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A Possible New Basal Hadrosaur from the Lower Cretaceous Cedar Mountain Formation of Eastern Utah
Abstract
A new ornithopod from the Lower Cretaceous Yellow Cat Member of the Cedar Mountain Formation in eastern Utah is described. This specimen is represented by a well-preserved left ilium, preac-etabular process of the right ilium, right tibia, right metatarsal III, fused sacrum, ribs, and ossified tendons. The ilium overall resembles that of the iguanodontid Camptosaurus, which we interpret as the plesiomorphic condition, but it has the lateral process ("an-titrochanter") that characterizes hadrosaurs. The plesiomorphic character of the elements suggests a recent departure from iguanodontids, whereas the synapomorphic lateral process suggests that this taxon represents a basal hadrosaur.
... This node includes a polytomy involving Hippodraco scutodens, Sektensaurus sanjuanboscoi, and Theiophytalia kerri Brill and Carpenter 2006, as well as a branch that includes all remaining styracosternans. This latter branch includes a small clade which englobes the Salvador Formation iguanodontian, Iguanacolossus fortis, and Cedrorestes crichtoni Gilpin et al. 2007 (Node B, Figure 19B). ...
Supposed dinosaur remains were collected between 1859 and 1906 in the Lower Cretaceous Recôncavo Basin (Northeast Brazil). Since these materials remained undescribed, and most were considered lost. Recently, some of these historical specimens were rediscovered in the Natural History Museum of London, providing an opportunity to revisit them after 160 years. The specimens come from five different sites, corresponding to the Massacará (Berriasian-Barremian) and Ilhas (Valanginian-Barremian) groups. Identified bones comprise mainly isolated vertebral centra from ornithopods, sauropods, and theropods. Appendicular remains include a theropod pedal phalanx, humerus, and distal half of a left femur with elasmarian affinities. Despite their fragmentary nature, these specimens represent the earliest dinosaur bones discovered in South America, enhancing our understanding of the Cretaceous dinosaur faunas in Northeast Brazil. The dinosaur assemblage in the Recôncavo Basin resembles coeval units in Northeast Brazil, such as the Rio do Peixe Basin, where ornithopods coexist with sauropods and theropods. This study confirms the presence of ornithischian dinosaurs in Brazil based on osteological evidence, expanding their biogeographic and temporal range before the continental rifting between South America and Africa. Additionally, these findings reinforce the fossiliferous potential of Cretaceous deposits in Bahia State, which have been underexplored since their initial discoveries.
... Lateral extension of digit IV was not detected in any of the three specimens. This character seems peculiar to Sobstitute with Saurolophinae (Maryanska and Osmólska 1984), but owing to the rarity of complete appendicular skeleton elements, it may also be shared by all hadrosauroids and hadrosaurids ornithopods (Gilpin et al. 2006;Hailu et al. 2006;McDonald et al. 2014). Regardless, we point out that lateral extension of digit IV may well represent a predictable character in manus tracks. ...
Hadrosauriformes is a group of ornithopod dinosaurs with a rich and extensive Cretaceous track record. However, their rear foot (pes) anatomy is rather conservative. Thus, distinguishing different putative track producers from morphological differences is often impeded unless their identification is corroborated by stratigraphic and geographic distribution. On the contrary, the forefoot (manus) anatomy of hadrosauriform taxa reflects distinctive characters that, when preserved in tracks, may be critical for identifying their trackmakers. In this study, we examined three manus tracks preserved as sandstone casts, collected from Coniacian deposits of the Frontier Formation, southwestern Montana, USA. Tracks are assigned to Hadrosauriformes according to their steeply inclined morphology, functionally tridactyl condition, presence of hoof-like impressions and crescentic cross-sectional shape. Track preservation suggests that digit II could be extended medially, whereas movements for digits III and IV were limited. The dorsally curved digit II and III impressions indicate that these digits could be hyperextended. One track shows a short, spade-like ungual II impression, suggesting a closer affinity of its producer to hadrosauroid or hadrosaurid ornithopods. Osteological characters of the manus combined with track morphology can help with discerning different hadrosauriform producers, providing important implication for palaeoecological and palaeogeographical reconstructions.
... A sacral count of 6 þ SD is seen in Barilium dawsoni (Norman 2011), Mantellisaurus atherfieldensis (Norman 1986), Gobihadros mongoliensis (Tsogtbaatar et al. 2019), Bactrosaurus johnsoni (Godefroit et al. 1998) and Ouranosaurus nigeriensis (Bertozzo et al. 2017). A count of 5þ SD is present in Morelladon beltrani (Gasulla et al. 2015), Equijubus normani (You et al. 2003) and probably Cedroestes crichtoni (Gilpin et al. 2007), although it is difficult to determine in disarticulated material, such as that of Morelladon beltrani and Equijubus normani, if a sixth true sacral vertebra failed to fuse until late in ontogeny and did not preserve. S1 is distorted, eroded on its right lateral surface and is obscured by a sacral rib on the left. ...
A new genus and species of non-hadrosaurid hadrosauriform dinosaur, Brighstoneus simmondsi gen. et sp. nov., is described from the Lower Cretaceous Wessex Formation of the Isle of Wight. The new taxon has two autapomorphies, a nasal having a modest nasal bulla with convex sides, and primary and accessory ridges on the lingual aspect of the maxillary crown. The dentary has at least 28 alveolar positions, which is the highest number recorded in an ornithopod with non-parallel sided alveoli, creating a character combination that is unique within Iguanodontia. The hadrosauriform fauna of the Barremian–Aptian Wealden Group on both the Isle of Wight and mainland England has been represented for almost a century by just two taxa, the robust Iguanodon bernissartensis and the more gracile Mantellisaurus atherfieldensis, with referred material often being fragmentary or based on unassociated elements. This discovery increases the known hadrosauriform diversity in England and, together with recent discoveries in Spain, suggests that their diversity in the upper Wealden of Europe was considerably wider than initially realized. This find also has important implications for the validity of the Mantellisaurus atherfieldensis hypodigm, and a reassessment of existing material is suggested.
http://zoobank.org/urn:lsid:zoobank.org:pub:31F0D48F-C1DA-406E-A811-1F5937ED19F4
... The preacetabular process projects almost straight cranially, with little change in slope between the dorsal margin of the process and that of the body of the ilium dorsal to the pubic peduncle (Fig 9A and 9B). The distal end of the preacetabular process is ventrally expanded into a horizontal 'boot', as in many other styracosternans, including Iguanacolossus [4], Cedrorestes [27], Planicoxa [25], Osmakasaurus [26,73], Barilium [81], Iguanodon [61], Mantellisaurus [62], Ouranosaurus [59], Xuwulong [69], and Probactrosaurus [65]. The medial surface of the preacetabular process exhibits a mediolaterally-thickened shelf that becomes dorsoventrally deeper caudally, reaching its greatest depth dorsal to the pubic peduncle. ...
Background
Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, and one of the most completely known non-hadrosaurid iguanodontians from North America. In addition to the large holotype and paratype partial skulls, copious remains of skeletally immature individuals, including three bonebeds, have been referred to E. caroljonesa. Nevertheless, aspects of the postcranial anatomy of this taxon, particularly the pelvic girdle, have remained ambiguous due to the lack of associated postcranial material of larger, more mature individuals.
Methodology/Principal findings
Here we describe a recently discovered associated partial postcranial skeleton of a large Eolambia caroljonesa. This specimen, FMNH PR 3847, provides new anatomical data regarding the vertebral column and pelvic girdle, supplementing previous diagnoses and descriptions of E. caroljonesa. A new phylogenetic analysis incorporating information from FMNH PR 3847 places E. caroljonesa as a basal hadrosauromorph closely related to Protohadros byrdi from the Cenomanian Woodbine Formation of Texas. Histological analysis of FMNH PR 3847 reveals that it represents a subadult individual eight to nine years of age. Taphonomic analysis indicates that FMNH PR 3847 was preserved in a crevasse splay deposit, along with an unusual abundance of small crocodylomorph material.
Conclusions/Significance
FMNH PR 3847 provides a wealth of new morphological data, adding to the anatomical and systematic characterization of Eolambia caroljonesa, and histological data, revealing new information on growth history in a basal hadrosauromorph. Taphonomic characterization of FMNH PR 3847 and associated vertebrate material will allow comparison with other vertebrate localities in the Mussentuchit Member of the Cedar Mountain Formation.
Iguanodontian dinosaurs are known from Middle Jurassic to Late Cretaceous deposits worldwide and are historically important because they include the first fossils to be identified as giant extinct reptiles that later became known as dinosaurs. Due to historical taxonomic practices and the fragmentary nature of many specimens, discoveries from the 19th century were referred to Iguanodon with little appraisal, resulting in the genus becoming something of a ‘wastebasket taxon’. Reinterpretations of holotype specimens are an important step in attempting to understand the evolutionary history of iguanodontian dinosaurs. Here, we redescribe the holotype of Mantellisaurus atherfieldensis, one of the most complete British dinosaur specimens, from the Barremian/Aptian of the Isle of Wight, UK, and assess its phylogenetic position. We find that Mantellisaurus atherfieldensis is a valid taxon distinct from the genus Iguanodon based on three autapomorphies of the premaxilla, maxilla, and scapula, and resolves as an early diverging hadrosauroid styracosternan, representing an important step in the evolutionary history of the ornithopods.
A nearly complete right dentary originally noted by Mantell in 1848 is redescribed. The specimen, NHMUK 28660, was discovered in a quarry near Cuckfield, West Sussex, from the same formation as the original teeth of Iguanodon anglicus. Fresh examination reveals that NHMUK 28660 exhibits a single autapomorphy (a row of foramina extending from the ventral surface of the symphysis onto the lateral surface of the dentary) and a unique combination of characters that distinguish it from all other iguanodontian dentaries. In light of this and because I. anglicus is regarded as a nomen dubium to which additional material cannot be unambiguously referred, NHMUK 28660 is made the holotype of the new genus and species Kukufeldia tilgatensis.
Bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation are rare, forming only about 15% of the dinosaur specimens. Nevertheless, one of them was among the first dinosaurs named
from what was then the ‘’Atlantosaurus Beds’’ of Colorado. Collecting and restudy for 140 years has increased the diversity from the initial 1877 discovery to the currently valid four genera and six species, viz.,
Fruitadens haagaroum, Nanosaurus agilis, Camptosaurus dispar, C. aphanoecetes, Dryosaurus altus, and D. elderae, which we briefly review. We demonstrate that the enigmatic Nanosaurus agilis is the senior name for Drinker nisti, Othnielosaurus consors, and Othnielia rex. In addition, a new species, Dryosaurus elderae is proposed for the Dryosaurus specimens from Dinosaur National Monument that are characterized by elongate cervical verebrae and a long, low ilium among other features.
Since the late 1800s, when professional fossil hunters vied with each other to bring the largest and most complete specimens to the museum market, Utah has been one of the most fertile grounds for dinosaur discovery. Because rock from the Mesozoic era covers more than 25,000 square miles in Utah, the state is a natural museum of the great age of dinosaurs. The presence of sites such as Dinosaur National Park and the Cleveland- Lloyd Dinosaur Quarry underline Utah’s ongoing paleontological significance. There are probably more paleontologists residing and working in Utah now than at any time in the past, and the state even has an official dinosaur, the Allosaurus. Dinosaurs of Utah is an ambitious book bridging the gap between the voluminous technical literature on Utah’s Mesozoic era and the numerous publications that describe dinosaurs at the elementary level. “Utah” dinosaurs are presented here as part of the Mesozoic terrestrial ecosystems that evolved in the Colorado Plateau region and are discussed in the context of the changing landscapes, environments, and biota recorded in the geological record. More than one hundred of author Frank DeCourten’s meticulous line drawings illustrate fossil remains and various features of dinosaur anatomy, as do five stunning paintings by Carel Brest van Kempen. More than forty color landscape photographs by John Telford and Frank DeCourten show modern geologic contexts in most parts of the state and emphasize the dynamic nature of the region’s geologic history. There is also a series of detailed maps, including several new to this edition, that show the tremendous topographical shifts that occurred within the Mesozoic era from the early Triassic to the late Cretaceous periods, a span of over 175 million years. This second edition of Dinosaurs of Utah enlivens our understanding of these amazing vanished creatures by explaining them and their world to us. It moves beyond the often superficial representations that have been so prevalent and more accurately portrays the variety of dinosaurs that once roamed the region now known as Utah.
The Cedar Mountain and Dakota Formations of eastern Utah preserve two distinct biostratigraphical dinosaur faunas that record the severing of a North American-European connection, and the opening of an North American-Asian connection as the North American Plate drifted westward. The older Yell ow Cat Fauna, of the Yellow Cat through to the lower Ruby Ranch Members of the Cedar Mountain Formation, is dominated by polacanthid ankylosaurs, brachiosaurid and titanosaurid sauropods, and iguanodontids much like those of the Wealden of southern England. The polacanthid ankylosaur, the brachiosaurid sauropods and a coelurosaurid theropod indicates that the Yellow Cat Fauna is a relict of the older Late Jurassic Morrison Fauna. The younger Mussentuchit Fauna from the top of the Ruby Ranch and Mussentuchit Members and from the Dakota Formation, shows an Asian influence as characterized by a shamosaur-like ankylosaurid similar to those of Asia, the first appearance of a neoceratopsian, and the presence of the triconodont mammal, Gobiconodon. Various age dates on the faunas indicate that separation between the North America and western part of the Eurasian Plates was completed by the end of the Barremian and that a connection between North American and eastern Eurasian Plates was established no later than the early Albian.
The unarmored, hadrosaurian dinosaurs of the late Cretaceous of North America constitute an interesting group about which much has been written and many species described. A review of this literature showed many different angles of approach, and it was in part to reconcile these various descriptions and reduce them to certain comparable common factors that this monographic study was undertaken. Aside from the mere compilation of the literature of these dinosaurs, redescriptions were prepared, nearly always in the presence of the original types and such other associated material as had come to light since the species was named.
The authors also undertook as complete a morphological study of the animals as the circumstances permitted, learning what they could of the mechanics of the skeleton and teeth, the musculature and integument, the nervous system and sense organs, and the probable functions of these various parts in the living animal. They further endeavored to imagine the reconstructed creatures in their appropriate environment—physical, climatic, vegetal, and animate—and to picture them and their manner of life as animate beings of a vanished age. An account of their distribution both in time and space is given, as well as a discussion of their probable phylogeny and the trend of their evolution.