Beijing, October 10 (Reporter Sun Zifa) The fossil research of China's Hami pterosaur fauna, known as the "Eden of Pterosaurs", has always attracted much attention. The research team of Wang Xiaolin of the Institute of Vertebrate Paleontology and Paleoanthropology (Institute of Paleovertebrate Paleontology) of the Chinese Academy of Sciences has been committed to the research of Hami pterosaur fauna in the past 9 years, and they and their collaborators recently discovered the first fossilized theropod footprints about 20 million to 1 million years ago in the "pterosaur Eden".

This is also the first discovery of Cretaceous dinosaur footprints in Hami and Tu (Turpan) Harmi (Hami) basins, further increasing the diversity of Hami pterosaur fauna. Based on the size of the fossil footprint, the collaborative team deduced that the traced dinosaur was about 65 cm tall, 171 cm long and weighed about 30 kg, making it a small theropod.

Well-preserved Hami theropod footprints fossilized (A. pseudo-color depth map; B. specimen photograph; C. line map). Wang Xiaolin's team/Courtesy photo

The important dinosaur research results of the pterosaur fauna were completed by Wang Xiaolin's research team in cooperation with Shenyang Normal University and Hami Museum, and the research paper was recently published online in the international professional academic journal Historical Biology.

Footprint fossils can obtain important information such as paleontological ecological habits

Researcher Wang Xiaolin, the corresponding author of the paper and the leader of the Hami scientific expedition team of the Institute of Paleovertebrate of the Chinese Academy of Sciences, pointed out in an interview with reporters that as an important type of fossil relics, the importance of footprint fossils lies in the fact that some information on paleontological ecological habits that cannot be provided by bone fossils can be obtained:

First, in the case of few or lack of bone fossils, the study of footprint fossils can make up for the incompleteness of the bone fossil record and obtain the basic characteristics of the tracer, including its type, hip height, body length and weight and other information.

Second, special trace characteristics can reflect some special behavioral habits of the tracer before his death, such as movement posture and speed, herdiness, predation behavior, walking and landing methods of flying animals, etc., which can be found in the change of trace characteristics, which is important information that bone fossils cannot provide.

Third, well-preserved footprint fossils such as claw tracks, toe pads, toe pads, etc., can provide some characteristics of the soft tissues of the tracer's feet.

Fourth, footprint fossils can also provide important information in stratigraphy, paleoenvironment, paleoecology and paleogeography.

The footprints were left by small theropod dinosaurs walking on the shores of the lake

The latest research has found that the Hami theropod dinosaur footprint fossils were collected by Hami scientific expeditions in recent years in the Hami Gobi Yadan area of the Tuha Basin about 1 million to 3 million years ago, a total of 1 specimens and 2 footprint fossils, from different layers of the two sites. Among them, two separate footprints were discovered in 3 at the first site, the Daidao Tongtiandong, which is the earliest footprint fossil found in this area, and a rich group of footprints including sauropods, pterosaurs, birds and turtles and turtles have also been found.

Through the detailed description and comparative analysis of the morphological characteristics of the footprint fossils, it is found that the overall footprint of Hami theropod dinosaurs is narrow and long, with an average length of about 16 cm, bipedal walking, functional three-toed, clear sharp claw tracks visible at the distal end of the toe, which are small theropod footprints. The length and width of the footprint are relatively small, the average value is 1.44, the length to width ratio of the toe tip triangle is also small, the average value is 0.55, the angle between the lateral toes is larger at 49.52 degrees, the length of the middle toe (third toe) exceeds the two toes, and a clear interpad suture and a toe pad located on the back of the middle toe can be seen.

The stratigraphic order and fossil stratigraphy of the Cretaceous Sheng Jinkou Formation under the Hami Sea Channel. Wang Xiaolin's team/Courtesy photo

Comparing the main features of Hami theropod footprints, including having a lower footprint aspect ratio and a smaller triangular toe aspect ratio, it was found to be very similar to the main features of the genus Thheropod footprints with larger dimensions (usually greater than 25 cm), but the size of Hami theropod footprint fossils was significantly smaller.

In recent years, small-sized footprints of Cyronsaurus have also been found more and more around the world, such as footprints from Beijing, Sichuan, Hebei, Shaanxi and the Lower Cretaceous strata of the United Kingdom and Japan, which are all smaller in size and have low footprint aspect ratio and low triangular aspect ratio and other characteristics, which are currently classified as similar genera of Cynosaurus footprints, Hami theropod footprints are also included in them.

The discovery of Hami theropod footprints further expanded the distribution range of this type of footprint, and also provided a footprint basis for the height and length of theropod dinosaurs in Hami pterosaur fauna. At the same time, combined with the discovery of stratigraphic sequence, sedimentary characteristics and fossilized invertebrate remains, the research team deduced that these footprints were left by small theropod dinosaurs walking on the shores of the lake.

Important progress has been made in the study of Hami pterosaurs and their fauna

Wang Xiaolin said that since 2006, the Hami scientific expedition team has carried out field surgery in Hami Gobi for more than ten consecutive years, and found a large number of male and female Hami pterosaurs from juvenile to adult, as well as the world's first 3D preserved pterosaur eggs and embryo fossils, and has made important progress in the morphological characteristics, phylogeny, growth mode, reproduction, ecological habits, fossil burial and cluster death of Hami pterosaurs, and these results have been published in the cover article of Modern Biology under Cell and Science and other international academic journals, it is considered the most exciting discovery in pterosaur research in more than 200 years.

At the same time, research results on the fauna of Hami pterosaurs have been emerging in recent years. Among them, the first study in 2021 found two sauropod fossils, named Chinese Silk Road Dragon and Xinjiang Hami Dragon, which not only increased the diversity of Hami pterosaur fauna, but also increased the diversity of Chinese Early Cretaceous sauropods.

In 2023, the shoulder girdle and bone histology of Hami pterosaur and the tooth morphology and histology of Hami pterosaur were studied, which preliminarily revealed the basic biological information of Hami pterosaur flight mechanism and tooth growth: in terms of flight, it has both similarity with bats and birds, as well as its own unique adaptation; In terms of tooth growth, it is assumed that the time to form a smaller tooth is about 80 days.

Hami theropod footprints fossilized and their line drawings. Wang Xiaolin's team/Courtesy photo

Wang Xiaolin said that the Hami area has now become the world's largest and richest fossil production area of pterosaurs, and hundreds of millions of pterosaurs have thrived here, which is a veritable "pterosaur Eden". He revealed that at present, this place has become Hami pterosaur-Yadan National Geopark, and the construction of the pterosaur (site) museum is underway, aiming to effectively protect the important fossils of Hami pterosaur fauna and its sites, and provide young people and the public with a window to understand the once flourishing and mysterious flying reptiles on Earth. (End)