An integrated approach has been used to assess the palaeoecology of gr
aptolites, both as a discrete group and as a part of the biota present
within Ordovician and Silurian planktic realms. Study of the function
al morphology of graptolites and comparisons with Recent ecological an
alogues demonstrates that graptolites most probably filled a variety o
f niches as primary consumers, with modes of life related to the colon
y morphotype. Graptolite coloniality was extremely ordered, lacking an
y close morphological analogues in Recent faunas. To obtain maximum fu
nctional efficiency, graptolites would have needed varying degrees of
coordinated automobility. A change in lifestyle related to ontogenetic
changes was prevalent within many graptolite groups. Differing lifest
yle was reflected by differing reproductive strategies, with synrhabdo
somes most likely being a method for rapid asexual reproduction. Direc
t evidence in the form of graptolithophage 'coprolitic' bodies, as wel
l as indirect evidence in the form of probable defensive adaptations,
indicate that graptolites comprised a food item for a variety of preda
tors. Graptolites were also hosts to a variety of parasitic organisms
and provided an important nutrient source for scavenging organisms.