Friday Cephalopod: Survivor: Cephalopod!

Tips for flourishing after a mass extinction. Ceratites nodosus (MCZ-7232) (A), from the Triassic of Germany, was similar to the ceratitid ammonoid species that thrived in the water column in the Early Triassic (1), while bottom-dwelling species languished. Key to the ceratitids’ rapid success after the end-Permian mass extinction were their ecological tolerances, which may be inferred by reference to their closest living relatives, the coleoids (squids, octopuses, and cuttlefish), including the low-oxygen specialist Vampyroteuthis infernalis (B).

This picture has a little story behind it. Over 250 million years ago, our world experienced the most massive extinction event known, with over 99% of all individuals on the planet dying out abruptly, and diversity was greatly limited for a few million years after that. One possible explanation for the Permian extinction is a correlated series of massive volcanic eruptions that burned through thick coal deposits and drowned the earth in CO2 — global warming on a massive scale. Even cephalopods suffered. The ceratatid ammonoids had been in decline for a long time, but the extinction nearly wiped them out, reducing them to only a few struggling genera.

But then something interesting happened. After the great extinction, the ammonoids exploded in diversity, radiating rapidly. Something about them had made some of them capable of riding out the disaster, and then exploiting the changed world afterwards.

(Click for larger image)

Total generic richness [Sobs; black bold line,
all ammonoids; gray lines, major ammonoid groups;
Permian dotted line, alternate data from Ammon
(16)] and mean Chao2 estimate of the overall generic
richness with its 95% confidence interval (large circles
with vertical bars) (table S1). PTB, Permian-Triassic
boundary; 1, Kasimovian; 2, Gzhelian; 3, Asselian; 4,
Sakmarian; 5, Artinskian; 6, Kungurian; 7, Roadian; 8,
Wordian; 9, Capitanian; 10, Wuchiapingian; unlabeled
successive intervals, Changhsingian, Griesbachian,
Dienerian, Smithian; 15, Spathian; 16, Early Anisian;
17, Middle Anisian; 18, Late Anisian; 19, Ladinian; 20,
Early Carnian; 21, Late Carnian; 22, Early Norian; 23,
Middle Norian; 24, Late Norian; 25, Rhaetian.

One speculative explanation for the secret of their success is the ability of some members of the cephalopod clade to survive in cold, nearly anoxic conditions, like Vampyroteuthis infernalis. They were able to rebound quickly because of their dismal metabolism and the general fecundity of cephalopods. They restored some ecological webs faster than previously thought and provided an environment for further growth of more severely crippled clades.

It just goes to show you that our current episode of global warming is a relatively minor event. Life will go on. Fast-living organisms with high metabolic demands like, say, humans, might suffer and die from the environmental consequences of a high CO2 atmosphere, but don’t worry — the cephalopods will live on. They might even get a happy surge in numbers from the changes.

Brayard A, Escarguel G, Bucher H, Monnet C, Brühwiler T, Goudemand N, Galfetti T, Guex J (2009) Good Genes and Good Luck: Ammonoid Diversity and the End-Permian Mass Extinction. Science 325(5944):1118-1121.

Marshall CR, Jacobs DK (2009) Flourishing After the End-Permian Mass Extinction. Science 325(5944):1079-1080.