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Daspletosaurus torosus
Axial length: 9m
Hip height: 3-5m
Weight: 3,6 metric tons
Name meaning: „Frightful lizard“ (Greek)

Daspletosaurus torosus was a Tyrannosaurinae Tyrannosaurid that inhabited territory of the modern-day Alberta and probably Montana in a geological period between circa 77 and circa 74 million years ago, or late Cretaceous Campanian. Although only a few fossil remains attributed to this specific species have been found, it is very well known. Only 7 specimens that definitely belong to Daspletosaurus have been discovered so far.
Holotype specimen of Daspletosaurus torosus was described by Dale Russel in 1970. Some specimens that have been found in Alberta and Montana allude that there were possibly more species of Daspletosaurus , not just D. torosus .

Daspletosaurus was characterized by a relatively short and tall rostrum, cranium approximately 1m long in linear dimension, and very large teeth compared to those of it’s close phylogenetic relatives. It possessed 72 teeth in total. Each tooth was curved backwards and possessed denticles, which were pointing upwards. This peculiar tooth morphology, typical for most of the Tyrannosauridae, enabled small pieces of meat to get stuck between the Daspletosaurus’ teeth, representing home for many species of toxic bacteria, giving Daspletosaurus somewhat of a septic bite. Teeth were relatively blunt and had circular bases (with the exception of premaxillary teeth, whose cross-section resembled the letter D, representing the consequence of heterodonty) what made them capable of sustaining large amounts of pressure, eventually enabling Daspletosaurus of bone-crushing bite. Therefore, strong bite force and very sharp claws were most likely primary weapons of this animal.
Its cranium was very heavily built in general. Anterior parts of it, especially nasal, were strongly fused. It had a rather unique orbit, representing somewhat of an intermediate stadium between the one seen in large advanced Tyrannosauridae, such as Tyrannosaurus and Tarbosaurus , and the one seen in more basal Albertosaurinae. Albertosaurinae possessed somewhat of a circular orbit, while advanced Tyrannosauridae possessed eliptical orbit, divided in two. It had rough outer surface of the maxilla and a crest around its orbit, covering its jugal, postorbital and lacrimal. Unlike genera like Tyrannosaurus and Tarbosaurus it possessed thickened bone above its orbits, forming a structure that resembled eyebrows in humans, as well as lacrimal horns. More advanced Tyrannosauridae did not possess such structures, and more commonly possessed horn-like structures in posterior parts of their crania.
Daspletosaurus possessed reduced front limbs (what is a synapomorphy for Tyrannosauridae), but they were proportionally larger than those seen in any other Tyrannosaurid.
It had about the same cranial:total body length ratio as its relatively close relative, Albertosaurus sarcophagus. Albertosaurus, Gorgosaurus and Daspletosaurus all possessed plantar ridge on their fourth metatarsal. This trait cannot be seen in Tyrannosaurids that lived more to the south of North America, such as Teratophoneus .
Unexpectedly, D. torosus was actually more muscular and heavily built than T. rex .

It is widely accepted that Daspletosaurus torosus was a direct evolutionary ancestor to Tyrannosaurus rex . Some notable paleontologists, such as Gregory S. Paul and Jack Horner, insist that T. rex desccended from D. torosus through anagenesis. Gregory S. Paul even re-classified D. torosus as just another species of Tyrannosaurus, Tyrannosaurus torosus . However, this idea was not widely accepted. More recent studies, notably by Steve Brusatte in 2016, suggest that T. rex was more likely an invasive species, originating from Asia. This study is correspondent with the hypothesis proposed by Phil Currie, that Tyrannosaurus’ evolutionary ancestor was Tarbosaurus , rather than Daspletosaurus .
In a study from 2006, Urban and Lamanna describe a lacrimal from Montana, dated to be 75 million years old, as belonging to Tyrannosaurus (but not neccesarily T. rex ). In this study, it is almost apparent that the specimen almost represents a „link“ between Daspletosaurus and Tyrannosaurus :

„ ¬_The jugal process of CM 9401 is noticeably anteroposteriorly thinner than that of some specimens of Tyrannosaurus rex (e.g., CM 9380), but is comparable to others (e.g., MOR 555, MOR 1125) and to Daspletosaurus (e.g., MOR 590) in this regard_ “

And while the lacrimal lacks the horn seen in Daspletosaurus it still seems to be far more similar to Daspletosaurus’ lacrimal than it is to Tarbosaurus’ lacrimal:

The lacrimal foramen is small and subcircular, as in Daspletosaurus (e.g., MOR 590) and Tyrannosaurus (e.g., CM 9380 and MOR 1125), being proportionately smaller than that in Albertosaurus and Tarbosaurus

Most of the Tarbosaurus bataar specimens are dated to be 70 million years old or slightly younger, while the youngest Daspletosaurus material is dated to be 74 million years old. This, of course, contributes to the reliability of the thesis that Tyrannosaurus descended from Daspletosaurus through anagenesis , since Tyrannosaurus remains appear to appear right when Daspletosaurus remains appear to disappear, and we basically have a transitionary specimen.
Jack Horner and his team in 1992 described a still unnamed taxon of Tyrannosaurid from Two Medicine Formation in Montana, based on at least 2-3 specimens. Jack Horner identified this taxon to be a transitionary species between Daspletosaurus and Tyrannosaurus , because it shares many morphological characteristics with both taxa. Currie however, classified this taxon as just a third species of Daspletosaurus , alongside with D. torosus and Daspletosaurus sp. from Dinosaur Park.
A less supported idea is the one suggested by paleontologist Tracy J. Thompson and colleagues in 2013, and suggests that Tyrannosaurus evolved from Tyrannosaurids characteristic for the ecosystems of southern North America, which are known to be morphologically distinct from the ones on the north.


There are multiple signs of D. torosus individuals being agressive towards each other. There are at least two specimens of D. torosus showing pathologies on their rostra that seem to match the teeth morphology of another D. torosus . Among them is a ca. 6m long and half a ton heavy subadult specimen, TMP 94.143.1, whose pathologies show signs of healing, what implies that the bite wasn’t intended to be fatal. It also shows a massive circular puncture on the posterior part of the cranium. These pathologies may allude on fights for territorial dominance, fights during mating season, or even cannibalism. However, the alternative hypothesis is that these pathologies were actually caused by an infestation by an ancestral form of Trichomonas gallinae , a protozoan parasite that infests birds and ultimately leads to death by starvation due to internal swelling of the neck. Nevertheless, the specimen shows postmortem Tyrannosaurid toothmarks on it’s right dentary, indicating it was most likely scavenged.
One specimen has a tooth embedded in its right pubis, and part of the pelvis bitten off. It is uncertain if the tooth actually belongs to Daspletosaurus , or Gorgosaurus .
Same form of pathologies resembling bite marks have been identified on FMNH PR2081, the most complete T. rex specimen, as a result of infestation.
Three D. torosus and five hadrosaur specimens have been found on the same location in Two Medicine formation. Out of 3 D. torosus specimens, one was identified to be a juvenile, another one was identified to be an adult, while it wasn’t possible to successfully determine the exact age of the third specimen. Many, such as Phil Currie, consider this find to be the proof of social predation in Daspletosaurus and Tyrannosauridae in general, since there are tooth marks of Tyrannosaurid teeth on the hadrosaur skeletons. However, even though it seems unlikely that all of these specimens have been washed to the shore by a river, it does seem possible that they died while feeding on already dead prey. One of the possible scenarios is that hadrosaurs have been poisoned by toxic volcanic gasses, and when Daspletosaurs arrived, hoping they’ll get an already cooked meal, they got poisoned too. They could also have died while competing for carcasses with Gorgosaurus or even another Daspletosaurus .
Even if they did hunt all of this prey by themselves, that does not necessarily have to imply they were social predators. As stated by Lawrence Witmer, they could have also been communal predators. Communal predation can usually be seen in modern day crocodiles and Komodo dragons. Individuals of the same species gather to hunt prey, but even though they are cooperating during the hunt, each one hunts for its own benefit. And when not hunting, communal predators live solitary, unlike social predators, which mostly tend to spend their entire lives in groups.

However, some Tyrannosaurus rex specimens, such as famous “ Wyrex “ and even FMNH PR2081, or “ Sue “, show some extremely serious pathologies, which would seriously negatively influence their hunting efficiency and general health condition and drive them into unavoidable death. However, these pathologies show clear signs of healing, and there are no signs these specimens died of consequences of these injuries, what implies these animals were fed and taken care of, as suggested by Peter Larson. This more-less proves that Tyrannosaurus rex did live in organized social communities, but it is uncertain if Daspletosaurus torosus did so as well.
Witmer compares this situation to difference in behavior between Panthera leo and Panthera leopardis . Despite them being the same genus, P. leo lives and hunts in organized social communities, while P. leopardis doesn’t. Phylogenetic relation isn’t always something to absolutely rely on.
However, in 2011, a local hunting outfitter and guide, Aaron Fredlund, unearthed two tyrannosaur track marks in the foothills of the Canadian Rockies in British Columbia. He informed paleontologist Richard McCrea and his team, which eventually described the find. Footprints of Tyrannosaurids, small theropods and Hadrosaurs were all present on the site. Trackways were dated to be approximately 70 million years old, therefore, Tyrannosaurid footprints could have been made by Albertosaurus, Gorgosaurus or Daspletosaurus . In total, 7 trackways of 3 tyrannosaurid individuals have been identified. Each footprint was approximately 19cm long in axial length. Contrary to other trackways found on the site, Tyrannosaurid ones were all parallel and appear to have been made at the same time, based on their depth, indicating that these Tyrannosaurids were moving in an organized group. All three trackways face the same direction and were made in close proximity, with 18 feet between Trackway A and B, and eight feet between B and C. According to McCrea, this represents an almost irrefutable evidence for social behavior and/or predation among Tyrannosaurids.
However, McCrea and his team identified footprints as distinct enough to be classified into their own taxon Bellatoripes fredlundi (“warlike foot”), so this might not represent direct evidence of social predation in Daspletosaurus specifically.
These footprints are also extremely important because they clearly imply that these animals lifted their feet out in a backwards motion, in contrary to the rest of predatory dinosaurs, which lifted their feet in a forwards motion.

Daspletosaurus torosus coexisted with its relatively close cousin, Gorgosaurus libratus . However, D. torosus probably did not compete with G. libratus , because they most likely had different ecological niches. Due to its more gracile musculoskeletal morphology, longer and legs more suited for fast running, and more shallow rostrum G. libratus’ diet probably mostly consisted out of smaller and quicker animals, while D. torosus , due to its extremely muscular morphology, deep rostrum and teeth designed to provide bone-crushing bite, probably mostly focused on hunting large ceratopsids and hadrosaurs. Evidence for this comes from fragments of an immature hadrosaur skeleton found in the stomach of Daspletosaurus specimen from Two Medicine Formation, suggesting that it did feed on them. However, it can also imply that it just hunted whatever it could, because it was undoubteldy the apex predator in its ecosystem.
Gorgosaurus specimens are more common on the north, while Daspletosaurus specimens appear to be more common in the south. Thomas Holtz noted that large ceratopsids and hadrosaurs, notably Chasmosaurinae and Hadrosaurinae, also were more common on the south, and that, during later Maastrichtian, Albertosaurinae (including Gorgosaurus itself), Centrosaurinae and Lambeosaurinae almost went extinct, while Tyrannosaurinae, such as Tyrannosaurus rex , Chasmosaurinae and Hadrosaurinae were thriving. This clearly implies that Gorgosaurus and Daspletosaurus were also geographically isolated, and that the type of ecosystem that Daspletosaurus lived in was slowly taking over the ecosystem that Gorgosaurus inhabited.

Daspletosaurus torosus holotype was originally found in Oldman formation, in Alberta, Canada, by a prolific fossil-hunter Charles M. Sternberg in 1921. and identified as a specimen of Gorgosaurus libratus , but further analysis, conducted by Dale Russel in 1970. showed that D. torosus was far more robust, had different cranial morphology, different dental morphology, shorter hind limbs, longer front limbs, etc.
Russel also described another specimen, AMNH 5438, as D. torosus paratype. This specimen was originally excavated by Barnum Brown in 1913 in Upper Oldman formation, now known as the Dinosaur Park formation.
Another specimen discovered by Brown in Dinosaur Park formation in 1914, was sold by American Museum of National History to Field Museum of National History in Chicago in 1954, where it was identified as Albertosaurus libratus , since Gorgosaurus libratus was still considered to be a junior synonym of Albertosaurus . This specimen, FMNH PR308, consists out of a nearly complete skeleton and some cranial material, and has later been re-classified as Daspletosaurus . However, these specimens have sparked some controversy recently, because it appears that they have enough autapomorphies to be classified as their own taxon, as claimed by Currie in 2003.
Daspletosaurus was one of the first Tyrannosauridae to be discovered with a clavicle. Before this, it was believed that Tyrannosauridae lacked clavicle absolutely.

1. Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology.
2. Currie, Philip J. (2003). "Cranial anatomy of tyrannosaurids from the Late Cretaceous of Alberta". Acta Palaeontologica Polonica.
3. Paul, Gregory S. (1988). Predatory Dinosaurs of the World. New York: Simon & Schuster.
4. Urban, Michael A.; Lamanna, Matther C. (2006)” Evidence of a giant Tyrannosaurid (Dinosauria: Theropoda) from the upper Cretaceous (?Campanian) of Montana”
5. Horner, John R.; Varricchio, David J.; Goodwin, Mark B. (1992). "Marine transgressions and the evolution of Cretaceous dinosaurs". Nature.
6. Thomson, T., Irmis, R., Loewen, M. 2013. First occurrence of a tyrannosaurid dinosaur from the Mesaverde Group (Neslen Formation) of Utah: Implications for upper Campanian Laramidian biogeography. Cretaceous Research.
7. Switek, Brian (2013) “Scrappy Utah Dinosaur Contributes Clues About Tyrannosaur History
8. Hone, D. W. E.; Tanke, D. H. (2015). "Pre- and postmortem tyrannosaurid bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada". PeerJ.
9. Geggel, Laura (2015) “Tyrannosaur Skull Bears Scars of Fierce Dino-Battle” LiveScience.
10. McCrea, R., Buckley, L., Farlow, J., Lockley, M., Currie, P., Matthews, N., Pemberton, S. 2014. A ‘terror of tyrannosaurs’: The first trackways of tyrannosaurids and evidence of gregariousness and pathology in tyrannosauridae. PLoS ONE.
11. Switek, Brian (2014) “Tracks Hint at the Social Life of Tyrant Dinosaurs” Laelaps. National Geographic
12. Ghose, Tia (2014) “Tyrannosaurs “Gangs” Terrorized Ancient Landscape” LiveScience
13. Farlow, James O.; Pianka, Eric R. (2002). "Body size overlap, habitat partitioning and living space requirements of terrestrial vertebrate predators: implications for the paleoecology of large theropod dinosaurs". Historical Biology.
14. Holtz, Thomas R. (2004). "Tyrannosauroidea". In Weishampel, David B.; Dodson, Peter; & Osmólska, Halszka (eds.). The Dinosauria (Second ed.). Berkeley: University of California Press.
15. Carr, Thomas D. (1999). "Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria)". Journal of Vertebrate Paleontology.
16. “Daspletosaurus” on Prehistoric Wildlife
17. “Daspletosaurus” on Australian Museum
18. McNab, Chris; Benton, Michael (2016) “The complete guide to Dinosaurs and other extinct reptiles” Marshall Editions, London
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Here's an episode of Dino Talk regarding T. rex' potential close relative.
A new episode of Dino Talk! This time, we discuss about Gualicho shinyae!

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Is Gualicho a Tyrannosauroid or not? Share your opinion in the comments below!
~ Gualicho shinyae profile~

Gualicho is a relatively newly discovered genus of a Theropod dinosaur, originally referred to as “Nototyrannus”, found in Huincul formation, discovered in 2007 by Akiko Shinya, described by Sebastian Apesteguia and colleagues in year 2016, and dated to be ca. 94-90 million years old. That would place it in the late Cenomanian-early Turonian age of the upper Cretaceous Period, what would indicate that it coexisted with some of the largest terrestrial predator ever, such as famous Giganotosaurus carolinii and Mapusaurus roseae . Type species, and currently the only one described, is G. shinyae . It’s genomial name, Gualicho , derives from the name of a demon from Mapuchine mythology, called gualichu/gualicho, while it’s type species’ name, G. shinyae , derives from his original excavator’s last name, Shinya.

Not much material is known from this animal. It is known solely from a holotype specimen, MPCN PV 0001, which includes 3 caudal vertebrae, 4 posterior-dorsal vertebrae, a nearly-complete left scapula, 3 pairs of gastraliae, 2 ribs, a partial ischium (the lower part), a complete left femur, partial right tibia and fibula, fragments of metatarsi, 3 phalanxes from the right foot, and most importantly, an anterior part of the forelimb, including nearly completely preserved manus, ulna and radius. Based on that, we know for sure that G. shinyae possessed reduced front limbs compared to those seen in closely related taxa. They were only 60cm (2 feet) long. It’s first and second metacarpal were fused proximally, and metacarpal 3 most likely had no phalanx, meaning that the animal had didactyl manus, while the first metacarpal is the most robust. First and second digits undisputedly possessed nails. The animal was also characterized by just two manual digits, what resulted in it being often compared to Tyrannosauridae, most notably Tyrannosaurus rex . “The Guardian” even published a text describing Gualicho as “a distant relative of T. rex “. However, this one peculiar synapomorphy with Tyrannosauridae does not indicate that Gualicho was a member of it. Gualicho shares most of its morphological traits with Allosauridae. It shares most of its traits with Deltadromeus agilis , such as nearly identical scapula, coracoid and femur, with elongated spinal processes in intermediate caudal vertebrae resembling those of Bahariasaurids and Tyrannosauroids the most. This indicates that process of front-limb reduction during evolution cannot be seen only in Tyrannosauroidea and Abelisauridea, but in Allosauride as well. Knowing this, it seems like the reduced front limbs with two manual digits were a common pattern in Theropod anatomy, appearing multiple times individually throughout the Theropod evolution. But the reason behind it is still mysterious. Nathan Smith, one of the co-authors of the original paper describing G. shinyae hypothesizes that it is due to these taxa’s increasingly strong bite force. There is basically no function for the front limbs, alongside with a strong bite force. Plus, strong bite force mostly requires very large and robust cranium, especially in it’s posterior section, so, an animal possessing both long and muscular front limbs as a form of weapon, as well as a robust cranium designed to provide enormous bite force, would probably be extremely front heavy, and would have a pretty hard time balancing all that unusually distributed weight.
However, there must have been a function for these front limbs, otherwise they would have disappeared entirely throughout the evolution.
Smith believes that while there may only be a limited number of ways to evolve reduced forelimbs, the differing anatomy and shape of the limbs and hands between short-armed dinosaurs hints there could be a range of evolutionary pressures at play.
Based on it’s hindlimb material, we know the animal’s hindlimbs were elongated, alluding on a fast and quick type of terrestrial locomotion. It’s tibia had some morphological attributes seen in Coelurosauria, but is in fact, pretty similar to a basal Tetanuran’s tibia, while fibula mostly matches the one seen in Deltadromeus .
Based on comparison with closely related taxa, it is estimated that G. shinyae measured somewhere between 6 and 7.6m in axial length, and half a ton in weight.

It is known that, back in Cenomian and Turonian, Patagonia was a separate landmass from the supercontinent of Gondwana. Huincul formation, being located in Patagonia, puts G. shinyae , as well as other taxa that shared the environment with it, such as A. huinculensis, G. carolinii, M. roseae etc., in this isolated habitat. Considering that it shared it’s environment with previously mentioned large predators, it most definitely was an opportunistic predator, feeding on smaller prey, as well as on carcasses left by apexes. It’s significantly reduced forelimbs described earlier also point on this type of behavior.

As seen in the “Morphology” section, G. shinyae has a shows a wide variety of characteristics seen both in Tetanurae and in Ceratosauria. However, the original analysis of the taxon did not focus precisely on determining cladistic position of Gualicho , it only says that Gualicho was a sister taxon to Deltadromeus , and using pretty mucg controversial hypothesis about Deltadromeus being a Carnosaur, to put Gualicho in Carnosauria as well. And, not to mention that there is an enormous amount of controversy revolving around D. agilis’ taxonomic position. Sereno originally classified D. agilis as a basal coelurosaur with unusually large body proportions. However, a later study committed by Sereno, Wilson, Srivastava, Bhatt, Khosla and Sahni in 2003 stated that D. agilis was actually a member of Noasauridae, a ceratosaurian clade closely related to more advanced Abelisauridae. However, Carrano and Sampson positioned Deltadromeus in basal Coelurosauria, as a genus closely related to genera like Elaphrosaurus and Limusaurus , in their study from 2008. However, Rahut and Carrano re-positioned Deltadromeus, Elaphrosaurus and Limusaurus all in Noasauridae in their 2016 paper.
Even thought G. shinyae is as impressive as it is, the fact that it is it’s own genus is dubious. Mickey Mortimer, Andrea Cau and Brad McFeeters all noted obvious similarities between Aoniraptor and Gualicho . First off, both genera are identified to have lived in the identical temporal range (96-90 mya), are found in the same formation, and are both very closely related to Deltadromeus agilis . Gualicho’s caudal vertebrae measure ca. 87cm in axial length according to the original analysis by Apesteguia et al., while Aoniraptor’s caudals measure ca. 83m in axial length according to Motta et al. Mickey Mortimer adds:
Both genera possess anterior mid-caudal vertebrae with fan-shaped prezygapophyses lacking a discernible articular surface for contacting the postzygapophyses; presence of a blunt and thick process on the lateral surface of the prezygapophyses of anterior midcaudal vertebrae, and might have the third - mid-posterior caudals with a pair of nonarticular flat surfaces located on the posterodorsal corner of the centrum .”
Although Gualicho’s and Aoniraptor’s vertebrae show some minor and ignorable differences, they may have been a result of individual variety, sexual dimorphism, or the difference in species, considering that no one implied that they were the same species, just the same genus.
In case this interpretation is correct, then Gualicho would not be a valid name anymore, because Aoniraptor is older. Although Gualicho was named just a month after Aoniraptor, Aoniraptor is still older, no matter how small the chronological span between the namings was.
In an analysis of Aoniraptor by Novas, Motta, Rolando, Rozadilla, Agnolin, Chimento, and Egli, Aoniraptor/Gualicho was found along with Deltadromeus and Bahariasaurus to probably form a new family of megaraptoran tyrannosauroids, different from the Megaraptoridae… So there is still a chance that “ T. rex like Allosaurid” was not actually an Allosaurid, but literally, a T.rex’ relative.

1. Sebastián Apesteguía; Nathan D. Smith; Rubén Juárez Valieri; Peter J. Makovicky (2016). "An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina". PLoS ONE.
2. Matías J. Motta, Alexis M. Aranciaga Rolando, Sebastián Rozadilla, Federico E. Agnolín, Nicolás R. Chimento, Federico Brissón Egli, and Fernando E. Novas (2016). "New theropod fauna from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina". New Mexico Museum of Natural History and Science Bulletin 71: 231–253.
3. Mickey Mortimer (2016) “Is Gualicho Aoniraptor?” The Theropod Database (
4. Andrea Cau (2016) “New remains of Aoniraptor? Uh ... welcome, Gualicho!” Theropoda Blog (|en&tbb=1&ie=UTF-8)
5. David Blagić (2016) “Deltadromeus agilis species profile“ Google Plus (
Btw I know I am referencing myelf ...
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A small review of king's close relative, Gorgosaurus !
A new episode of "Dino Talk"! In this episode, we will be discussing about famous Gorgosaurus ! :D

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A small profile of kings close cousin, Gorgosaurus libratus !
~ Gorgosaurus profile~

Gorgosaurus libratus is a large tyrannosaurid from what today is North America. Its remains were found all across modern Canada, from Provincional Park, up to the northern Alaska. It was about 9-10m long in linear dimension, and up to 3,5m tall at the pelvis. It was sister genus to Albertosaurus , and belongs to a subfamily of Tyrannosauridae, called Albertosaurinae. Albertosaurinae are known for being much more gracile and much more lightly built than Tyrannosaurinae, another subfamily of Tyrannosaurinae. Another distinguishing characteristic of Albertosaurinae are much more visible orbital horns, longer tibiae and metatarsi (and legs in overall), as well as teeth quite unusual for Tyrannosauroidea. Tyrannosauroids are known for possessing robust teeth, with very blunt tips, more suited for crushing bones and piercing through tough skin and osteoderms, rather than for slashing through flesh. Albertosaurinae possessed  less robust teeth with very sharp edges and tips, usually with more denticles. This, combined with the fact that Albertosaurinae were more gracile than Tyrannosaurinae and that their legs were more suited to provide fast running speeds, we can safely conclude that Tyrannosaurinae most likely hunted highly armored animals, such as Ankylosaurs, and that Albertosaurinae hunted more gracile and much faster prey, such as large Ornithomimosaurs and smaller Ornithopods. Especially if we add the fact that many species of Tyrannosaurinae coexisted with Albertosaurinae, such as in case of Gorgosaurus libratus and Dasletosaurus torosus .
There are differences in musculoskeletal morphology between juvenile and adult individuals of Gorgosaurus as well. Juveniles are believed to have possessed longer legs than adults, as well as tibiae longer than femora and proportionally larger metatarsi, contrary to adults, which possessed much more robust legs, with femora equally long as tibiae, and short meatatarsi compared to those seen in juveniles. This might indicate that juveniles hunted different prey than adults, or that both participated in pack hunting, juveniles providing speed and agility, and adults providing sheer strength.
Holotype specimen of Gorgosaurus libratus also includes a skin impression, described by Philip J. Currie as:
 " Smooth naked skin lacking the scales of other dinosaurs ."
As plumage is really difficult to preserve, this small patch of skin might have bore feathers in real life. Plumage in this animal was most likely present in two forms – morphotype B (plumulaceous) and morphotype C (basal pennaceous, also seen in basal modern Aves, such as Struthio camelus ) feathers. Feathers would have probably been used for display, as well as for providing additional heat, as Gorgosaurus was living in a really cold environment. Plumage would be especially useful during long and very cold winters that were present during this geological period, especially in Alaska, where fossils of Gorgosaurus have also been excavated.
A specimen of Gorgosaurus from Natural History Museum in Indianopolis is very well known for its stunning pathologies. It has 2 caudal vertebrae fused together, due to a very hard fracture. It also has a compound fracture on its right fibula, as well as a huge fracture between scapula and coracoid, where the shoulder joint is supposed to be located and a smaller, but still highly visible fracture between the two dentaries. It is simply stunning how this animal managed to survive. Paleontologists today mostly agree that it is due to a care inside of a social group, as well as very fast metabolism and much more powerful immunity system than ours.

Artwork by Sergey Krasovskiy.

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A great announcement on the channel!
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