At least, worms may have been among the first animals to recolonize the planet after the Cretaceous-Tertiary (K-T) extinction event. Karen Chin and her team from the University of Colorado at Boulder have discovered evidence of worm burrows that may have been made within a few thousand years of the asteroid strike that devastated life on Earth 65 million years ago. The results were presented at the 2011 annual meeting of the Geological Society of America.
Chin and her team found the burrows traveling horizontally through the sediment just inches above the K-T boundary layer. This provided strong evidence that worms were present in abundance, despite the lack of fossilized tissue. As much of the plant life on Earth would have been obliterated by the nuclear winter caused by the asteroid crash, some researchers speculate that many surviving animals subsisted on decomposing organic materials rather than on living plants and animals. This may have been an ideal substrate for worms, which in turn would have been welcome fair for other animals.
By the way, geologists now frown on using the term ‘Tertiary’ for this boundary. For that reason, you may see this event abbreviated as ‘K-Pg’ for ‘Cretaceous-Paleogene’. As to why Cretaceous is abbreviated with a ‘K’, you can thank the Germans for calling that time period ‘Kreidezeit’ after the word ‘kreide’ meaning ‘chalk’.