Antiarchi


Antiarchi 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 Chelysoma, mistakenly thought that the orbital fenestra 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, 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.

Phylogeny

Below is a cladogram from Jia et al. :

Timeline of genera


ImageSize = width:1000px height:auto barincrement:15px
PlotArea = left:10px bottom:50px top:10px right:10px
Period = from:-416 till:-350
TimeAxis = orientation:horizontal
ScaleMajor = unit:year increment:5 start:-416
ScaleMinor = unit:year increment:1 start:-416
TimeAxis = orientation:hor
AlignBars = justify
Colors =
#legends
id:CAR value:claret
id:ANK value:rgb
id:HER value:teal
id:HAD value:green
id:OMN value:blue
id:black value:black
id:white value:white
id:paleozoic value:rgb
id:cambrian value:rgb
id:ordovician value:rgb
id:silurian value:rgb
id:devonian value:rgb
id:earlydevonian value:rgb
id:middledevonian value:rgb
id:latedevonian value:rgb
id:carboniferous value:rgb
id:mississippian value:rgb
id:pennsylvanian value:rgb
id:permian value:rgb
id:mesozoic value:rgb
id:triassic value:rgb
id:jurassic value:rgb
id:cretaceous value:rgb
id:cenozoic value:rgb
id:paleogene value:rgb
id:neogene value:rgb
id:quaternary value:rgb
BarData=
bar:eratop
bar:space
bar:periodtop
bar:space
bar:NAM1
bar:NAM2
bar:NAM3
bar:NAM4
bar:NAM5
bar:NAM6
bar:NAM7
bar:NAM8
bar:NAM9
bar:NAM10
bar:NAM11
bar:space
bar:period
bar:space
bar:era
PlotData=
align:center textcolor:black fontsize:M mark: width:25
shift:

bar:periodtop
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:eratop
from: -416 till: -359.2 color:devonian text:Devonian
PlotData=
align:left fontsize:M mark: width:5 anchor:till align:left
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
PlotData=
align:center textcolor:black fontsize:M mark: width:25

bar:period
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

, Vanchienolepis and Yunnanolepis''