Dilong Paradoxus. (DIE-long) Early Tyrannosaurid Found in the Middle Jurassic to the Early Cretaceous. Claudia Montilla

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1 Dilong Paradoxus (DIE-long) Early Tyrannosaurid Found in the Middle Jurassic to the Early Cretaceous Claudia Montilla William Parker BRY Trilobites to T-Rex

2 Dilong Paradoxus 2 Abstract Dilong paradoxus, discovered in the Chinese province known as Liaoning. Dilong paradoxus falls into the Tyrannosauridae family and is thought to be a distant relative of the Tyrannosaurus rex. Dilong was feathered, small, and maintained characteristics of both the tyrannosaurids and earlier coelurosaurs spurring several different subjects of debate over the Dilong s classification. INTRODUCTION Dilong paradoxus was named from a specimen found in north eastern China that helped confirm the suspicion that dinosaurs had feathers, and that dinosaurs were an avian ancestor. It was discovered in 2004 by Dr. Xu Xing (Murray 2013). The location in which the specimen was found showed that eastern Asia was not completely isolated during this time period. Along with being an ancestor to the modern chicken, Dilong is considered one of the first members of the tyrannosauridae superfamily- meaning it was an ancestor to the common favorite household dinosaur, Tyrannosaurus rex; this family also includes the majority of the tyrannosaur lineage coming from Asia and North America. The most interesting fact about these little dinosaurs is their traits that have characteristics from older coelurosaurs and characteristics that would appear in later tyrannosauridae (Murray 2013). This shows that Dilong represented a huge leap in evolution, acting as a bridge between eras. Not only was the individual specimen a major scientific find, but the entire Jehol Group 1 find provided major insight into the Middle Jurassic and Early Cretaceous periods (Xu, 2006). If anything, the biggest discovery involving the Jehol Group was its very existence, considering it was a previously held notion that this area of the 1 The Jehol Group was an excavation site found in north eastern China where many new specimens were found in excellent condition.

3 Dilong Paradoxus 3 world was isolated during the time period described. Dilong is also notable for having four extremely well preserved specimens found in Liaoning, especially considering the site was previously raided, with some specimens being stolen. DISCUSSION Figure 1 Artist reconstruction of Dilong paradoxus (Xu 2004) Dilong paradoxus, a theropod classified in tyrannosauridae, was discovered in 2004, along with several other species. The origin of the name Dilong comes from the fabled emperor dragons that are prevalent in the local culture of that area (Xu, 2004). It was unearthed in a revolutionary find, which led to the long debated did non-avian dinosaurs have feathers? question being answered with convincing evidence during a period where the study was becoming more popular (among specimens that were not categorized under dromaesauridae 2 ). Dilong was on the smaller end of the tyrannosaurid dinosaur spectrum, compared to specimens such as the Tyrannosaurus rex, but it was one of the larger predators at the time of its speculated evolutionary debut. Dilong is considered, currently, one of the basal Tyrannosaurs (there has been controversy about this due to the nature of the specimen - meaning that it has traits that can 2 Biological family including raptors.

4 Dilong Paradoxus 4 be considered to belong to more than one family). It is thought that early tyrannosaurids, like Dilong, eventually evolved into the tyranno-giants such as Tyrannosaurus rex (Xu, 2006). Dilong and its companions, also, were found in an area that was not thought to have any life in it during that time; North Eastern China was considered to be completely isolated during the Middle Jurassic through the Cretaceous, approximately 130 million years ago) (Murray 2013). The specimens that were found were extremely well preserved, enough so that the soft tissue of some of the specimens was preserved along with the patterns of what are thought to be protofeathers. The reason these specimens were so well preserved there was that the ancient lake deposits surrounded by consistent volcanic activity (specifically the Yixian formation) were made up of a very fine-grained mud combined with ash and lava flows that captured the detail of the skins, feathers, and finer details of the animals that fell into it. The ancient habitat of Dilong seems to have consisted of mostly wetland and swamps. This kind of sediment is excellent for preservation of detailed material, hence the quality of the specimens found in Liaoning. This area housed a great variety of species, Mellissa Murray describes Liaoning like a 'natural laboratory', like the Galapagos Islands, with high biodiversity. (Murray 2013). Bones and other specimens that were determined to belong to Dilong were found in north eastern China in the Liaoning province. The strata that Dilong was discovered among is known, formally, as the Jehol Group of western Liaoning, where 25 new species and 21 new genera of non-avian dinosaurs were found (this is excluding specimens that have been removed illegally, these may have affected the true specimens found and the interpretation of the data) (Xu, 2006). The four specimens that were found included three found in the Luijatun bed and one found in the Jianshangou beds. The specimen found in the Jianshangou beds is known for the

5 Dilong Paradoxus 5 preservation of the filamentous integumentary structures close to the mandible along the caudal vertebrae. Dilong 3 was one of the earlier dinosaurs and the first tyrannosaurid to have feathers. This suggests that it was a distant relative- possibly an ancestor- to the modern bird. This concept is still highly debated because the theory that dinosaurs were ancestors to birds is not definitively proven. As Nicholas R. Geist 4 attests in his review of Feathered Dinosaur: The Origin of Birds by John Long and Peter Schouten 5, The notion that birds are the direct descendants of theropod dinosaurs has gained an increasingly powerful foothold within the paleontological community, and while an evolutionary connection is clear, the exact nature of that relationship remains a work in progress. (Geist 2009). Although it did have feathers, Dilong would not have had the ability to fly at this point, as it did not have wings. The feathers were all over Dilong s body and (conceptually) fanned off of the tail (Xu, 2004). The feathers were short and fuzzy, like downy feathers on a modern bird. Dilong did not have what would be called true feathers like birds. Short protofeathers are an earlier adaptation to feathers that would actually support flight. There is controversy surrounding whether the marks present on the specimens are actually from feathers or from some other extraneous fauna/flora. Nicholas R Geist also mentions in his review, Having examined first-hand a number of the specimens described in the book, I remain on the fence. While some of the fossils inarguably have feathers (e.g., Confuciusornis, Microraptor, Caudipteryx), others are open to interpretation. The simple filamentous 3 The dinosaur is more commonly known as simply Dilong rather than by the long Latin name, Dilong paradoxus. Di meaning emperor, long meaning dragon, and paradoxus referring to the protofeathers (Murray, 2013). 4 Nicholas R. Geist is an associate professor of Biology at Sonoma State University with a Ph.D. of zoology from Oregon State University. 5 John Long is a notable paleontologist and has published at least 24 books within the scientific community. Peter Schouten is an esteemed natural history artist.

6 Dilong Paradoxus 6 integumentary fibers preserved on some of the Chinese fossils (e.g., Sinosauropteryx, a meterlong compsognathid, and Dilong paradoxus, a primitive tyrannosaurid) bear little resemblance to feathers. (Geist 2009). Geist goes on further to describe that the filaments preserved in the specimens do not have the feather structure that is consistent with other specimens found that are considered to have had feathers. Regardless of the controversy, it is thought that these protofeathers were used for insulation; according to Dr. Thomas R. Holtz 6 A little animal loses heat a lot faster than a big animal it would help if you had a body covering that trapped heat inside the body so it may be that little dinosaurs with an active lifestyle evolved protofeathers so that they could keep from losing too much heat. (Holtz 2007). This functionality could also have been used for sexual display or for insulating eggs- the animal would have lain across the nest to keep the eggs warm, like a modern bird, until they hatched. Dilong paradoxus was a carnivore, evidenced by the sharpness and lack of variety in teeth. Their teeth were shaped like Ds, used for scraping and nipping at their prey (Holtz 2007). Another form of evidence for this lifestyle includes the presence of fused nasal passages. These specialized nasal passages make the bite of an animal exponentially stronger and provides the ability to do more damage per bite without inflicting damage to the jaw or skull of Dilong; or it can be used for actual feeding and scraping meat off the bone, allowing Dilong to apply more force to a carcass without splintering and wearing at its own skull (University of Alberta). Also, this empowered bite could have been used to crush bone and other cartilage of prey. This 6 Dr. Thomas R. Holtz is a senior lecturer at The University of Maryland s department of Geology and vertebrae paleontologist, he is known for his work with the BBC and his extensive list of published material.

7 Dilong Paradoxus 7 adaptation is a tyrannosaurid staple and would serve as a huge advantage in the future of the species. Figure 2 Skull and teeth structures of Dilong (Xu, 2004) The only primary surrounding Dilong s classification is that Dilong has characteristics from both tyrannosauridae and dromaesauridae (which encompasses raptors). In a case study regarding tyrannosaurid and other basal species interrelations carried out by A.O. Averianov1, S.A. Krasnoludzkii2 and S.V. Ivantsov3 7 The newly described tyrannosaurids Dilong lie[s] outside Tyrannosauridae (Averianoy, Kransolutskii, Ivantsoy 2010). However, it is worth noting that Averianoy et al do not go about explaining their reasoning for their dissent, thereby, in my eyes, making their argument seem less valid. This controversy is based on how both Dilong and some members of dromaesauridae have extremely birdlike characteristics (i.e. feathers). Both families also coexisted during the same historical period. Dilong also maintained some traits more typical of early coelurosaurian dinosaurs such as longer arms, three fingers, and 7 1 A.O. Averianoy is a professor at the Zoological Institute of the Russian Academy of Sciences in St. Petersburg, Russia. 2 S.A. Kransolutskii works for the Sharkypovo Regional Museum in Russia. 3 S.V. Ivantsov works for the Department of Paleontology and Historical Geography at Tomsk State University in Tomsk, Russia.

8 Dilong Paradoxus 8 its size. Another unique characteristic that Dilong possessed was fused nasal passages. These fused nasal passages connect Dilong to the tyrannosaurid family, as it is unique to the family (University of Alberta). Despite these similarities and off-putting traits, there still remain characteristics that keep Dilong within the tyrannosaurid family. These include the fused nasal passages. This is a vaguely new idea and is not heavily confirmed as far as my research has shown. It has only briefly been mentioned. Thus Dilong s status as a tyrannosaurid is not threatened. Table 1 Dilong's relationship to Coelurosaurian family (Roach, 2004) Table 2 Phylogeny and origin of traits among families during Cretaceous (Headen 2012).

9 Dilong Paradoxus 9 Dilong s diet was thought to be a hunter of small prey such as lizards, mammals and other small vertebrates (Murray 2013). They did not yet have the specialized bone crunching teeth that Tyrannosaurus rex and later tyrannosaurids had but the fused nasal passages made up for the lack in tooth strength. Dilong hunted by snatching up prey with its arms and nipping meat off. The holotype was found to be about 5 feet long (1.6 to 1.8 meters in length) and weighed up to 25 pounds. This holotype might be slightly off, though, because it is speculated that the measurements are that of a juvenile. They are thought to be shorter than humans even in adulthood. Figure 3 Size comparison between Dilong paradoxus and a human (Conty 2010) Dilong was bipedal with two long legs and two long arms 8. According to written sources and studies the consensus seems to be that Dilong had longer arms in proportion to its body to grasp at and grab at prey (Murray 2013). However, these arms would not have been long enough to suggest that Dilong spent a good amount of its time as quadrupedal. These features contribute to the idea that Dilong was active and warm-blooded, like a bird, rather than sedentary and cold- 8 Figure 1 shows Dilong with extremely short arms. In artist portrayals of Dilong the arm length varies

10 Dilong Paradoxus 10 blooded (Murray 2013). Each arm had three long fingers. These arms are long compared to that of other tyrannosaurids; because it was still at the cusp of a new species and and ancient one. The arms were notably shorter than the legs. The legs are proportionately shorter than that of an ideal tyrannosaurid compared to the arms, suggesting it was on the slower side (Murray 2013). CONCLUSION Dilong paradoxus was a revolutionary find in the universe of paleontology. It was important not only for the feathers it had, but for the location in which it was found. Without the excavation efforts in Liaoning, the area would still be considered isolated during the Cretaceous period. To reiterate, four specimens of Dilong were found in two different places, one in the Jianshangou beds and three in the Luijatun beds. It may have had protofeathers and specialized features unique to the tyrannosaurid lineage. It was definitely considered to be an early contributor to the tyrannosauridae lineage. Features like fused nasal passageways, and the other aforementioned traits tie Dilong to its classification well enough to merit the classification but it does, unequivocally, have traits that differentiate it from the classic tyrannosaurid. The Jehol Group in Liaoning provides a wealth of knowledge about how Dilong lived and the discovery of Dilong provides a wealth of knowledge of how many later species came to exist. REFERENCES A.O. Averianov, S.A. Krasnoludzkii and S.V. Ivantsov (2010) A New Basal Coelurosaur Dinosauria: Theropoda) From the Middle Jurassic of Siberia Retrieved from Conty. "Dilong Paradoxus." (2010). Wikipedia. Wikimedia Foundation, n.d. Web. 25 Nov

11 Dilong Paradoxus 11 Holtz R, Thomas (2007). Print. Dinosaurs- the most Complete, Up-To-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House Children s Books. Headden A, Jaime (2012). On the Structure of Fossil Feathers. Retrieved from: Murray, Mellissa (2013). Dilong paradoxus. Retrieved from Nicholas R. Geist (2009) Book Reviews Feathered Dinosaurs: The Origin of Birds. John Long and Peter Schouten. Retrieved from Roach, J, (2004). New Dinosaur Discovered: T. Rex Cousin Had Feathers. National Geographic News. Retrieved from: University of Alberta. "Fused Nasal Bones Helped Tyrannosaurids Dismember Prey." ScienceDaily. Retrieved from Xing, Xu; Norell A, Mark (12 Sept. 2006). Non-Avian dinosaur fossils from the Lower Cretaceous Jehol Group of Western Lianing, China. Retrieved from B70A D7AC14160.f04t03 Xing, Xu (2004). Dilong paradoxus. Retrieved from Xing Xu, Mark A. Norell, Xuewen Kuang, Xiaolin Wang, Qi Zhao1 & Chengkai Jia (2004). Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids." Retrieved from: