Miragaia longicollum

Lore & Background

A partial pelvis and vertebrae from a juvenile (specimen ML 433-A) found at the same location were assigned as a paratype. Francisco Costa described five probable dacentrurine specimens from the Morrison Formation (Wyoming and Utah), assigning one to cf. M. longicollum and three to Miragaia sp. The neck elongation of Miragaia appears to have resulted mostly from back vertebrae becoming incorporated into the neck, rather than addition of new vertebrae. The authors suggested the long neck may have allowed browsing at a level not exploited by other herbivores, or could have arisen due to sexual selection, though the feeding function makes sexual selection less plausible.

Reader's Guide

Miragaia longicollum is significant for demonstrating that stegosaurians could evolve extremely long necks, challenging the traditional view of them as low browsers with short necks. With at least seventeen cervical vertebrae, it had more neck vertebrae than most sauropods, paralleling only a few Chinese sauropod genera. The discovery also provides the first cranial material for a European stegosaurid. However, the genus's validity is disputed: some researchers consider Miragaia a junior synonym of Dacentrurus, while others argue it is a valid taxon. This taxonomic debate, ongoing as of 2025, reflects the difficulty of comparing incomplete holotypes. The possible presence of Miragaia in North America, suggested by 2026 work, would extend its geographic range. Histological study of the holotype indicates sexual maturity at 14–15 years and skeletal maturity at 21–25 years, offering insights into stegosaur growth.

Did You Know?

• Miragaia has the longest neck known for any stegosaurian, with at least seventeen vertebrae.
• The holotype was found after road construction between the villages of Miragaia and Sobral, Portugal.
• The specific name 'longicollum' means 'long neck' from Latin.