The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

• Published in: iScience 2023-02, Vol.26 (2), p.105989-105989, Article 105989
• Main Authors: Darroch, Simon A.F., Gutarra, Susana, Masaki, Hale, Olaru, Andrei, Gibson, Brandt M., Dunn, Frances S., Mitchell, Emily G., Racicot, Rachel A., Burzynski, Gregory, Rahman, Imran A.
• Format: Article
• Language: English
• Subjects: Evolutionary biology; Paleobiology; Zoology
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2023.105989

Rangeomorphs are among the oldest putative eumetazoans known from the fossil record. Establishing how they fed is thus key to understanding the structure and function of the earliest animal ecosystems. Here, we use computational fluid dynamics to test hypothesized feeding modes for the fence-like rangeomorph Pectinifrons abyssalis, comparing this to the morphologically similar extant carnivorous sponge Chondrocladia lyra. Our results reveal complex patterns of flow around P. abyssalis unlike those previously reconstructed for any other Ediacaran taxon. Comparisons with C. lyra reveal substantial differences between the two organisms, suggesting they converged on a similar fence-like morphology for different functions. We argue that the flow patterns recovered for P. abyssalis do not support either a suspension feeding or osmotrophic feeding habit. Instead, our results indicate that rangeomorph fronds may represent organs adapted for gas exchange. If correct, this interpretation could require a dramatic reinterpretation of the oldest macroscopic animals. [Display omitted] •The rangeomorph Pectinifrons created unique patterns of fluid flow•Flow patterns do not support suspension feeding or osmotrophy in Pectinifrons•Pectinifrons and the harp sponge converged on similar forms for different functions•Rangeomorph fronds might be organs adapted for gas exchange Zoology; Evolutionary biology; Paleobiology