The origin of Pterosaurs
Introduction
Pterosaurs were a long-lived and highly diverse clade of flying reptiles that first appeared in the fossil record in the early-middle Late Triassic (Benton, 1985; Bennett, 1997; Barrett et al., 2008; Upchurch et al., 2015). The oldest definitive specimens are Norian in age (227–208.5 million years old) (e.g., Wild, 1978), and come from a range of localities that are exclusively within the Northern Hemisphere (Barrett et al., 2008). A single Carnian-Norian (237–208.5 million years old) specimen that could represent a ‘basal’ pterosaur, named Faxinalipterus minima, is also known from the Caturrita Formation in Brazil, but this specimen is currently of uncertain affinity (Bonaparte et al., 2010).
Recent time-calibrated phylogenetic analyses (based upon the hypothesis that pterosaurs are archosaurs closely related to dinosaurs) have put the origination of the Pterosauria near to the Olenekian-Anisian boundary. This equates to the end of the Early Triassic and start of the Middle Triassic, roughly 250 million years ago (Nesbitt et al., 2017). This would also suggest that there is a substantial ghost lineage for the clade spanning almost 40 million years. This gap in the fossil record has yet to be filled, despite that fact that an abundance of other terrestrial archosaurs, including members of Avemetatarsalia (currently believed to be the clade that pterosaurs are nested in within Archosauria), are continuously being discovered in Middle and early Late Triassic localities (Ferigolo and Langer, 2006; Kammerer et al., 2012, Kammerer et al., 2020; Nesbitt et al., 2010, Nesbitt et al., 2017; Martz and Small, 2019; Pacheco et al., 2019). There are also currently no known ‘transitional’ pterosaur taxa that display a combination of plesiomorphic and derived anatomical characters suggestive of a lack of powered flight capability. As yet we do not know of any ‘missing-link’ pterosaurs that appear more as if they could glide or perhaps adopt other types of behaviour that differ from all currently known pterosaurs. This has made it difficult to understand precisely how the pterosaurs acquired their strange suite of unique anatomical characteristics. However, regardless of how and when pterosaurs originated, not long after their first appearance the clade rapidly diversified, radiating and spreading through the Late Triassic and Jurassic, lasting until the end-Cretaceous mass extinction, and achieving in this time a great diversity and disparity, as well as a global distribution (Unwin, 2003a; Barrett et al., 2008; Kellner et al., 2019; Bestwick et al., 2020).
Section snippets
Pre-cladistic days
The discovery of the first pterosaur specimen back in the 18th century (Collini, 1784) presented a real challenge for early natural historians and anatomists who wished to correctly establish this animal's affinities. This discovery was, after all, more than fifty years before Richard Owen would name the Dinosauria (Owen, 1842); palaeontology as a subject had not even been formulated, with typical ‘research’ of the time being mainly focused on trying to fit fossil taxa into extant clades, or
Pterosaurs as ornithodirans
The hypothesis that pterosaurs are ornithodirans (i.e., are the sister taxon to or lie within the Dinosauromorpha) is the hypothesis most commonly found in modern cladistic analyses and can be considered the current consensus view of pterosaur origins (Fig. 2a). Numerous analyses of various kinds have recovered this topology (Benton, 1990, Benton, 1999, Benton, 2004; Juul, 1994; Sereno, 1991; Novas, 1996; Sereno and Arcucci, 1990; Kellner, 1996; Bennett, 1996a; Nesbitt, 2007, Nesbitt, 2011) The
What are the earliest diverging Pterosaurs?
The question over which pterosaur taxa represent the most ‘basal’ members of Pterosauria is also still unresolved; this adds further problems to the issue of establishing pterosaur origins. Without certainty on which taxa are the earliest diverging members, we cannot yet say which give us the best understanding of the ‘basal’ condition of the pterosaur lineage and which are the best representatives to be included in phylogenetic analyses.
The primary candidates were long thought to be
Anatomical character data: drawbacks and insights
There remain important issues with the phylogenetic analyses considered above that have yet to be resolved, and indeed to a certain degree cannot be resolved under the current states of pterosaur research. It is something of a scientific cliché to state that more data or more research is required, but in the case of pterosaur origins it is certainly true.
An obvious problem for resolving the question of pterosaur origins is the relative lack of cladistic characters that can be applied to them.
New analyses: material & methods
This study further builds upon the anatomical dataset used in the recent analyses presented by Kammerer et al. (2020). This dataset was initially compiled by Nesbitt et al. (2010) and has subsequently been modified by Kammerer et al. (2012), Peecook et al. (2013), Martínez et al. (2012), Nesbitt et al., 2017, Nesbitt et al., 2019, and Müller et al., 2018a, Müller et al., 2018b. In its most up to date form, the dataset contained two pterosaur taxa Dimorphodon and Eudimorphodon. For reasons
New analyses: results
With an expanded dataset containing the new taxa, the first analysis, which used equal weights implementation of parsimony, produced 99 most parsimonious tree (MPTs) each of length 1429 steps. In this analysis, the pterosaurs form a clade nested within Avemetatarsalia, in a close relationship with the lagerpetids and dinosauriforms (Fig. 5a). Just as in the results presented in the most recent analyses of Kammerer et al. (2020), the lagerpetids are found to be closer to pterosaurs than to
Discussion
The position of the Pterosauria within the wider archosaurian and reptilian lineages is further supported by the expanded analyses of this work. With greater representation of early pterosaur taxa and, by association, better representation of the anatomy of the earliest diverging pterosaurs, the analyses seem to further support a position close to the origin of the dinosaurs. The clade Ornithodira, as defined, contains pterosaurs and dinosaurs and a number of other taxa that are, perhaps,
Conclusions
- 1.
Pterosaurs can confidently be placed in the avemetatarsalian lineage within Archosauria, along with dinosaurs and other close dinosaur and pterosaur relatives like the lagerpetids and aphanosaurs; this position is finding increasing levels of support, with multiple analyses that use a range of different anatomical datasets recovering the same or very similar hypothesis in recent years.
- 2.
The addition of many more pterosaur taxa to an existing large anatomical dataset of archosaurs does not alter
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowldgements
The author is grateful to two anonymous reviewers for taking the time to carefully review this work and for the numerous helpful comments and suggestions that they made during the peer-review process that helped to improve the overall quality of this work prior to publication.
The author is also indebted to Dr. David Hone for the significant contributions that he made to this piece of research in its earliest stages. Dr. Hone originally approached the author with the idea of compiling and
References (138)
- et al.
The earliest Pterodactyloid and the origin of the group
Curr. Biol.
(2014) The phylogenetic position of the Pterosaurs within the Archosauromorpha
Zool. J. Linnean Soc.
(1996)The tarsus of erythrosuchid archosaurs, and the implications for early diapsid phylogeny
Zool. J. Linnean Soc.
(1996)- et al.
The validity of Lagosuchus talampayensis Romer, 1971 (Archosauria, Dinosauriformes), from the Late Triassic of Argentina
Breviora
(2019) - et al.
Phylogenetic reassessment of Pisanosaurus mertii Casamiquela, 1967, a basal dinosauriform from the Late Triassic of Argentina
J. Syst. Palaeontol.
(2017) - et al.
A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae
Palaeontology
(2008) Über entwicklung, ausbildung und absterben der flugsaurier
Palaeontol. Z.
(1922)- et al.
Reconstructing the flight apparatus of Eudimorphodon
Pisanosaurus mertii and the Triassic ornithischian crisis: could phylogeny offer a solution?
Hist. Biol.
(2019)Testing pterosaur ingroup relationships through broader sampling of avemetatarsalian taxa and characters and a range of phylogenetic analysis techniques
PeerJ
(2020)
A new hypothesis of dinosaur relationships and early dinosaur evolution
Nature
Baron et al. reply
Nature
Pterosaur distribution in time and space: an atlas
A pterodactyloid pterosaur pelvis from the Santana formation of Brazil: implications for terrestrial locomotion
J. Vertebrate Paleontol.
A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: year-classes of a single large species
J. Palaeontol.
Year-classes of pterosaurs from the Solnhofen Limestone of Germany: taxonomic and systematic implications
J. Vertebr. Paleontol.
The arboreal leaping theory and the origin of pterosaur flight
Hist. Biol.
Pterosaur flight: the role of actinofibrils in wing function. Histor
Biol
The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon
Palaeontogr. A
Morphological evolution of the wing of pterosaurs: myology and function
The phylogenetic position of the Pterosauria within the Archosauromoprha
Acta Geosci. Sin.
The phylogenetic position of the Pterosauria within the Archosauromoprha re-examined
Hist. Biol.
Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopper
PeerJ.
Classification and phylogeny of the diapsid reptiles
Zool. J. Linnean Soc.
Origin and interrelationships of dinosaurs
Scleromochlus taylori and the origin of dinosaurs and pterosaurs
Philos. Trans. R. Soc. Lond. B Biol. Sci.
Origin and relationships of Dinosauria
Archosaur phylogeny and the relationships of the Crocodylia
Dietary diversity and evolution of the earliest flying vertebrates revealed by dental microwear texture analysis
Nat. Commun.
Handbuch der Naturgeschichte
Auflage; Göttingen (Dietrich’sche Buchhandlung)
Pterosauria from the Late Triassic of Southern Brazil
Lect. Notes Earth Sci.
Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years
Nat. Ecol. Evol.
Representing supraspecific taxa in higher-level phylogenetic analyses: guidelines for palaeontologists
Palaeontology
The Dinosaur Hunters
The evolution of the archosaur pelvis and hind-limb: an explanation in functional terms
Respiratory evolution facilitated the origin of pterosaur flight and aerial gigantism
PLoS One
Foot posture in a primitive pterosaur
Nature
Sur quelques Zoolithes du Cabinet d’Histoire naturelle de S.A.S.E. Palatine & de Bavière, à Mannheim
Acta Acad. Theodoro Palatinae
Synopsis of the extinct Batrachia, Reptilia and Aves on North America
Trans. Am. Philos. Soc.
Reptile volant
New observations on the osteology and taxonomic status of Preondactylus buffarinii Wild, 1984 (Reptilia, Pterosauria)
Boll. Soc. Paleontol. Ital.
Seazzadactylus venieri gen. et sp. nov., a new pterosaur (Diapsida: Pterosauria) from the Upper Triassic (Norian) of northeastern Italy
PeerJ
The Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja, Argentina): fossil tetrapods, high-resolution chronostratigraphy, and faunal correlations
Sci. Rep.
Does archosaur phylogeny hinge on the ankle joint?
J. Vertebr. Paleontol.
The flight of Sharovipteryx mirabilis: the world’s first delta-winger glider
J. Evol. Biol.
The early history and relationships of the Diapsida
Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria
Nature
The first dsungaripterid pterosaur from the Kimmeridgian of Germany and the biomechanics of pterosaur long bones
Acta Palaeontol. Pol.
Morphofunctioanal Evolution of the Pelvic Girdle and Hindlimb of Dinosauromorpha on the Lineage to Sauropoda
A Late Triassic dinosauriform from south Brazil and the origin of the ornithischian predentary bone
Hist. Biol.
Cited by (7)
A review of the Jurassic and Cretaceous Gondwanan pterosaur record
2023, Gondwana ResearchThe earliest evidence of deep-sea vertebrates
2023, Proceedings of the National Academy of Sciences of the United States of AmericaAdvanced Research on Fossil Insects
2022, Taxonomy