Biology:Antiarchi

Short description: Extinct order of fishes

Antiarchi Temporal range: Ludfordian- Famennian 425.6–358.9 Ma PreЄ Є O S D C P T J K Pg N
Bothriolepis canadensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Antiarchi Cope, 1885

Antiarchi ("opposite anus") is an order of heavily armored placoderms. The antiarchs form the second-most successful group of placoderms after the arthrodires in terms of numbers of species and range of environments. The order's name was coined by Edward Drinker Cope, who, when examining some fossils that he thought were armored tunicates related to Chelyosoma, mistakenly thought that the orbital fenestra (i.e., the hole in the headshield for the eyes, nose and pineal foramen) was the opening for the mouth, or oral siphon, and that the opening for the anal siphon was on the other side of the body, as opposed to having both oral and anal siphons together at one end.

The front portions of their bodies were heavily armored, to the point of literally resembling a box with eyes, with the sometimes scaled, sometimes naked rear portions often becoming sinuous, particularly with later forms. The pair of pectoral fins were modified into a pair of caliper-like, or arthropod-like limbs. In primitive forms, such as Yunnanolepis, the limbs were thick and short, while in advanced forms, such as Bothriolepis, the limbs were long and had elbow-like joints. The function of the limbs are still not perfectly understood, but, most hypothesize that they helped their owners pull themselves across the substrate, as well as allow their owners to bury themselves into the substrate.

Antiarchi, along with Brindabellaspis, form some of the most basal clades of the Placodermi, or Gnathostomata. They are more related to other placoderms and the more derived jawed fish than the Cephalaspidomorphi.

Phylogeny

Below is a cladogram from Jia et al. (2010):

Antiarchi

Parayunnanolepis       Dayaoshania     Grenfellaspis     Euantiarcha Bothriolepidoidei   Luquanolepis       Nawagiaspis     Jiangxilepididae   Jiangxilepis     Ningxialepis         Dianolepis     Bothriolepididae     Bothriolepis     Grossilepis         Monarolepis     Briagalepis       Microbrachiidae   Wudinolepis       Hohsienolepis     Microbrachius                 Asterolepidoidei   Byssacanthus         Hunanolepis         Kirgisolepis     Pterichthyodes         Gerdalepis     Sherbonaspis             Stegolepis       Asterolepis       Remigolepis     Pambulaspis

Timeline of genera

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 id:paleozoic     value:rgb(0.6,0.75,0.55)
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from: -416    till: -411.2   color:earlydevonian    text:Lochkovian
from: -411.2    till: -407   color:earlydevonian    text:Pragian
from: -407    till: -397.5   color:earlydevonian    text:Emsian
from: -397.5    till: -391.8   color:middledevonian    text:Eifelian
from: -391.8    till: -385.3   color:middledevonian    text:Givetian
from: -385.3    till: -374.5   color:latedevonian    text:Frasnian
from: -374.5    till: -359.2   color:latedevonian    text:Famennian

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color:earlydevonian	bar:NAM1	from:	-416	till:	-411.2	text:	Phymolepis
color:earlydevonian	bar:NAM2	from:	-416	till:	-411.2	text:	Chujinolepis
color:earlydevonian	bar:NAM3	from:	-416	till:	-411.2	text:	Zhanjilepis
color:earlydevonian	bar:NAM4	from:	-416	till:	-407	text:	Yunnanolepis
color:earlydevonian	bar:NAM5	from:	-411.2	till:	-407	text:	Liujiangolepis
color:middledevonian	bar:NAM6	from:	-391.8	till:	-385.3	text:	Grossaspis
color:latedevonian	bar:NAM7	from:	-385.3	till:	-374.5	text:	Taeniolepis
color:latedevonian	bar:NAM8	from:	-378.1	till:	-374.5	text:	Lepadolepis
color:latedevonian	bar:NAM9	from:	-374.5	till:	-359.2	text:	Jiangxilepus
color:latedevonian	bar:NAM10	from:	-374.5	till:	-359.2	text:	Sinolepis
color:latedevonian	bar:NAM11	from:	-374.5	till:	-359.2	text:	Xichonolepis

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from: -416    till: -411.2   color:earlydevonian    text:Lochkovian
from: -411.2    till: -407   color:earlydevonian    text:Pragian
from: -407    till: -397.5   color:earlydevonian    text:Emsian
from: -397.5    till: -391.8   color:middledevonian    text:Eifelian
from: -391.8    till: -385.3   color:middledevonian    text:Givetian
from: -385.3    till: -374.5   color:latedevonian    text:Frasnian
from: -374.5    till: -359.2   color:latedevonian    text:Famennian

bar:era
from: -416    till: -359.2   color:devonian    text:Devonian

</timeline>

Chuchinolepis, Vanchienolepis and Yunnanolepis

References

• Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. ISBN:0-8018-5438-5
• Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Placodermi entry)". Bulletins of American Paleontology 364: 560. http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=564&rank=class. Retrieved 2011-05-20. 

External links

• Review of Antiarcha at Paleos

Wikidata ☰ Q150593 entry