Typothoracinae 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 subfamily

Aetosaurinae Aetosaurinae is one of the two main clades of aetosaurs, the other being Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to '' Aetosaurus'' than '' Desmatosuchus''. Aetosaurinae currently comprises ''Aetosau ...

. It was originally defined as a

stem-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 ...

including all aetosaurs closer to ''

Typothorax ''Typothorax'' is an extinct genus of typothoracine aetosaur that lived in the Late Triassic. Its remains have been found in North America. Two species are known: ''T. coccinarum'', the type species, and ''T. antiquum''. Description ''Typoth ...

'' than to ''

Stagonolepis ''Stagonolepis'' is an extinct genus of stagonolepidid aetosaur known from the Late Triassic (Carnian stage) Hassberge Formation of Germany, the Drawno Beds of Poland, and the Lossiemouth Sandstone of Scotland. Supposed fossils from North and ...

'' or ''

Desmatosuchus ''Desmatosuchus'' (, from Greek δεσμός ''desmos'' 'link' + σοῦχος ''soûkhos'' 'crocodile') is an extinct genus of archosaur belonging to the Order Aetosauria. It lived during the Late Triassic. Description ''Desmatosuchus'' was ...

''. This definition was later expanded to specifically exclude '' Aetosaurus''; as of 2016, Typothoracinae is defined as the least inclusive clade containing ''Typothorax'' and ''

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 specimens ...

'', but not ''Aetosaurus,'' ''Stagonolepis'', or ''Desmatosuchus''. The clade was first named in 2007 under the spelling Typothoracisinae, after its namesake ''Typothorax''. However, this spelling was based on incorrect taxonomic nomenclature, and the clade's name was corrected to Typothoracinae in 2016. Typothoracines can be distinguished by their wide bodies. The

transverse processes The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

of the dorsal (trunk) vertebrae are reinforced and elongated, more than twice the width of the centrum. Their

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

, on the other hand, are short. The overlying

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the und ...

of osteoderms has a very broad, discoidal shape, distinct from the narrower carapace seen in other aetosaurs. The widest dorsal paramedian osteoderms have a width-to-length ratio exceeding 3.5. They also tend to possess a strong keel running along their underside, as well as a sigmoid lateral edge which appears to have a "clipped" posterolateral corner. Though typothoracines lack the massive neck spines of certain desmatosuchines, their cervical (neck) lateral osteoderms do bear moderately large curved spines with a flattened cross section. The dorsal lateral osteoderms have a strongly bent shape: there is an acute angle of flexion between the dorsal (upper) flange and the lateral (outer and lower) flange, which meet along a low blade-like surface or short spine on the outer edge of the osteoderm. In the lateral osteoderms above the hip and the front part of the tail, the lateral flange is triangular and concave, leading up to a hooked eminence.

References

Aetosaurs Late Triassic first appearances Late Triassic extinctions {{triassic-animal-stub