Appeared in Fujian 96 million years ago? The largest Deinonychus was found from footprints!

In the winter of 2020, a team from China University of Geosciences (Beijing) and Yingliang Stone Natural History Museum discovered a collection of many dinosaur footprints in Shanghang County, Fujian Province. This was the first time that dinosaur-related fossils were discovered in Fujian. The relevant results were published in Cretaceous Research in 2023, and this collection of fossil footprints was called the "Longxiang Tracksite".

Figure 1. Longxiang footprints group (Image source: Reference 1)

In May of this year, further research on these footprints yielded results, discovering that they actually included the largest Deinonychus. How was this determined?

How to identify dinosaurs from their footprints?

Before introducing this scientific research result, we need to first introduce the classification method of dinosaur footprints.

Most of the dinosaurs we know about in museums or popular science books come from the fossils left behind by bones or bodies, which are called "physical fossils."

But as a kind of creature, dinosaurs had the opportunity to leave traces in the environment through their daily eating, drinking, defecating and urinating, such as footprints, tracks, feces, tooth marks, gastric stones, etc. These are called "trace fossils."

Figure 2: Fossilized feces of a large carnivorous dinosaur. Based on the origin and age, it is speculated that it may have been excreted by Tyrannosaurus Rex. (Image source: Wikipedia)

The biggest advantage of trace fossils is that they can tell us how these creatures lived in the past. For example, food residues can be seen in feces, and walking posture can be inferred from footprints. At the same time, there is a relatively large number of trace fossils. For example, a Tyrannosaurus Rex has about 380 bones, but the footprints left by walking every day can far exceed this number, so naturally there are more opportunities for them to be left behind.

However, the biggest disadvantage is that physical fossils and trace fossils are rarely preserved together, so it is often difficult to determine who produced these traces. Therefore, these trace fossils have their own classification and naming system to distinguish them from physical fossils.

Although it is difficult to identify the owner, many traces still leave many characteristics, providing a general direction for inferring the "perpetrator". For example, different types of dinosaurs have different numbers, shapes and sizes of toes. Through measurement and observation, it is possible to infer what kind of dinosaurs may have walked there.

For example, the footprints published this time are clearly from Deinonychus. Most carnivorous dinosaurs leave three-toed footprints, but Deinonychus has a sickle-shaped claw on its second toe, which is usually folded high to avoid wear and tear, leaving only two toes on the ground in the footprints of this type of dinosaur.

Figure 3. The foot of Deinonychus, where only two toes touch the ground (Image source: Wikipedia)

Who is the owner of Fujian's footprints?

There are two two-toed footprints in the Longxiang footprint group that were studied in depth this time, and the size difference is quite large, which means that they were left by different dinosaurs.

Figure 4. Distribution and size comparison of two-toed footprints (T1 and T3) in this study (Image source: Reference 2)

The smallest footprint is about 11 centimeters in size, with a total of 6 discontinuous footprints. The rest may not be preserved or covered by footprints of other dinosaurs. By comparing with footprints found in other areas in the past, this set of small two-toed footprints is closest to Velociraptorichnus, so it is classified into this genus of trace fossils. I have to emphasize again that trace fossils are another set of classifications, so although they are called Velociraptor footprints, they are not necessarily left by Velociraptor, but may also be left by other small dinosaurs that are close relatives.

Figure 5. Small two-toed footprints classified as Velociraptor traces (Image source: Reference 2)

The larger two-toed footprint is about 36 centimeters, which is larger than any two-toed footprint discovered in the past. Therefore, the research team gave this footprint a new name - Fujianipus yingliangi. The genus name naturally comes from the Fujian Province where it was discovered, and the species name is to thank the Yingliang Stone Natural History Museum for its important support and contribution to local dinosaur research.

Figure 6: Yingliang Fujian footprints are more than 36 cm long (Image source: Reference 2)

Figure 7. The two-toed footprints (A, B) of the Longxiang footprint group are compared with other two-toed fossils from around the world. It can be seen that the Fujian footprint (A) is the largest (Image source: Reference 2)

In the past, these two-toed footprints were classified as belonging to the "Dromaeopodidae". However, the high-raised claws are not exclusive to the Dromaeosaur family, and the closely related Troodon family also has this feature. Therefore, the research team proposed a new classification called "Deinonycosauripodidae", because Deinonychosaurs include both Dromaeosaurs and Troodontia, two families with "terror claws".

The fourth toe of the Fujian footprint is relatively short. After comparing it with Deinonychus footprint fossils from around the world, the research team inferred that this footprint may have come from a Troodon. The foot has to carry the weight of the body, so the size of the foot is related to the length of the leg and the body size. Through this 36-centimeter Fujian footprint, it can be inferred that the hip height of this Troodon was about 1.8 meters and the total length may be more than 5 meters. This size is considered a giant among Troodon and even the entire Deinonychus family. No, it is like a giant dragon.

Figure 8. Ecological restoration of footprints in Fujian, possibly left by a large troodontid (Image source: Reference 2)

In addition to inferring body size, footprints can also be used to infer an animal's movement state and speed through the length of each step (just like when we run, our steps are longer than when we walk). In the large and small footprints of the Longxiang footprint group, we can see that the steps are shorter, which means that the two dinosaurs were only walking or jogging when they left their footprints, and their speed was more than 7 kilometers per hour.

In other words, the two dinosaurs that left the footprints may not have had anything important to do at the time (such as chasing prey to have a meal, or escaping quickly to avoid being eaten), and they were simply strolling here leisurely, leaving this timeless mark.

Fighting with Tyrannosaurus Rex

But why did such a huge troodontid appear in Fujian at that time? This may be related to the overall environmental background at that time.

The Longxiang Footprints are located in the Shaxian Formation, in an alluvial fan plain near a river or lake. Radioactive isotope dating shows that they are about 96 million years old, in the early Late Cretaceous, which is roughly the transitional period between the early and late Cretaceous.

At this point in time, in addition to the Deinonychus represented by the Fujian footprints, there is another famous family of carnivorous animals that have evolved into larger ones - the Tyrannosauroids.

The most famous member of the Tyrannosaurus family is of course the Tyrannosaurus Rex from the late Cretaceous period, which could grow to over 12 meters in length. However, the family's large-sized form took a relatively short time. For example, the Moros intrepidus, also discovered in New Mexico, USA, about 96 million years ago, was an early member of the Tyrannosaurus family. Its body size was only about 3 meters, which may mean that the Tyrannosaurus family was just beginning to grow larger from this point in time.

Figure 9. Comparison of the size of Ozaurus and an adult (Source: Wikipedia)

Scientists speculate that the growth of Tyrannosaurus and some Deinonychus at this time may be related to the decline of the Allosaurus family. Before this, the ecological niche of large predators was occupied by the Allosaurus family, and other dinosaur families were suppressed. But the situation changed. The Allosaurus family, which once dominated the world, began to decline in the middle of the Cretaceous period, which gave other carnivorous dinosaurs the opportunity to grow larger and fill the power vacuum in this ecological niche.

Conclusion - The Emerging Dinosaur Kingdom Site

The history of dinosaur research in Fujian Province is relatively short. Before the discovery of the Longxiang footprint group in 2020, there was no record of the discovery of dinosaur fossils. However, with the unremitting efforts of many scientists, dinosaur research in Fujian Province has made great progress in recent years.

In addition to the largest Deinonychus footprints introduced in this study, the bizarre Fujianvenator prodigiosus from the late Jurassic was also published in September last year. This research was even published in the top scientific journal Nature, attracting international attention.

Figure 10. The strange Fujian dragon is a bird-winged dinosaur from the late Jurassic period (Image source: Reference 3)

According to preliminary research reports in 2023, the Longxiang Footprint Group has a total of 247 footprints, including 23 footprints and 14 separate footprints, from ornithopods, sauropods, theropods, etc.

Figure 11. The Longxiang footprint group also includes many other different types of dinosaur footprints (Image source: Reference 2)

This publication is a study of two-toed footprints, and these are only 11 of them. How many new, interesting and subversive dinosaur discoveries will there be in Fujian in the future? It is worth our anticipation.

References

1. Niu, K. and Xing, L., The first dinosaur track assemblages from the Upper Cretaceous Shaxian Formation, Fujian Province, southeastern China. Cretaceous Research (2023). 146, 105486.

2. Xing, L., et al., Deinonychosaur trackways in southeastern China record a possible giant troodontid. iScience (2024).

3. Xu, L., et al. A new avialan theropod from an emerging Jurassic terrestrial fauna. Nature (2023). 621 (7978): 336–343.

Author: Liao Junqi, PhD, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, visiting scholar at Yale University

Reviewer: Pei Rui, Associate Researcher, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.