Complex sentence: Long-eared scaly-tailed flying squirrels are about 20cm long and weigh 30g, but not much else is known about them because they are very hard to keep alive in captivity.
Split into simpler sentences: Long-eared scaly-tailed flying squirrels are about 20cm long and weigh 30g. Not much is known about them because they are very hard to keep alive in captivity.