Umoonasaurus demoscyllus

Overview

Umoonasaurus demoscyllus is an Early Cretaceous plesiosaur from Australia. Its small head and distinctive skull ridges provide research clues. Introduced through research on opalized fossils, it also attracts attention for its preservation.^[1]

Key facts

The ridges on the skull are features used to recognize this animal. Distinctive ridges are described above its small head and short snout. Looking for bony structures on the head rather than only the broad body outline makes comparisons with other plesiosaurs intriguing.^[1]

Time and place

It is studied from Early Cretaceous material in present-day Australia. The 2006 paper addressed its background as an opalized fossil from a region then at high latitude. The Cretaceous was roughly 140–66 million years ago.^[1][2]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The adult type specimen AM F99374 preserves the skull together with the body skeleton. The small head, short snout, and skull ridges are important features. Neck and tail vertebrae and limb bones also reveal the body’s construction.^[1]

Umoonasaurus is described as reaching a maximum body length of about 2.5m. The opalized specimen AM F99374, nicknamed “Eric,” is an important clue for estimating this small plesiosaur’s size.^[3]

Habitat and reproduction

A plesiosaur’s four fins can be viewed as modified forelimbs and hind limbs. Research on Umoonasaurus addresses several regions of the head, neck, limbs, and tail. The distinctive head ridges can be compared alongside the body construction of a marine reptile.^[1]

Fossil discovery

The 2006 study described this animal from the associated skull and body skeleton of AM F99374. It examined unusual head ridges and skeletal features in opalized material. Preservation and anatomy together add interest to this fossil.^[1]

References

1. Kear et al. (2006) — Umoonasaurus preserved in opal
2. International Commission on Stratigraphy (2024) — Geological time chart
3. Kear et al. (2006) — Original description of Umoonasaurus
4. 2026 study — A thermal model of Albertonectes
5. Kubo·Mitchell·Henderson (2012) — A new elasmosaurid from Alberta

Research questions

How do the ridges on the small head differ from those of other plesiosaurs? Several features of the head bones, neck, limbs, and tail are compared together. This research explores relationships by examining one distinctive region alongside the construction of the whole body.^[1]

Observation

Move your gaze from the small head and short snout to the skull ridges. Then follow the body outline through the forefins, hind fins, and tail to reveal both the head features and the plesiosaur body construction.^[1]