Complex sentence: Because of the islands' isolation, the St. Kilda House Mouse was larger than the mainland varieties, though it had a number of traits in common with a subspecies found on Mykines island in the Faroe Islands, ("Mus musculus mykinessiensis").
Split into simpler sentences: Because of the islands' isolation, the St Kilda House Mouse was larger than the mainland varieties. It had a number of traits in common with a sub-species found on Mykines island in the Faroe Islands, ("Mus musculus mykinessiensis").