[D] Jinzhousaurus yangi [Su] [sG] [T]
Describer
Wang & Xu, 2001
Time
Cretaceous Early Aptian
Classification
Ornithischia Ornithopoda Iguanodontia Iguanodontidae
Diet
Herbivore
Fossilsite
Yixian Formation, Liaoxi, Liaoning, China
Length
7 meter (approximately)
Info
Genus - Typespecies - Skull
Based on the cranial and dentalmorphology of a specimen from the Yixian Formation, Jehol Biota of western Liaoning. Jinzhousaurus yangi displays a number of characteristics similar to those seen in derived iguanodontids, however a few primitive characteristics are also described. Some interesting characteristics include the absence of antorbitalfenestra and the frontal excluded from the participation in orbit, which are closer to the condition in hadrosaurids .
The unusual combination of the characteristics provides important data for assessing morphological evolution toward hadrosaurs. The new discovery also represents the first reported largesized dinosaur from Jehol fauna in western Liaoning, and increases the diversity of this famous fauna.Furthermore, the discovery of a derived iguanodontid from the Yixian Formation provides further evidence supporting a Cretaceous age of the Jehol fauna, which is consistent with an isotopic age.
Etymology
The genus name Jinzhou refers to the larger geographic area that includes the type locality; the species name is in horner of Yang Zhongjian who is the founder of the vertebrate paleontology in China.
Locality and horizon
Baicaigou, Toutai, Yixian County, Liaoning; Dakangpu member, the middle part of the Yixian Formation (comparable to Dawangzhangzi Bed); Huaterivian, Early Cretaceous (based on a 135 Ma J/K boundary) or Barremian, Early Cretaceous (a 144 Ma J/K boundary)
Known material/holotype
IVPP V12691, almost complete skeleton including complete skull.
Diagnosis of genus (as for the type species)
Large \\\\\\\"Iguanodontid\\\\\\\"; skull about 500 mm long, 280 mm high, antorbital portion long; 63 percent of skull length; maxilla triangularin lateral view, with long, narrow rostral extension; absence of antiorbital fenestra; frontals fused into single element; frontals extending rostrally, near rostral border of orbit, not contributing to formation of orbit; quadrate having curved shaft; outside of supretemporal foramen pointed forward; quadratojugal large; ventral process of predentary very weakly bifucated; dorsal end ventral margins of dentary straight; more than 16 dentary teeth, teeth becoming larger distally.
Description
A nearly complete skeleton, about 7 m in total length. The skull exposes its left and dorsal sides and visible elements include premaxilla, maxilla, nasal, lacrymal, prefrontal, frontal, postorbital, palpebral, parietal, jugal, qudratojugal, angular, surangular, quadrate, paraoccipital process, hyoid, predentary, dentary, and teeth.
Skull
The skull is about 500 mm in length (from the tip of the snout to the posterior margin of the parietal), about 280 mm in height. The antorbital portion is long, accounting for 64% the skull length. The dorsal margin of the snout mildly raised, describing a weak arch, and the skull roof is relatively flat. The orbit is relatively small, about 100 mm in anteroposterior diameter. The most occipital elements are obscured by the squamosals and parietals, with the exception that the left paraoccipital process is exposed in the left supratemporal Fenestra. The left and right parietals are fused along the middle, the maximum transverse width of which is about 130 mm and anteroposterior length about 75 mm. It is significantly wider than in other iguanodontids. Posteriorly a saggital crest is present. The supratemporal fenestra is oval in outline, narrower anteriorly and wider posteriorly. The maximum length of the fenestra is about 90 mm and the maximum width is about half the anteroposterior length. The long axis of the fenestra is oriented anterolaterally as in Ouranosaurus but different from Iguanodon in which it is directed anteriorly or anteromedially
The infratemporal fenestra is elliptical in outline. The frontals are fused into one element. Anteriorly it contacts the nasal through a straight suture; laterally it contacts the prefrontal and postorbital; and posteriorly it contacts the parietal through sinuous suture, more similar to the condition in Iguanodon but different from the straight one in Ouranosaurus and Camptosaurus. The frontals extend quite anteriorly, close to the anterior border of the orbit. Different from other iguanodontids, the frontal does not contribute to the formation of the orbit. The nasal is wide posteriorly and narrow anteriorly. A shallow groove is present along the midline of the nasals and a fossa is present on the dorsal surface of the posterior nasals, but this is probably due to the preservation. The nasal extends anteriorly close to the anterior margin of the external naris and posteriorly to contact the prefrontal and frontal at the level of the anterior border of the orbit. The external naris is large, about 210 mm in length. The subnarial fossa is well developed.
The prefrontal is large, about 300 mm long, accounting for about 60% the length of the skull. The rostral portion of the skull is expanded as in other iguanodontids. The maxillary process of the premaxilla is enlarged posteriorly, contacting the maxilla ventrally and the nasal dorsally. Its posterior end contacts the lacrymal. The main body of the premaxilla is enlarged, extending ventrally off to the ventral margin of the maxilla. The maxilla is comparatively small, triangular in outline. It is about 170 mm long and 80 mm in maximum height. A few large nutrient foramina are visible on the lateral surface of the maxilla.
Unlike other iguanodontids, the antorbital fenestra is absent as in hadrosaurids. Among other iguanodontids, Iguanodon lakotaensis has a large antorbital fenestra and others have a relatively small one. The jugal forms the ventral margin of the orbit. Its maxillary process appears to insert into a groove on the posterior lacrymal, and its postorbital process is oriented posterodorsally, contacting the ventral process of the postorbital. Posteriorly the jugal is large, sheet-like, forming the ventral and possibly part of the posterior margins of the infratemporal fenestra. The qudratojugal appears to be excluded from the posterior margin of the infratemporal fenestra. The lacrymal is large, and rough laterally. The rod-like palpebral is preserved and restricts its contaction with the only prefrontal. The prefrontal contacts the frontal, nasal, and lacrymal, forming the anterodorsal border of the orbit. The postorbital has a robust ventral process.
The squamosal contributes to the formation of the posterior and posterolateral margins of the supratemporal fenestra, and the postodorsal margin of the infratemporal fenestra. The left and right squamosal contacts each other, separating the parietals from the occipital region in dorsal view. The quadrate has a curved shaft as in Iguanodon atherfieldensis, Camptosaurus, and Ouranosaurus . In Iguanodon bernissartensis and Probactrosaurus, it is straight.
Mandible
The mandible exposes the predentary, dentary, angular and surangular. The predentary is denticulate anteriorly. Its ventral process is very weakly bifurcated. The dentary is about 350 mm long and about 90 mm in the maximum height. The dorsal and ventral margins of the dentary are straight as in Camptosaurus, and Ouranosaurus. In Iguanodon and Probactrosaurus the anterior end of the dentary is downturned. The first dentary tooth is positioned relative to the predentary by a distance of two-tooth position as in other iguanodontids. Seven nutrient foramina are present on the anterior dentary in lateral view. The relatively large surangular foramen is present, and the angular exposes a small portion laterally.
Dentition
The maxillary teeth are smaller than the dentary ones in size. Generally the primary ridge on the lateral surface of the maxillary tooth crown is well developed, and positioned slightly posteriorly. A weakly developed secondary ridge is present between the primary ridge and well-developed the anterior shelf of the crown. The posterior shelf of the crown is weakly developed. There are more than 16 dentary teeth that become larger posteriorly. The crowns are heavily weared and the wear facets face dorsolaterally. The first and second dentary teeth are at their erupted position, with well-developed serrations. The sixth alveolus contains a functional as well as a replacement tooth. (Wang and Xu , 2001).
Carpenter & Ishida (2010) Early and “Middle” Cretaceous Iguanodonts in Time and Space Journal of Iberian Geology 36 (2) 145-164
Jinzhousaurus yangi Wang and Xu 2001
Locality
Baicaigou, Toutai, Yixian County, Liaoning, People’s Republic of China.
Horizon
Dakangpu Bed (equivalent to the Dawangzhangzi Bed), Yixian Formation
Age
early Aptian (Wang and Zhou, 2003)
Comments
Know from two specimens, the holotype with a complete, articulated skeleton, and a second disarticulated anterior portion of a skeleton (including a partially disarticulated skull). The postcrania remain undescribed and unillustrated except for the ilium described here. The ilium is long and low, with a relatively straight preacetabular process, a long, tapering postacetabular process that is abruptly truncated distally, and a moderately well developed, triangular brevis shelf. The ischial peduncle is slightly expanded onto the lateral surface. No lateral iliac crest is present.
Wang & Xu, 2001
Time
Cretaceous Early Aptian
Classification
Ornithischia Ornithopoda Iguanodontia Iguanodontidae
Diet
Herbivore
Fossilsite
Yixian Formation, Liaoxi, Liaoning, China
Length
7 meter (approximately)
Info
Genus - Typespecies - Skull
Based on the cranial and dentalmorphology of a specimen from the Yixian Formation, Jehol Biota of western Liaoning. Jinzhousaurus yangi displays a number of characteristics similar to those seen in derived iguanodontids, however a few primitive characteristics are also described. Some interesting characteristics include the absence of antorbitalfenestra and the frontal excluded from the participation in orbit, which are closer to the condition in hadrosaurids .
The unusual combination of the characteristics provides important data for assessing morphological evolution toward hadrosaurs. The new discovery also represents the first reported largesized dinosaur from Jehol fauna in western Liaoning, and increases the diversity of this famous fauna.Furthermore, the discovery of a derived iguanodontid from the Yixian Formation provides further evidence supporting a Cretaceous age of the Jehol fauna, which is consistent with an isotopic age.
Etymology
The genus name Jinzhou refers to the larger geographic area that includes the type locality; the species name is in horner of Yang Zhongjian who is the founder of the vertebrate paleontology in China.
Locality and horizon
Baicaigou, Toutai, Yixian County, Liaoning; Dakangpu member, the middle part of the Yixian Formation (comparable to Dawangzhangzi Bed); Huaterivian, Early Cretaceous (based on a 135 Ma J/K boundary) or Barremian, Early Cretaceous (a 144 Ma J/K boundary)
Known material/holotype
IVPP V12691, almost complete skeleton including complete skull.
Diagnosis of genus (as for the type species)
Large \\\\\\\"Iguanodontid\\\\\\\"; skull about 500 mm long, 280 mm high, antorbital portion long; 63 percent of skull length; maxilla triangularin lateral view, with long, narrow rostral extension; absence of antiorbital fenestra; frontals fused into single element; frontals extending rostrally, near rostral border of orbit, not contributing to formation of orbit; quadrate having curved shaft; outside of supretemporal foramen pointed forward; quadratojugal large; ventral process of predentary very weakly bifucated; dorsal end ventral margins of dentary straight; more than 16 dentary teeth, teeth becoming larger distally.
Description
A nearly complete skeleton, about 7 m in total length. The skull exposes its left and dorsal sides and visible elements include premaxilla, maxilla, nasal, lacrymal, prefrontal, frontal, postorbital, palpebral, parietal, jugal, qudratojugal, angular, surangular, quadrate, paraoccipital process, hyoid, predentary, dentary, and teeth.
Skull
The skull is about 500 mm in length (from the tip of the snout to the posterior margin of the parietal), about 280 mm in height. The antorbital portion is long, accounting for 64% the skull length. The dorsal margin of the snout mildly raised, describing a weak arch, and the skull roof is relatively flat. The orbit is relatively small, about 100 mm in anteroposterior diameter. The most occipital elements are obscured by the squamosals and parietals, with the exception that the left paraoccipital process is exposed in the left supratemporal Fenestra. The left and right parietals are fused along the middle, the maximum transverse width of which is about 130 mm and anteroposterior length about 75 mm. It is significantly wider than in other iguanodontids. Posteriorly a saggital crest is present. The supratemporal fenestra is oval in outline, narrower anteriorly and wider posteriorly. The maximum length of the fenestra is about 90 mm and the maximum width is about half the anteroposterior length. The long axis of the fenestra is oriented anterolaterally as in Ouranosaurus but different from Iguanodon in which it is directed anteriorly or anteromedially
The infratemporal fenestra is elliptical in outline. The frontals are fused into one element. Anteriorly it contacts the nasal through a straight suture; laterally it contacts the prefrontal and postorbital; and posteriorly it contacts the parietal through sinuous suture, more similar to the condition in Iguanodon but different from the straight one in Ouranosaurus and Camptosaurus. The frontals extend quite anteriorly, close to the anterior border of the orbit. Different from other iguanodontids, the frontal does not contribute to the formation of the orbit. The nasal is wide posteriorly and narrow anteriorly. A shallow groove is present along the midline of the nasals and a fossa is present on the dorsal surface of the posterior nasals, but this is probably due to the preservation. The nasal extends anteriorly close to the anterior margin of the external naris and posteriorly to contact the prefrontal and frontal at the level of the anterior border of the orbit. The external naris is large, about 210 mm in length. The subnarial fossa is well developed.
The prefrontal is large, about 300 mm long, accounting for about 60% the length of the skull. The rostral portion of the skull is expanded as in other iguanodontids. The maxillary process of the premaxilla is enlarged posteriorly, contacting the maxilla ventrally and the nasal dorsally. Its posterior end contacts the lacrymal. The main body of the premaxilla is enlarged, extending ventrally off to the ventral margin of the maxilla. The maxilla is comparatively small, triangular in outline. It is about 170 mm long and 80 mm in maximum height. A few large nutrient foramina are visible on the lateral surface of the maxilla.
Unlike other iguanodontids, the antorbital fenestra is absent as in hadrosaurids. Among other iguanodontids, Iguanodon lakotaensis has a large antorbital fenestra and others have a relatively small one. The jugal forms the ventral margin of the orbit. Its maxillary process appears to insert into a groove on the posterior lacrymal, and its postorbital process is oriented posterodorsally, contacting the ventral process of the postorbital. Posteriorly the jugal is large, sheet-like, forming the ventral and possibly part of the posterior margins of the infratemporal fenestra. The qudratojugal appears to be excluded from the posterior margin of the infratemporal fenestra. The lacrymal is large, and rough laterally. The rod-like palpebral is preserved and restricts its contaction with the only prefrontal. The prefrontal contacts the frontal, nasal, and lacrymal, forming the anterodorsal border of the orbit. The postorbital has a robust ventral process.
The squamosal contributes to the formation of the posterior and posterolateral margins of the supratemporal fenestra, and the postodorsal margin of the infratemporal fenestra. The left and right squamosal contacts each other, separating the parietals from the occipital region in dorsal view. The quadrate has a curved shaft as in Iguanodon atherfieldensis, Camptosaurus, and Ouranosaurus . In Iguanodon bernissartensis and Probactrosaurus, it is straight.
Mandible
The mandible exposes the predentary, dentary, angular and surangular. The predentary is denticulate anteriorly. Its ventral process is very weakly bifurcated. The dentary is about 350 mm long and about 90 mm in the maximum height. The dorsal and ventral margins of the dentary are straight as in Camptosaurus, and Ouranosaurus. In Iguanodon and Probactrosaurus the anterior end of the dentary is downturned. The first dentary tooth is positioned relative to the predentary by a distance of two-tooth position as in other iguanodontids. Seven nutrient foramina are present on the anterior dentary in lateral view. The relatively large surangular foramen is present, and the angular exposes a small portion laterally.
Dentition
The maxillary teeth are smaller than the dentary ones in size. Generally the primary ridge on the lateral surface of the maxillary tooth crown is well developed, and positioned slightly posteriorly. A weakly developed secondary ridge is present between the primary ridge and well-developed the anterior shelf of the crown. The posterior shelf of the crown is weakly developed. There are more than 16 dentary teeth that become larger posteriorly. The crowns are heavily weared and the wear facets face dorsolaterally. The first and second dentary teeth are at their erupted position, with well-developed serrations. The sixth alveolus contains a functional as well as a replacement tooth. (Wang and Xu , 2001).
Carpenter & Ishida (2010) Early and “Middle” Cretaceous Iguanodonts in Time and Space Journal of Iberian Geology 36 (2) 145-164
Jinzhousaurus yangi Wang and Xu 2001
Locality
Baicaigou, Toutai, Yixian County, Liaoning, People’s Republic of China.
Horizon
Dakangpu Bed (equivalent to the Dawangzhangzi Bed), Yixian Formation
Age
early Aptian (Wang and Zhou, 2003)
Comments
Know from two specimens, the holotype with a complete, articulated skeleton, and a second disarticulated anterior portion of a skeleton (including a partially disarticulated skull). The postcrania remain undescribed and unillustrated except for the ilium described here. The ilium is long and low, with a relatively straight preacetabular process, a long, tapering postacetabular process that is abruptly truncated distally, and a moderately well developed, triangular brevis shelf. The ischial peduncle is slightly expanded onto the lateral surface. No lateral iliac crest is present.