Figure 1
Reconstruction of the Brazilian aetosaurs Aetosauroides, Aetobarbakinoides and Polesinesuchus (without osteoderms and gastralia), and respective schematic drawing of a trunk vertebra in lateral view (not to scale). Colored bone elements are those available on each specimen. Black arrows indicate important characters found in Aetosauroides, the infradiapophyseal laminae at the neural arch and the marked lateral fossa at the centra. Specimen size obtained relative to their femur circumference (see Taborda et al. 2013TABORDA JRA, CERDA IA & DESOJO JB. 2013. Growth curve of Aetosauroides Casamiquela 1960 (Pseudosuchia: Aetosauria) inferred from osteoderm histology. In: Nesbitt SJ, Desojo JB & Irmis RB (Eds), Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin, Geological Society, London, Special Publications. 379. Bath: The Geological Society Publishing House, p. 413-424.) and trunk vertebrae length (this study).
Figure 2
Associated aetosaur individuals and maps of Candelária Sequence outcrops. a, association of three aetosaur Aetosauroides (MCP-3450-PV, UFRGS-PV-1514-T and UFSM 11070) and at least one Hyperodapedon sanjuanensis (UFRGS -PV-1302-T). b, interpretative drawing. c, Faixa Nova Area with highlighted collected specimens. d, São João do Polêsine Area, with highlighted collected specimens in Piche and Buriol outcrops. Dots reveal studied specimens. Dark areas in the maps indicate the outcrops, green areas fragments of vegetation and blue lakes. Abbreviations: As, Aetosauroides (aetosaur); Bu, Buriolestes (dinosaur); Hy, Hyperodapedon sp. (rhynchosaur); Hs, Hyperodapedon sanjuanensis (rhynchosaur); Hm, Hyperodapedon mariensis (rhynchosaur); Ix, Ixalerpeton (lagerpetid); Pa, Polesinesuchus (aetosaur); Pr, Prozostrodon (cynodont); Sa, sauropodomorph indet. (dinosaur); Th, Therioherpeton (cynodont); Ts, Teyumbaita (rhynchosaur).
Figure 3
Cervical vertebrae of Aetosauroides (MCN-PV 2347 and UFSM 11070) and Polesinesuchus (ULBRAPV003T). a, left atlas neural arch and atlas intercentrum of MCN-PV 2347 in lateral (a1) and anterior views (a2). b, axis and third vertebra in lateral (b1) and ventral view (b2). c, third vertebra of MCN-PV 2347 in anterior (c1) and posterior views (c2). d, axis of MCN-PV 2347 in anterior (d1) and posterior views (d2). e, complete fourth (?) cervical vertebrae of Polesinesuchus type material in anterior (e1), lateral (e2) and ventral views (e3). f, cervical centra of Aetosauroides UFSM 11070 in anterior (f1) and in left lateral views (f2). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; ai, axis intercentrum; b., broken; da, diapophysis; epi, epipophysis; la, lamina; lfo, lateral fossa; na, neural arch; nc, neural canal; ns, neural spine; odp, odontoid process; ost, osteoderm; pa, parapophysis; pas, posterior articular surface; prez, prezygapophyses; psfo, postspinal fossa; posz, postzygapophyses; ra, articular facet for the atlas rib; vk, ventral keel.
Figure 4
Last cervical and anterior trunk vertebrae of Aetosauroides (MCP-3450-PV). Probable transitional vertebrae isolated neural arch in anterior (a), dorsal (b), posterior (e), left lateral (f) and right lateral views (g); with interpretative drawings of the anterior (c) and dorsal (d) views. Compatible isolated centra, in posterior (e) and ventral view (h). Putative last cervical vertebra in lateral (i) and ventral views (j). Arrow indicates anterior direction. Abbreviations: aifo, anterior infradiapophyseal fossae; b., broken; da, diapophysis; f.ncs, facet of the neurocentral suture; ilfo, incipient lateral fossae of the centrum; izpl, intrapostzygapophyseal lamina; mifo.sfo, middle infradiapophyseal fossa with sub-fossa; na, neural arch; nc, neural canal; ns, neural spine; p, pillar-like ridge; pa, parapophysis; pas, posterior articular surface; pd, neural arch peduncle; pdl, paradiapophyseal lamina; pit, deep pit lateral to the neural spine; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; vk, ventral keel.
Figure 5
Anterior trunk vertebrae of Aetosauroides (UFSM 11070). a, detail of the drop-shaped spine table, in dorsal view. b, anterior trunk articulated series in dorsal view, and its interpretative drawing (c). d, detail of the heart-shaped spine table, in dorsal view. e, anteriormost preserved trunk neural arch in anterior view and interpretative drawing (f). Abbreviations: aifo, anterior infradiapophyseal fossae; azdl, anterior zygodiapophyseal lamina; da, diapophysis; la, lamina; nc, neural canal; ns, neural spine; ost, paramedian osteoderm fragment; pa, parapophysis; pit, deep pit lateral to the neural spine; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; posz, postzygapophyses; psfo, post-spinal fossa; st, spine-table; tp, transverse process; Tv, trunk vertebra; vb, ventral bar.
Figure 6
Mid- and posterior trunk vertebrae of Aetosauroides (UFSM 11070). a, articulated series of mid- to posterior trunk vertebrae in dorsal view and interpretative drawing (c). b, detail of the heart-shaped spine table, in dorsal view. d, detail of the lateral pit with foramina present. Abbreviations: ca, capitulum; da, diapophysis; gap, groove separating the parapophysis from the diapophysis; izpl, intrapostzygapophyseal lamina; lost, lateral osteoderm; mlfo, wel-rimmed lateral fossae of the centrum; ncs, neurocentral suture; ost, paramedian osteoderm fragment; p, pillar-like ridge; pa, parapophysis; pit, deep pocket pit lateral to the neural spine; pit.f, deep pocket pit lateral to the neural spine with foramina; prez, prezygapophyses; psfo, postspinal fossa; posz, postzygapophyses; st, spine-table; tp, transverse process; tu, tuberculum; Tv, trunk vertebra.
Figure 7
Details of the mid- to posterior trunk vertebrae of Aetosauroides (UFSM 11070). a, sixth trunk vertebra (Tv6) in lateral (a1) and posterior (a2) views. b, seventh to ninth posterior trunk vertebrae (Tv7-9) in lateral (b1) and ventral (b4) views, with interpretative drawing in lateral view (b3). c, tenth trunk vertebra (Tv10) detail of the neural spine and postzygapophysis, in posterior view. d, eleventh and twelfth trunk vertebrae (Tv11-12) in posterolateral view (d). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; acdl, anterior centrodiapophyseal lamina; aifo, anterior infradiapophyseal fossae; ao, appendicular osteoderm; b., broken da, diapophysis; fs, flat ventral surface; ilfo, incipient lateral fossae of the centrum; izpl, intrapostzygapophyseal lamina; la, lamina; mifo, middle infradiapophyseal fossa; mlfo, wel-rimmed lateral fossae of the centrum; na, neural arch; nc, neural canal; ncs, neurocentral suture; pa, parapophysis; pas, posterior articular surface; pcdl, posterior centrodiapophyseal lamina; pifo, posterior infradiapophyseal fossa; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; psfo, post-spinal fossa; st, spine-table; tp, transverse process; Tv, trunk vertebra.
Figure 8
Anterior trunk vertebrae of Aetosauroides (MCP-3450-PV). Two articulated vertebrae of MCP-3450-PV in dorsal (a), ventral (c) and right lateral (d). Interpretative drawings of the dorsal (b) and right lateral (e) views. Arrow indicates anterior direction. Abbreviations: ab, anterior bar of the osteoderm; aifo, anterior infradiapophyseal fossae; d, depression; da, diapophysis; de, dorsal eminence of the osteoderm; dpto, dorsal paramedian trunk osteoderm; fs, flat ventral surface; ilfo, incipient lateral fossae of the centrum; izpl, intrapostzygapophyseal lamina; la, lamina; mifo, middle infradiapophyseal fossa; ncs, neurocentral suture; ns, neural spine; p, pillar-like ridge; pa, parapophysis; pcdl, posterior centrodiapophyseal lamina; pdl, paradiapophyseal lamina; pe, posterior expansion of the rib; pifo, posterior infradiapophyseal fossa; pit, deep pit lateral to the neural spine; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; psfo, post-spinal fossa; Tv, trunk vertebra.
Figure 9
Trunk vertebrae of Aetosauroides (MCP-3450-PV). a, the last vertebrae of Figure 9 in posterior view. b, subsequent trunk vertebra in anterior (b1), dorsal (b2), right lateral (b3), dorso-lateral (b4), ventral (b5) views. c, detail of the isolated triangular spine-table, in dorsal view. d, isolated trunk vertebra in lateral (d1) and ventral views (d2). e, isolated trunk vertebra in lateral (e1) and ventral views (e2). f, isolated trunk vertebra in lateral (f1) and ventral views (f2). g, isolated trunk vertebra in lateral (g1) and ventral views (g2). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; acdl, anterior centrodiapophyseal lamina; aifo, anterior infradiapophyseal fossae; b, broken; d, depression; da, diapophysis; fs, flat ventral surface; ilfo, incipient lateral fossae of the centrum; izpl, intrapostzygapophyseal lamina; la, lamina; nc, neural canal; np, notochordal pit; odp, odontoid process; ost, paramedian osteoderm fragment; p, pillar-like ridge; pa, parapophysis; pas, posterior articular surface; pcdl, posterior centrodiapophyseal lamina; pifo, posterior infradiapophyseal fossa; pit, deep pit lateral to the neural spine; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; psfo, post-spinal fossa ; st, spine-table.
Figure 10
Details of the trunk vertebrae of Polesinesuchus (ULBRAPV003T) and a small-sized Aetosauroides specimen (MCP-13-PV). Trunk vertebrae of ULBRAPV003T in anterior (a), right lateral (b), ventral (c), posterior (d), anterolateral (e) and its interpretative drawing in anterolateral view (f). The same vertebra, viewed from the left lateral side (g), scaled with the trunk series of the specimen MCP-13-PV in lateral (h) and posterior view (i). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; acdl, anterior centrodiapophyseal lamina; aifo, anterior infradiapophyseal fossae; b., broken; ilfo, incipient lateral fossae of the centrum; izpl, intrapostzygapophyseal lamina; la, lamina; mifo, middle infradiapophyseal fossa; nc, neural canal; ncs, neurocentral suture; ns, neural spine; npr, rudiments of the notochordal pit; p, pillar-like ridge; pa, parapophysis; pas, posterior articular surface; pcdl, posterior centrodiapophyseal lamina; pd, neural arch peduncle; pifo, posterior infradiapophyseal fossa; pit, deep pit lateral to the neural spine; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; st, spine-table.
Figure 11
Posterior trunk vertebrae of Aetosauroides (UFSM 11505). In left lateral (a), posterolateral (b), posterior (c) and ventral (f) views. Interpretative drawings of the lateral (d) and posterolateral view (e). Arrow indicates anterior direction. Abbreviations: acdl, anterior centrodiapophyseal lamina; mifo, middle infradiapophyseal fossa; mlfo, wel-rimmed lateral fossae of the centrum; nc, neural canal; ncs, neurocentral suture; pas, posterior articular surface; pcdl, posterior centrodiapophyseal lamina; pifo, posterior infradiapophyseal fossa; pit, deep pocket pit lateral to the neural spine; psfo, postspinal fossa; podl, posterior zygodiapophyseal lamina; posz, postzygapophyses; st, spine-table; tp, transverse process.
Figure 12
Sacral vertebrae of Aetosauroides (UFSM 11070). a, first sacral vertebra in anterior view. b, both sacrals and first caudals in dorsal view. Interpretative drawings of the anterior (b) and dorsal views (d). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; aesr, anterior expansion of the sacral rib - being confluent with the first sacral rib; Ca, caudal vertebra; d, depression; la, lamina; nc, neural canal; ncs, neurocentral suture; ost, paramedian osteoderm fragment; prez, prezygapophyses; prsfo, prespinal fossa; psfo, postspinal fossa; posz, postzygapophyses; r.I, ridge I; r.II, ridge II; Sa, sacral vertebra; sr, sacral rib; st, spine-table; tp, transverse process; Tv, trunk vertebra.
Figure 13
Sacral and caudal centra of Aetosauroides (UFRGS-PV-1514-T). a, second sacral centrum in anterior (a1) and ventral (a2) views. b, first caudal in anterior (b1), ventral (b2) and lateral (b3) views. c, third caudal in anterior (c1), ventral (c2) and lateral (c3) views. d, preserved articulated centra of the caudal series in dorsal (d1) and ventro-lateral view (d2). Arrow indicates anterior direction. Abbreviations: aas, anterior articular surface; ao, appendicular osteoderm; Ca, caudal vertebra; g, groove; ha, hemal arch; haf, hemal arch facet; ilfo, incipient lateral fossae of the centrum; la, lamina; lfo, lateral fossa; lost, lateral osteoderm; ncs, neurocentral suture; pas, posterior articular surface; sra, articular facet for the sacral rib.
Figure 14
Caudal vertebrae of Aetosauroides (UFSM 11070). a, sequence of available caudal vertebrae in ventral view, with the six first ones found in articulation. Details of the fifth caudal vertebra in posterior (b), dorsal (d) and posterolateral view (f) and interpretative drawings in posterior (c) and dorsal views (e). Arrow indicates anterior direction. Abbreviations: aas.nc, anterior articular surface natural cast; alp, aliform-like process; d, depression; Ca, caudal vertebra; ha, hemal arch; haf, hemal arch facet; izpl, intrapostzygapophyseal lamina; la, lamina; lfo, lateral fossa; nc, neural canal; ncs, neurocentral suture; ns, neural spine; ost, paramedian osteoderm fragment; pas, posterior articular surface; prsfo, prespinal fossa; psfo, postspinal fossa; posz, postzygapophyses; psfo, post-spinal fossa; st, spine-table; tp, transverse process.
Figure 15
Posterior caudals and hemal arches of Aetosauroides (MCP-3450-PV, UFSM 11070 and UFSM 11505). a, two articulated caudals of UFSM 11505 in lateral (a1), dorsal (a2) and ventral (a3) views. b, an isolated caudal of UFSM 11505 in lateral (b1), anterior (b2), posterior (b3) and ventral (b4) views. c1, isolated hemal arch of MCP-3450-PV, in anterior view. c2, articulated caudal vertebrae of MCP-3450-PV. Ten isolated caudal vertebrae of UFSM 11070 and probably some of MCP-3450-PV or UFRGS-1514-T in lateral (d1-l1), anterior (h1-j1), ventral (d3-j3), posterior (d2, g3, i2, j4 and l2) and dorsal views (j2). Abbreviations: aas, anterior articular surface; af, articular facets; alp, aliform-like process; b., broken; cncs, closed neurocentral suture; fsc, fusion scar; g, groove; ha, hemal arch; haf, hemal arch facet; nc, neural canal; ncs, neurocentral suture; ns, neural spine; pas, posterior articular surface; prez, prezygapophyses; posz, postzygapophyses; slfo, slit-like lateral fossae of the centrum; tp, transverse process.
Figure 16
Osteoderm paleohistological thin-section of the holotype of Polesinesuchus aurelioi. a, Composite image of the paramedian dorsal trunk osteoderm (arrows indicate anterior region). b, external and internal cortex details in conventional light (b1) and polarized light (b2), showing the external erosion by the resorption bays and the internal cortex vascularization pattern, with some primary osteons. c, internal cortex and basal layer detail in conventional light (c1) and polarized light (c2) showing the Sharpey fibers orientation and the cyclical growth mark. d, external layer and internal cortex detail the globular osteocyte lacunae, primary osteons and the resorption cavities evidencing the secondary remodeling in conventional light (d1) and polarized light (d2). e, dorsal view of sectioned osteoderm, showing the targeted slice. Abbreviations: bl, basal layer; cgm, cyclical growth mark; el, external layer; gol, globular osteocyte lacunae; il, inner layer; lb, lamellar bone; ool, organized distribution of osteocyte lacunae; ovc, open vascular channels; po, primary osteon; rb, resorbtion bays; rc, resorbtion cavities, rl, resorption line; ShF, Sharpey fibers; sd, secondary deposition; vca, vascular channels anastomoses; wfb, woven fibered bone.
Figure 16
Osteoderm paleohistological thin-section of the holotype of Polesinesuchus aurelioi. a, Composite image of the paramedian dorsal trunk osteoderm (arrows indicate anterior region). b, external and internal cortex details in conventional light (b1) and polarized light (b2), showing the external erosion by the resorption bays and the internal cortex vascularization pattern, with some primary osteons. c, internal cortex and basal layer detail in conventional light (c1) and polarized light (c2) showing the Sharpey fibers orientation and the cyclical growth mark. d, external layer and internal cortex detail the globular osteocyte lacunae, primary osteons and the resorption cavities evidencing the secondary remodeling in conventional light (d1) and polarized light (d2). e, dorsal view of sectioned osteoderm, showing the targeted slice. Abbreviations: bl, basal layer; cgm, cyclical growth mark; el, external layer; gol, globular osteocyte lacunae; il, inner layer; lb, lamellar bone; ool, organized distribution of osteocyte lacunae; ovc, open vascular channels; po, primary osteon; rb, resorbtion bays; rc, resorbtion cavities, rl, resorption line; ShF, Sharpey fibers; sd, secondary deposition; vca, vascular channels anastomoses; wfb, woven fibered bone.
Figure 17
Ontogenetic trajectory of trunk vertebrae of Aetosauroides. Interpretative drawings of the three main ontogenetic changes of Aetosauroides trunk vertebrae: lateral fossae (white line drawing reveal the centrum cross-section); spine table expansion in anterior view; and the pit lateral to the neural spine, in dorsal view. The specimens do not necessarily preserve vertebrae with homologous regions in the trunk series, being the neural arch morphology of MCP-34050 based in an anterior trunk vertebra. The PVL 2052 drawing refers only to the centrum length, as little information is available in the posterior trunk vertebrae of that specimen. Specimens ages based on this study, Cerda & Desojo (2011)CERDA IA & DESOJO JB. 2011. Dermal armour histology of aetosaurs (Archosauria: Pseudosuchia), from the Upper Triassic of Argentina and Brazil. Lethaia 44(4): 417-428. and Cerda et al. (2018)CERDA IA, DESOJO JB & SCHEYER TM. 2018. Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications. Palaeontology 61: 721-745..