Mahakala (dinosaur)
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''Mahakala'' ( from
संस्कृतम् Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had diffused there from the northwest in the late ...
(''Sanskrit''), named for Mahakala, one of eight protector deities ( dharmapalas) in Tibetan Buddhism) is a genus of
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 dinosaur from the Campanian-age (about 80 million years ago) Upper Cretaceous Djadokhta Formation of Ömnögovi, Mongolia. It is based on a partial skeleton found 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 an ...
. ''Mahakala'' was a small
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 ...
, and its skeleton shows features that are also found in early troodontids and
avialans Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used ...
. Despite its late appearance, it is among the most basal dromaeosaurids. Its small size, and the small size of other basal deinonychosaurians, suggests that small size appeared before flight capability in birds.


Description

''Mahakala'' was a small dromaeosaurid, measuring long and weighing . The holotype specimen, IGM 100/1033, consists of a partial skeleton including skull bones, vertebrae, limb bones, and portions of the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...
and
shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...
. Although this individual was small, comparable in size to ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'', '' Caudipteryx'', and ''
Mei Mei may refer to: Names * Mei (surname), a Chinese, Italian, Russian or Estonian family name * Mei (given name), a given name Places * Mei County, Guangdong, China, a county * Mei Pass, Guangdong, a strategic mountain pass * Mei River, Guangdong ...
'', it was close to adulthood. This genus can be distinguished from other
paravians Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the avia ...
(dromaeosaurids, troodontids, and birds) by details of the ulna,
thighbone The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
,
ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...
, and tail vertebrae. Like ''Archaeopteryx'' and derived dromaeosaurids, but unlike basal troodontids and other dromaeosaurids, the middle (third) metatarsal was not compressed, suggesting that the uncompressed version was the
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...
version. It had a typical dromaeosaurid form of the second toe, with an expanded claw.


Classification

A phylogenetic analysis performed by Turner and colleagues, who described the specimen, found ''Mahakala'' to be the most basal known dromaeosaurid. Their results, along with the small size of other theropods found at the base of
paravian Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the aviala ...
lineages, suggest that small size was not an innovation of early birds, but a common trait of early paravians; small size would have preceded flight and would not have been a special avian autapomorphy as the result of a size squeeze. Like birds, troodontids and dromaeosaurids were not small throughout their evolutionary history, and showed size increases among several different lineages. ''Mahakala'' has a combination of characteristics found among basal troodontids and birds, but lacks some that are present in more derived dromaeosaurids. A study in 2017 found that ''Mahakala'' was a member of the enigmatic,
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
Halszkaraptorinae. The cladogram below is based on the phylogenetic analysis conducted in 2017 by Cau et al. using updated data from the Theropod Working Group in their description of ''
Halszkaraptor ''Halszkaraptor'' (; meaning " Halszka's seizer") is a genus of waterfowl-like dromaeosaurid dinosaurs from Mongolia that lived during the Late Cretaceous period. It contains only one known species, ''Halszkaraptor escuilliei''. The type speci ...
''.


Paleoecology and paleobiology

The paleoenvironment of the Djadokhta Formation is interpreted as having a semiarid climate, with
sand 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, fl ...
and alluvial settings. The semiarid
steppe In physical geography, a steppe () is an ecoregion characterized by grassland plains without trees apart from those near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the temperate grasslands, ...
landscape was drained by
intermittent stream Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years.(Tzoraki et al., 2007) Such rivers drain large arid and semi-arid areas, covering approximately a third of the earth's surface. ...
s and was sometimes affected by dust and
sandstorms A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transporte ...
, and moisture was seasonal. Animals present included terrestrial turtles and crocodilians,
lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
s,
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, and a variety of dinosaurs; aquatic animals like fish were not present. The majority of the fauna was small to medium-sized. Small coelurosaurians are the most diverse dinosaurs, including fellow dromaeosaurid ''Velociraptor'', troodontids ''
Byronosaurus ''Byronosaurus'' is a genus of troodontid dinosaur from the Late Cretaceous Period of Mongolia. Discovery and naming In 1993, Michael Novacek, a member of an American Museum of Natural History expedition to the Gobi Desert, discovered the skele ...
'' and '' Saurornithoides'', oviraptorids ''
Citipati ''Citipati'' (; meaning "funeral pyre lord") is a genus of oviraptorid dinosaur that lived in Asia during the Late Cretaceous period, about 75 million to 71 million years ago. It is mainly known from the Ukhaa Tolgod locality at the Djadokhta F ...
'', '' Khaan'', and '' Oviraptor'', and alvarezsaurids '' Kol'' and ''
Shuvuuia ''Shuvuuia'' is a genus of bird-like theropod dinosaur from the late Cretaceous period of Mongolia. It is a member of the family Alvarezsauridae, small coelurosaurian dinosaurs which are characterized by short but powerful forelimbs specialized f ...
''; other dinosaurs present included
ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. ...
ns '' Protoceratops'' and '' Udanoceratops'', the hadrosaur '' Plesiohadros'', and the ankylosaurid '' Pinacosaurus''. Like other dromaeosaurids, ''Mahakala'' would have been a small active predaceous carnivore.


See also

* Timeline of dromaeosaurid research


References


External links


HTML version of "A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight"
{{Portal bar, Dinosaurs, Cretaceous Late Cretaceous dinosaurs of Asia Djadochta fauna Dromaeosaurs Fossil taxa described in 2007 Taxa named by Mark Norell