Hesperornithoides Temporal range: Late Jurassic, ~ | |
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Reconstructed skeleton, Wyoming Dinosaur Center | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Troodontidae |
Genus: | † Hesperornithoides Hartman et al., 2019 |
Species: | †H. miessleri |
Binomial name | |
†Hesperornithoides miessleri Hartman et al., 2019 | |
Hesperornithoides (meaning "western bird form"; nicknamed "Lori") is a genus of troodontid theropod dinosaur that lived in North America during the Late Jurassic period. [1]
Although several Troodontid teeth were found, with the troodontid Koparion named in 1994, [2] [3] a well preserved skeleton wasn't found until in 2001, a field crew from the Tate Museum supervised by William Wahl unexpectedly discovered the type skeleton Hesperornithoides in Jimbo Quarry of the Morrison Formation, overlying the excavation site of Supersaurus vivianae, near Douglas, Wyoming. [1] The muddy sandstone layers of the Jimbo Quarry from which Hesperornithoides came from the middle Morrison Formation dating to the between the Oxfordian and Tithonian ages of the Upper Jurassic. [4] [5] The accidental discovery of the skeleton led to some of the fossils being damaged or lost. [1] The holotype, WYDICE-DML-001 consists of a semi-articulated partial skeleton of a subadult or adult including: the rear skull and lower jaws, hyoid bones, five cervical vertebrae, the first dorsal vertebra, twelve caudal vertebrae, a rib, chevrons, the left shoulder girdle, the right humerus, the left arm, a femur fragment, and the left and right lower legs minus the right toes. [1]
Its discovery was announced at the 2003 annual meeting of the Society of Vertebrate Paleontology and in 2005, a phylogenetic analysis including it was presented in an abstract for the Journal of Vertebrate Paleontology . [6] The same year the specimen was donated to the Big Horn Basin Foundation which in 2016 joined the Wyoming Dinosaur Center. [1] In 2019, the type species Hesperornithoides miessleri was named and described by Scott Hartman, Mickey Mortimer, William Wahl, Dean R. Lomax, Jessica Lippincott and David M. Lovelace in an article published on PeerJ . [1] The generic name is derived from the Greek Ἑσπερίς, Hesperis, "western", ὄρνις, ornis, "bird", and ~eides, "form". The specific name honours the Miessler family for its support of the project. [1]
The length of the holotype individual was in 2019 estimated at 89 cm (35 in) long. Such a body size is rather limited for a troodontid. The specimen may represent an adult or subadult individual, due to the lack of cranial and body proportions associated with juvenile individuals. Nevertheless, either assignation would not be much different; for instance, the estimated 89 cm (35 in) would become 1 m (3.3 ft). [1]
The describing authors established some derived or apomorphic traits relative to the Paraves. The jugal bone is pneumatised. The rear branch of the lacrimal bone is short, with less than 15% of the length of the descending branch, measured from the inner corner downwards. The quadrate bone is part of the outer edge of the foramen paraquadraticum. In the lower jaw the external side opening is small, with less than an eighth of the length of the jaw as a whole. On the humerus, the ridge towards the inner condyle represents more than 15% of the total distal width of the element. The third claw of the hand is about as large as the second claw. The lower inner corner of the shinbone projects to the front. [1]
The phylogenetic analysis of 2005 placed the specimen as a close relative of Sinornithoides . [6] Unpublished phylogenetic results presented at the SVP 2017 conference recovered Hesperornithoides (then known by the informal name "Lori") as a relative of Sinovenator . [7] The presence of this derived maniraptoran along with several others, such as Anchiornis and Eosinopteryx , in Jurassic sediments was a strong refutation of the temporal paradox argument used by those who oppose the consensus view that birds evolved from dinosaurs. [1]
In 2019, Hesperornithoides was placed in the Troodontidae, in a relatively basal position, in a clade with Daliansaurus , Xixiasaurus and Sinusonasus , as shown in the cladogram below: [1]
Troodontidae |
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Many large dinosaurs have been discovered in the Morrison Formation during the nineteenth century; Hesperornithoides proves that the full wealth of species had not yet been revealed. It lived in a relatively open well-watered landscape with low growths but few trees, or, lacustrine and wetland environments. [1] [8]
The layers of the Jimbo Quarry have been interpreted as a marginal lacustrine or wetland environment, representing a cyclical rise and fall in water layers. [1] Notably, the specimen preserves some keratin sheaths on the distal end of several pedal and manual unguals. [1] The relative positioning of the thoracic elements of the skeleton suggests the animal was in a resting pose and the wetland environment from which the fossil was found suggests a wetland paleoecology. [1] [4]
Apart from the Avialae, most paravian groups had only few members with some flight capability. The exceptions all showed adaptations for an arboreal lifestyle, indicating flight developed multiple times when species evolved traits and behaviours useful for climbing trees or other more vertical surfaces, such as wing-assisted incline running. [1]
Apatosaurus is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Apatosaurus lived about 152 to 151 million years ago (mya), during the late Kimmeridgian to early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus had an average length of 21–23 m (69–75 ft), and an average mass of 16.4–22.4 t. A few specimens indicate a maximum length of 11–30% greater than average and a mass of approximately 33 t.
Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discoveries of complete and articulated specimens, have helped to increase understanding about this group. Anatomical studies, particularly studies of the most primitive troodontids, like Sinovenator, demonstrate striking anatomical similarities with Archaeopteryx and primitive dromaeosaurids, and demonstrate that they are relatives comprising a clade called Paraves.
Supersaurus is a genus of diplodocid sauropod dinosaur that lived in North America during the Late Jurassic period. The type species, S. vivianae, was first discovered by Vivian Jones of Delta, Colorado, in the middle Morrison Formation of Colorado in 1972. The fossil remains came from the Brushy Basin Member of the formation, dating between 153 to 145 million years ago. It was a very large sauropod, with the WDC and BYU specimens reaching 33–35 meters (108–115 ft) in length and approximately 35–40 metric tons in body mass. A potential second species, S. lourinhanensis (Dinheirosaurus), is known from Portugal and has been dated to a similar time.
Barosaurus was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota. It is present in stratigraphic zones 2–5.
Coelurus is a genus of coelurosaurian dinosaur from the Late Jurassic period. The name means "hollow tail", referring to its hollow tail vertebrae. Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned. Only one species is currently recognized as valid: the type species, C. fragilis, described by Othniel Charles Marsh in 1879. It is known from one partial skeleton found in the Morrison Formation of Wyoming, United States. It was a small bipedal carnivore with elongate legs.
Alxasaurus is a genus of therizinosauroid theropod dinosaurs from the Early Cretaceous Bayin-Gobi Formation of Inner Mongolia.
Xinjiangovenator is a genus of coelurosaurian dinosaurs, possibly part of the group Maniraptora, which lived during the Early Cretaceous period, sometime between the Valanginian and Albian stages. The remains of Xinjiangovenator were found in the Lianmuqin Formation of Wuerho, Xinjiang, China, and were first described by Dong Zhiming in 1973. The genus is based on a single specimen, an articulated partial right lower leg, containing the tibia, three pieces of the fibula, the calcaneum and the astragalus. This specimen, IVPP V4024-2, is the holotype of the genus.
Suuwassea is a genus of dicraeosaurid sauropod dinosaur found in the Upper Jurassic strata of the Morrison Formation, located in southern Carbon County, Montana, United States. The fossil remains were recovered in a series of expeditions during a period spanning the years 1999 and 2000 and were described by J.D. Harris and Peter Dodson in 2004. They consist of a disarticulated but associated partial skeleton, including partial vertebral series and limb bones.
Variraptor is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous of France.
Koparion is a genus of small coelurosaurian theropod dinosaur, from the late Jurassic Period, of Utah. It contains the single named species Koparion douglassi which is known only from a single isolated tooth.
Tanycolagreus is a genus of coelurosaurian theropod from the Late Jurassic of North America.
Marshosaurus is a genus of medium-sized carnivorous theropod dinosaur, belonging to the Megalosauroidea, from the Late Jurassic Morrison Formation of Utah and possibly Colorado.
Maniraptoriformes is a clade of dinosaurs with pennaceous feathers and wings that contains ornithomimosaurs and maniraptorans. This group was named by Thomas Holtz, who defined it as "the most recent common ancestor of Ornithomimus and birds, and all descendants of that common ancestor."
Haplocheirus is an extinct genus of theropod dinosaur from the Middle Jurassic Shishugou Formation of Xinjiang in China. It is generally considered to be an alvarezsauroid, although some researchers have questioned this assignment. The genus contains a single species, H. sollers, which is known from a mostly complete skeleton including the skull.
Uteodon is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the late Jurassic period in what is now Uintah County, Utah. It is known from the middle of the Brushy Basin Member, Morrison Formation. The genus was named by Andrew T. McDonald in 2011 and the type species is U. aphanoecetes.
Xiaotingia is a genus of anchiornithid theropod dinosaur from Middle Jurassic or early Late Jurassic deposits of western Liaoning, China, containing a single species, Xiaotingia zhengi.
Eosinopteryx is an extinct genus of theropod dinosaurs known to the Late Jurassic epoch of China. It contains a single species, Eosinopteryx brevipenna.
Anchiornithidae is a family of eumaniraptorans which could be the basalmost family of birds in the clade Avialae. Anchiornithids have been classified at varying positions in the maniraptoran tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, members of Archaeopterygidae, or an assemblage of dinosaurs that are an evolutionary grade within Avialae or Paraves.
Fujianvenator is an extinct genus of anchiornithid theropod dinosaur from the Late Jurassic Nanyuan Formation of Fujian Province, China. The genus contains a single species, F. prodigiosus, known from a partial articulated skeleton. It is suggested to possibly have had a terrestrial or wading lifestyle.