Polesinesuchus aurelioi Roberto-Da-Silva, Desojo, Cabreira, Aires, Müller, Pacheco & Dias-Da-Silva 2014, gen. et sp. nov.
Creators: name: Roberto-Da-Silva, Lúcio
name: Desojo, Julia B.
name: Cabreira, Sérgio F.
name: Aires, Alex S. S.
name: Müller, Rodrigo T.
name: Pacheco, Cristian P.
name: Dias-Da-Silva, Sérgio
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Prolacertiformes
Stagonolepididae
Polesinesuchus
Polesinesuchus aurelioi

description: Polesinesuchus aurelioi gen. et sp. nov.
Holotype: ULBRAPVT003, comprising cranial and postcranial elements: a partial parietal and a well preserved basioccipital; a partial axial skeleton (cervical, dorsal, sacral and caudal vertebrae); an incomplete pectoral girdle (partial scapulae, coracoids, and interclavicle); two partial humeri and both ulnae; a right pelvic girdle (ilium, ischium, and pubis); parts of both hindlimbs (femora, tibiae, fibulae, both astragali, and a left calcaneum); and pes (metatarsal III and V, unidentifiable phalanges, and two ungual phalanges). Ten isolated osteoderms from dorsal, ventral, and appendicular region of the armor (see Tables 1, 2, 3, and 4 below for anatomical measurements of skeletal elements of ULBRAPVT003).
Type locality and horizon: Buriol outcrop, municipality of São João do Polêsine (coordinates 29º39’34.2”S; 53º25’47.4”W) in the central region of the State of Rio Grande do Sul, Southern Brazil. This locality is included in the Sequence 2 of the Santa Maria Supersequence, Hyperodapedon Assemblage Zone (Fig. 3) (Langer et al. 2007; Soares et al. 2011).
Etymology. The generic name is derived from the name of the municipality from where the specimen was recovered (São João do Polêsine, Rio Grande do Sul State). The specific name is in honor of the physician Pedro Lucas Porcela Aurélio, a paleontology enthusiast from Rio Grande do Sul.
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Diagnosis. Polesinesuchus is distinguished from all other aetosaurs by the following unique combination of characters: cervical vertebrae with prezygapophyses widely extending laterally through most of the anterior edge of the diapophyses; absence of hyposphene articulation in both cervical and mid-dorsal vertebrae; anterior articular facet width of cervical vertebrae measuring less than 1.2 times the posterior one; presence of a ventral keel in cervical vertebrae; anterior and mid-dorsal vertebrae without a lateral fossa in their centra; expanded proximal end of scapula; anteroposteriorly expanded medial portion of scapular blade; a short humerus with a robust shaft; and a dorsoventral and very low iliac blade with a long anterior process which slightly exceeds the pubic peduncle. Polesinesuchus differs from Aetosauroides scagliai by the presence of an anteroposterior projection of the scapular shaft, absence of a lateral fossa in the presacral vertebrae, tip of the anterior process of the ilium longer and very pointed in comparison, femoral distal ends slightly twisted along the axial length. P. aurelioi differs from Aetobarbakinoides by the presence of a ventral keel in cervical vertebrae, absence of a circular pit in the neural spine, absence of a hyposphene articulation in dorsal vertebrae, the humeral shaft is very robust in comparison, the larger tuberosity of the humerus is poorly defined in comparison, and the tibial shaft is very robust in comparison. In Polesinesuchus, the ornamentation of the paramedian osteoderms shows a radial pattern with circular pits, grooves and ridges originated from a low eminence. The radial pattern observed in Polesinesuchus is different from the reticular one of Typothorax, Redondasuchus, C hilenosuchus. Ornamentation is randomly distributed in Desmatosuchus smalli, D. spurensis, Longosuchus and Acaenasuchus. The paramedian osteoderm of Polesinesuchus is subretangular with a width/length ratio of about of 3.3.
Description. The specimen is well- preserved, as most of the thin, delicate and small elements (e.g. interclavicle, sacral and caudal vertebrae, and pedal elements) present a high quality of fossilization. Just a few bones are weathered and crushed (e.g. right coracoid, left humerus, a few paramedian and ventral osteoderms).
Ontogenetic stage. The recognition of ontogenetic stages in aetosaurs is problematic, due to the lack of information regarding juvenile individuals (Parker 2008; Taborda et al. 2013). Moreover, the ontogeny of crocodile-line archosaurs is poorly known (Schoch 2007). In archosaurs, the usual practice addressing this issue is to consider individuals with closed neurocentral vertebral sutures as fully grown adults (Brochu 1996). The small size of an individual is not reliable information to establish its juvenile ontogenetic stage. In recent years, paleohistological analyses of growth marks in osteoderms arose as a possible solution to the understanding of ontogeny in the Aetosauria (Cerda & Desojo 2011; Taborda et al. 2013; Torsten et al. in press). Still, the ontogenetic stage of Polesinesuchus was tentatively proposed based solely in the observation of neurocentral sutures, in which they are widely opened. Hence, here we tentatively propose that Polesinesuchus is a juvenile specimen. Future paleohistological studies are needed to obtain a more accurate idea regarding the ontogenetic stage of Polesinesuchus (meaning estimating how immature this individual was when he died).
Parietal. Only the left parietal is preserved, which is mostly broken. A single identifiable small ridge separates this element in two parts with distinct angles (Fig. 4 g). Medial to this ridge, it is almost flat, showing a gentle radial ornamentation constituted of small and irregular fossae. Laterally, this bone protrudes ventrally and forms the dorsal margin of the supratemporal fenestrae. The posterior limit of the parietal bears a thin and incipient overhanging flange (probably by its juvenile condition), which accommodates nucal osteoderms (as seem in Aetosauroides scagliai PVL 2059, Neoaetosauroides engaeus PVL 5698, Desmatosuchus smalli TTUP 9024), a feature that characterizes aetosaurs. Due to the fragmentary nature of this element, most of its features are not observable.
Braincase. The braincase is represented by a partial but still well-preserved basioccipital, which participates in both condylar neck and occipital condyle (Fig. 4 a–f). It is dorsally placed to the magnum foramen as in Tecovasuchus chatterjeei (holotype TTUP 545; Martz & Small 2006), Typothorax coccinarum (TTUP 9214; Martz 2002), Desmatosuchus smalli (Small 2002), and Neoaetosauroides engaeus (PVL 5698). The articular facet of the occipital condyle is slightly projected dorsoventrally, as in Calyptosuchus wellesi (PEFO 34516). In posterior view, the occipital condyle is semicircular with a shallow notochordal pit in the center of its articular surface, a condition also observed in Stagonolepis olenkae (Sulej 2009). Two non-contacting facets for articulation with the exoccipitals are present in the dorsolateral surface of the occipital condyle, as in Longosuchus meadei (TTU 31185) and Desmatosuchus smalli (Small 2002), contrasting with the condition in Neoaetosauroides engaeus (PVL 5698). A pair of ventrally projecting knobs from the basioccipital, together with the basisphenoid, is present at the basis of the condylar neck and forms the basal tubera. These tubera serve as areas to attach subvertebral muscles (Romer 1956; Desojo & Baéz 2007). Despite the non-preservation of the exoccipitals, the basioccipital presents two channels in dorsal view. The first one forms part to the metotic foramen, which encloses nerves IX, X, XI and jugular vein as seen in Tecovasuchus chatterjeei (Martz & Small 2006). Posteriorly, the basioccipital also partially compose the ventral margin of the foramen for the hypoglossal nerve (XII).
Cervical vertebrae. Six cervical elements, including the centrum of the axis, are preserved. Based on the information about the position of their parapophysis, the degree of prominence of their ventral keels, and the size of the vertebral centra, their placement along the axial skeleton was tentatively assigned. The cervical segment is constituted by the axis and probably third, fourth, fifth, seventh, and eighth cervical vertebrae. Thus, two cervical elements are not preserved in the series, as in aetosaurs nine cervical vertebrae are considered to be present (Walker 1961; Parker 2008). On the other hand, a row of seven cervical paramedian osteoderms is present in the cervical region of Aetosaurus ferratus (SMNS 5770 S4, S7, S8, S16, S19), if each paramedian osteoderm is correlated with only one underling vertebra.
Axis. This element is poorly preserved, comprising only the centrum, which is mostly constricted along its length. The anterior facet of articulation is comparatively more distinguishable than the posterior one, being “U”- shaped. It is also possible to observe a prominent and dorsally displaced odontoid process (Fig. 5). Its posterior facet is circular and concave. In lateral view, the ventral surface of the centrum is shorter than the dorsal one; a small parapophysis, almost ventrally displaced, is also present. In ventral view, a conspicuous ventral keel is present, as occurs in Aetosauroides scagliai (PVL 2059; MCP13a–b-PV), Neoaetosauroides engaeus (PVL 5698), Longosuchus meadei (TMM 31185), Stagonolepis robertsoni and Typothorax coccinarum (Long & Murry 1995 fig 102c; Desojo et al. 2012). In contrast, this feature is absent in Aetobarbakinoides brasiliensis (CPE2 168) and Desmatosuchus spurensis (Parker 2008). In lateral view, the axis of Polesinesuchus does not present the wellrimmed fossa observable in cervical vertebrae of A. scagliai (PVL 2059; MCP13a–b-PV), (Desojo & Ezcurra 2011). This absence is shared with Aetobarbakinoides brasiliensis (CPE2 168) and Longosuchus meadei (TMM 31185). Thus, the presence of a ventral keel and the absence of well-rimmed fossa are characters extended to all preserved cervical elements of Polesinesuchus.
Postaxial cervical vertebrae. The third (?) cervical element is almost complete, preserving both neural arch and spines (Fig. 6). Two neural pedicles are preserved, both higher than the centrum and laterally projected; a condition shared with Aetobarbakinoides brasiliensis (CPE2 168). In lateral and medial views they present a slight concavity, as in Longosuchus meadei (TMM 31185). The neural canal presents the same ratio and size as Aetobarbakinoides (its height is two times lower than the height of the anterior articular surface of the centrum). The transverse process is short and lateroventrally projected, and its diapophysis is oval-shaped. The infradiapophyseal lamina is absent in cervical elements of the holotype, as in Neoaetosauroides (PVL 3525) and Longosuchus meadei (TMM 31185). Conversely, in Aetobarbakinoides brasiliensis (CPE2 168) and Aetosauroides scagliai (PVL 2059) the infradiapophyseal lamina is present (Desojo et al. 2012). In Polesinesuchus, the absence of both postzygapophyseal lamina and infradiapophyseal fossa are shared with Desmatosuchus spurensis (Parker 2008; Desojo et al. 2012). Only the right prezygapophysis is preserved in the holotype of Polesinesuchus. Its articulation facet is dorsally projected and medially restricted, not exceeding the anterior edge of the diapophysis as in Aetosauroides scagliai (PVL 2059), Neoaetosauroides engaeus (PVL 5698), Typothorax coccinarum (TTU P- 9214), Desmatosuchus spurensis (Parker 2008) and Stagonolepis robertsoni (NHMUK 4784). Conversely, Aetobarbakinoides brasiliensis presents laterally projected prezygapophyses (CPE2 168). In Polesinesuchus a small oval-shaped fossa is visible between the prezygapophysis. This fossa is known as the prespinal fossa, which is not dorsally extended along the neural spine, a condition similar to that found in Aetobarbakinoides (CPE2 168). Unfortunately, none of the postzygapophyses are preserved in the cervical vertebrae of the holotype. Its centrum is amphicoelous with a smooth lateromedial constriction. Its length is longer than the height of the anterior facet with an length:height ratio of 1.2. This condition is similar to that presented in Aetosauroides scagliai (PVL 2059) (Fig. 6). In Polesinesuchus the anterior facet of the centrum is wider than the posterior one (1.2 times) but in a comparative smaller degree regarding to Aetobarbakinoides (1.35 times). Desmatosuchus spurensis (Parker 2003, 2008) and Typothorax (Martz 2002) also present a smaller degree regarding this ratio (Parker 2008; Desojo et al. 2012). The lateral surface of the cervical centrum is slightly concave and lacks a well-rimmed fossa. It is thus distinct from Aetosauroides scagliai (PVL 2059) and Longosuchus meadei (TMM 31185). The absence of a wellrimmed fossa is a condition shared with Aetobarbakinoides brasiliensis (CPE2 168). The parapophysis is situated in the ventralmost portion of the anterior margin of the centrum and placed in a low pedicle, a similar condition to that found in Aetobarbakinoides (Desojo et al. 2012). Additionally, in ventral view, Polesinesuchus presents a sharp ventral keel as in Aetosauroides scagliai (PVL 2059; MCP 13-a–b-PV), Stagonolepis robertsoni (Walker 1961: fig 7f), Typothorax (Long & Murry 1995: 102c) and Neoaetosauroides engaeus (PVL 5698), (Desojo et al. 2012). Conversely, in Aetobarbakinoides brasiliensis (CPE2 168), Longosuchus meadei (TMM 31185), and Desmatosuchus spurensis the ventral keel is absent (Parker 2008). The fourth (?) cervical element is represented only by a centrum (Fig. 7 a–f). In the fifth (?) cervical element the set of features is the same of the third one, including the position of the parapophysis. It comprises the centrum and the left neural pedicle (Fig. 7 g–l). Only the prezygapophysis is preserved.
The seventh (?) cervical vertebra preserves the centrum and also the left neural pedicle (Fig. 8 a–f). It also shows a ventrally projected transverse process longer than the one of the third vertebra. Its parapophyses are dorsally displaced and close to the neurocentral suture. The eighth vertebra only preserves the centrum that presents the same characteristics already mentioned for the previous elements. Additionally, it is possible to observe a diagenetic distortion in the right surface of the centrum, which makes it more swollen than the parapophysis in comparison (Fig. 8 g–l). In general, the cervical centra of Polesinesuchus are robust with ovalshaped articular facets. In contrast, Desmatosuchus spurensis presents subrectangular facets on its centra (Parker 2008) Moreover, the length:height ratio of the all cervical centra of the Polesinesuchus is about 1.2.
Dorsal vertebrae. The first dorsal vertebra presents the left neural arch pedicle and preserves its pre- and postzygapophyses, transverse process, and centrum (Fig. 9 a–f). In lateral view, this element is anteroposteriorly shorter than the subsequent one (the more posteriorly placed dorsal vertebrae). Its centrum is amphicoelous, laterally compressed, and spool-shaped as in several aetosaurs, such as Desmatosuchus spurensis and Calyptosuchus wellesi (Long & Murry 1995; Parker 2008), Neoaetosauroides engaeus (PVL 3525), Aetosauroides scagliai (Desojo & Ezcurra 2011). The centrum of Polesinesuchus is longer than the height of its anterior articular facet, with a ratio of approximately 1.7, resembling the condition found in both anterior and medial dorsal vertebrae of Aetosauroides scagliai (1.5 in PVL 2073), anterior dorsal of Stagonolepis robertsoni (1.45 in NHMUK R4784; Walker 1961: fig 7i) and also of Sierritasuchus (1.46 in Parker et al. 2008: fig 2g) (Desojo et al. 2012). The parapophyses are present and dorsally displaced, close to the neurocentral suture. Additionally, a well-rimmed fossa is absent in the lateral surface of the centrum, the same condition of Aetobarbakinoides brasiliensis (Desojo et al. 2012) and Desmatosuchus spurensis (Parker 2008). In contrast, in Aetosauroides scagliai this structure is present (e.g. PVL 2073, PVL 2059, and PVL 2052). In ventral view, the centrum is devoid of a ventral keel, resembling the condition of Neoaetosauroides engaeus (PVL 3525), Aetosauroides scagliai, Desmatosuchus spurensis and Longosuchus meadei (Long & Murry 1995; Parker 2008). The infradiapophyseal lamina that occurs in Aetosauroides, is absent in the first dorsal vertebra of Polesinesuchus and Aetobarbakinoides (Desojo et al. 2012). Its absence is shared with Desmatosuchus spurensis (Parker 2008). The transverse process is shorter than that from the middle dorsal ones, but heavier, showing a slightly anterior displacement in relation to the center of the neural arch, a condition shared with Aetosauroides (MCP 13a–b-PV), (Desojo & Ezcurra 2011). In posterior view, the transverse process possesses a sharp postzygapophyseal lamina between the diapophysis and the postzygapophysis. This lamina is also present in dorsal vertebrae of Aetobarbakinoides and Desmatosuchus (Parker 2008; Desojo et al. 2012). The diapophyses are suboval in shape and its long axis is anteroposteriorly placed. The parapophysis is situated at the centrum just below the neural suture as seen in Desmatosuchus spurensis (MNA V9300; Parker 2008: fig 8C). The parapophysis is poorly pronounced and presents an oval form. In contrast, in Desmatosuchus spurensis this structure covers almost a quarter of the lateral side of the centrum (Parker 2008). Four disarticulated centra, probably proceeding from the anterior dorsal series, are present. These elements do not possess any distinctive difference from each other (Figs 9 g–l. 10) presenting the same characteristics of the other centra. The middle dorsal series is represented by three elements in which most structures are preserved (probably thirteenth, fourteenth, and fifteenth vertebrae) (Figs 11, 12). Their position in the dorsal series is tentative, based upon the location of their parapophyses, as in this region of the column they are placed on the transverse process. This feature is reported in all aetosaurs (Parker 2008).
The better preserved neural spine belongs to the putative 13th dorsal vertebra (Fig. 11). It is thin laterally and anteroposteriorly elongated, as in Desmatosuchus spurensis (Case 1922; Parker 2008). Its apex is partially broken, but it is possible to observe a well-marked lateral expansion of the neural spine. This expansion could be the socalled “spine table” typical of aetosaurs as in Desmatosuchus spurensis (MNA V9300; Parker 2008: fig 8). Both transverse processes are partially broken (Fig. 11). In dorsal view, the transverse process is trapezoidal and laterally projected. In lateral view, it is only possible to observe the diapophysis on both sides. The infradiapophyseal lamina is completely absent in dorsal vertebrae of Polesinesuchus. In contrast, these laminae are present in the middle dorsal axial elements of Aetosauroides (PVL 2073), Stagonolepis robertsoni (NHMUK R4784), Desmatosuchus spurensis (Parker 2008) and Typothorax coccinarum (Martz 2002), (Desojo & Ezcurra 2011; Desojo et al. 2012). This condition of Polesinesuchus is shared with Neoaetosauroides (PVL 3525) and the Stagonolepis olenkae (ZPAL AbIII 502/67) (Desojo & Ezcurra 2011). Furthermore, the infradiapophyseal fossa is absent in dorsal vertebrae of Polesinesuchus, as in Aetosauroides (MCP 13a–bPV) (Desojo & Ezcurra 2011). The neural spine is wide and posteriorly placed. Unfortunately, the apex of the neural spine is broken and its relationship with the centrum cannot be established.
The prezygapophyses are anteroposteriorly short and dorsally oriented, as in Aetosauroides (PVL 2073, MCP 13a–b PV), Stagonolepis robertsoni (Walker 1961), and Typothorax coccinarum (Martz 2002; Desojo & Ezcurra 2011). The longer axes of the prezygapophyses are lateromedial. Only the left postzygapophysis is preserved in the thirteenth vertebra. The hyposphene is absent in Polesinesuchus, the same condition found in Aetosauroides. In contrast, this structure is present in Aetobarbakinoides and Desmatosuchus (Parker 2008; Desojo et al. 2012). The postzygapophyseal lamina is present in the holotype, Aetobarbakinoides, and Aetosauroides (see Desojo & Ezcurra 2011; Desojo et al. 2012). Additionally, a circular pit (located in both sides of the neural spine and present in Aetobarbakinoides), is absent in Polesinesuchus and Aetosauroides (Desojo et al. 2012). Regarding the remaining dorsal vertebrae, their centra are amphicoelous and anteroposteriorly elongated, longer than the height of the anterior facet, with an length:height ratio of 1.42 (in Aetosauroides, 1.5: PVL2073), in the anterior dorsal of Stagonolepis robertsoni, 1.45: NHMUK R4784; Walker 1961; and in Sierritasuchus, 1.46: Parker et al. 2008: fig. 2g) (Desojo et al. 2012).
The fourteenth vertebra comprises a centrum and a partial neural arch, including the base of the left transverse process (Fig. 12 a–f). Only the left parapophysis and left prezygapophysis are preserved. The articular facet of the parapophysis is oval-shaped and placed on the transverse process. The prezygapophysis is similar to that one from the first dorsal vertebra. The centrum is amphicoelous, without a well-rimmed fossa. In dorsal view, the centrum is compressed (spool-shaped) as in Aetosauroides (MCP 13a–b PV) (Desojo & Ezcurra 2011). Its length is comparatively longer than the height of the anterior articular facet (length:height ratio = 1.33).
The fifteenth vertebra comprises a centrum with an open neurocentral suture, the base of the neural spine, a complete left transverse process, the diapophysis, and the parapophysis (Fig. 12 g–l). The diapophysis is ovalshaped and the parapophysis is anteriorly placed. In dorsal view, the transverse process is trapezoidal with an anteroposteriorly longer proximal end, as in Aetosauroides (PVL 2073; MCP 13a–b PV). The infradiapophyseal lamina is absent and the parapophysis is placed over the transverse process, reaching half of its length. As in many other centra described above, the centrum is longer than the height of the anterior articular facet with a length:height ratio of the 1.36. This element is amphicoelous and transversely compressed. Laterally, the wellrimmed fossa is absent.
Sacral vertebrae. The sacral vertebrae comprise two disarticulated centra, both amphicoelous and considerably more robust than those described for the dorsal series as seen in Desmatosuchus spurensis (Parker 2008), Stagonolepis robertsoni and Lucasuchus hunti (Walker 1961; Long & Murry 1995) (Fig. 13). Both anterior and posterior sides are wider than tall, as observable in sacral centra of Desmatosuchus supurensis, Lucasuchus hunti, and Stagonolepis robertsoni (Walker 1961; Long & Murry 1995; Parker 2008). These vertebrae possess slightly flattened anterior and posterior sides as in Typothorax coccinarum (TTUP 9214) and phytosaurs (Martz 2002). In lateral view, it is possible to observe both areas for articulation of the neural arches almost reaching the midline of the centrum as in Typothorax and Lucasuchus hunti (Long & Murry 1995; Martz 2002). However, in both sacral centra, these structures cover the dorsal half of the length of the centrum. A well-rimmed fossa is absent in Polesinesuchus, as in other sacral vertebrae of Aetosauroides scagliai (PVL 2073, PVL 2052), Neoaetosauroides engaeus (PVL 3525), Stagonolepis robertsoni (Walker 1961). In ventral view, both sacral centra are flattened and very broad as occurs in Desmatosuchus spurensis (Parker 2008) and other aetosaurs (e.g. Aetosauroides scagliai PVL 2073; Stagonolepis robertsoni).
Caudal vertebrae. Five disarticulated centra are preserved in the holotype. The first two are amphicoelous and longer than the height of the anterior articular facet (length:height ratio: 1.16) (Fig. 14). These elements are quite robust with oval-shaped articular facets. These facets form a thickened rim as in Desmatosuchus spurensis (Parker 2008). In ventral view, it is possible to observe a groove that is laterally limited by two ridges which anteriorly end in chevron facets as in Stagonolepis robertsoni (Walker 1961). In Polesinesuchus the ridges and grooves cover only the posterior half of the centrum. In contrast, in the anterior caudal element of Desmatosuchus spurensis the ridges extend throughout its entire length (Parker 2008). Laterally, the two first caudal centra are devoid of a lateral fossa. Two other centra belong to the middle caudal region. These elements present some degree of distortion and their lateral surfaces are broken (Fig. 15). The centra are longer than the anterior ones, with a length longer than the anterior articular facet (length:height ratio: 1.31). In ventral view, they present ridges with a groove in the anterior half of the centrum. As in the other caudal elements, lateral fossae are absent. The distal caudal region is represented by a single centrum (Fig. 16 m–r). This element is smaller when compared to the other caudal elements, but with the same morphology. It is longer than the anterior articular facet (length: height ratio: 2.33).
Shoulder Girdle. Both scapulae and coracoids of Polesinesuchus are preserved. The left elements are more complete than the right ones (Figs 16, 17). Both proximal and distal ends of the left scapula, as well as the scapular blade, are well-preserved. In contrast, in the right scapular blade both proximal ends and anterior margin are broken. The coracoids present comparatively different states of preservation. The right coracoid is broken. The left element is more complete, allowing its observation in detail. As usual for aetosaurs, the scapula is a slender element with a slight constriction along its center and expanded extremities. In lateral view, this bone is wide and slightly convex. Its anterior margin is, in comparison, sharper than the posterior. The posterior margin is thicker than the anterior one. Dorsoventrally, the scapular blade is thin, presenting a large anteroposterior expansion to support the suprascapular cartilage, which possibly becomes ossified in adult individuals (Walker 1961). The medial portion of the scapular blade is more expanded in comparison with of the condition found in Aetosauroides (PVL 2073). The ventral expansion presents a marked acromial process. It is thick and laterally placed as in Aetosauroides. In contrast, in Aetobarbakinoides (PVL 2073), Aetosaurus (SMNS 5770 S-2) and Neoaetosauroides (PVL 3525) this structure is less prominent (Desojo et al. 2012). According to Romer (1956) the articular process would serve as a point of attachment with the clavicle. Distally, the subacromial tuberosity delimits a shallow anteroposterior groove as in Aetosauroides. Conversely, in Aetobarbakinoides and Neoaetosauroides the subacromial tuberosity delimits a moderately deep subacromial depression (Desojo et al. 2012). Distally, the scapula shows an articular facet for accommodation of the coracoids. This articulation is lateromedially expanded towards dorsal region. Anteriorly, it is slender as in some basal archosaurs, such as Prestosuchus chiniquensis (Huene 1938) and Rauisuchus tiradentes (Lautenschlager 2008). The glenoid fossa is dorsolaterally projected as in Aetobarbakinoides (Desojo et al. 2012). Alongside the glenoid fossa there is a small process for the attachment of the triceps muscle as in Batrachotomus kupferzellensis (Gower & Schoch 2009).
Coracoid. The coracoids are laterally convex, medially concave, and longer than wide as in Aetosauroides (PVL 2073) (Casamiquela 1961). Proximally, they are thick, as they attach to the scapulae to form most of the glenoid, resembling Aetosauroides (PVL 2073) (Casamiquela 1961). Their glenoid shows a buttressed glenoid lip, as occurs in Typothorax coccinarum (Heckert et al. 2010). Posteriorly, these elements are also thick and rounded and, as usual, there is a neck below the glenoid. Dorsally, a posterior process is present. The coracoid foramen is quite visible in Polesinesuchus. This foramen is circular and relatively large. In contrast, Neoaetosauroides possesses a small foramen. In Polesinesuchus it is situated 7,8mm from the glenoid (Figs 16, 17). The subglenoid pillar, present in some aetosaurs, such as Typothorax coccinarum (Heckert et al. 2010), Stagonolepis robertsoni (Walker 1961: fig. 12) Neoaetosauroides, Lucasuchus, Desmatosuchus, Coahomasuchus and Aetosaurus (Bonaparte 1971; Long & Murry 1995), does not occur in Polesinesuchus, a condition shared with Aetosauroides scagliai (Casamiquela 1961).
Interclavicle. This blade-like shaped element is disarticulated from the coracoids (Fig. 18). It is an elongate element which is very thin anteriorly and becomes thick posteriorly forming a marked bulge, as seen in Typothorax coccinarum (Heckert et al. 2010). Ventrally, it is convex with its anterior end possessing two small articular facets separated by a tall crest as occurs in Aetosauroides scagliai (PVL 2073) and Stagonolepis robertsoni (Casamiquela 1961; Walker 1961). Walker (1961) described the articular facets as anterolateral pits to receive the medial process from the clavicles. This element is anteroposteriorly expanded. In Polesinesuchus its posterior end is well ossified and partially broken, with a total length of 44.5 mm in comparison to Aetosauroides (PVL 2073: 64mm) (Schoch 2007).
Humerus. A fragmentary right humerus and just parts of the left one were recovered for Polesinesuchus. The right element presents transversal fractures (close to its distal extremity) across the diaphysis. The left element comprises both proximal and distal epiphyses. Its diaphysis is missing (Figs 19, 20). The right humerus is long and relatively robust, with both proximal and distal ends transversally expanded, and a robust diaphysis. It measures about 1.2 times the length of the ulna (this ratio resembles that of Aetosaurus ferratus) (Schoch 2007). In contrast, in Aetosauroides (PVL 2073), Aetobarbakinoides, Desmatosuchus haplocerus (UCMP A 269/32168; Long & Murry 1995) and Typothorax coccinarum (UCMP V 2816 /34240; Long & Murry 1995) the humeral diaphysis is a lot narrower than the two expanded ends of this bone. The humeral head is prominent and presents a convex articular surface as in Aetobarbakinoides (Desojo et al. 2012). The larger tuberosity is poorly defined, as occurs in Aetosauroides (PVL 2052, 2073; PVSJ 326), Neoaetosauroides (PVL 3525), Stagonolepis robertsoni (Walker 1961) and Typothorax (UCMP V 2816 /34240; Long & Murry 1995; Martz 2002). This structure is comparatively more conspicuous in posterior view as in Typothorax and other basal archosaurs (UCMP V 2816 /34240 Long & Murry 1995; Martz 2002). A prominent, large tuberosity is present in Aetobarbakinoides brasiliensis and “ Argentinosuchus bonapartei ” (nomen dubium, an indeterminate aetosaur according to Desojo & Ezcurra [2011]) (Desojo et al. 2012). The later authors described two tuberosities in the humeral head of Aetobarbakinoides. The first one situated in the lateroventral corner and the second in the dorsal margin of the humeral head. In Polesinesuchus these structures are either poorly developed or absent. The deltopectoral crest is poorly developed ventrally and subtriangular in medial view. This condition is shared with other pseudosuchian, such as the “rauisuchian” Batrachotomus and the aetosaur Aetosauroides scagliai (Desojo et al. 2012). The distal end presents two ventrally placed condyles: laterally, the ectepicondyle and, medially, the entepicondyle. These two condyles are rounded and separated by a medial groove. In the dorsal surface of the distal end there is a shallow subtriangular depression as in Aetobarbakinoides brasiliensis (CPE2 168). In lateral view, a distal deep groove is also present (ectepicondylar groove: Schoch 2007). Along this groove there is a dorsal ridge, probably to accommodate blood vessels and the radial nerve (Romer 1956), similarly to the condition present in several aetosaurs, such as Aetobarbakinoides brasiliensis (CPE2 168), Aetosauroides scagliai (PVL 2073; PVSJ 326), Neoaetosauroides engaeus (PVL 3525), Stagonolepis robertsoni (Walker 1961) (Desojo et al. 2012), and contrasting with a foramen/fossa in Typothorax coccinarum (Heckert et al. 2010) and Desmatosuchus haplocerus (TTU 9170; Small 2002).
Ulna. Two well-preserved ulnae are present in Polesinesuchus, both presenting a slight fracture in their shafts (Fig. 21). They are lateromedially compressed with a slightly expanded and anteroposteriorly twisted proximal end, which is wider than the distal one in comparison, as in Neoaetosauroides engaeus (Desojo & Baéz 2005) and Longosuchus meadei (Sawin 1947). Its olecranon is poorly-developed. In contrast, this structure is well-developed in Coahomasuchus kahleorum (Heckert & Lucas 1999), Aetosauroides scagliai (PVL 2073) (Casamiquela 1961: fig. 11–13), Neoaetosauroides engaeus (Desojo & Baéz 2005), Longosuchus meadei (Sawin 1947), and Aetosaurus (Schoch 2007). It is probable that the olecranon of Polesinesuchus olecranon would be filled with cartilage, which is suggested by its poorly observable prominence. Also, it presents a gentle angle contrasting with the L-shaped one observed in Typothorax coccinarum (Heckert et al. 2010). In ventral view, the articular surface is oval-shaped as in Typothorax coccinarum (Heckert et al. 2010).
Ilium. Only the left ilium is preserved in Polesinesuchus. Its iliac blade is long, dorsoventrally short, with two processes (one anterior and other posterior). Its outline resembles that of Desmatosuchus haplocerus (UMMP 73322), (Long & Murry 1995) and Desmatosuchus spurensis (Parker 2008: fig. 6C) (Fig. 22). In lateral view, the blade is proportionally lower than the iliac blade of Aetosaurus ferratus (Schoch 2007: S-20), Typothorax coccinarum (UCMP V2816 122683 70/Fa54) and Stagonolepis robertsoni (Walker 1961; Martz 2002; Schoch 2007). In Typothorax coccinarum, the iliac blade is tall and shows, in both sides, two transversal buttresses above the acetabulum, that is expressed as a strong thickening (Heckert et al. 2010). This feature does not occur in the iliac blade of Polesinesuchus. The anterior process of the iliac blade is short, slightly exceeding the pubic peduncle, a condition shared with Neoaetosauroides engaeus (PVL 3525), Longosuchus meadei (TMM 31185) and Desmatosuchus spurensis. The tip of the anterior process is very slender with an oblique anteroventral direction as in Aetosaurus ferratus and Desmatosuchus haplocerus (Long & Murry 1995; Schoch 2007), and longer than in Aetosauroides scagliai (PVL 2073). Additionally, the tip of the anterior process is also very pointed when compared with the rounded one present in Aetosauroides scagliai (PVL 2073; PVL 2052). The anterior process of the iliac blade serves as the insertion area for iliotibialis and iliofemurales muscles, both directly related to the movement of hindlimbs (Desojo & Baéz 2005). The posterior process is long and massive. In dorsal view, the iliac blade presents a ripple in its distal end. Additionally, the posterior process is mediolaterally inclined, differently from the anterior process. This condition is shared with Typothorax coccinarum (Heckert et al. 2010). The acetabulum is a non-perforated shallow concavity. It is almost entirely formed by the ilium and delimited by a supracetabular crest that forms an overhanging ridge to accommodate the head of the femur as occurs in Desmatosuchus spurensis (Parker 2008). Ventrally, the ilium expands and ends in two articular surfaces.
Pubis. Represented by fragments of both pubial elements (Fig. 23). The left pubis preserves both proximal and distal ends, so the medial region is missing. The right pubis only preserves its proximal end. Walker (1961) described two foramina in the pubis of Stagonolepis robertsoni, but these structures are not visible in Polesinesuchus, as most of the aetosaurs. The proximal end presents the characteristic twist, a condition present in several pseudosuchian archosaurs (Walker 1961). The pubis is a short element in which the proximal end is stronger than the distal one in comparison, which presents a massive rugosity. A short pubis is also present in Aetosaurus ferratus (Schoch 2007). In contrast, a longer pubis is present in Stagonolepis robertsoni and Desmatosuchus spurensis (Walker 1961; Schoch 2007; Parker 2008). The left proximal end is comparatively better preserved and allows the recognition of some structures. For instance, the articular surface for the ilium is almost flat and “U” shaped. Anteroposteriorly, the articular surface is long as occurs in Neoaetosauroides engaeus and other basal archosaurs (Lecuona & Desojo 2011). Medially, there is a bony tongue with a groove over its sagital length. This structure is a thin proximal portion of bone for the obturador foramen, which in Polesinesuchus is difficult to observe due to its poor preservation. This tongue-like structure is reported only for Postosuchus kirkpatricki Chatterjee, 1985 (Long & Murry 1995: fig. 135) and Gracilisuchus stipanicicorum Romer, 1972 (Lecuona & Desojo 2011: fig. 4). Parts of the proximal end of the pubis are broken, but there is some evidence of the presence of the obturator foramen. A portion of the distal end of pubis is preserved in the left element. It is constituted by a very thin lamina which becomes thicker distally to form a prominent pubic foot. Distally, the pubic foot of Polesinesuchus shows a marked rugosity as occurs in Typothorax coccinarum and Stagonolepis robertsoni (Walker 1961; Martz 2002). Additionally, Parker (2008) described (for the distal end) a club-like end in Desmatosuchus spuresis, but stated that this structure is probably homologous to the pubic foot of other suchians. This feature is usual in aetosaurs, phytosaurs and sphenosuchians (Gower & Schoch 2009).
Ischium. Only the left ischium is preserved in Polesinesuchus, in which most structures are preserved (Fig. 23). It is L-shaped with the proximal end wider than the distal one in comparison. The proximal end is also thicker than distal, possessing two articular surfaces: one medial and other lateral. The medial articular surface is almost flat, smaller in comparison, and articulates with the posteroventral articular surface of the ilium. The lateral articular surface contributes to the ventral margin of acetabulum. It is larger and almost oval-shaped. The anterior margin of the ischium is very thin and it is partially broken in Polesinesuchus. It forms the puboischiatic plate. Distally, the ischium becomes posteriorly expanded and shows a curvature medial to the symphysis. Apparently, the symphysis is distributed along the length of the ischial shaft as in Aetosauroides scagliai (PVL 2073, PVL 2052), Typothorax coccinarum, Stagonolepis robertsoni, and many aetosaurs and pseudosuchian archosaurs as well (Walker 1961; Heckert et al. 2010; Lecuona & Desojo 2011; Nesbitt 2011).
Femur. Both femora are present and well-preserved in the holotype. They are robust, with a typical sigmoid shape as in Aetosauroides scagliai (PVL 2073) and most archosaurs (Nesbitt 2011), (Figs 24, 25). However, in the femora of Polesinesuchus, the extremities are slightly twisted along the axial length in comparison with those of Aetosauroides scagliai (PVL 2073). The distal end is anteroposteriorly twisted counterclockwise (to the left) in comparison to the proximal end. Additionally, the femoral shaft is oval in cross section, as seen in Typothorax coccinarum, Stagonolepis robertsoni and Aetosaurus ferratus (SMNS 57771), (Walker 1961; Schoch 2007; Heckert et al. 2010). Probably this feature is related to the type of insertion of the femur, due to the ventral position of the acetabulum (Desojo & Baéz 2005). The femoral head is medially displaced for connection to the acetabulum. The greater trochanter is slightly developed. Medially and below the greater trochanter there is a strong ridge that ends almost over the fourth trochanter. This ridge is accompanied by a similar sized longitudinal concave area. In the proximal femoral lateral surface there is another ridge, but low and poorly-developed in comparison. In dorsal view, the proximal end of the femur presents in its articular surface an anteroposterior groove. The fourth trochanter of Polesinesuchus is very high and forms a prominent crest, as reported in Aetosauroides scagliai and Calyptosuchus wellesi. In contrast, the fourth trochanter of Aetosaurus ferratus presents a longitudinal bulge that forms a low platform. Moreover, Stenomyti huangae also show a low fourth trochanter (Schoch 2007; Martz & Small 2013). These trochanters function as an insertion area for the M. caudifemoralis longus (Lecuona & Desojo 2011). The distal end of the femur presents two ventral condyles. The medial one articulates with the tibia and the lateral attaches with the fibula. These condyles are separated by a longitudinal intercondylar groove for attachment of the M. quadriceps femorallis.
Tibia. A complete left tibia and a proximal end of the right element are preserved Polesinesuchus, both in a good degree of preservation (Fig. 26). The tibia is a strong bone (Its length is 1.2 times the femur) with expanded extremities, the proximal wider than the distal one in comparison. The tibia of Aetobarbakinoides brasiliensis is gentle in comparison with that of Polesinesuchus (length:width ratio = 10). The expansion of the proximal end of the tibia in aetosaurs is wider than those in non-aetosaur pseudosuchians (Parrish 1986; Martz 2002). However, in Aetosaurus ferratus both extremities of the tibia present almost the same width, contrasting with those of Stagonolepsis robertsoni, Aetosauroides scagliai, Neoaetosauroides engaeus, Typothorax coccinarum, and Desmatosuchus (Schoch 2007). The shaft presents a posteriorly projected curve, as in Aetobarbakinoides brasiliensis (CPE2 168) and Aetosauroides scagliai (PVL 2073). Tibia and fibula have almost the same length (1.2 times the femoral length). The shaft is lateromedially flattened and presents a slightly bowing towards its length. Laterally, the tibial shaft presents a longitudinal edge, as in Aetobarbakinoides brasiliensis (CPE2 168). Dorsally, the proximal extremities form two articular surfaces for articulation with the femoral condyles. The distal end has an expanded and slightly elliptic outline which presents two ventral condyles, both forming two divided facets for the astragalus, as occurs in Typothorax coccinarum and also in other non-aetosaur pseudosuchians (Martz 2002).
Fibula. Both elements are preserved in Polesinesuchus. They are deformed and damaged in some extent. These elements are gentle, measuring almost the same length of the tibia which attains 1.25 times the femur (Figs 27, 28). In contrast, Stagonolepis robertsoni, Desmatosuchus smalli, and Longosuchus meadei (length:width ratio = 6.4) show the fibula stronger than the Polesinesuchus´s (length:width ratio = 9.6) (Sawin 1947; Walker 1961; Long & Murry 1995). Both proximal and distal ends are slightly transversely expanded and connected by a slender shaft. In the anterolateral surface of the shaft there is a prominent crest-like iliofibularis trochanter, which is longitudinally longer than in Aetosauroides scagliai (PVL, 2073). Additionally the crest-like iliofibularis trochanter of Polesinesuchus differs from the double trochanter of Longosuchus meadei (Sawin 1947). Additionally, in Stenomyti huangae the iliofibularis trochanter is also well developed (Small & Martz 2013). In contrast, in juvenile specimens of Aetosaurus ferratus, this structure is less pronounced than in all remaining aetosaurs (Schoch 2007). A huge iliofibularis trochanter is described for Desmatosuchus haplocerus (UCMP A269/32392) and Typothorax coccinarum (UCMP V2816 34248 70/G6), but in this last taxon it is placed almost halfway in the shaft (Long & Murry 1995). The distal end of the fibula presents two articular facets, one for the calcaneum (which is larger than the one for the astragalus) and one for the astragalus, which is smaller in comparison.
Tarsus and pes. Both proximal tarsals, astragali and the right calcaneum are preserved in Polesinesuchus. A few elements from the pes are preserved in the holotype: two complete metatarsals (probably III and V) and fragmentary elements of other metatarsals, phalanges. The crurotarsal ankle joint of Polesinesuchus is typical “crocodile-normal” as in pseudosuchian archosaurs, except in ornitosuchids (e.g. Sereno & Arcucci 1990). This articulation consists in the rotary ankle joint in which the proximal tarsals move against each other with a peg-andsocket articulation (Parrish 1986; Brochu 2001).
Astragalus. It is a massive bone that presents two articular facets (fibial and tibial) in its proximal region (Fig. 29). These articulations are separated by a thick crest which forms an acute angle among them. In Gracilisuchus stipanicicorum these facets are divided by a sharp crest (Lecuona & Desojo 2011). The tibial facet is subdivided into two facets by a small elevation and larger in comparison, occupying almost entirely the proximal region of the bone. Its anterior articular surface is strongly concave, whereas the posteromedial one is almost flat. These two facets diverge to form the screw-joint articulation for the tibia. Diverging facets are also related in other aetosaurs, such as Neoaetosauroides engaeus (PVL 3525) and Calyptosuchus wellesi (Long & Ballew 1985: fig. 82; Lecuona & Desojo 2011). Anteriorly, there is a poorly prominent astragalar hollow, which does not contact the distal hollow. According to Martz (2002), a small foramen located in the hollow is present in Desmatosuchus and Alligator mississippiensis, but not evident in Typothorax coccinarum. Also, this foramen is not observable in Polesinesuchus. The distal hollow is large and articulates with metatarsals I, II and the third distal tarsal. In lateral view, three articular surfaces for the calcaneum are present, two forming the astragalar peg as in Gracilisuchus stipanicicorum (Lecuona & Desojo, 2011), Typothorax (NMMNH P-36075; Lucas et al. 2002), Stagonolepis robertsoni (Walker 1961), Aetosauroides (Casamiquela 1961) and Coahomasuchus (Heckert & Lucas 1999).
Calcaneum. It is also a robust element with a wide shaft and a slight dorsoventral compression (Fig. 29). The calcaneal condyle is very prominent. Dorsally, it presents a concave surface that forms the area that receives the fibula in its lateral half, through a sliding articulation. The astragalus articulates with the condyle in its medial length as occurs in Gracilisuchus stipanicicorum (Lecuona & Desojo 2011). Ventral to the calcaneal condyle, there is a compressed tuber which serves for the attachment of the gastronemeus muscle (Martz 2002). This tuber is more prominent in Neoaetosauroides engaeus (Desojo & Baéz 2005). Between the calcaneal condyle and the calcaneal tuber, Polesinesuchus displays a well-marked notch as occurs in Aetosauroides scagliai (PVL 2052) and Gracilisuchus stipanicicorum (Lecuona & Desojo 2011). In the posterior surface of the tuber of Polesinesuchus there is the so-called shallow medial groove, which holds the tendon of the M. gastrocnemius externus reported in Gracilisuchus and other aetosaurs. Distally, the surface of the calcaneal condyle is flattened and contacts the fourth distal tarsal. Below this surface, there is a deep fossa in Polesinesuchus, as in Typothorax coccinarum (Martz 2002). However, in the former this fossa is “U”-shaped, differently from Typothorax. In lateral view, other smaller oval fossa (in comparison with the distal calcaneal fossa) is present. Medially, the condyle of the calcaneum displays a deep socket which is dorsally supported by a protruding lip as in Typothorax coccinarum (Martz 2002). This socket receives the peg of the astragalus, the typical articulation of the crocodile normal type of tarsus.
Metatarsal III. It is a relatively long bone with expanded ends (Length 2.25 times the fibula). The proximal end is dorsoventrally compressed and more expanded than the distal one in comparison (Fig. 30). Unfortunately, the proximal end shows fractures that difficult the recognition of some structures. Nonetheless, in the proximal end, the degree of expansion is longer than in Aetobarbakinoides brasiliensis. According to Desojo et al. (2012), in this taxon the degree of expansion of the proximal end is lesser than in Neoaetosauroides engaeus (PVL 3525), Aetosaurus ferratus (Schoch 2007), Stagonolepis robertsoni (Walker 1961), and Typothorax coccinarum (Heckert et al. 2010). The shaft towards the distal end becomes thinner. Distally, the shaft presents a slight twist, as seen in Postosuchus alisonae (UNC 15575) and Aetobarbakinoides (Peyer et al. 2008; Desojo et al. 2012).
Metatarsal V. Medially, the proximal articular surface forms a small condyle, and its proximal end is quite expanded, with the articular surface strongly concave (Fig. 31). The proximal articular surface possesses small foramina and ligament attachment marks. Medially, the proximal end shows a slight expansion as occurs in Aetobarbakinoides (Desojo et al. 2012). In contrast, Neoaetosauroides engaeus shows a typical archosauromorph hook-like shape medially in its proximal end (Desojo & Báez 2005). Additionally, in Aetosaurus (Schoch 2007), Stagonolepis (Walker 1961), and Typothorax (Heckert et al. 2010) this structure is also prominent (Desojo et al. 2012). In Aetosaurus this expansion of the proximal end is smaller than in Stagonolepis (Walker 1961; Schoch 2007). The distal end is less expanded than the proximal one, contrasting with the distal end of the Aetobarbakinoides, in which the distal end is more transversely expanded and robust than the proximal one (Desojo et al. 2012). The lateral surface is also similar to that of many archosauromorphs where the shaft is compressed and tall. This characteristic is exemplified in Typothorax coccinarum (UCMP V2816 /34255; Long & Murry 1995; NMMNH P-56299; Heckert et al. 2010).
Phalanges. Two phalanges are present. In both, the proximal and distal ends are wide (Fig. 32). The first phalanx (Fig. 32 a) is longer in comparison with the second, presenting a dorsoventrally compressed distal end. Laterally, there are small pits in both sides. The anterior articular surface is trapezoidal and more expanded in comparison. The second element (Fig. 32 b) is shorter than the first one, robust, and resembles the first element of the fourth digit of the Aetobarbakinoides (Desojo et al. 2012). Its distal end is dorsoventrally higher and the pits are larger in comparison. Furthermore, this element shows the typical developed ginglymous articulation in archosaurs. According to these features, it is quite possible to infer that this element proceeds from the four digit of the pes (see Desojo et al. 2012).
Ungual phalanges. They are quite curved and lateromedially compressed, with strongly sharp tips (Fig. 32 e– g). In both sides, close to distal end, there are grooves for blood vessels (Martz 2002). The morphology these elements are very similar to those from other aetosaurs as Neoaetosauroides engaeus (PVL 3525), Aetobarbakinoides brasiliensis (CPE2 168), Aetosauroides scagliai (PVL 2052) and Typothorax coccinarum (Desojo & Baéz 2005; Desojo et al. 2012; Heckert et al. 2010).
Dorsal paramedian osteoderms. Three elements are present (Fig 33 a–c). The osteoderm A is subrectangular in dorsal view and wider than long (a width:length ratio of about 2.76), (Fig. 33). This ratio is higher than in Aetobarbakinoides (1.96). Unfortunately, this element is quite damaged. Even so, on the external surface there is an anterior bar with a small elevation devoid of ornamentation. This bar becomes anteroposteriorly longer towards the lateral edge as in Aetosauroides scagliai (MCP 13-a–b PV), (Desojo & Ezcurra 2011). The lateral edge is partially broken but permits the observation of an anterolateral projection as occurs in a large specimen of Aetosaurus ferratus (SMNS 12670: Schoch 2007). In Polesinesuchus this projection is comparatively lower and its medial edge is not projected. Posteriorly, the paramedian osteoderms of Polesinesuchus present a strong ventral flexion as occurs in typothorascisine and desmatosuchine aetosaurs (Parker 2007; Desojo et al. 2012). The ornamentation consists of irregular circular pits and ridges with a radial pattern projecting from the dorsal eminence, as occurs in Aetosauroides scagliai (PVL 2073; MCP 13-a–b PV), Aetobarbakinoides brasiliensis (CPE2 168) Neoaetosauroides engaeus (PVL 3525), Aetosaurus ferratus (Schoch 2007), Lucasuchus hunti, Paratypothorax andressi (Long & Murry 1995), Coahomasuchus (Heckert & Lucas 1999) Stagonolepis robertsoni (NHMUK R4788), and Calyptosuchus wellesi (Long & Murry 1995), (Desojo & Ezcurra 2011; Desojo et al. 2012). However, the overall ornamentation of paramedical osteoderms of Polesinesuchus shows poor density. In small specimens of Aetosauroides scagliai this fact is probably attributed to its juvenile ontogenetic stage (Desojo & Ezcurrra 2011), the same situation of Polesinesuchus. In contrast, Typothorax (Long & Ballew 1985), Redondasuchus (Heckert et al. 1996), and Chilenosuchus (Desojo 2003) present a reticular distribution of ornamentation (Desojo & Ezcurra 2011; Desojo et al. 2012). Furthermore, the random pattern is observed in Desmatosuchus smalli, Desmatosuchus spurensis, Longosuchus and Acaenasuchus (Long & Ballew 1985; Parker 2005, 2008, Parker & Martz 2010; Desojo et al. 2012). The dorsal eminence is posteromedially displaced, incipient, and does not contact the posterior edge, as occurs in Aetosauroides scagliai (MCP 13-a–b PV), (Desojo & Ezcurra 2011). An incipient dorsal eminence occurs also in Aetobarbakinoides brasiliensis (CPE2 168), Typothorax coccinarum, and Redondasuchus reseri (Long & Ballew 1985; Heckert et al. 1996). The ventral view cannot be assessed, due the resin used for reinforce the structure of the osteoderm before the description of the Polesinesuchus. Due to these characteristics, osteoderm A probably belongs to the left posterior cervical or to the anterior dorsal region of the armor. Desojo & Ezcurra (2011) claim that the pitting density in cervical and dorsal osteoderms presents differences according to their position in the armor (e. g. a diminution of density towards the sacral region).
The osteoderm B comes from the right transverse segment and presents almost the same characteristics of the osteoderm A but, differently, its width:length ratio is 2.15 (Fig. 33). Its lateral ridge shows a rounded distal half, the ornamentation is more conspicuous, and the dorsal eminence forms an anteroposteriorly displaced ridge. Due to the density of the ornamentation in osteoderm B, this element is probably more anteriorly placed than A.
The ornamentation of osteoderm C is distinct. In dorsal view, the ridges and pits are deeper in comparison with those from osteoderms A and B. In the medial region, the small pits merge, increasing their size and being surrounded by anastomosed ridges (Fig. 33). In posterior view, the osteoderm C is not flexed. According to this pattern, this element was probably placed close to sacral region. (Taborda, personal communication, 2012). Due to the position of its dorsal eminence, that is medially displaced, this element proceeds from the right side of the armor.
Ventral osteoderms. Seven elements are present in Polesinesuchus (Fig. 34). They are almost squared, slightly curved transversely, and wider than long as occurs in Aetosauroides scagliai (MCP 13a–b PV. Desojo & Ezcurra 2011), Typothorax coccinarum (TTUP9214, fig.4.40a; Martz 2002), Coahomasuchus (Heckert & Lucas 1999), and Stagonolepis robertsoni (Walker 1961; Heckert & Lucas 2000, 2002). The anterior bar is welldeveloped, without ornamentation. The pattern of ornamentation consists of pits and grooves in a radial fashion, starting from the center of the osteoderm, as in Aetosauroides scagliai (Desojo & Ezcurra 2011). Among the preserved elements, four are still enclosed in the matrix, imbricated to each other, which shows their original disposition in the ventral armor. They are slightly flexed in posterior view.
description: Published as part of Roberto-Da-Silva, Lúcio, Desojo, Julia B., Cabreira, Sérgio F., Aires, Alex S. S., Müller, Rodrigo T., Pacheco, Cristian P. & Dias-Da-Silva, Sérgio, 2014, A new aetosaur from the Upper Triassic of the Santa Maria Formation, southern Brazil, pp. 240-278 in Zootaxa 3764 (3) on pages 242-272, DOI: 10.11646/zootaxa.3764.3.1, http://zenodo.org/record/251763