dino_a_day: (Default)


My grandmother's 93rd birthday is coming up next week and I told her I would do some art as a gift. Little old ladies, my grandmother included, typically prefer extant dinosaurs to extinct ones, and she's a fan of hummingbirds, which she has lately been trying to attract to her yard. Rufous Hummingbirds (Selasphorus rufus) are a common sight here in the Pacific Northwest, and while they're drawn to a wide range of flowers, western red columbines (Aquilegia formosa) are one of their favorites.

And I think this bit of art stands as an interesting contrast to the rest of the dinosaurs, too - just look at how highly modified they've become over the last several million years! From one line of small theropods came an extremely wide diversity of modern birds with an astounding variety of shapes, sizes, and special adaptations for filling almost every niche on the planet.
dino_a_day: (Default)


Amargasaurus cazaui, from Argentina's late Jurassic period, may be familiar to some of you who played the latest generation of the Pokemon games. Amaura and Aurorus were based off of this species of sauropod, which carries twin rows of spikes down its neck. It was formerly thought that these spikes supported sails of skin, but analyses have shown that if that was the case, Amargasaurus' sails would have rendered its neck inflexible, making it unlikely. Instead, they were probably free spines, and would have served the sauropod well both for display and also for intimidation and defense. One paleontologist has even suggested that the spikes, which were probably covered in a thick sheath of keratin, could have been used as a sound display. The Amargasaurus could shake its neck and cause the spikes to rattle against each other, creating a clacking sound not unlike a very large set of bamboo chimes.
dino_a_day: (Default)


Sanjuansaurus gordilloi is a very primitive dinosaur from the late Triassic period in Argentina. During the Triassic, large agile crocodiles were the dominant terrestrial predators. Early dinosaurs, still very lizard-like with their small hands, four-toed feet, and general lack of diversification into the fantastic body shapes later eras saw, were prey more often than predators. They were small and unimpressive, and scampered about searching for insects and other small reptiles to eat.

Sanjuansaurus' habitat was, at the time, volcanically active. While much of it was covered by forests, fresh lava flows occurred regularly. Small, mobile predators like Sanjuansaurus might have been able to take advantage of these dramatically-altered ecosystems and hunt between the rocks for early colonizers such as spiders and lizards.
dino_a_day: (Default)


Yandangornis longicaudus is, as the name ("ornis") implies, a bird. We think. It's actually very hard to say. Like birds, it is fully-feathered and has a beak with no teeth. However, it also has a long bony tail, a short fourth toe, and other skeletal features that make it more similar to dinosaurs. Since birds are dinosaurs, the distinction is purely one of interest to taxonomists, who work to figure out which species are more closely related to which other species. From a taxonomic perspective, Yandangornis is a dinosaur, as are all birds - but whether or not it can be called a bird for sure is still up for debate. Discovered in Zhejiang Province, China in 1999 from a largely intact skeleton, we do know that it was more adapted for ground-dwelling than aerial or arboreal life, and was similar in size and habit to today's roadrunners, likely chasing down insects, small reptiles, and primitive mammals on foot.

As a heads up, updates will be spotty over the next couple weeks as I finish my thesis and prepare my defense. I'll try not to go full hiatus on you guys!
dino_a_day: (Default)


Sinornithomimus dongi was found in the highlands of Mongolia in 2003. Late Cretaceous Mongolia wasn't all that unlike the Mongolia of today, and these ostrich-like theropods, which lived in small herds of similarly-aged individuals, would have had to pass through expansive desert areas to reach pockets of water once snowmelt became scarce in the summer. Many of the individuals we have fossils of include some of the most complete dinosaur skeletons, found having evidently been trapped in the mud at a water hole.
dino_a_day: (Default)


Pachycephalosaurus wyomingensis ought to be a familiar name to most of you. Discovered in Wyoming in 1931, it has long been famous as the dinosaur with the domed bony head, supposedly used by males in territorial and breeding disputes much like bighorn sheep today, by charging and then headbutting each other in a test of endurance and strength. Recently that thought has been disputed, as the skull likely could not have sustained such blows, nor could the neck, and no evidence of scarring or other damage on the heads of pachycephalosaurs that would result from this kind of combat has been found. They may instead have headbutted the side or flank of competing males, or of potential predators in self-defense.

Juveniles had far more extensive head spines than did adults, which initially caused paleontologists to think they were different species - Stygimoloch spinifer and Dracorex hogwartsia (what a name!). It now seems that the horns on young Pachycephalosaurus were absorbed into the heavy head dome as bone grew around them during the aging process.

Pachycephalosaurus were beaked but had small leaf-shaped teeth - unlike their relatives the ceratopsians, they must have eaten leaves, nuts, soft fruits, and/or insects, rather than tough cycads and grasses. The end of the Cretaceous had plenty of soft leafy plants and flowers for them to eat, making them less similar to cows and more like today's deer in terms of diet.
dino_a_day: (Default)


Ceratosaurus nasicornis is a late Cretaceous theropod from western North America. Discovered in 1884, its original describer felt that the unusually large (for a theropod, anyway) horns on its face were deadly weapons, in line with the general sentiment at the time that dinosaurs were absurdly brutish and violent compared to modern animals. Today, paleontologists feel that the horns might have been used in male-male combat over territory or females, or that possibly the horns were purely for display purposes. Males and females may have had differently-colored or differently-sized horns, or they may have been useful in species recognition, as Ceratosaurus was not the only large theropod in its habitat.
dino_a_day: (Default)


Balaur bondoc was an apex predator on Hateg Island, the late Cretaceous portion of Romania from which we know so much about the effects of island life on dinosaur evolution. Balaur was roughly the size of a turkey, with unusual proportions for a dromaeosaur - short, robust arms and legs, only two fingers on its hand, and with not just one but two sickle claws on each foot due to a highly modified inner toe. It wasn't a graceful sprinter like its relatives, but it was powerful and likely capable of taking down prey larger than itself. This one has caught a juvenile Zalmoxes robustus, an iguanodontid, still young enough to have a coat of down. Like Magyarosaurus and other Hateg dinosaurs, Zalmoxes grew much smaller than its relatives, an example of island dwarfism. As an adult, it would not have exceeded 7-10 feet in length, considerably smaller than the nearby Iguanodon species of continental Europe which reached 30-40 feet long as adults.

And with this I am officially back from my hiatus! It was longer than I'd anticipated it being, but that's thesis work for you sometimes.
dino_a_day: (Default)


Buitreraptor gonzalezorum is a unenlagiine dromaeosaur from Cretaceous Argentina. Unlike more typical dromaeosaurs, it had very long, thin legs, as well as a long slender snout filled with small, strongly recurved and grooved teeth. Rather than hunting larger animals or living in packs, it appears likely that Buitreraptor captured smaller animals - mammals, lizards, and amphibians, for example. Others, however, including Scott Hartman, a well-known skeletal restoration artist, have speculated that Buitreraptor's proportions and tooth shape suggest it may primarily have been piscivorous, making it the prehistoric equivalent of a heron or egret.
dino_a_day: (Default)


Ouranosaurus nigeriensis is a basal hadrosaur from, as the name implies, what is today Nigeria. While I've given it a sail for display (and possibly thermoregulation as well) here, the odd shape of the vertebrae, with them becoming wider and flatter toward the tips, suggest a large fat-storing hump might also have been possible. As a hadrosaur, it was herbivorous, and like some other hadrosaurs, the first two toes on the front feet were flattened and thick at the ends, forming a hoof. Unlike Edmontosaurus, which I drew previously, Ouranosaurus retained its fourth and fifth fingers separate from the hoof, and the fifth finger especially seemed to remain flexible, possibly enabling the animal to grab onto hard-to-reach plants while shifting to a temporary bipedal stance. Like other hadrosaurs, such as Iguanodon, the thumb was modified into a spike, possibly for defense against predators and/or combat with other Ouranosaurs during territorial or breeding disputes.
dino_a_day: (Default)


Concavenator corcovatus is a carcharodontosaur, one of several medium-to-large carnivores from Cretaceous Southern Europe. Discovered in Spain in 2010, it is the only known carnosaur with a sail on its back. This sail is unlike those of the early synapsid Dimetrodon, or the spinosaurs, in that rather than being tall and thin, it was low and likely wide at the base - possibly for display, possibly for fat storage such as in today's camels, or potentially for both purposes.

Concavenator also has large bumps on its forearm bones that appear to be quill knobs, and skin impressions show that its body was covered in large alligator-like scales.
dino_a_day: (Default)


Archaeopteryx lithographica has, until recently, enjoyed its place in the spotlight as the link between dinosaurs and birds. When it was discovered in 1861, it was regarded as a bird, but one with unusually dinosaur-like characteristics, including a long bony tail, clawed hands on the wings, and a toothed snout. As more specimens have been recovered, however, and with more and more feathered theropods being found every year, it has become evident that Archaeopteryx may not be the all-important transitional stage we once thought it to be. While some paleontologists maintain that it belongs in Avialae, others have suggested it may in fact be a troodontid or other maniraptoran, and therefore still a close relative of birds, but no more so than a species like Velociraptor, rather than a likely ancestor of modern birds. Whatever the case may be, it was certainly an important discovery in its time, and remains a well-known public ambassador for the evolutionary history of birds.
dino_a_day: (Default)


As anyone following this blog is well aware, dinosaurs did not go completely extinct 65 million years ago. A few small genera were able to survive the mass extinction, and one branch in particular became the Avialae, which we know today as birds. They diversified, colonizing habitats their ancestors had once ruled, but now having to compete with mammals as well, which previously had been primarily underground and nocturnal but now found themselves with a variety of niches to exploit.

While many birds were lightweight and airborne, a few different lineages returned to a shape similar to that of their ancestors - the ratites (ostrich, emu, and their relatives), the Gastornithiformes (large predatory ground-dwelling relatives of ducks), the Secretary Bird, and the seriemas, to name a few. But the most striking in terms of convergent evolution with ancestral dinosaurs were the now-extinct Phorusracidae - massive T-rex-like falcons, including the species pictured above, Titanis walleri. It was an estimated 8 feet tall and 330 lbs, and during the last ice age, it ruled the plains of southern North America, once again forcing the smaller mammals to hide or risk being eaten in one great gulp.
dino_a_day: (Default)


Einiosaurus procurvicornis is a Cretaceous ceratopsian from Northwestern Montana. What is today plains, forests, and high mountains was then something remarkably similar, though lower in altitude - while so many dinosaurs we've found are from warm, wet places, Einiosaurus lived in a semi-arid temperate zone. We have fossils of juveniles and adults which give researchers a good idea of how the frill and horn developed over the course of the animal's life.
dino_a_day: (Default)


Epidexipteryx hui, another of the small feathered Chinese dinosaurs, is a bit like Scansoriopteryx from a previous entry, with one major exception - it had only simple feathers, with no flight feathers whatsoever, except for four very long ribbon-like tail feathers. They were likely boldly patterned and used for display purposes, though given that we only have one fossil of this species, it's hard to say definitively. They, like Scansoriopteryx, had an elongated third finger, possibly for use in climbing or for reaching insects in small gaps and crevices in tree bark or rotting wood. The lack of flight feathers on the arms, however, suggests that this dinosaur wouldn't have been able to glide if it did climb up into the trees, while its relative may have done so. Instead, this animal may primarily have been a ground-dwelling species.
dino_a_day: (Default)


Didn't quite have time to finish last night, so here it is this morning. This is Edmontosaurus annectens, one of the best-known dinosaurs in existence. On top of having found hundreds of very complete skeletons of adults and juveniles, we have a few very complete mummies as well, which have allowed us to know the skin texture (loose and scaly, with round tuberculous scales more like a gila monster than a snake), and diet (lots of seeds, conifers and gymnosperms, based on gut contents and isotope ratios in the teeth). We have skeletons that show signs of scar tissue, damaged vertebrae and hips, and tooth marks, showing that they were preyed upon by large tyrranosaurs, as well as skeletons that show bone damage from other ailments such as cancer. Skeletons have been found from Alaska to Colorado, a huge range for any dinosaur, and some have suggested they may have been migratory like today's caribou, heading south to avoid the arctic winters. Their front toes were even developed into hoof-like structures, with the hard-scaled skin fully enclosing flattened toe bones. And they definitely lived in herds, some of which may have numbered thousands of Edmontosaurs.

Despite everything we do know, we're still finding out new information about this and other Edmotosaurus species. At the end of 2013, one specimen was discovered that preserved impressions of soft tissue around the head, which revealed for the first time that Edmontosaurus had a fleshy rooster-like comb on top of its head - something we never could have seen from skeletons alone. Just one more reminder of how little we know, even when it comes to a species we think we know so much about.
dino_a_day: (Default)


Guanlong wucaii, like many of the Chinese dinosaurs, has a very poetic name - "crowned dragon of five colors" - the five colors being the banded sandstone of Wucaiwan, similar to the four corners region of the US' Great Basin desert. Guanlong is a primitive tyrannosaurid from the late Jurassic, and unlike later tyrannosaurs, it has long, robust arms and hands and a tall crest over the top of its relatively slim head. Only two skeletons have been found, but one was a juvenile, with a much shorter crest over the nose, indicating that as individuals of this species matured, the crest grew taller as well as back toward the eyes. While neither skeleton preserved feathers, it is likely that like other known primitive tyrannosauroid dinosaurs, Guanlong would have had a coat of simple hairlike feathers.

I know, I know, I missed yesterday. Somehow on my travels I obtained a strain of Norovirus, or something similar. I'm feeling more functional today, thankfully.
dino_a_day: (Default)


No fancy title or background on this one today, I'm afraid - I'd like to do more with these guys at some point, though, because what an unusual dinosaur. This is Caudipteryx zhoui, an early Cretaceous oviraptorid. The outward similarity these dinosaurs shared with later chickens and pheasants is a little bit baffling. They had a very chicken-like body shape, with a birdlike short fanned tail. Strangely, no fossils found so far preserve any secondary feathers (the long feathers attached to the arm, as opposed to the hand feathers, which are the primaries) - either they didn't have them, or somehow they simply weren't fossilized, it's difficult to say. They did have teeth inside that beaked mouth, but they may have been vestigial, for as herbivores, they really only needed that beak and the stones they swallowed into their crop to tear up and break down plant matter. Despite this dinosaur looking an awful lot like a bird, they weren't as closely related to them as some of the other small theropods, like the dromaeosaurs - but maybe that doesn't matter so much, given how blurry that dinosaur-bird line is, already.
dino_a_day: (Default)


Magyarosaurus dacus is a sauropod from a heavily-forested island that is now part of modern-day Romania. As we see today in many island animals, the restricted size of the terrain led to a reduced size in its inhabitants, including these pygmy sauropods, no taller than today's horses and weighing a mere one ton. Magyarosaurus, like its close relatives around the world at the time, had an armor-plated back. Underneath its skin were osteoderms - large bony scutes that formed in rows. In addition to being armor, these osteoderms could be dissolved from the inside and made hollow, the calcium forming them recycled to become eggshells during the breeding season.
dino_a_day: (Default)


Discovered in 2008 along the shores of the inland sea that once filled most of Utah, Talos sampsoni is an important troodontid dinosaur for paleontologists and paleoartists in that it confirmed what was speculated about in the 1960s with regard to limb morphology in these dinosaurs. Unlike the heavier-built dromaeosaurs, troodontids, and Talos in particular, had very long, thin legs, indicating it was a very quick runner, and also relatively short arms - these were definitely not gliders or climbers, but fast, active ground-dwelling hunters. Only one Talos specimen has been found, and it has a cracked, damaged sickle claw on its left foot, suggesting that just like in the dromaeosaurs, and unlike some of their smaller arboreal relatives, troodontids used that claw for combat.
Page generated Oct. 22nd, 2017 11:59 am
Powered by Dreamwidth Studios