[Coral-List] Have massive scleractinians been getting more hardy over geologic time?

Douglas Fenner douglasfennertassi at gmail.com
Fri Dec 18 15:30:32 EST 2015

I'd just like to add that this subject is covered in more detail in Chapter
12 of Dr. Birkeland's new book, "Coral Reefs of the Anthropocene."

On Thu, Dec 17, 2015 at 6:43 PM, Charles Birkeland <charlesb at hawaii.edu>

> Bambach et al. (2004 Paleobiology 30: 522-542) found the overall survival
> of marine genera for both the Triassic/Jurassic and the
> Cretaceous/Paleogene (K-Pg) extinctions to be about 53%. The scleractinian
> genera did much worse than marine life in general in the Triassic/Jurassic
> extinction with about 29%, i.e., 20 out of 69 genera surviving (Lathuilière
> and Marchal 2009 Terra Nova 21: 57-66).   In contrast, according to
> Keissling and Baron-Szabo (2004, Palaeogeography, Palaeoclimatology,
> Palaeoecology 214: 195-223) scleractinians did much better than marine life
> in general in the K – Pg  with 70% scleractinian genera and over half the
> species surviving.  In fact, according to Wells (1956 In: Moore (ed)
> Treatise on Invert paleontology, Part F, Coelenterata. Geol Soc America)
> and Ma (1959) Oceanographica Sinica Special Vol 1) about two dozen of the
> important genera of massive or encrusting corals today were in the
> Cretaceous and have survived the K-Pg, the Paleocene-Eocene Thermal Maximum
> and turnovers of species in the western Atlantic. These genera must be from
> hardy lineages.
> Bambach et al. believe that a part of the problem at the T/J was little
> speciation while the K-Pg was a full-on mass extinction. There were major
> extinctions of many other calcareous organisms in the K-Pg such as
> planktonic foraminifers and coccolithophores and complete extinctions of
> some calcareous molluscs such as rudists and ammonites. This would make the
> relative hardiness of the more recent massive Cretaceous corals even
> greater.
> Most of the coral genera surviving the T/J mass extinction went extinct by
> the end of the Early Jurassic when conditions became very favorable for
> reef-building and 100 new genera appeared (Wood 1999 Reef evolution.
> Oxford).  Once again, the “Lazarus” corals (genera coming back to life
> after the K-Pg extinction) did better. Although some did go extinct when
> the environment became good for reef-building and new genera originated in
> the late Oligocene – early Miocene, a couple-dozen genera of Lazarus corals
> are still important today.
> All this does not seem to apply to fast-growing erect corals which are
> mostly wiped out with each mass extinction. New genera of fast-growing
> corals originate after mass extinctions and become prevalent when the
> environment gets good for reef-building.   For example, in the acroporids,
> the encrusting or somewhat massive *Astreopora* survived the K-Pg mass
> extinction and is still with us, but the branching genera have originated
> in the more recent Paleogene or Neogene.
> So the fossil record suggests that some lineages of the massive and
> encrusting genera might be getting more resistant through time, but the
> fast-growing genera have their 15 minutes (OK, 10s of millions of years) of
> glory when environmental conditions are good, but may be terminated when
> things get tough. Perhaps growing fast has tradeoffs with resistance to
> stress. During the good times of the Neogene, it may have been so rewarding
> to be a fast grower that natural selection disregarded insurance for future
> climate changes as it seems to have done in previous periods.
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Douglas Fenner
Consultant, corals, coral reefs, coral identification
"have regulator, will travel"
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