Nasutuceratops titusi, a new ceratopsian from Utah

The Kaiparowits Formation of Late Cretaceous Campanian age, in the Grand Staircase-Escalante National Monument, Southern Utah, has in recent years released a number of spectacular finds, including the ceratopsians Utahceratops and Kosmoceratops and the tyrannosaurid Teratophoneus.

This year sensation from Utah might well be another ceratopsian, Nasutuceratops titusi, known from an almost complete skull and an associated left forelimb, as well as skull fragments from two other individuals. Some skin impressions were also found with the forelimb. Nasutuceratops is still a nomen nudum (“naked name”), meaning it has not been officially and formally described in a published scientific journal yet. It has been named by Eric Karl Lund (advisor: Scott Sampson) in his Master of Science Geology thesis submitted to the faculty of the University of Utah in 2010. In a comprehensive phylogenetical analysis, this short snouted long horned centrosaurine ceratopsian was found to be closely related to the contemporary Avaceratops lammersi from Montana.

To my knowledge, the talented paleoartist Andrey Atuchin is the first one to have made a reconstruction of this intriguing animal. Mine is far from being as good as his but here it is nevertheless.

Update: it has been officially described in 2013 as Nasutoceratops titusi by Sampson et al (with an "o" instead of a "u").

Ref: Sampson, S. D., Lund, E. K., Loewen, M. A., Farke, A. A, Clayton, K. E. 2013. A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia. Proceedings of the Royal Society B: Biological Sciences 280 (1766) 20131186.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Latoplatecarpus willistoni, a new Mosasaur from the Western Interior Seaway

Fig 1.- Latoplatecarpus willistoni had a streamline body.

Mosasaurs are a group of highly successful marine lizards from the Late Cretaceous period that are related to the modern day land-living Komodo dragons and varans. Their diversity ranges from the small 3 meters long mollusk eating Carinodens to the giant 18 meters long predator Tylosaurus. To date, around 30 genera with a total of some 40 species have been described. Their geographical distribution is worldwide but fossils are particularly abundant in the ancient Western Interior seaway that used to divide the continent of North America during the Late Cretaceous period. The number of specimens found there is amounting to more than 3000.

The Plioplatecarpines form a particular group of mosasaurs consisting of shorted headed and long bodied critters, known from some 500 specimens from North America. In a general revision of the Plioplatecarpines published in the Journal of Vertebrate Paleontology in 2011, Takuya Konishi and Michael W. Caldwell name two new genera, Latoplatecarpus and Plesioplatecarpus and one new species, Latoplatecarpus willistoni, while two other taxa were referred to the above mentioned genera, Latoplatecarpus nichollsae (formerly Plioplatecarpus nichollsae) and Plesioplatecarpus planifrons (formerly Clidastes planifrons and then Platecarpus planifrons). In total, Konishi and Caldwell recognize 7 genera and 11 species to the Plioplatecarpines.

L. willistoni is known from 4 partial skeletons from the lowermost middle Campanian period of the Late Cretaceous, one (the holotype), from the Lower Pierre Shale Formation of Southern Manitoba, Canada, two from the Pierre Shale Formation of Wyoming and one from the Ozan Formation of Texas. The contemporary L. nichollsae is known from remains from Manitoba, Wyoming, South Dakota and Alabama, while P. planifrons, dating from the more ancient Upper Middle Coniacian-Middle Santonian period of the Late cretaceous, is known from Kansas and Alabama. 

Fig 2.- Old representation of Platecarpus with an eel like body.

The fish eating plioplatecarpines, like the other mosasaurs, were traditionally depicted as eel-like creature that propelled by lateral motion of the body. But the description of an exceptionally preserved complete specimen of Platecarpus in 2010 indicates that the general body plan of the most derived mosasaur Plotosaurus was also present in plioplatecarpines. The specimen is complete with skin impressions and possible internal organ impressions, and shows a sharp downward turn of the tail indicating the presence of a tail fluke. By an effect of convergent evolution, mosasaurs, it turned out, had a streamlined body shape similar to other marine creatures such as ichthyosaurs, metriorhynchids and sharks.

References:

Lindgren J, Caldwell MW, Konishi T, Chiappe LM. 2010. Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur. PLoS ONE 5(8): e11998.

Konishi, T. and Caldwell, M.W. 2011. Two new plioplatecarpine (Squamata, Mosasauridae) genera from the Upper Cretaceous of North America, and a global phylogenetic analysis of plioplatecarpines. Journal of Vertebrate Paleontology 31 (4): 754-783.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Diodorus scytobrachion, a new silesaurid from the Late Triassic of Morocco

 Fig 1.- Asilisaurus kongwe, from Tanzania.

The Silesaurids form a family of archosaurs closely related to the dinosaurs. They appeared in the fossil record during the Middle Triassic period and thrived alongside the early representatives of the dinosaurian clade during the Late Triassic period. These long-necked lightly-built quadrupedal critters possessed a dentary beak and leaf-shaped teeth, indicative of either an herbivorous or omnivorous diet.

Fig 2.- Silesaurus opolensis, from Poland.

Long known from just a few fragmentary remains from Argentina, their richness has only been recognized quite recently with the description of several well preserved taxa from Poland (Silesaurus opolensis, described in 2003), Brazil (Sacisaurus agudoensis, described in 2006) and Tanzania (Asilisaurus kongwe, described in 2010).

Yet another taxon, Diodorus scytobrachion, has just been described by Christian Kammerer, Sterling Nesbitt and Neil Shubin, from the Late Triassic (?Carnian-Norian) Timezgadiouine Formation of the Argana Basin of Morocco. The remains consist of a partial right dentary, isolated teeth, two humeri, a metatarsal and femur coming from different individuals. Phylogenetical analysis shows it was most closely related to the Brazilian Sacisaurus. Diodorus confirms the widespread distribution of the Silesaurids.

References:
Christian F. Kammerer, Sterling J. Nesbitt, and Neil H. Shubin. 2011. The first basal dinosauriform (Silesauridae) from the Late Triassic of Morocco. Acta Palaeontologica Polonica, in press.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Hyracotherium & Mesohippus

Starting a series of illustrations on the Early horses...

The 40 cm tall early horse Hyracotherium (= Eohippus) was widely distributed along the northern hemisphere during the Early Eocene period, 55-45 millions years ago. Several species have been described. This small creature lived in forest environments, probably in herds.

The later Mesohippus was a bit larger, standing at 60 cm in height, with longer legs. The different species were distributed from the Late Eocene to the Middle Oligocene periods (40-30 MYA) throughout the forests of the North American continent.


Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Samrukia nessovi, the prehistoric giant bird from Kazakhstan

Fig 1.- Very hypothetical reconstruction of Samrukia nessovi.

In a recent article published in Biology Letters, Darren Naish and colleagues named a new genus and species of Mesozoic bird, Samrukia nessovi, based on two pieces of lower jaw. The remains, hosted at the Wyoming Dinosaur Center in Thermopolis (Wyoming, USA), have been collected in the Bostobynskaya Formation of Late Cretaceous (Santonian-Campanian) age in Southern Kazakhstan.

Due to the fragmentary nature of the fossils, there isn’t much that can be said about the animal, save one remarkable fact: Samrukia was a giant bird. Even a crude extrapolation given by the size of the fragment of the lower jaw places the total dimension of the animal somewhere around 2 meters in length. The bird might have been a large flightless animal mimicking the bipedal non-avian theropods or a giant of the airs, mimicking the huge pterosaurs of that time, who knows? One thing is sure: Mesozoic birds were more diverse than previously thought, reaching sizes rivaling those of the non avialian dinosaurs living alongside them.

Fig 2.- Phylogenetic tree of birds closest dinosaurian relatives. Adapted from D. Naish et al., 2011. Compare with Xu et al., 2011.

There is however an interesting detail in the new phylogenetical analysis that was published alongside the paper in the supplementary electronic document. As in the Xu et al. paper mentioned in my previous post, the former “archetypal” ancestral bird, Archaeopteryx is knocked out of its perch as an Avialian but this time, it appears as a basal Paravian outside both the Avialae and the Deinonychosauria, alongside the Scansoriopterygids. As for Samrukia, the phylogenetic analysis shows that it was not quite a modern bird (Neornithes) but pretty close.

More about Samrukia on Tetrapod Zoology by the lead author of the paper himself.

References:

Darren Naish, Gareth Dyke, Andrea Cau, François Escuillié and Pascal Godefroit. 2011. A gigantic bird from the Upper Cretaceous of Central Asia. Biology Letters,  in press.

X. Xu, H. You, K. Du and F. Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475:465-470.


Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Xiaotingia zhengi or is Archaeopteryx still a bird?

Fig 1.- A reconstruction of Xiaotingia zhengi.

Xiaotingia zhengi is a new small carnivorous theropod dinosaur discovered in the Late Jurassic Tiaojishan Formation of the western Liaoning province of China. It is known from a single articulated skeleton missing the tail and part of the left leg, and preserved in a slab that also contains some feather impressions.

Fig 2.- Anchiornis huxleyi, a taxon previously described as a troodont, is closely related to Xiaotingia and Archaeopteryx.

The intriguing part of the story published last month in the journal Nature is less the description of the new fossil itself than the resulting cladistic analysis that followed. Xiaotingia was found to be closely related to the famous dinosaur-bird transitional fossil Archaeopteryx lithographica from Bavaria, Germany, and to another taxon described in 2009, Anchiornis huxleyi. Anchiornis had its share of fame last year when it became the first dinosaur to reveal its true colors from the examination of fossilized pigments found in the feather impressions. But Anchiornis was at that time classified as a flying dinosaur belonging to the troodontid family.

Fig 3.- Archaeopteryx lithographica, the "ancestral" bird, was actually a deinonychosaurian dinosaur related to Velociraptor. Note, the position of the wings is too high in this reconstruction.

The new cladistic tree proposed by Xing Xu and colleagues places Archaeopteryx, Anchiornis and the novel taxon Xiaotingia within the same family, the Archaeopterygidae and nests them at the base of the Deinonychosaurians, the group that contains such celebrities as Velociraptor, Deinonychus, Troodon and Utahraptor, and away from the ‘sister” branch (the Avialae) that lead to the modern birds. Archaeopterygidae is then a third and the most basal family that constitutes the Deinonychosaurians, along with the more derived Troodontids (Troodon and friends) and Dromaeosaurs (Velociraptor and friends). The real story behind the discovery of Xiaotingia is therefore that it knocks Archaeopteryx out of the genealogical tree that lead to the modern birds, a position that it held for a century and half! The true ancestors of birds, were more closely related to such oddities as the strange Scansoriopteryids and perhaps other dinosaurs such as the beaked Oviraptosaurs. This leads to the interesting possibility that an herbivorous rather than a carnivorous diet was an ancestral trait for birds.

Fig 4.- Phylogenetic tree of the ancestor of birds and their closest relatives (After Xu et al., 2011). Archaeopteryx does no longer belongs to Aves (Birds in the traditional sense).

As a matter of fact, the position of Archaeopteryx as the ancestor of all birds was precarious for some times now. The close relationship of Archaeopteryx with the Deinonychosaurians has been suspected for quite a while, with such discoveries as the four-winged flying sensation called Microraptor and other small “dromies”. The new cladistic analysis is just confirming a trend that started some two decades ago. Overall the new analysis by Xu and colleagues is making perfect sense: a number of traits that Archaeopteryx possesses are more akin to Deinonychosaurians than to Avialians. Archaeopteryx for instance has a slender shallow snout like the Deinonychosaurians and quite unlike basal avialians such as Epidexipteryx and Sapeornis and Oviraptosaurs who tend to have short and blunt snouts. Many details of the skeletal anatomy, such as the dimension and shape of the different openings in the skull (antorbital fenestra, premaxillary fenestra, …) shape and proportions of different bones (such as the lacrimal in the skull, the pubis, metatarsals, etc…) all point to Deinonychosaurian affinities for the Archaeopterygids.

Now to the vexed question as whether Archaeopteryx could still be considered a bird or not, the most we can say is that it all depends on how you define “bird”. In the traditional sense (as “birds”=Aves), Archaeopteryx is not a bird anymore. But using a broader definition (for instance, “birds”= Paraves (Avialae+ Deinonychosauria)), Archaeopteryx would still be considered a bird, but so should be all Archaeopteryx closest relatives, Velociraptor, Microraptor, Deinonychus and co. Anyway, the fact that a small feathered dinosaur related to Velociraptor could have been mistaken for the  “Urvogel”, the ancestral bird for well more than a century, tellingly shows how intimate the connection between the two groups is. Birds really are the last surviving group of dinosaurs, so get over it and move on, folks!


References:
Xing Xu, Hailu You, Kai Du and Fenglu Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475: 465–470.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.