T57 Phylogenetic Approaches to Paleobiology: Diversity, Rates, and Trends

Sunday, 9 October 2011
1:30 PM - 5:30 PM
Room 205AB

DEEP-WATER CORALS REVEAL MUCH DEEPER EVOLUTIONARY ORIGIN OF SCLERACTINIA

Paper number: T57-2
Program: Technical Sessions
Time: 1:45 PM – 2:00 PM

Authors

Abstract

The Scleractinia suddenly appear in the fossil record about 240 Mya, but the range of morphological variation seen in these Middle Triassic fossils is comparable to that of modern scleractinians, implying much earlier origins that have so far remained elusive. A significant factor in the inability to reconstruct early coral evolution is that, to date, deep-sea corals have been poorly represented in molecular phylogenetic analyses.

By adding new data from a large and representative range of deep-water species to existing molecular datasets and using a molecular clock calibrated against the fossil record, we show that (i) the divergence of the two major scleractinian clades, Robust and Complex corals, took place about 100 My earlier than previously thought, and (ii) that two families of deep-sea corals, the Gardineriidae and Micrabaciidae, diverged much earlier at around 425 My pushing the evolutionary origin of scleractinian corals deep into the Paleozoic.

The early divergence and distinctive morphologies of the extant gardineriid and micrabaciid corals, suggest a link with Ordovician “scleractiniamorph” fossils that were previously assumed to represent extinct anthozoan skeletonized lineages. Therefore, corals most likely evolved from Paleozoic soft-bodied ancestors and modern shallow-water Scleractinia, which are dependent on symbionts, appear to have had several independent origins from solitary, non-symbiotic precursors.