25 Dinosaurs That Start With J

Discovered on every continent worldwide, dinosaurs first wandered the earth more than 200 million years ago (mya). Today, some still live among us! Did you know that scientists consider birds living dinosaurs? It’s true! Birds, such as the cassowary, closely resemble dinosaurs of the past. The classification of birds as dinosaurs is based on the scientific study of evolution and relationships between groups of organisms (phylogeny). However, we’re only considering non-bird dinosaurs today. Read on to learn about 25 incredible dinosaurs that start with J. Before that, let’s take a look at how dinosaur discoveries get their names!

Naming a Dinosaur

Interestingly, where dinosaurs roamed often determines their name. Other dinosaurs take their name from the person who discovered them. Sometimes, the name describes the dinosaur’s features or looks. These names are almost always of Latin origin.

Dinosaur names, just like all scientific names, conform to a special set of rules called binomial nomenclature. In simple terms, this means “two names.” These rules apply to all scientific names for all living or extinct organisms. The first name (genus or generic name) is always capitalized. The second name (or specific name) is unique to the species, it’s never capitalized. Both words must always be italicized. For dinosaurs, genera (plural of genus) typically combine a root word (like Cerat) that describes their body with –sauros or -saurus (lizard).

An example of this is the Ceratosaurus, a genus of dinosaurs that walked on two feet (theropod). Cerat means “horned”, so Ceratosaurus means “horned lizard.” The large horns on top of the snout and over the eyes are one of the common features of the three species within this genus. Sometimes paleontologists find parts of dinosaur skeletons that are only possible to identify as belonging to a particular genus, rather than a specific species. This is why they often refer to the genus versus species, as we’ll learn below.

Genus vs. Species

Regarding how paleontologists choose dinosaur names, AZ Animals spoke with Dr. David E Fastovsky. Dr. Fastovsky is a paleontologist and Professor Emeritus in the Department of Geosciences at the University of Rhode Island. We asked, “How many dinosaur species can you think of that start with the letter J?”

He responded with a very detailed answer regarding genus versus species:

“This is not something that most dinosaur paleontologists would have at the top of their heads.  But it is easy enough to Google this question and a nice answer can be found here. Now, it is important that you understand that paleontologists don’t usually talk about species of non-avian dinosaurs; because species-level differences are very uncertain with only bones (or parts of bones) preserved, we tend to think more in terms of genera, as in Tyrannosaurus. 

For example, although there has been a lot of discussion, there is no widespread agreement that more than one species of Tyrannosaurus is known:  T. rex. In the case of Triceratops, there are two species known:  T. horridus and T. prorsus. These require complete specimens to be distinguished, which means that most finds can only be identified as Triceratops (the genus) and not species.  This applies to virtually all non-avian dinosaurs.  So, the list that I have given you to look at is given at the generic level, at which dinosaur identifications can be done definitively, and does not include species.”

Genera names are often reduced to their first letter while specific names are always written out. Now that we know more about dinosaur names, let’s discover 25 dinosaurs that start with J!

#1 Jaculinykus yaruui: The Speedy, Clawed Dinosaur That Starts with J

An exciting genus of dinosaurs that starts with J, Jaculinykus, consists of only one species. Jaculinykus yaruui stands out among dinosaurs because of the nearly complete skeleton found in Mongolia in 2023. Its name combines several elements: Jaculus (a small mythological Greek dragon), “onykus” from the Greek language meaning “claw”, and “yaruui,” which is the Mongolian word for “speedy” or “hasty.” Altogether, the name means “speedy clawed dragon.” Available artist renderings certainly portray the dinosaur as such. This small dinosaur was likely an ancestor to our modern-day birds. They lived about 72-71 mya.

#2 Jainosaurus septentrionalis

Our next dinosaur with a J-name was a massive species. Jainosaurus septentrionalis, lived roughly 68 mya. Measuring 59 feet long and weighing over 33,000 pounds, these colossal creatures ate only plants (herbivores). Originally named Antarctosaurus septentrionalis when discovered between 1871 and 1872, the name changed in 1995. The name change honored Sohan Lal Jain, the paleontologist who worked on the skull and published a study about it. Jainosaurus means “Jain’s lizard.”

#3 Jakapil kaniukura

Our first small dinosaur whose name starts with J was the Jakapil kaniukura. It only measured around 5 feet long and probably weighed an estimated 10-15 pounds. This small herbivore probably chewed tough plant materials for food. Scientists determined this by looking at the shape of their jaws and teeth. Due to the armor-like plates along its body, this dinosaur belongs to the same clade (or group of organisms thought to descend from a common ancestor) as the more commonly known Stegosaurus and Ankylosaurs. Uncovered between 2014 and 2020 in Argentina, it likely lived between 97 and 94 mya.

#4 Jaklapallisaurus asymmetrica: Oldest Dinosaur That Start With J

Named by a group of paleontologists in 2011, the Jaklapallisaurus asymmetrica discovery happened near the Indian village of Jaklapalli. The specific name comes from the asymmetrical shape of one of the ankle bones found that identified this species. It was one of two species in the genus. These dinosaurs were omnivores (eating both plants and meat). Similar to Velociraptors, they stood on their two rear legs and had shorter front limbs. A major difference was their long necks. That’s why they belong to the clade Sauropodomorpha with other long-necked dinosaurs like Brontosaurus. Further classified into Unaysauridae, J. asymmetrica were the oldest of the dinosaurs that start with J!

#5 Janenschia robusta: Largest Dinosaur That Start With J

Janenschia robusta was yet another J-name dinosaur species and another sauropod. Like others in the clade, they ate only plants (making them herbivores). Paleontologists incorrectly designated the first fossils, excavated in 1907, as belonging to Gigantosaurus. However, that name already belonged to another genus. It wasn’t until 1991 after many changes and debates that the creature gained its proper name. Werner Janensch, a paleontologist who studied animals of the Tendaguru Formation in Tanzania where the fossils surfaced became the namesake of this creature. Then it transferred to the family Tintanosauridae, making it the oldest member of the group (203 mya). Weight estimates for this dinosaur range from 22,000 to 66,000 pounds making it the largest of all the dinosaurs that start with J

#6 Jaxartosaurus aralensis: Kazakhstan’s Dinosaur That Starts With J

Jaxartosaurus aralensis, uncovered in Kazakhstan, was first described in 1937. It belongs to the Hadrosauridae family, a group of dinosaurs with large crests on top of their skulls. Most paleontologists agree this dinosaur that starts with J ate low-lying plants. The purpose of the crest is debatable. Perhaps it was for visual or audible communication. This species is closely related to the well-known Paralophosaurus popularized by the Jurrasic Park franchise. They lived about 94-84 mya.

#7 Jeholosaurus shangyuanensis

This J-name dinosaur got its generic name from Jehol, a historical place in Northeast China. This was a small herbivore (or omnivore, undecided) with a very long tail. The only remains discovered so far came from young, subadult specimens. Therefore, their true adult size remains a mystery. In the name Jeholosaurus shangyuanensis, the specific name refers to the area the fossils came from (Shangyuan). This species roamed Earth roughly 125-122 mya.

#8 Jeyawati rugoculus

The generic name, Jeyawati, means “grinding mouth.” The specific name, rugoculus, means “wrinkle eye.” It refers to the wrinkled ridges of the eye sockets. No one knows much about this J-name dinosaur except they lived around 94-89 mya. Some paleontologists believe the wrinkles may have been to support blood vessels in the area to allow some sort of visual display. However, the available skeletal remains (found in New Mexico, U.S.) don’t provide enough information on this feature. J. rugoculus belongs to Hadrosauridae along with Jaxartosaurus aralensis.

#9 Jianchangosaurus yixianensis: Feathered Dinosaur That Starts With J

This dinosaur that starts with J was different from those we’ve already covered due to the presence of feather imprints along with its discovered skeletal remains. Found in the Jianchang province in China, its specific name combines the name of the formation where it became known (Yixian) and the suffix -ensis meaning “originating in.” Standing 3.3 feet tall and measuring just over 6.5 feet long, this dinosaur probably weighed as much as a medium-sized dog (approximately 45 pounds).

#10 Jiangjunosaurus junggarensis

Jiangjunosaurus junggarensis is a J-name dinosaur belonging to the same group as Jakapil kaniukura (Stegosauridae). Covered in strong vertical plates to protect it from predators, this dinosaur also had spikes on the end of its tail. At nearly 20 feet long and over 5,500 pounds, these creatures possessed the ability to protect their young and themselves. Discovered near the abandoned town of Jiangjunmiao, China, in the Junggar Basin, J. junggarensis combines their names to create its scientific one. These impressive creatures lived roughly 125-120 mya.

#11 Jiangshanosaurus lixianensis

Discovered in 1977, Jiangshanosaurus lixianensis hails from China, as well. Its name, which relates to where it originated (a common trait in dinosaurs discovered in China), came about in 2001. A paleontologist team located the massive skeletons in the Jinhua formation of Lixian Village. The village is a part of Jiangshan county in eastern China. This dinosaur belongs to the clade Somphospondyli. Scientists found fossils of dinosaurs in this clade on every continent in the world! This dinosaur that starts with J existed some 92-88 mya.

#12 Jiangxisaurus ganzhouensis

Discovered in the Jiangxi Province of southern China near Ganzhou City, Jiangxisaurus ganzhouensis was most likely an herbivore. The significance of this dinosaur comes into play when looking at the paleogeographical distribution of oviraptorids in the area. That is, it helps scientists learn more about its cousins that also lived in the same place. Paleogeography is the study of historical geography (the study of physical landscapes). The Oviraptoridae family consists of more than 20 subgroups. This is the only dinosaur in the family that starts with J.

#13 Jiangxititan ganzhouensis

Found in the very same region as Jiangxisaurus ganzhouensis, this ginormous J-name dinosaur has a very similar name. In fact, the only difference is the suffix on the genus, -titan. This suffix refers to the titans in Greek mythology and designates this species as absolutely massive. Jiangxititan ganzhouensis towered over other dinosaurs from the same area. One of the bones found measured more than 2 feet across! However, this species looks small compared to the largest dinosaur that ever existed.

#14 Jianianhualong tengi

The Jianianhua dragon (Jianianhualong tengi), named in 2017, belongs to the Troodontidae family. Some researchers believe this family contained the smartest dinosaur that ever lived! Though it’s not a dinosaur that starts with J, the Troodon formosus is closely related to this Chinese discovery. J. tengi was a small, feathered dinosaur. Though incapable of flight, the feathers likely served to help balance the creature and reduce drag when hunting. This species is similar to J. yaruui found in Mongolia. Living approximately 125-122 mya, it was just over 3.5 feet long and weighed a mere 5 pounds.

#15 Jinbeisaurus wangi

 Jinbeisaurus wangi (meaning “northern Shanxi Province lizard”) is another J-name dinosaur from China that lived around 99-71 mya. No other Theropoda dinosaur comes from this area so far. Surprisingly, this dinosaur shares the clade designation with the famous T. rex, among others of Tyrannosauroidea (some 20 or more genera). Though much smaller than its cousin at only an estimated 19 feet long, it also hunted and consumed other dinosaurs (meaning it was a carnivore).

#16 Jinfengopteryx elegans: Another Tiny Dinosaur That Starts With J

No surprises here, Jinfengopteryx elegans also comes from China. Named after the Jinfeng (or Jui feng), the golden phoenix and queen of birds in Chinese folklore, it lived between 127 and 121 mya. Discovered as a single specimen with extensively well-preserved feather impressions, this tiny, bird-like dinosaur pre-dates the first bird (Archaeopteryx) by 30 million years or so. Measuring about 1.8 feet long and about half as tall, it’s still not the smallest of all of our dinosaurs that start with J. Michael Scott Earle’s book series, Tamer: King of Dinosaurs, featured this species as one of the character’s pets.

#17 Jingshanosaurus xinwaensis

Continuing with China’s host of dinosaurs that start with J, we have Jingshanosaurus xinwaensis. This relatively small Sauropodomorpha clade member grew to only approximately 16 feet long and weighed up to roughly 9,400 pounds. It’s further classified as a prosauropod. This group predated sauropods and often walked on two feet, whereas their larger cousins did not. This discovery remains one of the few finds of a complete dinosaur skeleton and skull in history. Despite this, finding quality photographs of the fossils remains difficult. It was one of the last prosauropods to exist on Earth, living around 201-196 mya.

#18 Jintasaurus meniscus

Jintasaurus meniscus became formally described in 2009 after its discovery in Jinta County, China. Paleontologists know very little about this species, having found only a few fragments of the skull. From the bones they examined, they determined their unique way of chewing. It belongs to the Hadrosauridae family along with J. aralensis and J. rugoculus. A skeletal replica on display in one Chinese museum shows what it may have looked like.

#19 Jinyunpelta sinensis

As you can probably guess by now, Jinyunpelta sinensis owes its name to Jinyun County, China. The ankylosaur was first discovered by a farmer at a construction site. Over the next six years, paleontologists unearth a total of five skeletons in the area. Two of them belonged to the new species. Named in 2018, its specific name comes from the Greek word meaning “small shield.” The specific name refers to its origins in China. This species had a club tail and armor-like plates along its back and sides. This species lived 112-99 mya, give or take.

#20 Jinzhousaurus yangi

Another Chinese hadrosaurus, Jinzhousaurus yangi became known through the discovery of a nearly complete skeleton. It measured around 23 feet long with its skull about 1.6 feet long. Closely related to the Iguanadon, its family (Iguanodontidae) consists of six genera. This herbivore lived approximately 127-121 mya. Many paleontologists believe it regularly switched between quadrupedal (four-legged) and bipedal (two-legged) walking. It ate tough plants by chewing them, similar to J. kaniukura.

#21 Jiutaisaurus xidiensis

Closing out the 14 different dinosaurs that start with J discovered in China, we have Jiutaisaurus xidiensis. This sauropod found in Jilin, China lived between the period of 125-93 mya. Another of the titanosaurs, it gained its name in 2006. Its generic name comes from its location of discovery. Together with the specific name, it means “Jilin’s nine-tipped lizard.” Its description was based on the 18 vertebrae uncovered in the find. J. xidiensis belongs to the clade Macronaria along with 24 other genera.

#22 Jobaria tiguidensis

Moving on from China to Niger, Africa, Jobaria tiguidensis was discovered in 1997 and named in 1999. It was a primitive sauropod weighing over 49,300 pounds! At 60 feet long, they could stand on their rear legs to reach leaves high up in the trees. J. tiguidensis is the second largest of all the dinosaurs that start with J. Scientists say their body composition was akin to elephants, with most of their weight supported by the hind limbs. It was named after a mythical beast (Jobar) and the cliff of Tiguidi, where it was discovered. Originally, researchers estimated this species lived around 132 mya. However, more recent studies showed they existed between 167 and 161 mya.

#23 Judiceratops tigris

The only dinosaur discovered so far that starts with J that belonged to the Ceratopsoidea clade was Judiceratops tigris. It belongs to the subfamily Chasmosaurinae along with the famous Triceratops. Though J. tigris takes the title of the oldest known species within the subfamily (living 78-77 mya). Collected in Montana, U.S., it became the second of the subfamily found in the area. The first was Medusaceratops. Paleontologists found four skull fragments of J. tigris in the Judith River Formation and named it in 2013. Much of what they determined about this dinosaur came from the scale patterns found with the bone fragments.

#24 Juratyrant langhami: Tyrannosaurus Dinosaur That Starts With J

Another dinosaur that starts with J and was a member of the Tyrannosauroidea family was Juratyrant langhami. Estimated to grow anywhere from 16 to 20 feet long and weigh 660-1675 pounds, this smaller Tyrranosaur still took down large prey. Its formal description came in 1984, followed by its name in 2008. The specific name honors Peter Langham, who unearthed it. The generic name means “Jurassic tyrant,” referring to the period in which it lived (150-145 mya). This fearsome carnivore stood just taller than the average human and hunted other dinosaurs for food. Where did it hunt? England!

#25 Juravenator starki: Smallest Dinosaur That Starts With J

Last, but not least comes the smallest of all dinosaurs that start with J, Juravenator starki. Measuring just over 2 feet long and standing only just above the ankle of the average human man, this tiny carnivore has been the center of many debates in the world of paleontology. Some say it is a hatchling of the Megalosauroidea clade (along with the infamous Spinosaurus), while others maintain it as a separate genus. Found in Germany, it roamed the earth around 152-151 mya.

Summary of Dinosaurs That Start With J

The following list includes all dinosaurs that start with J discovered as of December 2023. Temporal range refers to the period a species exists within. Of course, carbon dating used for determining temporal ranges remains only an estimate.

The photo featured at the top of this post is © kitty kahotong, Vanzyst/ via Canva.com