Platypterygius: Beast of the Week

This week we will be looking at a successful ichthyosaur.  Enter Platypterygius!

Platypterygius was a relatively large ichthyosaur, group of marine reptiles that converged with fish in their body shape, that could grow to be about twenty three feet long from snout to tail.  The genus encompasses several species that have been found around the world, including Australia, United States, Russia, Colombia, and Argentina.  That, alone, makes this creature a success story in the grand scheme of things.  However, it is when Platypterygius lived that makes it truly impressive.  Most ichthyosaurs lived during the Triassic and Jurassic.  It is thought by most that by the time the Cretaceous came around, the poor ichthyosaurs were outcompeted by newer forms of large marine reptiles like pliosaurs and mosasaurs.  But not Platypterygius!  This gritty reptile persisted all the way through to the late Cretaceous, 131 to 91 million years ago!

Platypterygius sp. native to what was once Texas, USA, life reconstruction by Christopher DiPiazza.  This genus is known to have eaten turtles in life.

Like its closest relatives, Platypterygius had the telltale ichthyosaur profile, which superficially resembles a combination of a tuna and a swordfish at first glance.  It had a long pointed snout, lined with sharp teeth.  It had four flippers that evolved from walking limbs millions of years prior.  The back flippers were proportionally much smaller than the front ones.  It likely had a tail fluke of some kind and dorsal fluke, as well.  It's eye sockets were relatively large so they were likely comfortable hunting in deep water where there was less light and/or during the night.  Platypterygius is defined by having more finger bones than what is typical of ichthyosaurs in its front limbs.  These bones are especially flat and widened to form the broad paddle appendage it used for swimming in life.  It is because of this specific morphology it earned its genus name, which translates to "flat wing".

Platypteregius americanus skeleton at the Royal Tyrrell Museum in Canada.  Photo by By Roland Tanglao

The earlier forms of Platypterygius that lived during the early Cretaceous were specialist hunters as far as we can tell, preferring to hunt fish and cephalopods. (like squid and ammonites)  These species, like Platypterygius hauthali, from South America (lived between roughly 131 and 125 million years ago), had relatively streamlined bodies and longer pectoral (front) flippers.  These are adaptations for fast swimming so they could pursue their quick-moving prey.  Millions of years later, however, we see a shift in strategy.  Species of Platypterygius that lived towards the end of the Cretaceous, like P. americanus (time range of 112 to 91 million years ago), were bulkier, with proportionally shorter flippers. Their teeth were also slightly larger and more robust.  In addition to differences in morphology, the later forms of this genus show evidence of hunting differently, too. Paleontologists have discovered remains of different kinds of prey in their stomach cavities, including bones from birds, and even sea turtles.  This paints a picture of an ichthyosaur that was less picky about what it considered prey, and was able to afford pursuing this wider menu with a little extra muscle at the price of speed.  Platypterygius managed to carve out a more generalist niche when its relatives were going extinct in reaction to increasing competition from other kinds of marine reptiles that were appearing during the Cretaceous, like pliosaurs and mosasaurs.

Platypteregius sp. tooth.  Photo by Nathan Van Vranken.

That is all for this week!  Special thanks to paleontologist, Nathan Van Vranken, who is currently finishing a new scientific publication on ichthyosaurs, including Platypterygius, for lending his brain to this post.  As always leave a comment below or on our facebook page!

References

Arkhangel’sky, M. S., Averianov, A. O., Pervushov, E. M., Ratnikov, V. Yu, and Zozyrev, N. Yu., 2008, On ichthyosaur remains from the Cretaceous of the Voronezh region: Paleontological Journal, v. 42, n. 3, p. 287-291.

Van Vranken, Nathan, 2017, Texas Cretaceous Ichthyosaurs: A Glimpse of Their Last Days in the Early Late Cretaceous.

Bulbasaurus: Beast of the Week

This week we will be looking at a newly described reptilian relative of mammals.  Check out Bulbasaurus!  Bulbasaurus was a dicynodont, a wildly successful group of plant-eating reptiles that shared characteristics with mammals.  It lived during the late Permian, between 260 and 252 million years ago, in what is now South Africa.  From beak to tail it would have roughly measured two feet long...maybe a bit less.  (Only the skull has been found, which was about six inches long.)  The genus name, "Bulbasaurus", tranlsates to "bulbous reptile" in reference to the bony mass above its nose.  The species name, "phyloxyron", translates to "leaf razor", in reference to how it may have cut leaves to eat with its beak. 

Life reconstruction of Bulbasaurus, by Christopher DiPiazza.

Bulbasaurus, as stated above, was a dicynodont.  Dicynodonts were interesting reptiles that looked like a combination of a few different animals alive today.  I have heard many compare them to pigs...but I never really saw that.  They had proportionally large heads, and broad beaks.  Many kinds had two tusks protruding downwards from their top jaw.  They would have walked in a squat, semi-sprawling posture on four, stout legs.  So if I were to describe a dicynodond in terms of modern animals...I'd say just imagine a French Bulldog...with beak...yeah...yeah, that's perfect. 

Bulbasaurus was an important find because it was a member of the family within dicynodonts, called geikiidae.  Until its discovery, geikiids were only known from significantly later times in the Permian and Triassic.  Bulbasaurus sets the first geikiids back millions of years than what was previously thought, however.  Geiikid dicynodonts typically had particularly large, robust heads, curved beaks, and longer tusks, which Bulbasaurus had when compared to its contemporary family members. 
 

Bulbasaurus skull from the paper recently published by Christian Kammerer and Roger M. H. Smith.

SO WHAT ABOUT THAT NAME?!  Was Bulbasaurus named after the pokemon, Bulbasaur? It certainly looks similar.  In fact, Bulbasaur, the pokemon's design was almost certainly based off dicynodonts, as I explained in a post last year.  According to interviews with Dr. Christian Kammerer, one of the paleontologists who worked with, and lead author of the paper that describes Bulbasaurus, it's insisted the name is a coincidence, and it really is just in reference to it's nose...and the species name...."leaf razor" in reference to it's beak, despite the fact that any pokemon fan can tell you one of Bulbasaur's signature attacks is called razor leaf.  I guess we will just have to believe them just like you should just believe my illustration of Bulbasaurus in no way is in reference to Bulbasaur, the pokemon's, color scheme, nor is the pose and setting inspired by the artwork on Bulbasaur's first pokemon card...

Stop looking for things that aren't there!  Definitely no connection here.  Total coincidence.

References

Kammerer, C.F.; Smith, R.M.H. (2017). "An early geikiid dicynodont from the Tropidostoma Assemblage Zone (late Permian) of South Africa". PeerJ. 5. doi:10.7717/peerj.2913. ISSN 2167-8359.

Kammerer, C.F.; Angielczyk, K.D.; Frobisch, J. (2011). "A Comprehensive Taxonomic Revision of Dicynodon (Therapsida, Anomodontia) and Its Implications for Dicynodont Phylogeny, Biogeography, and Biostratigraphy". Journal of Vertebrate Paleontology. 31 (sp1): 1–158.

Plateosaurus: Beast of the Week

This week we will be going over a well-known and popular dinosaur, Plateosaurus!

Plateosaurus was a plant-eating dinosaur that lived in what is now Germany, Switzerland, Greenland, and France, during the late Triassic Period, between about 214 and 210 million years ago.  As an adult it would have averaged about twenty feet long from snout to tail, although certain specimens suggest it was capable of growing even larger than that in some instances.  The name, "Plateosaurus" translates to "Broad-Build Lizard" most likely in reference to the dinosaur's robust bones.

Two rival Plateosaurus engelhardti duel for mating rights by Christopher DiPiazza.  The behavior was inspired by the intraspecies combat of many lizards and is purely speculation.

Plateosaurus is classified as a basal sauropodomorph, or "prosauropod".  These plant-eating dinosaurs were related to the much larger, and more iconic sauropods, like Brontosaurus and Apatosaurus, but tended to live in the late Triassic and early Jurassic periods.  In fact, a branch of basal sauropodomorphs actually gave rise to the first true sauropods.  Unlike sauropods, prosauropods typically walked on their hind legs.  Many of them, including Plateosaurus, were obligatory bipeds, meaning they could only walk on their hind legs, like modern birds, and other theropods.  HOWEVER...That being said...Plateosaurus was likely able to walk on all fours when it was a baby, based on what we know about a close relative, Massospondylus, which we know were quadrupedal as babies, thanks to skeletons, then became obligatory bipeds as they grew up.

Plateosaurus had a relatively long neck, which it would have used to help it feed on vegetation above and below it without without having to move its body much.  It had a long, almost rectangular skull, with the tip of its snout sloping slightly downwards.  Within the mouth it possessed many small, leaf-shaped teeth with serrations, which would have been ideal for eating plants, like horsetails, which lived at the same time as it.   The back of Plateosaurus' jaws also sloped downwards, implying there was more muscle there for biting through tough vegetation.

Plateosaurus mounted skeleton on display at the American Museum of Natural History in New York City.  The dinosaur would have likely walked with its tail above the ground in life, as this was mounted before that idea.

Plateosaurus also had robust, powerful arms, each tipped with five fingers.  The first three fingers possessed curved claws, the first digit's being the largest.  These claws may have helped to manipulate branches while feeding, defend against predators, or fight rivals of the same species. (or all three.)  The hind legs were also powerful, each foot ending in four long, broad claws.  The long, muscular tail would have helped Plateosaurus keep its balance as it walked around on its hind legs.

Left hand of Plateosaurus.  Note the large claw on digit 1.

Fortunately, Plateosaurus is known from many individual specimens, so scientists have been able to learn a lot about this dinosaur.  By looking at certain bones closely, it can be determined how an individual dinosaur was growing.  Plateosaurus, it turns out, went through a period of rapid growth when it was young, then slowing down when it reached a certain age or size.  However, the sizes of different individual Plateosaurus seemed to vary at the same age. For instance a sixteen-foot long Plateosaurus could have been the same age as an almost thirty foot Plateosaurus.  We see this today in modern reptiles and it depends on how many resources are available to animals as they are growing.  The more food an animal has, the larger and more rapidly it will grow.

Plateosaurus mounts on display at the University of Tübingen, in Germany.

Looking at the mobility of the ribs of Plateosaurus, and how they could change positions depending on if the dinosaur was inhaling or exhaling, it could also be hypothesized that this dinosaur was endothermic, like birds, and would have had the same kind of one-way breathing system that they do.  This form of respiratory system, only currently known today in birds and a few reptiles, makes it so that the animal is constantly taking in fresh oxygen with every inhale and exhale.  If humans could breathe like that track events would be a lot more intense!

That is all for this week!  Special thanks to Dr. Heinrich Mallison, who lent his expertise on Plateosaurus for the making of this post.

References

Creisler, Ben. "Plateosaurus: The Etymology and Meaning of a Name." Plateosaurus: The Etymology and Meaning of a Name. Dinosaur Mailing List, n.d. Web. 

Huene, F. von (1926). "Vollständige Osteologie eines Plateosauriden aus dem schwäbischen Keuper" [Complete osteology of a plateosaurid from the Swabian Keuper]. Geologische und Paläontologische Abhandlungen, Neue Folge (in German). 15 (2): 139–179.

Jaekel, O. (1911). Die Wirbeltiere. Eine Übersicht über die fossilen und lebenden Formen [The Vertebrates. An overview of the fossil and extant forms] (in German). Berlin: Borntraeger.

Mallison, H. (2010). "The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount". Acta Palaeontologica Polonica. 55 (3): 433–458. 

Sander, M.; Klein, N. (2005). "Developmental plasticity in the life history of a prosauropod dinosaur". Science. 310 (5755): 1800–1802. Bibcode:2005Sci...310.1800S.