Saichania and Minotaurasaurus in that it lacks postocular caputegulae (or small, polygonal bony plates behind the orbit) and has a proportionally high occiput in caudal view. The study additionally found that PIN 3142/250 (i.e. T. teresae) can be distinguished from T. kielanae in that the accessory osteoderm is not fused to the roof of the skull, the quadrate and paroccipital process are not fused, the back of the skull roof is strongly sculptured, and the openings for the fourth to twelfth cranial nerves is bifurcated. Much information given about Tarchia in older work refers to PIN 3142/250 (which was briefly referred to Saichania until it was named as T. teresae in 2016). In 2001, it was stated that, in Tarchia, wear facets indicative of tooth-to-tooth occlusion are present; this likely does not refer to the holotype specimen, since in the holotype no teeth are preserved. Phylogeny Vickaryous et alii in 2004 stated that Tarchia was basal to two distinct clades of Late Cretaceous ankylosaurids: one comprising North American taxa (Ankylosaurus, Euoplocephalus) and the other comprising Asian taxa (Pinacosaurus spp., Saichania, Tianzhenosaurus, Talarurus). However, this was again based on PIN 3142/250, the characters of which usually defined the operational taxonomic unit named Tarchia in the various cladistic analyses. Remarkably, Tarchia and Saichania nevertheless in these analyses often occupied very different positions. The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie: A limited phylogenetic analysis conducted in the 2016 redescription of Tarchia, focusing on the interrelationships between Tarchia, Saichania, and Minotaurasaurus, is reproduced below. Palaeobiology The rocks in which Tarchia fossils were found likely represent eolian dunes and interdune environments, with small intermittent lakes and seasonal streams. Hence, we know that Tarchia was a desert animal. On the other hand, well-watered forest would have been present. Tarchia would have been preyed upon by Tarbosaurus. Paleopathology One skull of Tarchia shows tooth marks identified as belonging to the tyrannosaurid, Tarbosaurus, indicating the theropod hunted the ankylosaurid. See also Timeline of ankylosaur research 2017 in archosaur paleontology References External links Tarchia in the Dino Directory Ankylosaurids Late Cretaceous dinosaurs of Asia Fossils of Mongolia Maastrichtian life Fossil taxa described in 1977 Taxa named by Teresa Maryańska Ornithischian genera