Paratypothoracini is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

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 Typothoracinae is a clade of aetosaurs within the subfamily Aetosaurinae. It was originally defined as a stem-based taxon including all aetosaurs closer to ''Typothorax'' than to ''Stagonolepis'' or ''Desmatosuchus''. This definition was later ex ...

. 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 ...

that includes ''

Rioarribasuchus ''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 ...

'' (=''

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 ''Paratypothorax'' is an extinct genus of aetosaur, known from a single species, ''Paratypothorax andressorum''. It was a broadly distributed member of the group found in Germany, North America, and possibly parts of Gondwana. The best specimen ...

'', ''

Tecovasuchus ''Tecovasuchus'' is an extinct genus of aetosaur. It is known primarily from osteoderms found from the Tecovas Formation in Texas, which is Late Triassic in age, dating back to the lower Norian. Material is also known from several other localitie ...

'', 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 have ...

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 (extinct amp ...

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