Most [Paleozoic] ammonoids are characterized by a combination curved and angular [suture] pattern, and this type of suture pattern is referred to as goniatitic ([fig. 19]b). Sutures that are curved and crenulated (marked in places by a [series] of tooth-like indentations) are known as ceratitic ([fig. 19]c). Ceratitic sutures first appeared in the [Mississippian], became increasingly abundant during the [Triassic] but were much less abundant during the [Cretaceous]. The ammonitic suture has a very complexly subdivided pattern ([fig. 19]d). Cephalopods with ammonitic sutures range from [Pennsylvanian] to Cretaceous in age and were the most abundant cephalopods of the [Mesozoic].
Plate 32
[PENNSYLVANIAN] CEPHALOPODS
PHANEROCERAS × 1 ORTHOCERAS × 1
[CRETACEOUS] CEPHALOPODS
METOICOCERAS × ½ CYMATOCERAS × ½
Plate 33
[CRETACEOUS] CEPHALOPODS
