Paratypothoracini is a clade of

aetosaur Aetosaurs () are heavily armored reptiles belonging to the extinct order Aetosauria (; from Greek, (aetos, "eagle") and (, "lizard")). They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs ...

s within the group Typothoracinae. It is a

node-based taxon Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a ''type'', which c ...

that includes '' Rioarribasuchus'' (=''

Heliocanthus ''Rioarribasuchus'' is a genus of aetosaur. Fossils have been found from the Chinle Formation in Arizona and New Mexico that date back to the upper Late Carnian stage of the Late Triassic. History ''"Desmatosuchus" chamaensis'' was named in 2003 ...

''), '' Paratypothorax'', '' Tecovasuchus'', and all descendants of their most recent common ancestor. The clade was first named in 2007 under the spelling Paraypothoracisini, after its namesake ''Paratypothorax''. However, this spelling was based on incorrect taxonomic nomenclature, and the clade's name was corrected to Paratypothoracinae in 2016. All

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

that diagnose Paratypothoracini can be found in their

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinc ...

s. The paramedian osteoderms are wide and lie flat, without any apparent flexure (a trait convergent with some desmatosuchin aetosaurs) The paramedians possess knob- or spine-like dorsal eminences which are strongly offset medially and practically never contact the rear margins of their respective plates. The anterior bar of each paramedian is present but only weakly raised (except in ''Tecovasuchus'', which has a stronger anterior bar). The lateral osteoderms have a dorsal (upper) flange which is tongue-shaped and much smaller than the lateral (lower and outer) flange. In the cervical (neck) and anterior dorsal (front of the torso) regions, the lateral osteoderms send out a long and flattened horn-like blade. ''Paratypothorax'' and a vertebra referred to ''Rioarribasuchus'' also have anterior caudal ribs (at the base of the tail) which are positioned lower on the centrum than in other aetosaurs.

References

Aetosaurs Late Triassic first appearances {{paleo-archosaur-stub