Mazon Creek - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 119

Insects
Six orders of insects occur at Mazon
Creek, all of which are now extinct. Much
of our knowledge of Pennsylvanian
insects comes from the 150 species
found in Mazon Creek nodules.
Palaeodictyoptera were medium to giant
flying forms with patterned wings
and comprised half of all known
Paleozoic insects. Both nymphs and
adults were terrestrial and had
sucking mouthparts. Megasecoptera were
similar to Palaeodictyoptera but had
more slender, often petiolated (stalked)
wings. Diaphanopterodea resembled
Megasecoptera with the one exception
that they could fold their wings over their
backs like modern butterflies and
damselflies do. Protodonata, as their
name suggests, were distantly related to
modern Odonata (dragonflies and
damselflies). Some reached giant
proportions in the Pennsylvanian and
Permian, with wingspans of 710 mm
(28 in). It is presumed that, like Odonata,
the nymphs led an aquatic life, but none
have been found.
'Protorthoptera' is a general name
given to a large group of Paleozoic insects
which resemble the modern Orthoptera
(grasshoppers, katydids, locusts, and
crickets) but lacked jumping legs. They
form the stem-group which gave rise
to modern Orthoptera, Dermaptera
(earwigs), Phasmatodea (mantids), and
some other extinct and living orders.
Twelve families occur at Mazon Creek, and
Gerarus is the commonest insect fossil
found there. Gerarus belongs to the group
which is thought to have given rise to the
giant Triassic Titanoptera, now extinct.
It was once thought that the familiar
roaches occurred in rocks as old as
Pennsylvanian because of the abundant
remains of roach-like animals in
Pennsylvanian nodules. However, it has
now been shown that these animals
possess some rather primitive traits, such
as a large external ovipositor which
evolved even before the origin of flight, so
these stem-group Dictyoptera are better

described as 'roachoids' or Blattodea
(Grimaldi and Engel, 2005). In the
nodules from Mazon Creek ( 123 ) their
veined wings are often mistaken for seed-
fern pinnules.

Myriapods
Myriapods are multilegged arthropods
which include the centipedes
(Chilopoda), millipedes (Diplopoda), two
other living classes (Symphyla and
Pauropoda), and the Paleozoic
Arthropleurida. Myriapods were among the
earliest known land animals (Chapter 6),
but by Pennsylvanian times some had
become gigantic, and many sported fierce
spines, presumably for defence against
predators. Short millipedes which could
roll up into a ball (Oniscomorpha:
Amynilyspes ) were present in the
Braidwood biota, but the most dramatic
forms belong to the extinct order
Euphoberiida. Myriacantherpestes ( 124 )
probably reached around 30 cm (1 ft) in
length and had long, forked, lateral spines
and shorter dorsal spines. Xyloiulus ( 125 )
was a more typical, cylindrical, spirobolid
millipede. Millipedes are generally
detritus feeders, while centipedes are
carnivorous.
Centipedes at Mazon Creek include
the scolopendromorph Mazoscolopendra
and the fast-running scutigeromorph
Latzelia . Arthropleurids range from tiny
forms in the Silurian to the Pennsyl-
vanian, when they became the largest
known terrestrial animals, reaching 2 m
(6.6 ft) in length. Nevertheless, like
millipedes, they were probably detritus-
feeders. Isolated legs and plates of
Arthropleura occur at Mazon Creek.
Onychophora (velvet worms) should also
be mentioned here. They are known from
the Cambrian (e.g. Aysheaia , Chapter 3),
when they were marine, to the Recent,
when they are wholly terrestrial. The
Mazon Creek Ilyodes was collected from
natural outcrops and it is not known
whether it came from the terrestrial
Braidwood or marine Essex biota.