Does the galGal5 chicken assembly have a chromosome 29? The chromosome sizes at UCSC don't seem to contain chr29:

ftp://hgdownload.soe.ucsc.edu/goldenPath/galGal5/bigZips/galGal5.chrom.sizes

It has a chr28 and a chr30. Am I missing something or is there some piece of history that led to the omission of this chromosome?
The current ensembl entry doesn't have a 29 either.  The archived ensembl assembly  lacks 29 30, and 31 and 33 and LGE64.

The chromosomes after 30 are tiny, so they might not be visible in a karyotype.  They probably realized that "chr 29" was really attached to some other chromosome.