Complex sentence: Some Equisetopsida were large trees reaching to 30 meters tall; the genus "Calamites" of family Calamitaceae for example is abundant in coal deposits from the Carboniferous period.
Split into simpler sentences: Some Equisetopsida were large trees reaching to 30 meters tall. The genus "Calamites" of the family Calamitaceae, for example, is abundant in coal deposits from the Carboniferous period.