Convolosaurus(/ˌkɒnvələˈsɔːrəs/,meaning "flocking lizard" after the concentration of juvenile fossils found) is agenusof basalornithopoddinosaurfrom theTwin Mountains FormationfromProctor LakeinComanche County, Texas.Thetypeand only species isConvolosaurus marri.[1]
| Convolosaurus | |
|---|---|
| |
| Composite skeleton inPerot Museum of Nature and Science | |
Scientific classification
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Neornithischia |
| Clade: | †Ornithopoda |
| Genus: | †Convolosaurus Andrzejewski, Winkler & Jacobs,2019 |
| Type species | |
| †Convolosaurus marri Andrzejewski, Winkler & Jacobs, 2019
| |
Discovery and naming
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In May 1985, James "Rusty" Branch at theProctor Lakein Comanche County, Texas, discovered a dinosaur fossil site which was among the richest from theLower Cretaceousof North America. TheShuler Museum of Paleontology,part of theSouthern Methodist Universityat 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), thePerot Museum of Nature and Science,(a composite of specimens SMU 74087, SMU 74093 and SMU 74104), and theFort Worth Museum of Science and History(based on specimen SMU 74663).[1]Thetaxon,new to science, was informally indicated as the "Proctor Lakehypsilophodontid".[3]Later it was understood that the Hypsilophodontidae are an invalidparaphyleticgrouping.
In 2019, thetype speciesConvolosaurus marriwas named and described by Kate A. Andrzejewski, Dale A. Winkler and Louis Leo Jacobs. The generic name is derived from theLatinconvolare,"to flock", a reference to the dense concentration of fossils. Thespecific namehonours Dr. Ray H. Marr who has propagated theSociety of Vertebrate Paleontologyat the SMU.[1]
Theholotype,SMU 72834,was found in a layer of the Twin Mountains Formation dating from theAptian.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
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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 anautapomorphy,a unique derived character. Thepremaxillabears 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 orsymplesiomorphies.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 theneural spineshave 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 thepubic boneis transversely flattened.[1]
Phylogeny
editWhile initially considered a member of the Hypsilophodontidae,Convolosauruswas in 2019 placed in the Ornithopoda in a basal position, betweenHypsilophodonandThescelosaurusin the evolutionary tree. Previous analyses had foundThescelosaurusto be more basal thanHypsilophodonbut this was now reversed asConvolosauruspossessed two supraorbitals that it shared withThescelosaurus,indicating thatHypsilophodonhad lost this trait independently.[1]
The cladogram below results from analysis by Andrzejewskiet al.,2019.[1]
References
edit- ^abcdefghijkAndrzejewski, 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.Bibcode:2019PLoSO..1407935A.doi:10.1371/journal.pone.0207935.PMC6413910.PMID30860999.
- ^Winkler, D.A; Murry, P.A; Jacobs, L.L.; Downs, W.R.; Branch, J.R.; Trudel, P. (1988). "The Proctor Lake dinosaur locality, Lower Cretaceous of Texas".Hunteria.2(5): 1–8.
- ^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.Geological Society of America Special Papers.238:55–61.doi:10.1130/SPE238-p55.ISBN0-8137-2238-1.
