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59-620: Acaenasuchus (from the Greek akaina, meaning "thorn" and suchus , meaning "crocodile") is an extinct genus of pseudosuchian , endemic to what would be presently be known as Arizona during the Late Triassic , specifically during the Carnian and Norian stages of the Triassic. Acaenasuchus had a stratigraphic range of approximately 11.5 million years . Acaenasuchus is further categorized as one of

118-494: A branch-based clade, Pseudosuchia is the sister taxon of another branch-based clade, the Avemetatarsalia . Avemetatarsalians are bird-line archosaurs, including pterosaurs and dinosaurs (the latter including birds). A different definition was suggested by Benton and Clark, 1988: the node-based taxon including the last common ancestor of Rauisuchidae and aetosaurs and all of its descendants. Benton and Clark also named

177-570: A diverse array of lifestyles during the Jurassic and Cretaceous periods, although only a single subset of crocodylomorphs, the Crocodilia, survive to the present day. Living crocodilians include crocodiles , alligators , caimans , and gavialids . The name Pseudosuchia was originally given to a group of superficially crocodile-like prehistoric reptiles from the Triassic period, but fell out of use in

236-461: A dry and wet season. The Chinle Formation during the Late Triassic was a time and place of great faunal diversity. Archosaurs were evolving and diversifying rapidly, Acaenasuchus is hypothesized to occupy a similar niche to smaller archosaurs of the time. Acaenasuchus has been organized under the clade Pseudosuchia , the crocodilian line archosaurs . Acaenasuchus is further organized within

295-513: A group called Crocodylotarsi, which includes most taxa now considered pseudosuchians. In 1990, Paul Sereno erected the clade Crurotarsi to supplant Pseudosuchia. However, Sereno defined Crurotarsi as a node-based clade, relying on the inclusion of groups such as Phytosauria , Aetosauria, and Crocodylomorpha . It is not equivalent to Pseudosuchia, which by definition must include all crocodilian-line archosaurs. For many years, Pseudosuchia and Crurotarsi have been considered partial synonyms because

354-477: A little less than the depth of the groove. Two or more pieces thus fit together closely. The joint is not normally glued , as shrinkage would then pull the tongue off. In another assembly method, the pieces are end-matched. This method eliminates the need for mitre joints , face nailing , and the use of joints on 16-inch (410 mm) or 24-inch (610 mm) centres of conventional framing . For many uses, tongue and groove boards have been rendered obsolete by

413-407: A similar definition, Crocodylotarsi, was named in 1988, possibly as a replacement for Pseudosuchia. The name Pseudosuchia, meaning "false crocodiles", has been used for over a century, and traditionally included only non-crocodilians, but when defined as a clade, Pseudosuchia came to include the group Eusuchia ("true crocodiles") as well. Crocodylotarsi may have been named to remove confusion, but as

472-410: A staggering diversity of reptiles with many different lifestyles. Early pseudosuchians were successful in the Triassic period. They included giant, quadrupedal apex predators such as Saurosuchus , Prestosuchus , and Fasolasuchus . Ornithosuchids were large scavengers, while erpetosuchids and gracilisuchids were small, light-footed predators. A few groups acquired herbivorous diets, such as

531-399: A stem-based clade, it is synonymous with Pseudosuchia. Because Pseudosuchia was named first, it has precedence. A third group, Crurotarsi , traditionally included the same archosaurs as Pseudosuchia, but as a node-based clade it is not synonymous. The scope of Crurotarsi has recently been changed by the phylogenetic placement of phytosaurs. In 2011, Sterling J. Nesbitt found phytosaurs to be

590-405: A subset of the group. The clade Pseudosuchia is potentially equivalent to Crurotarsi even though the latter has a different, node-based definition: "all taxa the least inclusive clade containing Rutiodon carolinensis (Emmons, 1856), and Crocodylus niloticus (Laurenti, 1768)." However, a major 2011 study of Triassic archosaur relations proposed that Rutiodon 's group, Phytosauria ,

649-966: Is a cladogram modified from Nesbitt (2011) showing the new changes (bold terminal taxa are collapsed). † Proterosuchidae [REDACTED] † Erythrosuchus [REDACTED] † Vancleavea [REDACTED] † Proterochampsia [REDACTED] † Euparkeria [REDACTED] † Phytosauria [REDACTED] Avemetatarsalia (bird-lineage of archosaurs) [REDACTED] † Ornithosuchidae [REDACTED] † Gracilisuchus [REDACTED] † Turfanosuchus [REDACTED] † Revueltosaurus [REDACTED] † Aetosauria [REDACTED] † Ticinosuchus [REDACTED] † Poposauroidea [REDACTED] † Prestosuchus [REDACTED] † Saurosuchus [REDACTED] † Batrachotomus [REDACTED] † Fasolasuchus † Rauisuchidae [REDACTED] Crocodylomorpha [REDACTED] The following cladogram

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708-408: Is a large boss that forms the dorsal surface of the orbit, perhaps representing a palpebral co-ossification to the frontal. There are two foramina present on the ventral surface of the bone beneath the large boss. The parietal bone is ornamented with sharp ridges and deep pits on the dorsal surface. The dorsal surface of the parietal bone lacks a midline crest. The squamosal bone of Acaenasuchus

767-607: Is characterized specifically by scutes highly developed through the pre-sacral series. These scutes further include the presence of thorn-like processes parallel along the side of the posterior region of the paramedian scutes. Additionally the scutes are described as highly ornamented with ridges and hollows not present in Desmatosuchus . It was known only by its dermal armor until 2016. The 2016 excavations revealed cranial, mandibular, vertebral, pelvic, etc... bones. Acaenasuchus paramedian scutes are relatively small in size, similar to

826-1026: Is from a slightly older study, Brusatte, Benton, Desojo and Langer (2010). Bold terminal taxa are collapsed. Several results of the study, such as the retention of a monophyletic Rauisuchia , the retention of phytosaurs within Pseudosuchia, and a close relation between aetosaurs and crocodylomorphs, replicate the results of older studies. However, the findings of Nesbitt (2011) have been more widely supported by pseudosuchian-focused analyses published since 2011. † Erythrosuchus [REDACTED] † Euparkeria [REDACTED] † Proterochampsidae [REDACTED] Avemetatarsalia [REDACTED] † Phytosauria [REDACTED] † Aetosauria [REDACTED] † Gracilisuchus [REDACTED] † Erpetosuchus [REDACTED] Crocodylomorpha [REDACTED] † Revueltosaurus [REDACTED] † Ornithosuchidae [REDACTED] Tongue and groove A strong joint,

885-442: Is longer anteriorly than it is wide posteriorly. The dorsal surface of the squamosal is ornamented in the form of small ridges and pits. The articular facet is broad. The surangular articulates the articular . The lateral side of the surangular is ornamented in the form of long ridges and oblong pits. The medial articular foramen is present. The retro-articular process of Acaenasuchus is short and curved. Trunk vertebrae are

944-507: Is not supported strongly... due to the fact that the concept of ontogenetic maturation is a poorly understood phenomena within Aetosauria. To address the geographical proximity of Acaenasuchus fossils to those of adult Desmatosuchus, evidence has not been studied to an extent sufficient to claim synonymy at this time. There are too many variables to consider, such as the possibility that both species lived in close proximity to each other during

1003-583: Is one of the two primary "daughter" clades of the Archosauria . The skull is often massively built, especially in contrast to ornithodires ; the snout is narrow and tends to be elongated, the neck is short and strong, and the limb posture ranges from a typical reptilian sprawl to an erect stance like dinosaurs ' or mammals ', although achieving it a different way. The body is often protected by two or more rows of armored plates. Many crurotarsans reached lengths of three meters or more. Pseudosuchians appeared during

1062-404: Is one of two major divisions of Archosauria , including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs", in contrast to the "bird-line archosaurs" or Avemetatarsalia . Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as

1121-425: Is ornamentation on the lateral side of the maxilla in the form of grooves below the ant-orbital foramen, and ridges and pits above. There is a short anterior process of the maxilla which projects ventrally. The teeth are described as having a rounded tip similar to R. callenderi , and contain broad denticles . There is ornamentation on the lateral surface of the jugal bone in the form of ridges and pits. The bone

1180-412: Is short. The zygapophyses are separated by a thin slot. The scapula of Acaenasuchus has not been fully excavated, only the proximal portion of the scapula has been recovered. The articulation with the coracoid has been observed. There is a small tubercle present above the glenoid towards the posterior end of the scapula. The coracoid has only been partially excavated as well. The proximal end of

1239-415: Is sometimes abbreviated as T&G (for example, on price tags and shelf tags). One of the following woodworking tools may be used to produce the tongue and groove: Tongue-in-groove is similar to tongue and groove, but instead of the tongue forming part of one of the edges, it is a separate, loose piece that fits between two identically grooved edges. The tongue may or may not be of the same material as

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1298-437: Is thin and tapers in the posterior direction. An early suchian feature, there is a sharp longitudinal ridge present on the lateral side of the jugal. In Acaenasuchus , the longitudinal ridge lies above a shallow groove. The frontal bone of Acaenasuchus is relatively narrower in the anterior direction. There is ornamentation on the dorsal surface of the frontal bone in the form of sharp circular ridges and oblong pits. There

1357-404: The pubis . The femur is relatively short and solid. The femoral head is "blocky" and includes a short groove on the proximal surface. On the anterior surface, the distal region of the femur is smooth. The carapace of Acaenasuchus is of normal proportions, with most armor including thin anterior laminae . Multiple plates of the carapace include extensive laminae suggesting that the carapace

1416-399: The tongue and groove joint is widely used for re-entrant angles. The effect of wood shrinkage is concealed when the joint is beaded or otherwise moulded. In expensive cabinet work, glued dovetail and multiple tongue and groove are used. Each piece has a slot (the groove or dado ) cut all along one edge, and a thin, deep ridge (the tongue ) on the opposite edge. The tongue projects

1475-574: The Late Triassic period. It is also notable that the Chinle Formation is a region rich in Aetosaur specimens, not solely Desmatosuchus. Acaenasuchus was very small and narrow-bodied. It is hypothesized to be less than 0.6m in length. Long and Murry provided the characterization of multiple Acaenasuchus features upon its discovery in 1995. Acaenasuchus possess paramedian scutes with anterior laminae, similar to Desmatosuchus . However, Acaenasuchus

1534-499: The area, gleyed mudstones represent floodplain paleosols , and organic mudstones represent bogs. Acaenasuchus was known to be a terrestrial organism, there is little information available that would suggest the Acaenasuchus had semiaquatic potential. Chinle climates in the Late Triassic, when Acaenasuchus lived, is hypothesized to have had significant precipitation seasonally. There may have been what we would categorize today as

1593-521: The birds, while the crocodilians continued with little change. Today, the crocodiles , alligators , and gharials are the surviving representatives of this lineage. The Mesozoic range of cranial disparity is higher than the Triassic one, suggesting crocodylomorphs attained a high degree of diversification compared to Triassic pseudosuchians. Pseudosuchia was defined as a stem-based clade in 1985. It includes crocodiles and all archosaurs more closely related to crocodiles than to birds. A second clade with

1652-402: The coracoid including articulation with the scapula has been described. The humerus has been recovered including all regions but the mid-diaphysis. Three bulb like structures can be observed on the humeral head. The median humeral head is the largest of the three. A semicircular foramen is observed underneath the humeral head. A sub-circular "cuboid fossa" is described on the distal portion of

1711-504: The dominant terrestrial carnivores and herbivores. As the Mesozoic progressed, the Protosuchia gave rise to more typically crocodile-like forms. While dinosaurs were the dominant animals on land, the crocodiles flourished in rivers, swamps, and the oceans, with far greater diversity than they have today. With the end-Cretaceous extinction , the dinosaurs became extinct, with the exception of

1770-424: The extinction of all the pseudosuchians with the exception of Sphenosuchia and Crocodyliformes (both Crocodylomorpha ), the latter being the ancestors of modern-day crocodiles. A study published in 2010 postulates that there is significant evidence that volcanic eruptions changed the climate, causing a mass extinction that wiped out the dinosaurs' main competitors. This allowed the dinosaurs to succeed them as

1829-744: The first to establish the name Pseudosuchia in a phylogenetic context, using it as a branch-based taxon for all archosaurs more closely related to crocodilians than to birds. This made the name Pseudosuchia somewhat ironic because true crocodiles (i.e. members of Crocodylia) were now included in the group. Phylogenetic definitions of Pseudosuchia include "Crocodiles and all archosaurs closer to crocodiles than to birds" (Gauthier and Padian), "Extant crocodiles and all extinct archosaurs that are closer to crocodiles than they are to birds" (Gauthier, 1986), and more recently "the most inclusive clade within Archosauria that includes Crocodylia but not Aves" (Senter, 2005). As

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1888-421: The following synapomorphies: the presence of a deep fontanelle at the base of the basisphenoid, and the absence of a raised boss, specifically over the cervical paramedian scutes. In 2020, a phylogenetic analysis found Acaenasuchus to be closely related to Revueltosaurus and Euscolosuchus . Ongoing research classifies A. geoffreyi with other specimens' E. olseni and R. callendri as sister taxa to

1947-417: The form of small pits and grooves. The zygapophyses are situated close to each other along the midline of each trunk vertebrae. Sacral vertebrae identified in Acaenasuchus have been reconstructed from fragments of sacral ribs, sacral centra, and sacral vertebra. The centrum is amphicoelous and short much like the trunk vertebrae. The sacral rib is found on the anterior side of the centrum. The neural arch

2006-456: The four locations within the Adamanian LVF where Acaenasuchus holotypes have been excavated, two localities are a site of great abundance of adult Desmatosuchus fossils. While studies are ongoing, the majority of working paleontologists agree that Acaenasuchus should retain its status as a valid taxon, independent of Desmatosuchus. The "pitting" as an example of ontogenetic developments

2065-442: The group Aetosaurids, rather than a part of the group. This led to the study concluding that Acaenasuchus should be classified under the more broad clade of Aetosauroformes, due to the lateral osteoderms found on their carapace . [REDACTED] [REDACTED] [REDACTED] [REDACTED] Pseudosuchia Pseudosuchia (from Greek : ψεύδος (pseudos) , "false" and Greek : σούχος (souchos) , "crocodile")

2124-490: The heavily armored aetosaurs , and several were bipedal, such as Poposaurus and Postosuchus . The bizarre, ornithomimid -like shuvosaurids were both bipedal and herbivorous, with toothless beaks. Many of these Triassic pseudosuchian groups went extinct at or before the Triassic–Jurassic extinction event . However, one group, the crocodylomorphs , survived the major extinction. Crocodylomorphs themselves evolved

2183-417: The holotype UCMP 139576, 95 other scutes under 90 catalogue numbers likely also belong to Acaenasuchus . Another specimen, known as SMU 75403, was described by Marsh et al. (2020), and consists of representative cranial, vertebral, and appendicular elements as well as previously unknown variations in the dorsal carapace and ventral shield. The classification of Acaenasuchus as an independent taxon has been

2242-581: The humerus. The ilium is vertically oriented in Acaenasuchus . The lateral surface of the ilium does not have a second crest above the supra-acetabular crest but does have a tubercle between the supra-acetabular crest and the pre-acetabular process. The pre-acetabular process is short and faces anteriorly. Two rib attachment scars are observed on the medial side of the ilium. These scars indicate articulations with two sacral vertebrae. The iliac and ischiadic pedicles are not perforated in Acaenasuchus as they are in dinosauriformes. The obturator foramen perforates

2301-420: The introduction of plywood and later composite wood boards, but the method is still used in higher-quality boards. Plywood may also be tongued all round to fit it flush into a framed structure, and plywood for sub-floors used in platform framing is often supplied with tongue and groove edges. When joining thicker materials, several tongue and groove joints may be used one above the other. "Tongue and groove"

2360-472: The late Olenekian (early Triassic ); by the Ladinian (late Middle Triassic) they dominated the terrestrial carnivore niches. Their heyday was the Late Triassic, during which time their ranks included erect-limbed rauisuchians , herbivorous armored aetosaurs , the large predatory poposaurs , the small agile sphenosuchian crocodilians, and a few other assorted groups. The end-Triassic extinction caused

2419-399: The late 20th century, especially after the name Crurotarsi was established in 1990 to label the clade (evolutionary grouping) of archosaurs encompassing most reptiles previously identified as pseudosuchians. By this time, Pseudosuchia had also been defined as a clade , but it was not widely embraced until 2011. In 2011 paleontologist Sterling Nesbitt proposed that Crurotarsi, as it

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2478-412: The latter clade encompasses all crocodilian-line archosaurs in most phylogenetic analyses. Sterling Nesbitt 's 2011 analysis places one crurotarsan group, Phytosauria, outside Pseudosuchia. Since the definition of Crurotarsi relies on phytosaurs, their placement outside Pseudosuchia (and thus Archosauria) means that the clade Crurotarsi includes both pseudosuchians and avemetatarsalians. Pseudosuchia

2537-512: The name "false crocodiles". In mid-20th century textbooks, like Alfred Sherwood Romer 's Vertebrate Paleontology and Edwin H. Colbert 's Evolution of the Vertebrates , Pseudosuchia constitutes one of the suborders of the now-abandoned order Thecodontia . Zittel's aetosaurs were placed in their own suborder, Aetosauria. Colbert considered small lightly built archosaurs, such as Ornithosuchus and Hesperosuchus — both of which were at

2596-437: The only non-sacral vertebrae identified on Acaenasuchus thus far. Each is similar in size and includes centrum, neural arches, zygapophyses, and transverse processes. The centrum is amphicoelous, and includes longitudinal depressions on the lateral surfaces just below the neural arch. The neural arch is flat, similar to E. olseni, and dorsoventrally short. The most distal end of the transverse process includes ornamentation in

2655-412: The order Aetosauria which is recognized by the presence of a carapace indicated by paramedian and lateral scutes. The carapace is composed of two columns of each dorsal and lateral scutes which have the capacity to vary extensively between individual Aetosaurids. Acaenasuchus was assigned to the family Stagonolepididae by Irmis (2005). Stagonolepididae is the subfamily of Aetosauria and is described by

2714-501: The paramedian scutes, suggesting heavy armor on the dorsal surface when compared to the lateral surface. There are two types of "horn" structures observed on the lateral scutes. Conical horns curved dorsally, laterally, and posteriorly… and were wider than the scutes themselves. Conical horns typically displayed ornamentation such as furrows. Blunt horns showed less curvature and did not include ornamentation. Acaenasucus lateral scutes' lack anterior bars but possess anterior laminae. There

2773-410: The pre-sacral scutes. A division of the raised boss is also noted. The raised boss is absent on cervical paramedian scutes only. In addition to paramedian scute identification, lateral scutes have been similarly described on Acaenasuchus. Lateral scutes are features unique to Aetosaurids. The lateral scutes are longer than they are wide in Acaenasuchus . They have increased angulation when compared to

2832-403: The putative size of the taxa itself. They have decreased transverse angulation and include a transverse furrow on the dorsal face. Acaenasuchus paramedian scutes do not include the " tongue in groove " articulation with adjacent plates as seen on Desmatosuchus . Medial and lateral "wing" structures emanate from the ridges of the pre-sacral scutes. Deeply incised pitting is visualized posterior to

2891-408: The sister taxon of Archosauria, and therefore not crocodile-line archosaurs. Because phytosaurs are included in the definition of Crurotarsi, crurotarsans are not solely crocodile-line archosaurs, but also bird-line archosaurs and phytosaurs. Under this phylogeny, Crurotarsi includes phytosaurs, crocodiles, pterosaurs, and dinosaurs, while Pseudosuchia still contains only crocodile-line archosaurs. Below

2950-523: The time reconstructed as theropod dinosaur-like bipeds — to be typical pseudosuchians. These small forms were assumed to be the ancestors of all later archosaurs. The name Pseudosuchia became a wastebasket taxon into which all thecodonts that did not fit in the other three suborders could be placed. Even Sharovipteryx and Longisquama , two enigmatic Triassic reptiles that bear little resemblance to archosaurs, have been regarded as pseudosuchians. Gauthier and Padian (1985) and Gauthier (1986) became

3009-503: The topic of controversy due to its similarities to Desmatosuchus. Upon review by Andrew B. Heckert and Spencer G. Lucas, the characters that Long and Murry claim to distinguish between the two species may not represent novel scute features but rather ontogenetic variation . These characters include pitting over the dorsal scutes of Acaenasuchus and division between the raised boss into two flanges of Acaenasuchus, neither of which are present in Desmatosuchus. Heckert and Lucas argue that

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3068-600: The type fauna that belong to the Adamanian LVF , based on the fauna of the Blue Mesa Member of the Chinle Petrified Forest Formation of Arizona, where Acaenasuchus was initially discovered. The holotype , UCMP 139576 (a left dorsal paramedian scute ), was first discovered by Charles Lewis Camp in 1930. Camp initially named the species " Machaeroprosopus zuni ". By 1985, " Machaeroprosopus zuni"

3127-408: The visible pits and grooves over the dorsal scutes of Acaenasuchus indicate a juvenile stage of Desmatosuchus development. They elaborate that this pitting is a developmental ontogenetic feature that has been observed in the maturation process of other Aetosaurs , specifically in the taxa Aetosaurus . In addition to the ontogenetic variation hypothesis, Heckert and Lucas have determined that of

3186-470: Was away in the field". Long and Murry are credited for providing the most stable evidence that Acaenasuchus was an independent taxon. Long and Murry identified small dorsal plates along the carapace of Acaenasuchus, and identified what they described to be "ornithischian -like" teeth, in addition to a multitude of other proposed synapomorphies. Some of which are the subjects of active studies regarding Acaenasuchus characterization. The holotype UCMP 139576

3245-466: Was considered a synonym of Desmatosuchus , and was reclassified as a juvenile Desmatosuchus by Robert A. Long and Karen Ballew in 1985. UCMP 139576 was eventually moved into its own taxon and classified under the name Acaenasuchus , upon reclassification by Robert A. Long and Philip A. Murry in 1995. Fun Fact! The species epithet Acaenasuchus geoffreyi was named after Geoffrey Long, Robert A. Long's son, for his "considerable patience while his father

3304-537: Was discovered in the Petrified Forest Member of the Chinle Formation and belongs to a fully grown individual, as opposed to a juvenile as initially believed. The Upper Triassic Chinle Formation of Arizona is abundant with fossils belonging to over 18 different taxa groups. Collections from the 1890s onwards document various holotypes of these ranging taxa, including that of Acaenasuchus. In addition to

3363-483: Was highly flexible, allowing Acaenasuchus to move swiftly with agility. Caudal armor and pectoral spikes are lost in Acaenasuchus when compared to Desmatosuchus , further suggesting an evolutionary tradeoff between defense and armor in exchange for speed and agility. Most excavations of vertebrate fossils from the Chinle Formation occurred over floodplains, bogs, small ponds, and near other fluvial channels. Sandstone deposits represent channel systems flowing throughout

3422-404: Was not closely related to other traditional "crurotarsans", at least compared to avemetatarsalians such as pterosaurs and dinosaurs . As a result, Crurotarsi could be a much broader clade than Pseudosuchia. Other recent studies support a more traditional phylogeny. Contrary to popular belief, crocodilians differ significantly from their ancestors and distant relatives, as Pseudosuchia contains

3481-568: Was then defined, must include not only crocodilian-line archosaurs, but all other archosaurs including birds, non-avian dinosaurs , and pterosaurs . The clade Pseudosuchia as originally defined could still be used to identify crocodilian-line archosaurs, and since many recent studies support Nesbitt's findings, Pseudosuchia is again commonly used. The name Pseudosuchia was coined by Karl Alfred von Zittel in 1887–1890 to include three taxa (two aetosaurs and Dyoplax ) that were superficially crocodilian-like, but were not actually crocodilian. Hence

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