MEANING: Western claw
PERIOD: Late Jurassic
CONTINENT: Europe
Hesperonyx is an iguanodontian ornithopod dinosaur from the Late Jurassic of what is now Portugal. It was a stout bipedal herbivore, relatively small for an iguanodontian at about 3–4 m in length. Based on its arms, it appears to have lacked the ability to switch to quadrupedality seen in more derived members such as the hadrosaurs. Basal iguanodontians from Europe are rare, and the discovery of Hesperonyx is helpful in understanding their evolution and dispersal.
Abstract from paper: Iguanodontia is a diverse clade of herbivorous ornithischian dinosaurs that were speciose and abundant during the Jurassic and Cretaceous. Although the monophyly of Iguanodontia is well supported, their internal relationships have sparked heated debate due to several phylogenetic paradigm shifts. Late Jurassic basally branching iguanodontians in particular are not well understood in terms of their systematic affinities and evolutionary relevance. Their fossil record in Europe is meager compared with North America, with only a few species currently recognized. Two taxa are currently known from the Upper Jurassic of England, the basally branching styracosternan Cumnoria prestwichii and the putative dryosaurid Callovosaurus leedsi. In the Upper Jurassic of Portugal, the styracosternan Draconyx loureiroi and the dryosaurid Eousdryosaurus nanohallucis are presently the only described basally branching iguanodontians. Here we report a new species of early diverging iguanodontian from the Upper Jurassic Lourinhã Formation of western-central Portugal. The new species is clearly distinguished from all other coeval taxa by an exclusive combination of characters that include a tibia with a cnemial crest that is directed craniolaterally and a fibular condyle that is angled at 90° with respect to the proximal epiphysis, a fibula with symmetrical proximal margins, and a reduced metatarsal I. The phylogenetic relationships of the Lourinhã iguanodontian were explored using maximum parsimony and Bayesian inference. The two analyses recover the Lourinhã iguanodontian as an indeterminate dryomorphan, with more precise affinities precluded due to the current available material. Body size is estimated between 3 and 4 meters for the holotype specimen, adding to the diversity of small ornithopods already recognized in the paleoichnological record of the Lourinhã Formation.
Hesperonyx is from the Jurassic. The Jurassic is a geologic period that spanned from the end of the Triassic, 201 million y ears ago, to the beginning of the Cretaceous, 145 million years ago. It is the middle period of the Mesozoic Era. The start of the Jurassic was marked by the major Triassic-Jurassic extinction event. The end, however, has no clear boundary with the Cretaceous. By the beginning of the Jurassic, Pangea had begun rifting into two landmasses: Laurasia and Gondwana, and the climate was warm with no ice caps. Life on land was dominated by dinosaurs, and the first birds appeared, evolving from a branch of theropods. The oceans were inhabited by marine reptiles, while pterosaurs were the dominant flying vertebrates.
Hesperonyx is an ornithopod. Ornithopoda is a clade of ornithischian dinosaurs that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous. They dominated the North American continent, then spread to Asia and eventually the southern hemisphere toward the end of the Cretaceous. Their major evolutionary advantage was their batteries of teeth, which allowed them to process vegetation in an extremely efficient way. Ornithopods were a diverse group, and included the hadrosaurs, which continued to dominate until the Cretaceous–Paleogene extinction event, which wiped out all non-avian dinosaurs.