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[[File:Xingxiulong-3.jpg|thumb|left|Detalle del cráneo y mandíbula de ''Xingxiulong''.]] |
[[File:Xingxiulong-3.jpg|thumb|left|Detalle del cráneo y mandíbula de ''Xingxiulong''.]] |
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A diferencia del contemporáneo ''[[Lufengosaurus]]'', ''Xingxiulong'' no tiene una cresta en los lados de su [[maxilar]]. Se preservaron once alvéolos dentales a lo largo del maxilar. Más atrás, en frente de la órbita ocular, el [[hueso lacrimal]] tiene una proyección notoria cerca de la parte superior de su extremo frontal, la cual también es observada en ''Lufengosaurus'', ''[[Adeopapposaurus]]'', ''[[Massospondylus]]'' y ''[[Riojasaurus]]'', pero no en ''[[Yunnanosaurus]]'', ''[[Jingshanosaurus]]'', o los sauropodiformes más avanzados. La superficie de contacto entre el [[yugal]] y el [[postorbital]] es bastante alargada, como en ''Lufengosaurus'' pero no en ''Yunnanosaurus''. Entre las tres ramas del yugal, aquella dirigida hacia atrás forma un ángulo de 80° con respecto a la rama que se proyecta hacia arriba, lo cual es similar a ''[[Plateosaurus]]'' y ''[[Thecodontosaurus]]'' pero es mucho mayor que en otros [[sauropodomorpha|sauropodomorfos]].<ref name="desc"/> |
A diferencia del contemporáneo ''[[Lufengosaurus]]'', ''Xingxiulong'' no tiene una cresta en los lados de su [[maxilar]]. Se preservaron once alvéolos dentales a lo largo del maxilar. Más atrás, en frente de la órbita ocular, el [[hueso lacrimal]] tiene una proyección notoria cerca de la parte superior de su extremo frontal, la cual también es observada en ''Lufengosaurus'', ''[[Adeopapposaurus]]'', ''[[Massospondylus]]'' y ''[[Riojasaurus]]'', pero no en ''[[Yunnanosaurus]]'', ''[[Jingshanosaurus]]'', o los sauropodiformes más avanzados. La superficie de contacto entre el [[yugal]] y el [[postorbital]] es bastante alargada, como en ''Lufengosaurus'' pero no en ''Yunnanosaurus''. Entre las tres ramas del yugal, aquella dirigida hacia atrás forma un ángulo de 80° con respecto a la rama que se proyecta hacia arriba, lo cual es similar a ''[[Plateosaurus]]'' y ''[[Thecodontosaurus]]'' pero es mucho mayor que en otros [[sauropodomorpha|sauropodomorfos]].<ref name="desc"/> |
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At the base of the skull, the [[quadratojugal bone|quadratojugal]] bears two branches, one pointing forwards and one upwards; they are roughly perpendicular to each other, unlike ''Lufengosaurus'' (angle of 45°), ''Yunnanosaurus'' (angle of 60°), and ''Jingshanosaurus'' (angle of 110°). Above the quadratojugal, the [[quadrate bone|quadrate]] has two [[condyle (anatomy)|articulating condyles]], a subtriangular one facing outward and a more rounded one facing inwards; the latter condyle is placed closer to the bottom, like ''Lufengosaurus'' and ''Yunnanosaurus'' but not ''Plateosaurus''. At the back of the skull, between the [[parietal bone|parietals]] and [[occipital bone|supraoccipitals]], there is a prominently developed postparietal fenestra; the supraoccipital itself slopes forwards at its bottom end so as to round off the base of the skull. The basipterygoid processes are long, slender, and project downwards and outwards like ''Plateosaurus'' and unlike ''Lufengosaurus'' and ''Jingshanosaurus'', forming an angle of 80° with each other.<ref name="desc"/> |
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En la base del cráneo, el [[cuadratoyugal]] tiene dos ramos, uno apuntando hacia adelante y otro hacia arriba; estos son aproximadamente perpendiculares entre sí, a diferencia de ''Lufengosaurus'' (con ángulo de 45°), ''Yunnanosaurus'' (ángulo de 60°) y ''Jingshanosaurus'' (ángulo de 110°). Encima del cuadratoyugal, el [[hueso cuadrado]] tiene dos [[cóndilo|cóndilos articulares]], con uno subtriangular y orientado hacia afuera y uno más redondeado orientado hacia adentro; este último cóndilo se sitúa más cerca de la parte inferior, como en ''Lufengosaurus'' y ''Yunnanosaurus'' pero no en ''Plateosaurus''. En la parte posterior del cráneo, entre los [[hueso parietal|parietales]] y los [[hueso occipital|supraoccipitales]], hay una fenestra postparietal desarrollada de forma prominente; el propio supraoccipital desciende hacia adelante en su extremo inferior hasta rematar la base del cráneo. Los procesos del basipterigoides son largos, delgados y se proyectan hacia abajo y hacia afuera como en ''Plateosaurus'' pero a diferencia de ''Lufengosaurus'' y ''Jingshanosaurus'', formando un ángulo de 80° entre sí.<ref name="desc"/> |
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Compared to ''Lufengosaurus'', ''Yunnanosaurus'', and ''Jingshanosaurus'', the [[angular bone|angular]] and [[surangular]] extend much further in front of the mandibular fenestra in ''Xingxiulong'', which is closer to ''Adeopapposaurus'' and ''Plateosaurus''. The articular bears an inward-projecting and pyramidal process as an extension of the jaw joint; at its back end, it also possesses an upward-directed and tab-like process, which is also seen in ''[[Coloradisaurus]]'', ''Jingshanosaurus'', and an as-of-yet unnamed sauropodomorph.<ref name="desc"/> |
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Comparado con ''Lufengosaurus'', ''Yunnanosaurus'' y ''Jingshanosaurus'', en ''Xingxiulong'' los huesos angular y surangular se extienden mucho más en el frente de la fenestra mandibular, en lo que se parece más a ''Adeopapposaurus'' y a ''Plateosaurus''.<ref name="plateo">{{cite journal | last1 = Prieto-Marquez | first1 = A. | last2 = Norell | first2 = M. | title = Redescription of a nearly complete skull of ''Plateosaurus'' (Dinosauria, Sauropodomorpha) from the late Triassic of Trossingen (Germany) | journal = American Museum Novitates | volume = 3727 | date = 2011 | pages = 1-58 | url = http://digitallibrary.amnh.org/handle/2246/6138}}</ref> El articular posee un proceso piramidal proyectado hacia adentro como extensión de la articulación de la mandíbula; en su extremo posterior, también posee un proceso dirigido hacia arriba en forma de pestaña, lo cual también es visto en ''[[Coloradisaurus]]'',<ref name="coloradi">{{cite journal | last1 = Apaldetti | first1 = C. | last2 = Martinez | first2 = R.N. | last3 = Pol | first3 = D. | last4 = Souter | first4 = T. | title = Redescription of the Skull of ''Coloradisaurus brevis'' (Dinosauria, Sauropodomorpha) from the Late Triassic Los Colorados Formation of the Ischigualasto-Villa Union Basin, northwestern Argentina | journal = Journal of Vertebrate Paleontology | volume = 34 | issue = 5 | date = 2014 | pages = 1113-1132 | doi = 10.1080/02724634.2014.859147 | url = http://www.tandfonline.com/doi/abs/10.1080/02724634.2014.859147}}</ref> ''Jingshanosaurus'' y en un sauropodomorfo sin nombrar.<ref name="desc"/> |
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===Vertebrae=== |
===Vertebrae=== |
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There are ten [[cervical vertebrae]] in the neck of ''Xingxiulong''. The proatlas, an atrophied vertebra positioned in front of the [[atlas (anatomy)|atlas]], is bounded in front by top sides of the [[foramen magnum]]. While it is difficult to say much about the atlas itself due to damage, the immediately following [[axis (anatomy)|axis]] has a relatively short [[vertebra#structure|centrum]], which is slightly compressed on its sides and bottom. Overall, the remainder of the cervical vertebrae are relatively short, being only 2.5 to 3 times as long as they are tall; they become increasingly shorter towards the back of the neck, like ''Lufengosaurus''. Other basal sauropodomorphs, including ''Jingshanosaurus'', have cervical vertebrae that are generally 3 to 4 times as long as they are tall. On the bottom of the centra of cervical vertebrae 4-9, there is a prominent keel as in ''Lufengosaurus'', ''Jingshanosaurus'', and other basal sauropodomorphs. Near the back of the neck, the [[vertebra#structure|neural spines]] become somewhat table-like.<ref name="desc"/> |
There are ten [[cervical vertebrae]] in the neck of ''Xingxiulong''. The proatlas, an atrophied vertebra positioned in front of the [[atlas (anatomy)|atlas]], is bounded in front by top sides of the [[foramen magnum]]. While it is difficult to say much about the atlas itself due to damage, the immediately following [[axis (anatomy)|axis]] has a relatively short [[vertebra#structure|centrum]], which is slightly compressed on its sides and bottom. Overall, the remainder of the cervical vertebrae are relatively short, being only 2.5 to 3 times as long as they are tall; they become increasingly shorter towards the back of the neck, like ''Lufengosaurus''. Other basal sauropodomorphs,<ref name="adeopappo">{{cite journal | last1 = Martinez | first1 = R.N. | title = ''Adeopapposaurus mognai'', gen. et sp. nov. (Dinosauria: Sauropodomorpha), with comments on adaptations of basal Sauropodomorpha | journal = Journal of Vertebrate Paleontology | volume = 29 | issue = 1 | date = 2009 | pages = 142-164 | doi = 10.1671/039.029.0102 | url = http://www.tandfonline.com/doi/abs/10.1671/039.029.0102}}</ref><ref name="leye">{{cite journal | last1 = Apaldetti | first1 = C. | last2 = Martinez | first2 = R.N. | last3 = Alcober | first3 = O.A. | last4 = Pol | first4 = D. | title = A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina | journal = PLoS ONE | date = 2011 | volume = 6 | issue = 11 | page = e26964 | doi = 10.1371/journal.pone.0026964 | url = http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0026964}}</ref> including ''Jingshanosaurus'', have cervical vertebrae that are generally 3 to 4 times as long as they are tall. On the bottom of the centra of cervical vertebrae 4-9, there is a prominent keel as in ''Lufengosaurus'', ''Jingshanosaurus'', and other basal sauropodomorphs. Near the back of the neck, the [[vertebra#structure|neural spines]] become somewhat table-like.<ref name="desc"/> |
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The fourteen [[thoracic vertebrae|dorsal vertebrae]] are weakly [[vertebral column#variations in vertebrae|amphicoelous]], or concave on both ends, typical of basal sauropodomorphs. Also typical is the presence of blade-like keels on the undersides of the first to third dorsal vertebrae, which are not seen elsewhere; additionally, the dorsal vertebrae near the front have the typical low, short, and somewhat plate-like neural spines. Unusually, however, the same kinds of neural spines are also seen in the last three dorsal vertebrae, which is only otherwise seen in basal [[saurischia]]ns like ''[[Herrerasaurus]]'' and ''[[Eoraptor]]''. In the middle and back dorsal vertebrae, the top back corner of the neural spines project outward to produce a concave back edge, which is seen in some other basal sauropodomorphs but not ''Lufengosaurus'', ''Jingshanosaurus'', ''Yunnanosaurus'', and ''[[Riojasaurus]]''.<ref name="desc"/> |
The fourteen [[thoracic vertebrae|dorsal vertebrae]] are weakly [[vertebral column#variations in vertebrae|amphicoelous]], or concave on both ends, typical of basal sauropodomorphs. Also typical is the presence of blade-like keels on the undersides of the first to third dorsal vertebrae, which are not seen elsewhere; additionally, the dorsal vertebrae near the front have the typical low, short, and somewhat plate-like neural spines. Unusually, however, the same kinds of neural spines are also seen in the last three dorsal vertebrae, which is only otherwise seen in basal [[saurischia]]ns like ''[[Herrerasaurus]]'' and ''[[Eoraptor]]''. In the middle and back dorsal vertebrae, the top back corner of the neural spines project outward to produce a concave back edge, which is seen in some other basal sauropodomorphs but not ''Lufengosaurus'', ''Jingshanosaurus'', ''Yunnanosaurus'', and ''[[Riojasaurus]]''.<ref name="desc"/> |
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[[File:Xingxiulong_vertebrae.jpg|thumb|Sacral vertebrae (a-d) and pubis (e-h) of ''Xingxiulong'']] |
[[File:Xingxiulong_vertebrae.jpg|thumb|Sacral vertebrae (a-d) and pubis (e-h) of ''Xingxiulong'']] |
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Unusually among basal sauropodomorphs, ''Xingxiulong'' has four [[sacrum|sacral vertebrae]]. This is a trait typically seen in more derived sauropodomorphs, like ''[[Melanorosaurus]]'', ''[[Leonerasaurus]]'', ''[[Barapasaurus]]'', and ''[[Shunosaurus]]''. The first of these sacral vertebrae, the dorsosacral, is not very well-fused to the next sacral vertebra; neither is it entirely fused to the corresponding sacral rib on the [[vertebra#structure|transverse processes]]. Collectively, the dorsosacral and first pair of sacral ribs extend forward to contact the [[ilium (bone)|ilium]]. The second and third sacral vertebrae, the two primoridial sacrals, are about the same length, and are well-fused to each other. Like other basal sauropodomorphs, the transverse processes of the third sacral vertebra project backwards and outwards. The same is true of the transverse process and sacral ribs for the fourth sacral vertebra, which contact the ilium again at the back. All of the neural spines are plate-like, like the last few dorsal vertebrae.<ref name="desc"/> |
Unusually among basal sauropodomorphs, ''Xingxiulong'' has four [[sacrum|sacral vertebrae]]. This is a trait typically seen in more derived sauropodomorphs, like ''[[Melanorosaurus]]'', ''[[Leonerasaurus]]'',<ref name="leonera">{{cite journal | last1 = Pol | first1 = D. | last2 = Garrido | first2 = A. | last3 = Cerda | first3 = I.A. | title = A New Sauropodomorph Dinosaur from the Early Jurassic of Patagonia and the Origin and Evolution of the Sauropod-type Sacrum | journal = PLoS ONE | date = 2011 | volume = 6 | issue = 1 | page = e14572 | doi = 10.1371/journal.pone.0014572 | url = http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014572}}</ref> ''[[Barapasaurus]]'',<ref name="barapa">{{cite journal | last1 = Jain | first1 = S.L. | last2 = Kutty | first2 = T.S. | last3 = Roy-Chowdhury | first3 = T. | last4 = Chatterjee | first4 = S. | title = The Sauropod Dinosaur from the Lower Jurassic Kota Formation of India | journal = Proceedings of the Royal Society B | volume = 188 | issue = 1091 | date = 1975 | doi = 10.1098/rspb.1975.0014 | url = http://rspb.royalsocietypublishing.org/content/188/1091/221 | pages = 221-228}}</ref> and ''[[Shunosaurus]]''. The first of these sacral vertebrae, the dorsosacral, is not very well-fused to the next sacral vertebra; neither is it entirely fused to the corresponding sacral rib on the [[vertebra#structure|transverse processes]]. Collectively, the dorsosacral and first pair of sacral ribs extend forward to contact the [[ilium (bone)|ilium]]. The second and third sacral vertebrae, the two primoridial sacrals, are about the same length, and are well-fused to each other. Like other basal sauropodomorphs, the transverse processes of the third sacral vertebra project backwards and outwards. The same is true of the transverse process and sacral ribs for the fourth sacral vertebra, which contact the ilium again at the back. All of the neural spines are plate-like, like the last few dorsal vertebrae.<ref name="desc"/> |
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It is probable that ''Xingxiulong'' would have had more than the 35 preserved caudal vertebrae in the tail. These vertebrae are overall tall and very robust, and have concave sides like other basal sauropodomorphs. They also all appear to be amphicoelous. The transverse processes of the first several caudal vertebrae are wide and flat, and directed upwards and outwards; the transverse processes of caudal vertebrae further back in the tail are more slender and horizontal. As for the neural spines, they are tall and thin, and are directed somewhat backwards.<ref name="desc"/> |
It is probable that ''Xingxiulong'' would have had more than the 35 preserved caudal vertebrae in the tail. These vertebrae are overall tall and very robust, and have concave sides like other basal sauropodomorphs. They also all appear to be amphicoelous. The transverse processes of the first several caudal vertebrae are wide and flat, and directed upwards and outwards; the transverse processes of caudal vertebrae further back in the tail are more slender and horizontal. As for the neural spines, they are tall and thin, and are directed somewhat backwards.<ref name="desc"/> |
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===Limbs=== |
===Limbs=== |
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Both ends of the [[scapula]] of ''Xingxiulong'' are quite expanded; the bottom end's width is 56% the length of the scapula, and the top end's width is 49% the length of the scapula. Various other basal sauropodomorphs, including ''Lufengosaurus'' and ''Jingshanosaurus'', have a more expanded bottom end, but their scapulae are generally more slender; conversely, ''[[Antetonitrus]]'' and ''[[Lessemsaurus]]'' have similarly robust scapulae, but the top end is more expanded in these two taxa. As with ''Jingshanosaurus'', the maximum width of the robust shaft of the scapula is 19-20% the length of the overall bone; ''Antetonitrus'' and ''Lessemsaurus'' have even more robust shafts, while the majority of basal sauropodomorphs have narrower shafts.<ref name="desc"/> |
Both ends of the [[scapula]] of ''Xingxiulong'' are quite expanded; the bottom end's width is 56% the length of the scapula, and the top end's width is 49% the length of the scapula. Various other basal sauropodomorphs, including ''Lufengosaurus'' and ''Jingshanosaurus'', have a more expanded bottom end, but their scapulae are generally more slender; conversely, ''[[Antetonitrus]]'' <ref name="anteto">{{cite journal | last1 = McPhee | first1 = B.W. | last2 = Yates | first2 = A.M. | last3 = Choiniere | first3 = J.N. | last4 = Abdala | first4 = F. | title = The complete anatomy and phylogenetic relationships of ''Antetonitrus ingenipes'' (Sauropodiformes, Dinosauria): implications for the origins of Sauropoda | journal = Zoological Journal of the Linnaean Society | volume = 171 | issue = 1 | pages = 151-205 | date = 2014 | doi = 10.1111/zoj.12127 | url = http://onlinelibrary.wiley.com/doi/10.1111/zoj.12127/abstract}}</ref> and ''[[Lessemsaurus]]'' have similarly robust scapulae, but the top end is more expanded in these two taxa. As with ''Jingshanosaurus'', the maximum width of the robust shaft of the scapula is 19-20% the length of the overall bone; ''Antetonitrus''<ref name="anteto"/> and ''Lessemsaurus'' have even more robust shafts, while the majority of basal sauropodomorphs have narrower shafts.<ref name="desc"/> |
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The tuberosity on the inner surface of the top end of the [[humerus]] is rather poorly-developed in ''Xingxiulong'', in contrast to the majority of basal sauropodomorphs (including ''Lufengosaurus'' and ''Yunnanosaurus''). Like ''Yunnanosaurus'' and ''Jingshanosaurus'', the [[ulna]] is about 61% the length of the humerus; this ratio is 68% in ''Lufengosaurus'', resulting in a longer ulna. The top end of the ulna is quite expanded, with prominent anteromedial and anterolateral processes; these processes, along with the shallow radial fossa, collectively form the articulation of the ulna with the [[radius (bone)|radius]]. The latter bone is slender and about 54% the length of the humerus. Parts of the hand, which bore at least four digits, are known but not well-described.<ref name="desc"/> |
The tuberosity on the inner surface of the top end of the [[humerus]] is rather poorly-developed in ''Xingxiulong'', in contrast to the majority of basal sauropodomorphs (including ''Lufengosaurus'' and ''Yunnanosaurus''). Like ''Yunnanosaurus'' and ''Jingshanosaurus'', the [[ulna]] is about 61% the length of the humerus; this ratio is 68% in ''Lufengosaurus'', resulting in a longer ulna. The top end of the ulna is quite expanded, with prominent anteromedial and anterolateral processes; these processes, along with the shallow radial fossa, collectively form the articulation of the ulna with the [[radius (bone)|radius]]. The latter bone is slender and about 54% the length of the humerus. Parts of the hand, which bore at least four digits, are known but not well-described.<ref name="desc"/> |
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Overall, the [[ilium (bone)|ilium]] is similar to other basal sauropodomorphs. The front of the ilium does not exceed the level of the pubic peduncle, or its articulation with the [[pubis (bone)|pubis]]. Unlike other basal sauropodomorphs, the back end is somewhat square instead of being pointed, and the bottom portion is very concave when viewed from the side (in other basal sauropodomorphs, it is mostly straight or even convex). The ischial peduncle, or the portion that articulates with the [[ischium]], has a small projecting heel on its bottom end. As for the pubis itself, the top end (known as the pubic plate) is relatively long, at 40% of the length of the bone, and the bottom portion (known as the pubic apron) is conversely relatively short. This is unlike other basal sauropodomorphs but similar to some basal sauropods. The outer face of the pubic apron is somewhat concave, and the bottom end is expanded forwards and backwards to about 16% the length of the entire bone. Finally, the expanded obturator plate of the ischium bears a groove on its side.<ref name="desc"/> |
Overall, the [[ilium (bone)|ilium]] is similar to other basal sauropodomorphs. The front of the ilium does not exceed the level of the pubic peduncle, or its articulation with the [[pubis (bone)|pubis]]. Unlike other basal sauropodomorphs, the back end is somewhat square instead of being pointed, and the bottom portion is very concave when viewed from the side (in other basal sauropodomorphs, it is mostly straight or even convex). The ischial peduncle, or the portion that articulates with the [[ischium]], has a small projecting heel on its bottom end. As for the pubis itself, the top end (known as the pubic plate) is relatively long, at 40% of the length of the bone, and the bottom portion (known as the pubic apron) is conversely relatively short. This is unlike other basal sauropodomorphs but similar to some basal sauropods. The outer face of the pubic apron is somewhat concave, and the bottom end is expanded forwards and backwards to about 16% the length of the entire bone. Finally, the expanded obturator plate of the ischium bears a groove on its side.<ref name="desc"/> |
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On the [[femur]], the [[lesser trochanter]] extends below the level of the [[femoral head]], unlike ''Yunnanosaurus'' and ''Jingshanosaurus''. Viewed from the front, the trochanter is close to the midline of the bone, like other basal sauropodomorphs except for ''Antetonitrus'' and ''[[Melanorosaurus]]'' (in which it is closer to the outer edge). Similarly, the [[fourth trochanter]] is near the midline, in contrast to many basal sauropodomorphs, including ''Lufengosaurus''. Of the two processes on the bottom of the [[tibia]], the one in the back is thinner, and projects more outwards than downwards than the one in front; this differs from most other sauropodomorphs in which the two are equally thick, and either they project equally outwards (as in ''Lufengosaurus'' and ''Jingshanosaurus'') or the front one projects further outwards (as in ''Yunnanosaurus'').<ref name="desc"/> |
On the [[femur]], the [[lesser trochanter]] extends below the level of the [[femoral head]], unlike ''Yunnanosaurus'' and ''Jingshanosaurus''. Viewed from the front, the trochanter is close to the midline of the bone, like other basal sauropodomorphs except for ''Antetonitrus'' and ''[[Melanorosaurus]]'' (in which it is closer to the outer edge). Similarly, the [[fourth trochanter]] is near the midline, in contrast to many basal sauropodomorphs,<ref name="coloradi"/> including ''Lufengosaurus''. Of the two processes on the bottom of the [[tibia]], the one in the back is thinner, and projects more outwards than downwards than the one in front; this differs from most other sauropodomorphs in which the two are equally thick, and either they project equally outwards (as in ''Lufengosaurus'' and ''Jingshanosaurus'') or the front one projects further outwards (as in ''Yunnanosaurus'').<ref name="desc"/> |
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The back of the [[talus bone|astragalus]] bears a bulge close to the bottom end of the bone. A similar bulge is also seen in ''[[Mussaurus]]'', albeit better developed and placed closer to the midline. Out of the [[metatarsal bones|metatarsals]], the first one is the widest and most robust. The fifth metatarsal is unusually expanded at its top end, the width of which is 85% the length of the entire bone. In other sauropodomorphs, this figure is usually 50-77%, although ''Antetonitrus'' may have a similarly expanded metatarsal. Below the metatarsals, the five digits have a [[phalanges|phalangeal formula]] of 2-3-4-5-1.<ref name="desc"/> |
The back of the [[talus bone|astragalus]] bears a bulge close to the bottom end of the bone. A similar bulge is also seen in ''[[Mussaurus]]'',<ref name="mus"/> albeit better developed and placed closer to the midline. Out of the [[metatarsal bones|metatarsals]], the first one is the widest and most robust. The fifth metatarsal is unusually expanded at its top end, the width of which is 85% the length of the entire bone. In other sauropodomorphs, this figure is usually 50-77%,<ref name="eucnemo">{{cite journal | last1 = McPhee | first1 = B.W. | last2 = Choiniere | first2 = J.N. | last3 = Yates | first3 = A.M. | last4 = Viglietti | first4 = P.A. | title = A second species of ''Eucnemesaurus'' Van Hoepen, 1920 (Dinosauria, Sauropodomorpha): new information on the diversity and evolution of the sauropodomorph fauna of South Africa's lower Elliot Formation (latest Triassic) | journal = Journal of Vertebrate Paleontology | volume = 35 | date = 2015 | issue = 5 | page = e980504 | doi = 10.1080/02724634.2015.980504 | url = http://www.tandfonline.com/doi/abs/10.1080/02724634.2015.980504?journalCode=ujvp20}}</ref> although ''Antetonitrus'' may have a similarly expanded metatarsal. Below the metatarsals, the five digits have a [[phalanges|phalangeal formula]] of 2-3-4-5-1.<ref name="desc"/> |
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==Discovery and naming== |
==Discovery and naming== |
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==Classification== |
==Classification== |
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A 2017 [[phylogenetics|phylogenetic analysis]] conducted based on the dataset of McPhee ''et al.'', published in 2015 with the description of ''[[Pulanesaura]]'', found that ''Xingxiulong'' was a basal member of the group [[Massopoda|Sauropodiformes]] once ''[[Blikanasaurus]]'' was removed from the dataset. Within this group, it is closest to the contemporary ''[[Jingshanosaurus]]''. Traits that are shared by ''Xingxiulong'' and ''Jingshanosaurus'' include the [[infratemporal fenestra]] being placed entirely behind the eye socket; the [[scapula]] being at least 20% as wide as it is long; the pubic apron, or the bottom of the [[pubis (bone)|pubis]], having a concave outer face; the expansion at the bottom of the apron being at least 15% the length of the entire bone; and the angle between the [[femoral head]] and the cross-sectional axis of the femoral shaft being about 30°. The topology recovered by this analysis is reproduced below.<ref name="desc"/> |
A 2017 [[phylogenetics|phylogenetic analysis]] conducted based on the dataset of McPhee ''et al.'', published in 2015 with the description of ''[[Pulanesaura]]'',<ref name="pulane">{{cite journal | last1 = McPhee | first1 = B.W. | last2 = Bonnan | first2 = M.F. | last3 = Yates | first3 = A.M. | last4 = Neveling | first4 = J. | last5 = Choiniere | first5 = J.N. | title = A new basal sauropod from the pre-Toarcian Jurassic of South Africa: evidence of niche-partitioning at the sauropodomorph–sauropod boundary? | journal = Scientific Reports | volume = 5 | page = 13224 | date = 2015 | doi = 10.1038/srep13224 | url = http://www.nature.com/articles/srep13224}}</ref> found that ''Xingxiulong'' was a basal member of the group [[Massopoda|Sauropodiformes]] once ''[[Blikanasaurus]]'' was removed from the dataset. Within this group, it is closest to the contemporary ''[[Jingshanosaurus]]''. Traits that are shared by ''Xingxiulong'' and ''Jingshanosaurus'' include the [[infratemporal fenestra]] being placed entirely behind the eye socket; the [[scapula]] being at least 20% as wide as it is long; the pubic apron, or the bottom of the [[pubis (bone)|pubis]], having a concave outer face; the expansion at the bottom of the apron being at least 15% the length of the entire bone; and the angle between the [[femoral head]] and the cross-sectional axis of the femoral shaft being about 30°. The topology recovered by this analysis is reproduced below.<ref name="desc"/> |
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[[File:Xingxiulong-6.jpg|thumb|Sacrum of ''Xingxiulong'' (a) compared with ''[[Leonerasaurus]]'' (b), ''[[Plateosaurus|Plateosaurus engelhardti]]'' (c), ''P. trossingensis'' (d), and ''[[Efraasia]]'']] |
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Various alternative phylogenetic placements of ''Xingxiulong'' were tested; out of these, the most plausible alternative involves it being placed as a [[basal (phylogenetics)|basal]] member of the [[Massopoda]], outside of either [[Massospondylidae]] or Sauropodiformes, which only requires two additional evolutionary steps. This is probably due to the curved top margin of the [[postorbital bone|postorbital]] and the presence of a process behind the jaw joint on the [[articular bone|articular]], which are traits that, compared to either Massospondylidae or Sauropodiformes, can be regarded as relatively primitive. Such an alternative scenario would involve significant [[mosaic evolution]] in this evolutionary grade. Placements that required three additional evolutionary steps placed ''Xingxiulong'' between ''Jingshanosaurus'' and ''[[Anchisaurus]]'', or between ''[[Yunnanosaurus]]'' and ''Jingshanosaurus''.<ref name="desc"/> |
Various alternative phylogenetic placements of ''Xingxiulong'' were tested; out of these, the most plausible alternative involves it being placed as a [[basal (phylogenetics)|basal]] member of the [[Massopoda]], outside of either [[Massospondylidae]] or Sauropodiformes, which only requires two additional evolutionary steps. This is probably due to the curved top margin of the [[postorbital bone|postorbital]] and the presence of a process behind the jaw joint on the [[articular bone|articular]], which are traits that, compared to either Massospondylidae or Sauropodiformes, can be regarded as relatively primitive. Such an alternative scenario would involve significant [[mosaic evolution]] in this evolutionary grade. Placements that required three additional evolutionary steps placed ''Xingxiulong'' between ''Jingshanosaurus'' and ''[[Anchisaurus]]'', or between ''[[Yunnanosaurus]]'' and ''Jingshanosaurus''.<ref name="desc"/> |
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Curiously, ''Xingxiulong'' has many characteristics that are normally otherwise seen among the [[Sauropoda]]. These include the four-vertebra [[sacrum]] (which ''[[Mussaurus]]'' also [[convergent evolution|convergently]] acquired); the long pubic plate, or top portion of the pubis, which occupies 40% of the length of the bone (this figure is 25% in most other basal [[sauropodomorpha|sauropodomorphs]], 33% in most sauropods, and 45-50% in the [[Camarasauromorpha]]); and the relative robustness of the femoral shaft, first [[metatarsal bone|metatarsal]], top end of the fifth metatarsal, and scapula. These unique characteristics are probably the product of convergent evolution rather than common ancestry.<ref name="desc"/> |
Curiously, ''Xingxiulong'' has many characteristics that are normally otherwise seen among the [[Sauropoda]]. These include the four-vertebra [[sacrum]] (which ''[[Mussaurus]]'' also [[convergent evolution|convergently]] acquired);<ref name="mus"/><ref name="leonera"/><ref name="sauropoda">{{cite journal | last1 = Upchurch | first1 = P. | title = The phylogenetic relationships of sauropod dinosaurs | journal = Zoological Journal of the Linnaean Society | volume = 124 | issue = 1 | pages = 43-103 | date = 1998 | doi = 10.1006/zjls.1997.0138 | url = http://www.sciencedirect.com/science/article/pii/S0024408297901382}}</ref> the long pubic plate, or top portion of the pubis, which occupies 40% of the length of the bone (this figure is 25% in most other basal [[sauropodomorpha|sauropodomorphs]],<ref name="coloradi"/> 33% in most sauropods,<ref name="sasac">{{cite journal | last1 = Wilson | first1 = J.A. | last2 = Sereno | first2 = P.C. | title = Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs | journal = Journal of Vertebrate Paleontology | volume = 18 | date = 1998 | pages = 1-79 | issue = sup002 | doi = 10.1080/02724634.1998.10011115 | url = http://www.tandfonline.com/doi/abs/10.1080/02724634.1998.10011115}}</ref> and 45-50% in the [[Camarasauromorpha]]<ref name="titano">{{cite journal | last1 = Salgado | first1 = L. | last2 = Coria | first2 = R.A. | last3 = Calvo | first3 = J.O. | title = Evolution of titanosaurid sauropods. I: Phylogenetic analysis based on the postcranial evidence | journal = Ameghiniana | volume = 34 | issue = 1 | pages = 3-32 | date = 1997 | issn = 0002-7014 | url = https://www.researchgate.net/publication/283797197_Evolution_of_titanosaurid_sauropods_I_Phylogenetic_analysis_based_on_the_postcranial_evidence}}</ref>); and the relative robustness of the femoral shaft,<ref name="leonera"/> first [[metatarsal bone|metatarsal]],<ref name="aard">{{cite journal | last1 = Yates | first1 = A.M. | last2 = Bonnan | first2 = M.F. | last3 = Neveling | first3 = J. | last4 = Chinsamy | first4 = A. | last5 = Blackbeard | first5 = M.G. | title = A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism | journal = Proceedings of the Royal Society B | volume = 277 | pages = 787-794 | doi = 10.1098/rspb.2009.1440 | date = 2009 | url = http://rspb.royalsocietypublishing.org/content/early/2009/11/09/rspb.2009.1440}}</ref> top end of the fifth metatarsal, and scapula. These unique characteristics are probably the product of convergent evolution rather than common ancestry.<ref name="desc"/> |
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==Paleobiology== |
==Paleobiology== |
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The overall robustness of the skeleton of ''Xingxiulong'', especially in the hip, [[femur]], and foot, are [[convergent evolution|convergent]] upon [[sauropoda|sauropods]], and collectively suggest that it had a relatively large gut and overall high body mass. However, unlike sauropods, ''Xingxiulong'' would have been [[bipedalism|bipedal]]; it lacks sauropodan adaptations to [[quadrupedalism]] including relatively longer forelimbs, the [[ulna]] bearing a prominent process on the front of its side, and the [[femur]] having a relatively straight shaft. Instead, its ulna and femur are overall more reminiscent of the typical basal [[sauropodomorpha|sauropodomorph]]. The large and robust [[scapula]]e of ''Xingxiulong'', ''[[Jingshanosaurus]]'', and ''[[Yunnanosaurus]]'' may have increased the mobility of the forelimb during bipedal browsing, but this trait was later adopted as an adaptation to quadrupedality in sauropods.<ref name="desc"/> |
The overall robustness of the skeleton of ''Xingxiulong'', especially in the hip, [[femur]], and foot, are [[convergent evolution|convergent]] upon [[sauropoda|sauropods]], and collectively suggest that it had a relatively large gut and overall high body mass. However, unlike sauropods, ''Xingxiulong'' would have been [[bipedalism|bipedal]]; it lacks sauropodan adaptations to [[quadrupedalism]] including relatively longer forelimbs, the [[ulna]] bearing a prominent process on the front of its side, and the [[femur]] having a relatively straight shaft.<ref name="aard"/> Instead, its ulna and femur are overall more reminiscent of the typical basal [[sauropodomorpha|sauropodomorph]]. The large and robust [[scapula]]e of ''Xingxiulong'', ''[[Jingshanosaurus]]'', and ''[[Yunnanosaurus]]'' may have increased the mobility of the forelimb during bipedal browsing, but this trait was later adopted as an adaptation to quadrupedality in sauropods.<ref name="desc"/><ref name="pulane"/> |
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==Paleoecology== |
==Paleoecology== |
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The [[Lufeng Formation]] contains [[mudstone]]s and [[siltstone]]s from lakes, rivers, and [[overbank]] deposits. Many [[sauropodomorpha|sauropodomorphs]] asides from ''Xingxiulong'' are known from the Lufeng Formation, including ''[[Lufengosaurus|Lufengosaurus huenei]]'', ''L. magnus'', ''[[Yunnanosaurus|Yunnanosaurus huangi]]'', ''Y. robustus'', ''[[Gyposaurus|"Gyposaurus" sinensis]]'', ''[[Jingshanosaurus|Jingshanosaurus xinwaensis]]'', ''[[Chuxiongosaurus|Chuxiongosaurus lufengensis]]'',<ref name="desc"/> ''[[Xixiposaurus|Xixiposaurus suni]]'', "[[Yizhousaurus|Yizhousaurus sunae]]", and ''[[Pachysuchus|Pachysuchus imperfectus]]''. Also present are the [[theropoda|theropods]] ''[[Sinosaurus|Sinosaurus triassicus]]'', ''[[Lukousaurus|Lukousaurus yini]]'', ''[[Shidaisaurus|Shidaisaurus jinae]]'', and ''[[Eshanosaurus|Eshanosaurus deguchiianus]]''; the [[ornithischia]]ns ''[[Tatisaurus|Tatisaurus oehleri]]'' and ''[[Bienosaurus lufengensis]]''; the [[crocodylomorpha|crocodylomorphs]] ''[[Dibothrosuchus|Dibothrosuchus elaphros]]'', ''[[Platyognathus|Platyognathus hsui]]'', ''[[Microchampsa|Microchampsa scutata]]'', and ''[[Dianosuchus|Dianosuchus changchiawaensis]]'', and ''[[Dianchungosaurus|Dianchungosaurus lufengensis]]''; the indeterminate [[archosaur]] ''[[Strigosuchus|Strigosuchus licinus]]''; the [[sphenodontia]]ns ''[[Clevosaurus|Clevosaurus petilus]]'', ''C. wangi'', and ''C. mcgilli''; the [[tritylodontidae|tritylodontid]] [[cynodont]]s ''[[Bienotherium|Bienotherium yunnanense]]'', ''B. minor'', ''B. magnum'', ''[[Lufengia|Lufengia deltcata]]'', ''[[Yunnanodon|Yunnanodon brevirostre]]'', and ''[[Dianzhongia|Dianzhongia longirostrata]]''; the mammals ''[[Sinoconodon|Sinoconodon rigneyi]]'', ''[[Morganucodon|Morganucodon oehleri]]'', ''M. heikoupengensis'', and ''[[Kunminia|Kunminia minima]]''; [[proganochelys|proganochelyid]] turtles; and a [[labyrinthodontia|"labyrinthodont"]] amphibian. --> |
The [[Lufeng Formation]] contains [[mudstone]]s and [[siltstone]]s from lakes, rivers, and [[overbank]] deposits.<ref name="ls"/> Many [[sauropodomorpha|sauropodomorphs]] asides from ''Xingxiulong'' are known from the Lufeng Formation, including ''[[Lufengosaurus|Lufengosaurus huenei]]'', ''L. magnus'', ''[[Yunnanosaurus|Yunnanosaurus huangi]]'', ''Y. robustus'', ''[[Gyposaurus|"Gyposaurus" sinensis]]'', ''[[Jingshanosaurus|Jingshanosaurus xinwaensis]]'', ''[[Chuxiongosaurus|Chuxiongosaurus lufengensis]]'',<ref name="desc"/> ''[[Xixiposaurus|Xixiposaurus suni]]'', "[[Yizhousaurus|Yizhousaurus sunae]]",<ref name="lf">{{cite journal | last1 = Xing | first1 = L. | last2 = Rothschild | first2 = B.M. | last3 = Ran | first3 = H. | last4 = Miyashita | first4 = T. | last5 = Persons | first5 = W.S. | last6 = Sekiya | first6 = T. | last7 = Zhang | first7 = J. | last8 = Wang | first8 = T. | last9 = Dong | first9 = Z. | title = Vertebral fusion in two Early Jurassic sauropodomorph dinosaurs from the Lufeng Formation of Yunnan, China | journal = Acta Palaeontologica Polonica | volume = 60 | issue = 3 | date = 2015 | pages = 643-649 | doi = 10.4202/app.00001.2013 | url = https://www.app.pan.pl/article/item/app000012013.html}}</ref> and ''[[Pachysuchus|Pachysuchus imperfectus]]''. Also present are the [[theropoda|theropods]] ''[[Sinosaurus|Sinosaurus triassicus]]'', ''[[Lukousaurus|Lukousaurus yini]]'',<ref name="ls"/> ''[[Shidaisaurus|Shidaisaurus jinae]]'',<ref name="lf"/><ref name="shidai">{{cite journal | last1 = Wu | first1 = X.-C. | last2 = Currie | first2 = P.J. | last3 = Dong | first3 = Z. | last4 = Pan | first4 = S. | last5 = Wang | first5 = T. | title = A New Theropod Dinosaur from the Middle Jurassic of Lufeng, Yunnan, China | journal = Acta Geologica Sinica | volume = 83 | issue = 1 | pages = 9-24 | date = 2009 | doi = 10.1111/j.1755-6724.2009.00002.x | url = http://onlinelibrary.wiley.com/doi/10.1111/j.1755-6724.2009.00002.x/abstract}}</ref> and ''[[Eshanosaurus|Eshanosaurus deguchiianus]]'';<ref name="eshan">{{cite journal | last1 = Xu | first1 = X. | last2 = Zhao | first2 = X. | last3 = Clark | first3 = J.M. | title = A New Therizinosaur from the Lower Jurassic Lower Lufeng Formation of Yunnan, China | journal = Journal of Vertebrate Paleontology | volume = 21 | issue = 3 | date = 2001 | pages = 477-483 | url = https://www.jstor.org/stable/20061976?seq=1#page_scan_tab_contents}}</ref> the [[ornithischia]]ns ''[[Tatisaurus|Tatisaurus oehleri]]''<ref name="ls"/> and ''[[Bienosaurus lufengensis]]''; the [[crocodylomorpha|crocodylomorphs]] ''[[Dibothrosuchus|Dibothrosuchus elaphros]]'', ''[[Platyognathus|Platyognathus hsui]]'', ''[[Microchampsa|Microchampsa scutata]]'', and ''[[Dianosuchus|Dianosuchus changchiawaensis]]'', and ''[[Dianchungosaurus|Dianchungosaurus lufengensis]]''; the indeterminate [[archosaur]] ''[[Strigosuchus|Strigosuchus licinus]]''; the [[sphenodontia]]ns ''[[Clevosaurus|Clevosaurus petilus]]'', ''C. wangi'', and ''C. mcgilli''; the [[tritylodontidae|tritylodontid]] [[cynodont]]s ''[[Bienotherium|Bienotherium yunnanense]]'', ''B. minor'', ''B. magnum'', ''[[Lufengia|Lufengia deltcata]]'', ''[[Yunnanodon|Yunnanodon brevirostre]]'', and ''[[Dianzhongia|Dianzhongia longirostrata]]''; the mammals ''[[Sinoconodon|Sinoconodon rigneyi]]'', ''[[Morganucodon|Morganucodon oehleri]]'', ''M. heikoupengensis'', and ''[[Kunminia|Kunminia minima]]''; [[proganochelys|proganochelyid]] turtles; and a [[labyrinthodontia|"labyrinthodont"]] amphibian.<ref name="ls">{{cite book | last1 = Luo | first1 = Z. | last2 = Wu | first2 = X.-C. | chapter = The small tetrapods of the Lower Lufeng Formation, Yunnan, China | editor-last1 = Fraser | editor-first1 = N.C. | editor-last2 = Sues | editor-first2 = H.-D. | date = 1997 | title = In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods | publisher = Cambridge University Press | location = Cambridge | pages = 251-270 | chapter-url = https://www.researchgate.net/publication/285880874_Correlation_of_vertebrate_assemblage_of_the_Lower_Lufeng_Formation_Yunnan_China | url = http://www.cambridge.org/us/academic/subjects/earth-and-environmental-science/palaeontology-and-life-history/shadow-dinosaurs-early-mesozoic-tetrapods?format=PB&isbn=9780521458993 | isbn = 9780521458993}}</ref> --> |
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==Referencias== |
==Referencias== |
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Revisión del 23:00 28 feb 2017
| Xingxiulong | ||
|---|---|---|
| Rango temporal: Hettangiense Jurásico | ||
 Fotografías de elementos óseos (a-n) y reconstrucción del esqueleto (o) de Xingxiulong. | ||
| Taxonomía | ||
| Reino: | Animalia | |
| Filo: | Chordata | |
| Clase: | Sauropsida | |
| Superorden: | Dinosauria | |
| Orden: | Saurischia | |
| Suborden: | Sauropodomorpha | |
| Infraorden: | Sauropoda | |
| (sin rango): | Massopoda | |
| (sin rango): | Sauropodiformes | |
| Género: |
Xingxiulong Wang et al., 2017 | |
| Especie tipo | ||
|
Xingxiulong chengi Wang et al., 2017 | ||
Xingxiulong es un género extinto de dinosaurio sauropodiforme bípedo que vivió durante el Jurásico Inferior en China. Solo incluye a una especie, X. chengi, descrita por Wang et al. en 2017.
Descripción
Xingxiulong era un sauropodiforme de tamaño mediano, con una longitud adulta de 4 - 5 metros y una altura de 1 - 1.5 metros hasta la cadera. Los dos mayores especímenes, LFGT-D0002 and LFGT-D0003, son de adultos al juzgar por la fusión completa en sus cráneos; el tercer espécimen, LFGT-D0001, es 14% menor y probablemente se trata de un subadulto teniendo en cuenta la fusión incompleta de sus vértebras.[1]
Cráneo y mandíbula
A diferencia del contemporáneo Lufengosaurus, Xingxiulong no tiene una cresta en los lados de su maxilar. Se preservaron once alvéolos dentales a lo largo del maxilar. Más atrás, en frente de la órbita ocular, el hueso lacrimal tiene una proyección notoria cerca de la parte superior de su extremo frontal, la cual también es observada en Lufengosaurus, Adeopapposaurus, Massospondylus y Riojasaurus, pero no en Yunnanosaurus, Jingshanosaurus, o los sauropodiformes más avanzados. La superficie de contacto entre el yugal y el postorbital es bastante alargada, como en Lufengosaurus pero no en Yunnanosaurus. Entre las tres ramas del yugal, aquella dirigida hacia atrás forma un ángulo de 80° con respecto a la rama que se proyecta hacia arriba, lo cual es similar a Plateosaurus y Thecodontosaurus pero es mucho mayor que en otros sauropodomorfos.[1]
En la base del cráneo, el cuadratoyugal tiene dos ramos, uno apuntando hacia adelante y otro hacia arriba; estos son aproximadamente perpendiculares entre sí, a diferencia de Lufengosaurus (con ángulo de 45°), Yunnanosaurus (ángulo de 60°) y Jingshanosaurus (ángulo de 110°). Encima del cuadratoyugal, el hueso cuadrado tiene dos cóndilos articulares, con uno subtriangular y orientado hacia afuera y uno más redondeado orientado hacia adentro; este último cóndilo se sitúa más cerca de la parte inferior, como en Lufengosaurus y Yunnanosaurus pero no en Plateosaurus. En la parte posterior del cráneo, entre los parietales y los supraoccipitales, hay una fenestra postparietal desarrollada de forma prominente; el propio supraoccipital desciende hacia adelante en su extremo inferior hasta rematar la base del cráneo. Los procesos del basipterigoides son largos, delgados y se proyectan hacia abajo y hacia afuera como en Plateosaurus pero a diferencia de Lufengosaurus y Jingshanosaurus, formando un ángulo de 80° entre sí.[1]
Comparado con Lufengosaurus, Yunnanosaurus y Jingshanosaurus, en Xingxiulong los huesos angular y surangular se extienden mucho más en el frente de la fenestra mandibular, en lo que se parece más a Adeopapposaurus y a Plateosaurus.[2] El articular posee un proceso piramidal proyectado hacia adentro como extensión de la articulación de la mandíbula; en su extremo posterior, también posee un proceso dirigido hacia arriba en forma de pestaña, lo cual también es visto en Coloradisaurus,[3] Jingshanosaurus y en un sauropodomorfo sin nombrar.[1]
Referencias
- ↑ a b c d Wang, Y.-M.; You, H.-L.; Wang, T. (2017). «A new basal sauropodiform dinosaur from the Lower Jurassic of Yunnan Province, China». Scientific Reports 73: 41881. doi:10.1038/srep41881.
- ↑ Prieto-Marquez, A.; Norell, M. (2011). «Redescription of a nearly complete skull of Plateosaurus (Dinosauria, Sauropodomorpha) from the late Triassic of Trossingen (Germany)». American Museum Novitates 3727: 1-58.
- ↑ Apaldetti, C.; Martinez, R.N.; Pol, D.; Souter, T. (2014). «Redescription of the Skull of Coloradisaurus brevis (Dinosauria, Sauropodomorpha) from the Late Triassic Los Colorados Formation of the Ischigualasto-Villa Union Basin, northwestern Argentina». Journal of Vertebrate Paleontology 34 (5): 1113-1132. doi:10.1080/02724634.2014.859147.