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WWD: Pectinatites rarescens
🕑 Added 2023-04-28 06:53:49 +0000 UTCOne of the most successful taxa of the Mesozoic were not merely the reptiles, but the molluscs. During this period evolved some of the very largest cephalopods and bivalves to have ever lived; vast reefs of giant clams up to ten feet across, while octopods larger than adult humans and ammonites weighing over a ton cruised across the shallow seas. Ammonite in particular are one of the era's greatest successes; they dominated the marine ecosystems in such number and diversity that they're used as index fossils for marking the age of rock layers. All the taxa here are those which existed roughly during the Pectinatites pectinatus layer of the Kimmeridge Clay. This species was a much larger close relative, reaching up to half a metre in shell diameter.
Despite the ubiquitousness of ammonites in the global fossil record, their soft anatomy remains obscure since well-preserved soft tissue impressions weren't described until very recently. WWD portrayed ammonites as having an operculum similar to modern aquatic gastropods or the hoods of nautili, but we know now that they did not have them. Their lifestyles are also poorly known, although considering the variety of sizes and shapes, it was probably equally diverse, some being active predators, some being benthic, others pelagic, some filter-feeders, others scavengers.
The episode also portrays ammonites as being an ugly dark brown, as though the fossils depict the true colours of the living animal, which was an ubiquitous portrayal style for a very long time. However, modern marine molluscs come in a spectacular variety of colours and patterns, so there's no reason to think the same wasn't true of prehistoric molluscs. Therefore, the colour scheme is basically re-invented wholesale, only keeping the basic brown shell hue, but changing everything else.
