Basic rundown of Choristodera, the “freshwater marine reptiles”

choristodera
a) Simoedosaurus lemoinei (modified from Sigogneau-Russell and Russell, 1978) –b) Ikechosaurus pijiagouensis (IVPP V13283) –c) Tchoiria namsarai (redrawn from Efimov, 1975) –d) Champsosaurus gigas (SMM P77.33.24): non-neochoristoderan –e) Cteniogenys sp. (Evans, 1990)–f) Lazarussuchus inexpectatus (Hecht, 1992) –g) Hyphalosaurus baitaigouensis (redrawn from Gao and Ksepka, 2008) –h) Monjurosuchus splendens (Matsumoto et al., 2007) –i) Philydrosaurus proseilus (Gao and Fox, 2005).

Choristoderes are a group of extinct reptiles I’ve talked about before. Now that several years have passed, I’m going to discuss them once more.

What are choristoderes?

hyphalosaurus_by_kahless28-d34r8g9
Hyphalosaurid choristoderes (and Manchurochelys) by kahless28

Choristoderes are a lineage of extinct, generally fully-aquatic reptiles. Beyond that, however, it’s very hard to tell.

See, it’s been a long standing debate whereas choristoderes are either archosauromorphs (the lineage of reptiles leading to archosaurs, including crocodylomorphs, pterosaurs and dinosaurs), lepidosauromorphs (the lineage leading to squamates and sphenodontians), or neither (more basal than either group). Similar debates have also plagued classical marine reptile groups like plesiosaurs and ichthyosaurs.

Part of the reason why figuring out where choristoderes fit in the phylogenetic tree of reptiles is because they lack definitive features affiliating them to either major reptile group. Their skulls vaguely resemble those of lepidosauromorphs, but lack the same quadrate configuration.

A particularly radical proposition was suggested by Miller 2004, in which choristoderes are linked to classical marine reptiles (ichthyosaurs and sauropterygians) under Euryapsida.

Personally, I lean slightly towards a lepidosaur identity, but further results may prove this hunch wrong.

 

When did they live?

hyphalosaurus_web

Hyphalosaurus by Matt Martuniuk.

Pachystropheus and Actiosaurus might represent examples of Rhaetian Triassic choristoderes. There is still some ambiguity; the former has also been regarded as a sauropterygian (Matsumoto 2009) or as a thalattosaur (Renesto 2005), while the latter was initially interpreted as a theropod, then an ichthyosaur before its proposed choristodere identity more recently (Mortimer 2010).

If both or at least one are choristoderes, they’re both fairly specialized marine reptiles and, in Pachystropheus‘ case, fairly derived, implying an even earlier origin. This is consistent with the long temporal gaps in choristodere fossil record history, the Lazarus taxon effect.

Otherwise, choristoderes are first known from the mid/late Jurassic. These Jurassic species are less specialized, being lizard-like freshwater reptiles. This would set a norm for the rest of the group’s existence: highly conservative “living fossils” whose lineages bear a spotty fossil record, attesting to both their resilience as well as avoidance of preservation. These include the complicated “Cteniogenys” assemblage, which first arose in the mid-Jurassic of Europe and North America, including the famous Morrison Formation.

By the Early Cretaceous, choristodere diversity in Asia undergoes an explosive radiation. Besides the more classical, salamander-like monjurosuchids, we also see the arrival of the long-necked hyphalosaurids and the long-jawed neochoristoderes, expanding the ecological niches available to the group.

Its unclear why choristoderes underwent such a sudden diversification. The local extinction of aquatic crocodilians due to colder temperatures might have triggered the evolution of neochoristoderes (Matsumoto 2010), but this doesn’t explain the evolution of hyphalosaurids.

From the mid-Cretaceous onward, there are no Asian choristodere remains, other than the largely understudied Eotomistoma (Carroll 1988). Hyphalosaurids disappear, but North America and Europe see the presence of both salamander-like species (“Cteniogenys”) as well as the diverse neochoristodere Champsosaurus. Both groups co-exist with a variety of aquatic crocodilians, though Champsosaurus apparently prevents long-snouted crocodilians from occurring in freshwater habitats (Matsumoto 2010).

Choristoderes survived the KT event, with Champsosaurus displaying dietary changes (Matsumoto 2015). It undergoes an adaptive radiation, producing several species including C. gigas, the largest known choristodere at around 3.5 meters long. It is joined by another genus, Simoedosaurus, which given its sudden appearance in the fossil record probably evolved from a Cretaceous Asian species.

Cretaceous “Cteniogenys” species are not known to have made it past the KT event. However, the genus Lazarussuchus debuts in the Paleocene of France, a much more basal animal with a ghost lineage quite possibly extending to the Jurassic or Triassic (Hecht 1992), unless they are related to the Cretaceous “Cteniogenys” species (Matsumoto 2013).

Neochoristoderes suddenly disappear in the medial Eocene, for no currently explainable reasons (see below). However, Lazarussuchus would continue to endure until the mid-Miocene, if not possibly until the Pliocene, when Europe grew too cold for these reptiles.

Unlike many clades, in which the most specialized members were the last representatives, choristoderes seem to have ended more or less as they started.

Fully Aquatic

hyphalosaurus_by_hyrotrioskjan-d460fje
Hyphalosaurus giving birth by Joschua Knüppe.

Most choristoderes were fully aquatic animals.

While some basal taxa like Lazarussuchus could be interpreted as amphibious, both monjurosuchids and hyphalosaurids have evidence of vivipary (Wu 2010) while in Champsosaurus only adult females have limbs robust enough to carry them ashore, while males and juveniles could not support their weight on land (Katsura 2007). As such, choristoderes as a whole appear to not have left the water much, if at all.

All known choristoderes possess laterally flatted tails, which were probably their main propulsion mechanism, with neochoristoderes also having paddle-like limbs. At least hyphalosaurids, monjurosuchids and neochoristoderes all have smooth skins with small, non-overlapping scales, though monjurosuchids do bear rows of scutes similar to those of modern alligator-lizards (Gao 2000). In neochoristoderes, the torso is dorsoventrally flattened, the gastralia are large and the ribs are short and massive, further adaptations for diving. There was a source mentioning pachyostic bones, but I can’t seem to find it.

Probably the most remarkable adaptation for life in the water are the nostrils. Aside from basal choristoderes like Lazarussuchus, which simply have receded nostrils, in more derived taxa the nostrils are fused and oriented towards the tip of the snout, allowing the animals to effectively use them as a snorkel, surfacing only the very tip of the snout while the rest of the body remained underwater (Acorn 2007).

Perhaps tellingly, the eyes are forwardly oriented. This is in contrast to amphibious animals like crocodilians and hippos, which have dorsally-oriented nostrils and eyes.

Cold Waters

Fig-2-Paleogeographical-distribution-of-Choristodera-during-the-Mesozoic-plotted-on

Palaeogeographical distribution of Choristodera in the Jurassic and Cretaceous periods.

Choristoderes as a whole have a pan-Laurasian distribution, ocurring in fossil sites in North America, Europe and Asia. There are two possible exceptions: basal choristoderes from the Jurassic/Early Cretaceous of North Africa (Haddoumi 2014) and possible neochoristodere teeth from Timor (Umbgrove 1949).

Other than these examples, however, nearly all choristodere remains occur in high latitudes. Although some do occur in sites that had a paratropical climate, most occur in temperate regions. Some Champsosaurus fossils even ocur in the high Arctic, in the Cretaceous of Greenland and the Eocene and Cretaceous of Axel Heiberg (Matsumoto 2010).

Thus, it can be seen that choristoderes tolerated colder environments, if not outright preferred them (Matsumoto 2014). Their ability to survive in colder climates in fact probably allowed them to diversify in the absence of crocodilians during the Early Cretaceous, when colder temperatures in Asia caused the local extinction of aquatic crocodilians (Matsumoto 2014). Both groups ultimately co-existed in warmer areas, however.

I previously speculated that neochoristoderes might have been endothermic, which fits well with their extreme speciation to an aquatic lifestyle. However, given that cold-tolerance was also present in more basal taxa, monjurosuchids and hyphalosaurids, I wonder if it endothermy was more widespread across the clade.

Ironically, cooling temperatures in Europe probably lead to the extinction of the group, as Lazarusussuchus probably survived until the glaciations.

Feeding

 

Figure-8-Palatal-dentition-of-Simoedosaurus-sp-SMNS-59026-a-e-and-Slemoinei-f-i.png

Palatine teeth in Simoedosaurus.

Basal choristoderes were probably generalistic feeders, ambushing small fish, crustaceans and other prey. Monjurosuchus has evidence of arthropod cuticle in its intestines, suggesting that it fed on aquatic arthropods (Gao 2000).

Hyphalosaurids were certainly specialized animals, bearing long necks. It’s likely that they were doing whatever the convergently similar plesiosaurs were doing, whatever that was. In particular, they appear to have preferred softer prey, which they probably hunted actively on the deeper areas of their lake environments (Gao 2008).

By contrast, the long-snouted neochoristoderes are much easier to figure out. These predators were doing what crocodilians, whales, gars and countless other large, predatory aquatic vertebrates do best: snatch up larger prey. Long, thinner jaws allowed them to accomplish this task with less drag.

While they are often compared to gharials, neochoristoderes may not be exactly analogous. Unlike other crocodilians, gharials have weak bite forces, rarely exceeding 497 N; they can tackle animals as large as goats, but they prefer small fish. By contrast, Champsosaurus had a bite force of 1194 to 1910 N, more comparable to that of crocodiles (James 2010). This may not have necessarily translated to a preference for larger prey, but it does convey a much larger degree of strength and speed when catching small fish.

Simoedosaurus dakotensis and Champsosaurus gigas, by contrast, have semi-brevirostrine snouts, and might have a diet more similar to that of crocodiles, feeding on not just fish but aquatic tetrapods like turtles and waterfowl and maybe ambushing terrestrial animals near the water. Notably, they co-existed with crocodile-like crocodilians like Borealosuchus (Matsumoto 2013 and 2014).

A neat feature choristoderes have is the retention of palatine teeth. Lost in various tetrapod groups like mammals, crocodylomorphs and dinosaurs, these teeth basically serve the role palatal grooves have in these groups, helping the animal to hold and manipulate food items in the mouth. In basal choristoderes these teeth are fairly generic, while in neochoristoderes they are more specialized, indicating a higher degree of food manipulation in the mouth. Such speciation might have evolved multiple times, as the simoedosaurid Ikechosaurus has palatine teeth more similar to those of non-neochoristodere choristoderes (Matsumoto 2015).

Through subtle differences in palatine teeth, we know that Champsosaurus changed its diet across the KT event, and that Simoedosaurus lindoei prefered softer prey than S. dakotensis (Matsumoto 2015).

Extinction

Lazarussuchus_NT_small

Lazarrusuchus, the last choristodere, by Nobu Tamura.

As mentioned previously, the extinction of choristoderes isn’t clear.

Competition with crocodilians is sometimes attributed to the demise of neochoristoderes, but both groups co-existed across the Late Cretaceous, Paleocene and Eocene of Laurasia and possibly Timor, and if anything neochoristoderes seem to have been dominant over long-snouted crocodilians in freshwater habitats (Matsumoto 2010 & 2014).

This also doesn’t explain the demise of hyphalosaurids, or of basal choristoderes in North America, North Africa and Asia.

Ultimately, European choristoderes such as Lazarussuchus appear to have died out due to glaciations in Europe.

Conclusion

There is still much I haven’t covered. Hopefully this will introduce you to these amazing extinct reptiles.

References

Ryoko Matsumoto; Shigeru Suzuki; Khisigjav Tsogtbaatar; Susan E. Evans (2009). “New material of the enigmatic reptile Khurendukhosaurus (Diapsida: Choristodera) from Mongolia”. Naturwissenschaften. 96 (2): 233–242. doi:10.1007/s00114-008-0469-6. PMID 19034405.

Silvio Renesto (2005). “A possible find of Endennasaurus (Reptilia, Thalattosauria) with a comparison between Endennasaurus and Pachystropheus“. Neues Jahrbuch für Geologie und Paläontologie – Monatshefte. Jg. 2005 (2): 118–128.

http://theropoddatabase.blogspot.pt/2010/06/actiosaurus-is-choristodere-not.html

R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274

R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698

R. Matsumoto and S. E. Evans. 2015. Morphology and function of the palatal dentition in Choristodera Article in Journal of Anatomy 228(3):n/a-n/a · November 2015 DOI: 10.1111/joa.12414

Hecht, M.K. (1992). “A new choristodere (Reptilia, Diapsida) from the Oligocene of France: an example of the Lazarus effect”. Geobios. 25: 115–131. doi:10.1016/S0016-6995(09)90041-9.

Matsumoto, R.; Buffetaut, E.; Escuillie, F.; Hervet, S.; Evans, S. E. (2013). “New material of the choristodere Lazarussuchus(Diapsida, Choristodera) from the Paleocene of France”. Journal of Vertebrate Paleontology. 33 (2): 319. doi:10.1080/02724634.2012.716274.

Ji Q., Wu, X.-C. and Cheng, Y.-N. (2010). “Cretaceous choristoderan reptiles gave birth to live young.” Naturwissenschaften, 97(4): 423-428. doi:10.1007/s00114-010-0654-2

Yoshihiro Katsura. 2007. Fusion of sacrals and anatomy in Champsosaurus (Diapsida, Choristodera), doi:10.1080/08912960701374659

Gao, K.; Evans, S.; Ji, Q.; Norell, M.; Ji, S. (2000). “Exceptional fossil material of a semi-aquatic reptile from China: the resolution of an enigma”. Journal of Vertebrate Paleontology. 20 (3): 417–421. doi:10.1671/0272-4634(2000)020[0417:efmoas]2.0.co;2.

John Acorn, Deep Alberta: Fossil Facts and Dinosaur Digs, University of Alberta, 07/02/2007

Hamid Haddoumi, Ronan Allain, Said Meslouh, Grégoire Metais, Michel Monbaron, Denise Pons, Jean-Claude Rage, Romain Vullo, Samir Zouhri, Emmanuel Gheerbrant, Guelb el Ahmar (Bathonian, Anoual Syncline, eastern Morocco): First continental flora and fauna including mammals from the Middle Jurassic of Africa, doi:10.1016/j.gr.2014.12.004

J. H. F. Umbgrove, Structural History Of The East Indies

Gao, K.-Q. and Ksepka, D.T. (2008). “Osteology and taxonomic revision of Hyphalosaurus (Diapsida: Choristodera) from the Lower Cretaceous of Liaoning, China.” Journal of Anatomy, 212(6): 747–768. doi:10.1111/j.1469-7580.2008.00907.x

James, Michael, The jaw adductor muscles in Champsosaurus and their implications for feeding mechanics, 2010-08-30T19:01:39Z

The Speculative Dinosaur Project: Pteranodontia

Besides Azhdarchidae, Spec also harbours another diverse clade of toothless pterosaurs. Pteranodonts are perhaps the most iconic clade of pterosaurs, well established in the pop cultural imaginarium, and while utilmately losing the spotlight in the HE, Spec’s pteranodonts are perhaps the most inventive and bizarre of the world’s pterosaurs.

Pteranodontia is the remaining branch of a prosperous Mesozoic branch of the pterosaur dynasty known as Ornithoehiroidea. Ornithocheiroids have quite possibly became the vertebrates most specialised for an aerial existence, having taken the already efficient pterosaur design and redefining it for life on the air: the shoulders ae higher than in other pterosaurs, the sternum keel is deeper – and, as predicated, the muscles associated with the downstroke are proportionally massive -, the humerus has developed a block-like form with large, warped dectopectoral crests, more robust and broad scapulocoracoids – in form forms no longer articulating with the notaria -, well developed notaria, an extensive rearrangeent of the flight musculature, and of course proportionally massive wings and small hindlimbs.
In pteranodontians, these traits were taken to their logical extreme, with pneumatisation becoming so extensive that even the hindlimbs are pneumatised, and rendering them the most pneumatised vertebrates to have ever existed. The toothed jaws present in other ornithocheiroids were instead replaced by a toothless, keratinous beak, forming a continuous sheet with their casque-like supraoccipital crests. Like in azhdarchids, the metacarpals I-III lost contact with the wrist bones, being now anchored at the end of the fourth metacarpal, smaller than the clawed digits themselves. The fourth metacarpal, on the other hand, has enlarged further, extending the already proportionally enormous wing, becoming some of the proportionally largest fourth metacarpals in any pterosaur and indeed any vertebrate. Some forms have taken these specialisations even further, developing inflexible scapulocoracoids, hatchet-shaped dectopectoral crests and a complete loss of the clawed digits of the hand, leaving only the wing finger.

Having possibly appeared as early as the Albian – if not deeper into the Lower Cretaceous -, pteranodontians gradually replaced their cousins in the Late Cretaceous, their domain beginning right after the systematic disappearence of their cousins, the ornithocheirids. The Santonian and Campanian periods are of particular relevance as the most iconic pteranodonts, †Pteranodon logiceps, †Geosternbergia sternbergi, †Geosternbergia maysei and †Dawndraco kanzai, dominate the flying vertebrate guilds of the north american seaways. At least a thousand †Pteranodon longiceps fossils are known, and many are so well preserved that for the longest time they proposed an important role in the understanding of pterodactyloids in general. An unique lineage of pteranodonts, the bizarre, nyctosaurids, also date back to this era, though they are much less common. Pteranodont remains before and after this span of time in the Santonian-Campanian are rare and often fragmentary, but they are found on a cosmopolitian scale, with remains occuring in not only North America, but South America, Europe and Japan as well (as well as a possible australian foot), and they span all the way to the Maastrichtian, both in the form of nyctosaurid humeri as well as well as specimens assigned to Pteranodontidae.

In Spec, Pteranodontia enters the Cenozoic with a bang, diversifying in the Eocene. Here, they witness global success and diversity, being the most common pterosaur lineage of the epoch, and the main component of the “Cenozoic Pterosaur Renaissance”. Besides characteristic marine piscivores, a variety of inland forms also appear, a few like †Messelosauravis having wingspans beneath 1.5 meters. Much like in earlier ornithocheiroids, a wide range of wing proportions can be seen: while all retain large wings, in many of these forms either the wing finger or the fourth metacarpal is dramatically shorter, showcasing the tendency for inland flyers to have shorter wings. In some forms, the clawed finger metacarpals are still long and connected to the wrist, which may either be an atavism or an ancestral feature, since the phylogeny of many of these pterosaurs is only now starting to be understood. Most retain the “normal” stork like beak, though some have serrations and strange jaw curvatures.

Pteranodontid fossils decrease drastically in number by the Oligocene, but this appears to be an artifact of preservation rather than a genuine feature, as the diversity achieved in the Eocene still occurs well into the Miocene; Pteranodontidae itself, however, appears to have disappeared in the Oligocene. This period witnesses a dominance of nyctosaurs in particular, which become some of the most common pterosaur finds in contrast to their Maastrichtian rarity. Other pteranodontians are mostly found on terrestrial/freshwater settings, a situation that goes on the present day. Unlike azhdarchids, which witness an evident shift in diversity by the Plio-Pleistocene, it’s difficult to evaluate how pteranodont diversity coped with the glaciations, given the rarity of non-nyctosaur remains. These seem largely unaffected, and middle-Pleistocene New Zealand sites seem to imply a sudden diversity increase at least during this era.

Besides the adaptations discussed above, pteranodontians are also weird among pterosaurs for other reasons. They lack a “gizzard”, relying exclusively on their stomachal acids for processing prey. Some pteranodonts have atypically long tails for pterodactyloids, with biforcated terminal caudals, in some cases supporting small structures thought to be similar to the diamond-like tail “fins” of early pterosaurs like †Rhamphorhynchus. Their nasonantorbital fenestrae are rather small for pterosaurs, providing them with iconic shallow, stork-like beaks. Their crests do not have keratin extensions, being entirely composed of bone sans the keratinous integrument envelope, as opposed to the elaborate keratin crests of other pterosaurs, including some azhdarchids; nonetheless, in some animals these bony crests can grow to be proportionally quite large and bizarrely shaped. All pteranodontians have rather wide pelvic cannals in females, and indeed some forms have become fully viviparous with true placentas.

Impundulu (Keranopterus scopus)

The skies of Africa, southern Europe, Arabia and Madagascar are crossed by a rather curious pteranodont. With white pelage and black wing membranes, beak and crest – which is rather small, barely noticeable unless under a closer inspection -, the Impundulu has an average wingspan of 2.5-3 meters, males generally being larger than females, though otherwise not much different beyond a slightly larger crest. The Impundulu, like all ornithocheiroids, has proportionally large wings, but they are smaller than those of the more characteristic pteranodonts, with metacarpal and wing finger proportions closer to that of the long gone istiodactylids and boreopterids, perfect for flight in inland settings. More curiously, the Impundulu still has it’s first metacarpal connected to the wrist, a trait unique among pteranodonts, as well as non-pneumatic hindlimbs, which might imply that this is a rather basal animal. Indeed, genetic analysis place it outside of the rest of Pteranodontia, implicating that it is in fact he most basal member of this clade. Similar animals are found in the Eocene and Oligocene in Asia and North America, and extinct forms of Keranopterus are known from the late Miocene of Europe.

The Impundulu favours generally dry open areas, particularly steppes, though it can also be found on wetter environments on occasion. Spending most of it’s time in the air, it nonetheless forages on the ground, feeding on squamates, beetles, small mammals, small dinosaurs and many invertebrates from snails to scorpions are also predated upon. This similarity in diet to HE’s Geronticus has labelled these pterosaurs as “Otherworld Bald Ibis”, though unlike the birds the Impundulu does not probe the ground with it’s beak outside of already made holes and crevices, preffering to capture prey on the surface substrates. With typical ornithocheiroid hindlimb proportions, it is a less efficient terrestrial walker than the azhdarchids it shares it’s habitat with, though like them it also has small, compact feet, as opposed to the larger and spread-toed pes of the average pteranodont. It roosts in cliffs, either near or miles away from it’s foraging grounds, gathering in large flocks. Occasionally, these flocks are targetted by large avisaurs, but generally only terrestrial predators attack these animals when foraging, and life expectancy can be quite high. The Impundulu is serially monogamous, with couples forming every breeding season to protect the eggs and then disbanding when the flaplings hatch. The “nest” is a pile of decaying vegetation in the cliffs, which is tended by both parents as to control the temperature within the eggs. After the flaplings are born, they generally remain in the cliffs for a while, foraging on insects and lizards that live there, before moving on to lowland areas.

ANATOCHASMIDAE

Anatochasmids are a lineage of pteranodontians of about 10 species occuring across the world’s freshwater bodies, known from as far back as the Paleocene – though genetic data seems to place their origin much earlier into the Cretaceous. It’s been suggested that these are perhaps living members of Pteranodontidae, though their nyctosaurid like dectopectoral crests and rather more generalised habits seem to imply another placement in Pteranodontia. With similar wing proportions to those of the Impundulu, these animals appear to occupy a similar ecological niche to that of their long gone boreopterid relatives, trapping small aquatic animals in ridges in their beaks while they swim in rivers, lakes and wetlands. However, unlike their dead cousins, these animals are actual filter feeders, opening and closing their jaws to allow water to flow in and other of their beaks in order to trap multiple prey at once. In a way, they are basically like large dabbling ducks, and indeed Spec does not have the same diversity of dabbling ducks that developed in HE’s Miocene, presumably due to competition with these pterosaurs.

Granduke (Anatochasma fritzli)

The Granduke is a presence on the wetlands of most of Africa and southern and western Eurasia, occuring from the Mediterranean to the Ganges and into the Caucasus’ inland seas, with occasional breeding populations making a living as far East as the Baikal and as far west as Brittain; most of the extremes in it’s range usually occur in breeding and wintering seasons, when these pterosaurs migrate huge distances and are taken to explore new territories. With a 4.5 wingspan and standing at 1.7 meters of height, the Granduke may not be huge by pterosaur standards, but it is the largest living anatochasmid, and certainly a very impressive animal, on the air or on the ground. Occuring in a variety of freshwater habitats, from estuaries to swamps to highland lakes, it tends to preffer large lakes, where it can gather to quite large flocks. With a wide beak, it displays very well the anatochasmid filter feeding method, pumping water in and out of it’s snout in biting motions, trapping crusctaceans, insects, tadpoles, small fish and other small prey in the pecten-like ridges.

The Granduke has a white pelage, gray wing membranes and a pink bill. It’s crest, barely distinguishable in colour from the beak, is rather oddly positioned for a pteranodontian, forming a disc in the jaw tip, not too dissimilar from the crests of the typical ornithocheirid. In males, this crest is predictably bigger, but it is also wider and has a more robust internal support, instead of the usual spongy casque inner bone. More bizarrely yet is how these crests are used; contrary to what one may think, there is very little animousity between adult males, which are content with foraging alongside each other. They instead have a much more sinister purpose: males strike at females with these crests, ramming their robust jaw tips against them, bruising them until they are too weak to fight against anatid-style violations. At times, groups of males may gang up, isolating females from groups and beating them with the crests in all directions, causing severe bruises. In the breeding season, females may even be rounded up in groups, guarded by several males that prevent escaping and help subdue the rape victims.

This seemingly barbaric method is observed occasionally in HE dolphins, but the Granduke seems to have taken it to it’s logical extreme, the tendency for forced intercourse having evolved into a grotesque herding strategy. How and why these pterosaurs switched from male rivalry in lek systems to cooperation in herding and gang-raping the opposite sex is unknown, though the presence of similar crests in some extinct relatives may suggest it has began as far back as the Eocene. It has been suggested that this is simply the logical conclusion of the sexual selection expressed in rape strategies, where an arms race of male and female strength determines if the male’s genes will be passed on to the next generation.

Although adult males do not act violently against each other, as sexual competition is detrimental in a scenario where cooperation is vital, younger males that haven’t yet reached sexual maturity are fair game, often raped and rounded up alongside females. After they reach sexual maturity, they may join males of a specific group, or move elsewhere. The Granduke is also not limited to animals of it’s same species: several animals, from ducks to juvenile mokeles, may also be gang-raped and often die of internal organ fracture.

Thankfully, these strategies only occur in the first month or so of the breeding season: afterwards, males stop herding females, which are free to go away and move to the safety of larger flocks, if they aren’t too wounded. They gather in large numbers in sandy bars and river banks, burying their eggs, often alongside crocodiles and turtles. At least a few females remain nearby, helping to fend off predators. After an incubation period that may take up to three months or so, the juveniles are born, enough nests incubating at the same time to ensure predators only get a small fraction of the flaplings. They stay near the adults, even migrating alongside them, foraging on aquatic insects and small crustaceans. Half an year later, they’re about a quarter of the adult size, growing slowly for about three years or so until they reach sexual maturity, and continuing to grow for about three more years.

Trausduke (Anatochasma moorei)

A smaller cousin of the infamous Granduke, the Trausduke usually doesn’t grow above a two meter wingspan. It is certainly a large animal among the freshwater flyers of the continent, however, and occupies an almost identical ecological niche across both Americas. With a black and orange pelage, the Trausduke also bears a similar crest, and engages in the same violent sexual behaviours, generally occuring in Spring in either hemisphere. Compared to it’s Old World relative, the Trausduke is more migratory: part of the year, the population has a more northern range towards North America and is rarer in South America south of Pantanal, while during another part of the year the focus becomes reversed, disappearing from most of North America north of Florida and extending it’s range southwards into Patagonia. Such shifts are seemingly a recent phenomena, as the glaciations presented a more narrow band for these shifts, and indeed it appears that it was largely sedentary during the glaciations, occuring mostly in subtropical America.

Minkaduke (Purpurorhamphus eyrensis)

The Minkaduke is Australia’s dominant anatochasmid, found all over the continent’s wetlands, but most often seen in the southern great lakes, which in Spec are still sizeable, permanent waterbodies, unaffected by the extreme drying in HE; it often also frequents coastoal bays and lagoons. The Minkaduke is the last of it’s genus, of which several species are known in Australia since the Oligocene, bearing a rounded, thick supraoccipital crest, present only in the males. The pelage is mostly of a cream colour, of a darker yellow in the head, with a black line on the torso and black shoulders; the wing membranes are of a gray tone, and the beak and headcrest bear a distinctive violet colour, achieved through porphyrins not too dissimilar to those present in the Hastazhdarcho azhdarchids. Reaching a wingspan of three meters, it is among the largest non-azhdarchid flyers in the continent, and the massive congregations of these animals darken the skies above wetlands. Breeding occurs year round, males forming temporary territories that may cover entire waterbodies, though usually restricted to a patch of shoreline in large waterbodies. Passing females lay their eggs on a mound of decaying vegetation the male has built, which is tended by him for around three months until the flaplings hatch. During this period the male guards the “nest” viciously against even large rhynchoraptors and carnocursorines, all the while checking the mound’s temperature and removing and adding vegetation in accordance to the eggs’ ideal incubation temperatures, only occasionally taking breaks to filter feed.

Clamduke (Tachyeromimus sudamericum)

Occuring in southern South America, the Clamduke frequents both large lakes as well as coastoal waters. It has deviated from the usual filter feeding norm of it’s relatives by becoming a specialised molluscivore, it’s pecten like ridges having become larger and thicker, less useful as sieves but helping in cracking bivalve shells open. Unlike dsungaripterids and the Dupap, and like most pteranodontians, the Clamduke can swim very well and thus has easier access to molluscs, foraging either by dabbling or even shallow diving, depending on the water’s depth. While occuring in lakes all over South America south of Pantanal, it only occurs in the Atlantic shores, the chilean coastline being instead occupied by the oviraptorian Waldo, which occupies a similar niche; neither animal occurs in southernmost South America. Coloured in a rich black and white pelt and an orange beak, the Clamduke has a small supraoccipital crest as well as a disc like crest in the tip of it’s bill, present only in the female; in a rare case among pterosaurs, the female is the one who forms harems, defending a territory where the smaller, less ornamented males tend the eggs, buried by the female on sandbanks and bars. Generally, all it takes is the male’s loud screams to drive the attention of the larger and more powerful female, which can reach a wingspan of 3.6 meters, fighting off most predators.

NYCTOSAURIDAE

The most morphologically derived clade of Pteranodontia, and indeed Ornithocheiroidea as a while, nyctosaurs have transformed their bodies further. Besides losing the fingers and metacarpals aside from the wing digit. the fourth metacarpal has also elongated further, being the proportionally longest of all non-azhdarchid pterosaurs, which combined with the wing finger it often renders their wings not only the longest in proportion to the body size of any animal, but also allowing very high aspect ratios, making nyctosaurs potentially the best soarers that have ever lived. The wing finger itself now only has three phalanges and is further stiffed, while the dectopectoral crests have become unwarped but rather hatchet like, offering a wider surface of attachment for the wing muscles. Tendons in the arm have become mineralised, an unique feature among pterosaurs, allowing the wing to remain locked in a fixed position as the animal soars continuously, and decreasing the danger of arthritis so common among old aged pterosaurs. The scapulocoracoids do not articulate with the notarium, forming a stable support for flight muscles, though at the expense of water based launching.

Nyctosaurids are for the most part pelagic animals, spending most of their lives flying above the sea, never touching land unless under rare circumstances. Spec’s first living nyctosaur specimens come from carcasses washed ashore in Tasmania, and since then reccords of living animals have increased sporadically, but they are still incredibly cryptic. Nyctosaurids can most often be seen in large congregations of other marine animals, be them schools of prey driven to the surface by marine predators, or the nocturnal migrations of deep sea organisms to surface waters. Unlike other pteranodontids, nyctosaurs are poorly suited for water based take off, and thus they are forced to forage aerially, much like HE frigatebirds and the contemporary enantiornithes known as jarilos. Various techniques have been observed in nyctosaurids, from typical dip feeding to impressive feats of hoovering, remaining more or less stationary on the air and simply picking up prey from the water surface, to angled strikes at high speed. Nyctosaurid diets are well documented in their carcasses, a wide variety of small animals having been found on the stomachal contents; while usually generalised, nyctosaurid diets appear to be largely focused on crustaceans and cephalopods. Kleptoparasitism has also been documented, with the pterosaurs targetting seabirds of various sizes, pecking them until they vomit their cargo. A few carcasses have also been found with petrels and other small seabirds inside the esophagus or stomach, implying that occasional predation on these birds occurs.

So well specialised for powered flight and soaring, nyctosaurids usually spend most if not all of their lives in the air, sleeping while flying like some of the most aerial birds, and uniquely they are among the few vertebrates that mate in the air. Landing is very well thought to almost never happen in most species, and should it happen the animals are virtually helpless on the ground, the immense wings being too long to coordinate with the hindlimbs when walking, though still competent swimmers even if water-based launching is very hard at best. Indeed, unlike most seabirds, nyctosaurs have completly cut off all ties to land, being viviparous, having developed a quite sophisticated placenta. This has the side effect of having much shorter “litters” than most pterosaurs, somewhere between one and four flaplings, but surprising at least some species seem to have reasonably high population densities; so far, it’s unknown if nyctosaurs engage in parental care, though no rookeries or similar nesting grounds have been identified, and many specimens are rather young animals, though all thought to be above six months in age; no significant deviations from the usual pterodactyloid growth rates have been observed thus far. Like all ornithocheiroids, their casque-like crests do not bear keratin extensions, but since the Cretaceous that these animals have provided rather impressive headgear.

Being the dominant marine pterosaurs in the Cenozoic, nyctosaurs had a rather impressive presence in Oligocene and Miocene marine fossil sites, being far more common than the few Cretaceous specimens. The Plio-Pleistocene seems to have done wonders to this clade, as the productivity of krill and other prey has increased in th globe’s oceans – though genetic studies imply a genetic bottleneck around the late Pliocene -, and Pleistocene subfossil beach sites in New Zealand’s Southern Island have provided thousands of specimens, mostly belonging to several species of Monochiropterus and Kerguelenorhamphus, presumably coinciding with an especially common presence in the southern oceans. As of this, at least 26 species have been recognised, and more seem to be on the way.

George’s Nycto (Monochiropterus georgi)

The first nyctosaur specimens discovered on Spec were three washed up carcasses of these animals in Tasmania. Since then, wild animals have been found across the world’s southern oceans, with occasional sightings as far north as Scottland, being one of the most well documented nyctosaurs. Largely of a light, silvery grey with a predictable bright white underside, the George’s Nycto displays a yellow and black beak, and males have an impressive headcrest of similar colours, albeit arranged in stripes and strange, axe-like dots. Roughly as long as the headcrest of the iconic †Nyctosaurus, it is rather distinct in shape: rather than a branched, antler-like structure, it is rather laterally flat and with a very large surface area, forming a structure similar to a much enlarged, reversed †Pteranodon longiceps crest. Hollow and filled with delicate, spongy internal support, it is occasionally seen broken in some specimens, and being reserved to the males it clearly bears no sigificant aerodynamic function. The wingspan usually ranges around 2.3 meters, with males being larger: the largest reccorded specimen had a wingspan of 3 meters. As always, the wings are massive in proportion to the rather small body.

The George’s Nycto is seemingly nocturnal, very rarely seen during the day and uncommon even in twilight hours, being most often encountered well after the Sun has set. Stomach contents show a variety of cephalopods, including baleen-whale larvae, as well as krill, with only occasional fish remains, mostly small or soft bodied like eel larvae. The reccords of the animal foraging in the wild show that it uses dip-feeding, flying over the ocean surface and quickly grabbing prey with it’s jaws. These reccords show a wide variety of strategies, from quick, angled attacks to hovering over the ocean surface, from the usual grabbing with neck flexion to angled strikes that “spear” the prey in the lower jaw, initially mistaken for skim-feeding. These attacks tend to have impressively high success rates, something poorly understood as the only other known nocturnal aerial dip-feeders are [spec]bats, and they use ecolocation to find prey. No ecolocation has been reccorded in nyctosaurs, which may suggest either their eyesight is so sophisticated that they can make out prey in dark water, or they have some sense currently undetected. Like most pterosaurs, it seems to have a poor sense of smell, and it doesn’t respond to oil baits like petrels, aside from following seabirds. Kleptoparasitism has been observed, with the pterosaurs grabbing small seabirds or other nyctosaurids by the tail or hindlimbs and shaking them, or pecking them in the flanks or throat, until they regurgitate their load. No actual predation has been so far observed, though one carcasse of a male was found with a storm-petrel inside of the esophagus.

Carcasses of gravid females suggest that these animals give birth to two or four flaplings. The juveniles’ wings are already well developed like those of most flaplings, but such a small brood size is atypical for supposedly superprecocial sauropsids. It is possible that nyctosaurs raise their young, or that this small offpsring production is a consequence of the needs of powered flight – though, since nyctosaurids seemingly almost never land, the main weight-saving pressure in flying vertebrates is absent. For a while, it was thought that this small brood size kept nyctosaur populations small, allowing the high diversity of species with so little competition, though studies on the population dynamics of the George’s Nycto and other species has shown that they have expected population sizes for pelagic foragers, at times even more common than some seabirds. Juvenile animals have been found in the wild, but they’re generally no younger than 6 months, where they’re more or less a third of the adult size.

Less mysterious, however, is what leads to the flaplings. At specific times of the year, these pterosaurs gather in large numbers at locales rich in prey stock, such as emerging blooms of krill. These concentrations generally are represented by a thousand or so individuals, some of the largest observed concentrations of nyctosaurids in the world – most impressively, these massive flocks almost vanish during the day, the animals dispersed at higher altitudes as they sleep, quickly descending once night settles in. Males fly well above the rest of the flock, honking loudly and performing incredible aerobatics. During this period, they forage very little, and indeed many males work and starve themselves to death, falling into the sea and never rising again. About a third of the amount of carcasses of these animals appear to be males that died this way, and it’s not uncommon to see mosarks, kronosharks and other large marine predators attending to these congregations, feeding on the fallen males. Should a female be impressed, she flies in the male’s direction and both rise up in the air. They mate in the air, the male displaying a long penis about a third of the creature’s wingspan and much longer than the torso, only as much as a fifth of it entering as the animals hover. Mating itself lasts only a few seconds, and the animals may mate continuously for two hours or so, before the female flies away and the male quickly refuels, before returning to aerobatics. The female may mate at most two more times, before she flies off, away from the massive flock and into the usual loneliness of the open sea.

White Nycto (Monochiropterus alba)

A smaller relative of the Goerge’s Nycto, the White Nycto has an average wingspan of around 1.4 meters as a full grown adult. One of the few polar pterosaurs, the White Nycto forages primarily in antarctic waters in Summer months, being commonly sighted on Antarctica’s shores, and even occasionally roosting on flat clifftops and icebergs, a rare behaviour for a nyctosaur; it is usually cathemeral, and during Antarctica’s Summer the White Nycto is obviously entirely diurnal. As the name implies, it has a thick, white pelage, which extends into the wing membranes; it’s beak is of a greenish tone, with yellow beak tips. Feeding primarily on krill, it can hoover excellently above the sea, picking the crustaceans from the water surface; it may also swoop down quickly. Mating during on Antarctica during the Summer, the males develop a rather small headcrest, of a vivid crimson and yellow colour, gathering in large flocks where the males exhibit themselves to exhaustion and mate in the air like it’s relatives. Mating on Antarctica during the Summer, the White Nycto winters in the open waters of the South Atlantic, Pacific and Indian Oceans, on average reaching as far north as the Galapagos. Despiste their Summer coastoal habits, the mystery to how nyctosaurids spend the first 6 months of their lives hasn’t been solved, and it is thought they give birth during Winter months on yet unidentified locations.

Tristan Nycto (Monochiropterus sudatlanticum)

At an average wingspan of two meters, this pterosaur occurs mostly in the waters of the Atlantic south of Ascension and north of the Falklands. White with a gray wing upperside and pink beaks, it displays little sexual dimorphism compared to it’s cousins, the males bearing only a small, round crest; nevertheless, the engages in similar mating gatherings. More piscivorous than it’s cousins, it has a prefference for pachycormid young, though it will happily consume most fish, cephalopods and crustaceans that it can swallow, and it frequently harasses seabirds and other pterosaurs for easy meals.

California Nycto (Monochiropterus septentrionalis)

Monochiropterus as a whole is more widely distributed in the southern hemisphere, the California Nycto being an exception to this rule. While it indeed occurs with large frequency in the western north american coast, it is also a frequent forager in Hawaiian and Asian waters, and it of course forages all over the pelagic Pacific between them, far away from shore; it seemingly preffers eastern Pacific waters during the Summer, generally moving westerwards during the Winter. With a wingspan of 2.4-2.9 meters, it bears a black pelage with a bright yellow beak and white wing membranes, white spots lining it’s flanks; the male develops a large white crest similar to that of the George’s Nycto in shape and size. Stomachal contents show that it feeds primarily on cephalopods, foraging primarily at nighttime. It Hawaii it has also been reccorded preying on bird chicks, swooping them from unguarded nests on the wing, usually during the day, picking also newborn seaturtles in this way; indeed Hawaiian individuals may very well predate on small insular animals during the day and forage on surface-venturing deep sea squid at night. Conversely, juveniles of this species seem to be a common target for jarilos and other acrobatic large seabirds. Mating gatherings occur both in Spring and Autumn, the former in the eastern Pacific, the latter in western waters.

Risso Nyctos (Kerguelenorhamphus spp.)

Once thought to represent a single species, Kerguelenorhamphus griseus, Risso Nyctos migght actually be a more complex group of species, with four main genetically distinct populations being identified. The original, first found as a moribund specimen in Île de Castries, has a western Indian Ocean distribution, found from western India to South Africa, being most common in waters to the east of Madagascar. Another population, informally assigned as K. cooki, occurs in waters around Australia, New Zealand, Melanesia, Micronesia and Indonesia east of Borneo; populations in the Bay of Bengal, eastern Indian Ocean and the central indonesian islands are thought to represent a mosaic of both populations, with interbreeding strongly suspected, mudding the waters fruther. A third population occurs in the Mediterranean, the Atlantic around Europe – including the North Sea – as far north as Iceland, as westwards as the Azores and as southernly as the Canaries, with infrequent occurences in the Black, Baltic and Caspian seas as well as the Atlantic north american coast. A third population occurs in the Pacific shores of the Americas, from Antarctic waters to the Pacific Northwest; populations occur in the Caribbean, which may either represent a mosaic between the Pacific and European populations, or an independent population of their own. Another mosaic/independent population scenario occurs in the waters around Japan and the Phillipines. Subfossil remains occur all over the world, but they first occur and are most common in New Zealand, particularly in South Island, and it has been thought that Kerguelenorhamphus is part of a southern radiation of nyctosaurids alongside Monochiropterus, though genetic testing seems to place these two genera at opposite sides of the Nyctosauridae phylogenetic tree. At any rate, while Monochiropterus has dominated southern oceans, Kerguelenopterus has spread across the world.

Risso Nyctos are rather variable in their habits, but they generally preffer to forage in waters off the continental shelf, in basically “shallow pelagic” environments; they forage cathemerally, predating on cephalopods and fish. Sometimes they forage on more coastoal waters, even occuring sporadically on lagoons and estuaries or even inland, but they generally remain at least a mile away from the shore. They are largely of a light gray with a white underside, bright orange beaks and rectancular headcrests that extend from the middle of the beak to the forehead. Variations on this design occur: K. griseus has a completly gray head pelage and black beak tips, while the face is white on K. cooki with gray extending from the neck to the pelage on the base of the lower jaw, having no black beak tips, and the headcrest extending into the supreoccipital, albeit lowly. The “european” population has a gray “mask”, a black upperjaw, and the crest restricted to the beak, while the eastern Pacific population is very similar to the european population except for having both jaw tips black, with the black area of the lower jaw extending well into the middle mandible. The “japanese” population has a white head like K. cooki,, but no supraoccipital crest and an entirely black lower jaw. No significant sexual dimorphism has been reccorded in any of the populations but the european one, where the head crest is absent in the females.

Breeding concides with Spring months in either hemisphere. Unlike Monochiropterus nyctosaurids, Risso Nyctos don’t form large congregations. The exact means of mate selection are unknown, but pairings are common during breeding months, implying serial monogamy for brief periods of time.

Ropen (Eucryptovolans novaeguineaea)

The seaways of Micronesia and Indonesia are frequented by nyctosaurid that is cryptic even for the standards of it’s clade, being very rarely sighted alive. With a wingspan of two meters, the Ropen is a nocturnal animal, almost never encountered during even twilight hours, foraging in both open waters and sheltered bays and estuaries for mostly invertebrate prey. It is coated in a light brown pelt, with similarly dull wings and and black beak; it has no headcrest, and indeed males look almost identical to females. However, this pterosaur has mastered a trick only two other groups of amniotes, the very unrelated baskervilles and tuataras, have managed: bioluminescence. At night time, the wings of the males glow with an eerie blue light, radiated from most of the membrane, and it is thought that these animals use this spectacular method instead of headcrests to determine worthy partners. Most spectacularly, unlike the baskervilles, the Ropen does not rely on a symbiotic relationship with fungi, producing it’s own luciferase reactions, though it is thought that they may use chemicals present in their prey, like marine glowing worms. This technique is not without some liability, however, as the blue light seems to affect the male’s melatonin production, and may endanger him to cancer. It seems, this dangerous mate selection mechanism favours indeed the strongest and healthiest males.

Besides it’s bioluminescence, the Ropen is also weird for a nyctosaur in regards to it’s still articulating scapulocoracoid. It has been suggested that it may represent a very basal member of it’s clade, and indeed it doesn’t appear to be closely related to the other nyctosaurids.

Giant Nycto (Giganokeanopterus magnificens)

The North Atlantic has a rather poor diversity of nyctosaurs, but it does compensate in having the largest species. With a wingspan of 6.7 meters, the Giant Nycto is the largest living non-azhdarchid pterosaur, and the marine flyer in the world, far overshadowing the seabirds it coexists with. White with brown patterns and a black head, the Giant Nycto has a rather unimpressive headgear, with it’s crests being a mere supraoccipital spike, golden in colour alongside it’s beak. It feeds primarily on fish, following other marine animals to schoals pressed against the surface, grabbing prey as large as small ichthyodectids. It also easily attacks seabirds, and indeed the Giant Nycto is a common menace in Summer rockeries, attacking adult birds leaving or returning to their nests, and occasionally snatching up chicks on the wing. On rarer occasions, it may swoop down to capture terretrial prey on the beaches and clifftops, and it may also scavenge, though doing this is rather tricky and energy taxing as the animal forages always on the wing.

Like Monochiropterus nyctos, it gathers in large open sea congrgations in the breeding season. However, these affairs are more violent, with males attacking each other on the wing, spearing and striking wih their bills. Many are fatally wounded and fall into the sea, and even triumphant males generally are too weak to mate more than once or twice at a time, though usually effectively as the penis has barbs, which remove the sperm of competitors. As usual per nyctosaurids, no animals younger than six months are known, and these are already large enough to be protected from most aerial animals besides adult Giant Nyctos. The Giant Nycto is the last member of a genus that has been prevalent in the world’s oceans during the late Miocene and Pliocene, with it’s closest relatives being the much smaller Prionopterus nyctos, distributed across the world’s oceans.

(More species can be envisioned)

Pteranodontidae

Geosternbergia/Pteranodon sternbergi flying away with an egg, courtesy of Disney.
Geosternbergia/Pteranodon sternbergi flying away with an egg, courtesy of Disney.

For such popular prehistoric animals, Pteranodon and it’s brethren are rather surprisingly rare not only in pop culture – most “cartoon pterodactyls” with the iconic headcrests are frankly never actually called Pteranodon, so… -, but also in documentaries. I literally can’t think of any appearences by these pterosaurs in documentaries aside from both Sea Monster documentaires – the BBC series and the National Geographic movie -, and amusingly enough the only accurate depiction of these animals on CGI is by Disney’s infamously generic movie Dinosaur. While Quetzalcoatlus has rather unsurprisingly been featured more frequently thanks to it’s massive size and actual co-existence with Tyrannosaurus, when much less popular pterosaurs like Nemicolopterus and Eosipterus have had their shot at (admitely very horribly depicted) documentarydom, you know something’s really, really wrong.

Regardless, pteranodontids have started to captivate me, ironically given the amount of “new”, more exotic pterosaurs being discovered and the fact that they represent what pterosaur lovers have long struggled against, the stereotypical seabird like animal. However, pteranodontids are fascinating and beautiful animals on their own right, and while Pteranodon longiceps is possibly one of the most well understood pterodactyloids known, other members of this clade are woefully understudied, adding a layer of mystique to a supposedly characteristic clade.

The Ultimate Flying Animals

Pteranodon longiceps taking off.
Pteranodon longiceps skeleton taking off.

Pteranodontidae is part of a clade of specialised pterodactyloids known as Ornithocheiroidea, which quite possibly may represent the vertebrate clade most specialised for an aerial living. With high shoulders, warped dectopectoral crests, large sternal keels, extensive pneumatisation of the skeleton, well developed notariums, broad and robust scapulocoracoids and proportionally massive wings – correspondent to porportionally small hindlimbs -, as well as casque-like crests without fibrous bone and thus keratinous extensions, ornithocheirioids stand well amidst other pterodactyloids as oddities, and indeed they are thought to have diverged early in monofenestratan evolution.

In pteranodontids and their close cousins, the nyctosaurs, these specialisations kept being perfected to a further extreme: skeletal pneumatisation became so extensive that even the hindlimbs are pneumatised, the sternal keel among the proportionally largest of all pterosaurs, the wings have become even larger via the extreme elongation of the fourth metacarpal, and the toothy maws characteristic to pterosaurs – very impressive in ornithocheiroids like ornithocheirids themselves – were replaced by a toothless, keratinous beak. The metacarpals aside from the one supporting the wing finger became astonishingly short, barely more than the digits themselves, becoming attached to the end of the fourth metacarpal, a trait also shared with azhdarchoids, though whereas this is a specialisation for flight or the inevitable consequence of the thinning of the I-III metacarpals is unknown. Nyctosaurs went further, adapting the dectopectoral crest and scapulocoracoid anatomy to stranger forms and loosing the non-wingfinger digits altogether, but pteranodontids kept conservative to ornithocheiroid anatomy in these regards, except for the development of strangely long tails with biforcated end caudals.

Because of these extreme anatomical changes and the rather sudden appearence of these animals in the middle-Cretaceous, how did these pterosaurs evolve is a mystery. The most probable explanation is that pteranodontids are actually highly derived ornithocheirids, rendering Ornithocheiridae paraphyletic – indeed, Guidraco has been suggested as being a sister taxon to Pteranodontidae. Another possibility suggested to me in a conversation was that pteranodontids evolved from animals akin to boreopterids, which already show a few pteranodontid like traits like the long tails, and have rather weak, fragile teeth, probably of little use besides preventing small fish from escaping, which could rather rapidly be replaced by a keratinous, toothless beak. Starting as inland foragers, these early pteranodontians would then have expanded into marine ecosystems, replacing ornithocheirids or simply filling their vacant niches – with pteranodontians reaching their golden age not long after ornithocheirids largely disappeared from the fossil reccord, this may be a blatant case of ecological replacement.

In turn, it is equally possible that Nyctosauridae may be a derived clade within Pteranodontidae, rendering the latter polyphyletic, though with little examination of the relationships between the known taxa this is of course difficult to attest. It is also likely that nyctosaurids are simply an entirely different branch of Ornithocheiroidea, having diverged from other ornithocheiroid branches and simply converged with pteranodontids, though both clades do share several traits in common at the exclusion of other ornithocheiroids.

How Many Are There?

American Pteranodontidae by Matt Martyniuk.
American Pteranodontidae by Matt Martyniuk.

Traditionally, Pteranodontidae is composed of two named genera, Pteranodon and Ornithostoma. The former, the first known north american pterosaur, is one of the best known flying reptiles, at least 1000 specimens having been uncovered, many of which astonishingly compete. The latter, on the other hand, is very fragmentary, and it’s identity as an actual pteranodontid is nothing short of controversial, with at least two specimens attributed to it being recovered as azhdarchoids, though the holotype may be a genuine pteranodontid.

Pteranodon has had many species attributed to it in historical times, but since the nineties that only two species have been recognised: P. longiceps, with it’s iconic thinner crest, and the hatcht crested P. sternbergi. However, more recently two new genera have been distinguished from Pteranodon (Kellner 2010): P. sternbergi became it’s own genus, Geosternbergia (composed, in turn, of both G. sternbergi and G. maysei), while a P. longiceps specimen was elevated to Dawndraco kanzai. These two genera haven’t gone uncontested, however (Mark Witton 2013), and indeed they may very well be all within Pteranodon, as they don’t have many significant anatomical differences beyond crest and beak shapes. The genera/species have been informally suggested to form a temporal species complex, with one form replacing another, but all co-exist in the Niobrara Formation at seemingly the same time period.

Remains attributed to Pteranodontidae and even Pteranodon itself have also been found in other parts of the world, including Japan, Australia, Argentina, Brasil, Romania, France and Sweeden (Allt om Vetenskap 2012, Barrett et al 2008), spanning all the way from the late Albian to the Maastrichtian. Little work has been done on these non-north american pteranodontids, but they clearly indicate that the clade was both cosmopolitian and long lived, lasting for at least 37 million years from the Lower Cretaceous to the very end of the Mesozoic. This indicates that Pteranodontidae, alongside Nyctosauridae, Azhdarchidae and whatever the hell Navajodactylus, Piksi and the New Zealand pterosaur are, was among the last pterosaur clades to have ever existed, perishing only due to the KT event.

Giant Flyers

It couldn't look at a giraffe in the eye, but it could certainly bite your head off.
It couldn’t look at a giraffe in the eye, but it could certainly bite your head off.

While we know little about how large most pteranodontids grew, the north american forms at least were positively gigantic animals. Pteranodon longiceps reaches a wingspan of 6 meters, while Geosternbergia maysei might reach a wingspan of 7.25 meters, being among the largest flying animals to have ever existed: only giant azhdarchids like Hatzegopteryx and Quetzalcoatlus, the teratorn Argentavis and the ornithocheirid Coloborhynchus can claim larger sizes; pelagornithid seabirds and some ornithocheirids come close in size. The exact weight of these animals is unclear, but based on estimates of birds and bats – as exposed to historically “super light weight” nonsense -, a healthy full grown animal should weight around 93 kilos, mass effordlessly vaulted from the ground by the pterosaurs’ powerful forelimbs. Even without the unique pterosaurian launching mechanism, however, such sizes would be affordable anyways, as the pelagornithid seabirds and teratorns show, contrasting previous studies on weight limits for flying animals.

Most impressively, only the males reached these massive sizes. Females remained much smaller at wingspans of around four meters or even lower, implicating that the males’ gigantism was the result of extreme sexual selection, observed nowhere else among pterosaurs (though possibly due to the lack of such a large sample in many other species), though the possibility of simply different ecological niches occupied by each gender cannot be dismissed. Animals generally reach large sizes because they can, and being the dominant flying vertebrates over the Late Cretaceous oceans, with seabirds remaining considerably smaller and even rarer in several cases, and with nyctosaurids and other marine pterosaurs consistently also smaller and less common, pteranodonts presumably wouldn’t have been forced into larger sizes by competition by either birds or other pterosaurs, as the “average” females show.

As Coloborhynchus was indeed larger than the largest known pteranodontids, it’s unlikely that the animals’ unique adaptations contributed much to their large sizes. Indeed, the even more specialised nyctosaurs are generally rather small animals, on average with 2 meter wingspans, excepting “Nyctosauruslamegoi‘s estimated 4 meter wingspan, which might implicate that these adaptations for flight have ironically also restrained their sizes.

Geosternbergia sizes by Matt Martyniuk
Geosternbergia sizes by Matt Martyniuk

In general, the flight style of pteranodontids has been probably the most well documented among pterosaurs. It’s almost universally agreed that pteranodonts were oceanic soarers akin to modern seabirds, specialised in utilising the marine wind currents and thermals for gliding effordlessly for hours with minimal wing flaps. Their wings are exceptionally long, with high aspect ratios and indeed comparable in shape to those of modern soaring seabirds like albatrosses, if wider (keep reading, though). The sternum nonetheless has a fairly deep keel for pterosaur standards, and the wing musculature appears to have been quite extensive and robust, certainly allowing for powerful flapping when needed, perhaps even more so than in modern seabirds. Like all pterosaurs, pteranodontids were probably capable of altering their wing shape, using the muscle fibers in the patagia to contract and expand the membrane, allowing wider wings when relaxed and thinner wings when contracting, something particularly useful when transitioning from stactic soaring to dynamic soaring, and vice versa, allowing for effective soaring in both marine and inland settings.

As stated previously, pteranodontids extended the pneumacy of their ornithocheiroid ancestors, with even the hindlimbs being pneumatised. While some bones may be rendered lighter with pneumacy, it has been made clear again and again that animals with hollow bones are not significantly lighter than non-pneumatised animals, and indeed Coloborhynchus managed larger sizes with less pneumatisation. Pneumacy instead seems to actually serve to make the bones stronger, allowing them to gain larger sizes simply by expanding the airsac into the bone like an air baloon with minimal extra resources wasted, and with density equally distributed. As such, pteranodontids had thicker bones elements than many other pterosaurs, allowing for both more extensive wing muscle attachment sites as well as a skeleton even more apt to deal with the pressures of powered flight.

Both femurs have roughly the same density, yet the pneumatisation in Pteranodon's allows it to be much more robust.
Both femurs have roughly the same density in proportion to the animal’s body, yet the pneumatisation in Pteranodon’s allows it to be much more robust.

It seems that pteranodontids, like most ornithocheiroids, were not very good at walking, with rather short hindlimbs in proportion to the massive forelimbs. The long fourth metacarpal was probably very close to the maximum limit for effective terrestrial locomotion: any longer, and the forelimbs wouldn’t have been able to be used as effective propellers in coordination with the hindlimbs. Worth of note is that Pteranodon was the main focus of early hypothesis about pterosaur terrestrial locomotion: all the insane ideas, from dragging itself by it’s belly to upright bipedality, were attributed to this pterosaur, before quadrupedal walking was realised.

Over The Sea

With adaptations for oceanic soaring, generally found in marine formations and with north american specimens associated with fish remains, including regurgitated fish scales, it’s clear that pteranodontids followed in the lines of ornithocheirids and rhamphorhynchines as the classical piscivorous pterosaur model, soaring over the Cretaceous’ oceans and feasting on teleosts, cephalopods, crustaceans and other small marine animals in the manner of seabirds, both contemporary to them and modern. However, unlike many earlier aerial piscivores, pteranodontids might have been especially like seabirds, landing on the ocean surface and swimming instead of catching prey on the wing: unlike dip feeding pterosaurs, pteranodontids have small anterior cervicals, indicating that their neck was not robust enough to withstand the stresses of dip feeding, nor that it had neck musculature strong enough for carrying the necessary neck motions. Instead, pteranodontids have characteristics thought to have expressed adaptations for water based launching, with reinforced scapulocoracoid systems, robust shoulders and possibly expanded and reconfigured downstroke muscles, allowing these animals to catapult themselves out of the water in a series of row-like motions from the arms. Additionally, pteranodontids have fairly large feet, as opposed to the miniscule feet of other ornithocheiroids, and are associated with small prey items, as opposed to the general tendency of aerial dip feeders of capturing large, easy to spot prey.

Once in the water, pteranodontids would have captured their morsels in a myriad of ways. Perhaps they simply dipped their long beaks, capturing prey near the surface as they floated, or maybe they dabbled like modern ducks and many seabirds, capturing prey slightly deeper whilst still floating in the surface. Maybe they selectively picked prey with their bills, or passed their beak through the water, closing it quickly as soon as they felt prey. Maybe they weren’t restricted to the surface after all, and could dive, aquaflying with their powerful forelimbs; when even modern albatrosses can dive for at least as deep as 6 meters, this is a serious possibility. Maybe they even plunge dived. When individual seabird species have varied foraging techniques, it’s likely pteranodontids employed many of these too. Dawndraco has a longer, thicker bill than other known pteranodontids, so it may have foraged differently. At any rate, pteranodontids in general have long, stork like bills, like the long bills in modern tropical/subtropical seabirds, allowing them to reach prey at deeper depths.

In at least north american pteranodontids, only adults and subadults are found in the fossil sites, thought to have once been the sea bottom of the open ocean. This means that juvenile pteranodontids probably had coastoal or even terrestrial habits, and only when they reached a large enough size did they venture into the open sea; by contrast, young nyctosaur fossils indicate that these pterosaurs started their pelagic lifestyle very early on. Some non-north american remains, like the romanian pteranodontid, occur in non-pelagic fossil sites, and indeed these animals probably landed, on land or on sea, to roost like most modern seabirds, unlike the seemingly perpetually aerial nyctosaurs.

It’s made very clear that pteranodontids were sexually dimorphic animals, with males being much larger than the females and having more impressive head crests and distinct overbites. Sex has been determined by the width of the pelvic cannals, which in the smaller, pratically crestless individuals is much wider, which is consistent with a female interpretation (though, once again, I give this warning). Much like modern pinnipedes, pteranodontids probably were lek strategists, the animals gathering for brief periods of time on coastoal rookeries where males would have maintained an harem of females. As to be expected from pelagic animals, potential mates would perhaps rarely encounter each other, so these short lived affairs would prommote extensive sexual selection, with larger, more flamboyant and more agressive males being favoured. The overbite in particular may imply the use of the beak in interspecific combat between males, though this is of course yet unattested.

Another, more dark interpretation is that, like modern mallards and dolphins, pteranodontids probably focused on a more direct form of sexual selection, with the males being larger and stronger to forcefully subdue females; mallards in particular are also exceptionally flamboyant in the males, and given the extensively documented cases of males ganging up on females (and other males) to mob rape them, such signalling might have been used to attract fellow males rather than repell them.

Regards of the strategy, it’s very unlikely males had much to do with the offspring. Or the females, for that matter, as like most pterosaurs baby pteranodontids would probably have been superprecocial, though parental care can’t at the present be dismissed. Female pteranodontids would have laid their eggs on sandy beaches like modern sea turtles, but given the soft eggshells of pterosaur eggs, ovovivipary is also a possibility, something of particular consideration given the wide pelvic cannals of these animals. The young, if not raised by the parents, presumably would have lived on the beach or in inland habitats for the few months of their lives, before growing large enough to venture into the sea.

Pteranodontids as a whole probably were the heirs to the ornithocheirid empire that lasted for over 63 million years until the Cenomanian, spreading across the world in the final stages of the Cretaceous. They seemingly were a common component of the world’s marine faunas, and probably ecologically analogous to their ornithocheiroid predecessors, cementing the domain of toothless pterosaurs after the Turonian. After their own 37 million year dynasty, they met their own extinction in the KT event, they were probably replaced ecologically by the pelagornithid seabirds, which only recently have become extinct.

Iconic Geosternbergia rookery picture by Mark Witton.
Iconic Geosternbergia rookery picture by Mark Witton.

Conclusion

For a group of pterosaurs bearing the most famous pterosaur of all, Pteranodontidae still has a lot of mysteries to unveil, all the while invoking a sense of wonder matched by few living animals. They were not as big as azhdarchids and didn’t have tall necks, but they were still massive animals with wings casting immense shadows over ancient seas, so similar yet so alien compared to modern seabirds. They were quite possibly the very last inovative pterosaur design, having appeared seemingly well after other known pterosaur clades were well established, and they reached impressive dichotomies in sizes between members of their own species.

Above all, they are an iconic symbol of pterosaur research.

Pteranodon longiceps by Mark Witton. without the person attached.
Pteranodon longiceps by Mark Witton. without the person attached.

Homophobia in the paleontological community?

Khaan mckennai specimens reffered to as "Romeo and Juliet". Putting aside the godawful ignorance about the play's point, there's no traits in the specimens that assign them to a specific gender.
Khaan mckennai specimens reffered to as “Romeo and Juliet”. Putting aside the godawful ignorance about the play’s point, there’s no observed traits in the specimens that assign them to a specific gender. People literally just saw two specimens together and decided it was an heterosexual mating pair.

One thing’s great about science: it only cares about accurate results. Nothing else matters: your religion, your race, your gender is nobody’s concern, so long as you follow proper procedures, conduct ethical experiments and not clouding your results with bias. White, straight men still happen to be the more famous and visible faces of modern paleontology, but many of the more field changing discoveries still rightfully belong to female paleontologists like Teresa Maryańska, whose Gobi desert expeditions have offered our first understanding of asian pachycephalosaurs. And, as with all sciences, it’s international reach pretty much grants representations by most cultures and ethnicies; my own home country has it’s own share of voices, most notably Miguel Telles Antunes.

Paleontology is particularly beneficient in that it is relatively invulnerable to political meddling; aside from the studies on human ancestry, there is no major government interest in affecting paleontological studies negatively. After all, the conclusions about an ornithocheirid specimen from the Cambridge Greensand are very unlikely to damage or boost the Prime Minister’s career – as oposed to, say, research on fossil fuels -, so the brittish government won’t bother to affect pterosaur studies in any way, besides maybe cutting funds if they feel like it. Only creationists enjoy a capacity to cause damage to paleontological studies, and their range of influence is thankfully relatively minor in the western world, only affecting the aforementioned human ancestry studies.

So, if paleontology is not only pragmatic and inclusive in relation to gender, culture and ethnicy, but also generally unaffected by non-creationist political meddling, why am I making a post about a form of prejudice, homophobia, being present in the paleontological community? Sadly, because it found a way, as usual.

Hide The [Paleontologist] Lesbians

Franz Nopsca, an infamous hungarian paleontologist (and nobility) who shot himself and his lover. Throught his life, the Baron had struggled with his sexuality, which he considered "unnatural", a tragically ironic conclusion that could have been avoided if there weren't scientific biases against the study of animal sexuality back then.
Franz Nopsca, an infamous hungarian paleontologist (and nobility) who shot himself and his lover. Throught his life, the Baron had struggled with his sexuality, which he considered “unnatural”, a tragically ironic conclusion that could have been avoided if there weren’t scientific biases against the study of animal sexuality back then.

Because science is again pragmatic and result focused, paleontologists are best known for their research; in theory, it’s a meritocratic affair, with the individuals being more famous the more groundbreacking their studies are. And, as with all meritocratic affairs, personality comes second to work: Robert T. Bakker has more limelights due to his research than he does due to being a pentecostal, for example. In theory, at least, it’s a fair system that encourages a focus on the actual subject than the researcher: you can be honest and open about yourself, so long as you are both competent and productive.

In theory. In practise, this tends to be rather arbitarily and hypocritically enforced. Putting aside employment practises and discrimination, how much visibility a researcher gets is variable. Some, like the aforementioned Bakker, are key components of the paleontological community’s public perception, but other researchers with just as much productivity and groundbreacking research are outright shoved into the background, like Kristina Curry Rogers, who is to Titanosauria what Bakker is to Morrison Formation theropods, yet rewarded far less. This is why, despiste the number of female paleontologists out there, they are obscure enough to need posts like this to gain the recognition they deserve. For a system that supposedly congratulates the inovative researcher, it sure attempts to not be such.

This, of course, leads us to the obvious, unconfortable conclusion: homosexuality is a taboo among paleontologists. Most LGBT researchers are not particularly open about their sexuality, and while it’s hard to demonstrate homophobic pressure, as it stands their visibility is reduced to an extreme minimum. Perhaps the best barometer of this is none other than Baron von Nopsca, to whom we owe the first understanding of the Hateg Island dwarves, early hypothesis about dinosaur sexual dimorphism – albeit rather erroneous -, early studies on the bird-dinosaur connection, and perhaps even the concept of palaeobiology, yet he is very, very sheldomly listed among the paleontological pioneers of his time. You’re more likely to hear about his murder-suicide than his relevance in his field, a bitter reversal of what being a scientist should entail.

Lets pretend it doesn’t exist in Nature

At the very least 30% of albatross couples are female/female. When was the last time you heard people talking about similar percentages in pseudodontorns?
At the least 30% of albatross couples are female/female. There’s no reason to think similar numbers wouldn’t have occured in extinct archosaurs, yet all discovered [supposed] mating pairs are reffered as heterosexual, with various levels of contrivance.

Homosexuality is overwhelmingly present in nature, being recorded in basically all types of multiple-sexed organisms, from fruit flies to cetaceans. Birds in particular have had their same-sex mating behaviour well documented: entire seagull and waterfowl colonies/flocks have been registered to be composed of female/female pairings and male/male pairings respectively, which in at least some forms like black swans may reflect an unusual yet successful breeding strategy, as same-sex pairings may be able to protect and provide for the chicks more effectively than “straight pairings”, as for some undiscernible reason “cheating” appears to be less common. The passerines known as cocks-of-the-rocks have been reccorded to have as much as 40% of their sexual activity to be between males, while some individuals don’t even bother touching females; these are birds that have gone through the same sexual selection procedures as ungulate mammals, developing extreme sexual dimorphism to supposedly drive away members of the same sex and attract females, and yet they “delight in homosexuality”. Same with ostriches, same with birds-of-paradise, same with peafowl. Mallards, the infamous rapists of the avian world, not only have been documented treating other drakes the same way they treat hens, even down to “gang banging”, but also engaging in homosexual necrophilia; homosexual necrophilia has also been reccorded in swallows and frogmouths. And, of course, there’s the famous male/male penguin, flamingo and vulture couples in zoos all over the world.

With so many cases of homosexual behaviour among living dinosaurs, you’d think the dead ones were also this… diverse. Yet, as far as most researchers are concerned, all dead dinosaurs were “straight”: all “couples”, or even specimens found in seemingly non-agressive poses, are reffered to as heterosexual mating pairs.

The most infamous and downright ridiculous example are the two specimens of Khaan mckennai known as “Romeo and Juliet”. This fossil, two skeletons of the oviraptor species found in extreme proximity of each other, are the species’ holotype (IGM 100/1127), and not only have been interpreted as a “couple” on extremely loose grounds (they were found together and weren’t fighting; that’s the reason why they’re called “Romeo and Juliet”. I guess the Messel Pit was a massive inter-species orgy then), but are considered male and female on every looser grounds. There are literally no traits in the holotype that favour one gender over the other.

In extinct ornithodires, sex is generally determined either by extreme sexually dimorphous structures, like the crests of pterosaurs, or by two main “subtle” features: the pelvis cannal, which is supposedly wider in females, and femur medullary bone, present in females; both are features adapted for the production of eggs. We do know that the former may be of some help – Darwinopterus does have clearly female specimens, one of them preserved in the process of laying an egg, with wider pelvic cannals, while troodontids and oviraptors do show rather extreme pelvic cannal widths can may be reasonably attributed to different genders -, but it is frequently subjected to error, as the cannal’s width in consistency to the animal’s sex is hard to predict except in extreme examples; this is why Sue’s actual gender is something of a controversy, as tyrannosaur pelvis cannal widths are more difficult to accurately estimate than previously thought. Medullary bone tissue is of more help, as it is indeed only significantly observed in females during egg production. Only three major medullary bone samples have been obtained from non-avian dinosaurs, from Tyrannosaurus rex, Allosaurus fragilis and Tenontosaurus tilletti; “Romeo and Juliet” currently remain untested for medullary bone, and the pelvis bone widths have not been accurately measured either.

On other words, they truly are just two random Khaan assumed to be an heterosexual mating pairing based on close proximity.

Not only we have thus forced and arbitary gendering, we also have something of a strange agression towards non-“heteronormative” (i.e. heterosexual pairings and polygynous lekking) breeding strategies. Just witness the bile thrown at “Evolution of classical polyandry: three steps to female emancipation” (Malte Andersson, 2005), a paper that [very briefly] suggests polyandry in non-avian dinosaurs. If we are to believe some of the responses, male Triceratops forming harems and forcing intercourse on females is “normal”, while theropod females defending brooding several males brooding their cluthes like modern jaçanas is “unnatural”, “falsetious” and “unscientific”. What?

We know that in oviraptors and troodontids the males – or at least morphs with absurdly narrow pelvic cannals – were the sole incubators of the eggs, much like in modern ratites. At least a few specimens may also bear another adult as well, yet these have been dismissed as “potential heterosexual mating pairs” without further study on the animals’ pelvic width or medullary bones. From the looks of it, adult females or at least animals with wider pelvic cannals have not been reported in association with nests, which may very well mean that these specimens may be homosexual pairings. A potentially revolutionary discovery, not only casually dismissed, but outright “straight washed”.

If I can’t see it, it does not exit, henceforth it is unnatural

So, we have LGBT researchers shoved into the background and direct erasure. We have basically the worst “indirectly hostile” factors for homophobia widespread and accepted in the paleontological community. Lack of visibility is the main factor in the prevalence of homophobia, far more so than “propaganda” and violent statements, as the still immense ignorance towards animal same-sex sexual behaviour still shows. Lack of visibility also leads to the lack of ressonance, which increases the already cancerous feeling of isolation. This ignorance and these feelings led to the violent death of Baron Franz Nopcsa von Felső-Szilvás, a man who had no religious reasons for his murder-suicide, but a tragic lack of understanding that his feelings were not ill or aberrant.

The irony is all too bitter.

Mammal-Like Choristodere: Failtastic addition to the Yesterdays movement

PictureSo, basically, with Nemo Ramjet’s All Yesterdays competition, I gave my shot with my luck charms, the champsosaurs. Here is a horrendously failtastic depiction of a Champsosaurus gigas engaging in a mammal-like defense pose.

Let’s take a closer look, shall we?

Picture2

First off we have the snout. Loosely inspired by giant snalamanders and cetaceans, this is one of the few pics in existence of champsosaurs with lips (based on soft shells and other aberrant turtles). I also have it a “rhinarium”; champsosaurs, much like mammals and crocodiles, usually have fused nares. The weird things along the jaws are fleshy “whiskers”, akin to those of some salamanders.

Picture3

Here we see it with the tail raised and waving on the water, much like newts do today, only with a more mammalian angle. The feet are deliberately made rounded and simplistic because choristoderes actually had paddle-like limbs, hence something between a flipper and a land vertebrate leg.

Picture4A closer inspection at the tail. It has loose patterns, also newt inspired, and deliberately raised in a skunk style.

Picture5Another look at the flipeprs/paddle-like limbs, raising the animal erect over the sea floor, presumably in a territorial display. In the far corner there is another male; I intended it to be actually attracted to the main displaying male (not enough pics of homosexuality in choristoderes, ha!), but you can also interpret it as fleeing or something.

Picture6A final, closer look at the snout. The lips are bigger on the upper jaw, making the snout look thicker than it actually is. In the lower jaw, you can still see the teeth.

Were the first amniotes semi-aquatic?

Previously, I explored the possibility of early amniotes being semi-aquatic in my article about early aquatic mammals, and it seems this might be true after all:

Canoville, A. and M. Laurin. 2010. Evolution of humeral microanatomy and lifestyle in amniotes, and some comments on paleobiological inferences. Biological Journal of the Linnean Society 100:384–406.