Piksi
Encyclopedia
Piksi barbarulna is a prehistoric bird
. It lived roughly 75 million years ago in what is now Montana
, USA. Known from parts of a right wing – the humerus
, ulna
and radius
bones – the only specimens found so far are housed in the Museum of the Rockies
(collection number MOR 1113). The genus
Piksi is monotypic
at present.
The fossils were found in 1991 by Gloria Siebrecht in the Blackfeet Indian Reservation
, namely at Bob's Vacation Site locality TM-088, Glacier County. Recovered from an old stratum of the upper Two Medicine Formation
, they are probably from an individual that died in or near a small pool. It was described in 2002 by David J. Varricchio.
) and others known from living taxa such as chicken
s. In addition, there are autapomorphies hitherto unknown in other birds, in accordance with which the specific name was chosen: both the dorsal epicondyle of the humerus and the dorsal cotyla
of the ulna are consicuously large and well-developed.
Comparing the fossils' size to the wing bones of other ground birds, P. barbarulna seems to have been about as large as a Common Pheasant
, i.e. some 15 in (35–40 cm) long excluding tail, and with a wingspan of perhaps 30 in (80 cm) or somewhat less. It would thus have weighed maybe 1 – 2 pounds (some 500 g – 1 kg).
The cladistic analysis – essentially limited to characters of the elbow joint – found these to be phylogenetically quite uninformative; it was not even possible to distinguish Neornithes from Enantiornithes
. Still, it provided a valuable hint, not for the phylogeny but for the morphology
of P. barbarulna: apart from the autapomorphies, the elbow joint of the prehistoric bird is very similar to that of such little-related birds as the Little Chachalaca
, the Dusky Grouse and the prehistoric Palaeortyx gallica (all galliform
s), the Little Tinamou
(a tinamou
), and the Western Crowned Pigeon
(a columbiform
) – but not the Wood Pigeon
(another columbiform). Despite belonging to very different lineages, the living species that grouped close to it are all united by a largely terrestrial lifestyle and a heavy body with rounded wings, making for a rather weak flying ability. Thus, while P. barbarulna was almost certainly not flightless, it is most likely that it was a heavyset bird with comparatively small, rounded wings, in general body shape rather similar to a tinamou or galliform.
Nonetheless, the original description found its affinities unresolvable except that it was probably ornithothoracine
– a bird with a modern flight apparatus that permitted deep wingbeats, as opposed to the shallow, mainly downward wingbeats of Confuciusornis or Archaeopteryx
and a well-developed sternum
serving as attachment for the main flight muscles.
A later analysis by Mortimer (2010) found Piksi to be, more specifically, a neognath
of uncertain placement. Any attempt to resolve its relationship further is at present hampered by the facts that only its wing bones can be compared to other taxa, and that, as shown by the initial analysis, it would tend to group according to ecomorphology
rather than according to its phylogenetic relationship. This problem is exacerbated by the scarcity of Mesozoic
landbird remains in general and non-Enantiornithes landbirds specifically, for if there is one thing that the new analysis indicated with any certainty, it is that P. barbarulna was not a member of that group. Still, it did neither group with the paleognaths and galliforms, for which wing skeletons were available.
In conclusion, Piksi barbarulna may represent a distinct lineage of ornithothoracines without any known relatives (as of now), a basal ornithuran
, or an early modern bird – even a member of the Galloanseres, the "fowl" clade which includes, among others, chicken.
y claystone
. This was formed from sediment
s deposited during what seems to have been a rather cool phase of the Late Cretaceous
: sea level
s of the Western Interior Seaway
at least were apparently very low for Mesozoic standards, though this may also have been due to strong tectonic uplift
in the Cordilleran Overthrust Belt. The location was inland, with the Western Interior Seaway's coast at least 220 miles (350 km) away.
Judging from the stratigraphical, sedimentological and fauna
l data, environment was thus probably semi-humid, possibly (seasonally?) semi-arid
grassland
or shrubland
in a tropical or subtropical climate. The claystone apparently formed from sediment of a small floodplain
, such as an ephemeral pool.
Plentiful fauna utilized the location as habitat
. Theropods were plentiful, such as Troodon
of which a nest was found, tyrannosaurids and dromaeosaurids. Orodromeus
had an abundant presence; herds might have come the pool to drink or breed, as adults, juveniles and hatchlings were found together. Early mammal
s – marsupial
s and multituberculates – occurred in the area, as well as lizard
s. That there was a temporary though not permanent body of water is indicated by the presence of articulated frog
skeletons and the absence of fish
and other aquatic animal
s.
The lifestyle of Piksi barbarulna thus probably resembled most – among living birds – that of a mid-sized galliform or a tinamou from similar habitat. It probably fed on seeds, tubers and other plantstuffs, as well as invertebrate
s such as the land snail
s with planispiral shells found in the same rocks; as its beak
is not known, this is conjectural however. It probably flew only when threatened or to cover longer distances. The Common Pheasant, Chukar
or Yellow-necked Spurfowl
which share a similar size and habitat seem to be as close an ecological analogue among living birds as can be expected for a prehistoric species with an undetermined place in the trophic web of its time.
The taphonomy
of the remains are peculiar. While not found in articulation – as if they would have been positioned in the living bird – it is likely that these three bones, which are adjacent in life, come from the same individual bird; they were catalogued as a single specimen. Also, they were found in a rather well-worked deposit, from which both fossils smaller than the Piksi bone pieces – the mammalian teeth – and more delicate – the snail shells – were recovered. The wings of birds, especially weak-flying species, provide little sustenance but much inedible material to predators from the mid-humerus distad. At least by terrestrial predators today, they are often torn off and discarded essentially whole after eating the muscles off the proximal humerus. Thus, though it can of course not be verified anymore, the taphonomy of the type specimen is suggestive of the wing of a bird discarded by a predator and ending up, already isolated from the rest of the body, in or by the shallow pool to decompose there.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
. It lived roughly 75 million years ago in what is now Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, USA. Known from parts of a right wing – the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
and radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
bones – the only specimens found so far are housed in the Museum of the Rockies
Museum of the Rockies
The Museum of the Rockies, is located in Bozeman, Montana. The museum, originally affiliated with Montana State University in Bozeman, and now, also the Smithsonian Institution, is known for its paleontological collections, although these are not its sole focus...
(collection number MOR 1113). The genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Piksi is monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
at present.
The fossils were found in 1991 by Gloria Siebrecht in the Blackfeet Indian Reservation
Blackfeet Indian Reservation
The Blackfeet Indian Reservation or Blackfeet Nation is an Indian reservation of the Blackfeet tribe in Montana in the United States. It is located east of Glacier National Park and borders Canada to the north. Cut Bank Creek and Birch Creek make up part of its eastern and southern borders...
, namely at Bob's Vacation Site locality TM-088, Glacier County. Recovered from an old stratum of the upper Two Medicine Formation
Two Medicine Formation
The Two Medicine Formation is a geologic formation, or rock body, that was deposited between 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma , during Campanian time, and is located in northwestern Montana...
, they are probably from an individual that died in or near a small pool. It was described in 2002 by David J. Varricchio.
Description and systematics
The bones are fragmentary and represent roughly the elbow area. They show a mix of characters known since very primitive birds (such as ConfuciusornisConfuciusornis
Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...
) and others known from living taxa such as chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
s. In addition, there are autapomorphies hitherto unknown in other birds, in accordance with which the specific name was chosen: both the dorsal epicondyle of the humerus and the dorsal cotyla
Cotyla
In classical antiquity, the cotyla or cotyle was a measure of capacity among the Romans and Greeks: by the former it was also called hemina; by the latter, and or...
of the ulna are consicuously large and well-developed.
Comparing the fossils' size to the wing bones of other ground birds, P. barbarulna seems to have been about as large as a Common Pheasant
Common Pheasant
The Common Pheasant , is a bird in the pheasant family . It is native to Georgia and has been widely introduced elsewhere as a game bird. In parts of its range, namely in places where none of its relatives occur such as in Europe , it is simply known as the "pheasant"...
, i.e. some 15 in (35–40 cm) long excluding tail, and with a wingspan of perhaps 30 in (80 cm) or somewhat less. It would thus have weighed maybe 1 – 2 pounds (some 500 g – 1 kg).
The cladistic analysis – essentially limited to characters of the elbow joint – found these to be phylogenetically quite uninformative; it was not even possible to distinguish Neornithes from Enantiornithes
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
. Still, it provided a valuable hint, not for the phylogeny but for the morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of P. barbarulna: apart from the autapomorphies, the elbow joint of the prehistoric bird is very similar to that of such little-related birds as the Little Chachalaca
Little Chachalaca
The Little Chachalaca is a small bird found only in the northern part of South America. It grows to about 38 cm in length and weighs . This bird lives mostly in trees. It is a member of the Cracidae family, and is found in northern Brazil, French Guiana, Suriname, Guyana and Venezuela...
, the Dusky Grouse and the prehistoric Palaeortyx gallica (all galliform
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...
s), the Little Tinamou
Little Tinamou
The Little Tinamou, Crypturellus soui, is found in Central America and South America.-Etymology:Crypturellus is formed from three Latin or Greek words. kruptos meaning covered or hidden, oura meaning tail, and ellus meaning diminutive...
(a tinamou
Tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....
), and the Western Crowned Pigeon
Western Crowned Pigeon
The Western Crowned Pigeon, also known as the Common Crowned Pigeon or Blue Crowned Pigeon, Goura cristata, is a large, blue-grey pigeon with blue lacy crests over the head and dark blue mask feathers around its eyes. Both sexes are almost similar but males are often larger than females...
(a columbiform
Columbiformes
Columbiformes are an avian order that includes the very widespread and successful doves and pigeons, classified in the family Columbidae, and the extinct Dodo and the Rodrigues Solitaire, long classified as a second family Raphidae. 313 species, found worldwide, comprise the Columbiformes order....
) – but not the Wood Pigeon
Wood Pigeon
The Wood Pigeon is a species of bird in the Columba genus in the Columbidae family. It is a member of the dove and pigeon family Columbidae.- Distribution :...
(another columbiform). Despite belonging to very different lineages, the living species that grouped close to it are all united by a largely terrestrial lifestyle and a heavy body with rounded wings, making for a rather weak flying ability. Thus, while P. barbarulna was almost certainly not flightless, it is most likely that it was a heavyset bird with comparatively small, rounded wings, in general body shape rather similar to a tinamou or galliform.
Nonetheless, the original description found its affinities unresolvable except that it was probably ornithothoracine
Ornithothoraces
Ornithothoraces is a clade of birds which includes all enantiornithines and modern birds .The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds...
– a bird with a modern flight apparatus that permitted deep wingbeats, as opposed to the shallow, mainly downward wingbeats of Confuciusornis or Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
and a well-developed sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
serving as attachment for the main flight muscles.
A later analysis by Mortimer (2010) found Piksi to be, more specifically, a neognath
Neognathae
Neognaths are birds within the subclass Neornithes of the class Aves. The Neognathae include virtually all living birds; their sister taxon Palaeognathae contains the tinamous and the flightless ratites....
of uncertain placement. Any attempt to resolve its relationship further is at present hampered by the facts that only its wing bones can be compared to other taxa, and that, as shown by the initial analysis, it would tend to group according to ecomorphology
Ecomorphology
Ecomorphology or Ecological Morphology is studying relationships between morphological and ecological variation. There is modern emphasis on linking the two aspects of variation by measuring the performance of traits associated behaviors, and fitness outcomes of the relationships...
rather than according to its phylogenetic relationship. This problem is exacerbated by the scarcity of Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
landbird remains in general and non-Enantiornithes landbirds specifically, for if there is one thing that the new analysis indicated with any certainty, it is that P. barbarulna was not a member of that group. Still, it did neither group with the paleognaths and galliforms, for which wing skeletons were available.
In conclusion, Piksi barbarulna may represent a distinct lineage of ornithothoracines without any known relatives (as of now), a basal ornithuran
Ornithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
, or an early modern bird – even a member of the Galloanseres, the "fowl" clade which includes, among others, chicken.
Ecology
The deposit in which the bones were found was a siltSilt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
y claystone
Claystone
Claystone is a geological term used to describe a clastic sedimentary rock that is composed primarily of clay-sized particles ....
. This was formed from sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s deposited during what seems to have been a rather cool phase of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
: sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
s of the Western Interior Seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
at least were apparently very low for Mesozoic standards, though this may also have been due to strong tectonic uplift
Tectonic uplift
Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
in the Cordilleran Overthrust Belt. The location was inland, with the Western Interior Seaway's coast at least 220 miles (350 km) away.
Judging from the stratigraphical, sedimentological and fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
l data, environment was thus probably semi-humid, possibly (seasonally?) semi-arid
Semi-arid
A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...
grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
or shrubland
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
in a tropical or subtropical climate. The claystone apparently formed from sediment of a small floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
, such as an ephemeral pool.
Plentiful fauna utilized the location as habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. Theropods were plentiful, such as Troodon
Troodon
Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America...
of which a nest was found, tyrannosaurids and dromaeosaurids. Orodromeus
Orodromeus
Orodromeus is a genus of herbivorous ornithopod dinosaur from the Late Cretaceous of North America.-Discovery and naming:...
had an abundant presence; herds might have come the pool to drink or breed, as adults, juveniles and hatchlings were found together. Early mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s – marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s and multituberculates – occurred in the area, as well as lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s. That there was a temporary though not permanent body of water is indicated by the presence of articulated frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
skeletons and the absence of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and other aquatic animal
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
s.
The lifestyle of Piksi barbarulna thus probably resembled most – among living birds – that of a mid-sized galliform or a tinamou from similar habitat. It probably fed on seeds, tubers and other plantstuffs, as well as invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s such as the land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
s with planispiral shells found in the same rocks; as its beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
is not known, this is conjectural however. It probably flew only when threatened or to cover longer distances. The Common Pheasant, Chukar
Chukar
The Chukar Partridge or Chukar is a Eurasian upland gamebird in the pheasant family Phasianidae. It has been considered to form a superspecies complex along with the Rock Partridge, Philby's Partridge and Przevalski's Partridge and treated in the past as conspecific particularly with the first...
or Yellow-necked Spurfowl
Yellow-necked Spurfowl
The Yellow-necked Spurfowl or Yellow-necked Francolin is a species of bird in the Phasianidae family. It is found in Djibouti, Eritrea, Ethiopia, Kenya, Somalia, Sudan, Tanzania, and Uganda.-References:...
which share a similar size and habitat seem to be as close an ecological analogue among living birds as can be expected for a prehistoric species with an undetermined place in the trophic web of its time.
The taphonomy
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...
of the remains are peculiar. While not found in articulation – as if they would have been positioned in the living bird – it is likely that these three bones, which are adjacent in life, come from the same individual bird; they were catalogued as a single specimen. Also, they were found in a rather well-worked deposit, from which both fossils smaller than the Piksi bone pieces – the mammalian teeth – and more delicate – the snail shells – were recovered. The wings of birds, especially weak-flying species, provide little sustenance but much inedible material to predators from the mid-humerus distad. At least by terrestrial predators today, they are often torn off and discarded essentially whole after eating the muscles off the proximal humerus. Thus, though it can of course not be verified anymore, the taphonomy of the type specimen is suggestive of the wing of a bird discarded by a predator and ending up, already isolated from the rest of the body, in or by the shallow pool to decompose there.