Found this on another site:
The galaxies, each only 5,000 light-years across, are a fraction of the size of today's "grownup" galaxies but contain approximately the same number of stars. Each could fit inside the central hub of the Milky Way. "These ultra-dense galaxies, forming the building blocks of today's largest galaxies, might comprise half of all galaxies of that mass at this early time," van Dokkum said.
Having read this and also the latest on the globular star clusters, could there be a link? Could a star cluster be an early galaxy forming? Food for thought...