Aviatyrannis | The “Tyrant’s Grandmother” of Portugal’s Late Jurassic

Aviatyrannis | The “Tyrant’s Grandmother” of Portugal’s Late Jurassic

Aviatyrannis jurassic was a small theropod which thrived in modern day Western Europe about 150 million years ago. Despite its dimunitive size, it was likely a ferocious little predator, preying on smaller dinosaurs and mammals.

Aviatyrannis Key Facts

KeywordFact
Aviatyrannis pronunciationay-vee-ah-ty-ran-nis
Meaning of nameTyrant’s Grandmother
Etymology of nameFrom Latin avia, “grandmother”, and tyrannus, “tyrant”
GroupTheropod
FamilyTyrannosauridae
GenusAviatyrannis
Type SpeciesAviatyrannis jurassic
DietCarnivore
When it Lived157.3 to 152.1 MYA
Period & TimeLate Jurassic
EpochKimmeridgian
Length3.3 ft
Height1.6 ft
Weight8-10 lbs
MobilityMoved on two legs
First Discovery2000 by Oliver Walter, Mischa Rauhut
Location of first findAlcobaça Formation, Leiria, Portugal
First Described by2003 by Oliver Walter, Mischa Rauhut
HolotypeIPFUB Gui Th 1

Aviatyrannis Name, Taxonomy and Timeline

A colored illustration of Aviatyrannis, a small, bipedal dinosaur from the Late Jurassic period. This dinosaur, depicted with a reddish-brown body, is known for its small size and bird-like features.

The name Aviatyrannis Jurassic is a funny nod to the larger and better known members of tyrannosauroids that would come later.

Avia, is Latin for grandmother, and was likely inspired by the fact that it is one of the earliest tyrannosauroids. So, an evolutionary grandmother if you like (not necessarily true) to better known theropods like Tyrannosaurs Rex.

The type species name Aviatyrannis Jurassic was based on the fact that it hails from the Late Jurassic Period, living around 150 MYA. This places it in the Kimmeridgian epoch, a time when the Earth was a vastly different place than it is today.

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Fossil Evidence

The paleontologists Oliver Walter and Mischa Rauhut made the first discovery of Aviatyrannis in 2000. The find was made in a coal mine in Guimarota, near Leiria, Portugal. Walter and Rauhut later described the dinosaur in 2003. The initial discovery was a part of the right ilium (part of the pelvic bone) and measured only around 3-4 inches.

It was first referred to as Stokesosaurus. However, the distinctiveness of the material justified a separate genus, leading to the name Aviatyrannis jurassic.

An illustration of fossil remains attributed to Aviatyrannis, a small theropod dinosaur from the Late Jurassic period. The image shows bones, including a femur and vertebra, with a scale indicating a length of about 5 cm.
Conty, CC BY 3.0, via Wikimedia Commons

The holotype, IPFUB Gui Th 1, was found in a layer of the Alcobaça Formation dating from the early Kimmeridgian, about 155 million years old. It consists of a right ilium. Rauhut in 2003 referred two other bones to Aviatyrannis: IPFUB Gui Th 2, a partial right ilium, and IPFUB Gui Th 3, a right ischium.

The referred elements represent slightly larger individuals. Additionally, sixteen isolated teeth were referred: IPFUB GUI D 89–91: three teeth of the premaxilla, and IPFUB GUI D 174–186: thirteen teeth of the maxilla and dentary.

Aviatyrannis Size and Description

Aviatyrannis was a small, bipedal predator—a characteristic feature of early tyrannosauroids. Its body was likely streamlined for efficient movement, with a long tail for balance. The dinosaur’s head would have been home to sharp, elongated teeth, perfect for gripping prey.

As I mentioned above, quite a few teeth have been found that have been identifed as belonging to Aviatyrannis Jurassic.

As an early tyrannosauroid, it provides valuable insights into the evolution of this group of dinosaurs. The holotype specimen, for example, is an ilium only ninety millimeters long. In 2016, Gregory S. Paul estimated size based on this specimen and suggested that the holotype possibly belongs to a juvenile.

The ilium is elongated and low, with the typical tyrannosauroid vertical ridge on the outer blade surface above the hip joint. This is not the only fossil evidence that hints at its lifestyle, however. Its teeth were built for a predatory lifestyle of tearing through prey and have their own unique shape and build.

Size and Weight of Type Species

A size comparison illustration of Aviatyrannis jurassica and a human. The dinosaur is shown to be significantly smaller than the human figure, with two different size estimates based on specimens "PP 11851 coll" and "DFMMh/FV 796".
Conty, CC BY 3.0, via Wikimedia Commons

As per the estimates of Gregory S. Paul in 2016, Aviatyrannis was approximately 3.3 ft long and weighed around 8-10 lbs. This estimation is based on the size of the ilium holotype specimen. However, it’s worth noting that this specimen possibly belongs to a juvenile, suggesting that adult Aviatyrannis could have been slightly larger. Despite this, it was still a rather small dinosaur, especially when compared to its later tyrannosaurid relatives.

The Dinosaur in Detail

While the size of this dinosaur may be small when you compare it to its later relatives, it has several traits that make it recognizeable as a tyrannosaurid.

The ilium is elongated and low, with a vertical ridge on the outer blade surface above the hip joint. This is a typical tyrannosauroid feature and is indicative of the dinosaur’s bipedal locomotion. The ilium’s structure would have allowed for the attachment of strong muscles, aiding in the dinosaur’s movement.

Its teeth moreover are particularly interesting. The premaxilla teeth have a D-shaped cross-section, a feature not commonly seen in other dinosaurs. This unique dental structure might have given Aviatyrannis an edge when it came to hunting and feeding.

The maxillary and dentary teeth, found in the main body of the upper jaw and the lower jaw, respectively, were elongated and recurved near the top. They also had perpendicular denticles on both edges, which would have made them effective tools for tearing flesh.

The Aviatyrannis in its Natural Habitat

This dinosaur lived in Europe during the Late Jurassic period, a time when the Earth was an unrecognizable place compared to today. The climate was likely warm and humid with lush vegetation covering the landscape. As a carnivore, Aviatyrannis would have been a predator, hunting smaller animals for food. Its sharp, elongated teeth would have been perfect for gripping prey and tearing flesh.

The dinosaur’s bipedal locomotion and smaller size suggest that it was a fast and agile hunter. It would have moved on two legs and used its long tail for balance. This would have allowed it to navigate the dense vegetation of its environment and chase after prey.

While not much is known about the social behavior of Aviatyrannis, it’s possible that it was a solitary hunter, like many other theropods.

Interesting Points about Aviatyrannis

  1. The fossil remains are very similar to another ancient tyrannosaur, Stokesosaurus, from North America. This has led to speculation that Aviatyrannis might be a junior synonym of Stokesosaurus.
  2. The discovery of fossils in Portugal proves that early tyrannosaurs made their way to Europe, probably from North America. This helps explain the presence of Eotyrannus, a later tyrannosaur from the early Cretaceous discovered in the British Isles.
  3. The teeth are unique among tyrannosauroids. The premaxilla teeth have a D-shaped cross-section, while the maxillary and dentary teeth are elongated and recurve near the top. They also have perpendicular denticles on both edges.
  4. The ilium is elongated and low, with a vertical ridge on the outer blade surface above the hip joint. This is a typical tyrannosauroid feature and is indicative of the dinosaur’s bipedal locomotion.

Contemporary Dinosaurs

This predator would likely have been both hunting and possibly prey for other predators. These European dinosaurs, each with their own unique traits, were part of a complex ecosystem that intertwined their lives in a delicate balance of survival and competition.

The Allosaurus, a larger carnivorous dinosaur, was a formidable presence. Its size and predatory nature might suggest a potential threat to Aviatyrannis. Yet, the Aviatyrannis could have used its smaller size and agility to navigate the landscape with a nimbleness that allowed it to coexist and possibly even evade this larger predator. The Ceratosaurus, another carnivorous contemporary, adds another layer to this back-and-forth between predator and prey. Its distinctive horn and large body size set it apart, yet it shared the same world as the Aviatyrannis and Allosaurus.

The Stegosaurus and Hylaeosaurus, both herbivores, present an interesting contrast to Aviatyrannis. While they would not have been direct competitors for food, their presence would have contributed to the overall dynamics of the environment. Aviatyrannis might have observed these larger dinosaurs from a distance, their interactions providing valuable insights into the behaviors and habits of different species. This coexistence paints a picture of a diverse and vibrant ecosystem where each creature, from the smallest Aviatyrannis to the largest Ceratosaurus, played a crucial role.

Frequently Asked Questions

What does the name mean?

The name Aviatyrannis translates to Tyrant’s Grandmother’.

When did it live?

It lived during the Late Jurassic period, specifically the Kimmeridgian epoch. This places its existence around 157.3 to 152.1 million years ago.

What did it eat?

As a carnivore, it would have eaten meat. It likely hunted smaller animals for food.

How big was it?

This was a rather small dinosaur. It’s estimated to have been around 3.3 feet long and weighed about 0.004 tons.

Where were the fossils found?

The fossils were first discovered in Leiria, Portugal, in the year 2000 by German paleontologist Oliver Walter Mischa Rauhut.

What makes this dinosaur unique?

It is unique for its small size and distinctive teeth. The premaxilla teeth have a D-shaped cross-section, a feature not commonly seen in other dinosaurs.

Sources

Article last fact checked: Joey Arboleda, 12-27-2024

Featured Image Credit: IJReid, CC BY 4.0, via Wikimedia Commons