to be closely related to dinosaurs even without hindlimb characters. They also criticized David Peters for drawing conclusions without access to the primary evidence, that is, the pterosaur fossils themselves. Hone and Benton concluded that, although more basal pterosauromorphs are needed to clarify their relationships, current evidence indicates that pterosaurs are avemetatarsalians, as either the sister group of Scleromochlus or a branch between the latter and Lagosuchus. An 2011 archosaur-focused phylogenetic analysis by Sterling Nesbitt benefited from far more data and found strong support for pterosaurs being avemetatarsalians, though Scleromochlus was not included due to its poor preservation. A 2016 archosauromorph-focused study by Martin Ezcurra included various proposed pterosaur relatives, yet also found pterosaurs to be closer to dinosaurs and unrelated to more basal taxa. Working from his 1996 analysis, Bennett published a 2020 study on Scleromochlus which argued that both Scleromochlus and pterosaurs were non-archosaur archosauromorphs, albeit not particularly closely related to each other. By contrast, a later 2020 study proposed that lagerpetid archosaurs were the sister clade to pterosauria. This was based on newly described fossil skulls and forelimbs showing various anatomical similarities with pterosaurs and reconstructions of lagerpetid brains and sensory systems based on CT scans also showing neuroanatomical similarities with pterosaurs. The results of the latter study were subsequently supported by an independent analysis of early pterosauromorph interrelationships. A related problem is the origin of pterosaur flight. Like with birds, hypotheses can be ordered into two main varieties: "ground up" or "tree down". Climbing a tree would cause height and gravity to provide both the energy and a strong selection pressure for incipient flight. Rupert Wild in 1983 proposed a hypothetical "propterosaurus": a lizard-like arboreal animal developing a membrane between its limbs, first to safely parachute and then, gradually elongating the fourth finger, to glide. However, subsequent cladistic results did not fit this model well. Neither protorosaurs nor ornithodirans are biologically equivalent to lizards. Furthermore, the transition between gliding and flapping flight is not well-understood. More recent studies on basal pterosaur hindlimb morphology seem to vindicate a connection to Scleromochlus. Like this archosaur, basal pterosaur lineages have plantigrade hindlimbs that show adaptations for saltation. At least one study found that the early Triassic ichnofossil Prorotodactylus is anatomically similar to that of early pterosaurs. Extinction It was once thought that competition with early bird species might have resulted in the extinction of many of the pterosaurs. It