27 September: Protostome/deuterostome differences, cont.

Trochophore larve vs dipleurula/bipinnaria larvae (lower right of diagram)

Anus at end of body vs post-anal tail

Haemocoel versus distinct circulatory and coelomic components

Storage form of phosphate-Aspartine versus Creatinine phosphate. Later work showed that creatinine phosphate is typical of homeothermic animals and arginine of exotherms.

The Cambrian Explosion--Sudden appearance of many forms containing "harden" body parts. also time of enhanced adaptive radiation. The Burgess shale of British Columbia is the source for many of the creatures. Others have been found in China. Both area have many strange forms, some of which disappeared soon thereafter. Gould's book, Wonderful Life, discusses this question. Gould describes how Walcott, one of the first collectors of the Burgess Shale, tried to pound square pegs in round holes by fitting all the creatures into known phyla. Gould uses the concept of contigency to explain what phyla we have present today.

Discussion of the arthropods--

Tagmatization (regional specialization)