Tujiaaspis vividus
Name: Tujiaaspis vividus [Vigorous Tujia shield]
When: Early Silurian Period, 443 - 423 million years ago
Where: Xiushan County, Chongqing, China
Claim to fame: Tujiaaspis belongs to the group Galeaspida, enigmatic creatures whose entire existence was limited to the Silurian and Early Devonian of what would become China. All galeaspids are interesting for being the first vertebrates to possess ossified internal bone along with bony armor plates and scales on their body surfaces. This allows us to see details of their internal anatomy that would otherwise be mysterious. So what do we see? Galeaspids are jawless vertebrates, but have interesting internal features including:
- A large opening on the front of the face that communicated with paired olfactory capsules and the pharynx. In contrast, more primitive vertebrates like lampreys and Pharyngolepis had one nostril connected to one olfactory capsule, and jawed vertebrates have paired nostrils connected to paired olfactory capsules but not to the pharynx.
- An astonishing number of gill arches - up to 40 pairs.
Unfortunately most galeaspids are known only from their head shield skeleton. That's where Tujiaaspis comes in. Tujiaaspis preserves the galeaspid trunk and tail skeleton with unprecedented detail, showing three dorsal fins and paired folds running dow its flanks - not quite paired fins, but trending in that direction. Digital analyses show that this creature, despite its large head and flat profile, was actually a fast swimmer among Silurian vertebrates.