5th International Paleontological Congress – Paris, 9th-13th July 2018 (1 Viewer)

Delphine Angst & Eric Buffetaut, 2018

Ontogenetic change in the giant bird Gastornis

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/IPC5_Abstract_Book.pdf pg. 167

The genus Gastornis includes large terrestrial herbivorous birds known from Europe, North America and China during the Paleocene and the Eocene. The Thanetian Mont-de-Berru site in north-eastern France has yielded remains referred to two species, G. parisiensis and G. russelli. While many specimens of G. parisiensis are known, including post-cranial as well as cranial material, the species G. russelli Martin, 1992 is based on a single left tarsometatarsus (the holotype), and a referred fragmentary beak, both in the collections of the Paris Natural History Museum. Martin (1992) briefly described this beak and provided a drawing, in which the missing tip is reconstructed as forming a distinct hook, for which there is no factual evidence.
A new preparation and reexamination of this beak leads to a new interpretation. The specimen (R2583) corresponds to the fused premaxillae and maxillae showing a very large naris which is much larger and anteriorly placed than the naris observed on the known Gastornis beaks, in which it is clearly very small and posterodorsally located. This significant difference at first sight challenges the attribution of this beak to Gastornis. However, an examination of the skull bones of both juvenile and adult specimens of Sylviornis neocaledoniae shows that in this bird both the position and size of the naris changed during ontogeny, from a large and anterior naris in juveniles to a small and posterodorsal naris in the adults. Assuming that the same kind of allometric growth occurred in Gastornis, we interpret the beak R2583 as a juvenile, not an adult, specimen.
The attribution of this beak to a juvenile therefore challenges the referral of this specimen to the species Gastornis russelli. The holotype tarsometatarsus of G. russelli belonged to an adult, to judge from the complete fusion of its bony components. The beak is too large to consider it as a juvenile of G. russelli, but is consistent with G. parisiensis, the other Gastornis species known from the same site. Therefore, we suggest that specimen R2583 belongs to a juvenile of G. parisiensis. The type tarsometatarsus of G. russelli differs from that of G. parisiensis only in its smaller size. A revision is required to establish if G. russelli is a valid species or should be included in G. parisiensis, in which case the small size of the tarsometatarsus currently attributed to G. russelli would imply significant size variation or sexual dimorphism in G. parisiensis.

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Fred

What is a long neck?

Christine Böhmer, Olivia Plateau, Raphaël Cornette & Eric Buffetaut, 2018

What is a long neck? The effects of scaling relationships between skeletal dimensions and body size in living and fossils birds

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 168

Birds constitute a classic example of modern vertebrates with highly variable neck lengths ranging from short necks in songbirds to extremely long, serpentine necks in herons. Since this includes a wide array of small to very large species, this raises the question of how neck length relates to body size. Furthermore, neck length is not necessarily an indicator of the number of cervical vertebrae since a few elongated vertebrae may form an equally long neck as do many short vertebrae.
We sampled the skeletons of a diversity of bird species (including fossil taxa) and compiled quantitative data of body proportions. We tested the length of the cervical vertebrae in relation to body size in order to reveal if the avian neck is subject to allometry. Next, we analyzed the relationship between vertebral length and the length of other body parts such as pelvic limb bones. This enables to reveal trends in proportion between the neck and other parts of the skeleton.
Our results show that neck length shows an isometric scaling in relation to body size in the majority of taxa. Pelagic specialists and birds that forage below or around the water surface tend to have a relatively long neck, whereas many birds that forage on the ground have a relatively short neck. The length of the central vertebra shows moderate negative allometry in relation to femur length and tibiotarsus length. It scales with strong negative allometry in relation to tarsometatarsus length. The vertebral length decreases relatively as tarsometatarsus length increases.
Variation in neck length appears to be related to functional differentiation in terms of foraging. The neck in birds serves many demanding tasks and is of particular importance for feeding. The association between vertebral length and tarsometatarsus length may support a reported trade-off between quantitative design (i.e., relative volumes of bone) and maximum rates of avian posthatching growth. Since the tarsometatarsus bone is one of the longest and fastest growing in the body of birds, this pattern of development may limit the relative growth of the vertebrae resulting in shorter vertebrae.
The present study, as the first large scale analysis of the scaling patterns of the cervical vertebral column in living and extinct birds, provides new information on the function and development of the avian neck. Next, we aim to include non-avian theropods in order to reveal if the growth trade-off occurred after the theropod-bird transition.

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Fred

How large was the Pleistocene 'giant ostrich' of China?

Eric Buffetaut & Delphine Angst, 2018

How large was the Pleistocene 'giant ostrich' of China? Mass estimates for Struthio anderssoni and their implications

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 169

Large ostrich eggs have been known from Quaternary deposits (especially Pleistocene loess) in northern China since the 1890s. The egg-based taxon Struthio anderssoni was erected for them by Lowe in 1931, and a few skeletal remains have also been referred to it. The large sizes of these eggs and bones, exceeding those of the living Struthio camelus, have often been emphasized, and the term ?giant ostrich' has frequently been used. However, no quantitative estimates have so far been provided for Struthio anderssoni. We have estimated the mass of that bird using two distinct approaches. A mass estimate of 270 kg, which is considerably above the maximum weight for S. camelus (mass range: 100-156 kg for males, 90-110 kg for females), has been obtained from the minimum circumference of an incomplete femur from the Late Pleistocene of the Upper Cave at Zhoukoudian, using Campbell and Marcus's method. Using Hoyt's equations based on the transverse and longitudinal diameters of the shell, we have estimated the volume and mass of eggs from various Pleistocene localities in northern China, on the basis of measurements available in the literature. Volumes range from 1542.9 cm3 to 2399.9 cm3 and masses from 1.7 kg to 2.6 kg. This again is more than the values for wild S. camelus (volume: 1082 - 1425 cm3; mass: 1.1 - 1.5 kg). Dyke and Kaiser's equations linking egg mass to femur length and body mass of the female bird indicate a femur length range of 304.8 - 371.9 mm (mean: 338.35; range in S. camelus: 249 -330 mm, mean: 289.5) and a mass range of 176.9 ?350.8 kg (mean: 263.85 kg). A S. anderssoni femur from the Upper Cave had a length of 355 mm, within the estimated range, and the above-mentioned femur-based mass estimate of 270 kg is also within the range of masses estimated from egg measurements. Our results show that S. anderssoni was indeed a giant ostrich, with a mass that could be more than 150 % that of S. camelus, and within the range of other very large extinct birds, such as the giant moa, Dinornis robustus. Since S. anderssoni lived in northern China during cold periods of the Pleistocene, its large size could be interpreted as an adaptation to a cold climate, following Bergmann's rule. However, very large ostriches from the Miocene (e.g. Ukraine) and the Early Pleistocene (e.g. Hungary, Georgia, Tanzania) did not live under cold climates, which suggests that other reasons must be sought for the very large size of S. anderssoni.

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Fred

An exceptional bone bed of Enantiornithine birds

Luis Chiappe, William Nava, Agustin Martinelli, Ryan Tucker & Herculano Alvarenga, 2018

An exceptional bone bed of Enantiornithine birds in the late Cretaceous of Brazil

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 170

Despite abundant discoveries of Mesozoic birds in the last few decades, knowledge of their evolution during the last 20 million years of the Cretaceous remains scant. However, this time interval is vital for understanding the rise of modern birds as well as the pattern of avifaunal turnover during the Cretaceous-Paleogene transition. We report on a remarkably rich site (William's Quarry; discovered in 2004 by WN) contained in the Upper Cretaceous Adamantina Formation (Bauru Group) of southeastern Brazil (Presidente Prudente, western São Paulo State). Excavations at this site have produced hundreds of partially articulated and isolated remains of small to medium-sized enantiornithine birds concentrated in a very small area (approximately 6 m²) of red-pink fluvial sandstones and claystones. The remains include numerous postcranial elements as well as many skull portions (isolated rostra, mandibles, and crania) preserved in three-dimensions and representing at least three taxa. This site constitutes the most abundant avian Mesozoic locality in the Americas and the richest site of Late Cretaceous age in the world. As such, this site provides key information for contrasting hypotheses of avian diversification during the K-Pg transition and the earliest divergences of modern birds. Together with other Late Cretaceous localities from Gondwana, the information revealed at this site indicates a clear abundance of enantiornithine bird species during the ~80-70 mya interval. Such a record is difficult to reconcile with hypotheses arguing that modern (neornithine) birds originated in the southern hemisphere during the Late Cretaceous.

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Life history of the basal pygostylian Confuciusornis sanctus

Anusuya Chinsamy-Turan, Luis Chiappe & Jesús Marugan-lobón, 2018

Life history of the basal pygostylian, Confuciusornis sanctus

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 171

Hundreds of specimens of Confuciusornis sanctus have been recovered from the Early Cretaceous Jehol Group of Northeastern China. Here we investigate the bone microstructure of 22 long bones sampled from ten different sized Confuciusornis specimens to assess life history patterns of this basal pygostylian bird. Analysis of the bone histology of the various bones revealed differences in the histological structure of
their bone walls. By comparing the histology of the Confuciusornis bones to ontogenetic changes in modern bird bone histology we were able to separate the Confuciusornis material into different age classes representing, juvenile, subadult and adult sizes. When the histology ”age-assigned” specimens were plotted on a graph obtained from ”morphometric” analyses, the histology correlated with different sized birds. Our findings suggest that Confuciusornis took several years to attain skeletal maturity and that the ”clusters” reflect ontogeny i.e. ”age cohorts” rather than sexual dimorphism or interspecific differences. This supports the earlier hypothesis that like Archaeopteryx and several other basal birds, Confuciusornis experienced a slower growth rate than most extant birds. Considering recent identification of a reproductive female Confuciusornis specimen (without tail feathers), we have been able to ascertain when sexual dimorphic traits became evident in the species. Our findings suggest that males exhibited long tail feathers early in ontogeny, suggesting that these early birds were able to reproduce well before they were adult body size.

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Selection on avian ecology structured the dawn of the crown bird radiation

Daniel Field, Antoine Bercovici, Jacob Berv, Regan Dunn, Tyler Lyson, David FastovskyVivi Vajda & Jacques Gauthier, 2018

Selection on avian ecology structured the dawn of the crown bird radiation

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 172

The fossil record and recent molecular phylogenies support an extraordinary early Cenozoic radiation of crown birds (Neornithes) following the Cretaceous-Paleogene (K–Pg) mass extinction. However, questions remain regarding the mechanisms underlying the survival of the deepest lineages within crown birds across the K–Pg boundary, particularly since this global catastrophe eliminated even the closest stem group relatives of Neornithes. Here, ancestral state reconstructions of neornithine ecology reveal a strong bias toward taxa exhibiting predominantly non-arboreal lifestyles across the K–Pg, with multiple convergent transitions toward predominantly arboreal ecologies later in the Paleocene and Eocene. By contrast, ecomorphological inferences indicate predominantly arboreal lifestyles among enantiornithines, the most diverse and widespread Mesozoic avialans. Global paleobotanical and palynological data show that the K–Pg Chicxulub impact triggered widespread destruction of forests. We suggest that ecological filtering due to the temporary loss of significant plant cover across the K–Pg boundary selected against any flying dinosaurs (Avialae) committed to arboreal ecologies, resulting in a predominantly non-arboreal postextinction neornithine avifauna composed of total-clade Palaeognathae, Galloanserae, and terrestrial totalclade Neoaves that rapidly diversified into the broad range of avian ecologies familiar today. The explanation proposed here provides a unifying hypothesis for the K–Pg-associated mass extinction of arboreal stem birds, as well as for the post-K–Pg radiation of arboreal crown birds. It also provides a baseline hypothesis to be further refined pending the discovery of additional neornithine fossils from the Latest Cretaceous and earliest Paleogene.

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Fred

New Zealand’s Platydyptes

Katie Matts & R. Ewan Fordyce, 2018

New Zealand’s Platydyptes old penguins with a new view: significance of the genus

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 174

New Zealand is home to a magnificent record of fossil penguins (Sphenisciformes). Uniquely adapted to aquatic life, their dense, ballasting bones predispose penguins to fossilise. Platydyptes, first described by B.J. Marples in 1952, is one of the most crownward of the stem (basal) penguins and one of a few described Late Oligocene genera. This position within penguin history shows Platydyptes as a precursor for the ”modern” or crown radiation of penguins, with importance for understanding functional morphology. Despite the potential value of the genus, the last published work on Platydyptes was by Simpson in 1971, on taxonomy but not including phylogeny or function. Platydyptes penguins are robust, adding to their preservation potential; while there is some variation in size, the three currently described species P. novaezealandiae, P. amiesi, and P. marplesi can be considered medium-sized ancient penguins (the smallest described species P. marplesi is closer in size to a king penguin, ˜95cm height, than to a crested penguin, ˜50-70cm height). A redescription of the genus is planned, to include new potentially diagnostic features from the P. novaezealandiae holotype, and the description of undescribed specimens from Hakataramea. For instance, a semi-articulated partial skeleton from the Otekaike Limestone of Hakataramea (OU 22804) varies from other Platydyptes. This fossil preserves the taxonomically diagnostic humerus as well as rarer elements such as the mandible, quadrate, a semi-complete sternum, and pelvis. While showing characteristics of Platydyptes, OU 22804 does not fall into the currently described species. Further ahead a phylogenetic study is also planned.

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Fred

Pygostyle formation in early birds

Jingmai O’Connor & Zhonghe Zhou, 2018

Pygostyle formation in early birds

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 175

The pygostyle, a compound element formed through fusion of the distal caudal vertebrae, is one of the most definitive characteristics of living birds but is absent in the most basal known taxon, the Late Jurassic Archaeopteryx whose elongate tail resembles that of its non-avian dinosaurian close relatives. In the Early Cretaceous, birds with bony tails even longer than that of Archaeopteryx co-exist with the basalmost pygostylians, birds whose abbreviated tails end in a pygostyle. With no obvious transition apparent from the fossil record, the evolution of this compound element has remained largely mysterious. The vast collections of Early Cretaceous birds from the Jehol deposits in northeastern China are dominated by subadult material and these fossils shed light on the formation and development of the pygostyle in individual lineages of early birds. Most informative are numerous specimens of young juvenile enantiornithines, which in particular show unusual allometric growth in the tail with this part of the skeleton being proportionately much longer in the youngest individuals. Osteohistological sampling and advanced scanning technologies applied to juvenile and subadult specimens further elucidates details of the formation of this element in individual lineages. The greater overall length of the pygostyle in the Confuciusornithiformes and Enantiornithes appears to correspond with a greater number of co-ossified vertebrae relative to the shorter pygostyles present in the Sapeornithiformes and Ornithuromorpha. Apparent differences in the number of caudal vertebrae forming the pygostyle in these clades may suggest multiple originations of this element or that the primitive pygostylian condition consisted of a pygostyle formed by at least twice the number of vertebrae observed in extant neornithines. As in living birds, the formation of the pygostyle is a post- hatching event but the time it takes for complete fusion to occur varies between basal lineages.

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Fred

Laser-Stimulated Fluorescence reveals preserved soft tissues

Michael Pittman, Thomas G. Kaye, Xiaoli Wang, Xiaoting Zheng, Scott A Hartman, Guillermo Navalón & Xing Xu, 2018

Laser-Stimulated Fluorescence reveals preserved soft tissues which unravel the complexity of avian flight evolution

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 175

Fossils of exceptionally preserved theropod dinosaurs have pushed back the origins of important anatomies related to avian flight. The unique anatomical configurations they possess indicate a highly diverse road to modern flight capabilities. Whilst less flight proficient lineages went extinct, rare evidence exists of unusual adaptive trends towards improved flight proficiency. For example, our work with Laser-Stimulated Fluorescence produced a quantitative body outline of the basal bird Anchiornis, from the extinct anchiornithid clade. This revealed a narrow, extended wing form with undifferentiated feathering. Additional data is therefore paramount to understanding the full range of early avian flight development. Using Laser-Stimulated Fluorescence we discovered that the short-tailed early bird Confuciusornis (Pygostylia: Confuciusornithidae) had extensively muscled shoulders in contrast to reduced breast muscles. This evolved along the confuciusornithid lineage through incremental development of the deltopectoral crest of the humerus in the absence of a keeled sternum - opposite to the keel-dominated configuration of modern birds.
We provide the first direct soft tissue evidence of an alternative musculoskeletal framework among early pygostylian birds, which led to novel, improved flight proficiency. These findings indicate that the transition to more modern crown birds during the Cretaceous included the elimination of lineages that had differentially improved flight proficiency, suggesting that this process of elimination was more nuanced than previously supposed. Such parallelism evident here presents a valuable opportunity to further explore the role of parallel evolution in shaping the development of avian flight.

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Fred

Multiple origins of powered flight among paravian theropod dinosaurs

Michael Pittman, Rui Pei, Pablo A. Goloboff, T. Alexander Dececchi, Michael B. Habib, Thomas G. Kaye, Hans C. E. Larsson, Mark A. Norell, Stephen Brusatte & Xing Xu. 2018

Multiple origins of powered flight among paravian theropod dinosaurs: constraints from new phylogenetic, aerodynamic and anatomical data

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 177

The evolution of birds from paravian theropod dinosaurs is a classic evolutionary radiation. Unfortunately, there is a lack of consensus on the geneology of birds and their very closest relatives. This has made it difficult to understand the timing and sequence of evolutionary changes along the line of descent to modern birds, particularly those involved with flight. We have addressed this issue through a larger, more resolved phylogeny produced by analysing a revised dataset using an automated pipeline of analysis tailored to large morphological datasets. The enhanced automation and newly developed techniques of this analytical pipeline should greatly increase access to more in-depth analyses using parsimony as a criterion for phylogenetic inference. We corroborate the grouping of dromaeosaurids and troodontids (Deinonychosauria) as the sister group to birds. We also recover the basal ‘Jianchang’ paravians as the basalmost avialans (Anchiornithidae e.g. Anchiornis), instead of troodontids. Wing loading and specific lift (theoretical and in vivo based criteria devised to discern volant from flightless avians) were calculated for taxa with vanned feathers and interpreted in the context of the improved phylogeny. This provided upper and lower bounds for flappingbased locomotor evolution, especially powered flight. Our results show that theropod powered flight appears to be limited to paravians and originated multiple times. The dromaeosaurids Microraptor and Rahonavis are especially strong non-avialan candidates for this behaviour.

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Fred

A new caudipterid dinosaur

Rui Qiu, Xiaolin Wang, Qiang Wang, Ning Li, Jialiang Zhang & Yiyun Ma, 2018

A new caudipterid dinosaur from the Lower Cretaceous Jehol Group of China

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 178

Caudipteridae is a primitive group of oviraptorsauria only found in the Early Cretaceous Jehol Group of western Liaoning, China. It is one of the first true feathered dinosaur that avian-like pennaceous remiges and rectrices present. Its discovery reduces both skeletal and soft tissue gap between small theropod dinosaurs and birds. Here we describe a new caudipterid species from the Lower Cretaceous Yixian Formation from Yixian County, Liaoning Province. This turkey-sized specimen is an adult individual based on fusion between neural arch and centrum on all preserved vertebrae. It is assigned to caudipteridae by a combination of following characters: relative short tail with few caudals; humerus about 50% of the femoral length; the metacarpal I shorter than half length of the metacarpal II; slightly concave proximal articular surface of manus phalanx I-1; proximal portion of metatarsal III compressed transversely. While it can be distinguished from known caudipterids Caudipteryx and Similicaudipteryx by small oval pleurocoel near the dorsal margin of the centrum, scapula shorter than the humerus, ulna subequal to humerus, relative small radiale angle, extremely short metacarpal I less than 40% length of metacarpal II. Phylogenetic analyses using both coelurosaurian and oviraptorosaurid matrix support the new species belong to caudipteridae. The new species exhibits a mosaic morphology. The features of its manus, such as slender digit III with full phalanges, ligament pit dorsally located, are more similar to other oviraptorosaurids rather than caudipteridae. We conclude that the manus of oviraptorosaurids show a complex evolution, different group has its own evolutionary trend. Its radiale gives new understanding of evolution of radiale angle along coelurosauria.

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Fred

Soaring like a vulture in the Cretaceous

Francisco Serrano & Luis Chiappe, 2018

Soaring like a vulture in the Cretaceous: Sapeornis and the evolution of energy-saving aerial strategies in early birds

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 179

nterpretations of the avian fossil record suggest that strategies to save cost of flight might have evolved by the Early Cretaceous, long before the origin of modern birds. In this study, we use a combination of computational modelling and morphofunctional analyses to infer the flight properties of the raven-sized, 125-million-years-old bird Sapeornis chaoyangensis. Specifically, lever theory as applied to the well-developed DPC of the humerus of this bird, and multivariate and computational models of modern neornithines, evidence that S. chaoyangensis would have had energetic limitations for prolonged flapping flights and suggest a flight behaviour comparable to that of modern soarers. Our results also indicate that the high-lift wings of S. chaoyangensis would have enabled this bird to soar in continental thermals. Aerodynamic modelling (slow gliding speeds with low lift-to-drag ratios and circling pattern during soaring) further evidences that S. chaoyangensis would have had an aerial behaviour similar to thermal soarers such as vultures and storks. Combined to known paleobiological evidences of herbivory and grasping feet, our results indicate that S. chaoyangensis was a thermal soarer with an ecology similar to that of living South American screamers. In summary, our results provide evidence documenting that thermal soaring, a strategy to reduce aerial costs observed in many medium-to-large modern birds, had evolved by at least 125 Ma among large early birds. This conclusion highlights once again the significant breadth of ecological, functional and behavioral diversity reached during the earliest avian evolutionary radiation of the Mesozoic.

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Fred

Bone fusions in manus and pelvis in the early evolution of birds

Min Wang, Zhiheng Li & Zhonghe Zhou, 2018

Bone fusions in manus and pelvis in the early evolution of birds in light of new discovery

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 180

The skeleton of birds show remarkable modifications pertaining to powered flight. The most noticeable feature is bone fusion in the hand, feet and pelvis, which enhances the strength and rigidity of the body. However, the historical origin of avian bone fusions remains allusive. This is largely because of the lack of transitional fossils and developmental studies on modern birds. Recently, we reported one of the earliest avian records that has a fully fused alular-major metacarpals and pelvis from the 120 million years old horizon from the Jehol Biota, northeast China. We traced the degree of fusion in manus and pelvis across Paravian phylogeny, and demonstrate that these features evolved independently in non-avian theropods, Enantiornithes, and Ornithuromorpha. The fusions of these bones are rare in known non-avian theropods and Early Cretaceous birds, but are well established in Late Cretaceous and crown birds, revealing a complicated evolution trajectory not appreciated previously. We suggest that the developments of bone fusion were polymorphic close to the origin of birds, resulting in the varying degrees of fusion in Paraves. However, that development polymorphism appear to be fundamentally restricted along the line to modern birds by the Late Cretaceous, where all birds have a completely fused manus and pelvis, suggesting developmental plasticity. Alternatively, the degree of bone fusion in this primitive bird may have been induced by modifications in genes or developmental paths (e.g., Hox). Future studies and fossil discoveries are required to clarify these hypotheses and pinpoint the developmental pathways involving the bone fusions in early avian evolution through to their modern pattern.

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Fred

New Ichthyornis specimens

Juan Benito, Bhart-Anjan Bhullar, David Burnham, Laura Wilson & Daniel Field, 2018

New Ichthyornis specimens: shedding new light on a classic taxon

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 181

The Late Cretaceous toothed bird Ichthyornis dispar was one of the first known Mesozoic avialans, and is recognized today as one of the closest relatives of crown birds among Mesozoic stem birds. As such, the skeletal morphology of Ichthyornis may be more representative of the ancestral condition of crown birds than that of any other known Mesozoic avialan, and its study has crucial implications for understanding the origins and early evolution of crown birds. Previous work on Ichthyornis has largely been based on limited fossil material discovered over a century ago.
Here we present high-resolution scans of new, exquisitely preserved three- dimensional specimens of Ichthyornis from the Late Cretaceous of Kansas, focusing on the pectoral girdle and wing elements. The new specimens are more complete and in better condition than the classic material, and include some previously unrepresented elements, as well as better preserved examples of several bones. These include a complete, three-dimensionally preserved sternum, including robust caudolateral processes and relatively developed sternal incisures. The coracoid exhibits very large and recurved acrocoracoid and procoracoid processes, and the scapula preserves a robust, pointed and hook-shaped acromion process, differing from previously referred specimens. This last character is of particular interest, as it represents a previously described autapomorphy of Ichthyornis dispar. Thus, the new material may represent a previously unknown species, or this putative autapomorphy may be more variable among I. dispar than previously appreciated. Wing bones, carpals and hand elements are well preserved as well, and include the first complete radiale known from Ichthyornis.
Ongoing work on these and other new Ichthyornis specimens will shed new light on morphological evolution across the proximal-most portion of the stem-bird phylogenetic tree.

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Fred

Shining a light on nightbird relationships

Albert Chen & Daniel Field, 2018

Shining a light on nightbird relationships: A total evidence phylogeny of strisores

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 182

Strisores is a clade of largely insectivorous crown-group birds that includes highly specialized fliers such as the Apodiformes (swifts and hummingbirds), as well as the nocturnal Caprimulgidae (nightjars), Steatornithidae (oilbird), Nyctibiidae (potoos), Podargidae (frogmouths), and Aegothelidae (owletnightjars). Recent molecular and morphological phylogenetic analyses have uniformly recovered the nocturnal strisorians as a paraphyletic grade with respect to Apodiformes. However, despite the use of large-scale molecular datasets, the precise phylogenetic relationships between the nocturnal strisorians have been resolved inconsistently by different studies and remain controversial.
Given the lack of consensus between results based on molecular data, we examined the possibility that incorporating morphological data from fossils might improve resolution of this phylogenetic problem. Putative stem-members of nearly all major strisorian lineages have been described from Eocene fossil deposits, potentially providing critical information on ancestral character states within Strisores. We adopted a total-evidence approach combining both molecular and morphological data, which has hitherto only been applied to strisorian phylogeny to a limited extent. Our phylogenetic dataset includes 117 morphological characters scored for 24 strisorian taxa (of which 14 were fossil taxa) as well as DNA sequences from the extant taxa. This dataset was analyzed using Bayesian phylogenetic methods in MrBayes, resulting in a novel phylogenetic topology of Strisores that is nonetheless largely congruent with the findings of a comprehensive recent molecular phylogenetic analysis of modern birds.
Our results suggest that total-evidence approaches are promising in their potential to help resolve outstanding questions in crown-bird systematics. In future work, we aim to further clarify the early evolution of Strisores by performing a tip-dating analysis on our dataset to generate a time-calibrated phylogeny of these specialized birds.

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Fred

An exceptional perinate Enantiornithes

Fabien Knoll, Luis Chiappe, Sophie Sánchez, Russell Garwood, Nicholas Edwards, Roy Wogelius, William Sellers, Phillip Manning, Francisco Ortega & José Luis Sanz, 2018

An exceptional perinate Enantiornithes from the Lower Cretaceous of Spain and its implications for ossification pattern in early birds

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 183

The evolutionary diversification of birds has resulted in a marked variation of locomotory adaptations in perinates, a wide range of developmental strategies of hatchlings, and important differences in their growth rates. Discoveries of fossil remains of juvenile birds from the Creta- ceous have furthered our understanding of the developmental pathways of some of the earliest branching avian lineages. Indeed, the analysis of the timing of ossification in these primitive birds can address uncertainties in the foundations of avian comparative developmental biology and the group’s morphological evolution. Using a wide range of analytical and imaging tech- niques (including propagation phase contrast synchrotron microtomography and synchrotron rapid scanning X-ray fluorescence elemental imaging) we explored in depth and non-invasively a unique, nearly complete skeleton of an early juvenile Enantiornithes from the Early Cretaceous (c. 127 Ma) Konservat-lagerstätte of Las Hoyas (Spain), MPCM-lH-26189. The specimen clearly belongs to Enantiornithes, the most species-rich clade of Mesozoic birds, but its early ontogenetic stage makes it impossible to know whether it represents a new species. Irrespective, of the three enantiornithine taxa described from Las Hoyas MPCM-lH-26189 appears closer to Iberomesornis than to Eoalulavis and Concornis, in both skeletal proportions and morphology. This specimen is amongst the smallest known Mesozoic avians, representing post-hatching stages of development. The fossil sheds light on Enantiornithes’ osteogenesis. A complex ossification pattern is present in the sternum, in which both the fan-shaped caudomedial xiphial ossification and the two parasagittal strap-like trabeculae are present, while the craniomedial bony discoid has not ossified yet. At least ten free caudal vertebrae are present, which is an unusually high number. Comparisons between this new specimen and other known early juvenile enantior- nithines support an asynchronous pattern in the sequence of ossification of the sternum and the vertebral column across some of the earliest avians. Our work indicates that the tempo of skeletal maturation and the developmental strategies of the hatchlings of basal birds was more diverse than previously thought, approximating the situation in neognaths.

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Fred

Vocal specialization through tracheal elongation in an extinct Miocene pheasant

Zhiheng Li, Julia Clarke, Chad Eliason, Thomas Stidham, Tao Deng & Zhonghe Zhou, 2018

Vocal specialization through tracheal elongation in an extinct Miocene pheasant from China

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 184

Modifications to the upper vocal tract involving hyper-elongated tracheae have evolved many times within crown birds, and their evolution has been linked to a ?size exaggeration' hypothesis in acoustic signaling and communication, whereby smaller-sized birds can produce louder sounds. A fossil skeleton of a new extinct species of wildfowl (Galliformes: Phasianidae) from the late Miocene of China, preserves an elongated, coiled trachea that represents the oldest fossil record of this vocal modification in birds and the first documentation of its evolution within pheasants. The phylogenetic position of this species within Phasianidae has not been fully resolved, but appears to document a separate independent origination of this vocal modification within Galliformes. The fossil preserves a coiled section of the trachea and other remains supporting a tracheal length longer than the bird's body. This extinct species likely produced vocalizations with a lower fundamental frequency and reduced harmonics compare to similarly-sized pheasants. The independent evolution of this vocal feature in galliforms living in both open and closed habitats does not appear to be correlated with other factors of biology or its open savanna-like habitat. Features present in the fossil that are typically associated with sexual dimorphism suggest that sexual selection may have resulted in the evolution of both the morphology and vocalization mechanism in this extinct species.

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Fred

Colour patterns in the stem upupiform Messelirrisor

Fiann Smithwick, Lisa Sánchez, Gerald Mayr & Jakob Vinther, 2018

Colour patterns in the stem upupiform Messelirrisor

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 185

The Eocene age deposits of Messel have yielded an important array of bird taxa, many of which represent stem members of extant clades. One of these birds is the stem upupiform Messelirrisor. Like many of the Messel birds, specimens of Messelirrisor have exceptional soft tissue preservation including feathers, with some even showing original colour patterns. Thanks to the discovery that integumentary structures such as feathers are preserved due to the retention of the pigment melanin, original colouration can be predicted through quantitative comparison to modern bird melanosomes. Here, we analyse multiple specimens of Messelirrisor and predict a likely colouration of mixed blacks and greys, as well as a striped black and white tail. The extant members of Upupiformes, the hoopoes and wood hoopoes, show strikingly different colouration to one another which is likely related to their respective feeding habitats. Of the two extant clades, Messelirrisor shows more similarity to the wood hoopoes which are specialist arboreal feeders. The colour predictions therefore match the presumed forested environment of Messel and the predicted perching habit of Messelirrisor, although there is no evidence that the distinctive iridescence of wood hoopoes was present in Messelirrisor, which has implications for behavioural adaptations related to signalling.

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Fred

Tooth reduction in Mesozoic birds had a negligible effect on body mass

Yachun Zhou, Corwin Sullivan & Fucheng Zhang, 2018

Tooth reduction in Mesozoic birds had a negligible effect on body mass

Abstracts of the 5th International Paleontological Congress – Paris, 9th-13th July 2018

Free pdf https://ipc5.sciencesconf.org/data/I...tract_Book.pdf pg. 186

Tooth reduction and loss was an important evolutionary process in Mesozoic birds. Analysis of evolutionary trends in the total mass of the dentition, a function of tooth size and tooth number, has the potential to shed light on the evolutionary pattern of tooth reduction and loss, and on the causes of this pattern. Because modern birds lack teeth, however, they cannot provide the basis for a model that would allow estimation of tooth masses in their Mesozoic counterparts. We selected the teeth of crocodilians as analogues of those in Mesozoic birds because the latter are the closest living relatives of the former, and because the two groups are similar in tooth morphology, tooth implantation, and tooth replacement pattern. To estimate tooth masses in Mesozoic birds, we formulated four regression equations relating tooth mass to various linear dimensions, which were measured in 31 intact isolated teeth from eight individual crocodiles (Crocodylus siamensis). The results for Mesozoic birds show that dental mass as a proportion of body mass was negligible, at least from the perspective of flight performance, suggesting that selection pressure favoring body mass reduction was probably not the primary driver of tooth reduction or loss. Variations in dental mass among Mesozoic birds may reflect the different foods they ate, and the different types of feeding behavior they displayed.

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Fred

Fred... These are great. Thank you for sharing.

:clap: