Prolecanitida
Prolecanitida Temporal range:
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Protocanites, a Tournaisian prolecanitoid in the family Prolecanitidae | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Mollusca |
Class: | Cephalopoda |
Subclass: | †Ammonoidea |
Order: | †Prolecanitida Miller & Furnish, 1954 |
Superfamilies | |
Prolecanitida is an order of extinct
Prolecanitids form a relatively small and stable order within the Ammonoidea, with 43 named genera and about 1250 species. They were a long-ranging lineage, surviving for about 108 m.y. stretching from the Devonian–Carboniferous boundary to the Early Triassic. Although not as diverse as their goniatitid contemporaries, the Prolecanatida provided the stock from which all later Mesozoic ammonoids were derived.
Most prolecanitids had
Evolution and phylogeny
The origin of the Prolecanitida may be found in the
The oldest known prolecanitids were the family Prolecanitidae, which appeared around the Devonian–Carboniferous boundary and diversified in the Tournaisian stage. One of the most basal members of the order was Protocanites, which has been (likely erroneously)[1] reported from the latest Devonian Louisiana Limestone of Missouri.[2] The prolecanitoid family Daraelitidae is the probable source for the order Ceratitida, beginning with the family Xenodiscidae in the Middle Permian. Not counting their ceratite descendants, the youngest known prolecanitids were Episageceras and Latisageceras, two Early Triassic medlicottioid genera in the subfamily Episageceratinae.
Prolecanitids showed long-term, gradual changes in shell geometry. Likewise, they utilized a more limited set of available forms (a smaller morphospace) as compared to the dominant goniatitids. Prolecanitid genera averaged 14.7 million years in duration, as compared to 5.7 million years for Upper Carboniferous goniatitids.[3]
Suture morphology in the Prolecanitida changed dramatically over time, from very simple sutures in the earliest genera to much more complex-sutured genera in the late Paleozoic. The increase in suture complexity over the 108 m.y. duration resulted from the iterative of addition of umbilical lobes, increasing serration of lobes, and the subdivision of lateral and ventral lobes. As many as 12–15 replicate, U-shaped umbilical lobes were added to the sutures during both ontogeny and phylogeny, originating at the umbilicus and migrating outward across the flanks.
Suture patterns in Prolecanitida evolved differently than in the Goniatitda, by increasing the number of umbilical lobes rather than by subdivision of the lateral saddle. Moreover, the body chamber in Prolecanitida was comparatively short, taking up only about half of the largest whorl. This complicates the question of the relationship between the Goniatitida and the Prolecanitida and their Mesozoic descendants.
References
- Furnish, William M.; Glenister, Brian F.; Kullmann, Jürgen; Zhuren, Zhou (2009). Selden, Paul A. (ed.). Part L, Mollusca 4 (Revised). Volume 2: Carboniferous and Permian Ammonoidea (Goniatitida and Prolecanitida). ISBN 1-891276-61-1.
- Miller, Furnish, and Schindewolf, 1957; Paleozoic Ammonoidea, Suborder Prolecanitina, L69, in The Treatise on Invertebrate Paleontology, Part L, Ammonoidea.
- Species and Genus Level Evolution in the Fossil Record [1]