Weejasperaspididae

Weejasperaspididae ("Shields of Wee Jasper") is a family of three extinct acanthothoracid placoderm species indigenous to the Early Devonian "Taemas-Wee Jasper" reef off the southeastern coast of Gondwanaland, located near what is now the town of Wee Jasper, in New South Wales, Australia.

Description

As with other acanthothoracids, the weejasperaspids were heavily armored, with a pair of spines that emanated from their chests, and had a large spine emanating from the top of their backs. They had blunt snouts, and are suspected of being shellfish eaters.

Evolutionary Relationships

The main reasons why the weejasperaspids are not considered to be closely related to other non-acanthothoracid placoderms, as opposed to the palaeacanthaspids, are that their skull anatomies and plate histologies are generalized, and do not bear any similarities to any specific non-acanthothoracid group, and that the patterns of ornamentation on their dermal plates are unique to this family.

The placoderm Brindabellaspis stensioi was once regarded as a weejasperaspid because of the similarities between its armor and dermal plates to the other weejasperaspids. Even before it was split off into its own order, it stood out from the others because of its long, pointed snout. French paleontologist Phillipe Janvier placed B. stensioi in its own order, Brindabellaspida, because of how the internal anatomy of the braincase resembled more like those of osteostracans or galeaspids than those of other placoderms.

External links

Mikko's Phylogeny Archive [1]

References

• Janvier, Philippe. Early Vertebrates Oxford, New York: Oxford University Press, 1998. ISBN 0-19-854047-7
• Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. ISBN 0-8018-5438-5