''Protohadros'' (meaning "first

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which incl ...

") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of herbivorous

ornithischian Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

( Cenomanian stage). Gary Byrd, a part-time

palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

, discovered some remains of this euornithopod (ribs and an

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

) during early 1994 at

Flower Mound Flower Mound is an incorporated town located in Denton and Tarrant counties in the U.S. state of Texas. Located northwest of Dallas and northeast of Fort Worth adjacent to Grapevine Lake, the town derives its name from a prominent mound locat ...

Denton County Denton County is located in the U.S. state of Texas. As of the 2020 census, its population was 906,422, making it the 7th-most populous county in Texas. The county seat is Denton. The county, which was named for John B. Denton, was establis ...

, north-central

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

. He informed professional palaeontologist Yuong-Nam Lee of the find, who arranged for the entire preserved fossil to be excavated. It was first reported upon in 1996 by Jason Head of the Dedman College of Humanities and Sciences,

Southern Methodist University , mottoeng = "The truth will make you free" , established = , type = Private research university , accreditation = SACS , academic_affiliations = , religious_affiliation = United Methodist Church , president = R. Gerald Turner , ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''Protohadros byrdi'' was described and named by Head in 1998. The genus name is derived from Greek πρῶτος, ''protos'', "first", en ἁδρός, ''hadros'', "thick", a reference to the fact that Head considered the species the oldest known

. The specific name honours Byrd. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

, specimen SMU 74582, of ''Protohadros'', was found in the

Woodbine Formation The Woodbine Group is a geological formation in east Texas whose strata date back to the Early to Middle Cenomanian age of the Late Cretaceous. It is the producing formation of the giant East Texas Oil Field (also known as the "Black Giant") fr ...

, which dates to the middle Cenomanian. It consists of a partial skull, pieces of ribs, a hand ungual and a

neural arch The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

. In 1997 Lee named possible tracks of ''Protohadros'' as the

ichnospecies An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

Caririchnium ''Caririchnium'' is an ichnogenus of ornithopod dinosaur footprint, belonging to either derived iguanodonts or basal hadrosauroids. It includes the species ''Caririchnium lotus'' from Lower Cretaceous Jiaguan Formation and ''C''. ''protohadrosau ...

protohadrosaurichnos''.Yuong-Nam Lee, 1997, "Bird and dinosaur footprints in the Woodbine Formation (Cenomanian), Texas", ''Cretaceous Research'' (1997) 18: 849-864 Due to the paucity of the remains much of the reconstruction of this dinosaur is speculative. The skull is about seventy centimetres long. From this Head estimated the length of the type specimen of ''Protohadros'' at seven to eight metres. He pointed out that this specimen was that of a subadult and that fully-grown individuals could have been longer. ''Protohadros'' had a massive, very deep set of lower jaws, and the snout was strongly turned down at the front, which according to Head suggested a habit of grazing on low-growing plants, rather than browsing from bushes or overhanging branches. Its diet would then have consisted of the swamp plants which grew in the delta streams in its habitat, scooped up by the broad, down-turned mouth. In some respects ''Protohadros'' was intermediate in morphology to more derived hadrosaurids. Like these it did have pleurokinesis, a cranial joint system that produced the food-grinding action, but only partially in that the quadrate at the back of the skull was still relatively immobile. ''Protohadros'' rear legs were probably longer than the front pair, and it could move on all fours or walk and run on its hind legs only. ''Protohadros'' was first described as the most basal member of the Hadrosauridae, hence its generic name. However, scientific opinion has since changed and it is now regarded as a non-hadrosaurid

iguanodontia Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', ''Dryosaurus'', ''Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck-bil ...

n, a basal member of the

Hadrosauroidea Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Europ ...

, though one closely related to the Hadrosauridae. The dinosaur's discovery conflicted with the idea that hadrosaurids evolved in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

, but its reassessment as a less- derived iguanodontian has rendered this discrepancy less problematic.

References

External links

''Protohadros'' in the Dino Directory
{{Taxonbar, from= Q1976657, from2= Q3924310 Iguanodonts Late Cretaceous dinosaurs of North America Fossil taxa described in 1998 Paleontology in Texas