Misplaced Pages

Zenaspidida
Fossil of Zenaspis powriei
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Osteostraci
Order:	†Zenaspidida Stensiö, 1958
Subgroups
†Spangenhelmaspis †Wladysagitta †Parameteoraspididae †Superciliaspididae †Scolenaspididae †Zenaspididae
Synonyms
Zenaspida

Zenaspidida is an extinct order of osteostracans, a group of jawless stem-gnathostomes. They possessed a distinct headshield, which varied in width to length ratio by species.

Description

The head shield is dome-shaped and extremely large in comparison to the main body. The abdominal section of this shield has a less developed median dorsal crest. As a rule for this order, the nasohypophysial opening is larger than the nasal division. The pineal plate seen in other osteostracans is barely developed or completely absent. The median dorsal field is notably broad, and the lateral fields are widened in the posterior, but reach back no further than the proximal section of the dorsal surface of the cornual processes. The ornamentation on the head shield can have singular, large tubercles, or groups of tubercles which range in size. This is often used to speciate.

Classification

The cladogram below is adapted from a 2014 article by Scott and Wilson:

References

1. Scott, B. R.; Wilson, M. V. H. (2013). "A new species of osteostracan from the Lochkovian (Early Devonian) of the Mackenzie Mountains, with comments on body size, growth, and geographic distribution in the genus Machairaspis". Canadian Journal of Earth Sciences. 50 (2): 127–134. doi:10.1139/cjes-2012-0100.
2. Voichyshyn, V. (2006). "New osteostracans from the Lower Devonian terrigenousdeposits of Podolia, Ukraine". Acta Palaeontologica Polonica. 51: 131–142 – via ResearchGate.
3. Voichyshyn, V. (2011). "THE EARLY DEVONIAN ARMOURED AGNATHANS OF PODOLIA, UKRAINE" (PDF). Palaeontologia Polonica. 66. Archived from the original (PDF) on February 14, 2023.
4. Scott, B. R.; Wilson, M. V. H. (2015). "The Superciliaspididae, a new family of Early Devonian Osteostraci (jawless vertebrates) from northern Canada, with two new genera and three new species". Journal of Systematic Palaeontology. 13 (3): 167–187. doi:10.1080/14772019.2013.863809.

External links

• "Zenaspidida". The Encyclopedia of Life.
• "Agnatha". paleofile.com. Archived from the original on April 10, 2021.

v t e Osteostraci
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata
Osteostraci Hemicyclaspis Ungulaspis Ateleaspididae Aceraspis Ateleaspis Hirella Cornuata Camptaspis Cephalaspis Hildenaspis Janaspis Mimetaspis Pattenaspis Waengsjoeaspis Yvonaspis Zychaspis Benneviaspidida Benneviaspis Ectinaspis Hoelaspis Securiaspis Severaspis Boreaspididae Belonaspis Boreaspis Hapilaspis Spatulaspis Tauraspis Thyestiida Aestiaspis Auchenaspis Dartmuthia Didymaspis Ilemoraspis Procephalaspis Saaremaspis Thyestes Tyriaspis Witaaspis Kiaeraspididae Acrotomaspis Axinaspis Gustavaspis Kiaeraspis Nectaspis Norselaspis Tremataspididae Dobraspis Oeselaspis Sclerodus Tannuaspis Timanaspis Tremataspis Zenaspidida Spangenhelmaspis Wladysagitta Parameteoraspididae Balticaspis Escuminaspis Levesquaspis Parameteoraspis Trewinia Superciliaspididae Dentapelta Glabrapelta Superciliaspis Scolenaspididae Machairaspis Scolenaspis Ukrainaspis Zenaspididae Diademaspis Stensiopelta Tegaspis Zenaspis
Category

This article about a prehistoric jawless fish is a stub. You can help Misplaced Pages by expanding it.

• v
• t
• e

• Osteostraci
• Prehistoric jawless fish orders
• Prehistoric jawless fish stubs