Qiupanykus (IPA: , meaning "claw from the Qiupa Formation") is an extinct genus of alvarezsaurid theropod from the Late Cretaceous Qiupa Formation of Henan Province, China. The type and only species is Q. zhangi, named for Shuancheng Zhang, who assisted in finding the fossils of Qiupanykus.
Discovery
The
Qiupa Formation is located in the
Tantou Basin which is in
Luanchuan County of the
Henan province in
China. Lithological correlation of the local strata has dated the Qiupa Formation to the
Late Cretaceous.
More specific analyses have suggested that the formation dates to the end of the
Maastrichtian stage, which was the final stage of the
Mesozoic Era.
This would make
Qiupanykus and its contemporaries were among the last-surviving non-avian
dinosaurs.
The Qiupa Formation preserves a wide variety of dinosaur eggs, many of which have been named as ootaxa, as well as body fossils. Alvarezsaurid remains were found near the village of Guanping in Luanchuan County and were reported in the scientific literature in 2012 and 2017, but the latter of these would not be described until the next year.
Description
Qiupanykus, like all members of
Parvicursorinae, was a relatively small dinosaur, and likely among the smallest of all the alvarezsaurs.
The authors of its description did not publish a detailed estimate of its in-life linear size, but they did provide the length of the leg bones. The femur was about long, the tibia was about long, and the longest metatarsal was about . This would give the leg, if fully extended, a total length of only about . Lü and colleagues also used the dimensions of the femur to estimate an in-life mass of based on isometric scaling methods.
Subsequent authors studying the evolution of miniaturization in alvarezsaurids gave a mass estimate of only for
Qiupanykus.
Another publication suggested a range of for possible masses.
The holotype of Qiupanykus consists of a relatively poorly-preserved postcranial skeleton that includes elements from all areas of the body. The elements present include four disarticulated cervical vertebrae, six sacrum, twenty-five with an associated chevron, part of the right ilium and ischium, part of the pubis, an articulated right hindlimb (including the femur, fibula, tibia, astragalus, calcaneum, and all three ), two phalanx bone of the foot, and three associated pedal claws. Notably, the skeleton was also found in association with several fragments of which have been assigned to the ootaxon Arriagadoolithus.
The presence of these features allowed Lü and colleagues to distinguish Qiupanykus from all other alvarezsaurs by the following combination of traits: a strong keel on the underside of the sacral vertebrae, transverse processes positioned on the midline of the centra of the caudal vertebrae at the base of the tail, a reduced knob-like pubic peduncle on the ilium, a large quadrangular crest on the tibia, the two vertebrae at the base of the tail being functionally part of the sacrum, and the presence of a small pneumatic foramen on each of the caudal vertebrae. Additionally, the ratio of the length of the femur to the tibia and the presence of an arctometatarsus suggest that Qiupanykus, like other alvarezsaurs, would have been a capable runner.
Classification
In their description of
Qiupanykus, Lü and colleagues conducted a phylogenetic analysis of
Alvarezsauroidea. This analysis, based on the dataset published by Xu Xing in 2011, included 14 taxa coded for 77 anatomical characters. Their strict consensus tree recovered
Qiupanykus at the base of
Parvicursorinae in a
polytomy with
Albertonykus,
Linhenykus,
Xixianykus, the specimen YPM 1049 (
"Ornithomimus minutus"), and a clade containing the rest of the derived parvicursorines.
Although not formally assigned to the clade Parvicursorinae in the description, this position would make it a member of Parvicursorinae
sensu Xu
et al. (2013).
In 2024, a team of authors led by Jorge Gustavo Meso and including the theropod researchers Diego Pol and Peter Makovicky published a study examining the evolutionary history of Alvarezsauria. They studied the biogeography, diversification, and functional morphology of these theropods throughout the Jurassic and Cretaceous periods. The phylogenetic analysis conducted by these authors reaffirmed the findings of Lü and colleagues. They found Qiupanykus as a member of Parvicursorinae and suggested that its appearance is reflective of a "miniaturization event" within alvarezsaurian evolution that occurred during the early-to-middle Cenomanian. An abbreviated version of the cladogram produced by Meso and colleagues is shown below.
Paleobiology
The
ootaxon found in association with
Qiupanykus, given the name
Arriagadoolithus, has been suggested by multiple authors to possibly have been laid by
Qiupanykus, even if not necessarily the individual which was preserved. Lü and colleagues estimated that in life, the egg would have been more massive than the holotype, making it unlikely that the holotype individual was the egg's parent.
However, in their study on the evolutionary trends of alvarezsauroids in 2022, Meso and colleagues observed that episodes of miniaturization in some modern birds has resulted in the evolution of species which lay very small clutches of disproportionately massive eggs. The
kiwi bird is the foremost example of this phenomenon as females famously lay a single giant egg (20% the mass of the mother) in every clutch. Eggs found in association with the larger-bodied alvarezsaur
Bonapartenykus appear to also be larger than eggs laid by other similarly-sized animals, which Meso and colleagues suggest that this phenomenon could be widespread in alvarezsaurids.
Paleoecology
Diet
No remains of the skull of
Qiupanykus are known, so no direct observations about its possible feeding habits based on the anatomy of its skull can be inferred. However, the diet of derived alvarezsauroids generally has been a topic of considerable speculation. The major diversification of parvicursorines coincided with the Cretaceous Terrestrial Revolution — a major evolutionary transition that was marked by, among other things, the spread of
angiosperms and the evolution of
eusociality in
Hymenoptera.
These simultaneous developments, coupled with the unique morphology of alvarezsaurid hands, has been used to suggest that they may have been specialized to feed on colonial insects like
ants.
[Senter, P. (2005). "Function in the stunted forelimbs of Mononykus olecranus (Theropoda), a dinosaurian anteater". Paleobiology Vol. 31, No. 3 pp. 373–381.]
Importantly for discussions of the diet of Qiupanykus, the holotype was found associated with broken dinosaur eggshells. These egg fossils were originally reported in a conference abstract as belonging to the (then unnamed) alvarezsaurid.[Kundrát M, Lü JC, Xu L, Pu HY, Shen CZ, Chang HL. 2017. First assemblage of eggshells and skeletal remains of the alvarezsaurid dinosaur from Laurasia (Upper Cretaceous, China). Journal of Vertebrate Paleontology abstracts, 145.] These eggshells, later given the name Arriagadoolithus, closely resemble elongatoolithid eggs found at Luanchuan County elsewhere in the Qiupa Formation that are attributed to . This is supported by the discovery of fossils from juvenile oviraptorosaurs in the vicinity of Qiupanykus. Also of note, the scaling methods used to estimate the full size of these eggshells, yielded a mass of about , which is larger than the estimated mass of the holotype of Qiupanykus.
These lines of evidence seem to indicate that the egg almost certainly could not have belonged to this Qiupanykus individual. Lü and colleagues use this to suggest that Qiupanykus, and possibly alvarezsaurs more generally, fed on the eggs of oviraptorosaurs and other dinosaurs. They also suggested that the large hand claws on their short arms would have assisted in breaking eggshells to feed. Additional evidence which may support this hypothesis is the discovery of eggshell fossils in the vicinity of the alvarezsaur Bonapartenykus in Patagonia.
Paleoenvironment
The
Qiupa Formation is subdivided into three sections laterally, which correspond to different outcroppings of the rock layer. Section C, in which
Qiupanykus was found, is the youngest of these sections, and this section preserves strata that correspond exactly to the
K-T boundary and the beginning of the
Cenozoic. The fossil-bearing strata of the
Qiupa Formation where
Qiupanykus was found are the lower beds of Section C. These beds are composed primarily of purple-red calcareous
mudstone and fine to medium conglomerates with interbedded calcareous mudstone. This sedimentary layer would have been deposited by a
braided river River delta that created the depositional environment necessary for
to form.
This area is also interpreted as having been part of a
littoral zone environment during the end of the Cretaceous Period.
Contemporary fauna
The Qiupa Formation is very
fossil rich, although relatively few taxa from the area have been described and named.
The largest inhabitants of the area were the non-avian
. Remains of large dinosaurs are fragmentary and indeterminate in identity, with many of them only being diagnostic to the family level. Partial remains from the area have been attributed to
ankylosauridae and
tyrannosauridae, and one of these was even named: the dubious
"Tyrannosaurus luanchuanensis".
More complete remains are known from small
.
Qiupanykus was contemporaneous with the
ornithomimid Qiupalong,
the
dromaeosauridae Luanchuanraptor,
indeterminate
troodontidae,
the
oviraptoridae Yulong,
and at least one other alvarezsaur taxon.
This environment was also home to a variety of other animals. These would have included
,
squamates (such as the genus
Tianyusaurus), small mammals, and uniquely an
edentulous enantiornithes Yuornis.
See also
-
2018 in archosaur paleontology
-
List of Asian dinosaurs
-
List of vertebrate fauna of the Maastrichtian stage
