SPINY TRILOBITES
Some polymeroid trilobites evolved extremely spinose
bodies, especially odontopleurids and some lichids. Examples of spinose
odontopleurid and spinose lichid trilobites are shown below.
Ceratarges spinosus from the AM Limestone (Middle Devonian) in southern
Morocco (FMNH PE 60826, Field Museum of Natural History, Chicago, Illinois,
USA). This complete exoskeleton has eight prominent spines. It has
two pairs of long, curving cephalic (head) spines - one pair of genal (cheek)
spines and one pair extending from the glabella. The eyes are perched
atop a pair of stalks that extend posteriorly upward. The pygidium (tail)
also has two pairs of long, curving spines - one pair from the anterolateral
corners and one pair extending from the posterior pygidial margin, straddling
the axis. Series of smaller, straight spines are present between the larger
pygidial spine pairs.
Classification: Animalia, Arthropoda, Trilobita, Polymerida,
Lichidae, Trochurinae
Dicranurus hamatus elegantus (Campbell, 1977) from the Haragan Formation (lower
Lower Devonian) in Coal County, southeastern Oklahoma, USA (FMNH PE 60440,
Field Museum of Natural History, Chicago, Illinois, USA). Dicranurus
has a pair of thin, long, curvilinear genal spines and a moderately robust pair
of strongly curved occipital spines. In lateral view, the occipital
spines appear coiled, like a ram's horns. The thorax has a series of
pleural spines that trend posteriorly to being longer and more strongly bent
backward. The pygidium (tail) is small and has one pair of moderately
short spines.
Classification: Animalia, Arthropoda, Trilobite, Polymerida,
Odontopleurida, Odontopleuridae
Isoprusia tafilaltana Alberti, 1976 (often referred to by its junior
synonym Koneprusia brutoni Alberti, 1983) from the lower Hamar Laghdad
Formation (middle Lower Devonian) at Tafilalt, southeastern Morocco (FMNH PE
60833, Field Museum of Natural History, Chicago, Illinois, USA).
Classification: Animalia, Arthropoda, Trilobita, Polymerida,
Odontopleurida, Odontopleuridae, Koneprusiinae