Saturday, June 17, 2017

From One Diver to Another: There's Something Loony about Petralca

First things first: we now have approximately half of a baby Mesozoic maniraptor preserved in amber. What a time to be alive.

Onward to the main subject of this post. The seabird Petralca from the Miocene of Austria was first described in 1987 as an auk. However, this identification was (reportedly*) not justified by any anatomical observations and other researchers have subsequently suggested that Petralca may instead belong to a different group of diving birds, the loons (or divers, if you're British). Saying anything conclusive regarding Petralca has been difficult though, given that the holotype is not particularly well preserved. Some of the bones associated with the specimen are not even preserved directly, only evident as impressions.

*I cannot confirm this for myself, as the original description is in German.

The holotype of Petralca, from Göhlich and Mayr (in press).

To uncover more information about the specimen, paleontologists Ursula B. Göhlich and Gerald Mayr initiated further preparation of the fossil as well as casting of the preserved bone impressions. Armed with the new data they collected from these ventures, they were able to better compare the skeleton of Petralca to those of definite fossil loons as well as extant loons and auks.

There's no use beating around the bush: they found that Petralca is a loon. Every available skeletal element in Petralca that could be compared to those of loons and auks was more similar to those of loons. Of particular note is that the radiale (one of the wrist bones) of Petralca has a deep and prominent notch, which is a very distinctive feature of extant loons, but is absent in auks.

Comparison between the radiale of Petralca (B), a red throated loon (Gavia stellata, C), and a razorbill (an auk, Alca torda, D), from Göhlich and Mayr (in press).

In addition to clearing up its phylogenetic affinities, this reassessment of Petralca also provides clues to how it lived. Extant loons can swim quickly underwater by propelling themselves with their feet, whereas previously known early Miocene loons, such as Colymboides minutus, don't appear to have been so specialized for diving. The humerus of Petralca, however, had very thick bone walls, which is characteristic of diving birds (including both extant loons and auks). It looks like Petralca truly lived up to its claim as a diver.

Reference: Göhlich, U.B. and G. Mayr. In press. The alleged early Miocene auk Petralca austriaca is a loon (Aves, Gaviiformes): restudy of a controversial fossil bird. Historical Biology in press. doi: 10.1080/08912963.2017.1333610

Tuesday, June 6, 2017

A Small Basal Paravian Not Preserved as Roadkill? Enter Liaoningvenator!

Near the base of Paraves where we once had only Archaeopteryx as a model for the last common ancestor of modern birds and dromaeosaurids, we now know of a plethora of protobirds that likely occupy the same general region of theropod phylogeny. The Late Jurassic Tiaojishan Formation in northeastern China has proven particularly productive in this regard, its fine-grained lake deposits playing host to Pedopenna, Anchiornis, Xiaotingia, Eosinopteryx, and Aurornis, with rumors of more to come.

Many of these early paravians are known from essentially complete remains, have their soft tissues preserved in exquisite detail, and, in the case of Anchiornis, are represented by hundreds of specimens, to the point where their integument, musculature, and even coloration can be restored with unprecedented accuracy. On the flip side, however, these specimens tend to be preserved as flattened corpses similar to roadkill, making aspects of their skeletal anatomy challenging to interpret.

Another geological formation exposed in northeastern China, the Early Cretaceous Yixian Formation, is also known for lake deposits containing "roadkill" fossil specimens with finely-preserved soft tissues. However, the Yixian has other fossil beds that were formed by volcanic ash, and though the fossils found in these generally lack obvious soft tissue structures, they can preserve complete skeletons in three dimensions. A newly-named basal paravian has been recovered from these Yixian ash beds, making it a potentially quite significant find.

The holotype of Liaoningvenator, from Shen et al. (2017).

Liaoningvenator curriei is known from a nearly complete specimen, and at a glance it has some striking features. It looks extremely leggy, with very long lower legs and and feet for its size. Based on rough measurements done in ImageJ, the longest metatarsal is around 64% the length of the tibia, comparable to the ratio seen in some cusorial noasaurids such as Elaphrosaurus. Its forelimbs, conversely, are quite short, the humerus being less than 60% the length of the femur. (Compare Jinfengopteryx, another short-armed basal paravian, in which this figure is around 70%.)

The tail also looks unusually short and the life restoration provided in the paper appears to take this at face value, depicting the preserved length of the tail as its total length in life. The tail as preserved looks truncated, at least to my eye, so I, for one, am skeptical of this interpretation. (The authors do not comment on this issue one way or another.) Even so, it may not be farfetched to suggest that even the complete tail of Liaoningvenator was fairly short, considering that the phylogenetic analysis in the description finds it to be the sister taxon of Eosinopteryx, which has a relatively short tail with only 20 tail vertebrae in total. (For comparison, Anchiornis and Aurornis both have around 30 tail vertebrae.)

Speaking of phylogenetic affinities, the description recovers Liaoningvenator and Eosinopteryx as part of a clade of basal troodontids along with Anchiornis and Xiaotingia. If these findings are valid, Liaoningvenator would be the geologically youngest known member of this basal clade. It would also be the largest member of the group by far: using the Christiansen and Fariña (2004) method of estimating theropod body mass by femur length, Liaoningvenator is predicted to have weighed around 2 kg, whereas its Tiaojishan brethren have all been estimated as less than 1 kg. (On top of that, bone histology indicates that the holotype of Liaoningvenator was still growing at the time of death, though approaching skeletal maturity.)

That's all very fascinating if true. However, the phylogenetic relationships of these basal paravians are notoriously difficult to figure out. Anchiornis (the best-studied Tiaojishan paravian) has bounced between being an avialan, a troodontid, and neither ever since its initial description. In addition, it is not clear whether all of these protobirds really do clade together to the exclusion of other paravians. Perhaps we should also expect a tumultuous phylogenetic future for Liaoningvenator.

Alternative phylogenetic topologies for Paraves recovered by recent studies, based on Shen et al. (2017), Cau et al. (2015), Brusatte et al. (2014), and Foth et al. (2014).

I would be remiss if I neglected to mention that Liaoningvenator is not the only small basal paravian known from a complete, three-dimensionally preserved specimen. Mei is known from two such specimens, also found in ash beds from the Yixian Formation. Infamously, both of these specimens have been preserved in what appears to be a sleeping posture, which has led to jokes that Mei spent all of its time sleeping, despite efforts by paleoartists to depict alternative behaviors. Unlike Liaoningvenator, however, Mei has never been considered a close relative of the Tiaojishan "problem paravians", and is uniformly recovered as a troodontid.

Reference: Shen, C., B. Zhao, C. Gao, J. Lü, and M. Kundrát. 2017. A new troodontid dinosaur (Liaoningvenator curriei gen. et sp. nov.) from the Early Cretaceous Yixian Formation in western Liaoning Province. Acta Geoscientica Sinica 38: 359-371. doi: 10.3975/cagsb.2017.03.06

Sunday, June 4, 2017

ProgPal 2017 and New Walk Museum

Being in the UK opens up access to a whole host of paleontological conferences that I might not have considered attending before. Among these is Progressive Palaeontology (ProgPal), a conference run specifically by grad students for grad students.

This year's ProgPal was held in the city of Leicester. The first afternoon of the conference was host to a couple of workshops, but the first event I attended was the icebreaker later in the evening, which took place at the New Walk Museum.

The paleontology exhibit at this museum is particularly rich in Jurassic marine fossils. Here are the magical jaws of Liopleurodon, poised to clamp down on the head and neck of Muraenosaurus.

As is also visible in the previous photo, many of the fossils were accompanied by small models representing life restorations.

Direct evidence that plesiosaurs ended up on the menu of other sea creatures, in the form of bite marks on some of their bones.

The skull of Rhomaleosaurus.

An ichthyosaur showing off a massive sclerotic ring.

The New Walk Museum is home to some newly-discovered marine reptiles, such as this currently unnamed plesiosaur.

Here is Wahlisaurus, an ichthyosaur that was only described last year.

Naturally, there are also a few dinosaurs on display, including this model of a Neovenator skeleton.

The centerpiece of the hall is the sauropod Cetiosaurus.

Some Ediacaran fossils get in on the act, including several specimens of Charnia.

This is said to be the only solo portrait that David Attenborough has agreed to sit.

The museum has some interesting osteological material of extant species as well, such as this skeleton of a tree kangaroo.

The skull of an Indian (or Ganges) softshell turtle.

The main events of the conference, however, happened on the second day. These were, naturally, the talks and poster presentations. I didn't present anything, given that I had barely begun to do my Master's research by the time abstracts were due. Next year, perhaps.

Even so, the Bristol contingent was well represented (unsurprisingly, considering the size of our research group), accounting for around a quarter of the total number of both attendees and presentations given. (Yes, I counted.) Dare I say, this may have been a double-edged sword in some ways; I noticed that many of us Bristolians (myself included) tended to cluster together during free periods rather than taking the time to meet new people. Nonetheless, I did have quite a few worthwhile interactions with some non-Bristolian delegates, such as meeting with future collaborator Juan Benito Moreno for the first time. I also received some (positive) attention for my continuous livetweeting of the conference talks. (Livetweeting at SVP has given me plenty of opportunities for practice.)

Most of the talks were livesteamed and can be viewed here (though the sound appears to be out of sync towards the end of the recording). Institutional loyalties aside, my favorite talks include (in order of presentation):
  • Virginia Harvey's talk on using ancient collagen to study the fauna of the Cayman Islands (which deservedly went on to win best talk)
  • Alessandro Chiarenza's talk on modelling the ecological niches of dinosaurs in the latest Cretaceous of North America
  • David Marshall's talk on the paleoecology of Acutiramus (a Bristol talk, but the fact that he had to give a hand-drawn presentation due to spending his weekend trying to salvage a vandalized fossil site and still knocked it out of the park means he more than deserves a mention)
  • Andrew Jones's talk on phytosaur phylogeny (I especially liked his slide designs)
  • Alexander Askew's talk on Middle Devonian depositional dynamics in Spain (his declaration that "animal fossils are useless" doubtless being memorable to many)

On the whole, I had a great time at ProgPal and found it to be very effective at what it sets out to do (providing a relatively laid-back environment for early-career paleontologists to share their research). I intend to be back next year.

Thursday, April 20, 2017

London Zoo Part V: Reptile House

The last set of my photos from London Zoo (for the time being) come from its reptile house. Here is a king cobra, one of the largest venomous snakes.

A yellow-headed water monitor.

The Annam leaf turtle exhibit had a very interesting design, a stark presentation of some of the threats that this species is facing.

An Utila spiny-tailed iguana, another reptile critically endangered by hunting.

A collared tree lizard.

A Rio Fuerte beaded lizard, formerly considered a subspecies of the Mexican beaded lizard.

A Fiji banded iguana, a species with a lovely color palette.

Some Feae's flying frogs. I imagine they don't get to showcase the "flying" part much in this exhibit.

"Jeff Corwin can hear it, and so can Sir David Attenborough..."

A Philippine crocodile.

A puff adder (the original, not just any species of Bitis).

A Jamaican boa.

A gidgee skink, a sociable Australian lizard, as indicated by the accompanying sigaage.

The White's tree frog exhibit is decorated to reflect one of the habitats wild specimens are commonly found in.

A Sardinian brook salamander.

A black mamba, widely considered to be the fastest snake in the world.

Monday, April 17, 2017

London Zoo Part IV: B.U.G.S.

I get the impression that the B.U.G.S. (Biodiversity Underpinning Global Survival) building is one of the most highly acclaimed exhibits at the London Zoo, and it's not difficult to see why. Many of its displays use quite novel methods to showcase its resident animals, most of which (as indicated by the building's acronym) are invertebrates.

The photo below shows one of these novel exhibits, their leaf-cutter ant display. The ants can march between several tanks, including one from which they can harvest leaves and another which houses their nest. The paths they use to get from tank to tank are exposed out in the open, providing no physical barrier between the ants and visitors.

A pile of leaves harvested by the ants.

A couple of giant house spiders living in a mock-up bathroom.

A fen raft spider, a large wetland spider that hunts on the water surface.

There is even a spider walkthrough exhibit. Shown here is the corner of the walkthrough where social spiders reside.

Some chocolate millipedes. (They are not actually made of chocolate.)

Some weaver ants with their woven nest, which is made out of leaves and larval silk.

Some shiny jewel wasps, a parasitic wasp species that lay their eggs on cockroaches.

Some sunburst diving beetles.

Some critically endangered giant magnolia snails.

Some African giant mosquitoes, one of the few mosquito species in which the females do not need to drink blood to reproduce. The larvae prey on the larvae of other mosquitoes. Accordingly, they are sometimes used as a means of biological pest control.

A medicinal leech.

Saturday, April 8, 2017

London Zoo Part III: Lions, Tigers, and Gorillas, But I was Distracted by Other Things

One row of aviaries at the London Zoo houses some large birds, such as this woolly-necked stork.

An African harrier hawk and its lunch. This species is known for its "double-jointed" ankle, which helps it to reach into crevices to capture prey.

A striated caracara, a scavenging falcon from the Tierra del Fuego archipelago.

The London Zoo houses two species of penguin: Humboldt and northern rockhopper. Both are visible in this photo, but the Humboldt might take some searching to spot.

I tried to get some good photos of the blue-throated macaws, a species I hadn't seen before, but was unsuccessful.

A vicuña, the wild ancestor of the alpaca.

A newly-opened exhibit at the zoo showcases their lions. It's a good exhibit, but not even the fact that they had the Asiatic subspecies of lion (which I'd already seen at the Bristol Zoo) was enough to draw me away from this magnificent Rüppell's griffon vulture.

The Blackburn Pavilion is home to many species of tropical birds. Much of this building appears to be a walkthrough aviary and was thus closed during my visit, but a number of displays near the entrance remained open for viewing. Among its residents is this superb fruit dove (which is actually the name of its species and not merely my own description of it, apt though it is).

A hooded pitta.

A beautiful fruit dove (again, the actual name of this species), marred somewhat by the fine wire mesh.

A Mindanao bleeding heart dove.

A male crested partridge. I've found that the coloration of this species blends well into the lighting of forested environments, which makes getting clear photos of them fairly difficult.

A male red-legged honeycreeper. Not a close relative of the famous Hawaiian honeycreepers (which are finches), but a tanager.

An orange-headed thrush.

The Casson Pavilion is home to a rather miscellaneous variety of animals, including this large hairy armadillo. Armadillos are surprisingly active when they're awake; it took me many tries to get a photo that wasn't (too) blurry.

The pavilion provides indoor retreats for some animals that also have outdoor exhibits, such as these Malayan tapirs.

Despite signs claiming that this exhibit was empty, this rock hyrax was present.

A yellow mongoose. In the wild, this species may share burrow systems with meerkats and Cape ground squirrels.

Just outside, the tiger exhibit is accompanied by some humorous signage.

Gorilla Forest displays gorillas, as you can guess, but it has many other species of primates as well. This is a white-naped mangabey.

More importantly, it also exhibits some African bird species, like this green woodhoopoe.

A northern helmeted curassow, which is... South American, not African. Hmm.