Complex sentence: Of the 621 spider species known to occur in his native Utah, Chamberlin described or co-described more than a third, and became a leading expert in North American tarantulas; describing over 60 species.
Split into simpler sentences: Of the 621 spider species known to occur in his native Utah, Chamberlin described or co-described more than a third. Chamberlin was also a leading expert in North American tarantulas; describing over 60 species.