The green alga Chaetocladus (Dasycladales)

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Geography and Geology


Two species of the enigmatic alga Chaetocladus, C. ruedemanni (new species) and C. dubius (previously regarded as a graptolite incertae sedis), are described from the Silurian Lockport Group of New York and Ontario, Canada, respectively. A comprehensive investigation reveals that these and other Chaetocladus taxa occur in distinctive Konservat-Lagerstatten in association with other thallophytic algae, annelid worms, and lightly sclerotized arthropods. The sedimentology, taphonomy, and biotic composition of Chaetocladus-bearing deposits indicate that this alga thrived in shallow, stagnant, occasionally storm-agitated marine environments. In these settings, preservation of thallophytic algae and associated soft-bodied animals apparently was facilitated by a combination of obrution, anoxia, and early diagenesis of the burial muds. The morphology of Chaetocladus corresponds to that characteristic of the green alga order Dasycladales, and it is herein referred to this long-ranging taxon as a representative of a new subtribe (Chaetocladinae, new subtribe) within the tribe Salpingoporelleae (emended herein), family Triploporellaceae (emended herein). This euspondyl, endosporate genus extends the range of the euspondyl dasyclads significantly, from the Early Devonian back to the Middle Ordovician, and bridges an evolutionary gap between early Paleozoic aspondyl, endosporate forms and middle Paleozoic euspondyl, cladosporate forms.

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