Complex sentence: The tammar wallaby was the second marsupial to have its genome sequenced, after the gray short-tailed opossum and the first Australian marsupial to be sequenced (although it was the second published).
Split into simpler sentences: The tammar wallaby was the second marsupial to have its genome sequenced, after the gray short-tailed opossum. It was the first Australian marsupial to be sequenced (although it was the second published).