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A review of Late Jurassic stegosaurs (Dinosauria, Stegosauria) from the People’s Republic of China.
Abstract
Seven genera of stegosaurian dinosaur have been named on the basis of material from the Upper Jurassic of China, and this represents a diversity of stegosaurs unparalleled around the world at this time. However, many of the original specimens used to diagnose and describe these species are currently unavailable, and the original descriptions and figures are often inadequate. The Chinese stegosaurs have proven in the few cladistic analyses of Stegosauria that have been carried out, causing a loss of resolution in cladograms. Supplementary data on previously described specimens are presented here along with a taxonomic revision. Only Tuojiangosaurusmultispinus,Chungkingosaurusjiangbeiensis and Gigantspinosaurussichuanensis are considered to be valid taxa, with autapomorphies pertaining to features of the ilio-sacral blocks and dermal armour in all cases. The holotype specimen of is a juvenile, bearing no diagnostic characters, and is based on fragmentary and undiagnostic material. and have never been described or figured and their whereabouts are unknown, so they are regarded as nominanuda. This taxonomic revision significantly reduces known stegosaurian diversity worldwide, and shows that the Chinese diversity was similar to that of Europe and North America in the Upper Jurassic. Previously, it had been suggested that the diversity of Chinese stegosaurs indicated an Asian origin for the clade, a claim that cannot now be upheld.
... The anterior end of the premaxilla is incomplete, but the anterior process is sinuous in lateral view and curves ventrally, as in the stegosaurs Miragaia (Mateus, Maidment & Christiansen, 2009) and Huayangosaurus (Sereno & Dong, 1992), the ankylosaur Silvisaurus (NHMUK R1107) and the basal ornithischian Heterodontosaurus (Butler, Porro & Norman, 2008). This, however, contrasts to the horizontally-projecting process of the stegosaurs Chungkingosaurus (Maidment & Wei, 2006) and Stegosaurus stenops (NHMUK R36730), the ankylosaur Edmontonia (NHMUK R36851), and the basal ornithischian Lesothosaurus (Sereno, 1991). The posterior process of the premaxilla is robust and similar to that of the basal ornithischian Heterodontosaurus (Butler, Upchurch & Norman, 2008) and the ornithopods Camptosaurus (NHMUK R1608) and Jinzhousaurus (Wang & Xu, 2001) in that it intervenes between the maxilla and nasal to stop them contacting each other. ...
... This feature is, however, variable in stegosaurs; the same condition is seen in Huayangosaurus (Sereno & Dong, 1992), yet in Stegosaurus (NHMUK R36730) and Hesperosaurus (Carpenter, Miles & Cloward, 2001), the external nares face anteriorly. The external naris is longer anteroposteriorly than wide transversely in Paranthodon, similar to other stegosaurs such as Stegosaurus stenops (NHMUK R36730) and Chungkingosaurus (Maidment & Wei, 2006), and ornithopods such as Camptosaurus (NHMUK R1608) and Hypsilophodon (NHMUK R197). The condition is the same in the ankylosaurs Silvisaurus (NHMUK R1107), Europelta (Kirkland et al., 2013) andKunbarrasaurus (Leahey et al., 2015); in contrast, in the ankylosaurs Anodontosaurus (NHMUK R4947) and Edmontonia (NHMUK R36851) the naris is wider transversely than it is long anteroposteriorly. ...
... In ventral view, the tooth row is not inset from the lateral edge of the maxilla and is in line with the lateral edge of the premaxilla. This is similar to the condition in the stegosaur Tuojiangosaurus (Maidment & Wei, 2006) and the basal ornithischian Lesothosaurus (Sereno, 1991), but contrasts with all other members of Thyreophora, as well as ornithopods including Hypsilophodon (NHMUK R197), where there is a laterally-extending ridge dorsal to the tooth row. The tooth row is sinuous in ventral view, as in the basal thyreophoran Scelidosaurus (NHMUK R1111), the stegosaur Jiangjunosaurus ( Jia et al., 2007) and the ankylosaurs Anodontosaurus (NHMUK R4947), Gastonia (Kinneer, Carpenter & Shaw, 2016), Edmontonia (NHMUK R36851), Pawpawsaurus (Kinneer, Carpenter & Shaw, 2016), Panoplosaurus (Kirkland et al., 2013) and Silvisaurus (NHMUK R1107). ...
The first African dinosaur to be discovered, Paranthodon africanus was found in 1845 in the Lower Cretaceous of South Africa. Taxonomically assigned to numerous groups since discovery, in 1981 it was described as a stegosaur, a group of armoured ornithischian dinosaurs characterised by bizarre plates and spines extending from the neck to the tail. This assignment has been subsequently accepted. The type material consists of a premaxilla, maxilla, a nasal, and a vertebra, and contains no synapomorphies of Stegosauria. Several features of the maxilla and dentition are reminiscent of Ankylosauria, the sister-taxon to Stegosauria, and the premaxilla appears superficially similar to that of some ornithopods. The vertebral material has never been described, and since the last description of the specimen, there have been numerous discoveries of thyreophoran material potentially pertinent to establishing the taxonomic assignment of the specimen. An investigation of the taxonomic and systematic position of Paranthodon is therefore warranted. This study provides a detailed re-description, including the first description of the vertebra. Numerous phylogenetic analyses demonstrate that the systematic position of Paranthodon is highly labile and subject to change depending on which exemplifier for the clade Stegosauria is used. The results indicate that the use of a basal exemplifier may not result in the correct phylogenetic position of a taxon being recovered if the taxon displays character states more derived than those of the basal exemplifier, and we recommend the use, minimally, of one basal and one derived exemplifier per clade. Paranthodon is most robustly recovered as a stegosaur in our analyses, meaning it is one of the youngest and southernmost stegosaurs.
... The anterior articular facet of the centrum is sub-circular in outline and flat, with a central concavity that might be due to erosion (Fig 18A). This contrasts with the condition in Chungkingosaurus (CV 206), where the anterior articular facet is convex and the centrum is opisthocoelous, a feature not previously noted by either [34] or [35]. The posterior articular facet is also sub-circular in outline and flat with a small central pit ( Fig 18B). ...
... 4B; 9E) from Portugal in that they possess a ventrolateral corner on the ventrolateral margin of the preacetabular process, and they taper to a point anteriorly. The angle between the preacetabular process and the acetabular region is much lower in Tuojiangosaurus (CV 209/210; [34]; [35] : fig 2a), Chungkingosaurus (CV 206; [34]; [35]: fig 2b) and Huayangosaurus (ZDM T7001; [31]: fig 29; [26]: fig 5a) and describes a gentle arc rather than a right angle, as it does in NHMUK PV R36730. ...
... 4B; 9E) from Portugal in that they possess a ventrolateral corner on the ventrolateral margin of the preacetabular process, and they taper to a point anteriorly. The angle between the preacetabular process and the acetabular region is much lower in Tuojiangosaurus (CV 209/210; [34]; [35] : fig 2a), Chungkingosaurus (CV 206; [34]; [35]: fig 2b) and Huayangosaurus (ZDM T7001; [31]: fig 29; [26]: fig 5a) and describes a gentle arc rather than a right angle, as it does in NHMUK PV R36730. ...
Although Stegosaurus is one of the most iconic dinosaurs, well-preserved fossils are rare and as a consequence there is still much that remains unknown about the taxon. A new, exceptionally complete individual affords the opportunity to describe the anatomy of Stego-saurus in detail for the first time in over a century, and enables additional comparisons with other stegosaurian dinosaurs. The new specimen is from the Red Canyon Ranch Quarry, near Shell Wyoming, and appears to have been so well preserved because it was buried rapidly in a pond or body of standing water immediately after death. The quarry is probably located in the middle part of the Morrison Formation, which is believed to be Tithonian in age in this area. The specimen is referable to Stegosaurus stenops based on the possession of an edentulous anterior portion of the dentary and elevated postzygapophyses on the cervical vertebrae. New information provided by the specimen concerns the morphology of the vertebrae, the iliosacral block and dermal armor. Several aspects of its morphology indicate the individual was not fully skeletally mature at the time of death, corroborating a previous histological study.
... The preacetabular shelf and associated crest are present in Scelidosaurus, although are not as well developed. They are absent in Huayangosaurus and most stegosaurs, except Dacentrurus (BMNH 46013) and an unnamed Dacentrurus-like pelvis from China ( [16] fig. 5f ). ...
... This trapezoid shape is different from that seen in other ornithischians (e.g., Camptosaurus CM 11337), in which the sacral ribs form an hour-glass shape, being shortest adjacent to the acetabulum; an inverse hour-glass in which the sacral ribs are longest in the middle is seen in ceratopsians ( [37] fig. 55) and stegosaurs (see [16] The synsacrum of Scelidosaurus is comprised of at least the first presacral (i.e., last dorsal vertebra) closely appressed against the first sacral (although these have now been separated by acid preparation). The opposing articular surfaces of the dorsal and sacral centra are somewhat irregular and interlocking, thus resembling the typical irregular surface between sacral vertebrae of immature dinosaurs and implies the two vertebrae of Scelidosaurus were tightly interlocked. ...
... The postacetabulum is subhorizontal, as is the dorsal plate. The lateral process (supra-acetabular process of [16]) is reinforced ventrally by a ridge forming a robust buttress. An early ontogenetic series of Stegosaurus ilia (Fig. 12) show that the lateral process is not formed by the dorsal rim of the postacetabular rotating laterally to a horizontal position. ...
Discovery of a pelvis attributed to the Late Jurassic armor-plated dinosaur Gargoyleosaurus sheds new light on the origin of the peculiar non-vertical, broad, flaring pelvis of ankylosaurs. It further substantiates separation of the two ankylosaurs from the Morrison Formation of the western United States, Gargoyleosaurus and Mymoorapelta. Although horizontally oriented and lacking the medial curve of the preacetabular process seen in Mymoorapelta, the new ilium shows little of the lateral flaring seen in the pelvis of Cretaceous ankylosaurs. Comparison with the basal thyreophoran Scelidosaurus demonstrates that the ilium in ankylosaurs did not develop entirely by lateral rotation as is commonly believed. Rather, the preacetabular process rotated medially and ventrally and the postacetabular process rotated in opposition, i.e., lateral and ventrally. Thus, the dorsal surfaces of the preacetabular and postacetabular processes are not homologous. In contrast, a series of juvenile Stegosaurus ilia show that the postacetabular process rotated dorsally ontogenetically. Thus, the pelvis of the two major types of Thyreophora most likely developed independently. Examination of other ornithischians show that a non-vertical ilium had developed independently in several different lineages, including ceratopsids, pachycephalosaurs, and iguanodonts. Therefore, a separate origin for the non-vertical ilium in stegosaurs and ankylosaurs does have precedent.
... 2. The above-mentioned presence of unstable taxa partially reflects the fact that scoring of some taxa in the data matrix was based largely on the published literature rather than on firsthand observation of the specimens. Much of the literature on many genera, especially those from Asia, was written before the widespread use of cladistic methodologies among dinosaur workers and often lacks the descriptive detail that has become necessary for character determination (Maidment & Wei 2006;Maidment et al. 2006). In addition, older descriptions of some genera do not differentiate between genuine observable characteristics and inferred reconstructed characteristics in figures (e.g. ...
... 2. The above-mentioned presence of unstable taxa partially reflects the fact that scoring of some taxa in the data matrix was based largely on the published literature rather than on firsthand observation of the specimens. Much of the literature on many genera, especially those from Asia, was written before the widespread use of cladistic methodologies among dinosaur workers and often lacks the descriptive detail that has become necessary for character determination (Maidment & Wei 2006;Maidment et al. 2006). In addition, older descriptions of some genera do not differentiate between genuine observable characteristics and inferred reconstructed characteristics in figures (e.g. ...
... Dong et al. 1983;Marsh in Ostrom & McIntosh 1999), leading to incorrect scoring of some features in the data matrix. Maidment et al. (2006) carried out a preliminary cladistic analysis of the relationships of several thyreophoran dinosaurs, including two basal thyreophorans, six stegosaurs and two ankylosaurs. The analysis was effectively an early version of the results presented here; the aim of the analysis was to provide a framework on to which character state changes relevant to the basal stegosaur Huayangosaurus could be plotted, and to resolve the position of the basal thyreophoran Scelidosaurus. ...
Stegosauria is a clade of ornithischian dinosaurs characterised by a bizarre array of dermal armour extending, in two parasagittal rows, from the cervical region to the end of the tail. Although Stegosaurus is one of the most familiar of all dinosaurs, little is known regarding the evolutionary history of this clade.Alpha‐level taxonomic revision of all proposed stegosaur taxa shows that 11 species of stego‐saur can be regarded as valid on the basis of autapomorphies. These are: Dacentrurus armatus and Loricatosaurus priscus (gen. nov.) from Europe; Kentrosaurus aethiopicus and Paranthodon afric‐anus from Africa; Tuojiangosaurus multispinus, Chungkingosaurus jiangbeiensis, Huayangosaurus taibaii, Gigantspinosaurus sichuanensis and Stegosaurus homheni (comb. nov.) from China; and Stegosaurus mjosi (comb. nov.) and Stegosaurus armatus from North America.A cladistic analysis of Stegosauria (the first to be based upon direct observation of all relevant specimens) is presented, which indicates that Tuojiangosaurus, Loricatosaurus and Paranthodon are sister taxa to Stegosaurus. Stegosaurinae can be defined as all stegosaurs more closely related to Stegosaurus than to Dacentrurus; Stegosauridae is defined as all stegosaurs more closely related to Stegosaurus than to Huayangosaurus; and Huayangosauridae can be defined as all stegosaurs more closely related to Huayangosaurus than to Stegosaurus. This study is also the first phylogenetic analysis to include Gigantspinosaurus, which is recovered as the most basal stegosaur.
... Unfortunately, many of these specimens were not further studied in detail and no relevant papers were published. Zhao (1983) reported dinosaur species Monkonosaurus lawulacus from the Lawu Mountain in Mangkang (Mangkam) County, Qamdo area, which was later suggested as an invalid species (Maidment and Wei, 2006) or attributed to the clade of Stegosauria (Dong, 1990;Dong et al., 2015). Zhao (1985) also reported dinosaurs (e.g., Lufengosaurus changduensis, Damalasaurus magnus, Megalosaurus tibetensis) and aquatic reptiles (e.g., Ichthyosaurus changduensis, Plesiosaurus changduensis, and Steneosuchus microobtusidens) from the Lower Jurassic Daye Formation in the Qamdo area. ...
... Tibet is one of the least studied regions in China in terms of dinosaur palaeobiology, despite situating close to Yunnan and Sichuan which are iconic localities of Jurassic dinosaur fossils (Young, 1939;Mao et al., 2020). Although systematic investigation into Tibet's dinosaur is in its infancy, the known specimens indicate a diverse dinosaurian fauna consisting of sauropods, theropods and stegosaurians in Qamdo of eastern Tibet (Maidment and Wei, 2006;An et al., 2021). The new eusauropod limb bones from Qamdo likely belong to individuals of varying body sizes (6-20 m long) based on comparisons with other sauropods from Southwest China. ...
... Stegosauria is a clade of dinosaurs characterized by the possession of two parasagittal rows of dermal armour extending from the neck to the end of the tail. Although progress has been made concerning our understanding of the morphology and phylogeny of stegosaurs (Dong et al. 1982;Zhou et al., 1984;Maidment and Wei 2006;Jia et al. 2007;Maidment et al., 2008;Maidment 2010;Maidment et al. 2015;Raven and Maidment 2017), the record of illness or injury in stegosaurs has been reported less frequently (Carpenter et al. 2005). Gigantspinosaurus sichuanensis is a stegosaur found in the Upper Shaximiao Formation (Late Jurassic) of Zigong, Sichuan Province, People's Republic of China. ...
... The complete, articulated skeleton was excavated from the Upper Shaximiao Formation of Pengtang in Yinhe Village, Zhongquan Town, Zigong City, Sichuan Province in 1985. The Upper Shaximiao Formation has yielded a diversity of fossils known as the 'Mamenchisaurus Fauna', and includes the other stegosaurs Tuojiangosaurus multispinus, and Chungkingosaurus jiangbeiensis (Dong et al. 1983;Peng et al. 2005;Maidment and Wei 2006). Recent isotopic dating of the Lower Shaximiao Formation, which underlies the Upper Shaximiao Formation, places it at 159 ± 2 Ma , suggesting that the Upper Shaximiao Formation is likely to be Kimmeridgian to Tithonian in age. ...
We report a case of a specific osteopathy in the stegosaurian dinosaur Gigantspinosaurus sichuanensis from the Late Jurassic of Zigong City, China. The G. sichuanensis skeleton is very complete. The left femur has obvious pathological characteristics based on morphological observations. CT scans and energy spectrum data indicate the presence of multiple cystic-like low density areas internal to the pathological area, which are present in the form of multiple cystic low-density shadows in the CT data. This contrasts with the ‘normal’ area, which does not possess these characteristics. After comparing the specimen with the pathologic scapula of Yangchuanosaurus hepingensis (Dinosauria: Theropoda) also found in Zigong, we consider that the pathology in the left femur of G. sichuanensis was probably caused by a bone tumor. This is the first analysis with the aid of energy spectrum CT scanning of bone disease in fossils. This study increases the known information about paleopathology of stegosaurian dinosaurs and enriches the pathological knowledge of dinosaurs in general.
... In interpreting the results must be considered that the stegosaurs result in general rare as fossils (see Raven and Maidment 2017). However, it has been shown on an empirical basis that the sum of variance can be considered more robust with respect to irregular sampling over time (Wills et al. 1994;Brusatte et al. 2012;Butler et al. 2012), whereas the sum of ranges is more robust in relation to taxonomic splitting or lumping (Wills et al. 1994; In recent decades several phylogenesis for stegosaurids have been presented in the literature (Sereno and Zhimin 1992;Sereno 1999;Galton and Upchurch 2004;Maidment and Wei 2006;Escaso et al. 2007;Mateus et al. 2009), however that performed by Raven and Maidment (2017) results to date the most comprehensive in terms of considered taxa and characters identified (both continuous and discrete); so the matrix of this phylogeny was chosen for the present study of the relationship between disparity and diversity through time. By using a consistent number of continuous characters (based mainly on the post-cranium) Raven and Maidment (2017) Raven and Maidment 2017). ...
... Despite the great number of phylogenetic analyzes and taxonomic reviews presented in the literature (e.g. Carpenter and Galton 2001;Maidment and Wei 2006;Carpenter 2010;Galton 2010;Maidment 2010), as stressed by Raven and Maidment (2017) 'much remains unknown about the palaeobiology and palaeoecology of the clade' . Traditionally, more general studies on the paleobiology of stegosaurs have been focused on the significance and functional morphology of the bizarre dermal plates (e.g. ...
The Stegosauria represents an iconic group of ornithischian dinosaurs, with a fossil record spanning the Middle Jurassic to the Late Cretaceous. In this contribution I present the first detailed analysis of the relationship between disparity and diversity through the evolutionary history of the group. The analysis has been performed on a recently published cladistic dataset, allowing the separate study of the signals deriving from discrete characters and from continuous morphometric characters. Whereas the disparity as sum of variance is decoupled with respect to diversity, the sum of ranges provides a signal fairly consistent with the trend in the number of taxa. Both sub-data sets show that evolution of stegosaurs can be considered essentially as symmetrical, i.e. the maximum exploration of the possible morphospace takes place about half way through the history of the group, with subsequent significant decline until extinction in the Upper Cretaceous. An interesting result is a decoupling of the tempo and mode of evolution of the cranium and postcranium in stegosaurs. Specifically, the evolutionary radiation with maximum saturation of morphospace is anticipated in the cranial skeleton, with maximum peak in the Oxfordian; in contrast, the postcranium explores the largest number of morphotypes subsequently during the Kimmeridgian.
... Middle Jurassic terrestrial crocodiles from Asia include a goniopholid and the enigmatic Hsisosuchus from the Lower Shixaniao Formation (Peng et al. 2005), as well as a "sphenosuchian" from the Wuceiwan Formation (Clark et al. 2004) and a goniopholid from the Totunhe Formation in China (Maisch et al. 2003), and a report of a goniopholid from Kirghizia (Averianov 2000). The most important Middle Jurassic dinosaur fauna from the Northern Hemisphere is that of the (?) Bathonian Lower Shaximiao Formation of China (Peng et al. 2005), which includes stegosaurian (Maidment and Wei 2006) and basal cerapodan ornithischians (Barrett et al. 2005), theropods, and sauropods. Theropods include basal tetanurans, such as Xuanhanosaurus and "Szechuanosaurus" zigongensis (Dong 1984, Gao 1993, and the possible basal coelurosaur Gasosaurus (Dong andTang 1985, Holtz et al. 2004). ...
... Late Jurassic pterosaurs from Asia are rare, but include at least the ctenochasmatid Huanhepterus (Dong 1982). Dinosaurs from the Late Jurassic of Asia include sinraptorid allosauroids, mamenchisaurid sauropods, and stegosaurian and ornithopodan ornithischians , Peng et al. 2005, Maidment and Wei 2006. Furthermore, the oldest ceratopsian ornithischians are known from the Tithonian Tuchengzi and the Oxfordian Shishougou formations of China (Zhao et al. 1999, Xu et al. 2006b, and the latter unit has also yielded the basal tyrannosauroid Guanlong (Xu et al. 2006a) and the first ceratosaurs from Asia . ...
... The ribs are 'T'-shaped in cross-section, with an anteroposteriorly broad dorsal surface. Large, oval fenestrae separate each rib in dorsal view, similar to the arrangement seen in other Chinese stegosaurs such as Tuojiangosaurus (CV 209/210) and Chungkingosaurus (CV 206: Maidment and Wei, 2006), and basal thyreophorans such as Scelidosaurus (BMNH R1111: Fig. 5D). ...
... The small plates reach maximum heights of 15-20 cm and have markedly asymmetric bases that are thickened, pitted, and rugose. The spines are very similar to those of Kentrosaurus (Fig. 7B) and IVPP V2300 ("Chialingosaurus": Maidment and Wei, 2006). The bases of the spines, although rugose, are less markedly asymmetric and there is little evidence to suggest from which side of the body they are derived, although it can be seen that many of them would have projected posterodorsally. ...
Previous descriptions of the postcranial skeleton of the primitive stegosaur Huayangosaurus taibaii (Middle Jurassic: People's Republic of China) are insufficient for character determinations in cladistic analysis. Reexamination of the postcranium has revealed several important characters, most of which are retained plesiomorphies that have not been identified previously. For example, Huayangosaurus retains ossified tendons, the loss of which has been used as a synapomorphy of Stegosauria. These purported stegosaurian synapomorphies now serve to unite the monophyletic clade Stegosauridae, defined as all stegosaurs more closely related to Stegosaurus than to Huayangosaurus. In addition, some anatomical characters previously used as ‘ankylosauromorph’ synapomorphies have now been identified in Huayangosaurus: this suggests that these characters occur more basally within Thyreophora. The plesiomorphic status of Huayangosaurus suggests that substantial convergence between ankylosaurs and stegosaurs occurred during their respective evolutionary histories, reflecting coincident functional morphological changes associated with the adoption of obligate quadrupedality.
... Middle Jurassic terrestrial crocodiles from Asia include a goniopholid and the enigmatic Hsisosuchus from the Lower Shixaniao Formation (Peng et al. 2005), as well as a "sphenosuchian" from the Wuceiwan Formation (Clark et al. 2004) and a goniopholid from the Totunhe Formation in China (Maisch et al. 2003), and a report of a goniopholid from Kirghizia (Averianov 2000). The most important Middle Jurassic dinosaur fauna from the Northern Hemisphere is that of the (?) Bathonian Lower Shaximiao Formation of China (Peng et al. 2005), which includes stegosaurian (Maidment and Wei 2006 ) and basal cerapodan ornithischians (Barrett et al. 2005), theropods, and sauropods. Theropods include basal tetanurans, such as Xuanhanosaurus and "Szechuanosaurus" zigongensis (Dong 1984, Gao 1993 ), and the possible basal coelurosaur Gasosaurus ( Tang 1985, Holtz et al. 2004). ...
... Late Jurassic pterosaurs from Asia are rare, but include at least the ctenochasmatid Huanhepterus (Dong 1982). Dinosaurs from the Late Jurassic of Asia include sinraptorid allosauroids, mamenchisaurid sauropods, and stegosaurian and ornithopodan ornithischians (, Peng et al. 2005, Maidment and Wei 2006). Furthermore, the oldest ceratopsian ornithischians are known from the Tithonian Tuchengzi and the Oxfordian Shishougou formations of China (Zhao et al. 1999, Xu et al. 2006b ), and the latter unit has also yielded the basal tyrannosauroid Guanlong (Xu et al. 2006a) and the first ceratosaurs from Asia (). ...
The fossil record of archosaurs - crocodylomorphs, pterosaurs and dinosaurs - from the Jurassic of the Southern Hemisphere is critically reviewed, and its evolutionary implications are evaluated. Although several important faunas and also isolated finds are known from Gondwana, the record in total is still very patchy, and any evolutionary scenario based on this record should be seen as tentative. Compared to the Northern Hemisphere, southern archosaurs are much more poorly known, which is especially true for terrestrial crocodiles and pterosaurs. Marine crocodiles are rather well represented in south-western South America, whereas the report of terrestrial archosaurs is currently best for Africa. However, in South America, important and especially promising archosaur faunas are known from the Callovian Cañadón Asfalto and the (?)Tithonian Cañadón Calcáreo formations of Chubut province, Argentina. Early and Middle Jurassic Gondwanan archosaurs demonstrate that the faunas of that period still had a generally Pangean distribution, whereas first indications of differential archosaur evolution in the Northern and Southern Hemispheres are evident in Late Jurassic Gondwanan faunas.
... Acantholipan is from the Santonian of Mexico, is represented by an extremely fragmentary postcranium, and was originally described as a nodosaurid (Rivera-Sylva et al., 2011, whereas Euoplocephalus is a well-known ankylosaurid from the Campanian-Maastrichtian of North America (Arbour & Currie, 2013a). Mongolostegus is the youngest stegosaur, from the Aptian-Albian of Mongolia, and is highly fragmentary (Tumanova & Alifanov, 2018), whereas Chungkingosaurus is from the Late Jurassic of the People's Republic of China (Dong et al., 1983;Maidment & Wei, 2006). The character completeness scores for Acantholipan and Mongolostegus are extremely low (2.9% and 3.2%, respectively; Table 3), compared to those of Euoplocephalus and Chungkingosaurus (79.7% and 26.2%, respectively), and it is likely the two former taxa were identified as taxonomic equivalents of the latter due to a lack of scorable character states. ...
... -There are no records of basal neornithischian skeletons and tracks in the Changdu area. However, the tracks of thyreophorans described in this paper might correspond to the possible stegosaur 'Changdusaurus' (Zhao 1985;Maidment and Wei 2006). The records of thyreophorans from the Changdu area also correspond to cf. ...
We report five new dinosaur track sites in Chaya County, about 120 km southeast of Changdu City. The track assemblages are dominated by sauropods (45 tracks), which have been identified tentatively as cf. Brontopodus. Also present are two thyreophoran trackways consisting of 13 tracks that show strong similarities with the ichnogenus Deltapodus, the potential trackmakers of which were probably stegosaurids. The sauropod tracks from the Chaya region are dominated by large tracks with different affinities if compared to those of the Changdu area. The isolated sauropod tracks from Changdu and Chaya regions show similar morphological patterns, but those from the Chaya region lack large scale tracks. This paper compares and discusses the known ichno and body fossil records of sauropods, theropods, and ornithischians from the Middle Jurassic of Yunnan, Sichuan, and eastern Tibet and their importance for our understanding of dinosaur faunas from this region. The absence of basal neornithischian records in the
Yunnan and Changdu regions is likely a preservational bias but also an ecological pecularity cannot be completely excluded. The palaeogeographic position of the four sampled skeleton and track sites suggests the possible existence of a corridor through which faunal exchanges were taking place throughout the Jurassic.
... In stegosaurs, such an expansion is present in Huayangosaurus (Zhou, 1984), Dacentrurus (Owen, 1875;Galton, 1985;Costa and Mateus, 2019), Hesperosaurus , Kentrosaurus ( Fig. 4B; Hennig, 1925;Galton, 1982), Stegosaurus Fig. 4C; Gilmore, 1914), Loricatosaurus (Galton, 1985(Galton, , 1990, Miragaia (ML 433) and a humerus referred to Chungkingosaurus (Dong et al., 1983: fig. 100; though see Maidment and Wei, 2006, for the taxonomic identification of this element), but apparently not in Adratiklit (somewhat uncertain as the humerus is strongly compressed; Maidment et al., 2020) and, possibly, Tuojiangosaurus (Dong et al., 1983:pl. 39 , fig. 3). ...
A stegosaurian humerus from the Oxfordian–Tithonian(?) Cañadón Calcáreo Formation of Chubut, Argentina, extends the fossil record of this clade of thyreophoran ornithischian dinosaurs to the Upper Jurassic of South America. The element shares the derived character of an oblique ridge extending from the deltopectoral crest towards the medial distal condyle with taxa such as Kentrosaurus and Stegosaurus and thus represents a derived representative of the clade. The presence of stegosaurs in the Cañadón Calcáreo Formation underlines the similarities of its dinosaur fauna with other Late Jurassic dinosaur faunas, such as the Morrison Formation of North America or the Tendaguru Formation of Tanzania, in at least broad systematic terms.
... However, in MG 4863 both are deep, with the proximal postpubis only marginally less deep than the prepubis. As a result of this and the large and round acetabular process, the obturator notch is closed in lateral view (as the margins of the postpubis and acetabular process clearly overlap each other medially), a condition that is observable in no other stegosaur species besides Huayangosaurus [109]. The posterior edge of the acetabular process of the pubis of NHMUK OR46013 is broken [27] and appears to have been reconstructed since with plaster, but at least anteriorly the obturator notch would still be open, and it is unlikely it overlapped posteriorly the postpubis. ...
The stegosaur species Miragaia longicollum was erected based on a partial anterior skeleton from the Upper Jurassic of Portugal. Until then, almost all stegosaur specimens in Portugal and Spain had been identified as Dacentrurus armatus, the sister taxon of M. longicollum and only other member of the clade Dacentrurinae. The holotypes of the two species have little overlap, since the holotype of D. armatus is mostly a posterior skeleton, so the classification of other specimens to either species is unclear and the validity of M. longicollum has been questioned and debated. Here we describe a largely complete specimen of M. longicollum discovered in 1959 in Atouguia da Baleia, Peniche, Portugal, consisting of both anterior and posterior portions of the skeleton. Comparisons to the holotypes of dacentrurines and other stegosaurs shed light on the convoluted relationships of this group. We conclude that M. longicollum is valid and rather different from D. armatus, and provide a revised diagnosis of M. longicollum, as well as revised diagnoses for D. armatus, Dacentrurinae, and the first diagnosis of the genus Miragaia, granting stability to these taxa and allowing new considerations to be given on the classification of other Iberian stegosaurs. This new specimen is, to date, the most complete dinosaur described from Portugal and the most complete stegosaur described from Europe. Miragaia shared anatomical features that show a close affinity to Alcovasaurus longispinus, confirming this to be the first known dacentrurine stegosaur in America, coherent with the hypothesis of an ephemeral land bridge between North America and Iberia that allowed faunal exchange.
... Stegosaurian thyreophorans were widely distributed in western China: remains have been discovered in Middle JurassiceLower Cretaceous strata in Sichuan (Sichuan basin), Xinjiang (Junggar basin), Tibet (Mangkang basin), and Nei Mongol (Ordos basin) (Maidment and Wei, 2006;Dong, 2009). However, despite reports of ostensibly stegosaurian (cf. ...
... Monkonosaurus lawulacus from Tibet is based on a complete sacrum with ilia, two partial vertebrae and three dermal plates (Dong 1990). Maidment & Wei (2006) considered the species to be a nomen dubium. Its age is uncertain: Dong (1990) regarded the Loe-ein Formation to be of Late Jurassic to Early Cretaceous age. ...
Pereda-Suberbiola, X., Galton, P.M., Mallison, H. & Novas, F. iFirst article. A plated dinosaur (Ornithischia, Stegosauria) from the Early Cretaceous of Argentina, South America: an evaluation. Alcheringa, 1–14. ISSN 0311-5518.A re-evaluation of several vertebrae and dermal plates from the Lower Cretaceous (La Amarga Formation, Puesto Antigual Member; Barremian–lower Aptian) of Neuquén in Argentina, originally described as a stegosaurian dinosaur and recently referred to an indeterminate ornithischian, confirms the former identification. The Neuquén remains have a combination of features that is only known among stegosaurs: cervical vertebrae with a proportionally large cross-section of the neural canal, the anterior height and width of which are half the height of the anterior centrum, as in the cervical vertebrae of Kentrosaurus, Dacentrurus and Stegosaurus; prominent lateral depressions on the cervical centra, as in the presacral vertebrae of Dacentrurus; and cervical dermal plates that are subtriangular, longer than high and reminiscent of those of Miragaia. Moreover, a small bone here interpreted to be an anterior supraorbital (= first palpebral) is similar to that of Stegosaurus and other stegosaurs in having an elongate form and a dorsal rugose surface. The remains from Argentina exhibit some differences relative to other stegosaurs, suggesting that it is potentially a distinct taxon, but their incompleteness advises against the erection of a new genus and species. Interestingly, it is the only known skeletal record of Stegosauria in South America. It provides the second conclusive evidence of the presence of this clade in the Early Cretaceous of the Gondwanan landmasses.
... The slightly more conspicuous Middle Jurassic record of ornithischians includes the first stegosaurs and ankylosaurs within Thyreophora and an array of basal neornithischians. The Lower Shaximiao Formation of China (Peng et al., 2005) has yielded stegosaurs (Maidment & Wei, 2006) and neornithischians (Barrett et al., 2005a), while the former group was recorded along with a possible pachycephalosaur from the Balabansai Formation of Kirghizia (Averianov, Martin & Bakirov, 2005;Averianov, Bakirov & Martin, 2007). In Europe, Middle Jurassic ornithischians are represented by basal ornithopods (Galton, 1980;Evans & Milner, 1994, Kriwet, Rauhut & Gloy, 1997Ruiz-Omeñaca, Suberbiola & Galton, 2005), stegosaurs (Galton & Powell, 1983, Galton, 1990, and ankylosaurs (Galton, 1983a). ...
The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and Spondylosoma absconditum. The identification of dinosaur apomorphies is jeopardized by the incompleteness of skeletal remains attributed to most basal dinosauromorphs, the skulls and forelimbs of which are particularly poorly known. Nonetheless, Dinosauria can be diagnosed by a suite of derived traits, most of which are related to the anatomy of the pelvic girdle and limb. Some of these are connected to the acquisition of a fully erect bipedal gait, which has been traditionally suggested to represent a key adaptation that allowed, or even promoted, dinosaur radiation during Late Triassic times. Yet, contrary to the classical "competitive" models, dinosaurs did not gradually replace other terrestrial tetrapods over the Late Triassic. In fact, the radiation of the group comprises at least three landmark moments, separated by controversial (Carnian-Norian, Triassic-Jurassic) extinction events. These are mainly characterized by early diversification in Carnian times, a Norian increase in diversity and (especially) abundance, and the occupation of new niches from the Early Jurassic onwards. Dinosaurs arose from fully bipedal ancestors, the diet of which may have been carnivorous or omnivorous. Whereas the oldest dinosaurs were geographically restricted to south Pangea, including rare ornithischians and more abundant basal members of the saurischian lineage, the group achieved a nearly global distribution by the latest Triassic, especially with the radiation of saurischian groups such as "prosauropods" and coelophysoids.
... ; S. C. R. Maidment 2005, personal observations) while Scelidosaurus had eight cervical vertebrae (S. C. R. Maidment 2005, personal observations, see the electronic supplementary material). The basal stegosaur Huayangosaurus had nine cervical vertebrae (Maidment et al. 2006 ...
Stegosaurian dinosaurs have a quadrupedal stance, short forelimbs, short necks, and are generally considered to be low browsers. A new stegosaur, Miragaia longicollum gen. et sp. nov., from the Late Jurassic of Portugal, has a neck comprising at least 17 cervical vertebrae. This is eight additional cervical vertebrae when compared with the ancestral condition seen in basal ornithischians such as Scutellosaurus. Miragaia has a higher cervical count than most of the iconically long-necked sauropod dinosaurs. Long neck length has been achieved by 'cervicalization' of anterior dorsal vertebrae and probable lengthening of centra. All these anatomical features are evolutionarily convergent with those exhibited in the necks of sauropod dinosaurs. Miragaia longicollum is based upon a partial articulated skeleton, and includes the only known cranial remains from any European stegosaur. A well-resolved phylogeny supports a new clade that unites Miragaia and Dacentrurus as the sister group to Stegosaurus; this new topology challenges the common view of Dacentrurus as a basal stegosaur.
Jurassic strata are widely distributed in the eastern part of Tibet Autonomous Region, and have yielded many dinosaur bones. However, none of these specimens has been studied extensively, and some remain unprepared. Here we provide a detailed description of some new sauropod material, including several cervical vertebrae and a nearly complete scapula, recovered from the Middle Jurassic of Chaya County, East Tibet. The cervical vertebrae have short centra that bear ventral midline keels, as in many non-neosauropod sauropods such as Shunosaurus . Moreover, the cervical centra display deep lateral excavations, partitioned by a septum. The scapula has proximal and distal ends that are both expanded as in mamenchisaurids and neosauropods. However, relatively small body size and lack of fusion of neurocentral sutures in the cervical vertebrae suggest that the available material is from a juvenile, and the length of the cervical centra may have increased relative to the size of the rest of the skeleton in later ontogenetic stages. Phylogenetic analysis provides limited evidence that the new Tibetan sauropod specimen belongs to Eusauropoda, being more derived than Shunosaurus , but is basal to Mamenchisauridae. The new material provides important information on the morphological transition between Shunosaurus and mamenchisaurids, and extends the known biogeographic range of early-diverging sauropods in the Middle Jurassic of East Asia.
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Modern carnivore communities include species that span a range of body sizes. For example, on the African savannah, there are small species (mongooses), medium species (wild dogs), and large species (lions). This variation reflects available prey sources that best suit each group. Carnivorous dinosaur communities, however, were missing species that fall into the middle, or mesocarnivore, group as adults. Schroeder et al. looked across communities, space, and time and found that this absence appears to have been driven by the distinctive biology of dinosaurs, in which giant adults start out as tiny hatchlings. Growing juvenile dinosaurs thus filled the other niches and limited trophic species diversity.
Science , this issue p. 941
The first Mongolian stegosaur, Mongolostegus exspectabilis gen. et sp. nov., Stegosauridae (Ornithischia), represented by a series of anterior caudal vertebrae and bones of the pelvic girdle is described. The vertebral structure and massiveness and morphological features of pubic bones provide a unique combination of features, allowing recognition of diagnostic characters. The new taxon comes from the Aptian–Albian deposits of the Khamryn-Us locality (Mongolia) and belongs to the latest Stegosauridae (Ornithschia).
Gigantspinosaurus sichuanensis is one of the six Stegosauria genera discovered from the Sichuan basin, which preserves the first skin impressions of stegosaurs around the world and a huge pair of ‘comma’ ‐shaped parascapular spines kept in situ, and being named after the latter feature. The holotype was firstly named and reported in an abstract of a lecture by Ouyang, 1992, since when it has never been detailed studied and the taxonomic position of Gigantspinosaurus is also vague. The morphological redescription shows that G. sichuanensis is a medium‐sized stegosaur, with external mandibular foramen developed. The ratio of femur to humerus is large, and the intersacral fenestrae are big. According to the wear degree of teeth, the holotype of G. sichuanensis is regarded as an adult individual. On the basis of the recent data matrix of stegosaurs and the characters revisions of G. sichuanensis, its phylogenetic position has been determined again. By our detailed morphological and phylogenetic analysis, G. sichuanensis is considered to inherit some primitive traits, but it is more derived than Huayangosaurus, and located in a transitional position between Huayangosaurus and Tuojiangosaurus, as a kind of evolved stegosaurs. The ancestors of Stegosauria are small and quadruped, with primitive ornithopod‐like skull, and grow leaf‐shaped teeth, a large number of bone plates.
Extensive and well-preserved tracksites in the coastally exposed Lower Cretaceous (Valanginian–Barremian) Broome Sandstone of the Dampier Peninsula provide almost the entire fossil record of dinosaurs from the western half of the Australian continent. Tracks near the town of Broome were described in the late 1960s as Megalosauropus broomensis and attributed to a medium-sized theropod trackmaker. Brief reports in the early 1990s suggested the occurrence of at least another nine types of tracks, referable to theropod, sauropod, ornithopod, and thyreophoran trackmakers, at scattered tracksites spread over more than 80 km of coastline north of Broome, potentially representing one of the world's most diverse dinosaurian ichnofaunas. More recently, it has been proposed that this number could be as high as 16 and that the sites are spread over more than 200 km. However, the only substantial research that has been published on these more recent discoveries is a preliminary study of the sauropod tracks and an account of the ways in which the heavy passage of sauropod trackmakers may have shaped the Dampier Peninsula's Early Cretaceous landscape. With the other types of dinosaurian tracks in the Broome Sandstone remaining undescribed, and the full extent and nature of the Dampier Peninsula's dinosaurian tracksites yet to be adequately addressed, the overall scientific significance of the ichnofauna has remained enigmatic.
At the request of the area's Goolarabooloo Traditional Custodians, 400+ hours of ichnological survey work was undertaken from 2011 to 2016 on the 25 km stretch of coastline in the Yanijarri–Lurujarri section of the Dampier Peninsula, inclusive of the coastline at Walmadany (James Price Point). Forty-eight discrete dinosaurian tracksites were identified in this area, and thousands of tracks were examined and measured in situ and using three-dimensional photogrammetry. Tracksites were concentrated in three main areas along the coast: Yanijarri in the north, Walmadany in the middle, and Kardilakan–Jajal Buru in the south. Lithofacies analysis revealed 16 repeated facies types that occurred in three distinctive lithofacies associations, indicative of an environmental transgression between the distal fluvial to deltaic portions of a large braid plain, with migrating sand bodies and periodic sheet floods. The main dinosaurian track-bearing horizons seem to have been generated between periodic sheet floods that blanketed the preexisting sand bodies within the braid plain portion of a tidally influenced delta, with much of the original, gently undulating topography now preserved over large expanses of the present day intertidal reef system. Of the tracks examined, 150 could be identified and are assignable to a least eleven and possibly as many as 21 different track types: five different types of theropod tracks, at least six types of sauropod tracks, four types of ornithopod tracks, and six types of thyreophoran tracks. Eleven of these track types can formally be assigned or compared to existing or new ichnotaxa, whereas the remaining ten represent morphotypes that, although distinct, are currently too poorly represented to confidently assign to existing or new ichnotaxa. Among the ichnotaxa that we have recognized, only two (Megalosauropus broomensis and Wintonopus latomorum) belong to existing ichnotaxa, and two compare to existing ichnotaxa but display a suite of morphological features suggesting that they may be distinct in their own right and are therefore placed in open nomenclature. Six of the ichnotaxa that we have identified are new: one theropod ichnotaxon, Yangtzepus clarkei, ichnosp. nov.; one sauropod ichnotaxon, Oobardjidama foulkesi, ichnogen. et ichnosp. nov.; two ornithopod ichnotaxa, Wintonopus middletonae, ichnosp. nov., and Walmadanyichnus hunteri, ichnogen. et ichnosp. nov.; and two thyreophoran ichnotaxa, Garbina roeorum, ichnogen. et ichnosp. nov., and Luluichnus mueckei, ichnogen. et ichnosp. nov. The level of diversity of the main track types is comparable across areas where tracksites are concentrated: Kardilakan–Jajal Buru (12), Walmadany (11), and Yanijarri (10).
The overall diversity of the dinosaurian ichnofauna of the Broome Sandstone in the Yanijarri–Lurujarri section of the Dampier Peninsula is unparalleled in Australia, and even globally. In addition to being the primary record of non-avian dinosaurs in the western half of Australia, this ichnofauna provides our only detailed glimpse of Australia's dinosaurian fauna during the first half of the Early Cretaceous. It indicates that the general composition of Australia's mid-Cretaceous dinosaurian fauna was already in place by the Valanginian–Barremian. Both sauropods and ornithopods were diverse and abundant, and thyreophorans were the only type of quadrupedal ornithischians. Important aspects of the fauna that are not seen in the Australian mid-Cretaceous body fossil record are the presence of stegosaurians, an overall higher diversity of thyreophorans and theropods, and the presence of large-bodied hadrosauroid-like ornithopods and very large-bodied sauropods. In many respects, these differences suggest a holdover from the Late Jurassic, when the majority of dinosaurian clades had a more cosmopolitan distribution prior to the fragmentation of Pangea. Although the record for the Lower Cretaceous of Gondwana is sparse, a similar mix of taxa occurs in the Barremian–lower Aptian La Amarga Formation of Argentina and the Berriasian–Hauterivian Kirkwood Formation of South Africa. The persistence of this fauna across the Jurassic-Cretaceous boundary in South America, Africa, and Australia might be characteristic of Gondwanan dinosaurian faunas more broadly. It suggests that the extinction event that affected Laurasian dinosaurian faunas across the Jurassic-Cretaceous boundary may not have been as extreme in Gondwana, and this difference may have foreshadowed the onset of Laurasian-Eurogondwanan provincialism. The disappearance of stegosaurians and the apparent drop in diversity of theropods by the mid-Cretaceous suggests that, similar to South America, Australia passed through a period of faunal turnover between the Valanginian and Aptian. -------- In: Society of Vertebrate Paleontology Memoir (Journal of Vertebrate Paleontology Vol. 36, supplement to 6, November 2016).
In basal thyreophorans there is no equivalent to the small based slender dermal tail spines of stegosaurs, which differ in several respects from the lateral dorsal spines of nodosaurid ankylosaurs, and large based stocky spikes are restricted to a few genera of stegosaurs. Several isolated spines and spikes from England (Middle and Upper Jurassic), Portugal (Upper Jurassic) and Spain (Lower Cretaceous), previously re-identified as Thyreophora indet., are Stegosauria indet. Where available, cross-sections shows a thick layer of compact bone with a well-defined central canal as in old adult individuals of Stegosaurus (Upper Jurassic, USA) in which, in addition to display, they functioned as weapons. This stronger construction also favored their preservation as isolated bones. It contrasts with a thin layer of compact bone filled with cancellous bone for the spines of adult and younger individuals of Stegosaurus and of ankylosaurs. The preservation of an isolated pair of spines and of spikes indicates that their bases were bound together. Two columnar femora with a finger-like anterior trochanter from England (Middle and Upper Jurassic) are also re-identified as Stegosauria indet., as are the remains of a juvenile individual from Portugal (Upper Jurassic). The autapomorphies of Lori- catosaurus priscus (Nopcsa, 1911) (England, Middle Jurassic: Middle Callovian) include characters observed in the anterior and mid-caudal vertebrae, posterior pubic process and dermal armor (spine plate, small based body spine).
In 1929, the famous Swedish palaeontologist Carl Wiman documented the first unequivocal stegosaurian dinosaur fossils from Asia. His material comprised an isolated dermal spine, together with a dorsal vertebra that was briefly described but never figured. Since then these remains have languished in obscurity, being noted in some stegosaur review articles but often ignored altogether. However, recent auditing of the Museum of Evolution palaeontological collection at Uppsala University in Sweden has led to the rediscovery of Wiman's original specimens, as well as two additional previously unrecognised stegosaurian dorsal vertebrae. All of these bones derive from the Lower Cretaceous (Berriasian-Valanginian) Mengyin Formation of Shandong Province in eastern China, and are morphologically compatible with the stratigraphically proximal stegosaurian taxon Wuerhosaurus from the Valanginian-Albian Tugulu Group in the Xinjiang Uyghur Autonomous Region of Western China. Wirnan's seminal stegosaurian fossils thus expand current palaeobiogeographical distributions, and contribute to the otherwise enigmatic record of Early Cretaceous stegosaurian occurrences
The plated dinosaur Stegosaurus longispinus came from the Morrison Formation (Upper Jurassic) near Alcova, Wyoming, USA. Only the femur and plaster casts of the posterior pair of long dermal tail spines survived destructive water damage in the 1920s. This surviving material and archival photographs showing the bones in the quarry and as exhibited allow us to expand the original description. S. longispinus Gilmore, 1914 is made the type species of Alcovasaurus n. gen. as A. longispinus (Gilmore, 1914). Autapomorphies include the continuation of transverse processes to the distal caudal vertebrae; distal caudal centra anteroposteriorly short so height exceeds length; both distal dermal spine pairs with a very long slender shaft at ~90% of femoral length, and posterior pair widest at 25% of length. Natronasaurus longispinus was proposed by Ulansky (2014) for S. longispinus. However this failed to meet the requirements of the International Code of Zoological Nomenclature, as is also true for 17 other names proposed for basal thyreophorans and stegosaurs.
Thyreophora es un clado de dinosaurios ornitisquios que reúne a estegosaurios, anquilosaurios y formas basales como Scelidosaurus. Su registro fósil se extiende desde el Jurásico Inferior hasta el Cretácico Superior. Muchos de los fósiles de tireóforos descubiertos hasta la fecha provienen de yacimientos situados en el hemisferio norte. No obstante, el registro gondwánico comprende relevantes restos esqueléti- cos y/o icnitas en Sudamérica, África, Madagascar, Australia, Nueva Zelanda y la Antártida. Los tireóforos podrían estar representados en África desde el Jurásico Inferior–Medio. Se ha documentado su presencia en el Jurásico Superior de Tanzania (estegosaurio Kentrosaurus) y en el lí- mite Jurásico–Cretácico de Bolivia (huellas). Durante el Cretácico Temprano, los estegosaurios estuvieron presentes en Sudáfrica (Paranthodon) y la Argentina (forma indeterminada), y los anquilosaurios en Australia (Minmi). Los anquilosaurios también tienen registro en el Cretácico Superior de Sudamérica (restos esqueléticos en la Argentina y huellas en Bolivia), la Antártida (Antarctopelta), Nueva Zelanda y posiblemente Madagascar. La presencia de anquilosaurios y estegosaurios posibles en el Cretácico Superior de la India está sin confirmar. Desde un punto de vista paleobiogeográfico, los tireóforos gondwánicos parecen provenir de diferentes dispersiones desde Laurasia. Los estegosaurios afri- canos serían el testimonio de dos eventos de dispersión ocurridos durante el Jurásico Medio–Tardío. Los anquilosaurios gondwánicos tampoco resultan de una radiación única: Minmi podría representar un linaje relictual establecido en Australia durante el Jurásico antes de la dicotomía Nodosauridae-Ankylosauridae, mientras que los nodosáuridos de la Argentina y la Antártida serían el resultado de una o varias dispersiones desde América del Norte durante el Cretácico Tardío.
Previous descriptions of the postcranial skeleton of the primitive stegosaur Huayangosaurus taibaii (Middle Jurassic: People's Republic of China) are insufficient for character determinations in cladistic analysis. Reexamination of the postcranium has revealed several important characters, most of which are retained plesiomorphies that have not been identified previously. For example, Huayangosaurus retains ossified tendons, the loss of which has been used as a synapomorphy of Stegosauria. These purported stegosaurian synapomorphies now serve to unite the monophyletic clade Stegosauridae, defined as all stegosaurs more closely related to Stegosaurus than to Huayangosaurus. In addition, some anatomical characters previously used as ‘ankylosauromorph’ synapomorphies have now been identified in Huayangosaurus: this suggests that these characters occur more basally within Thyreophora. The plesiomorphic status of Huayangosaurus suggests that substantial convergence between ankylosaurs and stegosaurs occurred during their respective evolutionary histories, reflecting coincident functional morphological changes associated with the adoption of obligate quadrupedality.
A well preserved dorsal vertebra of a stegosaur is described from the Oxfordian Qigu Formation of the Junggar Basin, northwestern China. This is the first evidence for thyreophoran dinosaurs in this Formation. Previously, stegosaurs have only been recorded from the Lower Cretaceous Tugulu Group of this region. Although the generic identity of the specimen is indeterminate, the find provides confirmation for the presence of stegosaurs in the Jurassic of the Xinjiang Uygur Autonomous Region.
Four articulated posterior dorsal vertebrae from the Middle Jurassic (Callovian) Balabansai Svita at Sarykamyshsai locality
in the northern Fergana Valley represent the first record of Stegosauria in Kyrgyzstan. The vertebrae cannot be attributed
to any known stegosaurian genus. This is one of the oldest records for the Stegosauria.
Vier artikulierte posteriore Dorsalwirbel aus der mitteljurassischen (Callov) Balabansai Svita von der Lokalität Sarykamyshsai
im nördlichen Fergana-Tal stellen den ersten Nachweis von Stegosauria in Kirgistan dar. Die Wirbel lassen sich keiner bekannten
Stegosaurier-Gattung zuordnen. Es handelt sich um einen der ältesten Nachweise der Stegosauria.
The first partial skeleton of a stegosaurian dinosaur was discovered in a brick pit in Swindon, UK in 1874. Since then, numerous
stegosaurian remains have been discovered from Europe, North America, Africa and Asia, and continue to be discovered regularly.
Stegosaurs are known from the Middle Jurassic to the Early Cretaceous; no definitive evidence of the clade is known from younger
deposits. New discoveries are improving our understanding of stegosaur biology and showing that stegosaurs were more morphologically
diverse than was previously realized. A new phylogeny, which includes all valid stegosaurian taxa, largely agrees with previous
studies and shows the European Dacentrurinae was sister taxon to Stegosaurus. Poor resolution at the base of Stegosauria is probably due to the fragmentary nature of many of the Chinese taxa.
KeywordsDinosauria-Ornithischia-Stegosauria-Phylogeny
A new genus of sregosaurid, from the Upper Jurassic Morrison Formation, is more primitive than Stegosaurus stenops but not as primitive as Huayangosaurus. The specimen consists of a nearly complete skull and much of the skeleton, minus the forearms and hind legs. It is «, characterized by a short, broad skull; domed frontoparietal; low neural "-arches; and low, oval plates. A preliminary phyletic analysis of the Stegosauria places this new genus closest to Dacentrurus from the Upper Jurassic of Europe. The occurrence of this new stegosaurus 5 m above the base of the Morrison Formation makes it one of the oldest known stegosaurs in North America.
Stegosauria is recognized as a Jurassic clade of Ornithischia. Stegosaurs are medium-sized to large quadrupedal herbivores with proportionally small heads, short and massive forelimbs, long columnar hindlimbs, short metacarpals and metatarsals with hoof-like unguals. The largest stegosaur is Stegosaurus (up to 9 m) and is represented by numerous remains from the late Kimmeridgian or Tithonian of the United States, mostly from Colorado, Utah, and Wyoming. Stegosaurs are also characterized by parasagittal osteoderms, which developed as a double series of small plates and spines. The best known example of this configuration is Kentrosaurus, presumed to have carried fifteen paired plates and spines on its back, but only the position of the terminal pair of tail spines is fixed. The pattern of plates and spines is characteristic for each species, and it was probably important for intraspecific recognition.
New materials of Lesothosaurus diagnosticus permit a detailed understanding of one of the earliest and most primitive ornithischians. Skull proportions and suturai relations can be discerned from several articulated and disarticulated skulls. The snout is proportionately long with a vascularized, horn-covered tip. The premaxillary palate is broad and vomers are long and fused anteriorly. Unlike many later ornithischians, the postpalatine vacuities are broadly open. The basal tubera are short and gently depressed, and the epiotic contributes to the sidewall of the braincase. The mandibular symphysis is spout-shaped, and the dentition is marked by oblique wear facets, in contrast to earlier reports. The tooth-to-tooth wear facets and form of the predentary-dentary articulation suggest long-axis rotation of the mandibular rami during mastication.The forelimb is proportionately very short, with a partially opposable pollex. The ischium lacks an obturator process. The reduced hallux is held well above the substrate during locomotion.L. diagnosticus is diagnosed below on the basis of apomorphic features. Other “fabrosaurids” constitute a heterogeneous assemblage of poorly known ornithischians and hatchling prosauropods that do not share any apomorphic features with L. diagnosticus. Fabrosaurus australis is a nomen dubium, and, as a consequence, the family Fabrosauridae is invalid. Echinodon becklesii may represent a primitive heterodontosaur, and Tawasaurus, Fulengia, and portions of the holotype of Technosaurus represent hatchling prosauropods. Pisanosaurus mertii may be the most primitive ornithischian, as indicated by the form of the distal crus and astragalus, but a more precise phylogenetic assessment will require additional remains.
All specimens of the Stegosauridae from England are described. The material from the lower and upper Bathonian (Middle Jurassic) of Oxfordshire and Gloucestershire is the earliest record of the family. The holotype femur of Omosaurus vetustus Huene is tentatively referred to the genus Lexovisaurus Hoffstetter as L.? vetustus (Huene). Lexovisaurus durobrivensis (Hulke) includes Omosaurus durobrivensis Hulke, O. leedsi Seeley, and Stegosaurus priscus Nopcsa; it is represented by two partial skeletons and isolated bones from the Lower Oxford Clay (middle Callovian, Middle Jurassic) of Northamptonshire and Cambridgeshire. The dermal armor of Lexovisaurus consisted of large, thin plates with the height more than twice the anteroposterior width, in addition to at least one pair of parasacral spines. The holotype femur of Omosaurus phillipsi Seeley (Oxfordian, Upper Jurassic, Yorkshire) is from a juvenile individual and is generically and specifically indeterminate. Dacentrurus armatus (Owen) includes Omosaurus hastiger Owen and ?O. lennieri Nopcsa; it is represented by a partial skeleton and isolated bones from the lower Kimmeridge Clay (Kimmeridgian, Upper Jurassic) of Wiltshire and Dorsetshire. In Dacentrurus, the vertebral centra are massive, the solid pedicel-like region of the dorsal neural arches is short, and the minimum angle between the transverse process and the neural arch is 55°. The armor consists of at least small plates plus elongate and massive tail spines. Craterosaurus pottonensis Seeley consists of a partial neural arch of a dorsal vertebra from the Neo-comian (Lower Cretaceous) of Bedfordshire. This taxon is characterized by a very deep depression in the top of the arch posterior to the prezygapophyses. The relationships of Dacentrurus and Lexovisaurus are discussed, but the record is too poor to reconstruct any meaningful phylogenetic relationships.
Two partial skeletons of juvenile individuals of Stegosaurus with estimated body lengths of about 1.5 m (5 ft) and 2.6 m (8.5 ft) are described from the Morrison Formation (Upper Jurassic) of Utah and Wyoming. These juveniles differ from adults in the absence of fusion in composite bones (sacrum, scapulocoracoid, tibia–fibula–astragalus–calcaneum), the smoothness of the surface of the bones, the smaller size of ridges for muscular attachment, a proportionally more slender and elongate scapula, the relatively small size of the olecranon process of the ulna and the head of the femur, and the possible absence of dermal plates (but tail spines were present). Apart from the ratios of the length of the femur to those of the humerus and ilium, and the form of the scapula, ilium and fibula, the bones of juvenile individuals of Stegosaurus are very similar to those of juvenile individuals of the stegosaur Kentrosaurus (Upper Jurassic, East Africa). A probable sexual dimorphism in the sacrum with either four (?female) or five (?male) sacral ribs occurs in Kentrosaurus. The additional sacral rib attaches anterior to the other four; a rib in the Utah juvenile has the same distinctive shape, and it thus may have been a male (sacra of Stegosaurus with four sacral ribs have been previously illustrated).
Here, we provide a comparative survey of the histology of postcranial dermal-armor osteoderms of ankylosaurs, including material of polacanthids (Polacanthus foxii, Gastonia sp.), ankylosaurids (e.g., Saichania chulsanensis, Pinacosaurus grangeri, Ankylosauridae indet.), and nodosaurids (e.g., Struthiosaurus austriacus, Nodosauridae indet.). Samples of osteoderm-bearing outgroups (Scelidosaurus harrisonii, phytosaurs, and crocodiles) as well as literature data on Stegosaurus stenops plates and spikes helped to elucidate histological evolution and character polarity.The complex histology of ankylosaur osteoderms seems to be of systematic value, as the sectioned osteoderms can be classified into three distinctive groups. All polacanthid osteoderms share a relatively generalized histology with a thickened, uniform cortex completely surrounding trabecular bone. Nodosaurid osteoderms only have an external cortex with the underlying internal spongiosa being much thicker and forming a rather flat base. Ankylosaurids have very thin osteoderms that were greatly strengthened by the incorporation of structural collagen fiber bundles, similar but not identical to Sharpey's fibers, into the thin primary cortex and, uniquely, the secondary bone tissue. Structural fibers are also abundant in nodosaurids but there are significant differences in arrangement and occurrence, being random in ankylosaurids but highly ordered in nodosaurids. In their cortex, the latter have two sets of 3D-orthogonal fibers rotated at 45° to each other. The combination of the greatly strengthened external cortex covering a thick cushion of cancellous bone thus serves to resist local penetration. Ankylosaurid and nodosaurid osteoderms are thus highly optimized towards a resistant yet light-weight armor.
This chapter summarizes all dinosaur locations currently known worldwide. Geographic location is based on primary administrative divisions (e.g., states, departments, provinces, counties) of the countries in which dinosaur material has been found. Locations are annotated for lithostratigraphic unit (bed, formation, group, series), faunal composition, and stratigraphic horizon. The members of the fauna are present in rank order, roughly based on their phylogenetic relationships. The chapter also includes locations yielding skeletal remains and those that have produced tracks and/or trackways, as well as locations where eggs and eggshell fragments have been found.
The ascendancy of dinosaurs on land near the close of the Triassic now appears to have been as accidental and opportunistic as their demise and replacement by therian mammals at the end of the Cretaceous. The dinosaurian radiation, launched by 1-meter-long bipeds, was slower in tempo and more restricted in adaptive scope than that of therian mammals. A notable exception was the evolution of birds from small-bodied predatory dinosaurs, which involved a dramatic decrease in body size. Recurring phylogenetic trends among dinosaurs include, to the contrary, increase in body size. There is no evidence for co-evolution between predators and prey or between herbivores and flowering plants. As the major land masses drifted apart, dinosaurian biogeography was molded more by regional extinction and intercontinental dispersal than by the breakup sequence of Pangaea.
The recent discovery of the Middle Jurassic stegosaur, Huayangosaurus taibaii has shed new light on the early phylogeny of Stegosauria. The skull of this taxon is described in detail and compared to those of other thyreophorans. Cranial and postcranial autapomorphies of Huayangosaurus include high premaxillary and maxillary tooth counts (7 and 25–30, respectively), small postorbital horn, intercostal articular flanges, and a carpus composed of a single coossified block.Nineteen synapomorphies unite Huayangosaurus and other stegosaurs and constitute a revised cladistic diagnosis for Stegosauria. Huayangosaurus is the sister-taxon to all other stegosaurs, which have lost premaxillary teeth, reduced the size of the antorbital fossa, increased the length of the prepubic process of the pubis, and lost lateral scute rows along the trunk.
The evolution of scutes in thyreophoran dinosaurs, based on Scutellosaurus, Scelidosaurus, Stegosaurus, and several ankylosaurs, began with small rounded or ovoid structures that typically had slight, anteroposteriorly oriented keels. These scutes were elaborated in two general and overlapping ways: they could flare laterally and asymmetrically beneath the keels that mark the anteroposterior axis, and they could be hypertrophied in their distal growth to produce plates, spikes, and other kinds of ornamentation. Stegosaurus plates and spikes are thus primarily hypertrophied keels of primitive thyreophoran scutes, sometimes with elaboration of dermal bone around their pustulate bases. Histologically, most thyreophoran scute tissues comprise secondary trabecular medullary bone that is sandwiched between layers of compact primary bone. Some scutes partly or mostly comprise anatomically metaplastic bone, that is, ossified fibrous tissue that shows incremental growth. The "plumbing" of Stegosaurus plates was not apparently built to support a "radiator system of internal blood vessels that communicated with the outside of the plates and coursed along their external surfaces to return heated or cooled blood to the body core. Possibly a purely external system supported this function but there is no independent evidence for it. On the other hand, many of the vascular features in stegosaurian plates and spikes reflect bautechnisches artifacts of growth and production of bone. Surface vascular features likely supported bone growth and remodeling, as well as the blood supply to a keratinous covering. When the gross and microstructural features of the plates and spikes are viewed in phylogenetic context, no clear pattern of thermoregulatory function emerges, though an accessory role cannot be eliminated in certain individual species. It seems more likely, as in other groups of dinosaurs, that the variation of dermal armor form in stegosaurs was primarily linked to species individuation and recognition, perhaps secondarily to interand intraspecific display, and rarely to facultative thermoregulation.
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