Fun Hesperornithoides Facts For Kids

Moumita Dutta
Nov 29, 2022 By Moumita Dutta
Originally Published on Dec 07, 2021
Edited by Luca Demetriou
Fact-checked by Kidadl Team
Hesperornithoides facts explore all details about the discovery of this bird-like dinosaur in this article.
Age: 3-18
Read time: 6.4 Min

Do you think birds evolved from dinosaurs? Any arguments against this theory were refuted when a new bird-like species was discovered in the Jimbo Quarry of the Morrison Formation in Wyoming, North America. Hesperornithoides (Hesperornithoides miessleri), as it was named by Scott Hartman, was the smallest and the only Troodontid member from the Jurassic. Its existence contradicted the 'temporal paradox', which suggested that the evolution of birds was not related to dinosaurs. Researchers found out this new species to have lived at the same time as Archaeopteryx and other primitive birds around 150 million years ago.

Hesperornithoides miessleri (a.k.a Lori) may have been bird-like in appearance, but being a genus in the Trootonid family tree, it was non-volant (ground-dwelling). The skeleton of the 150-year old dinosaur showed researchers how flying dinosaurs may have evolved. In natural history, this was a significant discovery. Learn other fantastic facts about this dinosaur, including its habitat, diet, taxonomic classification and physical description. These facts on the flying velociraptor can address the significant evolution of every dinosaur.

Want to know why this dinosaur was named Lori? Your search ends here! Expand your knowledge about other primitive dinosaurs like Heterodontosaurus and Metriorhynchus.

Hesperornithoides Interesting Facts

How do you pronounce 'Hesperornithoides'?

The name Hesperornithoides is pronounced 'hess-per-or-nith-oides'.

What type of dinosaur was a Hesperornithoides?

Hesperornithoides dinosaur is a type of troodontid and paravian theropod. Troodon is a group of sickle-clawed raptor-like dinosaurs such as the famous Velociraptor. Its type species is known as Hesperornithoides miessleri. Scott Hartman named and provided a detailed description of the species in 2019 in the Journal of Vertebrate Paleontology.

In which geological period did the Hesperornithoides roam the earth?

Hesperornithoides miessleri or this partial bird roamed the earth from the base of the Kimmeridgian to the top of the Tithonian stage of the Late Jurassic period. This geological period fell between 145-157 million years ago, right at the start of the Cretaceous period.

When did the Hesperornithoides become extinct?

Paleontologists estimate the Hesperornithoides miessleri became extinct by the beginning of the Tithonian stage (145 million years ago) of the Late Jurassic period.

Where did a Hesperornithoides live?

Hesperornithoides (approximately 150 million years old) was a ground-dwelling or terrestrial bird-like dinosaur.

What was a Hesperornithoides's habitat?

Researchers found the skeletal remains of this Troodontid member in the Morrison Formation (Late Jurassic) of Wyoming, USA. The Hesperornithoides habitat was characterized to be dry but with sufficient vegetation. The dry climate would not have supported any angiosperms, meaning flowers, trees, and other flora. The existing vegetation was riparian and mostly included coniferous trees such as tree ferns, ginkgos. The riparian habitat also likely had fish, lizards, turtles, pterosaurs, clams, and other mammaliaformes.

Who did a Hesperornithoides live with?

The living behavior of Hesperornithoides isn't clear due to the lack of enough data available. Thus, it cannot be confirmed whether or not they were solitary individuals or lived in groups.

How long did a Hesperornithoides live?

Paleontologists are yet to discover the average life expectancy of these Troodontids.

How did they reproduce?

These dinosaurs were oviparous, meaning they reproduced by laying eggs. This species group's reproduction details, such as mating and nesting style, have yet to be studied.

Hesperornithoides Fun Facts

What did a Hesperornithoides look like?

Hesperornithoides miessleri was a chicken-sized dinosaur possesing features of a bird. Since it is a Troodon family member, paleontologists were certain that the new species most likely had feathers. Its skeleton gave insight into how dinosaurs started flying like birds. The discovery of a preserved curved wishbone and semilunate carpal (wrist bone) were adaptations that helped early birds achieve flight. Lori's teeth and skull make it related to the Troodontidae group. While other body proportions make it part of the maniraptoran family tree.

Nicknamed Lori, Hesperornithoides translates to a western bird form.

How many bones did a Hesperornithoides have?

The discovered specimen consisted of a skull and partial skeleton. As mentioned by Scott Hartman in the Journal PeerJ, the holotype includes the rear skull, lower jaws, five neck vertebrae, back vertebrae, a rib, left shoulder girdle, twelve tail vertebrae, right humerus, left arm, chevrons, a piece of the thighbone, both legs without the right toe. The specimen is partially articulated, which makes it easy for the person to create a form by connecting the bones. Based on the study, the animal was perhaps an adult or subadult.

How did they communicate?

Paleontologists have not yet been successful in discerning how these 150 million old dinosaurs communicated with each other.

How big was a Hesperornithoides?

Lori was at least 35 in (89 cm) in length, about the size of a turkey or chicken. This made it the smallest-known species from the Jurassic Morrison Formation. This formation is known more for the big dinosaurs such as Stegosaurus, Apatosaurus, and the largest - Supersaurus. It was slightly smaller than Velociraptor, another Troodon group member, who was around 70.9 in (180 cm) long.

How fast could a Hesperornithoides move?

We've yet to discover the speed and agility of these dinosaurs as there is insufficient data available on this at present.

How much did a Hesperornithoides weigh?

The bodyweight of this dinosaur has not been described in Hartman et al (2019) analysis of the Hesperornithoides fossil.

What were the male and female names of the species?

The male and female members of these bird-like dinosaurs would be the same. They would be termed as adult Hesperornithoides miessleri.

What would you call a baby Hesperornithoides?

Baby Hesperornithoides are known as juveniles.

What did they eat?

The Hesperornithoides diet could either have been carnivorous or omnivorous. Researchers have come to this conclusion based on these dinosaurs being part of the Troodontids family. This analysis is as a carnivore, the primitive dinosaur may have preyed on juvenile dinosaurs of other theropods and ornithischians or other small animals like reptiles and insects.

How aggressive were they?

The behavioral characteristics of this 150 million years old bird-like dinosaur are yet to be examined. Being a predator, the animal was likely aggressive while hunting for prey.

Did you know...

The Hesperornithoides skeleton was found beside the remains of Supersaurus vivianae, the largest dinosaur from Wyoming.

WYDICE-DML-001 (specimen holotype) is available with The Wyoming Dinosaur Center, Inc.

The preserved specimen is placed along with the other early dinosaurs like Microraptor.

Who discovered Hesperornithoides and when?

A team from the Tate Museum of Casper College in Wyoming, United States found the skeletal remains of Lori in 2001. The specimen of the new species was found on the foot trail area of the Jimbo Quarry (Morrison Formation). It was discovered by accident when the team wanted to uncover the fossil of the 111-foot-long sauropod called Supersaurus. During the dig, a shovel damaged the snout of the Hesperornithoides fossil, unfortunately destroying part of it. Initially, the skeleton was misidentified as a pterosaur specimen. Later, Lori was correctly identified as a velociraptor-related dinosaur. The phylogenetic analysis of Lori was presented in 2005 in Journal PeerJ.

Finally, in 2019, Scott Hartman et al named and described the type species- Hesperornithoides miessleri. Hesperornithoides is derived from Greek where Hespris means western, ornis means bird and eides means form. The address Miessleri was given to honor the landowners who supported the search.

Fun fact! All dinosaurs except for the Hesperornithoides specimen were given nicknames that belonged to the landowner's children. Lori was named after Lori Hockemeyer, a volunteer at the search site.

Did the Hesperornithoides run or fly?

Hesperornithoides may have had a bird-like skeletal anatomy, but it stuck to the ground. However, its discovery gave great insight into the origin of avian flight. Whether Hesperornithoides is a direct ancestor of birds or it was just a group of bird-like dinosaurs that existed near the avian origin is still being debated. But this discovery shed light on the possibility that perhaps birds could have evolved from ground-dwelling animals.

Here at Kidadl, we have carefully created lots of interesting family-friendly dinosaur facts for everyone to discover! For more relatable content, check out these Zuniceratops facts, or Caviramus facts for kids.

You can even occupy yourself at home by coloring in one of our free printable dinosaur in Christmas hat coloring pages.

Main image by Scott Hartman​1, Mickey Mortimer2, William R. Wahl3, Dean R. Lomax4, Jessica Lippincott3, David M. Lovelace.

Second image by Vi Ko.

Hesperornithoides Facts

What Did They Prey On?

Small reptiles, mammals, insects

what Type of Animal were they?

Carnivore, omnivore

Average Litter Size?


What Did They Look Like?


How Much Did They Weigh?


Skin Type

Scales, feathers

How Long Were They?

35 in (89 cm)

How Tall Were They?










Scientific Name

Hesperornithoides miessleri

What Were Their Main Threats?


What Habitat Did They Live In?


Where Did They Live?

Wyoming, North America
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Written by Moumita Dutta

Bachelor of Arts specializing in Journalism and Mass Communication, Postgraduate Diploma in Sports Management

Moumita Dutta picture

Moumita DuttaBachelor of Arts specializing in Journalism and Mass Communication, Postgraduate Diploma in Sports Management

A content writer and editor with a passion for sports, Moumita has honed her skills in producing compelling match reports and stories about sporting heroes. She holds a degree in Journalism and Mass Communication from the Indian Institute of Social Welfare and Business Management, Calcutta University, alongside a postgraduate diploma in Sports Management.

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