Prolecanitida

Early Carboniferous through the End Triassic

360 to 200 million years ago

Diversity, Geographic Range and Habitat

• This order of Ammonites was more diverse than the Clymeniida

Characteristics

Shell Structure

• Early Prolecanitida had both evolute and involute shells and were not as flattened (or disc-shaped) as the later groups
• Later Prolecanitida possess only involute shells which were more disc-shaped than the other paleoammonoids
• Ventral edge is comes to a sharp edge unlike other paleoammonoids whose ventral edge could be rounded or even somewhat flattened
  • This feature adds to the disc-like appearance of the shell
  • Some paleontologists think that this shape may have enhanced the animals swimming abilities allowing it to slice through the water.

Siphuncle

• Ventral

Septal Neck

• Prochoanitic (points forwards, towards the body chamber)

Suture Lines

• Their sutures resembled those of the Goniatites
• Suture lines were complex with several lobes and saddles
  • Saddles were rounded
  • Lobes were divided into sections like splayed fingers
  • Such sutures were characteristic of advanced paleoammonoids.
• Seen in some goniatites
• Also typical of ceratites
• All had umbilical lobes as well as the usual external and internal lobes
  • The umbilical lobe appeared as the ammonite grew

Ornamentation

• Shell surface smooth and weakly ornamented with ribs
• No lappets