Post by Cross on Mar 9, 2016 11:55:36 GMT 5
Yutyrannus huali
(Above illustration by Andrey Atuchin)
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Class: Reptilia or Clade: Sauropsida
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: Archelosauria
Clade: Archosauromorpha
Clade: Archosauriformes
Clade: Crurotarsi
Clade: Archosauria
Clade: Avemetatarsalia
Clade: Ornithodira
Clade: Dinosauromorpha
Clade: Dinosauriformes
Clade: Dinosauria
Order: Saurischia
Clade: Eusaurischia
Suborder: Theropoda
Clade: Coelurosauria
Clade : †Tyrannosauroidea
Genus: †Yutyrannus
Species: †Y. huali
Yutyrannus huali is a species of giant proceratosaurid tyrannosauroid theropod from the lower Cretaceous (125 million years ago) of northeastern China. The species is known on the basis of three nearly-complete and well-preserved skeletons of different ontogenetic stages. The holotypic specimen, ZCDM V5000, is a large, skeletally mature adult individual based on the ossified neurocentral sutures. The femur length of the holotype is 85 centimeters long, and comparisons with other tyrannosauroid taxa suggest that ZCDM V5000 exceeded some of the late Cretaceous tyrannosaurids in body size, with ZCDM V5000 being estimated to be 9-meters in total body length with an estimated body mass of 1,414 kilograms based on an empirical equation. However, taking into account how allometric methods such as this equation are known to underestimate the body mass of extinct organisms in the past, and comparing the anatomy and body proportions of Y. huali to those of other tyrannosaurs, a body mass of roughly 2,000 kilograms is probably a more plausible range of body mass for the 9-meter long ZCDM V5000. This slightly exceeds the Campanian tyrannosaurs Albertosaurus and Gorgosaurus in size.
(Photograph and diagram of the holotype specimen ZCDM V5000).
Species-level diagnosis from Xu et al. (2012) :
"A gigantic tyrannosauroid distinguishable from other tyrannosauroids by the unique presence of a rugose, highly fenestrated midline crest formed by the premaxillae and nasals, an anteroventrally projecting orbital process in the area of the junction between the frontal and jugal processes of the postorbital, a large concavity onthe lateral surface of the main body of the postorbital, and an external mandibular fenestra located mostly within the surangular. Also differs from Sinotyrannus in that the morphologically lateral surface of the maxillary process of the premaxilla faces dorsally, the maxilla lacks an anterior ramus, the maxillary fenestra is posteriorly positioned, the antorbital fossa has a posteroventrally sloping ventral margin, and the ilium has a straight dorsal margin and a postacetabular process whose ventral margin bears a lobe-like flange"
(Skull reconstruction by Scott Hartman. Note the allosauroid-like shape and proportions of the skull).
The cranium of Yutyrannus huali is visibly carnosaur-like in shape despite being a tyrannosauroid, with a narrow, tapered morphology of the rostrum and preorbital region and a sloping nasal region. A small, horn-like crest is present on the dorsal surface of the lacrimal and the anterior region of the nasal posterodorsal to the premaxilla is rugose in texture.
Yutyrannus shares with Guanlong wucaii the presence of an ornamented surface with a single crest. Guanlong wucaii possesses a wedge-shaped metatarsal-III while this feature is absent in Yutyrannus. Yutyrannus huali also shares with Guanlong the presence of at least one small foramina on the jugal process. Pneumatic recesses are present on the lateral surface of the nasal crest and ascending ramus of the maxilla in Yutyrannus huali specimen ELDM V5001 whereas pneumatic recesses are only present on the lacrimal in Guanlong wucaii.
Xu et al. (2012) were able to identify several morphological variations in the cranial anatomy of the three specimens of Y. huali that are explainable by ontogenetic changes. The cranium becomes increasingly deep and robust, the premaxilla becomes narrower and taller, the premaxilla's anterior portion becomes more medially oriented and robust, the lateral surface of the maxillary process of the premaxilla rotates to fac dorsally, and the maxillary fenesta becomes more anteriorly located.
The presence of large, filamentous protofeathers on the body of Yutyrannus huali makes it the largest organism ever found with direct evidence of having feathers. This suggests that perhaps all tyrannosauroids, small or large, probably had protofeathers as well. It is often argued that later tyrannosaurs could not have had feathers due to existing in much warmer climates, but this is untrue since integument is only tanginally/partly correlated with the environment. Giant proboscideans and ground sloths as well as aepyornithids are known to have thick coats of fur and feathers despite living in tropical environments.
Originally recovered as an intermediate basal tyrannosauroid by Xu et al. (2012), this systematic position was later revised by Brusatte and Carr (2016) in their phylogenetic analysis of Tyrannosauroids making use of Bayesian topology methods rather than Parsimony methods. Their analysis recoveres Yutyrannus huali as a giant proceratosaurid tyrannosauroid.
-----References and cited literature
Brusatte, S. L. and Carr, T. D. The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Sci. Rep. 6, 20252; doi: 10.1038/srep20252 (2016).
Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., ... & Wang, S. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484(7392), 92-95.
(Above illustration by Andrey Atuchin)
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Class: Reptilia or Clade: Sauropsida
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: Archelosauria
Clade: Archosauromorpha
Clade: Archosauriformes
Clade: Crurotarsi
Clade: Archosauria
Clade: Avemetatarsalia
Clade: Ornithodira
Clade: Dinosauromorpha
Clade: Dinosauriformes
Clade: Dinosauria
Order: Saurischia
Clade: Eusaurischia
Suborder: Theropoda
Clade: Coelurosauria
Clade : †Tyrannosauroidea
Genus: †Yutyrannus
Species: †Y. huali
Yutyrannus huali is a species of giant proceratosaurid tyrannosauroid theropod from the lower Cretaceous (125 million years ago) of northeastern China. The species is known on the basis of three nearly-complete and well-preserved skeletons of different ontogenetic stages. The holotypic specimen, ZCDM V5000, is a large, skeletally mature adult individual based on the ossified neurocentral sutures. The femur length of the holotype is 85 centimeters long, and comparisons with other tyrannosauroid taxa suggest that ZCDM V5000 exceeded some of the late Cretaceous tyrannosaurids in body size, with ZCDM V5000 being estimated to be 9-meters in total body length with an estimated body mass of 1,414 kilograms based on an empirical equation. However, taking into account how allometric methods such as this equation are known to underestimate the body mass of extinct organisms in the past, and comparing the anatomy and body proportions of Y. huali to those of other tyrannosaurs, a body mass of roughly 2,000 kilograms is probably a more plausible range of body mass for the 9-meter long ZCDM V5000. This slightly exceeds the Campanian tyrannosaurs Albertosaurus and Gorgosaurus in size.
(Photograph and diagram of the holotype specimen ZCDM V5000).
Species-level diagnosis from Xu et al. (2012) :
"A gigantic tyrannosauroid distinguishable from other tyrannosauroids by the unique presence of a rugose, highly fenestrated midline crest formed by the premaxillae and nasals, an anteroventrally projecting orbital process in the area of the junction between the frontal and jugal processes of the postorbital, a large concavity onthe lateral surface of the main body of the postorbital, and an external mandibular fenestra located mostly within the surangular. Also differs from Sinotyrannus in that the morphologically lateral surface of the maxillary process of the premaxilla faces dorsally, the maxilla lacks an anterior ramus, the maxillary fenestra is posteriorly positioned, the antorbital fossa has a posteroventrally sloping ventral margin, and the ilium has a straight dorsal margin and a postacetabular process whose ventral margin bears a lobe-like flange"
(Skull reconstruction by Scott Hartman. Note the allosauroid-like shape and proportions of the skull).
The cranium of Yutyrannus huali is visibly carnosaur-like in shape despite being a tyrannosauroid, with a narrow, tapered morphology of the rostrum and preorbital region and a sloping nasal region. A small, horn-like crest is present on the dorsal surface of the lacrimal and the anterior region of the nasal posterodorsal to the premaxilla is rugose in texture.
Yutyrannus shares with Guanlong wucaii the presence of an ornamented surface with a single crest. Guanlong wucaii possesses a wedge-shaped metatarsal-III while this feature is absent in Yutyrannus. Yutyrannus huali also shares with Guanlong the presence of at least one small foramina on the jugal process. Pneumatic recesses are present on the lateral surface of the nasal crest and ascending ramus of the maxilla in Yutyrannus huali specimen ELDM V5001 whereas pneumatic recesses are only present on the lacrimal in Guanlong wucaii.
Xu et al. (2012) were able to identify several morphological variations in the cranial anatomy of the three specimens of Y. huali that are explainable by ontogenetic changes. The cranium becomes increasingly deep and robust, the premaxilla becomes narrower and taller, the premaxilla's anterior portion becomes more medially oriented and robust, the lateral surface of the maxillary process of the premaxilla rotates to fac dorsally, and the maxillary fenesta becomes more anteriorly located.
The presence of large, filamentous protofeathers on the body of Yutyrannus huali makes it the largest organism ever found with direct evidence of having feathers. This suggests that perhaps all tyrannosauroids, small or large, probably had protofeathers as well. It is often argued that later tyrannosaurs could not have had feathers due to existing in much warmer climates, but this is untrue since integument is only tanginally/partly correlated with the environment. Giant proboscideans and ground sloths as well as aepyornithids are known to have thick coats of fur and feathers despite living in tropical environments.
Originally recovered as an intermediate basal tyrannosauroid by Xu et al. (2012), this systematic position was later revised by Brusatte and Carr (2016) in their phylogenetic analysis of Tyrannosauroids making use of Bayesian topology methods rather than Parsimony methods. Their analysis recoveres Yutyrannus huali as a giant proceratosaurid tyrannosauroid.
-----References and cited literature
Brusatte, S. L. and Carr, T. D. The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Sci. Rep. 6, 20252; doi: 10.1038/srep20252 (2016).
Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., ... & Wang, S. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484(7392), 92-95.
