TO THE ORDER PHACOPIDA
last revised 16 October 2005 by S. M. Gon III
ORDER PHACOPIDA
Compare the above pictorial approach to the narrative description
(pictorial features highlighted above are boldfaced
green below):
Compare the above pictorial approach to the narrative description
(pictorial features highlighted above are boldfaced
green below):
| ORDER PHACOPIDA
Introduction: large and variable group of related suborders. Cephalon: typically proparian (Phacopina and Cheirurina) or gonatoparian (Calymenina), preglabellar field often very short or absent, 4 or fewer pairs of glabellar furrows (these sometimes fused); eyes, when present, schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina); with rostral plates (Calymenina and Cheirurina) or without (some Phacopina); hypostome conterminant (all suborders) to impendent (some Phacopina). Thorax: 8 – 19 segments, sometimes distinctly furrowed, axis sometimes broad (e.g., Homalonotidae). Pygidium: typically micropygous (most Calymenina and Phacopina), but variable (e.g., subisopygous in Dalmanitoidea and Acastoidea), may be lobed or spiny (e.g., Cheirurina, some Dalmanitoidea, Acastoidea), or smooth-margined, with round or subtriangular outline (e.g., Calymenina, Phacopoidea). Other: All suborders share similar ontogeny (particularly in the protaspides) that in particular link the Calymenina to other Phacopida. Occurrence: Lower Ordovician (Tremadoc) to Upper Devonian (Famennian) Suborders: Calymenina, Phacopina, Cheirurina. |
PHACOPIDA includes three Suborders
| Phacopina
|
Calymenina
|
Cheirurina
|
Walking Trilobite animation ©2000
by S. M. Gon III
All line drawings this page ©1999 - 2005 by
S.
M. Gon III
