{{Short description|Extinct genus of reptiles}} {{Automatic taxobox | taxon = Polesinesuchus | fossil_range = [[Late Triassic]]<br />~{{fossil range|231.4|225.9}} | image = Polesinesuchus skeletal (possible synonym with Aetosauroides).png | image_caption = Skeletal diagram of the holotype of '''''Polesinesuchus''''' | authority = Roberto-da-Silva ''et al.'' [[2014 in paleontology|2014]] | type_species = {{extinct}}'''''Polesinesuchus aurelioi''''' | type_species_authority = Roberto-da-Silva ''et al.'' 2014 }}
'''''Polesinesuchus''''' is an [[extinct]] [[genus]] of [[stagonolepidid]] [[aetosaur]] known from the [[Late Triassic]] of southern [[Brazil]]. Fossils have been found from the [[Santa Maria Formation|Santa Maria Supersequence]] of the late [[Carnian]] and early [[Norian]] stages, making ''Polesinesuchus'' one of the oldest aetosaurs. It contains a single species, '''''Polesinesuchus aurelioi''''', the fifth aetosaur species known from [[South America]] to date.<ref name="Polesinesuchus">{{Cite journal|last1=Roberto-Da-Silva|first1=L. C.|last2=Desojo|first2=J. B.|last3=Cabreira|first3=S. R. F.|last4=Aires|first4=A. S. S.|last5=Müller|first5=R. T.|last6=Pacheco|first6=C. P.|last7=Dias-Da-Silva|first7=S. R.|year=2014|title=A new aetosaur from the Upper Triassic of the Santa Maria Formation, southern Brazil|url=https://www.researchgate.net/publication/262696630|journal=Zootaxa|volume=3764|issue=3|pages=240–278|doi=10.11646/zootaxa.3764.3.1|pmid=24870635|hdl=11336/20729|hdl-access=free}}</ref> Anatomical evidence suggests that ''Polesinesuchus'' likely represents a juvenile individual of the contemporary ''[[Aetosauroides]]''.<ref name="paesneto2021axial">{{cite journal |last1=Paes-Neto |first1=V.D. |last2=Desojo |first2=J.B. |last3=Brust |first3=A.C.B. |last4=Schultz |first4=C.L. |last5=Da-Rosa |first5=A.A.S. |last6=Soares |first6=M.B. |year=2021 |title=Intraspecific variation in the axial skeleton of ''Aetosauroides scagliai'' (Archosauria: Aetosauria) and its implications for the aetosaur diversity of the Late Triassic of Brazil |journal=Annals of the Brazilian Academy of Sciences |volume=93 |issue=supp. 2 |article-number=e20201239 |doi=10.1590/0001-3765202120201239|pmid=34468486 |s2cid=237372648 |hdl=11336/150258 |hdl-access=free }}</ref><ref name="paesneto2021bc">{{cite journal |last1=Paes-Neto |first1=V.D. |last2=Desojo |first2=J.B. |last3=Brust |first3=A.C.B. |last4=Ribeiro |first4=A.M. |last5=Schultz |first5=C.L. |last6=Soares |first6=M.B. |year=2021 |title=The first braincase of the basal aetosaur ''Aetosauroides scagliai'' (Archosauria: Pseudosuchia) from the Upper Triassic of Brazil |journal=Journal of Vertebrate Paleontology |volume=41 |issue=2 |article-number=e1928681 |doi=10.1080/02724634.2021.1928681|s2cid=237518035 }}</ref>
== Discovery == ''Polesinesuchus'' was first named by Lúcio Roberto-da-Silva, Julia B. Desojo, Sérgio F. Cabreira, Alex S. S. Aires, Rodrigo T. Müller, Cristian P. Pacheco and Sérgio Dias-da-Silva in [[2014 in paleontology|2014]] and the [[type species]] is ''Polesinesuchus aurelioi''. It is known solely from its [[holotype]] specimen, a partially articulated partial [[skeleton]]. It is composed of the [[parietal bone]] and the [[Neurocranium|braincase]] as well as [[postcrania]]l elements including [[cervical vertebrae|cervical]], [[dorsal vertebrae|dorsal]], [[sacral vertebrae|sacral]] and [[caudal vertebrae]], both [[scapula]]e, a [[humerus]], the [[ilium (bone)|ilium]], [[pubis (bone)|pubis]], [[ischium]] and [[tibia]], a partial right pes, and anterior and mid-dorsal paramedian [[osteoderm]]s. It was collected from the [[Santa Maria Formation]] which dates back to the late [[Carnian]] and earliest [[Norian]] stages of the [[Late Triassic]].<ref name=Polesinesuchus/>
== Description == ''Polesinesuchus'' is known from a relatively small-sized individual with an estimated length of {{convert|76|cm}}, probably a two-year-old [[Juvenile (organism)|juvenile]] based on the incomplete fusion of neural arches to their [[Body of vertebra|centra]] in the whole [[vertebral column]].<ref name="paesneto2021axial"/> ''Polesinesuchus'' can be distinguished from all other [[aetosaur]]s by a unique combination of characters not controlled by [[ontogeny]], most of which are found in its vertebrae. Its [[cervical vertebrae]] show [[Articular processes|prezygapophyses]] that widely extend laterally through most of the anterior edge of the [[:wikt:diapophyses|diapophyses]]. In ''Polesinesuchus'', [[Hyposphene-hypantrum articulation|hyposphene articulations]] are absent in both cervical and mid-[[dorsal vertebrae]]. A ventral keel is present in the cervical vertebrae. The [[Body of vertebra|centra]] of the anterior and mid-dorsal vertebrae lack a lateral [[Fossa (anatomy)|fossa]]. The proximal end of the [[scapula]] is greatly expanded, while the medial portion of scapular blade is expanded anteroposteriorly. ''Polesinesuchus'' possess a short [[humerus]] with a robust shaft, and a dorsoventral and very low iliac blade with a long anterior process, exceeding slightly the pubic peduncle.<ref name=Polesinesuchus/> Yet, in 2021, it was found that many of these features fall within the range of variation present in juvenile specimens of ''[[Aetosauroides]]''. One example is the lateral fossa, which becomes more apparent in individuals of ''Aetosauroides'' longer than {{convert|1|m}}).<ref name="paesneto2021axial"/> Furthermore, a braincase of ''Aetosauroides'' had a remarkably similar structure of the basioccipital bone to ''Polesinesuchus''.<ref name="paesneto2021bc"/> For these reasons, ''Polesinesuchus'' was suggested as a junior synonym of ''Aetosauroides''.<ref name="paesneto2021axial"/>
== Classification == A [[phylogenetic]] analysis was conducted in the first description of ''Polesinesuchus'' based on a slightly updated data matrix from previous analyses, resulting in a matrix that includes 19 aetosaurs and two outgroup taxa which are scored based on 37 morphological traits. ''Polesinesuchus'' was recovered as the [[sister taxon]] of ''[[Aetobarbakinoides]]'', known from the same [[Formation (stratigraphy)|geological formation]]. Close relatives of this [[clade]] included ''Aetosauroides'' and ''[[Neoaetosauroides]]'', both of which are also from South America. However, [[Aetosaurinae]] is found to be [[paraphyletic]] representing a [[evolutionary grade|grade]] of early aetosaurs that developed into desmatosuchines and typothoracisines later in the Triassic. Although this clade is placed in a relatively [[basal (phylogenetics)|basal]] [[phylogenetic]] position among [[stagonolepidid]] aetosaurs, it is closely related to both [[desmatosuchine]]s and [[typothoracisine]]s, two derived clades of stagonolepidids. Below is a [[cladogram]] modified from this analysis.<ref name=Polesinesuchus/>
{{clade| style=font-size:85%;line-height:85% |label1=[[Aetosauria]] |1={{clade |1=''[[Aetosauroides scagliai]]'' |label2=[[Stagonolepididae]] |2={{clade |1=''[[Aetosaurus ferratus]]'' |2=''[[Coahomasuchus kahleorum]]'' |3=''[[Neoaetosauroides engaeus]]'' |4={{clade |1=''[[Calyptosuchus wellesi]]'' |2=''[[Stagonolepis robertsoni]]'' |3={{clade |1={{clade |1=''[[Aetobarbakinoides brasiliensis]]'' |2='''''Polesinesuchus aurelioi'''''}} |2={{clade |label1=[[Typothoracisinae]] |1={{clade |1={{clade |1=''[[Typothorax]]'' |2=''[[Redondasuchus]]''}} |label2=[[Paratypothoracisini]] |2={{clade |1=''[[Tecovasuchus chatterjeei]]'' |2={{clade |1=''[[Rioarribasuchus chamaensis]]'' |2=''[[Paratypothorax andressorum]]''}} }} }} |label2=[[Desmatosuchinae]] |2={{clade |1=''[[Sierritasuchus macalpini]]'' |2={{clade |1=''[[Longosuchus meadei]]'' |2={{clade |1=''[[Lucasuchus hunti]]'' |2={{clade |1=''[[Acaenasuchus geoffreyi]]'' |label2=''[[Desmatosuchus]]'' |2={{clade |1=''[[Desmatosuchus haplocerus]]'' |2=''[[Desmatosuchus smalli]]''}} }} }} }} }} }} }} }} }} }} }}
== See also == {{Portal|Brazil|Paleontology}} * ''[[Buriolestes]]'' * ''[[Ixalerpeton]]''
== References == {{Reflist}}
{{Aetosauria}} {{Taxonbar|from=Q15726984}}
[[Category:Aetosauria]] [[Category:Late Triassic reptiles of South America]] [[Category:Santa Maria Formation]] [[Category:Fossils of Brazil]] [[Category:Fossil taxa described in 2014]] [[Category:Prehistoric pseudosuchian genera]] [[Category:Taxa named by Rodrigo T. Müller]]