The Evolution of Pneumatic Foramina in Pterosaur Vertebrae.

Richard Buchmann,Taissa Rodrigues

doi:10.1590/0001-3765201920180782

Richard Buchmann, Taissa Rodrigues

Open Access

https://doi.org/10.1590/0001-3765201920180782

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Abstract

Pterosaurs possess skeletal pneumatization, which can be assessed externally through the observation of pneumatic foramina. These foramina vary in position, shape, and number among taxa. Here we propose new characters referring to the position and number of pneumatic foramina present in cervical and dorsal vertebrae of pterosaurs. A cladistic analysis was performed after first-hand study of material in collections and using data from the literature in order to test these new characters for homology, and they were subsequently mapped in a strict consensus tree. The analysis resulted in nine equally parsimonious trees with 215 steps each. The strict consensus tree obtained does not present significant differences in relation to trees obtained in previous studies. The mapping performed identified that most pneumatic foramina evolved independently in several lineages, and only two of the eight added characters appeared once in the evolution of pterosaurs. In general, pneumatic foramina were more common in the Dsungaripteroidea, however, the flattened preservation of non-pterodactyloids and in the Archaeopterodactyloidea often precludes their visualization, and therefore the presence of vertebral pneumatization may be broaden with the discovery of new, better preserved specimens.

Highlights

Pterosaurs are known as the first vertebrates to develop the ability to fly actively
This data matrix focused on the Pterodactyloidea, which besides including the largest known pterosaurs, are generally better preserved, facilitating the visualization of pneumatic foramina and of skeletal pneumatization
The presence of pneumatic foramina on the lateral surface of the neural arch in midcervical vertebrae is relatively common among non-pterodactyloids, appearing as a synapomorphy of the Novialoidea and with independent origins in non-novialoid species such as Sordes pilosus, Dorygnathus banthensis and Carniadactylus rosenfeldi. The absence of this foramen is synapomorphic for the Pterodactyloidea (Figure 2a)

Summary

Introduction

Pterosaurs are known as the first vertebrates to develop the ability to fly actively. Besides pterosaurs and extant birds, postcranial pneumatization is observed in the Sauropodomorpha and non-avian Theropoda (O’Connor 2006, Butler et al 2012), raising questions about the evolution of this system in archosaurs (Butler et al 2012). As some archosauriforms, such as Erythrosuchus, have limited evidence of pneumatization such as foramina and fossae that do not contact pneumatic chambers, Butler et al (2012) did not exclude the possibility of skeletal pneumatization being plesiomorphic for Archosauria

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