Complex sentence: Lyle Richard Campbell (born 1942) is a linguist considered a foremost expert on Historical Linguistics and on American Indian languages, especially those of Mesoamerica; he also has expertise in Uralic (Finno-Ugric) languages.
Split into simpler sentences: Lyle Richard Campbell (born 1942) is a linguist and leading expert on American Indian languages--especially those of Mesoamerica--and on historical linguistics in general. He also has expertise in Uralic (Finno-Ugric) languages.