Antiarchi Temporal range: Ludfordian[1]- Famennian 425.6–358.9 Ma PreꞒ Ꞓ 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.

Below is a cladogram from Jia et al. (2010):^[3]

• 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. Archived from the original on 2004-10-14. Retrieved 2011-05-20.

• Review of Antiarcha at Paleos

v t e "Placodermi"
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Infraphylum: Gnathostomata Gnathostomata see Gnathostomata Placodermi see below↓ Placodermi
Acanthothoraci* Hagiangella Palaeacanthaspidae* Arabosteus Dobrowlania Kimaspis Kolymaspis Kosoraspis Palaeacanthaspis Radotina Romundina Sudaspis Tlamaspis Weejasperaspididae Murrindalaspis Weejasperaspis Petalichthyida Diandongpetalichthys Neopetalichthys Quasipetalichthyidae Eurycaraspis Pauropetalichthys Quasipetalichthys Macropetalichthyidae Ellopetalichthys Epipetalichthys Lunaspis Macropetalichthys Notopetalichthys Shearsbyaspis Tongdzuylepis Wijdeaspis Ptyctodontida Austroptyctodus Campbellodus Chelyophorus Ctenurella Denisonodus Destnoporella Eczematolepis Goniosteus Kimbryanodus Materpiscis Meeksiella Palaeomylus Ptyctodopsis Ptyctodus Rhamphodopsis Rhynchodus Rhenanida Asterosteus Bolivosteus Gemuendina Jagorina Nefudina Ohioaspis Antiarchi see Antiarchi Arthrodira see Arthrodira Others "maxillate placoderms" Bianchengichthys Entelognathus Qilinyu Silurolepis? Brindabellaspis Holopetalichthys Minjinia Pseudopetalichthys Stensioella Xiushanosteus
Category

v t e Antiarchi
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Placodermi Gnathostomata see Gnathostomata Placodermi see Placodermi Antiarchi see below↓ Antiarchi
Antiarchi Minicrania Yunnanolepidoidei Chuchinolepis Heteroyunnanolepis Shimenolepis Vanchienolepis Zhanjilepis Yunnanolepididae Mizia Parayunnanolepis Phymolepis Vukhuclepis Yunnanolepis Sinolepididae Dayaoshania Grenfellaspis Liujiangolepis Sinolepis Xichonolepis Euantiarcha "Bothriolepidoidei" Dianolepis Tenizolepis Microbrachiidae Hohsienolepis Microbrachius Wudinolepis Bothriolepididae Bothriolepis Briagalepis Grossilepis Houershanaspis Monarolepis Vietnamaspis Wufengshania Asterolepidoidei Asperaspis Asterolepis Byssacanthus Colombialepis Gerdalepis Grossaspis Hunanolepis Jiangxilepis Kirgisolepis Lepadolepis Luquanolepis Nawagiaspis Ningxialepis Pambulaspis Pterichthyodes Remigolepis Sherbonaspis Stegolepis Wurungulepis
Category