Convolosaurus

Convolosaurus (meaning "flocking lizard" after the concentration of juvenile fossils found) is a genus of basal ornithopod dinosaur from the Twin Mountains Formation from Proctor Lake in Comanche County, Texas. The type and only species is Convolosaurus marri.[1]

Convolosaurus
Temporal range: Early Cretaceous, Aptian
125 Ma
Convolosaurus in Perot Museum
Composite skeleton in Perot Museum of Nature and Science
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Genus: Convolosaurus
Andrzejewski, Winkler & Jacobs, 2019
Type species
Convolosaurus marri
Andrzejewski, Winkler & Jacobs, 2019

Discovery and naming

Convolosaurus maps
Maps showing location of fossils

In May 1985, James "Rusty" Branch at the Proctor Lake in Comanche County, Texas, discovered a dinosaur fossil site which was among the richest from the Lower Cretaceous of North America. The Shuler Museum of Paleontology, part of the Southern Methodist University at Dallas, excavated a large number of specimens on the southeastern bank of the lake, in the Camp Quarry and the North Quarry. The discovery was in 1988 reported in the scientific literature.[2] Remains found were combined into three mounted skeletons displayed at respectively the Proctor Lake US Army Corps of Engineers Office at Proctor (based on specimen SMU 70456), the Perot Museum of Nature and Science, (a composite of specimens SMU 74087, SMU 74093 and SMU 74104), and the Fort Worth Museum of Science and History (based on specimen SMU 74663).[1] The taxon, new to science, was informally indicated as the "Proctor Lake hypsilophodontid".[3] Later it was understood that the Hypsilophodontidae are an invalid paraphyletic grouping.

In 2019, the type species Convolosaurus marri was named and described by Kate A. Andrzejewski, Dale A. Winkler and Louis Leo Jacobs. The generic name is derived from the Latin convolare, "to flock", a reference to the dense concentration of fossils. The specific name honours Dr. Ray H. Marr who has propagated the Society of Vertebrate Paleontology at the SMU.[1]

The holotype, SMU 72834, was found in a layer of the Twin Mountains Formation dating from the Aptian. It consists of a partial skeleton with skull. It preserved the cranium with the lower jaws, the vertebral column up to the twenty-third tail vertebra, the shoulder girdle, the left arm, the right humerus, the pelvis, both thighbones, both shinbones and the left calfbone. It represents a subadult individual.[1] A large amount of fossils have been referred to the species. In 2019 these amounted to 488 specimens, representing at least twenty-nine individuals, ranging from small juveniles to subadults. Almost the entire skeleton is now known.[1]

Description

Convolosaurus skull
Skull reconstruction

The holotype individual had an estimated length of between two-and-a-half and three metres. It was not yet fully grown; the adult size was considered to be unknown. Thighbones found vary between 51 and 315 millimetres in length.[1]

The describing authors established a number of distinguishing traits. One of these is an autapomorphy, a unique derived character. The premaxilla bears four teeth, which have a vertical trough on the outside.[1]

Additionally, a unique combination of traits is present that in themselves are not unique. Some of these traits are basal or symplesiomorphies. The premaxilla bears teeth. The entire upper rim of the eye socket is covered by two supraorbitals.[1]

Other traits are derived characters, indicating a position higher in the evolutionary tree. The roots of the maxillary teeth are curved. The neck vertebrae are opisthocoelous, convex at the front and concave at the rear. With the sacral vertebrae the neural spines have twice the height of the vertebral body. The rear end of the ischium is expanded into a "foot". Between the fronts of the condyles of the thighbone only a shallow groove is present. The prepubic process of the pubic bone is transversely flattened.[1]

Phylogeny

Articulated Convolosaurus
Articulated specimen SMU 70456

While initially considered a member of the Hypsilophodontidae, Convolosaurus was in 2019 placed in the Ornithopoda in a basal position, above Hypsilophodon and below Thescelosaurus in the evolutionary tree. Previous analyses had found Thescelosaurus to be more basal than Hypsilophodon but this was now reversed as the possession by Convolosaurus of two supraorbitals, shared with Thescelosaurus, indicated that Hypsilophodon had lost this trait independently.[1]

References

  1. ^ a b c d e f g h i j Andrzejewski, Kate A.; Winkler, Dale A.; Jacobs, Louis L.; Forster, Catherine (2019). "A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas". PLOS ONE. 14 (3): e0207935. doi:10.1371/journal.pone.0207935. PMC 6413910.
  2. ^ Winkler, D.A,, Murry, P.A,, Jacobs, L.L., Downs, W.R., Branch, J.R., and Trudel, P., 1988, "The Proctor Lake dinosaur locality, Lower Cretaceous of Texas", Hunteria 2(5): 1-8
  3. ^ Winkler D.A. & Murry P.A. 1989. "Paleoecology and hypsilophodontid behavior at the Proctor Lake dinosaur locality (Early Cretaceous), Texas". Geological Society of America Special Paper. 238: 55–61
Aquilarhinus

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Aralosaurini

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Canardia

Canardia is an extinct genus of aralosaurin lambeosaurine dinosaur known from the Late Cretaceous Marnes d’Auzas Formation (late Maastrichtian stage) of Toulouse, Haute-Garonne Department, southern France. The type species Canardia garonnensis was first described and named by Albert Prieto-Márquez, Fabio M. Dalla Vecchia, Rodrigo Gaete and Àngel Galobart in 2013.

Choyrodon

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Elasmaria

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Huxleysaurus

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Iguanodontia

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Jaxartosaurus

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Jeyawati

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Laiyangosaurus

Laiyangosaurus ("Laiyang lizard") is a genus of saurolophine hadrosaurid from the Late Cretaceous of China. It is known from one species, L.youngi, found in the Laiyang Basin within the province of Shandong.

Lambeosaurinae

Lambeosaurinae is a group of crested hadrosaurid dinosaurs.

Lapampasaurus

Lapampasaurus is an extinct genus of hadrosaurid known from the Late Cretaceous Allen Formation (late Campanian or early Maastrichtian stage) of La Pampa Province, Argentina. It contains a single species, Lapampasaurus cholinoi.The generic name refers to the Argentine province of La Pampa. The specific name honours the late collector José Cholino. The material includes cervical, dorsal, sacral and caudal vertebrae, the forelimb girdle, and the partial hindlimb.

Osmakasaurus

Osmakasaurus is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the lower Cretaceous period (Valanginian age) in what is now Buffalo Gap of South Dakota, United States. It is known from the Chilson Member of the Lakota Formation. This genus was named by Andrew T. McDonald in 2011 and the type species is Osmakasaurus depressus. O. depressus was previously referred to as Camptosaurus depressus, and was first described in 1909 by Charles W. Gilmore.

Pareisactus

Pareisactus (from the Greek "pareisaktos", meaning "intruder", referring to being represented as a single element among hundreds of hadrosaurid bones) is a genus of rhabdodontid ornithopod dinosaur from the Late Cretaceous Conquès Member of the Tremp Formation in the Southern Pyrenees of Spain. The type and only species is P. evrostos, known only from a single scapula.

Plesiohadros

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Sahaliyania

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Tsintaosaurini

Tsintaosaurini is a tribe of basal lambeosaurine hadrosaurs native to Eurasia. It currently contains only Tsintaosaurus (from China) and Pararhabdodon (from Spain ).Koutalisaurus, also known from late Cretaceous Spain and formerly referred to Pararhabdodon

, may also be a tsintaosaurin because of its association with the latter genus; some recent work also suggests it may indeed be referrable to Pararhabdodon.

Twin Mountains Formation

The Twin Mountains Formation, also known as the Twin Mountain Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age (Lower Cretaceous), and is notable for its dinosaur fossils. Dinosaurs from this formation include the large theropod Acrocanthosaurus, the sauropod Sauroposeidon, as well as the ornithopods Tenontosaurus and Convolosaurus. It is the lowermost unit of the lower Cretaceous, lying unconformably on Carboniferous strata. It is overlain by the Glen Rose Formation. It is the lateral equivalent of the lower part of the Antlers Formation.

Xuwulong

Xuwulong is a genus of hadrosauroid dinosaur from the Early Cretaceous period. It lived during the early Cretaceous period (Aptian-Albian age) in what is now Yujingzi Basin in the Jiuquan area, Gansu Province of northwestern China. It is known from the holotype – GSGM F00001, an articulated specimen including a complete cranium, almost complete axial skeleton, and complete left pelvic girdle from Xinminpu Group. Xuwulong was named by You Hailu, Li Daqing and Liu Weichang in 2011 and the type species is Xuwulong yueluni.

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