New information on the Wukongopteridae (Pterosauria) revealed by a new specimen from the Jurassic of China

A taxonomic approach on diagnostic characters used to define new pterosaur taxa and an estimation of pterosaur diversity

Diagnostic characters from 227 pterosaur species were listed, separated into cranial or post-cranial elements and counted. From 21 post-cranial and 23 cranial elements, most diagnostic characters were related to phalanges (15%) and rostrum. Post-cranial characters comprise 44.23%, and cranial characters 55.77% of all characters used in pterosaur diagnoses. The highest correlation between diagnostic features occurs between the coracoid and the scapula. 25.11% and 28.63% of sampled taxa were diagnosed with 3-4 and 5-6 characters, respectively. The mean number of 6.79 characters was found in specimens with both cranial and post-cranial elements, and 4.86 and 4.17 in those with just cranial or post-cranial elements, respectively. 31 from 227 species (13.7%) were erected based on single elements, which are most frequently complete or partial mandibles (n=18). We estimate that 23.4% of the total pterosaur genera are currently known, with 90% of this diversity to be unveiled up to 2145. As the requirements of broad and cautious revision of genus/group must be undertaken, and some deposits will provide mostly fragmented and incomplete material, the assignment of fairly incomplete specimens to the most inclusive taxonomic level is feasible. Tracing this scenario can guide future works on the description of new pterosaur taxa.

An early juvenile of Kunpengopterus sinensis (Pterosauria) from the Late Jurassic in China

The Wukongopteridae is a transitional clade between the long- and short-tailed pterosaur groups, and at least ten specimens have been studied without a determined juvenile specimen. Here, we described a small-sized Kunpengopterus sinensis, less than half the size of the holotype, which is the smallest specimen in wukongopterids. Based on unossified small elements, unfused cranial and postcranial elements, and grooves on the bone surface, this specimen is thought to be at least an early juvenile or even a late hatchling. By comparing the juvenile and subadult specimens of K. sinensis, we have found that the mid region of the upper and lower jaws had a higher growth rate than the anterior part, and that the growth rates were similar in most postcranial elements except for a higher rate in the caudal vertebrae. We revised the previous diagnosis of K. sinensis and specified that two characteristics, nasoantorbital fenestra approximately 40% of the skull length and a thin and relatively short maxillary process of the jugal, should be diagnostic in subadult or adult specimens. We have also found that pedal features are stable during ontogeny and can be diagnostic in juvenile, subadult or adult specimens in K. sinensis.

A new darwinopteran pterosaur reveals arborealism and an opposed thumb

Pterosaurs, which lived during the Mesozoic, were the first known vertebrates to evolve powered flight.^1,2 Arboreal locomotion has been proposed for some taxa,^3,4 and even considered to have played a role in the origin of pterosaur flight.^5,6 Even so, there is still need for comprehensive quantitative ecomorphological analyses.^3,4 Furthermore, skeletal adaptations correlated to specialized lifestyles are often difficult to recognize and interpret in fossils. Here we report on a new darwinopteran pterosaur that inhabited a unique forest ecosystem from the Jurassic of China. The new species exhibits the oldest record of palmar (or true) opposition of the pollex, which is unprecedented for pterosaurs and represents a sophisticated adaptation related to arboreal locomotion. Principal-coordinate analyses suggest an arboreal lifestyle for the new species but not for other closely related species from the same locality, implying a possible case of ecological niche partitioning. The discovery adds to the known array of pterosaur adaptations and the history of arborealism in vertebrates. It also adds to the impressive early bloom of arboreal communities in the Jurassic of China, shedding light on the history of forest environments.

Assessing ontogenetic maturity in extinct saurian reptiles

Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life-history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least-inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260-million-year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. 'juvenile', 'mature') and provide routes for better clarity and cross-study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method-specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, 'Ontogenetic Assessment', be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well-represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well-constrained, empirically tested methods.

New anatomical information of the wukongopterid Kunpengopterus sinensis Wang et al., 2010 based on a new specimen

The Wukongopteridae compose a non-pterodactyloid clade of pterosaurs that are the most abundant flying reptiles in the deposits of the Middle-Late Jurassic Yanliao Biota. Until now, five species of three genera and two additional unnamed specimens have been described. Here we report on a new material, IVPP V 23674, that can be referred to the wukongopterid Kunpengopterus sinensis due to several features such as a comparably short nasoantorbital fenestra, the dorsally rising posterodorsal margin of the ischium, and the very short first pedal phalanx of digit V relative to metatarsal IV. IVPP V 23674 provides the first view of a wukongopterid palate, which differs from all other pterosaurs by having a very large postpalatine fenestra and laterally compressed choanae, indicating that the evolution of the pterosaur palate was more complex than previously thought. Sesamoid bones at the dorsal side of manual unguals are present and are reported for the first time in a wukongopterid suggesting an arboreal life-style for these pterosaurs.