Darwinopterus

Darwinopterus (meaning "Darwin's wing") is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates to the middle Jurassic period, 160.89–160.25 Ma ago. The type species, D. modularis, was described in February 2010. D. modularis was the first known pterosaur to display features of both long-tailed ("rhamphorhynchoid") and short-tailed (pterodactyloid) pterosaurs, and was described as a transitional fossil between the two groups. Three additional species, D. camposi, D. linglongtaensis, and D. robustodens, were described from the same fossil beds in February 2025, December 2010, and June 2011, respectively.

Darwinopterus, like its closest relatives, is characterized by its unique combination of basal and derived pterosaurian features. While it had a long tail and other features characteristic of the 'rhamphorhynchoids', it also had distinct pterodactyloid features, such as long vertebrae in the neck and a single skull opening in front of the eyes, the nasoantorbital fenestra (in most 'rhamphorhynchoids', the antorbital fenestra and the nasal opening are separate).

Darwinopterus is distinguished from its close relatives by the greater relative length of the back portion of the skull compared to its jaws, thin nasal bone, and elongated hip bone (ilium). The teeth in all species were spaced widely with the longest teeth at the jaw tips. The teeth were spike-like in form, and set into tooth sockets with raised margins. The hand bones were relatively short, even shorter than the femur. The tail was long, with over 20 vertebrae, and was partially stiffened by long, thin bony projections. Unlike other wukongopterids, the head crest found in males was supported by a thin bony extension of the skull, with a serrated top edge. The serrations probably helped anchor an even larger keratin extension.

Specimens of Darwinopterus have been divided into four distinct species, based largely on the size and shape of their teeth. The first, D. modularis, was named by Lü Junchang and colleagues in 2010. D. modularis had an especially elongated back end to the skull, and widely spaced, "spike-like" teeth. Later, D. linglongtaensis was named by Wang Xiaolin and colleagues in the same year. It was characterized by a shorter and taller skull and shorter, cone-shaped teeth. In 2011, Lü and another team of scientists described and named D. robustodens, for a new specimen with very robust teeth.

Some later work has noted the extreme similarity between these three species. A 2021 paper by Xuanyu Zhou and colleagues argued that the differences in dentition between D. modularis and D. rubustodens are due to taphonomic tooth slippage in the former (with "D. robustodens" representing the natural anatomy), and that differences seen in D. linglongtaensis compared to D. modularis are due to being based on a younger individual with ontogenetic differences in anatomy. Therefore, they considered D. modularis to be the only valid species in the genus, with the other two being junior synonyms.

In 2025, Xin Cheng and colleagues described a new species D. camposi based on a nearly complete, adult specimen (IVPP V 17957). It has more teeth than other species, with eighteen in the upper jaw and fourteen in the lower jaw; other wukongopterids have ten or eleven teeth in their upper jaws. The bony crest of D. camposi has a straight front edge, lacking a projection at the front, and has a smooth surface unlike the rough texture of other species. The fourth phalange of the wing finger (the outermost bone) is shorter than the first (the innermost finger bone), unique among species of Darwinopterus.

Below is a cladogram following Wang et al. (2017)

In 2024, it has been suggested that the genus Darwinopterus is polyphyletic based on phylogenetic analyses by Hone et al. (2024), who recovered the other three species in various positions. A cladogram of their results is shown below.