''Hesperornithoides'' (meaning "western bird form"; nicknamed "Lori") is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
troodontid theropod 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 ...
that lived in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
during the
Late Jurassic period.
Discovery
Although several Troodontid teeth were found, with the troodontid ''
Koparion'' named in 1994, a well preserved skeleton wasn't found until in 2001, a field crew from the
Tate Museum
Tate is an institution that houses, in a network of four art galleries, the United Kingdom's national collection of British art, and international modern and contemporary art. It is not a government institution, but its main sponsor is the U ...
supervised by William Wahl unexpectedly discovered the type skeleton ''Hesperornithoides'' in Jimbo Quarry of the
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...
, overlying the excavation site of ''
Supersaurus
''Supersaurus'' (meaning "super lizard") is a genus of diplodocid Sauropoda, 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, Colorad ...
vivianae'', near
Douglas, Wyoming
Douglas is a city in Converse County, Wyoming, United States. The population was 6,120 at the 2010 census. It is the county seat of Converse County and the home of the Wyoming State Fair.
History
Douglas was platted in 1886 when the Wyoming C ...
.
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
In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...
ages of the
Upper Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987.
In European lithostratigraphy, the name ...
.
[Trujillo, K., Chamberlain, K., & Strickland, A. (2006). Oxfordian Park: U/Pb ages from SHRIMP analysis for the Upper Jurassic Morrison Formation of southeastern Wyoming with implications for biostratigraphic correlations. ''Journal of Vertebrate Paleontology'', ''26'', 1-152.][Lovelace, D.M. (2006). "An Upper Jurassic Morrison Formation fire-induced debris flow: Taphonomy and paleoenvironment of a sauropod (Sauropoda: ''Supersaurus vivianae'') locality, east-central Wyoming." pp. 47–56 ''in'' Foster, J.R., and Lucas, S.G., eds. (2006), ''Paleontology and geology of the Upper Jurassic Morrison Formation''. New Mexico Museum of Natural History and Science Bulletin 36.] The accidental discovery of the skeleton led to some of the fossils being damaged or lost.
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 several ...
, WYDICE-DML-001 consists of a semi-articulated partial skeleton of a subadult or adult including: the rear skull and lower jaws,
hyoid bone
The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebr ...
s, 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.
Its discovery was announced at the 2003 annual meeting of the
Society of Vertebrate Paleontology
The Society of Vertebrate Paleontology (SVP) is a professional organization that was founded in the United States in 1940 to advance the science of vertebrate paleontology around the world.
Mission and Activities
SVP has about 2,300 members inter ...
and in 2005, a
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analysis including it was presented in an abstract for the ''
Journal of Vertebrate Paleontology''.
The same year the specimen was donated to the Big Horn Basin Foundation which in 2016 joined the
Wyoming Dinosaur Center
The Wyoming Dinosaur Center is located in Thermopolis, Wyoming and is one of the few dinosaur museums in the world to have excavation sites within driving distance. The museum displays the Thermopolis Specimen of ''Archaeopteryx'', which is the onl ...
.
In 2019, 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 specimen ...
''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
''PeerJ'' is an open access peer-reviewed scientific mega journal covering research in the biological and medical sciences. It is published by a company of the same name that was co-founded by CEO Jason Hoyt (formerly at Mendeley) and publisher Pet ...
''.
The generic name is derived from the Greek Ἑσπερίς, Hesperis, "western", ὄρνις, ''ornis'', "bird", and ~eides, "form". The
specific name Specific name may refer to:
* in Database management systems, a system-assigned name that is unique within a particular database
In taxonomy, either of these two meanings, each with its own set of rules:
* Specific name (botany), the two-part (bino ...
honours the Miessler family for its support of the project.
Description
![Hesperornithoides skull block](https://upload.wikimedia.org/wikipedia/commons/3/3e/Hesperornithoides_skull_block.png)
The length of the holotype individual was in 2019 estimated at 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 would become .
The describing authors established some derived or
apomorphic
In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...
traits relative to the
Paraves. The
jugal bone
The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species.
Anatomy ...
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 humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
, 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.
Classification
The phylogenetic analysis of 2005 placed the specimen as a close relative of ''
Sinornithoides''.
[Hartman, S., Lovelace, D., and Wahl, W., (2005). "Phylogenetic assessment of a maniraptoran from the Morrison Formation." ''Journal of Vertebrate Paleontology'', 25, Supplement to No. 3, pp. 67A–68A http://www.bhbfonline.org/AboutUs/Lori.pdf ] Unpublished phylogenetic results presented at the SVP 2017 conference recovered ''Hesperornithoides'' (then known by the informal name "Lori") as a relative of ''
Sinovenator''.
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.
In 2019, ''Hesperornithoides'' was placed in the
Troodontidae, in a relatively basal position, in a
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
with ''
Daliansaurus
''Daliansaurus'' (meaning "Dalian reptile") is a genus of small troodontid theropod dinosaur, measuring approximately long, from the Early Cretaceous of China. It contains a single species, ''D. liaoningensis'', named in 2017 by Shen and colleag ...
'', ''
Xixiasaurus'' and ''
Sinusonasus
''Sinusonasus'' is a genus of dinosaurs from the Early Cretaceous Period, recovered from the Yixian Formation. It lived in what is now the Liaoning Province of China. ''Sinusonasus'' was a theropod, specifically a troodontid dinosaur.
The type ...
'', as shown in the cladogram below:
Palaeobiology
![Hesperornithoides](https://upload.wikimedia.org/wikipedia/commons/2/2b/Hesperornithoides.png)
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
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
environments.
The layers of the Jimbo Quarry have been interpreted as a
marginal lacustrine or
wetland
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
environment, representing a cyclical rise and fall in water layers.
Notably, the specimen preserves some keratin sheaths on the distal end of several pedal and manual unguals.
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.
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
Wing-assisted incline running (abbreviated as "WAIR") is a running behavior observed in living birds as well as a model proposed to explain the evolution of avian flight. WAIR allows birds to run up steep or vertical inclines by flapping their win ...
.
See also
*
Timeline of troodontid research
This timeline of troodontid research is a chronological listing of events in the History of paleontology, history of paleontology focused on the troodontids, a group of bird-like theropod dinosaurs including animals like ''Troodon''. Troodontid re ...
*
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...
*
2019 in paleontology
Flora Plants
Fungi
Paleomycological research
* Fossil sporocarps indistinguishable from sporocarps of members of the extant genus ''Stemonitis'' are described from the Cretaceous amber from Myanmar by Rikkinen, Grimaldi & Schmidt (2019).
* ...
References
{{Taxonbar, from=Q3301304
Late Jurassic dinosaurs of North America
Troodontids
Dinosaurs of the Morrison Formation
Paleontology in Wyoming
Fossil taxa described in 2019