Mystipterus: Beast of the Week

This week we'll be checking out a newly described prehistoric mammal that I was privileged enough to help introduced to the world.  Let's look at Mystipterus austinae!

Watercolor reconstruction of Mystipterus living in what is now north Dakota, 32 million years ago.  It would have shared its home with land snails, a legless burrowing lizard, and the early canid, Hesperocyon.

Mystipterus was a prehistoric mole that lived in what is now North Dakota during the middle Oligocene period, about 32 million years ago.  Known from mostly just a lower jaw, its body length is estimated at only a few inches long (about 7 centimeters) from nose to tail.  Like its living relatives, it was likely a meat-eater, sniffing out and devouring most invertebrates and possibly other kinds of smaller animals it came across.  The genus name translates to "Impossible to Identify" because of its dubious identity after it was first discovered. It was initially interpreted as a bat, but has since been more accurately identified as a mole.

Mystipterus one of the earliest known moles.  By comparing the fossils that have been found to those of modern kinds of moles, paleontologists have predicted that Mystipterus would not have resembled the more specialized moles, with their enlarged front limbs for digging.  Rather it was most similar to moles in the genus Uropsilus, which are more generalized.  The common name for this group is the shrew-moles, since they in many ways resemble shrews.  It may have even had a long, trunk-like nose, like some shrews have.  

Jaw and teeth from Mystipterus featured in the 2023 paper, by Korth Et al. referenced below.

Like its modern relatives, Mystipterus likely spent most of its time underground, possibly coming out at night to hunt. It may also have been a strong swimmer in life, like many modern moles and shrews are, especially since the rocks its bones were found in indicate it would have inhabited a wet environment with lots of slow-moving rivers and streams.  Since it was so small, it would have needed to avoid predators, especially while above ground, like the early canid, Hesperocyon, whos bones were found in the same area as Mystipterus'.

References

Korth, W. W.; Boyd, C. A.; Emry, R. J. (2023). "Additional small mammals from the Oligocene Brule Formation (Whitneyan) of southwestern North Dakota". Paludicola. 14 (2): 57–74.

Maryland Dinosaurs: Major Discovery!

 As you probably know, if you have been reading this blog for a while or follow me on any social media, I was born in and spent the majority of my life in New Jersey. What you may not know, however, is that I moved down to Maryland several years ago.  It was pretty sad because that means I'd be farther away from some of my favorite things, like the American Museum of Natural History, Hadrosaurus, Dryptosaurus, and good pizza.  One positive thing of the move, however, is it means I'm now living extremely close to a unique dinosaur fossil site, called the Arundel Formation, where some amazing dinosaur bones have been unearthed.

Photo of the Arundel formation I took while at the press release.  Just out of frame in both directions there are parking lots and warehouses.

The Arundel Formation used to be a mining area during the late 1800s, but now is surrounded by warehouses and office buildings.  Fossils have been discovered there for decades, including many tree and other plant fossils, like pinecones and even pollen, as well as bones from several kinds of dinosaurs, like Maryland's official state dinosaur, Astrodon.  All the fossils here are from the early Cretaceous period, about 115 million years ago, in what was a slow-moving river with surrounding swamps at the time.

Dr. Thomas Holtz speaking at the press conference about the kinds of dinosaurs that have been found at the Arundel formation.

Earlier this week a press conference was held at this site with exciting news.  Teams of paleontologists and volunteers, led by John-Paul Hodnett, just this year started uncovering many bones from not one, but several different species of dinosaurs, some of which are previously only known from teeth and other very tiny fragments, as well as at least one completely new taxa!  As stated, this site has been yielding fossils for many decades, but this many bones from this many different species at once is a first.

Below is a breakdown of the newest dinosaur discoveries shared from this press release.

Leg bone from a very large theropod

Watercolor reconstruction of Acrocanthosaurus, which may have lived in what is now Maryland.

The largest theropod bone on the eastern side of the country was discovered at the Arundel Formation just this year.  Based on the size of the tibia, the whole dinosaur is estimated to have been roughly thirty eight feet long from snout to tail.  

John-Paul Hodnett speaking about how the fossils formed at the press release from within the Arundel formation.  The big bone still in the ground at his feet is a tibia from a very large theropod.

Based on fragmentary material found at this sight in the past, as well as the time period the formation is from, this leg could belong to Acrocanthosaurus, but it could also be something entirely new depending on what further examination shows.  

Astrodon bones and a claw.  

Watercolor life reconstruction of Astrodon, Marylands state dinosaur.

Astrodon is Maryland's official state dinosaur.  It was a sauropod, related to Brachiosaurus and Camarasaurus, and was likely the largest animal in its community when it was alive.  This past year more bones from Astrodon, including a foot claw, have been discovered, giving us a more complete picture of this dinosaur's skeleton.  

Recently unearthed Astrodon fossils from the Arundel site.

It is possible these bones are from the same individual, which was a subadult when it died, that we already have an incomplete skeleton of on the fossil record, based on the size and location in the site they were found.

Priconodon bones.  

Very rough sketch of what Priconodon may have looked like.

Priconodon was a plant-eating armored dinosaur, from the nodosaur group of ankylosaurs, characterized by usually sporting long, thorny spikes running down their flanks.  For years, Priconodon was only known from teeth and very small bone fragments.  

Gigantic Prictonodon tail vertebra unearthed recently at the Arundel site.  My hand for scale.

Just this year, however, whole bones, including some truly massive vertebra, have been discovered.  Based on the size of these vertebra, Priconodon could very well have been one of the largest, if not THE largest armored dinosaur ever found!

New species of tyrannosauroid teeth

Watercolor reconstruction of a generic early Cretaceous tyrannosauroid, with three fingers on each hand, long legs, and feathers.

Teeth from what appear to be a tyrannosauroid have been discovered this year at the site for the first time at this location.  

Tyrannosauroid tooth recently unearthed from the Arundel formation.

Unlike giants like Tyrannosaurus rex, which lived at the very end of the Cretaceous, tyrannosauroids during the early cretaceous were usually relatively small, but likely fast-moving and covered in feathers.

Dromaeosaur teeth

Deinonychus, which may have lived in what is now Maryland.

Dromaeosaur fossils have been unearthed at this site, possibly belonging the famous, Deinonychus, based on size and time period.  This year more teeth that match this dinosaur were unearthed.

Ornithomimosaur bones and claw

Bones from an ornithomimosaur, group of dinosaurs that connvergently resembled ostriches, have been found at this site, including a bone unearthed just this year.  

watercolor reconstruction of a generic early cretaceous ornithomimid.  They tend to have proportionally larger heads and small teeth, compared to their toothless later relatives.

Like the dromaeosaur bones, ornithomimosaur bones have been uncovered at this site before, but having new material will add to how much we can actually learn about them and hopefully help us create a more accurate picture of them in this part of the world. 

Ornithomimid fossils recently unearthed from the Arundel formation.

Small coelurosaur theropod

A few very small bones and teeth from some kind of small bird-like theropod have been found at the Arundel site.  Unfortunately they aren't diagnostic enough to narrow it down any more than being from a coelurosaur, the broad group of theropods that includes tyrannosaurs, dromaeosaurs, and birds.  The teeth appear to be straight and pointed, however, which is unusual.  (I wonder if it was a kind of unenlagiine) Hopefully we'll learn more soon.

In addition to all these dinosaurs, the fossils of several other animals, including crocodiles, turtles, stingrays, and mussels were unearthed this year.  Furthermore, fossils from other dinosaurs and other animals have been found here in the past and may come up again as digging continues, including mammals and a small early ceratopsian, similar to the western US contemporary, Aquilops.

Watercolor reconstruction of Aquilops, which lived at the same time as the dinosaurs unearthed at the Arundel formation.

The news of so many bones being pulled out of this sight is extremely exciting.  Not only because they will vastly increase our understanding of previously very mysterious dinosaurs, but also because we have at least one totally new species. Even more exciting perhaps, is the fact that its all taking place on the east coast, an area not normally associated with major dinosaur fossil sites.  I can't wait to see what else is uncovered in the coming days!