For worlds famous gill breathers there are three hip
around- kinds of hanging about their marine medium:
drifting around, swimming around and
crawling around ;-)))
According to this, Trilobites biotic communities are to be shown as
So this can be assumed, representatives of the Order
Agnostida led a planktonic mode of life, i. e. floating with drift (passive)
inside the plankton. One biotic indices concerning this mode of life is the wide
global distribution of a big number of fossil Agnostides within a very short-
time geological period. Amongst the active natant trilobites (nekton), according
to the body shapes (elongate, streamlined body shapes in opposite to broad
shapes) there must have been trilobites with more or less good swimming
Aside from body structures pelagic living trilobites are to
be distinguished from their benthic relatives with the eyes. Swimmers of the
pelagic water column had big eyes relative to cephalons size, with lenses
arrayed the patterns (quantity and adjustment), guaranting nearly an all-round
sight. On the other hand the eyes of trilobites moving through a benthic layer
were designed for a primary upwards- (e.g. detection of predators) and
lateral visual field.
With regard to their feeding habits, trilobites are comparable to their recent
relatives, the Crustacea. According to this, they are classified to predators,
filter feeders and particle feeders (endogeic).
Predators typically possessed spines (sometimes even fang- like) at their upper
ventral appendages (gnathobase to fix the prey, or transporting
the prey forward by using the gnathobases of the anterior limbs, and finally
slashing the prey by their special distincted Hypostoma. Another arbitrary
indication for a predatory way of life was a great inflated Glabella, housing an
appropriately big stomach for initial processing of large chunks of prey.
Filter feeders shared a big vaulted cephalon considerably
developed more convex in opposite to the remaining body. Below this cephalon
there was a cavern, filling it with sediment by the use of anterior spine, rows
of pits or by paddling with the legs. By use of a respective species- specific
designed "filter- system" the nutritious contents were seperated from "waste"
As a rule endogeic trilobites had many
thoragic segments (appropriate number of pairs of legs for rooting), a
relatively small glabella and a 'flexible'
hypostome (natant condition) for
strongly digging up the sediment.