Species: P. abyssalis

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

Age and Location: Ediacaran of Newfoundland

Classification: ?Eukarya: incertae sedis: Rangeomorpha

Pectinifrons is 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. Pectinifrons was an enormous organism by Ediacaran standards, with the largest individuals being nearly a meter long. Unlike Fractofusus, which lay flat on the seafloor, Pectininfrons was 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 Fractofusus have the same number of fronds and are essentially identical except for size, while larger Pectinifrons have more fronds. This suggests that Fractofusus developed an adult morphology early in life and simply grew by expanding itself, whereas Pectinifrons grew 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.

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