''Hulsanpes'' ( meaning " Khulsan foot") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

halszkaraptorine Halszkaraptorinae is a basal ("primitive") subfamily of Dromaeosauridae (or possibly Unenlagiidae) that includes the enigmatic genera ''Halszkaraptor'', ''Natovenator'', ''Mahakala'', and ''Hulsanpes''. Halszkaraptorines are definitively known o ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaurs 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 the ...

that lived during the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

in what is now the

Barun Goyot Formation The Barun Goyot Formation (also known as Baruungoyot Formation or West Goyot Formation) is a geological formation dating to the Late Cretaceous Period. It is located within and is widely represented in the Gobi Desert Basin, in the Ömnögovi Pr ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million ...

, about 75-72 million years ago. The remains were found in 1970 and formally described in 1982 by Halszka Osmólska, who noted that the genus is represented by an immature individual. ''Hulsanpes'' represents the first record of the basal

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus Genus ( plural genera ) is a taxonomic rank used in the biological classifica ...

Halszkaraptorinae.

History of discovery

The first

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

remains of ''Hulsanpes'' were discovered in 1970 during the third Polish-Mongolian expedition at Khulsan in the

Gobi Desert The Gobi Desert ( Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast a ...

. Twelve years later, 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 specim ...

, ''Hulsanpes perlei'', was named and described by the Polish

palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

Halszka Osmólska in

1982 Events January * January 1 – In Malaysia and Singapore, clocks are adjusted to the same time zone, UTC+8 (GMT+8.00). * January 13 – Air Florida Flight 90 crashes shortly after takeoff into the 14th Street Bridge in Washington, D.C ...

. ''Hulsanpes'' is based on 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 seve ...

fossil

specimen Specimen may refer to: Science and technology * Sample (material), a limited quantity of something which is intended to be similar to and represent a larger amount * Biological specimen or biospecimen, an organic specimen held by a biorepository f ...

ZPAL MgD-I/173, uncovered in a sandstone layer of the

, dating from the Late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

(roughly 72

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago ...

). It consists of a partial

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

fragment and the right

metatarsus The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

composed by the second, third and fourth metatarsals and three pedal

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

from an apparently immature individual. Osmólska mentioned the braincase as preserved in the holotype but this element was never described. Based on the unusual morphology of the metatarsus and second phalanges she concluded that ''Hulsanpes'' represented a deinonychosaur taxon, but due to the lack of more material, she tentatively classified the genus as a dromaeosaurid taxon. In an etymological aspect, the generic name, ''Hulsanpes'', can be translated as "Khulsan pes" and is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

ized name of the type locality Khulsan and the Latin ''pēs'' meaning "foot" (''Hulsan'' + ''pēs''). The specific name, ''perlei'', is in honour to the veteran Mongolian paleontologist

Altangerel Perle Altangerel Perle (born 1945) is a Mongolian palaeontologist. He is employed at the National University of Mongolia. He has described species such as ''Goyocephale lattimorei'', '' Achillobator giganticus'' and '' Erlikosaurus andrewsi''. He has ...

Description

The holotype specimen is represented by a very small immature individual and therefore all the available data is somewhat limited. The roughly textured bones are indicators of an early stage of life, probably a post-

hatchling In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar to ...

chick. The genus itself can be distinguished in having the contact area of metatarsal III and IV straight in a frontal view and the lower end of metatarsal IV projected to the lower lateral side. Overall, the preserved right

is a gracile and compact element with the three main metatarsals only lacking the first one, in all metatarsals the upper end is slightly eroded. Although compact, the third metatarsal is not pinched at the upper end, indicating that the metatarsus was not arctometatarsalian. Metatarsals II, III and IV are similar in length (, and respectively), although the third one is the longest. There are three pedal

preserved but only one being complete. The first phalanx of metatarsal III is very eroded missing most of its lower part but preserving the upper one; it remains articulated to the metatarsal. The first phalanx of metatarsal II is complete but the second one is severely damaged, lacking most of the lower region, however, it is articulated to the first phalanx. The partial

is a small element, measuring just in length, it is embedded in a small portion of the sandstone layer. In general, the morphology is very complex and has an irregular shape. Based on comparisons with other maniraptorans, the preserved portion can be identified as the right inner side of the prootic- opisthotic bones in the braincase.

Classification

When first described in 1982, Osmólska tentatively placed ''Hulsanpes'' within the

Dromaeosauridae Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

. Several features of the specimen were, according to Osmólska, too "primitive" for it to be a genuine bird taxon such as the lack of fusion of the metatarsals except in the lower region but this might partly be due to the young age of the individual specimen. Although its juvenile nature is reminiscent of a miniature individual of ''

Velociraptor ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaur that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in th ...

'', and though these traits are

plesiomorph In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, ...

ic, it might still belong to another, non-avian, maniraptoran lineage besides Dromaeosauridae. A 2004 phylogeny of Dromaeosauridae recovered ''Hulsanpes'' as a dromaeosaurid (due to a coding error for ''

Sinovenator ''Sinovenator'' (meaning "Chinese hunter") is a genus of troodontid dinosaur from China. It is from the early Cretaceous Period. Discovery and naming Two specimens of a troodontid were described in 2002. They are both housed in the Institu ...

''), but Agnolin and Novas in 2013 assigned it to Averaptora ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'' based on the fact that the extremely gracile metatarsals are similar to Avialae and metatarsal III interpreted to be pinched at the upper region. This latter statement has been proven to be incorrect though. After several inconsistencies surrounding the placement of the genus, in

2017 File:2017 Events Collage V2.png, From top left, clockwise: The War Against ISIS at the Battle of Mosul (2016-2017); aftermath of the Manchester Arena bombing; The Solar eclipse of August 21, 2017 ("Great American Eclipse"); North Korea tests a s ...

during the description of '' Halszkaraptor'' a new clade, the Halszkaraptorinae, was coined by Cau and colleagues, containing the new genus ''Halszkaraptor'' and its close relatives which were identified as being the long enigmatic ''Hulsanpes'' and ''

Mahakala Mahākāla is a deity common to Hinduism and Tantric Buddhism. In Buddhism, Mahākāla is regarded as the sacred '' Dharmapāla'' ("Protector of the Dharma"), while in Hinduism, Mahākāla is a fierce manifestation of the Hindu god Shiva and th ...

''. The analysis showed that the Halszkaraptorinae was the most primitive known dromaeosaurid group, slightly related to

unenlagiines Unenlagiinae is a subfamily of long-snouted paravian theropods. They are traditionally considered to be members of Dromaeosauridae, though some authors place them into their own family, Unenlagiidae, alongside the subfamily Halszkaraptorinae. Un ...

. ''Hulsanpes'' occupied a derived position within the Halszkaraptorinae as the

sister species In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of ''Mahakala''. The cladogram below is based on the results obtained in the phylogenetic analysis performed during the description using updated data from the Theropod Working Group:

Paleobiology

''Hulsanpes'' has been re-classified as a halszkaraptorine taxon, updating various aspects about the life-style of these animals. ''Hulsanpes'' had a similar life-style to those of the modern-day sawbills or waterfowls, spending most of their time in aquatic environments (such as rivers) using fore and hindlimb-assisted

swimming Swimming is the self-propulsion of a person through water, or other liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs and the body to achieve hydrodynamic thrust that r ...

. But like all dinosaurs, they come up onto land to reproduce and laid eggs in terrestrial

nests A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic materi ...

. However, it appears to be that ''Hulsanpes'' may have been more terrestrial based on the holotype metatarsus, which features adaptations for a more subcursorial life-style, supporting the diversification within this subfamily.

Paleoecology

The holotype specimen was recovered from the

at the type location of the formation, the Khulsan locality. This formation is interpreted to date back to the Middle-Late Campanian stage of the Late Cretaceous period, about 72 million to 75 million years ago. Most of the environments present consisted of large

rivers A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

with other

water bodies A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ...

, and prominent

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

-like terrains. Here, ''Hulsanpes'' shared their habitat with diverse dinosaurs such as ''

Bagaceratops ''Bagaceratops'' (meaning "small-horned face") is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 72 to 71 million years ago. ''Bagaceratops'' remains have been reported from the Barun Goyot Form ...

'', ''

Gobipteryx ''Gobipteryx'' (from Gobi eferring to the Gobi Desert where it was first discovered and Greek pteryx “wing”) is a genus of prehistoric bird from the Campanian Age of the Late Cretaceous Period.Elżanowski, A. (1974): Preliminary note on t ...

'', '' Parvicursor'', ''

Saichania ''Saichania'' (Mongolian meaning "beautiful one") is a genus of herbivorous ankylosaurid dinosaur from the Late Cretaceous period of Mongolia and China. The first fossils of ''Saichania'' were found in the early 1970s in Mongolia. In 1977 the ...

'', '' Tarchia'' and '' Tylocephale''. The locomotory specializations of ''Hulsanpes'' may suggest a reduced source competition with other species in the formation.

References