Oculudentavis
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''Oculudentavis'' is an extinct
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
of uncertain
taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...
placement,Bolet et al., 2021 originally identified as an avialan dinosaur (bird, in the broad sense). It contains two known
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, ''O. khaungraae'' and ''O. naga''. Each species is known from one partial
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 preserve ...
specimen in
Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...
, which differ in several proportions. Their skulls measure in length, indicating that ''Oculudentavis'' would have been comparable in size with the modern
bee hummingbird The bee hummingbird, zunzuncito or Helena hummingbird (''Mellisuga helenae'') is a species of hummingbird, native to the island of Cuba in the Caribbean. It is the smallest known bird. The bee hummingbird feeds on nectar of flowers and bugs foun ...
if it were an avialan. Both specimens were retrieved from 99-million-year-old deposits of the Hukawng Basin in
Kachin State Kachin State (; Jingpho language, Kachin: ) is the northernmost administrative divisions of Myanmar, state of Myanmar. It is bordered by China to the north and east (Tibet Autonomous Region, Tibet and Yunnan, respectively), Shan State to the sou ...
, northern
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
. The type specimen of ''O. khaungraae'' is embroiled in controversy regarding its identity and the ethical issues surrounding the acquisition and study of
Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...
. The original description advocating for an avialan identity was published in ''
Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'', but has since then been retracted from the journal.Xing et al., 2020 retraction


Discovery and naming

''Oculudentavis khaungraae'' is known from a complete skull preserved in
Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...
, found at the Angbamo site in
Tanai Township Tanai Township () is the only township in Tanai District ( in northwestern Kachin State, northern Myanmar. The principal town is Tanai. On 30 April 2022, the Ministry of Home Affairs designated Tanai Township into a new district consisting of only ...
,
Kachin State Kachin State (; Jingpho language, Kachin: ) is the northernmost administrative divisions of Myanmar, state of Myanmar. It is bordered by China to the north and east (Tibet Autonomous Region, Tibet and Yunnan, respectively), Shan State to the sou ...
, northern
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
. The genus name ''Oculudentavis'' was chosen to include the combination of the words ''oculus'', ''dentes'', and ''avis''. These
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
words translate to "
eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...
", "
teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
", and "
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
" respectively. 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 ...
honors Khaung Ra, the woman who donated the piece of amber to the Hupoge Amber Museum for study. Presently, the
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
is cataloged as HPG-15-3 in the Hupoge Amber Museum. Later that year, an unpublished preprint attributed a second specimen (GRS-Ref-286278) to the genus. Subsequently, in 2021, it was published in the journal ''
Current Biology ''Current Biology'' is a biweekly peer-reviewed scientific journal that covers all areas of biology, especially molecular biology, cell biology, genetics, neurobiology, ecology, and evolutionary biology. The journal includes research artic ...
''. This specimen, which consists of the skull and the front portion of the torso, was found in the same mine as the holotype of ''O. khaungraae''. It was named as a different species, ''O. naga'', after the local
Naga people Nagas are various Tibeto-Burman languages, Tibeto-Burman ethnic groups native to northeastern India and northwestern Myanmar. The groups have similar cultures and traditions, and form the majority of population in the Indian state of Nagaland ...
of Myanmar (who historically played a prominent role in the amber trade).


Description

The holotype skull of ''O. khaungraae'' was in length, while the holotype skull of ''O. naga'' was in length; the length of the former was initially misreported as . The animal would have been comparable in size with the modern
bee hummingbird The bee hummingbird, zunzuncito or Helena hummingbird (''Mellisuga helenae'') is a species of hummingbird, native to the island of Cuba in the Caribbean. It is the smallest known bird. The bee hummingbird feeds on nectar of flowers and bugs foun ...
, the smallest known living dinosaur. It had a slender snout and a bulbous skull roof, as well as a long tooth row of twenty-three teeth. The
orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...
were very large and had a thick
sclerotic ring The scleral ring or sclerotic ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. The rin ...
formed from unusual spoon-shaped sclerotic ossicles. This indicates that it was likely a diurnal animal, active mostly during the day. The eyes bulge sideways according to an outwardly slanted
jugal 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 ...
(cheekbone), indicating that it did not possess
binocular vision Binocular vision is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. Th ...
. It may have had a relatively strong bite and a specialized diet of small invertebrates, based on its sharp teeth, extensively textured mouth skin, tall coronoid process, and robust, inflexible skull.Xing et al., 2020 ''Oculudentavis'' had a collection of
plesiomorphic 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, an ...
("primitive") and advanced traits compared with Mesozoic
avialans Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative defi ...
. For example, it retains separate frontal, parietal,
postorbital The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...
, and
squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...
bones, which are fused together or lost in modern birds. The extensive tooth row is also similar to non-avialan theropods. On the other hand, it lacks a separate
antorbital fenestra An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with Archosauriformes, archosauriforms, first appearing during the Triassic Period. Among Extant ...
and the bones of the snout are elongated and fused. These features are more common among modern birds. Some traits, such as the
acrodont Acrodonty (from Greek ''akros'' 'highest' + ''odont-'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be r ...
or
pleurodont Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 've ...
tooth implantation and spoon-shaped sclerotic bones are unprecedented for dinosaurs as a whole, and instead, are common among modern
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s. A patch of seemingly scaly skin occurs near the base of the skull, unusual for a bird, but consistent with a
lepidosaur The Lepidosauria (, from Greek meaning ''scaled lizards'') is a superorder or subclass of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata also includes lizards and snakes. Squamata contains over 9,000 species, making it by ...
identity. The high tooth count and apparent lack of an antorbital fenestra or
quadratojugal bone The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...
have also been used to argue against an avialan identity.Wang et al., 2020 The two specimens are distinguished by numerous characters of the skull, though the authors of the description of ''O. naga'' noted that it was "possible that at least some of these differences between the two specimens are due to a combination of individual variation, taphonomical deformation, and perhaps sexual dimorphism".


Classification

Specializations caused by the small size of ''Oculudentavis'' led to difficulties in making precise conclusions on its classification. A
phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...
in the original description supports a basal placement for ''Oculudentavis'' within Avialae, only slightly closer to modern birds than ''
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 (''archaîos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
''. This suggests that a ~50 million year
ghost lineage A ghost lineage is a hypothesized ancestor in a species lineage that has left no fossil evidence, but can still be inferred to exist or have existed because of gaps in the fossil record or genomic evidence. The process of determining a ghost line ...
exists between the
Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...
and the middle of the
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
. A small amount of most parsimonious trees instead suggest that it is an
enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cl ...
, like other birds preserved in Burmese amber. The
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
following the original description is shown below: Soon after the publication of the article, a number of paleontologists voiced skepticism on whether ''Oculudentavis'' is even a dinosaur, due to a much higher number of similarities with
squamates Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles; most members of which are commonly known as lizards, with the group also including snakes. With over 11,991 species, it is also the second-largest order ...
than with theropods. The general skull shape is considered the largest argument in favor of bird affinities, but some living lizards ('' Meroles'', ''
Anolis ''Anolis'' is a genus of anoles (), iguanian lizards in the family Dactyloidae, native to the Americas. With more than 425 species, it represents the world's most species-rich amniote tetrapod genus, although many of these have been proposed to b ...
'') and extinct reptiles (''
Avicranium ''Avicranium'' is a genus of extinct drepanosaur reptile known from the Chinle Formation of the late Triassic. The type species of ''Avicranium'' is ''Avicranium renestoi''. "''Avicranium''" is Latin for "bird Skull, cranium", in reference to its ...
'', ''
Teraterpeton ''Teraterpeton'' (meaning "wonderful creeping thing" in Greek (language), Greek) is an extinct genus of trilophosaurid archosauromorphs. It is known from a partial skeleton from the Late Triassic Wolfville Formation of Nova Scotia, described in ...
'') are known to have convergently evolved a bird-like skull shape. The usage of a bird-focused phylogenetic analysis (without considering lizards) also has been criticized. The editors of the
Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of People's Republic of China, China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian For ...
's ''Fanpu'' publication have published an editorial arguing for an interpretation of ''Oculudentavis'' as a lizard rather than an avialan. Several additional phylogenetic analyses were conducted for the description of ''O. naga'', including both of the specimens referred to the genus. Both specimens were consistently placed together in the genus ''Oculudentavis''. An analysis based on a dataset of
amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...
s found that they were squamates. Within the squamates, analyses with a more detailed dataset variously recovered ''Oculudentavis'' as the
sister group 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 (1) the
Dibamidae Dibamidae or blind skinks is a family of lizards characterized by their elongated cylindrical body and an apparent lack of limbs. Female dibamids are entirely limbless and the males retain small flap-like hind limbs, which they use to grip their ...
, (2) '' Scandensia'', and (3)
Mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...
ia, depending on whether multi-state characteristics were treated as (1) ordered or (2) unordered or if (3) molecular data was removed. A 2022 description of the Middle Jurassic lizard ''
Bellairsia ''Bellairsia'' is an extinct genus of stem-squamate known from a single species, ''Bellairsia gracilis'', from the Middle Jurassic (Bathonian) of England and Scotland. It is amongst the oldest squamates known. It was originally described in 1998 ...
'' by Tałanda ''et al''. found ''Oculudentavis'' to be a
stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
squamate, forming a weakly supported clade with ''
Huehuecuetzpalli ''Huehuecuetzpalli'' (translating to "the ancient lizard" in Nahuatl) is an extinct genus of lizard from the Early Cretaceous (late Albian) Tlayúa Formation, a Lagerstätte near Tepexi de Rodríguez, Central Mexico. One species, ''H. mixectus' ...
'' from the mid-Cretaceous of Mexico and ''Bellairsia''. The cladogram below displays the results of the phylogenetic analyses by Tałanda ''et al''.:


Paleoecology

Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...
is retrieved from the
Hukawng Valley The Hukawng Valley (; also spelt Hukaung Valley) is an isolated valley in Myanmar, roughly in area. It is located in Tanaing Township in the Myitkyina District of Kachin State in the northernmost part of the country. It has the Hukaung Valley ...
, the geographical representation of the Hukawng Basin, a large
Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
-
Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...
sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock They form when long-term subsidence ...
in
Kachin State Kachin State (; Jingpho language, Kachin: ) is the northernmost administrative divisions of Myanmar, state of Myanmar. It is bordered by China to the north and east (Tibet Autonomous Region, Tibet and Yunnan, respectively), Shan State to the sou ...
of northern
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
. The strata have undergone
folding Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure * Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Abov ...
and
faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
. The basin is considered to be a part of the West Burma block or
Burma terrane The Burma terrane or West Burma block was an isolated Gondwana-derived island arc within the Tethys Ocean. The terrane was in the upper plate of the subduction zone since early Cretaceous. It collided with Insular India during the Paleocene and co ...
, which has a debated tectonic history. The block was part of
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
during at least the Early Paleozoic, but the timing of rifting is very uncertain, with estimates ranging from the
Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
to
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
. It also is disputed whether the block had accreted onto the Asian
continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...
by the time of the amber deposition.Metcalfe, 2017 Some members of the flora and fauna have Gondwanan affinitiesPoinar, 2018 although
albanerpetontid The Albanerpetontidae (also spelled Albanerpetidae and Albanerpetonidae) are an extinct family of small amphibians, native to the Northern Hemisphere during the Mesozoic and Cenozoic. The only members of the order Allocaudata, they are thought to ...
s are more typically found in the northern continents. A recent
paleomagnetic Paleomagnetism (occasionally palaeomagnetism) is the study of prehistoric Earth's magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain ...
reconstruction finds that the Burma terrane formed an island land mass in the
Tethys Ocean The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...
during the Mid Creaceous at a
latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
around 5-10 degrees south of the equator.Westerweel et al., 2019 The amber deposits have provided a wealth of fossil flora (including mosses and bamboo-like monocots), arthropods (among many others pisaurid spiders,
onychophora Onychophora (from , , "claws"; and , , "to carry"), commonly known as velvet worms (for their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, ''Peripatus''), is a phylum of el ...
ns, dyspnoid
harvestmen The Opiliones (formerly Phalangida) are an Order (biology), order of arachnids, Common name, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered w ...
, and coccoid scale insects), and a number of vertebrates (including well-preserved three-dimensional anatomy of skeletons and feathers), that the paleoecology of the earliest Cenomanian environment has been interpreted in detail. The existence of the frog '' Electrorana limoae'' (the oldest record of frogs in amber), the snake '' Xiaophis myanmarensi'', lizard '' Cretaceogekko burmae'',Arnold & Poinar, 2008 an
albanerpetontid The Albanerpetontidae (also spelled Albanerpetidae and Albanerpetonidae) are an extinct family of small amphibians, native to the Northern Hemisphere during the Mesozoic and Cenozoic. The only members of the order Allocaudata, they are thought to ...
Matsumoto et al., 2018 and several enantiornitheans including ''
Elektorornis ''Elektorornis'' is an extinct genus of enantiornithean bird known from a partial hindlimb and a small amount of wing plumage. It contains a single species, ''Elektorornis chenguangi''. The hindlimb and feathers were preserved in a piece of 99 mi ...
'' and undescribed specimens,Angbamo, Kachín, Myanmar
in the Paleobiology Database
suggest a humid, warm, tropical forest ecosystem that contained at least some freshwater habitats. The presence of
ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
s and marine
ostracod Ostracods, or ostracodes, are a Class (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...
s suggest that some of the amber-bearing forests existed near the shore of a marine environment.Xing et al., 2018
Zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...
s in the
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...
s of the formation in which the Burmese amber has been found have been U-Pb dated to 98.8 ± 0.6 Ma, or the
Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
epoch of the earliest
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
.Shi et al., 2012, p.162


Controversy


Ethics of Burmese amber

Upon the high-profile release of the paper, which was featured on the front cover of ''
Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'', several palaeontologists renewed discussion around controversies related to Burmese amber, which were first raised in 2019. These include poor working conditions for miners (many of whom are underage), and allegations that the high-end trade of Burmese amber helps to fund the Kachin conflict, akin to
blood diamond Blood diamonds (also called conflict diamonds, brown diamonds, hot diamonds, or red diamonds) are diamonds mined in a war zone and sold to finance an insurgency, an invading army's war efforts, terrorism, or a warlord's activity. The term is u ...
s.Gammon, 2020Witton, 2020Joel, 2020 As of April 2020, 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 inte ...
has discouraged its members from collecting and studying Burmese amber due to the connections between the resource and human rights abuse.SVP, 2020aSVP, 2020b


Scientific criticism

In response to the paper's taxonomic identification of ''Oculudentavis'', critics such as Wang ''et al.'' also have noted a deliberate use of ambiguous language by the authors — in particular, the statement that ''Oculudentavis'' is "bird-like" as opposed to being a bird, and the admission that "there is a strong potential for new data to markedly alter
heir Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Offi ...
systematic conclusion". The decision of the authors to assume that ''Oculudentavis'' is a bird ''a priori'', without testing other possible positions, for their morphological description and phylogenetic analysis also was called "illogical" by Wang et al., who noted that the rejection of this hypothesis would compromise the paper's conclusions and significance. On July 22, 2020, the original ''Nature'' article describing the genus was retracted.Viglione, 2020 This retraction was motivated by the type specimen of ''O. naga'', which opposes the paper's hypothesis that the original specimen is an avialan.


See also

* Vertebrates in Burmese amber


References


Bibliography

;''Oculudentavis'' * * * * * * * * * * ;Geology and dating * * * ;Paleoecology * * * * ;Kachin conflict and its effect on paleontology * * * *


Further reading

;Bird evolution * * *


External links

;Press releases
Press release about ''Oculudentavis''
- ''
Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
''
Press release about ''Oculudentavis''
- Phys.org
Press release about ''Oculudentavis''
- ''
National Geographic ''National Geographic'' (formerly ''The National Geographic Magazine'', sometimes branded as ''Nat Geo'') is an American monthly magazine published by National Geographic Partners. The magazine was founded in 1888 as a scholarly journal, nine ...
'' ;Other links
A Tetrapod Zoology article on ''Oculudentavis,'' including some discussion on the controversy
* – ''Nature'' Video (3:32; 11 March 2020) {{Authority control Late Cretaceous reptiles of Asia Cretaceous lizards Cenomanian life Burmese amber Kachin State Fossils of Myanmar Fossil taxa described in 2020