| | Trilobite Facial Suture Types |
 | | Facial sutures once played a primary role in defining family-level relationships, and several common patterns within the three types above were named according to the families that bore the suture pattern. |
 | | Because it is difficult sometimes to envision the nature of the dorsal and ventral sutures, and how they partition the cephalon, I have developed images below that show the sutures in an intact and a disarticulated cephalon of representative trilobites, including ones with large to small rostral plates, and one lacking a rostral plate. |
 | | Note that in species with conterminant hypostomes (ones attached firmly to the anterior boublure), the hypostome may either have well-developed sutures, or may be permanently atached to the rostral plate. |
| www.trilobites.info /sutures.htm (939 words) |