus is acuity (keen or sharp vision)," (pg. 256). Therefore, T. rex had large eyes and great vision.

Holtz (2013) in a lecture explains that T. rex's eyes faced forward. Other theropod dinosaurs (Holtz uses an Acrocanthosaurus for comparison) had eyes that were positioned on the sides of their skulls, and they could only see from the side. T. rex's eyes, since they faced forward, were positioned on the top of its head. T. rex had larger eyes, and better vision, than other theropod dinosaurs. In fact, Professor Kent Stevens says that T. rex had a binocular vision range of 55 degrees, which is greater than a hawk's (Matt Blitz, 2014). T. rex's vision rivals even the birds of prey, which are excellent hunters.

6. The Size of T. rex:
I've done a lot of research on how big T. rex was able to grow. In summary, an adult T. rex was 40-70 feet long. Links to how I was able to calculate these sizes are down below. T. rex was undoubtedly the largest predator in its environment, and it coexisted with some of the largest herbivores that ever lived (Edmontosaurus annectens and Alamosaurus). For a predator to get that big, and to keep the large herbivorous dinosaurs' numbers in check, it would have to both hunt and scavenge.

MOR 1126 ("Celeste Rex"):

Photo from Mark Smith (2000).

Jack Horner in the early 2000's discovered numerous T. rex specimens. One of them, called MOR 1126 or "Celeste Rex," named after Horner's first wife, is stated to have been larger than "Sue" (Mark Smith, 2000) (Melissa Sogard, 2000, p. 5) (Celeste Horner). According to my math, MOR 1126 would have been about 64 feet long (based on a toe bone). If this is accurate, then compared to a 45-foot long "Sue," that's a HUGE carnivore! Now the question is, how do you think "Celeste Rex" got so big? It couldn't just sit around and wait for something to die. It had to go out and find it. It either hunted for food or scavenged. Not one over the other, but both. In order to have gotten that big, "Celeste Rex" had to have been extremely successful at both hunting and scavenging, or it would have died a long time ago and wouldn't have been that big.

The large size of MOR 1126 also shows that T. rex kept the large herbivores of its time in check. Heck, the largest T. rex specimen I've found was actually 70 feet long. This is based on a gigantic humerus. This would help T.rex to take on the huge sauropod, and hadrosaur, Alamosaurus and Edmontosaurus annectens. Therefore, T. rex's large size indicates that it hunted large prey.

7. Horner Never Took It Seriously?
So far, we have seen that T. rex could have ran up to 20-29 miles per hour (mainly 25 mph), fought and attacked contemporary herbivorous dinosaurs and other T. rexes, and that it had surprisingly strong arms that could help it in attacking its prey. However, it seems that Jack Horner has stepped back a bit on his scavenger hypothesis for T. rex. In 2013, Horner commented on the find concerning the T.rex tooth stuck in the Edmontosaurus annectens tail. He said that he has always stated that T.rex was a hyena, which scavenges but also hunts (Kaplan, 2013). That sounds surprising, but it gets even better.

In The Complete T.rex (pg. 218), Horner says that he never believed that T. rex was just a scavenger. He just wanted to say that it so he can "be contrary" to his colleagues. he does believe T. rex to be a "part-time hunter." I first saw this quoted in Laelaps (2013), and then in the book itself when I brought it a couple of days ago.

Jack Horner's Quote from The Complete T. rex (pg. 218):

Quote Again by Brian Switek (Laelaps) (2013):

...Um, WHAT!?

If that's true, then why would he constantly bring up his scavenger hypothesis every chance he got!? On multiple documentaries, he's stated that T. rex was only a scavenger! He's said that the dromaeosaurids and Spinosaurus were the real hunters, not T. rex! And yet, after decades of promoting his scavenger hypothesis, it turns out that Jack Horner never meant it. He also says in his book that he sees T. rex as a "part-time hunter" (pg. 218).

...Okay, I'm done. This debate is officially over, and a complete waste of everyone's time. T. rex is a hunter and a scavenger. This also goes for Gorgosaurus, and every other carnivorous theropod dinosaur.

P.S.: I don't hate Jack Horner anymore. I'm too preoccupied with other stuff nowadays anyway.

Update (10/18/20): In 2017, at the Jurassic World Frontier Expo ("'The Origins of Jurassic Park and Jurassic World' with Jack Horner" on YouTube), Horner actually says the truth about the Spinosaurus vs. T. rex fight in Jurassic Park III:

Update (11/26/20): The remains of a juvenile T. rex and a Triceratops, called the "Dueling Dinosaurs," have been found together. Both specimens show pathologies that have been sustained in combat, which seems to have led to the two dinosaurs dying side-by-side. The Triceratops had the T. rex's teeth in its spine and pelvis, and the T. rex's skull was split (Pantuso, 2019, p. 16-17) (Strickland, 2020, p. 10)

(Bonhams, "Dueling Dinosaurs," p. 7). This seems to indicate that the Triceratops was being hunted by the T. rex. Now this is a juvenile specimen, but this still doesn't change the fact that T. rex hunted for food as well as scavenged just like any other carnivorous animal, alive or extinct. Once again, this is evidence against the "Scavenger Hypothesis," but at this point this hypothesis is dead in the water anyway. I just wanted to talk about this awesome discovery.

"Dueling Dinosaurs" (Bonhams):

Update (127/21): Holtz (2008) basically repeated everything I said in this post ("Conclusions" pg. 390). He does question whether or not tyrannosaurids used their hands for predation ("Short Arms" pg. 382), but says that birds, hyenaenids, and canids have no problem hunting without hands ("Short Arms" pg. 383). I disagree with T. rex's arms being useless in grasping prey, but the canids and hyenaenids examples are spot on. T. rex could have hunted for prey, even if it didn't use its hands.