text: othnielosaurus othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago , during the late jurassic - age morrison formation of the western united states . it is named in honor of famed paleontologist othniel charles marsh , and was formerly assigned to the genus laosaurus . this genus was coined to hold fossils formerly included in othnielia , which is based on remains that may be too sparse to hold a name ; as such , it is part of decades of research to untangle the taxonomy left behind by marsh and his rival edward drinker cope from the bone wars . othnielosaurus has usually been classified as a hypsilophodont , a type of generalized small bipedal herbivore or omnivore , although recent research has called this and the existence of a distinct group of hypsilophodonts into question . description othnielosaurus is known from material from all parts of the body , including two good skeletons , although the skull is still poorly known ( note that earlier references use a multitude of names for this material , with most of them since 1977 using othnielia rex ) . othnielosaurus was a small animal , 2 meters ( 6 . 6 ft ) or less in length and 10 kilograms ( 22 lb ) or less in weight . it was a bipedal dinosaur with short forelimbs and long hindlimbs with large processes for muscle attachments . the hands were short and broad with short fingers . from the partial type skull and the skull on the possible specimen " barbara " , the head was small . it had small leaf - shaped cheek teeth ( triangular and with small ridges and denticles lining the front and back edges ) , and premaxillary teeth with less ornamentation . like several hypsilophodont or iguanodont - grade ornithopods such as hypsilophodon , thescelosaurus , and , othnielosaurus had thin plates lying along the ribs . called intercostal plates , these structures were cartilaginous in origin . classification othnielosaurus ( previously under the names laosaurus , nanosaurus , and othnielia ) has typically been regarded as a hypsilophodont ornithopod , a member of a nebulous and poorly defined group of small , running herbivorous dinosaurs . this was challenged by robert bakker et al. in 1990 . in their description of the new taxon drinker nisti , they split othnielia into two species ( o. rex and o. consors ) and placed " " as more basal than hypsilophodontids . with recent analyses suggesting a paraphyletic hypsilophodontidae , the general idea of " " as basal to other hypsilophodonts has been supported , although drinker has been controversial because virtually nothing new has been published on it since its description . other basal ornithopods have sometimes been linked to othnielosaurus , particularly , considered by at least one author to be a species of " othnielia " , o. . new studies concur with the hypothesis that othnielosaurus is more basal than other traditional hypsilophodonts , but go even farther and remove the genus from ornithopoda and the larger group , which also includes horned dinosaurs and dinosaurs . history and taxonomy o.c. marsh named several species and genera in the late 19th century that have come to be recognized as hypsilophodonts or hypsilophodont - like animals , including nanosaurus agilis ( possibly ) , " n. " rex , laosaurus celer , l. consors , and l. gracilis . this taxonomy has become very complicated , with numerous attempts at revision in the years since . in 1877 , marsh named two species of nanosaurus in separate publications , based on partial remains from the morrison formation of garden park , colorado . one paper described n. agilis , based on ypm 1913 , with remains including impressions of a dentary , and postcranial bits including an ilium , thigh bones , shin bones , and a fibula . the other paper named n. rex , a second species which marsh based on ypm 1915 ( also called 1925 in galton , 2007 ) , a complete thigh bone . he regarded both species as small ( " fox - sized " ) animals . he assigned this genus to the now - abandoned family . the next year , he named the new genus laosaurus on material collected by samuel wendell williston from como bluff , wyoming . two species were named : the type species l. celer , based on parts of eleven vertebrae ( ypm 1875 ) ; and the " smaller " l. gracilis , originally based on a back vertebra 's centrum , a caudal centrum , and part of an ulna ( review by peter galton in 1983 finds the specimen to now consist of thirteen back and eight caudal centra , and portions of both hindlimbs ) . a third species , l. consors , was established by marsh in 1894 for ypm 1882 , which consists of most of one articulated skeleton and part of at least one other individual . the skull was only partially preserved , and the fact that the vertebrae were represented only by centra suggests a partially grown individual . galton ( 1983 ) notes that much of the current mounted skeleton was restored in plaster , or had paint applied . these animals attracted little professional attention until the 1970s and 1980s , when peter galton reviewed many the " hypsilophodonts " in a series of papers . in 1973 , he and jim jensen described a partial skeleton ( byu esm 163 as of galton , 2007 ) missing the head , hands , and tail as nanosaurus ( ? ) rex , which had been damaged by other collectors prior to description . by 1977 , he had determined that nanosaurus agilis was quite different from n. rex and the new skeleton , and coined othnielia for n. rex . the 1977 reference , somewhat buried in a paper concerning the transcontinental species of dryosaurus , did not elaborate , but did assign laosaurus consors and l. gracilis to the new genus , and considered l. celer a nomen nudum . the publication of drinker further complicated matters . most recently , in 2007 galton reevaluated morrison formation ornithischians and concluded that the femur on which " nanosaurus " rex ( and by extension othnielia ) is based is not diagnostic , and reassigned the byu skeleton to laosaurus consors , which is based on more diagnostic material . as the genus laosaurus is also based on nondiagnostic material , he gave the species l. consors its own genus , othnielosaurus . as a result , in practical terms , what had been thought of as othnielia is now known as othnielosaurus consors . othnielia is not a synonym of othnielosaurus , because they are based on different specimens ; however , the skeletons that had been used to describe and depict othnielia were reassigned to othnielosaurus , leaving the older name with only the original femur . the current status for the various species is as follows : nanosaurus agilis is a possible basal ornithopod , " n. " rex ( othnielia ) is a dubious basal ornithopod , drinker nisti is its own tentatively valid taxon , l. consors is the type species for othnielosaurus , and l. celer and l. gracilis are still considered dubious . paleobiology and paleoecology othnielosaurus was one of the smaller members of the diverse morrison formation dinosaur fauna , diminutive in comparison to the giant sauropods . the morrison formation is interpreted as a semiarid environment with distinct wet and dry seasons , and flat floodplains . vegetation varied from river - lining gallery forests of conifers , tree ferns , and ferns , to fern savannas with rare trees . it has been a rich fossil hunting ground , holding fossils of green algae , fungi , mosses , horsetails , ferns , cycads , ginkgoes , and several families of conifers . other fossils discovered include bivalves , snails , ray - finned fishes , frogs , salamanders , turtles , sphenodonts , lizards , terrestrial and aquatic crocodylomorphans , several species of pterosaur , numerous dinosaur species , and early mammals such as docodonts , multituberculates , symmetrodonts , and triconodonts . such dinosaurs as the theropods ceratosaurus , allosaurus , ornitholestes , and torvosaurus , the sauropods apatosaurus , brachiosaurus , camarasaurus , and diplodocus , and the ornithischians camptosaurus , dryosaurus , and stegosaurus are known from the morrison . othnielosaurus is present in stratigraphic zones 2 - 5 . typically , othnielosaurus has been interpreted like other hypsilophodonts as a small , swift herbivore , although bakker ( 1986 ) interpreted the possibly related nanosaurus as an omnivore . this idea has had some unofficial support , but little in the formal literature ; description of more complete skull remains will be needed to test this hypothesis .