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Neuquenornis volans, a new Late Cretaceous bird (Enantiornithes: Avisauridae) from Patagonia, Argentina
Journal of Verterbrate Paleontology
Abstract
A new genus and species of Late Cretaceous (Coniancian–Santonian) birds, Neuquenornis volans, is described. This new taxon is known from a fairly complete, articulated specimen from the Río Colorado Formation of northwestern Patagonia. Synapomorphies of the humerus, radius, ulna, coracoid, femur, tibiotarsus, tarsometatarsus, and thoracic vertebrae, support its allocation to the Enantiornithes. The tarsometatarsal structure of Neuquenornis refers it to the Late Cretaceous family Avisauridae. The structure of the wing and pectoral girdle of Neuquenornis indicates that it was an active flyer, an aptitude also inferred for the El Brete enantiornithines from the Upper Cretaceous Lecho Formation of northwestern Argentina. The pedal structure of Neuquenornis and Soroavisaurus from El Brete, indicates that avisaurids were capable of perching in trees.
... Avialans from the Upper Cretaceous of Argentina are mainly represented by the Enantiornithes. The femur in these avialans also presents a trochanteric crest but differs from MAU-Pv-PH-453 by a well-developed posterior trochanter, a posteriorly projected lateral margin of the distal part of the femur, a cylindrical head connected with the shaft through a distinct neck, and, in most taxa, a fossa for the capital ligament (Chiappe 1991(Chiappe , 1996Chiappe and Calvo 1994;Sanz et al. 1995;Chiappe and Walker 2002;Sereno et al. 2002;Walker and Dyke 2009;Chiappe et al. 2020;Wang et al. 2023). The capital ligament fossa is also observed in some earlier divergent Cretaceous avialans, such as Confuciusornis (Chiappe et al. 1999), as well as in more derived taxa, which are also characterised by a patellar groove on the anterodistal surface of the femur (Chiappe 1996;Clarke and Norell 2002;Clarke 2004;Clarke et al. 2005;Bell and Chiappe 2020;Benito et al. 2022). ...
A new specimen, MAU-Pv-PH-453, comprising an isolated femur from the Plottier Formation (Coniacian-Santonian), northern Patagonia, is described here. Its characteristics, i.e., an anteriorly curved diaphysis; fused lesser and greater trochanters forming a trochanteric crest; a prominent medially directed head; and the absence of a fourth trochanter, allow us to identify it as belonging to a maniraptoran theropod. Among Patagonian maniraptorans, MAU-Pv-PH-453 shares similarities with alvarezsaurians, such as the absence of a posterior trochanter, a trochanteric shelf, and the fourth trochanter. However, in Patagonian alvarezsaurs, the lesser and greater trochanters are generally separated by a cleft. Notably, MAU-Pv-PH-453 exhibits some features seen in femora of parvicursorine alvarezsaurids, including a proximally projected trochanteric crest and an L-shaped profile in proximal view. However, MAU-Pv-PH-453 presents differences with parvicursorines, such as a knob partially separating the lesser and greater trochanters. Phylogenetically, MAU-Pv-PH-453 may have parvicursorine affinities, although its fragmentary nature might generate a bias in its phylogenetic position. Due to the lack of more diagnostic characters, MAU-Pv-PH-453 is assigned to Alvarezsauria indet. This material represents the second theropod record from the Plottier Formation and it could fill a temporal gap (between Coniacian and Santonian) in the record of Upper Cretaceous Patagonian alvarezsaurians.
... The Bajo de la Carpa Formation has yielded fossils that collectively represent a diverse and important paleobiota [30,32,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Vertebrate remains are abundant and often well-preserved, and include those of snakes (Dinilysia patagonica), lizards (Paleochelco occultato), turtles (Lomalatachelys neuquina), crocodyliforms (Notosuchus terrestris, Comahuesuchus brachybuccalis, Fig. 1 Type locality of Diuqin lechiguanae gen. ...
Unenlagiine paravians are among the most relevant Gondwanan theropod dinosaur clades for understanding the origin of birds, yet their fossil record remains incomplete, with most taxa being represented by fragmentary material and/or separated by lengthy temporal gaps, frustrating attempts to characterize unenlagiine evolution. Here we describe Diuqin lechiguanae gen. et sp. nov., a new unenlagiine taxon from the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Basin of Neuquén Province in northern Patagonia, Argentina that fills a substantial stratigraphic gap in the fossil record of these theropods. Although known only from a very incomplete postcranial skeleton, the preserved bones of Diuqin differ from corresponding elements in other unenlagiines, justifying the erection of the new taxon. Moreover, in several morphological aspects, the humerus of Diuqin appears intermediate between those of geologically older unenlagiines from the Neuquén Basin (e.g., Unenlagia spp. from the Turonian–Coniacian Portezuelo Formation) and that of the stratigraphically younger, larger-bodied Austroraptor cabazai from the Campanian–Maastrichtian Allen Formation. Consequently, the morphology of the new taxon appears to indicate a transitional stage in unenlagiine evolution. Phylogenetic analysis recovers Diuqin as a paravian with multiple plausible systematic positions, but the strongest affinity is with Unenlagiinae. The humerus of the new form exhibits subcircular punctures near its distal end that are interpreted as feeding traces most likely left by a conical-toothed crocodyliform, mammal, or theropod, the latter potentially corresponding to a megaraptorid or another unenlagiine individual. Thus, in addition to filling important morphological and temporal gaps in unenlagiine evolutionary history, the new taxon also offers information relating to the paleoecology of these theropods.
... YPM VP 59473 sheds light on the biogeography of early crown birds and their closest relatives. Although stem birds are plentiful in the Late Cretaceous of North and South America [4,5,43,47,48], the record of Mesozoic crown birds from North and South America is restricted to a number of isolated bones of unclear phylogenetic position and provenance [4,9]. ...
Background
Living birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins.
Results
Here, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon. The North American provenance of the specimen supports a cosmopolitan distribution of early crown birds, clashes with the hypothesized southern hemisphere origins of living birds, and demonstrates that crown birds and their closest relatives coexisted with non-avian dinosaurs that independently converged on avian skeletal anatomy, such as the alvarezsaurids and dromaeosaurids.
Conclusions
By revealing the ecological and biogeographic context of Cretaceous birds within or near the crown clade, the Lance Formation specimen provides new insights into the contingent nature of crown avian survival through the Cretaceous-Paleogene mass extinction and the subsequent origins of living bird diversity.
... This condition may explain the ostracods occurring in sequential localities, for example between localities within South America (such as from the Sub-Andean and Neuquén basins to Southeastern Brazil) and between South America and Africa, and eventually as far as India. Flying animals should also facilitate this dispersal in South America, as pterosaurs and birds occurred in many localities referred here, like the Yacoraite Formation, with occurrences of shorebirds and ostracods together in same outcrops ( Cónsole-Gonella et al., 2017 ;De Valais and Cónsole-Gonella, 2019 ), or in same geological units as the Adamantina Formation in Bauru Group ( Alvarenga and Nava, 2005 ;Chiappe et al., 2019 ), Anacleto, Bajo de la Carpa and Los Alamitos formations in Neuquén Group, for instance ( Alvarenga and Bonaparte, 1992 ;Chiappe and Calvo, 1994 ;Coria et al., 2002 ;Agnolin and Martinelli, 2009 ). Fossils of flying animals (pterosaurs and birds) also co-occurred with ostracods from the Campanian-Maastrichtian strata, such as the bird fossils of the Las Curtiembres Formation of the Salta Basin ( Scanferla et al., 2011 ) and pterosaur tracks of the Anacleto Formation ( Díaz-Martínez et al., 2022 ). ...
Non-marine ostracods from the Upper Cretaceous of Southern Hemisphere (South America, Africa and India) are studied and discussed for the purpose of establishing a biostratigraphy scheme and their paleogeographic distribution. The paleogeographic analysis performed here reveals ten distinct groupings of species: (1) Neuquén and Paraná basins (Brazil) are characterized by Ilyocypris riograndensis, Neuquenocypris minor, Neuquenocypris tenuipunctata, Wolburgiopsis vicinalis and Vecticypris aff. punctata; (2) Wolburgiopsis neocretacea is characteristic of Los Llanos Formation (Sub-Andean Basin, Argentina) and Neuquén (Argentina) and Parana basins (Brazil); (3) Ilyocypris triebeli is characteristic of Sub-Andean Basins (El Molino Formation, Bolivia; Los Llanos, Ciénaga del Rio Huaco formations, Argentina), and Yacoraite formations (Salta Basin); Neuquén (Argentina), Paraná and Campos basins (Brazil): Ilyocypris triebeli; (4) Neuquén (Argentina), Paraná and Santos basins (Brazil): Fossocytheridea lobulata; (5) Paraná, Santos (Brazil), Congo (R. D. Congo) basins and Lameta Formation (India): Stenocypris cylindrica; (6) Paraná (Brazil) and Congo (R. D. Congo) basins: Paracypria makawensis and Species “K 530 b” Grekoff, 1960; (7) Yacoraite Formation (Salta Basin) and Neuquén Basin (Argentina), Paraná (Brazil) and Congo (R. D. Congo) basins: Ilyocypris argentiniensis; (8) Neuquén (Argentina), Paraná (Brazil) and Congo (R. D. Congo) basins: Alicenula kwangoensis; (9) Paraná Basin (Brazil) and Lameta Formation (India): Candona chuiensis, Cypridopsis huenei, Paracandona jabalpurensis and Paralimnocythere hasuii; (10) Paraná (Brazil), Congo (R. D. Congo) basins and Lameta Formation (India): Periosocypris megistus. Other generic correlations, especially the genera Wolburgiopsis, Neuquenocypris, Virgatocypris, Altanicypris and Talycypridea, reinforce this paleobiogeographical similarities and a Campanian-Maastrichtian age to the Bauru Group (Paraná Basin) and the Kwango Series (Congo Basin), whose age was still in need of refinement.
... birds. Cumulative discoveries indicate that by the Late Cretaceous enantiornithines had evolved numerous derived skeletal morphologies in parallel to neornithines (Chiappe and Calvo, 1994;Wang et al., 2021). This suggests that skeletal anatomy does not explain the extinction of enantiornithines together with other nonneornithine dinosaurs. ...
Enantiornithines were the most diverse group of birds during the Cretaceous, comprising over half of all known species from this period. The fossil record and subsequently our knowledge of this clade is heavily skewed by the wealth of material from Lower Cretaceous deposits in China. In contrast, specimens from Upper Cretaceous deposits are rare and typically fragmentary, yet critical for understanding the extinction of this clade across the K-Pg boundary. The most complete North American Late Cretaceous enantiornithine is Mirarce eatoni, a member of the diverse clade Avisauridae. Except for Mirarce, avisaurids are known only from isolated hindlimb elements from North and South America. Here we describe three new enantiornithines from the Maastrichtian Hell Creek Formation, two of which represent new avisaurid taxa. These materials represent a substantial increase in the known diversity of Enantiornithes in the latest Cretaceous. Re-examination of material referred to Avisauridae through phylogenetic analysis provides strong support for a more exclusive Avisauridae consisting of six taxa. Exploration of the functional morphology of the avisaurid tarsometatarsus indicates potential strong constriction and raptorial attributes. The lower aspect ratio of the tarsometatarsus facilitates a more biomechanically efficient lever system which in extant birds of prey equates to lifting proportionally heavier prey items. In addition, the proportional size and distal position of the m. tibialis cranialis tubercle of the tarsometatarsus is similar to the morphology seen in extant birds of prey. Together with the deeply-grooved metatarsal trochlea facilitating robust and likely powerful pedal digits, morphologies of the hindlimb suggest avisaurids as Late Cretaceous birds of prey.
Enantiornithines were the dominant birds of the Mesozoic, but understanding of their diet is still tenuous. We introduce new data on the enantiornithine family Bohaiornithidae, famous for their large size and powerfully built teeth and claws. In tandem with previously published data, we comment on the breadth of enantiornithine ecology and potential patterns in which it evolved. Body mass, jaw mechanical advantage, finite element analysis of the jaw, and traditional morphometrics of the claws and skull are compared between bohaiornithids and living birds. We find bohaiornithids to be more ecologically diverse than any other enantiornithine family: Bohaiornis and Parabohaiornis are similar to living plant-eating birds; Longusunguis resembles raptorial carnivores; Zhouornis is similar to both fruit-eating birds and generalist feeders; and Shenqiornis and Sulcavis plausibly ate fish, plants, or a mix of both. We predict the ancestral enantiornithine bird to have been a generalist which ate a wide variety of foods. However, more quantitative data from across the enantiornithine tree is needed to refine this prediction. By the Early Cretaceous, enantiornithine birds had diversified into a variety of ecological niches like crown birds after the K-Pg extinction, adding to the evidence that traits unique to crown birds cannot completely explain their ecological success.
Important transformations of the pectoral girdle are related to the appearance of flight capabilities in the Dinosauria. Previous studies on this topic focused mainly on paravians yet recent data suggests flight evolved in dinosaurs several times, including at least once among non-avialan paravians. Thus, to fully explore the evolution of flight-related avian shoulder girdle characteristics, it is necessary to compare morphology more broadly. Here, we present information from pennaraptoran specimens preserving pectoral girdle elements, including all purportedly volant taxa, and extensively compare aspects of the shoulder joint. The results show that many pectoral girdle modifications appear during the evolution from basal pennaraptorans to paravians, including changes in the orientation of the coracoid body and the location of the articulation between the furcula and scapula. These modifications suggest a change in forelimb range of motion preceded the origin of flight in paravians. During the evolution of early avialans, additional flight adaptive transformations occur, such as the separation of the scapula and coracoid and reduction of the articular surface between these two bones, reduction in the angle between these two elements, and elongation of the coracoid. The diversity of coracoid morphologies and types of articulations joining the scapula-coracoid suggest that each early avialan lineage evolved these features in parallel as they independently evolved more refined flight capabilities. In early ornithothoracines, the orientation of the glenoid fossa and location of the acrocoracoid approaches the condition in extant birds, suggesting a greater range of motion in the flight stroke, which may represent the acquisition of improved powered flight capabilities, such as ground take-off. The formation of a new articulation between the coracoid and furcula in the Ornithuromorpha is the last step in the formation of an osseous triosseal canal, which may indicate the complete acquisition of the modern flight apparatus. These morphological transitions equipped birds with a greater range of motion, increased and more efficient muscular output and while at the same time transmitting the increased pressure being generated by ever more powerful flapping movements in such a way as to protect the organs. The driving factors and functional adaptations of many of these transitional morphologies are as yet unclear although ontogenetic transitions in forelimb function observed in extant birds provide an excellent framework through which we can explore the behavior of Mesozoic pennaraptorans.
Enantiornithines were the dominant birds of the Mesozoic, but understanding of their diet is still tenuous. We introduce new data on the enantiornithine family Bohaiornithidae, famous for their large size and powerfully built teeth and claws. In tandem with previously published data, we comment on the breadth of enantiornithine ecology and potential patterns in which it evolved. Body mass, jaw mechanical advantage, finite element analysis of the jaw, and traditional morphometrics of the claws and skull are compared between bohaiornithids and living birds. We find bohaiornithids to be more ecologically diverse than any other enantiornithine family: Bohaiornis and Parabohaiornis are similar to living plant-eating birds; Longusunguis resembles raptorial carnivores; Zhouornis is similar to both fruit-eating birds and generalist feeders; and Shenqiornis and Sulcavis plausibly ate fish, plants, or a mix of both. We predict the ancestral enantiornithine bird to have been a generalist which ate a wide variety of foods. However, more quantitative data from across the enantiornithine tree is needed to refine this prediction. By the Early Cretaceous, enantiornithine birds had diversified into a variety of ecological niches like crown birds after the K-Pg extinction, adding to the evidence that traits unique to crown birds cannot completely explain their ecological success.
The “opposite birds” Enantiornithines were the dominant birds of the Mesozoic, but our understanding of their ecology is still tenuous. In particular, diets of enantiornithine species have remained speculative until recently. While this new work has been effective at determining diet within groups of enantiornithines, diet data thus far has been too sparse to comment on larger trends in the diversity and evolution of enantiornithine ecology. We introduce new data on the enantiornithine family Bohaiornithidae, famous for their large size and strong teeth and claws. In tandem with previously-published data on the earlier-diverging pengornithids and later-diverging longipterygids, we comment on the breadth of enantiornithine ecology and potential patterns in which it evolved.
Body mass, jaw mechanical advantage, finite element analysis of the jaw, and traditional morphometrics of the claws and skull are compared between bohaiornithids and living birds. The sample size for living bird body mass is over ten times larger than previous studies on longipterygid and pengornithid diet, with implications in interpreting their results. We find bohaiornithids to be ecologically diverse: Bohaiornis and Parabohaiornis are similar to living plant-eating birds; Longusunguis resembles raptorial carnivores; Zhouornis is similar to both fruit-eating birds and generalist feeders; and Shenqiornis and Sulcavis plausibly ate fish, plants, or a mix of both. This ecological diversity is wider than any other enantiornithine family studied previously, which may be driven by strengthening of the jaw relative to other early birds. This strong jaw would allow bohaiornithids to eat harder foods than other birds at the time, but their jaws were weaker than most “strong-jawed” living birds.
With these reconstructions of diet in Bohaiornithidae, there is quantitative support for enantiornithines inhabiting nearly every trophic level. By combining these reconstructions with past dietary predictions for Longipterygidae and Pengornithidae, we predict the ancestral enantiornithine bird to have been a generalist which ate a wide variety of foods. This would suggest that the ecological diversity of enantiornithine birds represents specialisation in taking foods their ancestors were already eating, rather than many dramatic changes in diet. However, more quantitative data from across the enantiornithine tree is needed to refine this prediction. By the Early Cretaceous, enantiornithine birds had diversified into a variety of ecological niches in a similar way to crown birds after the K-Pg extinction, adding to the body of evidence that traits unique to crown birds (e.g. a toothless beak or cranial kinesis) cannot completely explain their ecological success.
Several characters of the tarsometatarsus of the Cretaceous enantiornithine birds are discussed, with emphasis on the genus Avisaurus, which was considered a non-avian theropod taxon by its authors. Two synapomorphies (metatarsal IV reduced with respect to metatarsals II and III; well-developed knob on the anterior face of metatarsal II) relate Avisaurus to the remaining enantiornithine tarsometatarsi types and support reference of this taxon within the Enantiornithes. Three other synapomorphies (laterally compressed, J-shaped metatarsal I; anterior surface of the mid-shaft of metatarsal III strongly convex transversely; strong posterior projection of the internal rim of trochlea on metatarsal III) shared by Avisaurus and a Late Cretaceous enantiornithine from northwestern Patagonia further support its avian affinities. Avisaurus and the family Avisauridae are assigned to the avian subclass Enantiornithes.
First published in 1983 to celebrate the centennial of the American Ornithologists' Union, Perspectives in Ornithology collects together a series of essays and commentaries by leading authorities about especially active areas of research on the biology of birds. Readers will find in this collection a useful overview of many major concepts and controversies in ornithology.
Numerical cladistic analysis of 73 cranial and postcranial characters has resulted in a highly corroborated hypothesis describing the phylogenetic pattern of early avian evolution. Using “non-avian theropod” dinosaurs as a comparative outgroup and root for the tree, the analysis confirmed Archaeopteryx to be the sister-group of all remaining avian taxa, or Ornithurae. This latter taxon is subdivided into two lineages, the Hesperornithiformes and the Carinatae. The carinates, in turn, were also resolved into two sister-groups, the Ichthyornithiformes and the modern birds, or Neornithes. This paper provides morphological data corroborating the divergence of the two basal clades of the Neornithes: the Palaeognathae (tinamous and ratites) and Neognathae (all other modern birds). The phylogenetic relationships of four important Cretaceous taxa were also investigated, but these fossil taxa were too fragmentary to determine their phylogenetic position unambiguously. Alexornis and Ambiortus are both carinates, but their relationships cannot be resolved in greater detail. The relationships of the Enantiornithes may lie within the Carinatae or these two taxa may be sister-groups. Gobipteryx is a neornithine and possibly the sister-group of the Palaeognathae.
This analysis indicates that major patterns of morphological change took place at the time of origin of the ancestors of the Ornithurae and the Carinatae. Ornithurine innovations included major changes throughout the skeleton, whereas those of the carinates, while substantial, were primarily restricted to the pectoral girdle and forelimb. The phylogenetic results, in conjunction with the known ages of fossil taxa, indicate that the early lineages of birds very likely arose in the Jurassic. The early cladistic events within the neornithine lineage are also more ancient than generally recognized, and may well extend back to the early Cretaceous.
A new family of theropod dinosaurs is described based on metatarsi from North America and Argentina. Because birds are theropod descendants, there are often problems in assigning isolated metatarsi to the proper group. Differences between the metatarsi of ground birds and theropods are detailed. In particular, it is shown that the length/width ratio of articulated metatarsi cannot be used to distinguish higher taxa. This new family represents the first occurrence of the same genus of theropod dinosaur from both Laurasia and Gondwanaland at the end of the Cretaceous, a time when the two supercontinents were supposedly still separate.
The anatomy of a new articulated enantiornithine bird skeleton from the Late Cretaceous of Patagonia clearly indicates a capacity for powered flight, approaching that of modern birds. Enantiornithines possess some of the synapomorphies of the Ornithurae, although they retain plesiomorphic states for many other characters, mainly in the hind limb. Such a mosaic character combination suggests a sister-group relationship between Enantiornithes and Ornithurae. Derived features of the pectoral girdle are here considered as diagnostic for a major avian clade, the Ornithopectae, comprising all known birds other than Archaeopteryx. The combination of derived and primitive traits in the fore and hind limbs and their girdles in early ornithopectines reflects mosaic evolution, with flight-related modifications of the fore limb and pectoral girdle preceding those in the hind limb and pelvic girdle.
The fossil record of cretaceous birds from Latin America comprises occurrences in Mexico, Brazil, Chile and Argentina. Three different phylods of birds have been recognized: (1) the enantiornithines, the best represented, which probably had an important radiation in South America, (2) a new group of cursorial birds, which apparently acquired flightlessness independently from all other known birds, and (3) a marine group of foot-propelled divers. South American Cretaceous terrestrial birds show no clear affinities to modern birds, otherwise well known in the Late Cretaceous of North America. The apparent absence of the latter during the Late Cretaceous in South America, combined with the radiation of the enantiornithines, may indicate that South American Cretaceous avifaunas were isolated from those of the northern hemisphere.