Galeaspida

Galeaspida Temporal range: Llandovery[1]–Early Devonian, 438–400 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	†Galeaspida Liu, 1965
Orders
Eugaleaspidiformes Liu, 1965 Huananaspidiformes Janvier, 1975 Polybranchiaspidiformes Janvier, 1996

Galeaspida (from Latin, 'Helmet shields') is an extinct taxon of jawless marine and freshwater fish. The name is derived from galea, the Latin word for helmet, and refers to their massive bone shield on the head. Galeaspida lived in shallow, fresh water and marine environments during the Silurian and Devonian times (430 to 370 million years ago) in what is now Southern China, Tibet and Vietnam. Superficially, their morphology appears more similar to that of Heterostraci than Osteostraci, there being currently no evidence that the galeaspids had paired fins.^{[citation needed]} A galeaspid Tujiaaspis vividus from the Silurian period of China was described in 2022 as having a precursor condition to the form of paired fins seen in Osteostraci and gnathostomes.^[2] Earlier than this, Galeaspida were already in fact regarded as being more closely related to Osteostraci, based on the closer similarity of the morphology of the braincase.^{[citation needed]}