Ammonoid atau ammonites?

Ammonoid (cephalopoda) adalah salah satu hidupan laut yang paling berjaya dalam perkembangannya serta mempunyai kaitan dengan sotong kurita, sotong-sotong dan nautilus. Ahli paleontologi perlu membezakan ammonoid dan ammonites dengan teliti. Ammonoid wujud dari Zaman Devonian Awal sehingga penghujung Zaman Kapur atau kira-kira dari 400 ke 66 juta tahun lampau. Ammonites adalah suborder kepada ammonoid yang bermula dari Zaman Jurasik antara 200 ke 150 juta tahun dahulu.

Ammonoid mempunyai cangkerang berpilin. Jasad yang hidup tinggal di bahagian kebuk kehidupan iaitu pada penghujung kebuk yang terbesar. Ammonites boleh membesar sehingga mencapai diameter satu meter. Semasa Jurasik dan Kapur, ammonoites telah mengalami kepelbagaian kepada banyak spesies-spesies yang berbeza, yang dibezakan melalui bentuk garis sutur yang komplek. Ini ada hubungan dengan kesesuaian atau adapatasi terhadap persekitaran pada masa itu demi kelangsungan spesies itu terus membiak.

Kesemua ammonoid telah pupus pada detik kepupusan massa Kapur yang pada masa yang sama pupus bersama dinasor-dinasor.

Ammonoids were a very successful order of sea creatures (Ammonoidea) among the cephalopods, related to the octopuses, squids and nautilus. Paleontologists are careful to distinguish the ammonoids from the ammonites. Ammonoids lived from Early Devonian times until the end of the Cretaceous Period, or from about 400 million to 66 million years ago. Ammonites were a suborder of ammonoid with heavy, ornamented shells that thrived starting in the Jurassic Period, between 200 and 150 million year ago.

Ammonoids have a coiled, chambered shell that lies flat, unlike gastropod shells. The animal lived at the end of the shell in the largest chamber. The ammonites grew as large as a meter across. In the wide, warm seas of the Jurassic and Cretaceous, ammonites diversified into many different species, largely distinguished by the intricate shapes of the suture between their shell chambers. It is suggested that this ornamentation served as an aid to mating with the right species. That would not help the organism survive, but by ensuring reproduction it would keep the species alive.

All the ammonoids died at the end of the Cretaceous in the same mass extinction that killed off the dinosaurs.