The ancestor of pterosaurs couldn’t fly?

Recently, a new paper published in Nature stated that Brazilian researchers have discovered well-preserved partial skeletons of a rabbit lizard that lived about 230 million years ago. The rabbit lizard is a species that preceded the pterosaurs, and the species discovered this time has unusual characteristics. This discovery, together with other previous fossils, shows that the rabbit lizard was more diverse in morphology than the dinosaurs of the Triassic period.

Pterosaur

Wingless rabbit lizards are actually close relatives of pterosaurs

Tracing the origin of pterosaurs has always been an unresolved issue in paleontology. In 1900, German zoologist Föberlinger proposed that the ancestors of pterosaurs and dinosaurs were animals of the same era. Later, some paleontologists hypothesized that the ancestors of pterosaurs might be small tree-dwelling reptiles. In 1907, paleontologists discovered the fossil of Taylor's Crelosaurus in Scotland. This is a lagomorph that lived in a hot and humid environment 231 million years ago. It may be a close relative of pterosaurs.

The fossils of the rabbit lizard were first discovered in Texas, the United States in the 1930s and 1940s. Paleontologists have determined that the rabbit lizard has a strong sense of balance and is agile.

After the discovery of the 230-million-year-old rabbit lizard fossil puzzle, more rabbit lizard fossils were found in South America, and scientists have come to realize that the rabbit lizard was a small wingless reptile that lived mainly in the Triassic period between 237 million and 210 million years ago. Molecular biology studies have also shown that pterosaurs were likely to have evolved from terrestrial reptiles.

Paleontologists originally believed that the rabbit lizard was more closely related to dinosaurs because the length and shape of the rabbit lizard's bones are very similar to those of pterosaurs and dinosaurs. But later, a series of evidence increasingly supported that the rabbit lizard and pterosaurs were sister groups and they had a common ancestor. Researchers from the Department of Earth Sciences at Virginia Tech in the United States studied the fossils of the rabbit lizard found in North America, Brazil, Argentina and Madagascar in recent years, and conducted a detailed study of its skull and bones, convincing them that the rabbit lizard is a close relative of pterosaurs.

Possessing features associated with flight, rabbit lizards are morphologically diverse

The tuatara is a bipedal reptile without wings and cannot fly, but it shares some unique features with pterosaurs, such as the shape of the inner ear, and its bones also have many symbiotic traits, which strongly support the relationship between the two.

Using micro-CT scanning and 3D technology, the researchers found that the rabbit lizard had evolved some neural features related to the flight ability of pterosaurs. Apparently, these features evolved before the ability to fly, which solved the relationship between the rabbit lizard and pterosaurs from an anatomical and evolutionary perspective and provided a new model for studying the origin of reptiles and their flight ability.

The new species of rabbit lizard discovered by scientists in Brazil about 230 million years ago not only has the beak of a bird of prey, but also has prominent scimitar-shaped claws. These characteristics indicate that the rabbit lizard was highly specialized in its ecological niche. Its claws may have been used to help deal with prey or climb, and the beak would have functions such as sexual display, vocalization and temperature regulation in addition to eating.

Furthermore, the newly discovered traits of the tuatara suggest that this group was unusually diverse and as morphologically diverse as the pterosaurs of the Triassic, meaning that tuatara diversity was already thriving in the ancestors of dinosaurs and pterosaurs.

Pterosaurs have unique flight mechanisms and are closer to birds in terms of phylogeny

Pterosaurs roamed the skies for 150 million years during the Mesozoic Era and are the most persistent of the three flying vertebrate branches: pterosaurs, birds, and bats. Although the membranous wings of pterosaurs led some early scholars to believe that their flight mechanism was similar to that of bats, as research progressed, it was discovered that pterosaurs had a closer phylogenetic relationship with birds.

The latest research results of Chinese scientists on the shoulder girdle morphology and bone histology of Hami pterosaurs reveal the flight mechanism of pterosaurs. The research shows that Hami pterosaurs may have used the contraction of the supracoracoscopic muscles to lift their wings like birds, and the shoulder sockets of Hami pterosaurs are suspected to have retained cartilage tissue, which may have thick articular cartilage like birds to buffer flight pressure.

The study also found that pterosaurs had a unique flight mechanism. Unlike birds, whose scapula and coracoid bones never heal, the scapula and coracoid bones of Hami pterosaurs completely healed before they reached adulthood, forming a bony fusion of scapula and coracoid bones, which represented a unique shoulder girdle adaptation in the evolution of pterosaur flight.

Source: Popular Science Times

Author: Feng Weimin (the author is a researcher at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, and the honorary curator of the Nanjing Paleontological Museum)