Phaedrolosaurus, meaning “elated lizard”, was a species of dromaeosaurid raptor dinosaur which lived in western China during the early Cretaceous Period approximately 130-120 million years ago.
In 1963, a team of local geologists were exploring an area near the town of Wuerhu, located within the Junggar (also spelled Jung-Gar, Dsungar, or Zhunga’er) Basin of northern Uyghurstan. Within this area are the rocks of the Lian-Mu-Qin (also spelled Lianmugin) Formation, which is the uppermost formation of the Tugulu Group (Xing et al. 2020, page 76). Here, they stumbled upon fossils belonging to several dinosaur species. The type locality where the fossils were found is classified as “IVPP site 64043”, which is regarded as being deposited by a river delta on the shore of a lake (Xing et al. 2020, page 76). The entirety of the Lian-Mu-Qin Formation’s strata within this area measures 405 meters thick, and the fossil horizon found within the locality designated “IVPP site 64043” was uncovered within the lower section of the formation (Xing et al. 2021, e11476). In 1964, paleontologists visited the site, excavated the fossils, and brought them to the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) for study (Rauhut and Xu 2005, page 107).
The exact dating of the Lian-Mu-Qin Formation as a whole and the dating of the exact locality where the fossils have been found are confusing, because different research papers give different dates. A paper from 1991 stated that the formation spanned the entirety of the Early Cretaceous (Chen et al. 1991, page 4,068), which would date the entire formation to 144-100 million years ago (MYA). A 2004 paper stated that the formation spanned the Aptian (maybe) and Albian Stages of the middle Cretaceous (Maisch et al. 2004, page 625), which would tentatively date the formation to 121-100 MYA. A 2008 paper stated that the Lian-Mu-Qin Formation dated to the Barremian Stage, 125-121 MYA (Yang et al. 2008, pages 345-363). A 2010 paper said that the rocks of the Lian-Mu-Qin Formation spanned from possibly the Valanginian Stage to the Albian Stage (Brusatte et al. 2010, page 282), provisionally dating it 139-100 MYA. This assessment was repeated two years later (Brusatte et al. 2012, pages 65-66, 70). A 2019 paper stated that the Lian-Mu-Qin Formation dated from the lower Aptian Stage to the middle-to-upper Albian Stage (Xi et al. 2019, pages 256-286), approximately 120-105 MYA. As you can see, there isn’t much consensus aside from the fact that everybody agrees that the Lian-Mu-Qin Formation dates to sometime during the early Cretaceous Period.
Two different date spans are given for the specific locality “IVPP site 64043” within online sources. One website states that it’s dated from the late Aptian to the late Albian Stages of the middle of the Cretaceous Period (dates aren’t given here, but this would date it from about 115-100 MYA), while another is it says that it’s dated from 122.5-99.7 MYA, which dates the rocks from the late Barremian to the very end of the Albian Stages (“Wuerho, IVPP site 64043 (Cretaceous of China)”; “Kelmayisaurus petrolicus Dong 1973 (allosauroid)”). By looking at the most common dates given in the various sources, I propose that the rocks of the Lian-Mu-Qin Formation as a whole date from the early Hauterivian Stage to the end of the Albian Stage, circa 130-100 MYA. Moreover, it was stated that the specific locality was situated within the lower 175 meters of this formation’s strata, less than half of the formation’s total depth, and should therefore date to the lower end of that timespan. Unfortunately, a more precise stratigraphic description wasn’t given, so we have no idea exactly how far down this fossil layer is situated. It must be noted that fossils of the stegosaur Wuerhosaurus homheni were also found in this locality. Numerous popular media books from the 1990s and 2000s state that Wuerhosaurus lived 135-120 MYA, which is within the lower end of the time span given above, and which serve as plausible dates for the fossil locality. Therefore, I believe that the dates for the locality “IVPP site 64043” should be tentatively and cautiously revised to 130-120 MYA. Rigorous dating methods need to be employed by people who are far more skilled in these matters than myself in order to determine whether this is true.
One of the fossils which was recovered at the locality was a single tooth (collection ID code: IVPP V 4024-1). It was similar in shape to the teeth of Deinonychus, but it was shorter, thicker, and more robustly built, indicating it had a more strongly-built skull. In 1973, this tooth was ascribed the name Phaedrolosaurus, “the elated lizard”, in reference to its supposed active energetic lifestyle (Dong 1973, pages 46-47).
If Phaedrolosaurus was related to Deinonychus, then it’s possible that the two animals measured about the same size, so Phaedrolosaurus possibly measured 10 feet long.
In 1990, British paleontologist David Norman stated that Phaedrolosaurus was a nomen dubium but didn’t provide further information (Norman 1990). In 2005, it was noted that while Dong gave a general description of the tooth, he did not list any characters which distinguished this tooth from any other theropod dinosaur teeth. Therefore, the article argued, Phaedrolosaurus ought to be regarded as a nomen dubium (Rauhut and Xu 2005, pages 107, 112). At present, that single tooth is the only known fossil of Phaedrolosaurus. More excavations will need to be carried out in the area to see if we can find even more remains of this intriguing creature.
Phaedrolosaurus shared its early Cretaceous environment with the stegosaur Wuerhosaurus, the alvarezsaur Tugulusaurus (originally believed to be an ornithomimid), the carcharodontosaur Kelmayisaurus, the sauropod Asiatosaurus (which might be related to the Asian sauropod Euhelopus), and a second unidentified sauropod which might be related to Camarasaurus (Dong 1973, pages 45-52).
Below is my reconstruction of what I think Phaedrolosaurus might have looked like. The reconstruction is based upon Deinonychus, which it might have been related to. However, since the tooth of Phaedrolosaurus was more robustly built, it’s possible that the entire animal may have been stronger and more muscular than its North American relative. Short thick sturdy teeth are indicative of a powerful bite, and therefore the animal likely had a very robustly-built skull to handle the impressive bite force. Therefore, I have portrayed Phaedrolosaurus with a more strongly-built skull and a more muscular body compared to Deinonychus.
Phaedrolosaurus ilikensis. © Jason R. Abdale (April 18, 2025).
I truly enjoy writing my articles and drawing my art, but it’s increasingly clear that I can’t keep this up without your gracious financial assistance. Kindly check out my pages on Redbubble and Fine Art America if you want to purchase merch of my artwork. Consider buying my ancient Roman history books Four Days in September: The Battle of Teutoburg and The Great Illyrian Revolt if you or someone that you know loves that topic. Also, please consider becoming a patron on my Patreon page so that I can afford to purchase the art supplies and research materials that I need to keep posting art and articles onto this website.
Take care, and, as always, keep your pencils sharp.
Bibliography
Brusatte, Stephen L.; Benson, Roger B. J.; Xu, Xing (2010). “The evolution of large-bodied theropod dinosaurs during the Mesozoic in Asia”. Journal of Iberian Geology, volume 36, issue 2 (December 2010). Pages 275–296.
https://www.researchgate.net/publication/260714806_The_evolution_of_large-bodied_therood_dinosaurs_during_the_Mesozoic_in_Asia.
Brusatte, Stephen L.; Benson, Roger B. J.; Xu, Xing (2012). “A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous of China”. Acta Palaeontologica Polonica, volume 57, issue 1 (March 1, 2012). Pages 65-72.
https://bioone.org/journals/acta-palaeontologica-polonica/volume-57/issue-1/app.2010.0125/A-Reassessment-of-Kelmayisaurus-petrolicus-a-Large-Theropod-Dinosaur-from/10.4202/app.2010.0125.full.
Chen, Yan; Cogne, Jean-Pascal; Courtillot, Vincent; Avouac, Jean-Philippe; Tapponnier, Paul; Wang, Gongque; Bai, Meixiang; You, Hongzi; Li, Ming; Wei, Chunsheng; Buffetaut, Eric (1991). “Paleomagnetic Study of Mesozoic Continental Sediments Along the Northern Tien Shan (China) and Heterogeneous Strain in Central Asia”. Journal of Geophysical Research, volume 96, issue 83 (March 10, 1991). Pages 4,065-4,082.
https://authors.library.caltech.edu/34009/1/90JB02699.pdf.
Dong, Zhiming (1973). “Dinosaurs from Wuerho”. Memoirs of the Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, volume 11 (1973). Pages 45-52.
Maisch, Michael W.; Matzke, Andreas T.; Sun, Ge (2004). “A new dsungaripteroid pterosaur from the Lower Cretaceous of the southern Junggar Basin, north-west China”. Cretaceous Research, volume 25, issue 5 (October 2004). Pages 625-634.
Norman, David B. (1990). “Problematic Theropoda: ‘Coelurosaurs’”. In Weishampel, D. B.; Dodson, Peter; Osmólska H., eds. The Dinosauria. Berkeley: University of California Press, 1990. Pages 280-305.
Rauhut, Oliver W. M.; Xu, Xing (2005). “The Small Theropod Dinosaurs Tugulusaurus and Phaedrolosaurus from the Early Cretaceous of Xinjiang, China”. Journal of Vertebrate Paleontology, volume 25, issue 1 (2005). Pages 107-118.
https://www.researchgate.net/publication/235907336_The_small_theropod_dinosaurs_Tugulusaurus_and_Phaedrolosaurus_from_the_Early_Cretaceous_of_Xinjiang_China.
Xi, Dangpeng; Wan, Xiaoqiao; Li, Guobiao; Li, Gang (2019). “Cretaceous integrative stratigraphy and timescale of China”. Science China Earth Sciences, volume 62, issue 1 (2019). Pages 256-286.
Xing, Lida; Lockley, Martin G.; Jia, Chengkai; Klein, Hendrik; Niu, Kecheng; Zhang, Lijun; Qi, Liqi; Chou, Chunyong; Romilio, Anthony; Wang, Donghao; Zhang, Yu; Persons, W. S.; Wang, Miaoyan (2021). “Lower cretaceous avian-dominated, theropod, thyreophoran, pterosaur and turtle track assemblages from the Tugulu Group, Xinjiang, China: ichnotaxonomy and palaeoecology”. PeerJ, 9: e11476.
https://peerj.com/articles/11476/.
Xing, Lida; Lockley, Martin G.; Li, Zhongdong; Klein, Hendrik; Chen, Shaojie; Persons IV, W. Scott; Wang, Miaoyan (2020). “Large Scale Dinoturbation in Braided Stream Deposits: Evidence from the Cretaceous Tugulu Group of the Hami Area, Eastern Xinjiang, China”. Biosis: Biological Systems, volume 1, issue 2 (2020). Pages 72-84.
Yang, J. L.; Wang, Q. F.; Lu, H. N. (2008). “Cretaceous charophyte floras from the Jungar Basin, Xinjiang, China”. Acta Micropalaeontologica Sinica, volume 12, issue 25 (2008). Pages 345-363.
Fossilworks. “Kelmayisaurus petrolicus Dong 1973 (allosauroid)”.
http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=65212. Accessed on June 30, 2023.
Fossilworks. “Wuerho, IVPP site 64043 (Cretaceous of China)”.
http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=49817&is_real_user=1. Accessed on June 30, 2023.
Categories: Paleontology, Uncategorized
DINOSAURS AND BARBARIANS 
Leave a comment