A Gorgosaurus feeding on a Citipes
Illustration by Julius Csotonyi
75 million years before creationists think Earth was created, a juvenile Gorgosaurus, a species of tyrannosaur, was catching young avian dinosaurs like Cities but then selectively eating the fleshiest parts, the legs.
At this stage in its life, the Gorgosaurus was slender, had a narrow skull and blade-like teeth and was able to catch small, swift running dinosaurs, but had it lived to grow into an adult, it's body and particularly its head and teeth, would have become massive and capable of catching the large vegetarian dinosaurs and crushing their bones.
We know this because this particular juvenile Gorgosaurusdied and its body became fossilised, complete with the leg bones of two young Citipes still in its stomach, one more digested than the other, showing they were eaten at different times.
This was discovered by a group of palaeontologists led by Dr. Darla Zelenitsky, PhD, an associate professor in the Department of Earth, Energy and Environment at the University of Calgary, and Dr. François Therrien from the Royal Tyrrell Museum. Their finding is published, open access, in the journal Science Advances. It is described in a University of Calgary news item:
The difference between a juvenile and adult tyrannosaur is massive — both figuratively and literally.Technical details are given in the team's published paper. I've included the introduction as this gives background to the species and the fossil record:
While adults weighed around 3,000 kilograms, the weight of a pick-up truck, juveniles were much leaner. Adults had massive skulls, robust teeth and were capable of generating bone-crushing bites, while juveniles were long-legged with slender skulls and blade-like teeth.
Now, paleontologists from UCalgary and the Royal Tyrrell Museum have discovered that as the body of a tyrannosaur changed throughout its lifespan, so did its diet.
[…]
The research was the result of a groundbreaking discovery: a juvenile Gorgosaurus with prey found in its stomach. This remarkable specimen broadens our understanding of the feeding habits of these iconic meat-eating dinosaurs.
The prey found inside the gut region was the hind legs of two young, bird-like theropod dinosaurs of the species Citipes elegans.This is the first time that such well-preserved stomach contents have been found inside the skeleton of a large species of tyrannosaur.
Dr. Darla K. Zelenitsky, co-corresponding author
Department of Earth, Energy, and Environment
University of Calgary, Calgary, Alberta, Canada.
The well-preserved juvenile Gorgosaurus was found in Dinosaur Provincial Park by Darren Tanke, a technician at the Royal Tyrrell Museum of Paleontology. Gorgosaurus, a species of tyrannosaur, lived about 75 million years ago in what is now Alberta. When the dinosaur died it was between the ages of five and seven, weighed only 335 kilograms — just over 10 per cent the mass of an adult individual — and was four metres long.
While it wasn’t immediately obvious that there was prey inside of the specimen, during preparation work in the museum's lab, staff noticed small toe bones protruding from the ribcage.
The size of a juvenile Gorgosaurus compared to the size of a young prey Citipes.
Illustration by Julius Csotonyi
Royal Tyrrell Museum
The right side of Gorgosaurus juvenile with prey items in the stomach, visible in the lower centre of skeleton.
Photo: Darla Zelenitsky
The left and right side of Gorgosaurus juvenile with prey items in the stomach
Photo: Darla Zelenitsky
Zelenitsky explains that the juvenile Gorgosaurus likely only ate the hind limbs from the small prey because it was the meatiest part of the animal.The rock within the ribcage was removed to expose what was hidden inside. Lo and behold, the complete hind legs of two baby dinosaurs, both under a year old, were present in its stomach.
Dr. François Therrien, co-corresponding author
Royal Tyrrell Museum of Palaeontology
Drumheller, Alberta, Canada.
It’s unclear whether Gorgosaurus had a preference for Citipes, or if this particular species was simply an abundant prey at a certain time of year. What this discovery does mean is that juvenile tyrannosaurs’ narrow skulls and blade-like teeth meant they were suited for capturing and dismembering small, swift prey while adult tyrannosaurs’ massive skulls and robust teeth meant they could eat much larger prey like megaherbivores, including duck-billed and horned dinosaurs.The two individuals were probably eaten at different times because the bones of one were more digested than the other. Regardless, it appears that this teenage dinosaur definitely had an appetite for drumsticks.
It’s well-known that tyrannosaurs changed a lot during growth, from slender forms to these robust, bone-crushing dinosaurs, and we know that this change was related to feeding behaviour. They appear to have gone from hunting prey like Citipes — a small fraction of their size — as teenagers to hunting megaherbivore dinosaurs — as large, or larger, than their size — as adults.
Dr. Darla K. Zelenitsky.
While this is only one unique fossil, Zelenitsky and Therrien are hopeful that more specimens will be found to give clues as to what else was on the menu for teenage tyrannosaurs.
Overall, this Gorgosaurus specimen gives direct evidence that tyrannosaurs were changing their diet as they grew from juveniles to adults. This study is a leap forward for the world of paleontology research and fascinating new information for anyone intrigued by these creatures who roamed our earth 75 million years ago.
AbstractSo, dinosaurs were eating other dinosaurs 75 million years before creationists think Earth was created! But there is something even more subtle that should worry those creationists who can do joined-up thinking. In their mythology, before their god's genocidal flood, all animals were vegetarian (to get round the fact that the carnivores on the Ark would have eaten the vegetarians) and have since become carnivores. They also believe all fossils were formed during this genocide and all sedimentary rocks were laid down then, about 4,000 years ago.
Tyrannosaurids were large carnivorous dinosaurs that underwent major changes in skull robusticity and body proportions as they grew, suggesting that they occupied different ecological niches during their life span. Although adults commonly fed on dinosaurian megaherbivores, the diet of juvenile tyrannosaurids is largely unknown. Here, we describe a remarkable specimen of a juvenile Gorgosaurus libratus that preserves the articulated hindlimbs of two yearling caenagnathid dinosaurs inside its abdominal cavity. The prey were selectively dismembered and consumed in two separate feeding events. This predator-prey association provides direct evidence of an ontogenetic dietary shift in tyrannosaurids. Juvenile individuals may have hunted small and young dinosaurs until they reached a size when, to satisfy energy requirements, they transitioned to feeding on dinosaurian megaherbivores. Tyrannosaurids occupied both mesopredator and apex predator roles during their life span, a factor that may have been key to their evolutionary success.
INTRODUCTION
Tyrannosaurids are a clade of carnivorous dinosaurs that dominated the ecosystems of Asia and North America near the end of the Cretaceous period [~80 to 66 million years (Ma) ago] (1–4). Among the largest terrestrial predators to have ever existed, tyrannosaurids grew from meter-long hatchlings to multiton sizes (9- to 12-m long, 2000 to 6000 kg) over the course of their life span (3–5). Juveniles were gracile with narrow skulls, blade-like teeth, and long slender hind limbs, whereas adults were robust with massive skulls and large incrassate teeth and were capable of generating bone-crushing bites (3, 4, 6–11). These marked morphological changes suggest that tyrannosaurids underwent a major ontogenetic dietary shift, in which immature/juvenile and mature/adult individuals occupied different ecological niches (7, 10, 12, 13). Fossil evidence reveals that dinosaurian megaherbivores (i.e., species with an adult mass > 1000 kg, including ceratopsids, giant ornithomimosaurs, hadrosaurids, and sauropods) were common prey items of large tyrannosaurids (8, 14–20), a diet for which the necessary craniodental adaptations and bite forces only developed when individuals reached late juvenile or early subadult growth stages (7, 10, 11, 21). Unfortunately, fossil evidence for diet in young tyrannosaurids is largely unknown, thus limiting our understanding of ontogenetic dietary shifts in these iconic predators.
Providing direct fossil evidence of diet and feeding behavior in young tyrannosaurids, here, we report on an articulated skeleton of a juvenile Gorgosaurus libratus from the Upper Cretaceous Dinosaur Park Formation (~75.3 Ma) of Alberta, Canada (see Supplementary Text), that preserves the remains of two small caenagnathid theropods (Oviraptorosauria) in its abdominal cavity (Fig. 1, A to C). This specimen [Royal Tyrrell Museum of Palaeontology (TMP) 2009.12.14] represents, to our knowledge, the first instance of in situ stomach contents (i.e., preserved in proper anatomical position) for a tyrannosaur and provides direct fossil evidence of diet and feeding behavior in a young tyrannosaurid.
Fig. 1. Juvenile Gorgosaurus TMP 2009.12.14 preserving stomach contents.
Photographs of specimen in (A) right lateral view and (B) left anterolateral view. (C) Interpretive illustration of specimen in right lateral view. Skeleton consists of a nearly complete skull, the left side of the body and limbs, and a nearly complete pelvis. Red rectangle delineates location of stomach contents. (D) Histological photomicrograph of tibia showing the presence of five lines of arrested growths and two annuli (marked by asterisks), indicating that the individual was between 5 and 7 years old. Scale bars, 50 cm (A) to (C) and 1 mm (D).
Fig. 3. Stomach contents of juvenile Gorgosaurus. Photograph (A) and interpretive illustration (B) of stomach contents. Some of the caenagnathid bones are truncated and weathered due to modern erosion along the ventral abdominal region. Light blue and dark blue elements are the left and right hindlimbs, respectively, of the anterior Citipes individual. Light green elements are the hindlimbs and caudal vertebrae of the more posterior Citipes individual. Dark green elements represent the manual unguals of the posterior Citipes individual. White elements represent the juvenile Gorgosaurus. Fe, femur; Ti, tibia; Fi, fibula; MT, metatarsal; dig, pedal digit. Scale bar, 10 cm. See Supplementary Text for detailed identification.
François Therrien et al. ,
Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator.
Sci. Adv. 9, eadi0505(2023). DOI:10.1126/sciadv.adi0505
Copyright: © 2023 The authors.
Published by the American Association for the Advancement of Science. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
Yet here we have a fossil with the remains of a meat meal in its stomach (as well as the teeth of a carnivore).
How can this be if the mythology is correct?
According to creationists such as Ken Ham and Kent Hovind, Tyrannosaurus were originally herbivores created 6000 to 10,000 years ago along with the the first humans. They were herbivores until the day Adam and Eve ate a forbidden apple and caused Original Sin or The Fall. This is a silly myth. It's fake science, fake history, and fake reality. The world never was a Garden of Eden, it never was a Paradise, it never was a Peaceable Kingdom. The world was always the cruel, violent, hostile, dangerous deadly screwed up place that's so familiar to us. It's not Paradise Lost but it's rather a Paradise That Never Was. Paradise only exists in our wishful thinking, myths, and fairytale and movies. It does not exist in reality, sad to say.
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