Smaller than a Microraptor!

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Scientific classification

Pravitoceras is an ammonite from the Late Cretaceous of Japan.

The final new for 2021 CollectA figure is this spectacular model of the Late Cretaceous heteromorph ammonite Pravitoceras.  This colourful model extends the number of invertebrates featured in the CollectA range following the introduction of a horseshoe crab, Orthoceras, a belemnite, a trilobite, the nautilus (N. pompilius) and an ammonite with a regularly coiled shell – Pleuroceras, in 2020.

Whilst members of the public might be quite familiar with those types of ammonites with tightly coiled shells, as epitomised by the CollectA Pleuroceras (an example of a homomorph shell), in the Late Jurassic a number of new types of marine cephalopod began to appear in the fossil record with varying degrees of uncoiled shells.  These ammonites became increasingly abundant during the Cretaceous and by the Late Cretaceous they were widespread and extremely diverse with a myriad of different types of shell.  So numerous were these ammonites, that just like their coiled relatives, many genera have become important zonal fossils assisting with the relative dating of strata.

Unlike some of the more bizarre shells of other heteromorphic ammonites, the final shell coil of Pravitoceras forms a distinctive “S” shape and the body chamber is folded back on itself to form a retroversal hook.  Pravitoceras would have been able to swim with a minimal amount of drag due to its shell shape, whereas other more irregularly coiled ammonites with much more complicated shell configurations would have been encumbered by their shells when attempting to swim.

Palaeontologists speculate that these types of ammonites were either entirely epifaunal (dwelling on the sea floor), perhaps scavenging or hunting slow moving animals such as bivalves or snails, or they floated passively in the water column, like many types of extant jellyfish, feeding on zooplankton.


ColelctA 2021 Pravitoceras model