Sunday, June 12, 2022

Prehistoric Planet

The talk of the town (or at least of the online paleontology community) lately has been Prehistoric Planet, a new documentary series now available for streaming on Apple TV+. This show has been eagerly anticipated ever since it was first publicly revealed in 2019 to have been in production, not least because paleontology documentaries have been thin on the ground in the last decade. The dearth of content has been especially true regarding series that portray prehistoric life as though it had been filmed in the wild, a premise popularized by Walking with Dinosaurs in 1999.

Despite the inevitable comparisons to Walking with Dinosaurs, however, Prehistoric Planet borrows more from recent BBC documentaries that focus on the modern biosphere, such as The Blue Planet, Planet Earth, and their sequels. Regular viewers of nature documentaries will likely notice stylistic choices and even specific film sequences in these shows that inspired elements of Prehistoric Planet (including its title). Unlike Walking with Dinosaurs, the series is organized by habitat, with each episode being composed of several vignettes that take place in multiple locations, instead of revolving around an extended narrative about one specific individual animal or ecosystem. In addition, all of the segments in Prehistoric Planet are set within a fairly narrow window of geologic time (the Maastrichtian Age of the Late Cretaceous), not spread across the entire Mesozoic.

Now that the show has been released, it appears that most responses to Prehistoric Planet have been overwhelmingly positive, and the acclaim is well deserved in my book. The considerable advances in both technology and paleontological science since Walking with Dinosaurs are more than evident throughout the series, and others have already commented repeatedly on the spectacular visual effects as well as the naturalistic, scientifically plausible depictions of extinct animals. Instead of heaping on more of the same (albeit justified) general praise, I'd like to take a closer look specifically at the show's portrayals of maniraptoran dinosaurs. This is a maniraptoran blog, after all.

There is quite a bit to cover, for maniraptors are featured extensively in Prehistoric Planet. Most exciting to me was the fact that there is a whole segment dedicated to an alvarezsaurid, namely Mononykus from the Nemegt Formation of Mongolia! This sequence has to rank among my favorites in the show, not only because I am extremely biased in favor of alvarezsaurids, but also because I was very impressed by how much scientific knowledge about alvarezsaurid biology it incorporated. Traveling for long distances on foraging excursions? Sensitive hearing for detecting prey? Using the specialized thumb claw as an excavation tool? Feeding on wood-dwelling termites instead of mound-building ones? Whereas some segments of Prehistoric Planet revolve around behaviors widespread in modern animals that were transplanted onto select prehistoric species as (generally reasonable) speculation, almost everything Mononykus is shown doing was based directly on research into alvarezsaurid anatomy, function, and ecology.

What's more, this depiction of Mononykus appears to have resonated strongly with audiences. From what I've seen, it's probably fair to consider Mononykus one of the breakout stars of Prehistoric Planet, with even executive producers Jon Favreau and Mike Gunton identifying it as one of their favorite dinosaurs in the series. Alvarezsaurids have made a surprisingly large number of documentary appearances considering their relative obscurity (BBC's Chased by Dinosaurs in 2002 and Discovery Channel's Dinosaur Planet in 2003 come to mind), but none of those previous shows spent much time highlighting what makes these dinosaurs strange and interesting. Thanks to Prehistoric Planet's approach, it seems that Mononykus is well on its way to becoming a household dinosaur name, and I couldn't be happier about that.

Paleoartist Ilari Pätilä has proposed calling the Mononykus from Prehistoric Planet "Dolores", after a character from the Disney film Encanto who has the power of super-sensitive hearing. I approve, though the production team behind Prehistoric Planet reportedly has their own internal nickname for her.

Therizinosaurs are represented in Prehistoric Planet by the largest of them all, Therizinosaurus. Another maniraptor known from the Nemegt Formation, Therizinosaurus first appears in the background visiting a watering hole alongside other Nemegt dinosaurs (including Mononykus), but is not acknowledged by the narration at this point. A later scene, however, features a group of juvenile Therizinosaurus as its protagonists. This segment has the distinction of being, to my knowledge, the only one in the series for which visual elements were neither given away in promotional material nor publicly described by reviewers who'd seen the show early, which made it especially enjoyable to watch for the first time.

The way in which the Therizinosaurus are shown using their beaks and claws for feeding is supported by published research on therizinosaurs, as is their precocial nature. Their attempt to reach a bees' nest for honey by climbing with their beaks, claws, and flaps of their forelimbs is more speculative, but well within the realm of possibility. It is furthermore a fun potential nod to a discredited hypothesis that therizinosaurs might have had arboreal ancestors, while at the same time showing that most flightless Mesozoic theropods probably weren't particularly good climbers (which might not have stopped some from occasionally trying to climb anyway).

A juvenile Therizinosaurus has a go at wing-(and-beak-and-claw-)assisted incline climbing.

Despite their efforts, the young Therizinosaurus are quickly dissuaded by bee stings. They are eventually rewarded, however, when an adult Therizinosaurus shows up. Undeterred by the bees, it knocks the nest to the ground with a single swat from one of its clawed hands, and leaves behind enough leftovers for the youngsters to savor. This was a great way to convey the power and majesty of the adult Therizinosaurus without placing it in a stereotypically violent scenario. There is a minor error in the narration for this sequence: the adult is mistakenly described as 30 ft tall instead of 30 ft long. That being said, lead scientific consultant Darren Naish has pointed out that it is not inconceivable for a large Therizinosaurus to have been able to rear to heights approaching 30 ft.

Oviraptorosaurs appear in the form of the tall-crested Corythoraptor from the Nanxiong Formation of China. They do not play a major role beyond serving as would-be prey for the tyrannosaurid Qianzhousaurus, but they have a lovely design that makes it clear that just as much research and care went into their depiction as for those of the other computer-generated creatures in the show. In fact, the segment that they appear in is perhaps among the most aesthetically pleasing and atmospheric in the entire series. It was also neat to see the Corythoraptor feeding on ginkgo fruits and using their wings for balance while running, in a manner similar to ostriches. (As an aside: I'm not a stickler for the pronunciation of scientific names, but as someone who knows Mandarin, hearing narrator Sir David Attenborough pronounce Qianzhousaurus correctly was a plus.) 

A flock of foraging Corythoraptor makes for pretty dinosaurs in a pretty forest.

The function of feathers in flightless maniraptors is spotlighted dramatically in one of two segments starring the dromaeosaurid Velociraptor. Strictly speaking, the "Velociraptor" in Prehistoric Planet were based on indeterminate velociraptorines from Maastrichtian fossil deposits, with Velociraptor proper having only been found in the Djadochta Formation and possibly the Wulansuhai Formation, which are generally considered Campanian in age. As others have noted, however, there is enough ambiguity in the dating of Late Cretaceous rock units from central Asia that the Djadochta and Nemegt Formations may in fact have been laid down in different environments that coexisted at approximately the same time. In any case, the presence of Velociraptor-like dromaeosaurids in the Maastrichtian of central Asia is readily justifiable.

Velociraptor is introduced with a pair of them trying to prey on an unspecified lizard, which is in turn feeding on carrion flies drawn in by some dozing Tarbosaurus (an obvious homage to footage of agamid lizards hunting for flies near lions, as shown on BBC's Africa in 2013). Where Velociraptor truly gets to shine though is in its second appearance, which depicts a trio stalking azhdarchid pterosaurs on a sheer cliff face, perhaps partly inspired by fossil evidence that Velociraptor at least fed on azhdarchids occasionally. The Velociraptor are portrayed as agile hunters, using wing-assisted locomotion to boost their jumps, control descents, and even survive dangerous falls on difficult terrain. These maneuvers are reminiscent not only of locomotor strategies seen in modern birds, but also observations of polar bears and especially snow leopards hunting on cliffsides. Somewhat surprisingly, the famous "raptor prey restraint" model (which proposes that dromaeosaurids used their wings to stabilize themselves while restraining prey with their feet) is not explicitly shown in Prehistoric Planet, though this may have been deliberate given that the bloodier aspects of predation are noticeably downplayed in the imagery of this series.

This may not be the version that mainstream popular culture is most familiar with, but Velociraptor was undoubtedly a skilled predator.

Another dromaeosaurid that shows up is an unspecified polar species, presumably based on dromaeosaurid teeth from the Prince Creek Formation of Alaska. A group of these dromaeosaurids is featured cooperating to hunt hadrosaurids larger than themselves. Dromaeosaurids being shown bringing down unrealistically large prey items is a long-standing pet peeve of mine, but here the predator–prey relationship is portrayed much more believably: it is stated that the polar dromaeosaurids are targeting juvenile hadrosaurids rather than adults, and the one they eventually feed on is not directly killed by them, instead dying from being swept away in its panic by a fast-flowing river.

Even in depicting an animal known only from fragmentary remains, Prehistoric Planet draws heavily from fossil evidence. The polar dromaeosaurids have a frond of tail feathers restricted to the back half of the tail and with two especially elongate feathers at its tip, probably inspired by the tail feathering found in one specimen of Microraptor. One is also shown sleeping in a curled-up pose, based on the posture preserved in two specimens of the troodontid Mei, and leaving functionally two-toed tracks in the snow, based on actual fossil trackways made by dromaeosaurids.

A soundly sleeping polar dromaeosaurid.

Two separate but thematically similar segments portray possible interactions Mesozoic paravians might have had with wildfires, modeled after interesting behaviors exhibited by modern birds. One features a third dromaeosaurid taxon, Atrociraptor from the Horseshoe Canyon Formation of Canada, picking up a burning stick to fumigate its feathers, in an allusion to similar activities that have been documented in corvids. In another, an unspecified troodontid (presumably a member of the taxonomic tangle that is the Late Cretaceous troodontids of North America) actively spreads burning vegetation to drive prey into the open, as has been reported for some Australian kites and falcons. These scenarios are speculative, and it seems unlikely that direct evidence for them could ever be ascertained from the fossil record, but dromaeosaurids and troodontids were probably versatile predators with relative brain-to-body ratios within the range of (albeit not exceptionally large relative to) those seen in modern birds, so it's certainly not out of the question that they could have practiced such behaviors.

An Atrociraptor reaps the rewards of a forest fire.

There is one major group of maniraptors that gets the short end of the stick in Prehistoric Planet, however, and it's avialans. They are not completely absent: enantiornitheans show up in a few scenes and various bird-like forms are sometimes visible as set-dressing in the background or in wide shots, but they never feature as protagonists in the individual segments nor even as the focus of any close-ups. In fact, if I had any notable criticism of the series, it would be the apparent neglect of the smaller tetrapods in Late Cretaceous ecosystems. Only a single mammal species appears on the show, unmentioned and unnamed, and its sole role is to be killed by the aforementioned troodontid. It also nearly beggars belief that a time-traveling documentary crew would film a whole episode on freshwater habitats in the Maastrichtian and fail to include any footage of crocodyliforms or turtles.

In practice, of course, resources to create and animate digital models of prehistoric life for a series like this are limited, so it is understandable that the production team prioritized particularly strange and spectacular fauna over more "mundane-looking" ones. I would contend though there likely is substantial audience interest in learning about the origins of modern animals, which increased spotlight on taxa more closely related to extant forms would have provided opportunities for. Furthermore, the Mesozoic diversity and disparity of "microvertebrates" is regularly underappreciated. Leaving aside recent Maastrichtian avialan discoveries like Asteriornis and Falcatakely, which were almost certainly published too late to be incorporated into the show, it probably would not have been difficult to come up with engaging storylines featuring the bizarre, island-dwelling Balaur or enantiornithean nesting colonies (both of which, as a bonus, have been the focus of Darren's own research).

Even without adding or replacing any of the existing narratives in Prehistoric Planet, I would have liked to see at least some split-second close-ups of the enantiornitheans, considering that the team had evidently gone to the trouble of making digital models for them. Such "incidental" shots are a regular component of modern wildlife documentaries and probably would have made the ecosystems portrayed feel even more vibrant and immersive. As it is, the show already spends time (and occasionally narration) on shots of crustaceans, fishes, fungi, plants, and other organisms in "non-starring" roles, not to mention an entire segment on ammonoids (arguably one of the highlights of the entire series), so I have no doubt that a few extra seconds of microvertebrate footage could have been used to great effect.

Probably the closest we get to an in-focus shot of an enantiornithean on Prehistoric Planet: one is perched in the upper right corner here as the giant ornithomimosaur Deinocheirus prepares to use its tree as a scratching post.

Another concern about Prehistoric Planet I've seen from some viewers is that it generally does not clarify which aspects are speculation and which are based on direct evidence. This is not a new discussion regarding paleontology documentaries of this sort; very similar arguments were had with respect to Walking with Dinosaurs. To their credit, Walking with Dinosaurs and its sequel series Walking with Beasts had tie-in websites with extensive sections explaining the scientific backing behind their creative decisions, and the former also had a companion book on the same subject (co-authored by Darren, as it happens). Prehistoric Planet, meanwhile, currently has 5-minute videos (available for free on the Apple TV YouTube channel) accompanying each episode that feature interviews with paleontologists and delve into the science behind the series. These "Uncovered" videos, as they are called, are quite good for what they are, but each of them focuses only on a single narrow topic (e.g., how we know Velociraptor had feathers), leaving a great majority of what is shown in the episodes unaddressed. The production of additional "Uncovered" videos is allegedly being considered, and I very much hope that it comes to pass. If anything, a lack of transparency does a disservice to the tremendous amount of thought and research that clearly went into this show.

These critical comments, however, do not undermine the excellence that Prehistoric Planet has achieved. The series is outstanding in nearly every way possible, setting a new and extremely high standard for works of this genre, and the fact that my biggest issues largely amount to a desire for more is very much a testament to its success. Given the positive reception so far, I feel hopeful that we will eventually see future seasons of Prehistoric Planet and, with luck, maybe even a whole new age of paleontology-inspired media.

Friday, April 1, 2022

Delays and Updates

I should know by now that announcing one's plans almost guarantees that they won't happen, but here we are. I'd mentioned that I'd already decided on what to write for the annual April 1st post this year; however, the way things have transpired, other projects and events have demanded enough of my attention to prevent me from writing it. Maybe I'll write it up within the next month, or (arguably more likely) maybe I'll save it for next year... we'll see. In the meantime, perhaps you can consider the Story of Perrine review a retroactive make-up post for today.

Most of the projects that I've been working on instead are not at a stage where they can be discussed in detail. However, one major announcement I can make is that within the last two weeks, both my labmate Juan Benito Moreno and I passed our PhD vivas (with no corrections requested of either of us), making us the first PhDs to fledge from the Field Palaeobiology Research Group. I suppose I really am Dr. Claw now...

Saturday, January 22, 2022

New (Extinct) Maniraptors of 2021

By my count, 42 new species of extinct maniraptors were named in 2021, which is about par for the course these days. Let's take a quick look at these new taxa and other nomenclatural proposals.

New alvarezsaurs have been described at a fairly steady trickle in recent years, and 2021 gave us Khulsanurus, known from a partial skeleton from the Late Cretaceous Barun Goyot Formation of Mongolia. It was discovered at the same locality as Parvicursor, but can be distinguished based on vertebral anatomy.

No new oviraptorosaur species were described last year; in fact, they may have lost a member. A new specimen of Elmisaurus preserves overlapping material nearly identical to Nomingia, lending credence to the hypothesis that the two are synonymous (in which case the name Elmisaurus would take priority).

Non-ornithothoracean Paravians
2021 was a good year for dromaeosaurids, with the velociraptorines Shri (formerly known by the nickname "Ichabodcraniosaurus") and Kuru (formerly known by the nickname "Airakoraptor") both described based on partial skeletons from the Barun Goyot Formation. Less completely known are Kansaignathus (based on a partial jaw and possibly teeth from the Late Cretaceous Yalovach Formation of Tajikistan), Vectiraptor (based on partial vertebrae from the Early Cretaceous Wessex Formation of the United Kingdom), and Ypupiara (an unenlagiine based on jaw fragments from the Late Cretaceous Serra da Galga Formation* of Brazil). Tragically, the type specimen of Ypupiara was among the fossils lost in the 2018 fire that destroyed the main building of the National Museum of Brazil.

*Ypupiara was described as being from the Marília Formation. However, it was recently proposed that the classic Marília Formation should be split into the separate Marília and Serra da Galga Formations.

Holotype of Shri, from Turner et al. (2021).

Troodontids, on the other hand, got Papiliovenator from the Late Cretaceous Wulansuhai Formation of China, known from a partial skeleton including a nearly complete skull. Its name translates (I think quite adorably) into "butterfly hunter", not based on any inference about its ecology, but on the "butterfly-like" shape of its dorsal vertebrae. There was also Tamarro from the Late Cretaceous Talarn Formation of Spain, known from a partial metatarsal. Meanwhile, a detailed reassessment of small theropods from the Dinosaur Park Formation concluded that Latenivenatrix cannot be reliably distinguished from Stenonychosaurus, and that the two should be (re-)synonymized.

Skull of Papiliovenator, from Pei et al. (2022). (The paper was released as an advance online publication in 2021.)

Last year also saw the description of a new Jeholornis-like avialan, Neimengornis, from the Early Cretaceous Jiufotang Formation of China. It appears to be known from an essentially complete skeleton. However, there have already been suggestions that the type specimen is likely a chimera.

As is often the case, the Jiufotang Formation also contributed some new enantiornitheans in 2021, two to be precise. One of these was Brevirostruavis, which is notable for preserving an elongated hyoid, suggesting that it may have used its tongue for handling food. Although the original description compares this condition to that seen in hummingbirds and woodpeckers, the hyoid elongation seen in Brevirostruavis does not look to my eye quite as extreme as that of those crown birds. My guess would be that Brevirostruavis might have used its tongue to help pick up food and manipulate it within its mouth, but did not use a feeding strategy that involved protruding the tongue very far beyond its snout.

The other new Jiufotang enantiornithean was Yuanchuavis, which preserves a set of eight tail feathers forming a fan-like array. This contrasts with the typical condition seen in most other enantiornitheans (which tended to either lack large tail feathers or have only a single pair of them), but resembles that of Chiappeavis. Unlike Chiappeavis, the central pair of tail feathers in Yuanchuavis was particularly elongate.

Personally, I think one of the most scientifically important new maniraptors to be named last year was Yuornis from the Late Cretaceous Qiupa Formation of China. It is based on a partial skeleton with an essentially complete skull preserved in three dimensions, a rarity for avialan fossils. It is also one of the few enantiornitheans known to have had entirely toothless jaws.

Holotype of Yuornis, from Xu et al. (2021).

A fourth enantiornithean to come out of 2021 was Fortipesavis, known from a foot preserved in Late Cretaceous Burmese amber that had been previously described in 2019.

Non-neornithean Euornitheans
Two non-neornithean euornitheans were named in 2021 based primarily on cranial material, these being Brevidentavis and Meemannavis from the Early Cretaceous Xiagou Formation of China. The type specimen of Brevidentavis was previously reported as the skull of Gansus, but a more likely candidate for an actual Gansus skull was described in the new paper. The lower jaw of Brevidentavis exhibits unusually short, blunt teeth set in a groove (instead of in sockets), whereas Meemannavis has a toothless lower jaw.

Holotype of Brevidentavis, from O'Connor et al. (in press).

One Mesozoic avialan named last year that was not discovered in Asia was Kaririavis from the Early Cretaceous Crato Formation of Brazil. Based on a partial foot, it was unusual for a Cretaceous euornithean in being particularly small (around the size of a sparrow) and in that its one preserved toe claw was large and strongly curved.

Perhaps one of the biggest overhauls in dinosaur systematics in 2021 was the reinterpretation of geranoidids, eogruids, and ergilornithids as stem-ostriches instead of gruiforms. Although a close relationship between ergilornithids and ostriches had been suggested in the 1950s and contemplated more recently in light of further data on fossil paleognaths, anatomical information from newly described eogruid and ergilornithid specimens seems to strongly bolster this hypothesis. In their revision of these birds' affinities, the authors additionally resurrected the genus Proergilornis, which had been previously synonymized with Ergilornis, and suggested that it was less closely related to extant ostriches than ergilornithids proper.

A new fossil paleognath was also described last year, the kiwi Apteryx littoralis, based on a tarsometatarsus from the Pleistocene of New Zealand. Kiwi fossils are rarely found, and this species is the first one known from the early Pleistocene.

A couple of extinct total-group anseriforms were named in 2021. One of these was the small presbyornithid Bumbalavis from the Eocene Naran-Bulak Formation of Mongolia. (Meanwhile, the type specimen of "Presbyornis" mongoliensis from the same locality was reinterpreted as a stem-mirandornithean similar to Juncitarsus.) The other was the stiff-tailed duck Manuherikia primadividua from the Miocene Bannockburn Formation of New Zealand, the fourth species to be named in the genus Manuherikia. It appears to be stratigraphically separated from the older M. lacustrina.

Two small, early total-group galliforms were described from the Naran-Bulak Formation last year as well, these being Bumbanipodius and Bumbanortyx.

New fossil members of Strisores don't get described every day, or every year for that matter. (The last one I recall was Cypseloramphus from 2016.) That's why I was excited to see the publication of Archaeodromus from the Eocene London Clay Formation of the United Kingdom, known from a partial skeleton. This new taxon is a member of Archaeotrogonidae (formerly thought to be a group of stem-trogons, as their name suggests, later reevaluated as strisoreans), and not only provides new anatomical information on this group, but also suggests that they may be stem-nightjars. The absence of clear examples of Eocene stem-nightjars had been a conspicuous gap in the known fossil record of Strisores, so the common but enigmatic archaeotrogonids filling that space seems like a tantalizing possibility. It would also imply that my earlier hypothesis that the putative archaeotrogonid Hassiavis was a stem-owlet-nightjar is probably wrong, but that's the way science goes sometimes.

Shoulder and forelimb bones of Archaeodromus, from Mayr (2021).

The Naran-Bulak Formation gave us two more new fossil birds in 2021, the possible gruiforms Bumbanipes and Bumbaniralla. Bumbanipes appears to have been a specialized swimming form with morphological similarities to the limpkin (Aramus guarauna) and finfoots, whereas Bumbaniralla resembles messelornithids. Additional new entrants in the extinct gruiform department were the crane-like Palaeogeranos, based on a coracoid from the Oligocene of France, and the recently extinct rail Gallirallus astolfoi, based on a tarsometatarsus from the island of Rapa Iti in French Polynesia. Recent revisions in the generic assignment of recent rails have restricted the genus Gallirallus to the weka (G. australis) and sometimes the New Caledonian rail (G. lafresnayanus), in which case it wouldn't surprise me if G. astolfoi was transferred to a different genus in the future, perhaps Hypotaenidia. In fact, reassignment to Hypotaenidia was proposed last year for another recently extinct rail, the Chatham rail ("Cabalus" modestus), in one study on rail phylogeny.

No new extinct charadriiforms were named in 2021, but a study on the original illustrations used to describe the Moorea sandpiper (Prosobonia ellisi) supported synonymizing it with the Tahiti sandpiper (P. leucoptera).

There has still been no formal proposal to name the clade uniting Phaethontimorphae and Aequornithes, but last year the name Feraequornithes was coined for the group including most aequornitheans other than loons. As it happens, all of the extinct members of the "waterbird clade" that were named in 2021 belong to Feraequornithes.

The excellent fossil record of total-group penguins continued to provide, with new taxa in the form of the giant Kairuku waewaeroa, based on a partial skeleton from the Oligocene Glen Massey Formation of New Zealand, and the smaller Marambiornopsis, based on a tarsometatarsus from the Eocene Submeseta Formation of Antarctica. Perhaps more surprising was the description of a new fossil petrel based on a well-preserved skeleton, Procellaria altirostris from the Pliocene Tangahoe Formation of New Zealand.

Holotype of Procellaria altirostris, from Tennyson and Tomotani (2021).

Among pelecanimorphs, Eopelecanus was described as the oldest known stem-pelican based on a tibiotarsus from the Eocene Birket Qarun Formation of Egypt, whereas a revision of plotopterid specimens from the Paleogene of Washington State resulted in "Tonsala" buchanani being reassigned to Klallamornis.

Although not as many new raptors were named last year as there were in 2020, they were still pretty well represented. Arguably the most exciting was Archaehierax, known from a partial skeleton from the Oligocene Namba Formation of Australia. It was nearly as big as the wedge-tailed eagle (Aquila audax, the largest bird of prey in Australia today), and phylogenetic analyses (which have otherwise almost never been done on fossil accipitrimorphs!) suggest that it was a crown accipitrid, but not especially closely related to any living species.

Tarsometatarsus of Archaehierax, from Mather et al. (in press).

The other new fossil accipitrids of 2021 were also quite large species, Buteo dondasi from the Pliocene Chapadmalal Formation of Argentina and Buteogallus irpus from the Pleistocene of the Dominican Republic and Cuba. B. irpus is notably based on specimens formerly assigned to Titanohierax (now restricted to fossils from the Bahamas) and "Amplibuteo" woodwardi (now restricted to fossils from the United States). Its description further suggested sinking members of the genus Amplibuteo into Buteogallus, which had been foreshadowed in previous papers. Another new raptor was the owl Margarobyas abronensis from the Pleistocene of Cuba, a close relative of the poorly-known bare-legged owl (M. lawrencii) that still lives in Cuba today.

Among coraciimorphs, there was Ueekenkcoracias from the Huitrera Formation of Argentina, based on a partial hindlimb. It was described as a stem-member of the group uniting ground rollers and rollers, in which case it would be the first representative of this clade known from South America. However, a later study argued that Ueekenkcoracias more closely resembles the enigmatic Eocene bird Palaeopsittacus, in which case it may not be a telluravian at all. Probably less controversial are the three Pleistocene woodpeckers described from the La Brea tar pits (listed in order of decreasing body size), Breacopus, Melanerpes shawi, and Bitumenpicus.

The London Clay Formation had a good year as far as new fossil birds were concerned, with Tynskya waltonensis revealing new details about messelasturid morphology, though the phylogenetic affinities of these parrot-like birds remain mysterious. Perhaps even more remarkable was the psittacopedid Parapsittacopes, known from a very well-preserved partial skeleton that sheds new light on the anatomy of these stem-passeriforms. It further adds to the already impressive ecological diversity of psittacopedids, exhibiting a slightly widened beak that may have allowed it to feed on fruits and flying insects.

Skull of the holotype of Parapsittacopes, from Mayr (2020). (The print version of the journal retroactively dates the paper to 2020, but really, the paper was first released in 2021.)

Last but not least, a few fossil crown passeriforms were also described in 2021, the possible suboscine Crosnoornis, based on a nearly complete skeleton from the Oligocene of Poland, and the magpie Pica praepica from the Pleistocene of Bulgaria.

Type specimen of Crosnoornis, from Bochenski et al. (2021).

Saturday, January 1, 2022

Review of 2021

It appears that I've set a new record for an all-time low in annual post count on this blog (beating out last year). The main reason for this is pretty clear: 2021 was the year that I was supposed to turn in my PhD thesis. As of the time of writing, the deed has been done, so the main task left before I can earn my degree is to pass my viva (which will presumably be held within the next few months). I still need to do a fair amount of work to prepare my final thesis chapter for publication, not to mention think about what I'll do after I graduate, but the most grueling part of the PhD might just be behind me. Does that mean I'll resume a (more) regular posting schedule here? Well, I'd like to, but I'm making no promises...

However, writing up my thesis did not completely halt my other activities (which was a good thing... I think). On the academic side of things, I attended and presented at a few (virtual) conferences and co-authored a paper on online science outreach. I also received the immense honor of consulting for the educational studio Kurzgesagt on several of their projects, including a poster depicting the tree of life, a poster about the last non-avialan dinosaurs, a video on paleoartistic depictions of extinct animals, and their calendar for 2022 (which features prehistoric life). The research team at Kurzgesagt was an absolute pleasure to work with, and I came away from each project feeling like they made a very dedicated and honest effort to consider all of my feedback.

Kurzgesagt's "Map of Evolution" poster depicting the tree of life. This was the first project that I worked with them on and I'm very pleased with the final result.

My friend Joan Turmelle and I have continued to run our YouTube channel Through Time and Clades. Our biggest accomplishment so far, I think, is that we have completed both of the long-form lecture series that we set out to make: Joan's "Humanity, a Prologue" (covering human origins) and my "Dinosaurs, the Second Chapter" (covering crown bird evolution), with plans to release annual updates incorporating new research from our respective fields. Although I'd be the first to say that my videos are far from ideal in some ways (for example, I know that the multi-hour length of some episodes can be a real deterrent), don't let it be said that I haven't tried to make information on the evolutionary history of Cenozoic birds available in a reasonably accessible and comprehensive manner. We are also working on a companion website that will present the material from our lecture series in what we hope will be a more approachable format for some, though that is in early stages still. Another pleasant surprise for our channel last year was that we received an invitation to participate in Paleo Rewind, an annual collaboration among paleontology-focused YouTube creators to recap the year in paleontological discoveries.

A collage of title slides from my YouTube series "Dinosaurs, the Second Chapter", in which Joan and I discussed the origins, evolution, and diversity of crown-group birds.

Astonishingly, I was even able to start a new personal project last year! That was the blog New Dinosaur Alert, on which I write a brief post for each new genus or species of dinosaur described (including extant birds). Despite everything else going on, I've managed to stay on top of that blog for the most part, so I intend to continue it in the foreseeable future.

When I picked Velociraptor as the primary basis of the logo for New Dinosaur Alert, I did not know that the first Mesozoic dinosaur to be described in 2021 would be the velociraptorine dromaeosaurid Shri devi. That was a happy coincidence!

Lastly, I didn't expect to enjoy rewatching a show from my childhood as much as I did, but I'm glad that I was inspired to do so.

... And that's more than enough about me. Let's take a look at what 2021 had to offer in the world of maniraptoran research. As always, my coverage of papers about modern birds is necessarily going to be incomplete, so I put more focus on those that have more direct connections to paleontology, such as studies on anatomy, ontogeny, and higher-order phylogeny.

In January, oilbirds were found to disperse seeds across longer average distances than megafauna. A specimen of Pachystruthio from the Nihewan Formation was described. The skull morphology of phorusrhacids and the language-like capabilities of Japanese tits were reviewed. New studies came out on the hindlimb musculature of Nothronychus, the evolution of tooth shape in avialans and coloration and song in American warblers, and the phylogeny of neoavians and shearwaters. Newly-named maniraptors included the dromaeosaurid Shri devi, the Pliocene petrel Procellaria altirostris, the Eocene possible stem-coracioid Ueekenkcoracias tambussiae, the Pleistocene woodpeckers Bitumenpicus minimus, Breacopus garretti, and Melanerpes shawi, and the psittacopedid Parapsittacopes bergdahli.

Skull of the holotype of Parapsittacopes bergdahli, from Mayr (2020). (The print version of the journal retroactively dates the paper to 2020, but really, the paper was first released in 2021.)

In February, southern giant petrels were reported preying on Atlantic yellow-nosed albatrosses. Purported gastroliths in Bohaiornis were reinterpreted as mineral precipitate (as had been previously suggested). The mineralization of avian eggshells was reviewed. A tinamou egg from the Dolores Formation was described. Macrornis was redescribed as a possible phorusrhacid (though a dubious taxon). Male superb lyrebirds were found to mimic the sounds of mobbing flocks during courtship. New studies came out on the evolution of disparity in Mesozoic avialans, the diversification of avialans, atavisms in the avian hindlimb, the structure of kiwi eggshells, the phylogenetic position of Brontornis (favoring galloanseran affinities), recent extinctions of eastern North American birds, the phylogeny of galliforms and potoos, the ontogeny of locomotion in chukars and hindlimb muscle mass in Cabot's tragopans, skeletal pneumaticity in cuckoos, the biogeography of rails, the cranial anatomy of Spheniscus urbinai, the offshore behavior of Whenua Hou diving petrels, the relationship between male-biased sexual selection and speciation in passeriforms, and the use of alarm calls in yellow warblers. Newly-named maniraptors included the Oligocene passeriform Crosnoornis nargizia.

Displaying male superb lyrebird and spectrograms comparing the sounds of a mobbing flock to a lyrebird's mimicry thereof, from Dalziell et al. (2021).

In March, the phylogenetic position of Nesotrochis was evaluated based on ancient DNA, recovering it as a stem-flufftail. The regionalization of avian integument was reviewed. Soft tissues were reported from an ostrich from the Liushu Formation. Vegavis and Columba congi were redescribed. The name Feraequornithes was coined for the clade uniting most aequornitheans other than loons. A raven skull from the Pleistocene of China was described. New studies came out on the pelvic musculature of maniraptors, the tail anatomy of alvarezsaurs, the forelimb musculature of Nothronychus and aquatic birds, the evolution of dentition in avialans, the bone histology of Mirarce, the evolutionary versatility of the avian neck, the factors influencing the ease of puncturing avian eggshells, the endocranial anatomy of dromornithids and piciforms, the phylogeny of sea ducks and leaf warblers, the skeletal elements of penguin eyes, and the correlation between cooperative breeding and longevity in birds. Newly-named maniraptors included the troodontid Tamarro insperatus, the Alagoas screech-owl (Megascops alagoensis), the Xingu screech-owl (Megascops stangiae), the Alagoas black-throated trogon (Trogon muriciensis), and the messelasturid Tynskya waltonensis.

Phylogenetic tree showing the position of Nesotrochis, from Oswald et al. (2021).

In April, a juvenile specimen of Archaeorhynchus was reported. A large caenagnathid from the Hell Creek Formation, a giant euornithean from the Tremp Formation, birds from the Nanjemoy Formation, a pheasant from the Chi-Ting Formation, and a petrel from the Gaiman Formation were described. The evolution of the avian chondrocranium and species limits in birds were reviewed. Red blood cell mitochondria in birds were shown to produce more heat in winter than in fall. The ecological consequences of the extinction of Chendytes were investigated. The feather microstructure of male Ramphocelus tanagers was found to amplify their plumage signals. New studies came out on the evolution of eggshell thickness in birds (and other dinosaurs), the osteology of Unenlagia and Dryornis, the scapulocoracoid bone histology of Confuciusornis, the hindlimb muscle function and jumping performance of elegant crested tinamous, the craniofacial development of strisoreans, cultural evolution in great tits, the cranial musculature of the black-throated finch, and the diversification of tanagers. Newly-named maniraptors included the Pleistocene kiwi Apteryx littoralis.

Juvenile specimen of Archaeorhynchus, from Foth et al. (2021).

In May, research on the evolution of hearing and vision in theropods suggested that alvarezsaurs were likely to have been nocturnal. Larger neuron numbers were found to correlate with longer yawn duration in birds (and mammals). The global abundance of birds was estimated. The genetics of avian coloration were reviewed. Eggs of extinct emus and coprolites of little bush moa were described. Supposed tooth sockets in a juvenile gastornithid were reevaluated. Ant-following birds were found to have a higher probability of being infested by ticks. The genome of the California condor was published. Siberian jays were shown to use social knowledge to avoid being deceived. Great reed warblers were reported flying at extreme altitudes during migration. Great-tailed grackles were documented to be able to direct their eyes independently towards different targets. New studies came out on the evolution of the inner ear in maniraptors (and other reptiles), pectoral girdle morphology in paravians, competition as a driver of trait divergence in birds, convergent evolution in avian mitochondria, the effects of environmental lighting on avian eye evolution, the coracoscapular joint of birds, hybridization in kiwi, the morphometrics of wing shape in aquatic birds, the macroevolutionary stability of fruit-eating birds, the bone histology of Genyornis, migration speeds in common swifts, the correlation between speciation and plumage color evolution in hummingbirds, variation in echo parakeets, the phylogeny of fieldwrens and Afro-Eurasian sparrows, the persistence of song culture in zebra finches, the diversification of Afro-Eurasian buntings, and feather coloration in swallow tanagers. Newly-named maniraptors included the presbyornithid Bumbalavis anatoides, the Oligocene gruiform Palaeogeranos tourmenti, the Pleistocene magpie Pica praepica, the white-tailed cisticola (Cisticola anderseni), and the Kilombero cisticola (Cisticola bakerorum). The new genus Radinopsyche was coined for the caatinga antwren ("Herpsilochmus" sellowi).

Comparison of maniraptoran skulls with sclerotic rings highlighted, including the nocturnal Australian owlet-nightjar (B), the potentially nocturnal Haplocheirus (C), the diurnal Finsch's pygmy parrot (D), and the potentially diurnal Erlikosaurus (E), from Choiniere et al. (2021).

In June, isotope analysis was used to infer that the Chatham Island duck primarily ate marine invertebrates. An alvarezsaurid from the Qiupa Formation and a juvenile enantiornithean from the Jiufotang Formation were described. The life history of troodontids and divergent foraging strategies in hummingbirds were reviewed. Flocks of rock pigeons were found not to exhibit "selfish herd" behavior when under threat. Great snipes were reported to make extreme changes in flight altitude during migration. Malar stripe prominence in peregrine falcons was found to correlate with solar radiation. New studies came out on vertebral pneumaticity in Unenlagia, the quadrate of Longipteryx, the diversity of avian olfactory receptor genes, the development of avian wing digits, the effects of flight efficiency on dispersal distances in birds, the phylogenetic positions of the bee hummingbird and the Whenua Hou diving petrel, the diet of the tiny hawk, the systematics of sharp-shinned hawks, diversity patterns in tyrant flycatchers, perceptual inabilities in Eurasian jays, avian defenses against brood parasites, magnetic sensitivity in European robins, and the innervation of vocal muscles in zebra finches. Newly-named maniraptors included the enantiornithean Fortipesavis prehendens (based on a Burmese amber specimen, albeit one already previously described), the Eocene pelican Eopelecanus aegyptiacus, and the satin berrypecker (Melanocharis citreola).

Changes in flight altitude of great snipes, from Lindström et al. (2021).

In July, possible troodontid pellets were reported. A new specimen of Elmisaurus (suggesting that "Nomingia" is a junior synonym), the wishbone of Halszkaraptor, a troodontid from the Wulansuhai Formation, a new skull of Ichthyornis, and teratornithids from the Pleistocene of Argentina were described. The diet and bone growth variability in Mesozoic avialans and the theft of mammal hair by birds were reviewed. Potential evidence of molting in Archaeopteryx was disputed. The innovation and spread of bin-opening behavior in sulfur-crested cockatoos were documented. The origin of sweet taste perception in songbirds was investigated. New studies came out on the evolution of body size in alvarezsaurs, brain shape in birds, and sex chromosomes in paleognaths, the morphometrics of avialan limbs, patterns of skeletal integration in birds, factors correlating with extinction in Quaternary birds, the bone histology of North Island brown kiwi, phylogenetic conflict in galliforms, the effects of dark wings on flight efficiency in seabirds, the taxonomic status of the Canary Islands oystercatcher, wing morphing in raptors, the phylogeny of white-eyes and Campylorhynchus wrens, the origin of the Sulawesi babbler, and morphological signatures of introgression in Darwin's finches. Newly-named maniraptors included the dromaeosaurid Kansaignathus sogdianus, the Eocene galliforms Bumbanortyx transitoria and Bumbanipodius magnus, the Eocene gruiforms Bumbanipes aramoides and Bumbaniralla walbeckornithoides, the archaeotrogonid Archaeodromus anglicus (suggesting that archaeotrogonids are stem-nightjars), and the Eocene stem-penguin Marambiornopsis sobrali. The new genus Aptenorallus was coined for the Calayan rail ("Gallirallus" calayanensis).

Charts showing that the taste receptors of many songbirds respond to sugars, whereas those of suboscines (the two leftmost species) only respond to amino acids, from Toda et al. (2021).

In August, eogruids and ergilornithids were reinterpreted as stem-ostriches instead of gruiforms. The preservation of cartilage in Confuciusornis and Yanornis was examined. Male-like ornamentation in female white-necked jacobins was shown to function in reducing social harassment. Tool manufacture was documented in wild Tanimbar corellas. Passeriforms from the Miocene of Austria were described. An evolutionary trade-off between song and plumage complexity was found in antwrens. New studies came out on the role of locomotor modularity in avian origins, the bone histology of Yanornis and Gansus, the (limited) correlation between latitude and evolutionary dynamics in birds, lateral openings and depressions in avian back vertebrae, the cerebellar anatomy of birds, the relationship between avian sternal variation and locomotion, the challenges of flying through gaps for birds, variation in the postcranial skeleton of ostriches, the morphology of the femoral nutrient foramen and nutrient artery in chickens, the migratory routes of Arctic terns, the genomic bases of telluravian diversification, the mitochondrial genomes of condors, the reproductive benefits of cooperative polygamy to acorn woodpeckers, the sensitivity of Eurasian jays to cognitive illusions, the diversification of the common chaffinch species complex, and the evolution of the skull of the giant cowbird. Newly-named maniraptors included the unenlagiine Ypupiara lopai. The new genus Microspizias was coined for the semicollared hawk ("Accipiter" collaris) and the tiny hawk ("Accipiter" superciliosus).

Partial eogruid or ergilornithid skull (A) compared to those of a common ostrich (C) and a limpkin (a gruiform, D), from Mayr and Zelenkov (2021).

In September, a special issue on vocal learning in birds (and other animals) was published, including a report of vocal learning in musk ducks. Nuclear preservation in the cartilage of Caudipteryx was examined. An enantiornithean from the Jiufotang Formation, plotopterids from the Paleogene of the United States, and a specimen of Septencoracias from the London Clay Formation were described. Recent advances in avian genomics were reviewed. Evidence of humans harvesting and rearing cassowaries in the Pleistocene and early Holocene was presented. Island colonization was found to facilitate diversification in pigeons. Tool innovation by a disabled kea was documented. Cockatiels were shown to be able to sing in synchrony with human music. New studies came out on the postcranial osteology of Beipiaosaurus, the body mass of Anzu, dental replacement in enantiornitheans, the effects of topographic uplift on avian (and mammalian) speciation, the role of brain size and allometry in avian craniofacial evolution, the relationship between avian forelimb proportions and flight capability, phylogenetic patterns of ultraviolet vision in birds, the diversity of eggshell thicknesses in moa, signatures of coevolution between hosts and brood parasites in the avian visual system, the use of olfactory cues by hummingbirds, species delimitation in rockhopper penguins, the population genomics of kākāpō, the perception of virtual stimuli by kea, constraints on skull shape in passeriforms, introgression in suboscines, and the diversification of bulbuls in South Asia. Newly-named maniraptors included the non-pygostylian avialan Neimengornis rectusmim, the enantiornitheans Yuanchuavis kompsosoura and Yuornis junchangi, the Oligocene stem-penguin Kairuku waewaeroa, the Oligocene hawk Archaehierax sylvestris, and the Pleistocene hawk Buteogallus irpus (with "Amplibuteo" considered a junior synonym of Buteogallus).

Holotype of Yuornis junchangi, from Xu et al. (2021).

In October, parthenogenesis was reported in California condors. The avian altricial–precocial spectrum was quantified. Birds from the Miocene of Spain were revised. Birds from the Pleistocene–Holocene of Tajikistan and a galliform skull from the Makah Formation were described. Frugivory in raptors was reviewed. A new westward migration route was documented in Richard's pipits. New studies came out on the distribution of carotenoid pigments in birds (and other reptiles), the bone histology of birds, ecological drivers of avian eggshell wettability, the evolution of sex chromosomes in paleognaths and egg coloration in Australian songbirds, sensory adaptations in flightless birds, the phylogeny of tinamous and the spectacled thrush species complex, the histology of sutures in chicken skulls, embryo movement in avian brood parasites, the phylogeography of Chalcophaps doves, rates of hybridization in hummingbirds, the relationship between plumage coloration and colonization history in barn owls of the British Isles, correlations between morphology and migratory behavior in kingbirds, dispersal of fungal spores by tapaculos, the maintenance of evolutionary diversity in pale martins, and beak color polymorphism in Darwin's finches. Newly-named maniraptors included the troodontid Papiliovenator neimengguensis and the inti tanager (Heliothraupis oneilli).

Inti tanager, from Lane et al. (2021).

In November, adaptations for wing-propelled diving in dippers were documented. Aposematism in birds was reviewed. A South Island giant moa from Rakiura was described. Ecological shifts were found not to be strongly linked to morphological evolution in Australasian parrots. New Caledonian crows were reported investigating heated objects. Cavity-nesting birds were found to use feathers to dissuade nest usurpers. New studies came out on wing kinematics in Caudipteryx, the loss of functional diversity due to recent island bird extinctions, the evolution of wing feather molt in birds, phylogenetic analyses of avian mitochondrial data, phylogenetic conflict in paleognaths, divergence times of galliforms, the annual cycle of pallid swifts, factors influencing plumage ornamentation in male red-backed fairywrens, the phylogenetic position of the Sulawesi thrush, and the genetic basis of variation in redpolls. Newly-named maniraptors included the alvarezsaur Khulsanurus magnificus, the dromaeosaurid Kuru kulla, the Cretaceous euornithean Kaririavis mater, the Pliocene hawk Buteo dondasi, and the cryptic flatbill (Rhynchocyclus cryptus).

Brown dipper, photographed by Alpsdake, under CC BY-SA 3.0.

In December, evidence of iridescent plumage in Eoconfuciusornis was reported. Putative red blood cells preserved in Beipiaosaurus were reevaluated. An oviraptorid embryo preserved in a bird-like prehatching posture and a new specimen of Scandiavis were described. The fossil record of avian tracks and the morphology of the avian notarium were reviewed. Migratory birds were shown to be generally lighter colored. Ring-billed gulls were documented solving the string-pull test. Zebra finches were shown to use calls to influence mitochondrial function in their developing young. New studies came out on the evolution of feeding mechanics in maniraptors (and other coelurosaurs), iridescent feather nanostructures, and avian beak shape, the morphology of Borogovia, divergence times of Mesozoic avialans, the metabolism of Concornis and Iberomesornis, the ossification of avian respiratory turbinates, pathologies in Genyornis, the diversification of shearwaters, the feeding behavior of the Haast's eagle, the population history of barn owls in the Western Palearctic, the development of parrot pseudoteeth, the correlation between sex roles and sexual dimorphism in fairywrens, the phylogeny of whistlers, the safekeeping of tools by New Caledonian crows, the carpometacarpus morphology of mimids, and the migratory routes of citrine wagtails. Newly-named maniraptors included the dromaeosaurid Vectiraptor greeni, the enantiornithean Brevirostruavis macrohyoideus, the Cretaceous euornitheans Brevidentavis zhangi and Meemannavis ductrix, the Miocene duck Manuherikia primadividua, and the Pleistocene owl Margarobyas abronensis. The new genus Leucoptilon was coined for the white-tailed flycatcher ("Cyornis" concretus).

Skull and foot of Haast's eagle, from Te Papa, under CC BY 4.0.