Yesterday saw the arrival of the newly named Nanuqsaurus, a surprisingly small tyrannosaur from Northern Alaska. While this has been called a dwarf or pygmy in some quarters, it is hardly small with an estimated size of around 5 m in total length (though based on very fragmentary remains). It may be a surprise to learn there are small tyrannosaurs out there – attention does tend to focus on the giants like Tyrannosaurus, but their forebears were rather smaller.
Early forms (including the British Eotyrannus and Proceratosaurus) were smaller still, and there are plenty of members of this group that were closer to the size of Nanuqsaurus than the giants. Indeed there is something of a general evolutionary pattern in tyrannosaurs with ever later species being ever larger than earlier animals. This is in part, the oddity about the new discovery, all of its nearest relatives (Tyrannosaurus, Tarbosaurus, Zhuchengtyrannus, Daspeltosaurus, Lythronax) are rather larger, in fact some are more than twice as long as the new animal. That alone would make it something of an outlier compared to what would be expected, but another aspect adds to the unusual nature of it being such a small animal.
There are several common evolutionary phenomena associated with body size and how it varies under certain environmental conditions. Famously animals trapped on islands often change size quite dramatically, and the “Island Rule” suggests that small animals often get larger while large forms get small. Even modern red deer on Scottish islands tend to be smaller than their mainland counterparts, while the Mediterranean islands played host to pygmy elephants but also giant swans, and a series of dwarf dinosaurs have been recovered from modern Romania, which was an island at the time. Smaller animals free from the pressures of predators (which are rare or absent on islands) can get larger, while larger animals, with reduced food available, adapt by shrinking. Similarly, “Bergmann’s Rule” is that animals closer to the poles tend to be larger, where a larger mass to surface area ratio will help them keep warm.
This then is the second surprise associated with Nanuqsaurus – as it comes from the north of Alaska. While the continents have moved over time, and the Cretaceous was warmer than today’s climate, Alaska has not moved much in the past 70m years, and it was certainly cold back then. So if Nanuqsaurus was from the frozen (or at least seasonally rather cold) north, why was it small? This would seem to run in opposition to Bergmann’s Rule, which while not universal, is pretty common and especially when Nanuqsaurus is from the part of the lineage that is otherwise full of giants.
The authors’ suggested explanation to this is that in this case the Island Rule has come up trumps. This part of Alaska was not an island then in terms of being surrounded by sea, but the area where the bones were recovered was cut off from most of the rest of the continent by a chain of mountains. Thus, just like an island, animals living in this region were “cut off” from the mainland and the region was both limited in size, and that far north, probably not replete with resources. Thus despite the latitude, the selective pressures on Nanuqsaurus may have been for smaller, not larger size, and hence the relative “pygmy” who was related to the giants.
Fiorillo AR, Tykoski RS. 2014. A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE 9 (3): e91287.
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Nanuqsaurus: A Surprisingly Small Tyrannosaur from Northern Alaska
The article discusses the discovery of a newly named dinosaur called Nanuqsaurus, which is a small tyrannosaur found in Northern Alaska. Despite being referred to as a dwarf or pygmy in some quarters, Nanuqsaurus is estimated to have been around 5 meters in total length. It is important to note that this estimation is based on very fragmentary remains.
Small Tyrannosaurs and Evolutionary Patterns
While the attention often focuses on giant tyrannosaurs like Tyrannosaurus, it is worth noting that there were smaller forms of tyrannosaurs in the past. Early forms such as Eotyrannus and Proceratosaurus were even smaller than Nanuqsaurus. In fact, there is a general evolutionary pattern in tyrannosaurs where later species tend to be larger than earlier ones. Nanuqsaurus stands out as an outlier in this pattern, as all of its nearest relatives, such as Tyrannosaurus and Tarbosaurus, are much larger in size. This makes Nanuqsaurus an interesting discovery.
The Island Rule and Body Size Evolution
The article mentions the Island Rule, which is a common evolutionary phenomenon associated with body size and how it varies under certain environmental conditions. Animals trapped on islands often undergo significant changes in size. According to the Island Rule, small animals tend to get larger while large forms tend to get smaller. This phenomenon has been observed in various species, including red deer on Scottish islands and pygmy elephants on Mediterranean islands. The article suggests that Nanuqsaurus being a small tyrannosaur from the north of Alaska goes against Bergmann's Rule, which states that animals closer to the poles tend to be larger. However, the authors propose that the Island Rule may explain the smaller size of Nanuqsaurus. Although the region where Nanuqsaurus was found was not an island surrounded by sea, it was cut off from most of the rest of the continent by a chain of mountains. This isolation may have limited the resources available, leading to selective pressures for smaller size.
In summary, the article discusses the discovery of Nanuqsaurus, a small tyrannosaur from Northern Alaska. It highlights the surprising nature of this finding, as Nanuqsaurus is smaller than its nearest relatives. The article also explores the evolutionary patterns in tyrannosaurs and the influence of the Island Rule on body size evolution.
FAQs
Bergmann's rule in Mesozoic dinosaurs and mammals. Bergmann's rule predicts that evolutionary increases in body size can be explained by positive shifts in absolute latitude and associated decreases in local climatic temperature along phylogenetic lineages.
What is the dinosaur with the smallest arms? ›
Carnotaurus sastrei
As a unique type of dinosaur in the Abelisauridae family, Carnotaurus sastrei had even smaller forearms than the T. rex. First found in Patagonia in 1985, dinosaurs in this family were known for their tiny horns extending above their eyes.
Why did so many dinosaurs have tiny arms? ›
Over more than a century, other proposed explanations for the short arms included waving for mate attraction or social signaling, serving as an anchor to allow T. rex to get up from the ground, holding down prey, stabbing enemies, and even pushing over a sleeping Triceratops at night. Think cow-tipping, Padian said.
What other dinosaurs have short arms? ›
rex is not the only enormous carnivore with small arms. Many theropods, a clade of bipedal carnivorous dinosaurs, have small arms attached to a massive body. Examples include Carnotaurus, whose name means meat-eating bull and whose arms look like vestigial stubs.
Do humans follow Bergmann's rule? ›
3 According to Bergmann's Rule, species of larger size are found in colder environments and species of smaller size are found in warmer regions. Anthropologists have found that many human populations tend to follow Bergmann's rule.
What is the Bergmann's rule in simple terms? ›
Bergmann's rule claims that that in cold climates, large body mass increases the ratio of volume-to-surface area and provides for maximum metabolic heat retention in mammals and birds. Conversely, in warmer temperatures, smaller body mass increases surface area relative to volume and allows for greater heat loss.
What is the small dinosaur that looks like a T. rex? ›
A new analysis of fossils believed to be juveniles of T. rex now shows they were adults of a small tyrannosaur, with narrower jaws, longer legs, and bigger arms than T. rex. The species, Nanotyrannus lancensis, was first named decades ago but later reinterpreted as a young T.
Why do autistic people sleep with dinosaur hands? ›
Why Might Neurodivergent People Sleep with Dinosaur Hands? The significance of sleeping with dinosaur hands extends beyond its visual portrayal. For many neurodivergent individuals, this sleep posture serves as a form of comfort and regulation.
What is the smallest dinosaur that ever existed? ›
The fossil skull of the new species, dubbed Oculudentavis, meaning "eye tooth bird," is just over half an inch long. The smallest dinosaur ever found – a bird-like creature weighing less than a tenth of an ounce – has been discovered inside a drop of amber, where it was preserved for 99 million years.
What is the biggest dinosaur that ever existed? ›
Patagotitan mayorum, the Titanosaur
Patagotitan mayorum may have been the world's largest terrestrial animal of all time, based on size estimates made after considering a haul of fossilized bones attributed to the species. The collection included a femur (thighbone) that measured 2.4 meters (8 feet) from end to end.
“Some people, particularly those with ADHD or sensory processing challenges, might crave deeper proprioceptive input,” says Keshri, “This could explain the T-rex arms, fidgeting, or even the comfort some find in weighted blankets or tight spaces.”
What is the dinosaur that looks like a T. rex with longer arms? ›
gigas had longer arms, study coauthor Juan Canale of the Ernesto Bachmann Paleontological Museum in Argentina tells CNN that they likely shrank as the animals developed larger, more powerful heads, with which they could have grabbed prey directly, leaving their arms unnecessary for hunting.
What newly discovered dinosaur had tiny arms like T. rex? ›
Rex. The 70-million-year-old meat-eater stalked South America during the Cretaceous, a new study says. Paleontologist Diego Pol analyzes a skull model of Koleken, a recently discovered carnivore from the late Cretaceous period.
What dinosaur has an armoured skull? ›
Pachycephalosaurus was an unusual-looking dinosaur. It stood on two legs, had a beak for cropping plants and had a large bony dome on its head surrounded by spikes and bumps. Some scientists think that the animal used its hard dome in head-butting contests, similar to the way modern-day rams use their horns.
Why did dinosaurs get so big? ›
Paleontologists don't know for certain, but perhaps a large body size protected them from most predators, helped to regulate internal body temperature, or let them reach new sources of food (some probably browsed treetops, as giraffes do today).
What animals follow Bergmann's rule? ›
This phenomenon was first described by German biologist Carl Bergmann in 1847 who noticed this geographical distribution pattern in many birds and mammals, for example, foxes, bears, and penguins. Generally larger-bodied animals, tend to conform more closely to Bergmann's Rule than do smaller-bodied animals.
What allowed dinosaurs to get so big? ›
Paleontologists don't know for certain, but perhaps a large body size protected them from most predators, helped to regulate internal body temperature, or let them reach new sources of food (some probably browsed treetops, as giraffes do today).
Does Cope's rule apply to dinosaurs? ›
Cope's rule is the tendency for body size to increase over time along a lineage. A set of 65 phylogenetically independent comparisons, between earlier and later genera, show that Cope's rule applied in dinosaurs: later genera were on average about 25% longer than the related earlier genera to which they were compared.
How can we figure out if dinosaurs were warm or cold blooded? ›
Researchers analyzed fossil specimens and measured the ratio of biochemical byproducts that resulted from breathing. They then discerned which dinosaurs were warm and cold-blooded, finding in the fossil record that warm-blooded dinosaurs would breathe more than cold-blooded.
