Description: Sphenolithus species with prominent, apical spines formed from a single element.

Species included: 

	S. heteromorphus - prominent apical spiine, lower and upper cycles of base of similar size	NN4-5
	S. belemnos - dart shaped species, lower cylce of base much larger than upper cycle	NN3
	S. delphix - small species with long apaical spine and basal spines	NN1
	S. calyculus - small species with long apical spine	NN1
	S. capricornutus - small species with two apical spines	NN1

Remarks: S. heteromorphus and S. belemnos are common species and key bostratigraphic markers. S. delphix, S. capricornutus and S. calyculus are a group of relativel rare small species with well developed apical spines charcteristic of the Earliest Miocene.