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.
^Pan, Zhaohui; Niu, Zhibin; Xian, Zumin; Zhu, Min (2023-01-03). "A novel specimen-based mid-Paleozoic dataset of antiarch placoderms (the most basal jawed vertebrates)". Earth System Science Data. 15 (1): 41–51. Bibcode:2023ESSD...15...41P. doi:10.5194/essd-15-41-2023. ISSN 1866-3508.
^Jia, L. T.; Zhu, M.; Zhao, W. J. (2010). "A new antiarch fish from the Upper Devonian Zhongning Formation of Ningxia, China". Palaeoworld. 19 (1–2): 136. doi:10.1016/j.palwor.2010.02.002.
Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. ISBN0-8018-5438-5
Sepkoski, Jack (2002). . Bulletins of American Paleontology. 364: 560. Archived from the original on 2004-10-14. Retrieved 2011-05-20.
External linksedit
Review of Antiarcha at Paleos
December 12, 2023
antiarchi, confused, with, acritarch, opposite, anus, order, heavily, armored, placoderms, antiarchs, form, second, most, successful, group, placoderms, after, arthrodires, terms, numbers, species, range, environments, order, name, coined, edward, drinker, cop. Not to be confused with acritarch 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 AntiarchiTemporal range Ludfordian 1 Famennian 425 6 358 9 Ma PreꞒ Ꞓ O S D C P T J K Pg NBothriolepis canadensisScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass PlacodermiOrder AntiarchiCope 1885The 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 Contents 1 Phylogeny 2 Timeline of genera 3 References 4 External linksPhylogeny editBelow is a cladogram from Jia et al 2010 2 Antiarchi ParayunnanolepisDayaoshaniaGrenfellaspisEuantiarcha Bothriolepidoidei LuquanolepisNawagiaspisJiangxilepididae JiangxilepisNingxialepisDianolepisBothriolepididae BothriolepisGrossilepisMonarolepisBriagalepisMicrobrachiidae WudinolepisHohsienolepisMicrobrachiusAsterolepidoidei ByssacanthusHunanolepisKirgisolepisPterichthyodesGerdalepisSherbonaspisStegolepisAsterolepisRemigolepisPambulaspisTimeline of genera edit nbsp Chuchinolepis Vanchienolepis and YunnanolepisReferences edit Pan Zhaohui Niu Zhibin Xian Zumin Zhu Min 2023 01 03 A novel specimen based mid Paleozoic dataset of antiarch placoderms the most basal jawed vertebrates Earth System Science Data 15 1 41 51 Bibcode 2023ESSD 15 41P doi 10 5194 essd 15 41 2023 ISSN 1866 3508 Jia L T Zhu M Zhao W J 2010 A new antiarch fish from the Upper Devonian Zhongning Formation of Ningxia China Palaeoworld 19 1 2 136 doi 10 1016 j palwor 2010 02 002 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 External links editReview of Antiarcha at Paleos Retrieved from https en wikipedia org w index php title Antiarchi amp oldid 1187875079 Phylogeny, wikipedia, wiki, book, books, library,
