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Aetosaur palaeobiology. (a) Life reconstruction of Desmatosuchus spurensis as a herbivore, image # Victor Leshyk. (b) Life reconstruction of Neoaetosauroides engaeus showing the difference in posture between front and back limbs, image # Jorge A. Gonzalez (Palaeontology 50: 269).
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Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species ranging from 1 to 6 m in length, and with a body mass ranging from less than 10 to more than 500 kg, are known. Aetos...
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... body length and mass varied greatly (Fig. 3). The majority of basal aetosaurians were relatively small. Immature specimens of Aetosaurus ferratus are less than 1 m long (Fig. 3a) (Schoch 2007) and had a body mass estimated at less than 4 kg (Taborda 2011). However, some plesiomorphic forms, such as Aetosauroides scagliai and Neoaeto- sauroides engaeus (Fig. 3d), appear to have been nearly the same size as the typothoracisines (Fig. 3j, k) and probably weighed 20-70 kg (Taborda 2011). Calyptosuchus wellesi, elements of which are as large or larger than those of Typothorax coccinarum (Long & Murry 1995), probably weighed at least 100 kg. The wide-bodied typothoracisines appear to have generally been approximately 2-3 m long (nearly half of which is tail) and probably weighed 50-110 kg, and large Typothorax coccinarum specimens have been esti- mated as weighing around 100-110 kg (Heckert et al. 2010). Desmatosuchines include some of the smallest and largest aetosaurs known: Acaenosu- chus geoffreyi may been of comparable size to smaller specimens of Aetosaurus ferratus (assum- ing that it is not a juvenile), and Longosuchus (¼Typothorax) meadei has been estimated as weighing 68 kg (Kubo & Benton 2007). Desmatosu- chus spurensis may have reached a body mass of at least 280 kg (Kubo & Benton 2007) and a length of 6 m or more (Parker 2008), making it the largest aetosaur known. Most of the above mass esti- mates were based on the Anderson et al. (1985) method, utilizing the mid-shaft circumference of the humerus and femur. Sawin (1947) proposed that Longosuchus meadei was a scavenger (¼'necrophile': Sawin 1947, p. 238), 'not adapted to predaceous habits and the heavy and complete armour predicate a passive mode of life'. However, Walker (1961) and most recent workers have considered aetosaurs to be more herbivorous, omnivorous or, possibly, even insectivorous (Small 2002;Desojo 2003, Desojo & Vizcaíno 2009). Many authors have considered modern armadillos (Dasypodidae), which have broadly omnivorous diets that include arthropods (Smith & Redford 1990), as an analogue for aeto- saurs (e.g. Bonaparte 1978;Small 2002;Sulej 2010). Parrish (1994) addressed the possibility of her- bivory in aetosaurs generally (Fig. 9a), noting the depression of the jaw joint below the level of the tooth row in most aetosaurs where the skull and jaw are known (Fig. 4: also the condition of most herbivorous dinosaurs), and the simple, conical dentition typical of most aetosaurian taxa. Parrish (1994) also proposed a keratinous beak over the edentulous portion of the snout and mandible (Parrish 1994, p. 204) (2009) disputed the likelihood of such a beak in Neoaetosauroides engaeus and other aetosaurs, noting the scarcity in the anterior snout of thick- ened bone margins, vascularization and ...
Context 2
... Walker (1961) and Desojo & Vizcaíno (2009) suggested that the shovel-shaped expansion on the snout in most aetosaurs (Fig. 4e) (except Aetosaurus ferratus: see Schoch 2007) may have been used for digging or grubbing. Walker (1961) speculated briefly that Stagonolepis robertsoni may have used its forelimbs for digging, and Heckert et al. (2010) provided more extensive evi- dence that Typothorax coccinarum was reasonably adapted to dig with its limbs as well. Specifically, Heckert et al. (2010, pp. 637 -638) noted that T. coccinarum has a low brachial index (radius shorter than humerus), short, wide metacarpals and phalanges, a prominent deltopectoral crest that extends distally on the humerus, and a wide entepi- condyle, all characteristics that Hildebrand (1974,1983) used to identify digging behaviour in extant vertebrates. Furthermore, the possession of large, curved, laterally compressed unguals and a com- pact, strongly articulated pes may indicate scratch- digging behaviour (Heckert et al. 2010), as Benton (1983) had posited for the rhynchosaur Hyperoda- pedon. Such digging adaptations might have been used to unearth roots (Fig. 9a) or burrowing ...
Citations
... Neosuchians also returned to a land-living lifestyle on two occasions, within Planocraniidae and Mekosuchinae [5]. These terrestrial forms show considerable disparity in diet (figure 1) with Triassic aetosaurs and poposauroids showing adaptations for herbivory and omnivory [7,8], traits which also evolved independently in numerous notosuchians [9]. Other terrestrial crurotarsans occupied top predatory niches, from Triassic 'rauisuchians' [10] to huge sebecid notosuchians in the Cenozoic [11,12]. ...
Extant crocodilian jaws are subject to functional demands induced by feeding and hydrodynamics. However, the morphological and ecological diversity of extinct crocodile-line archosaurs is far greater than that of living crocodilians, featuring repeated convergence towards disparate ecologies including armoured herbivores, terrestrial macropredators and fully marine forms. Crocodile-line archosaurs, therefore, present a fascinating case study for morphological and functional divergence and convergence within a clade across a wide range of ecological scenarios. Here, we build performance landscapes of two-dimensional theoretical jaw shapes to investigate the influence of strength, speed and hydrodynamics in the morphological evolution of crocodile-line archosaur jaws, and test whether ecologically convergent lineages evolved similarly optimal jaw function. Most of the 243 sampled jaw morphologies occupy optimized regions of theoretical morphospace for either rotational efficiency, resistance to Von Mises stress, hydrodynamic efficiency or a trade-off between multiple functions, though some seemingly viable shapes remain unrealized. Jaw speed is optimized only in a narrow region of morphospace whereas many shapes possess optimal jaw strength, which may act as a minimum boundary rather than a strong driver for most taxa. This study highlights the usefulness of theoretical morphology in assessing functional optimality, and for investigating form–function relationships in diverse clades.
... The Aetosauria is an extinct clade of extensively armored pseudosuchian archosaurs that reached a high species diversity during the Late Triassic (Heckert & Lucas, 2000Parker, 2016a, b). The aetosaurs are characterized by a small skull with strongly tapering laterally expanded snout (e.g., Stagonolepis robertsoni), upturned, and predominantly edentulous premaxilla, long tail, comparatively small forelimbs and an ornamented dermal armor or carapace covering the postcranial region (Antczak, 2016;Desojo et al., 2013). The discovery of an array of dentigerous material suggests that aetosaurs were large omnivorous to insectivorous quadrupeds (Desojo & Ezcurra, 2011;Desojo et al., 2013;Paes-Neto et al., 2021a;Parker, 2016a;Reyes et al., 2021;von Baczko et al., 2018). ...
... The aetosaurs are characterized by a small skull with strongly tapering laterally expanded snout (e.g., Stagonolepis robertsoni), upturned, and predominantly edentulous premaxilla, long tail, comparatively small forelimbs and an ornamented dermal armor or carapace covering the postcranial region (Antczak, 2016;Desojo et al., 2013). The discovery of an array of dentigerous material suggests that aetosaurs were large omnivorous to insectivorous quadrupeds (Desojo & Ezcurra, 2011;Desojo et al., 2013;Paes-Neto et al., 2021a;Parker, 2016a;Reyes et al., 2021;von Baczko et al., 2018). Aetosaurs are documented within the Upper Triassic strata of Texas, Arizona, New Jersey, Colorado, New Mexico (Case, 1932;Cope, 1875;Gregory, 1953;Heckert & Lucas, 1999;Hunt & Lucas, 1991;Long & Murry, 1995;Lucas et al., 2007;Marsh et al., 2020;Sawin, 1947;Small, 1998Small, , 2002, Greenland (Jenkins et al., 1994), Brazil, Argentina (Bonaparte, 1969;Casamiquela, 1960Casamiquela, , 1980Desojo et al., 2012), U.K., Germany, Italy, Poland, Scotland (Agassiz, 1844;Czepinśki et al., 2021;Drózḋz, 2018;Dzik et al., 2000;Fraas, 1877;Hunt & Lucas, 1992;Long & Ballew, 1985;Parker, 2018a;Sulej et al., 2012;Teschner et al., 2022;von Huene, 1920;Walker, 1961), Morocco (Jalil et al., 1995), and India (Bandyopadhyay & Ray, 2020;Kutty & Sengupta, 1989). ...
... Aetosaurs are documented within the Upper Triassic strata of Texas, Arizona, New Jersey, Colorado, New Mexico (Case, 1932;Cope, 1875;Gregory, 1953;Heckert & Lucas, 1999;Hunt & Lucas, 1991;Long & Murry, 1995;Lucas et al., 2007;Marsh et al., 2020;Sawin, 1947;Small, 1998Small, , 2002, Greenland (Jenkins et al., 1994), Brazil, Argentina (Bonaparte, 1969;Casamiquela, 1960Casamiquela, , 1980Desojo et al., 2012), U.K., Germany, Italy, Poland, Scotland (Agassiz, 1844;Czepinśki et al., 2021;Drózḋz, 2018;Dzik et al., 2000;Fraas, 1877;Hunt & Lucas, 1992;Long & Ballew, 1985;Parker, 2018a;Sulej et al., 2012;Teschner et al., 2022;von Huene, 1920;Walker, 1961), Morocco (Jalil et al., 1995), and India (Bandyopadhyay & Ray, 2020;Kutty & Sengupta, 1989). Because of their wide global distribution and restricted occurrences, aetosaurs are considered biostratigraphically important (Desojo & Ezcurra 2011;Desojo et al. 2013;Heckert & Lucas, 1999Lucas, 2018;Parker, 2016a, b;Parker et al., 2008). ...
A new typothoracine aetosaur is described based on multiple isolated and articulated left paramedian and lateral osteoderms recovered from the Upper Triassic lower Dharmaram Formation of India. The partial carapace of the new taxon is reconstructed as strongly discoidal based on the curvature of the paramedian osteoderms with the widest one positioned dorsal to the mid-dorsal trunk vertebra. Asymmetric lateral osteoderms with acute flexion are considered as precaudals with the angle of flexion decreasing posteriorly. Phylogenetic analysis recovered the new taxon as deeply nested within the clades Typothoracinae and Paratypothoracini, and a sister taxon to Kocurypelta silvestris. The autapomorphic characters involving paramedian osteoderms dorsal to the trunk vertebrae include dorsal surface ornamented by large, irregular pits surrounding the dorsal eminence and radiating ridges in other areas, straight anterior margin of the anteromedial corner of the anterior bar in dorsal view, and raised or ridged and ornamented posteromedial corner. The current study highlights the significance of the new aetosaur, and the age of the lower Dharamaram Formation is modified here as mid-Norian to Rhaetian based on global correlation with other coeval horizons. The recovery of this taxon marks the first record of Paratypothoracini from high paleolatitudes of the Gondwanan region. The study corroborates the earlier findings of a strong Laurasian faunal influx in India during the Late Triassic suggesting possible land bridges and/or conducive environmental conditions for faunal dispersal. http://zoobank.org/urn:lsid:zoobank.org:pub:FCC37C0E-107F-4B15-9460-4E802B465865
... As such, the incorporation of vertebrate biostratigraphy has long been used to bolster and refine regional and global chronostratigraphic correlations (Ochev and Shishkin, 1989;Lucas, 1998Lucas, , 2010Langer, 2005;Klein and Lucas, 2010;Loughney et al., 2011). However, the integration of vertebrate biostratigraphy into chronostratigraphic frameworks has been criticized for poor taxonomic resolution among some index taxa and poor definitions of biostratigraphic boundaries (e.g., Rayfield et al., 2005Rayfield et al., , 2009Irmis et al., 2010Irmis et al., , 2011Desojo and Ezcurra, 2011;Desojo et al., 2013;Butler, 2013;Kam-merer et al., 2016). directly addressed these concerns in a review of biostratigraphic concepts and nomenclature in which they leveraged the fossil assemblages of the Chinle Formation and Dockum Group as an exemplar. ...
The Upper Triassic Popo Agie Formation of the Chugwater Group of Wyoming, northeastern Utah, and northwestern Colorado has been an enigmatic unit since its definition and is commonly excluded from large-scale studies of continental Upper Triassic strata in the western USA. Lithostratigraphic correlations of Popo Agie Formation outcrops are documented from west-central Wyoming through northeastern Utah and northwestern Colorado, which demonstrates the presence of the Popo Agie Formation throughout this region. Unique detrital zircon age distributions have led previous workers to hypothesize a paleodrainage connecting basal units of the Dockum in west Texas and eastern New Mexico, USA, with the Gartra Grit, a basal unit of the Popo Agie in northeastern Utah. Biostratigraphically informative taxa such as parasuchid phytosaurs in the absence of leptosuchmorph phytosaurs support an assignment of the Gartra Grit and Popo Agie Formation to the Otischalkian estimated holochronozone. We present the first detrital zircon age distributions for the Popo Agie Formation. Multidimensional scaling analysis of zircon populations shows that the Popo Agie samples are similar to other Upper Triassic units surrounding the Ancestral Uncompahgre Highlands, Central Colorado Trough, and the Ancestral Front Range. Additionally, we present the first maximum depositional ages (youngest population) for the Popo Agie Formation at a location where the top of the ochre unit is no older than 225 ± 4 Ma, and the upper purple to ochre transition is no older than 230 ± 5 Ma. By leveraging existing biostratigraphy, regional lithostratigraphy, and new radioisotopic ages we temporally constrain the Popo Agie Formation, enabling us to integrate the upper Chugwater Group, Chinle Formation, and Dockum Group strata into a testable Late Triassic chronostratigraphic framework for the western USA. The consilience of data support a Carnian age for the majority (if not entirety) of the Popo Agie Formation, making this—and equivalent strata in the Dockum Group (i.e., Camp Springs Conglomerate, and strata of the Tecolotito and Los Esteros members of the Santa Rosa Formation)—among the oldest continental Late Triassic stratigraphic units in the western USA.
... Given the highly divergent shape of this osteoderm relative to of all others known from this locality, its position and anatomical directions are unknown. Accordingly, we employ the anatomical orientation of a The earliest-diverging avemetatarsalian • 337 (Parker 2007, 2008, Desojo et al. 2013. This rectangular osteoderm is about twice as wide as long, with a distinct bend just off the mediolateral centre. ...
Understanding the evolution of the earliest avemetatarsalian (bird-line) archosaurs and inferring the morphology of the last common ancestor of Archosauria are hampered by a poor fossil record in critical temporal intervals. Here we describe an early-diverging avemetatarsalian from the ?Earliest Late Triassic (~235 Ma) ‘basal Isalo II’/Makay Formation of Madagascar, which helps bridge these gaps. This taxon, Mambachiton fiandohana gen. et sp. nov., is represented by well-preserved postcranial material and possibly a postfrontal bone. Features of the neck region include anteroposteriorly elongated vertebrae with laterally expanded dorsal ends of the neural spines with three pairs of osteoderms per cervical vertebra, lying dorsal to those vertebrae. Inclusion of Mambachiton in a phylogenetic analysis of archosauromorphs recovers it at the base of Avemetatarsalia, outside of the aphanosaur + ornithodiran clade. This new specimen indicates that osteoderms were present in the earliest avemetatarsalians, but were lost in more crownward lineages. The plesiomorphic morphology of the taxon also underscores the difficulty of identifying early avemetatarsalians from incomplete skeletons. This early-diverging avemetatarsalian occurring together with a lagerpetid and silesaurid in the ‘basal Isalo II’/Makay Formation of Madagascar documents the co-occurrence of multiple non-dinosaurian avemetatarsalian clades in Gondwana near the Middle–Late Triassic transition. Translated abstract ( Malagasy and French) is provided in the Supplementary information.
... The Aetosauria Marsh (1884) is a clade of heavily armored pseudosuchian tetrapods that is currently constrained to strata of Late Triassic age (Carnian-Rheatian, ~237-201 Ma; Heckert and Lucas 2000, Desojo et al. 2013, Parker 2016a. Aetosaurs have been reported from continental strata across the globe including Europe, India, Africa, and North and South America (Desojo et al. 2013). ...
... The Aetosauria Marsh (1884) is a clade of heavily armored pseudosuchian tetrapods that is currently constrained to strata of Late Triassic age (Carnian-Rheatian, ~237-201 Ma; Heckert and Lucas 2000, Desojo et al. 2013, Parker 2016a. Aetosaurs have been reported from continental strata across the globe including Europe, India, Africa, and North and South America (Desojo et al. 2013). Historically, our evolutionary understanding of the Aetosauria was predominantly based on their osteoderms (e.g., Long and Ballew 1985, Long and Murry 1995, Heckert and Lucas 1999, Parker 2007. ...
... This is partially a result of their osteoderms being some of the most commonly collected fossilized elements recovered from Late Triassic strata. Osteoderms are integumental ossifications that are independent of the main skeletal system, allowing them to become easily dispersed during the taphonomic process, particularly in fluvial systems *Author for correspondence (Desojo et al. 2013, Scheyer et al. 2014. However, in the last two decades, the discovery of relatively complete skeletons and skulls for a variety of aetosaurian taxa provided a means of more holistically assessing interspecific variation within the clade (e.g., Heckert and Lucas 1999, Heckert et al. 2010, Taborda et al. 2015, Parker 2016a, Schoch and Desojo 2016, Reyes et al. 2020, Paes-Neto et al. 2021a. ...
he Late Triassic Chinle Formation in northern Arizona and Dockum Group in northwestern Texas preserve a high aetosaur biodiversity within the Adamanian teilzone, including Desmatosuchus spurensis, Desmatosu- chus smalli, Calyptosuchus wellesi, Adamanasuchus eisenhardtae, Typothorax coccinarum, Paratypothorax sp., Tecovasuchus chatterjeei, and Sierritasuchus macalpini. Here, we present a new aetosaur Kryphioparma caerula gen. et sp. nov. from the upper Blue Mesa Member of the Chinle Formation, Adamanian teilzone, in northern Arizona. Kryphioparma caerula sp. nov. is documented based on several isolated osteoderms collected from the Placerias Quarry and Petrified Forest National Park. Although fragmentary, it is evident that the paramedian osteoderms of Kr. caerula exhibit a dorsal ornamentation composed of large, randomly oriented oblong pits; a low concentration of pits relative to available surface area; well-developed anterior bar; a probable high width-to-length ratio; dorsoventrally thickened; well-developed ventral strut; and grooves along the posterior margin. This suite of morphological characters indicates that Kr. caerula is a typothoracine similar to Ty. coc- cinarum, Te. chatterjeei, and P. andressorum; its stratigraphic occurrence within the upper Blue Mesa Member makes it the oldest documented typothoracine to date. The documentation of Kr. caerula within the Placerias Quarry brings to question the taxonomic affinities of paratypothoracin material identified as “Tecovasuchus” by previous authors, as well as the biostratigraphic utility of Te. chatterjeei across the southwestern United States. We present the first unambiguous material referable to Te. chatterjeei from the Downs Quarry and Petrified Forest National Park. The documentation of Te. chatterjeei in the Chinle Formation of northern Arizona and Tecovas Formation of northwestern Texas suggests that this taxon may be biostratigraphically informative as
... There were a number of tetrapod clades that radiated and became more geographically widespread in the late Carnian and continuing through the Norian, but had known or inferred origins earlier in the Triassic. These include crocodile-like phytosaurs, armoured, primarily herbivorous aetosaurs, and rhynchocephalians, a sister group to lizards and snakes with a single extant species (Stocker et al., 2017;Desojo et al., 2013;Hsiou et al., 2019). Most important in terms of subsequent ecological and evolutionary success were the dinosaurs. ...
... Aetosaurs were quadrupedal, fully terrestrial, heavily armoured pseudosuchians that experienced a radiation during the Late Triassic. Their length varied between 1 and 6 m; their limbs were well-developed and the small skull had a shovel-shaped snout (Walker, 1961;Heckert and Lucas, 2000;Desojo et al., 2013). Surface ornament, width/length ratios and lateral osteoderm morphology are diagnostic for aetosaurian clades and in some cases, for species (Parker, 2018b). ...
... There are different versions of the phylogenetic trees of aetosaurians, but additional work aimed at clarifying various issues is ongoing. It has been suggested that Aetosauroides scagliai is the most basal aetosaur and sister-taxon to all other members of the Aetosauria (Desojo et al., 2013;Parker, 2016a;Brust et al., 2018). ...
... Aetosaur material has been recorded from Europe, North and South America, Greenland, Morocco and India (Desojo et al., 2013;Roberto-da-Silva et al., 2014;Parker, 2016a). The presence of these reptiles in South Africa has not yet been confirmed; to date, only footprints (ichnogenus Brachychirotherium) have been documented. ...
In recent years, the Upper Triassic deposits at Krasiejów (south-west Poland) have yielded several tetrapod taxa, both aquatic and terrestrial. Stagonolepis olenkae is one of the terrestrial vertebrates recovered there; a quadrupedal, armoured aetosaur, which belonged to the crocodile-line archosaurs with a characteristic shovel-shaped snout. Several previous studies (osteological, histological and taphonomic) have attempted to understand the mode of life, growth pattern and possible dimorphism of this species and on this basis, to interpret palaeoecological, palaeoclimatic and stratigraphical implications. So far, the pelvic girdle of S. olenkae from Krasiejów remained undescribed. Here, the authors record stagonolepid ilia and pubes and a single ischium from collections housed at the University of Opole, and compare these with the pelvic girdles of other aetosaurian taxa. These well-preserved bones have a typical aetosaurian general outline, but also show some peculiar features.
For instance, the preacetabular blade of the ilium is short and flattened and does not exceed the pubic peduncle; several small foramina occur dorsally of the supracetabular crest; the number of pubic foramina is two and the pubic symphysis is less than half the length of the pubis. The material is similar to previously known
Stagonolepis robertsoni from the Elgin area, except for the length of the symphysis. The bones presented here differ between each other in thickness, morphology of the preacetabular blade or attachment of sacral ribs, which may be connected with sexual dimorphism. The pelvic girdle of most aetosaurs is not well known. This is unfortunate,
because it is an important element in the study of the evolution of the pelvic girdle and in phylogenetic analyses. Thus, the ilia, pubes and ischium of the present study are valuable examples that may contribute to the discussion of the ontogeny and sexual dimorphism in Stagonolepis, as well as to our general knowledge of the Aetosauria.
... Two major archosaur groups, Aetosauria (Marsh, 1884) and Phytosauria (Jäger, 1828), are a constant component of Late Triassic (Carnian to Rhaetian) faunal assemblage found on almost all continents (Buffetaut, 1993;Lucas, 1998;Desojo et al., 2013;Stocker & Butler, 2013;Barrett et al., 2020). The only exception is Diandogosuchus from the Middle Triassic of China (Li et al., 2012;Stocker et al., 2017), representing so far, the oldest and phylogenetically most basal phytosaur (Butler et al., 2019). ...
... The only exception is Diandogosuchus from the Middle Triassic of China (Li et al., 2012;Stocker et al., 2017), representing so far, the oldest and phylogenetically most basal phytosaur (Butler et al., 2019). Aetosauria are interpreted as being herbivorous to omnivorous in diet and occupying terrestrial habitats (Carroll, 1988;Small, 2002;Desojo & Vizcaino, 2009;Desojo et al., 2013). Phytosaurs are mostly found in lacustrine and fluviatile environments worldwide (Hungerbühler, 2000;Stocker & Butler, 2013) and their mode of life was reconstructed as semi-aquatic to aquatic (Hunt, 1989). ...
The growth pattern of the Polish phytosaur Parasuchus cf. arenaceus and the aetosaur Stagonolepis olenkae (both Krasiejów; Norian) was studied. Results were compared to published data of other members of these two groups and to a new sample of the German (Heslach; Norian) phytosaur Nicrosaurus sp. All three herein studied taxa display lamellar-zonal bone consisting predominately of parallel-fibred tissue and on average a low to moderate vascular density. Towards the outer cortex the thickness of annuli increases in most samples and becomes distinctly wider than the zones. Therefore, most of the appositional growth in adults was achieved during phases of prolonged slow growth. All bones show a diffuse growth pattern, without well demarcated zones and annuli. Distinct lines of arrested growth (lag) are not identified in the Krasiejów sample, only the Nicrosaurus femur shows one distinct lag as do other taxa outside Krasiejów. Instead, the Krasiejów taxa display multiple rest lines and sub-cycles. Thus, identification and count of annual growth cycles remains difficult, the finally counted annual growth cycles range (two to six) is quite large despite the low size range of the samples. A correlation between age and bone length is not identified, indicating developmental plasticity. Although both are archosaurs, Stagonolepis and Parasuchus are hylogenetically not closely related, however, they show a very similar growth pattern, despite different life styles (terrestrial vs. semi-aquatic). Based on the new data, and previously histological studies from Krasiejów, the local environmental conditions were special and had a strong influence on the growth pattern.
... Aetosauria is a clade of quadrupedal, armored archosaurs whose terrestrial ecology is inferred as including both herbivory and omnivory (Desojo et al., 2013). Aetosaurs achieved a nearly global geographic distribution, whereas they are stratigraphically restricted to the Upper Triassic (Carnian-Rhaetian) (Desojo et al., 2013;Biacchi Brust et al., 2018). ...
... Aetosauria is a clade of quadrupedal, armored archosaurs whose terrestrial ecology is inferred as including both herbivory and omnivory (Desojo et al., 2013). Aetosaurs achieved a nearly global geographic distribution, whereas they are stratigraphically restricted to the Upper Triassic (Carnian-Rhaetian) (Desojo et al., 2013;Biacchi Brust et al., 2018). Most aetosaur taxa reach a total body length between 2 and 6 meters (Desojo et al., 2013). ...
... Aetosaurs achieved a nearly global geographic distribution, whereas they are stratigraphically restricted to the Upper Triassic (Carnian-Rhaetian) (Desojo et al., 2013;Biacchi Brust et al., 2018). Most aetosaur taxa reach a total body length between 2 and 6 meters (Desojo et al., 2013). The only exceptions are the relatively small Coahomasuchus spp. ...
... This group was a common element of the Upper Triassic continental ecosystems of Europe, North Africa, India, North and South America. In the last continent, aetosaurs are represented by four species: Aetobarbakinoides brasiliensis (Desojo et al. 2012) from Brazil; Aetosauroides scagliai (Casamiquela 1960) from Argentina and Brazil; Neoaetosauroides engaeus (Bonaparte 1969) from Argentina and the putative assigned Chilenosuchus forttae (Casamiquela 1980) from Chile (Desojo 2003;Desojo andBáez 2005, 2007;Parker 2007;Desojo et al. 2013). Additionally, other individuals are tentatively assigned to Aetosauria in South America, like PVSJ 691 specimen (Heckert et al. 2021). ...
Aetosaurs were a group of armoured pseudosuchians, recorded in most of the Upper Triassic continental deposits worldwide. Several osteohistological contributions of aetosaurs focused on their osteoderms, but rarely on appendicular bones. Here, we analyse the microstructure of the humerus, femur and tibia of Aetosauroides scagliai (specimens PVL 2073 [holotype] and PVL 2052). These exhibit cortical bone formed by highly vascularised fibrolamellar bone present in the inner portion of the cortex, mixed with scarce parallel-fibred bone. Also, they show parallel-fibred bone in the outermost portion of the cortex. A general growth pattern that includes a first rapid stage followed by a slow stage is reported. Nevertheless, the growth rate and the presence of parallel-fibred bone embedded in fibrolamellar bone layers recognise more variation within Aetosauria. The value of appendicular bones and osteoderms as age estimators is variable, the first being useful in early stages, and in late stages the osteoderms are better (based on the particular growth of osteoderms). Through morphological (neurocentral sutures) and histological (EFS absent) information, the holotype (PVL 2073) was recovered between juvenile and subadult stages. Using a statistical model that combines microanatomical and morphological data, a terrestrial lifestyle is inferred for Aetosauroides, which concur with previous analyses.
