#rangeomorph

Species: P. abyssalis

Etymology: “Comb of leafy branches,” after its shape

Age and Location: Ediacaran of Newfoundland

Classification:?Eukarya:incertae sedis: Rangeomorpha

Pectinifronsis a rangeomorph, and so broadly similar to Fractofusus,which also was a sessile organism that reclined on the surface, and with which it shared a presumed osmotrophic lifestyle and fractal anatomy. However, despite the simplicity of their body plans, there was still substantial variation between different genera. Pectinifronswas an enormous organism by Ediacaran standards, with the largest individuals being nearly a meter long. Unlike Fractofusus,which lay flat on the seafloor, Pectininfronswas taco-shaped, with its midline lying on the seafloor and two rows of fronds sticking upward. While superficially it resembled a folded Fractofusus, though, it appears to have grown differently: all Fractofusushave the same number of fronds and are essentially identical except for size, while larger Pectinifronshave more fronds. This suggests that Fractofususdeveloped an adult morphology early in life and simply grew by expanding itself, whereas Pectinifronsgrew by lengthening the midline of its body and growing additional fronds. Such a dramatic difference in growth strategies suggests that the rangeomorphs might be more diverse than previously thought. What kind of organism rangeomorphs are–or if they’re a single kind of organism at all–remains unknown.

Sources

Bamforth EL., Narbonne GM., Anderson MM., Bamforth EL., Narbonne GUYM., Anderson MM., Crescent S. 2008. Growth and Ecology of a Multi-Branched Ediacaran Rangeomorph from the Mistaken Point. Journal of Paleontology 82:763–777.
Hoyal Cuthill JF., Conway Morris S. 2014. Fractal branching organizations of Ediacaran rangeomorph fronds reveal a lost Proterozoic body plan. Proceedings of the National Academy of Sciences of the United States of America.