CONFOUNDING CONFUCIUSORNIS

Confuciusornis was about the size of a modern pigeon, with a total length of 50 centimetres (1.6 feet) and a wingspan of up to 70 cm (2.3 ft). Its body weight has been estimated to have been as much as 1.5 kilograms (3.3 lb), or less than 0.2 kg (0.44 lb). Confuciusornis feducciai was about a third longer than average specimens of Confuciusornis sanctus.

Confuciusornis is an interesting species as it shows a mix of basal and derived traits. It was more advanced or derived than Archaeopteryx in possessing a short tail with a pygostyle — a bone formed from a series of short, fused tail vertebrae — and a bony sternum or breastbone, but more basal or "primitive" than modern birds in retaining large claws on the forelimbs, having a primitive skull with a closed eye-socket, and a relatively small breastbone.

At first, the number of basal characteristics was exaggerated: Hou assumed in 1995 that a long tail was present and mistook grooves in the jaw bones for small degenerated teeth. I suppose we see what we want to see and our expectations colour our vision.

Confuciusornis sanctus, Cincinnati Museum of Natural History and Science

The skull morphology of Confuciusornis has been difficult to determine. Many of the specimens are crushed and deformed but we can piece some of it together.

Their skulls were near triangular in side view, and the toothless beak was robust and pointed. The front of the jaws had deep neurovascular foramina and grooves, associated with the keratinous rhamphotheca — horn-covered beak.

The skull was rather robust, with deep jaws, especially the mandible. The tomial crest of the upper jaw — bony support for the jaw's cutting edge — was straight for its entire length. The premaxillae —front bones of the upper jaw — were fused together for most of the front half of the snout, but were separated at the tip by a V-shaped notch. The frontal processes that projected hindwards from the premaxillae were thin and extended above the orbits (eye openings) like in modern birds, but unlike Archaeopteryx and other primitive birds without pygostyles, where these processes end in front of the orbits. The maxilla (the second large bone of the upper jaw) and premaxilla articulated by an oblique suture, and the maxilla had an extensive palatal shelf. The nasal bone was smaller than in most birds and had a slender process that directed down towards the maxilla.

The orbit was large, round, and contained sclerotic plates — the bony support inside the eye. A crescent-shaped element that formed the front wall of the orbit may be an ethmoidolacrimal complex similar to that of pigeons, but the identity of these bones is unclear due to bad preservation, and the fact that this region is very variable in modern birds. The external nares, bony nostrils, were near triangular and positioned far from the tip of the snout. The borders of the nostrils were formed by the premaxillae above, the maxilla below, and the nasal wall at the back.

Birds: Living Dinosaurs

Few specimens preserve the sutures of the braincase, but one specimen shows that the frontoparietal suture crossed the skull just behind the postorbital process and the hindmost wall of the orbit.

This was similar to Archaeopteryx and Enaliornis, whereas it curves back and crosses the skull roof much farther behind in modern birds, making the frontal bone of Confuciusornis small compared to those of modern birds.

A prominent supraorbital flange formed the upper border of the orbit and continued as the postorbital process, which had prominent crests that projected outwards to the sides, forming an expansion of the orbit's rim.

The squamosal bone was fully incorporated into the braincase wall, making its exact borders impossible to determine, which is also true for adult modern birds.

Various interpretations have been proposed of the morphology and identity of the bones in the temporal region behind the orbits, but it may not be resolvable with the available fossils. Confuciusornis was considered the first known bird with an ancestral diapsid skull — with two temporal fenestrae on each side of the skull — in the late 1990s, but in 2018, Elzanowski and colleagues concluded that the configuration seen in the temporal region of confuciusornithids was autapomorphic — a unique trait that evolved secondarily rather than having been retained from a primitive condition — for their group.

Victoria Crowned Pidgeon, Goura victoria

The quadrate bone and the back end of the jugal bar were bound in a complex scaffolding that connected the squamosal bone with the lower end of the postorbital process. This scaffolding consisted of two bony bridges, the temporal bar and the orbitozygomatic junction, which gave the appearance of the temporal opening being divided similarly to diapsid skulls, though this structure is comparable to bridges over the temporary fossa in modern birds.

The mandible, lower jaw, is one of the best-preserved parts of the skull. It was robust, especially at the front third of its length. The tomial crest was straight for its entire length, and a notch indented the sharp tip of the mandible.

The mandible was spear-shaped when viewed from the side due to its lower margin slanting downwards and back from its tip for the front third of its length — the jaw was also deepest at a point one third from the tip.

The symphyseal part — where the two halves of the lower jaw connected — of the dentary was very robust. The lower margin formed an angle at the level of the front margin of the nasal foramen, which indicates how far back the rhamphotheca of the beak extended.

The dentary had three processes that extended backwards into other bones placed further back in the mandible. The articular bone at the back of the mandible was completely fused with the surangular and prearticular bones. The mandible extended hindwards beyond the cotyla — which connected with the condyle of the upper jaw — and this part was therefore similar to a retroarticular process as seen in other taxa. The surangular enclosed two mandibular fenestrae. The hindmost part of the surangular had a small foramen placed in the same position as similar openings in the mandibles of non-bird theropods and modern birds. The splenial bone was three-pronged — as in some modern birds, but unlike the simple splenial of Archaeopteryx — and its lower margin followed the lower margin of the mandible. There were large rostral mandibular fenestra and a small, rounded caudal fenestra behind it.

Though only two specimens preserve parts of the beak's keratinous covering, these show that there would have been differences between species not seen in the skeleton. The holotype of C. dui preserves the outline of an upwards curving beak which sharply tapers towards its tip, while a C. sanctus specimen has an upper margin that is almost straight and a tip that appears to be slightly hooked downwards.

Photo One: Zhiheng Li, Zhonghe Zhou, Julia A. Clarke - http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198078, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=78911418

Photo Two: James St. John, Ohio State University, Newark - https://www.flickr.com/photos/jsjgeology/15236217920/, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=36907383

BIRDS OF THE JEHOL BIOTA

In November 1993, Chinese paleontologists Hou Lianhai and Hu Yoaming, of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing received a call from an excited local fossil collector.

He claimed to have quite a remarkable specimen on his hands. The team visited Zhang He at his home in Jinzhou, or Chinchow, a coastal prefecture-level city in central-west Liaoning province

Zhang showed them a spectacular fossil bird specimen he'd recently purchased at a local flea market. Very little was known about the specimen but it was clearly important and the team was hopeful more of this paleo goodness might turn up.

They didn't have that long to wait. A month after his visit to Zhang, Hou learned about a second specimen discovered by a local farmer, Yang Yushan. Things were looking up. Best of all, he learned that both specimens were likely from the same locality in Shangyuan, Beipiao. This was not a one-off discovery or an amazing but anonymous find. With two specimens to compare, the locality determined, the possibility of an interesting publication and career advancement would be a reality.

In 1995, the two specimens, as well as a third, were formally described as a new genus and species, Confuciusornis sanctus, by Hou and colleagues. The generic name combines the philosopher Confucius with a Greek ὄρνις, (ornis), "bird". The specific name means "holy one" in Latin and is a translation of Chinese 圣贤, shèngxián, "sage", again in reference to Confucius.

The first discovered specimen was designated the holotype (as you do) and catalogued under the specimen number IVPP V10918; it comprises a partial skeleton with skull and parts of the forelimb.

Of the other two skeletons, one (paratype, IVPP V10895) comprises a complete pelvis and hind limb, and the other (paratype, IVPP V10919–10925) a fragmentary hind limb together with six feather impressions attached to both sides of the tibia or shin bone.

All was well until those reading the journal articles realized that the two paratype specimens only comprise bones that were unknown from the holotype. An oversight, likely by design, but this lack of overlap between the specimens made their referral to the species speculative. The lack of overlap also gave a wide margin for error in the naming of additional, albeit hopeful, new species names — names that would later need to be amended. Luckily, the discovery of a veritable treasure trove of well-preserved specimens shortly after confirmed that the specimens indeed represented a single species.

Together with the early mammal Zhangheotherium, which was discovered about the same time, Confuciusornis was considered the most remarkable fossil discovery of the Jehol biota. If you're not in the paleo loop, the Jehol biota of northeastern China has unearthed some of the most important Mesozoic bird specimens worldwide over the past two decades.

It has also given us another fossil-rich Lagerstätte that includes a wonderful mix of advanced and ancient species. My speculation is that northeast Asia was isolated for part of the Jurassic by the Turgai Sea that separated Europe from Asia at that time. The fossils at Jehol are numerous and exceptionally well preserved. Think of the Cambrian goodies at Burgess or the Altmühltal Formation, Jurassic Konservat-Lagerstätte at Solnhofen. Quite remarkably, fully articulated skeletons, soft tissues, colour patterns, stomach contents, and twigs with leaves and flowers still attached, can be found within the Jehol biota.

A beautifully preserved Archaeopteryx

In the late 1990s, Confuciusornis was considered both the oldest beaked bird as well as the most primitive bird after Archaeopteryx. It was also considered to be only slightly younger than Archaeopteryx. 

Yixian Formation, the rock unit where most Confuciusornis specimens have been found, was thought to be of Late Jurassic (Tithonian) age at the time.

Although two bird genera, Sinornis and Cathayornis, had already described from the Jehol biota back in 1992, these were based on fragmentary remains and stem from the younger Jiufotang Formation. At the time, the Jiufotang was thought to be Early Cretaceous. Both formations have since been dated to the Lower Cretaceous — Barremian to Aptian — 131–120 million years ago.

In 1995, local farmers began digging for fossils near the village of Sihetun, Beipiao, in what would become one of the most productive localities of the Jehol biota. The then largely unknown site is truly world-class. Large-scale professional excavations at this single locality have been carried out by the IVPP from 1997 onwards. Not one, not two, but several hundred specimens of Confuciusornis have now been unearthed from here. Many additional sites producing fossils of the Jehol biota have been recognized since, distributed over a large region including Liaoning, Hebei, and Inner Mongolia.

Due to the great abundance, preservation, and commercial value of the fossils, excavations by local farmers produced an unusually high number of fossils. Although some of these fossils have been added to the collections of Chinese research institutions, more have been smuggled out of the country.

In 1999, it was estimated that the National Geological Museum of China in Beijing housed nearly a hundred (100) specimens of Confuciusornis, and in 2010, the Shandong Tianyu Museum of Nature was reported to possess five hundred and thirty-six (536) specimens. While it is illegal to export them, the majority of specimens are still held privately and thus are not available for research. I see them on social media and occasionally they come up for sale on eBay.

At one time forty individuals were discovered on a surface of about 100 m2. This unusual bone bed was likely the result of an entire flock of birds being simultaneously killed by ash, heat or poisonous gas following the volcanic eruptions that caused the tuff stone in which the fossils were found to be deposited as lake sediments. An avian death bed is highly unusual. Very sad for our feathered friends but grateful for what has been revealed by this rare event.

Notes: Confuciusornis chuonzhous was named by Hou in 1997 based on specimen IVPP V10919, originally a paratype of Confuciusornis sanctus. The specific name refers to Chuanzhou, an ancient name for Beipiao. Confuciusornis chuonzhous is now generally considered synonymous with Confuciusornis sanctus.

Confuciusornis suniae, named by Hou in the same 1997 publication, was based on specimen IVPP V11308. The specific name honours Madam Sun, the wife of Shikuan Liang who donated the fossil to the IVPP. Confuciusornis suniae is now usually considered synonymous with Confuciusornis sanctus.

Reference: Zhou, Z; Hou, L. (1998). "Confuciusornis and the early evolution of birds". Vertebrata PalAsiatica. 36 (2): 136–146.

Zhou, Z. (2006). "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives". Geological Journal. 41 (3–4): 377–393. doi:10.1002/gj.1045.

CALAMOPLEURUS OF BRAZIL

This well-preserved fossil fish skull is from Calamopleurus (Agassiz, 1841), an extinct genus of bony fishes related to the heavily armoured ray-finned gars.

They are fossil relics, the sole surviving species of the order Amiiformes. Although bowfins are highly evolved, they are often referred to as primitive fishes and living fossils as they retain many of the morphologic characteristics of their ancestors.

This specimen was found in Lower Cretaceous outcrops of the Santana Formation in the Araripe Basin UNESCO Global Geopark. The Santana Formation of north-east Brazil contains one of the most important Mesozoic fossil Konservat Lagerstatten on Gondwana (Maisey, 1991; Martill, 1993, 1997, 2001; Kellner, 2002; Fara et al., 2005). The formation crops out on the flanks of the Chapada do Araripe in southern Ceara´, western Pernambuco and a small part of eastern Piaui in the north-eastern Brazilian Caatinga. It forms part of a heterogeneous assemblage of spectacularly fossiliferous rocks of Cretaceous age (Gardner, 1841; Brito, 1984; Maisey, 1991; Martill, 1993).

Two formations within the basin are well-known as Konservat Lagerstatten; the Nova Olinda Member of the Crato Formation lies a few tens of metres below the Santana Formation, and both have contributed considerably to our knowledge and understanding of Gondwanan Cretaceous palaeobiotas (Martill, 1988, 1993; Wenz and Brito, 1990; Maisey, 1991, 1993; and many references herein). Only the age of the Romualdo Member of the Santana Formation, a dominantly silty shale sequence that includes the highly fossiliferous carbonate concretion-bearing unit, is considered here.

Although the Santana Formation concretions have been famous for their enclosed fossils, especially fishes, for over 150 years, in more recent times they have become known for a diversity of dinosaur and pterosaur remains in an excellent state of preservation (Martill, 1998; Martill and Unwin, 1989; Kellner, 1996a,b; Frey et al., 2003a,b) comparable with, and sometimes exceeding, that of the Jurassic Solnhofen Limestone of Bavaria (Barthel et al., 1990), especially in their three-dimensionality. Photo and collection of David Murphy.

References: Martill, David M. The age of the Cretaceous Santana Formation fossil Konservat Lagerstatten of north-east Brazil: a historical review and an appraisal of the biochronostratigraphic utility of its palaeobiota, Cretaceous Research 28 (2007) 895-920.

THEROPODS OF A FEATHER

Birds are a group of warm-blooded vertebrates constituting the class Aves, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.

These modern dinosaurs live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. There are about ten thousand living species, more than half of which are passerine, or "perching" birds.

Birds have wings whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds.

Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in some birds, including ratites, penguins, and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming.

Best of all, birds are feathered theropod dinosaurs, and constitute the only living dinosaurs. Based on fossil and biological evidence, most scientists accept that birds are a specialized subgroup of theropod dinosaurs, and more specifically, they are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, amongst others. As palaeontologists discover more theropods closely related to birds, the previously clear distinction between non-birds and birds has become a bit muddy.

Recent discoveries in the Liaoning Province of northeast China, which include many small theropod feathered dinosaurs — and some excellent fakes — contribute to this ambiguity. Still, other fossil specimens found here shed a light on the evolution of Aves. Confuciusornis sanctus, an Early Cretaceous bird from the Yixian and Jiufotang Formations of China is the oldest known bird to have a beak.

Like modern birds, Confuciusornis had a toothless beak, but close relatives of modern birds such as Hesperornis and Ichthyornis were toothed, telling us that the loss of teeth occurred convergently in Confuciusornis and living birds.

Confuciusornis sanctus, Cretaceous Bird from China, 125 mya

The consensus view in contemporary palaeontology is that the flying theropods, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids and troodontids.

Together, these form a group called Paraves. Some basal members of this group, such as Microraptor, have features which may have enabled them to glide or fly. The most basal deinonychosaurs were wee little things. This evidence raises the possibility that the ancestor of all paravians may have been arboreal, have been able to glide, or both. Unlike Archaeopteryx and the non-avialan feathered dinosaurs, who primarily ate meat, tummy contents from recent avialan studies suggest that the first avialans were omnivores. Even more intriguing...

Avialae or "bird wings" are a clade of flying dinosaurs containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to modern birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally bantered back and forth.

Archaeopteryx lithographica, from the late Jurassic Period Solnhofen Formation of Germany, is the earliest known avialan which may have had the capability of powered flight. However, several older avialans are known from the Late Jurassic Tiaojishan Formation of China, dating to about 160 million years ago.

The Late Jurassic Archaeopteryx is well-known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to clearly display both traditional reptilian characteristics — teeth, clawed fingers, and a long, lizard-like tail—as well as wings with flight feathers similar to those of modern birds. It is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor.

Unlikely yet true, the closest living relatives of birds are the crocodilians. Birds are descendants of the primitive avialans — whose members include Archaeopteryx — which first appeared about 160 million years ago in China.

DNA evidence tells us that modern birds — Neornithes — evolved in the Middle to Late Cretaceous, and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 mya, which killed off the pterosaurs and all non-avian dinosaurs.

In birds, the brain, especially the telencephalon, is remarkably developed, both in relative volume and complexity. Unlike most early‐branching sauropsids, the adults of birds and other archosaurs have a well‐ossified neurocranium. In contrast to most of their reptilian relatives, but similar to what we see in mammals, bird brains fit closely to the endocranial cavity so that major external features are reflected in the endocasts. What you see on the inside is what you see on the outside.

This makes birds an excellent group for palaeoneurological investigations. The first observation of the brain in a long‐extinct bird was made in the first quarter of the 19th century. However, it was not until the 2000s and the application of modern imaging technologies that avian palaeoneurology really took off.

Understanding how the mode of life is reflected in the external morphology of the brains of birds is but one of several future directions in which avian palaeoneurological research may extend.

Although the number of fossil specimens suitable for palaeoneurological explorations is considerably smaller in birds than in mammals and will very likely remain so, the coming years will certainly witness a momentous strengthening of this rapidly growing field of research at the overlap between ornithology, palaeontology, evolutionary biology and the neurosciences.

Reference: Cau, Andrea; Brougham, Tom; Naish, Darren (2015). "The phylogenetic affinities of the bizarre Late Cretaceous Romanian theropod Balaur bondoc (Dinosauria, Maniraptora): Dromaeosaurid or flightless bird?". PeerJ. 3: e1032. doi:10.7717/peerj.1032. PMC 4476167. PMID 26157616.

Reference: Ivanov, M., Hrdlickova, S. & Gregorova, R. (2001) The Complete Encyclopedia of Fossils. Rebo Publishers, Netherlands. p. 312

Photo: By Tommy from Arad - Confuciusornis; FunkMonk, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=24115307