Sphenodiscus

## SphenodiscusWedge Disc

### Temporal Range

83.5 - 64.5 million years ago, Campanian - Danian Stage, Late Cretaceous - Early Paleocene Period

### Episodes

* Oceans (Segment 5)
* North America (Segment 2)
* What Do We Really Know About Ammonites?

## Characteristics

### Diet

Carnivore

***Sphenodiscus*** (Wedge Disc), also called ***tiger ammonites*** on the show, is an extinct genus of sphenodiscid ammonite cephalopod that lived in North America, South America, Europe, Asia and Africa, around 83.5 - 64.5 million years ago, from the Campanian stage of the Late Cretaceous Period to the Danian Stage of the Early Paleocene Period.

It is unknown which specific species was depicted on Prehistoric Planet. The species featured in the fifth segment of Oceans (set within the Tethys Ocean) may be *S. binkhorsti* of the Netherlands or some other European species, while the species featured in the second segment of North America (set in the Western Interior Seaway) may be any of the common species found in North America, like *S. lobatus*, *S. lenticularis*, *S. pleurisepta*, etc.

## Description

***“ Tiger ammonites are themselves hunters. The combination of a streamlined profile and a powerful siphon enables them to shoot through water at great speed. But so can the mosasaur. ”***

― **David Attenborough**, *North America*
TBA

## Habitat

As shown on Prehistoric Planet, *Sphenodiscus* thrived in the warm, shallow waters of the Gulf of Mexico, which was, by that time, part of the Western Interior Seaway, an inland sea that split North America into two landmasses (Laramidia in the west and Appalachia in the east). It was also present in similar seas across the globe, thriving in the waters of Trinidad and Brazil in South America, the Netherlands in Europe, Nigeria in Africa, and India (which by that time was an island isolated from the rest of Asia).

## Appearances

### Oceans

In the fifth segment of Oceans, several *Sphenodiscus* briefly appear alongside other ammonites in a seagrass meadow in the Tethys Ocean.

### North America

In the second segment of North America, in the Gulf of Mexico, a *Globidens* seeks out shoals of "tiger ammonites", *Sphenodiscus*. Every year, from the deep levels of the ocean, thousands of females come up to the coast, each ammonite carrying hundreds of fertilized eggs that need to be laid in the shallows, right where *Globidens* is waiting for them.

The *Sphenodiscus* use their own predatory traits (their streamlined profile and powerful siphon) to get to their destination faster and evade incoming threats. Unfortunately for them, *Globidens* is also quick enough to catch up to them and attack. With its globular teeth, the mosasaur easily crunches through the shells of the ammonites, releasing the buoyant air within its prey, disabling and sinking as many *Sphenodiscus* as it can instead of taking time to consume each ammonite it catches. Once the shoals of ammonites have passed through the area, with no more prey to cripple, *Globidens* feeds on the ammonites it sunk to the ocean floor. Despite the mosasaur having killed dozens of the ammonites, hundreds more make it to the shallows to successfully lay their eggs.

### What Do We Really Know About Ammonites?

  **What Do We Really Know About Ammonites?**
**Subject**
Various facts and knowledge about ammonites.

**Experts**
Dr. Darren Naish, Zoe Hughes
TBA