Baby Limusaurus had teeth!

This is pretty remarkable.
Wang et al. 2016 reported on a growth series for Limusaurus (Xu et al. 2009; Jurassic, Oxfordian; 1.7m in est. length; IVPP V 15923; Figs. 1-5,) “the only known reptile to lose its teeth and form a beak after birth.”  

You might remember
Limusaurus became famous earlier for its tiny forelimbs complete with a digit 0 medial to digit 1, that made theropod workers go bonkers because they assumed the digits present were 1-4, not 0-3.

Figure 2. Limusaurus also has four fingers and a scapula with a robust ventral area, like Majungasaurus, but those four fingers are not the same four fingers found in Majungasaurus.

Figure 1. Limusaurus also has four fingers and a scapula with a robust ventral area, like Majungasaurus, but those four fingers are not the same four fingers found in Majungasaurus.

Wang et al. report,
“The available data are important for understanding the evolution of the avian beak.” Except… Limusaurus is not close to the avian line of ancestry anyway you look at it. The LRT nests Limusaurus, with or without teeth, with Khaan, a toothless, beaked oviraptorid. Wang et al. nest Limusaurus with Elaphrosaurus (Fig. 3) even though Khaan is part of their taxon list. So something is not scored right. Not sure about the discrepancy, but some of that could be due to the misidentification of manual digits 0-3.

Figure 3. Khaan, an oviraptorid that nests with Limusaurus in the large reptile tree AND the repaired Cau, Brougham and Naish tree.

Figure 2. Khaan, an oviraptorid that nests with Limusaurus in the large reptile tree AND the repaired Cau, Brougham and Naish tree.

Wang et al. report,
“The ontogenetically variable features (e.g. teeth/no teeth, etc.) have little effect on its phylogenetic position.” The LRT agrees. Wang et al. report that no matter which ontogenetic stage is tested for Limusaurus, it always nests with or near the ceratosaur, Elaphrosaurus (Fig. 3).The LRT disagrees.  In other words, with or without teeth, the topology does not change. In the LRT  toothed juvenile Limusaurus also nested with Khaan. Toothed Juravenator and Sinosauropteryx nest as sisters to that clade. The large Compsognathus specimen CNJ79 (Fig. 6) was a basal taxon. All of these sisters are closer to Limusaurus in size and morphology than is Elaphrosauru (Fig. 3).

Figure 3. Elaphrosaurus is known from a partial skeleton lacking a skull.

Figure 3. Elaphrosaurus is known from a partial skeleton lacking a skull. Adult Limusaurus added to scale. Wang et al. consider these two to be sister taxa among basal theropods, which is not confirmed by the LRT.

The ontogenetic series of Limusaurus
is shown in figure 4. Not all the specimens are complete. None are shown to scale. All are portrayed as tiny rough tracings. I think this lack of detail is one shortcoming of the paper.

Figure 4. Specimens attributed to Limusaurus, not to scale.

Figure 4. Specimens attributed to Limusaurus, not to scale, from Wang et al. 2016.

Wang et al. also provided
reconstructions of a juvenile and adult Limusaurus (Fig. 5). Unfortunately, Wang et al. filled in all the missing bones and gave both reconstructions something of a generic theropod character, lacking some of the traits unique to this genus.

Limusaurus reconstructions from Wang et al. 2016, to scale and not to scale.

Figure 5. Limusaurus reconstructions from Wang et al. 2016, to scale and not to scale. The angle of the pubis is difficult to determine.

That Limusaurus juveniles had teeth
and adults did not, tells us less about the avian line and more about the oviraptorid line of theropod dinosaurs.

Figure 1. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

Figure 6. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

References
Wang S, Stiegler J, Amiot R, Xu W, Du G-H, Clark JM, Xu X 2016. Extreme ontogenetic changes in a ceratosaurian theropod. Currently Biology 27:1-5 plus SupData.

Full scale models from the vault

Back in the day
when I was writing and illustrating dinosaur books (1988~1992) I also built a few full scale models that I intended to use as subjects for paintings and museum displays. Here are most of them. Other models include the pterosaur skeletons you can see here.

Figure 1. Brachiosaurus skull, carved out of wood. Full scale.

Figure 1. Brachiosaurus skull, carved out of wood. Full scale.

At this point in my life
(1990s) the work (paintings / illustrations) was considered ‘acceptable.’ Even my papers were ‘acceptable.’ Unfortunately, when I started applying phylogenetic analysis to taxa and discovering new and overlooked relationships (published at ReptileEvolution.com, ) my work and manuscripts were no longer considered ‘acceptable,’ despite the fact that early discoveries made here are being re-discovered and validated years later by PhDs.

FIgure 2. Camarasaurus baby model. Full scale.

FIgure 2. Camarasaurus baby model. Full scale.

This Dimorphodon
(Fig. 3) was among the first of the models, based on Kevin Padian’s 1983 running illustrations.

Figure 3. Dimorphodon skull with dog hair for pycnofibers.

Figure 3. Dimorphodon skull with dog hair for pycnofibers.

Not sure why I produced this plesiosaur
because it took up a bunch of garage space and only entertained the mailman. Ultimately it was purchased by the AMNH, but never put on display. Where it is now is anyone’s guess.

Figure 4. Plesiosaur model. Full scale.

Figure 4. Plesiosaur model. Full scale. See figure 5 for the face.

Much of this plesiosaur
was fashioned at the late Bob Cassilly studios, who was a famous St. Louis sculptor and founder of The City Museum. Bob contacted me after seeing my book, Giants, because he had been commissioned to produce some of the giant marine animals pictured therein. Through that friendship in the 1990s, I was able to study specimens, including Sharovipteryx and Longisquama, from the traveling Russian Dinosaur Exposition that came to the City Museum for their first stop.

Figure 5. Plesiosaur model head detail. Full scale. Teeth are tree thorns.

Figure 5. Plesiosaur model head detail. Full scale. Teeth are tree thorns.

Among the smaller full scale models
is this sparrow-sized Pterodactylus in a bipedal pose (Fig. 6), ready to take flight.

FIgure 6. Pterodactylus scolopaciceps (n21) model. Full scale.

FIgure 6. Pterodactylus scolopaciceps (n21) model. Full scale. Later I learned that this genus was plantigrade (flat-footed), when quadrupedal. This one is about to take flight from a bipedal configuration. Digitigrady at this instance would have given Pterodactylus a bit more power in its initial leap during take-off.

And based on the evolution book

From the Beginning, these three (Fig. 7) are fleshed out steps in the evolution of tetrapods, cynodonts, mammals and man. Ichthyostega is a bit out of date now.

Figure 7. Ichthyostega, Osteolepis and Thrinaxodon, all more or less ancestral to humans. Full scale.

Figure 7. Ichthyostega, Osteolepis and Thrinaxodon, all more or less ancestral to humans. Full scale.

References
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.

Feathered T-rex video: Excellent!*

The best video* I’ve seen on feathered dinosaurs.
*But note: their gliding Anchiornis forgot how to flap. Flapping came first. Then flapping with bipedal climbing. Then flapping with flying. Birds don’t come by gliding except to rest while airborne. Same with bats (if any glide ever). Same with pterosaurs. Let’s take gliding out of the equation for the origin of flight. That’s widespread antiquated thinking not supported by evidence. If you glide you do not flap. If you flap, some of your ancestors may learn to glide.

Click here or on the image to play.

Hypsibema missouriensis – a Late Cretaceous Appalachia duckbill dinosaur

Figure 1. Model of Hypsibema missouriensis, a hadrosaurid dinosaur

Figure 1. Model of Hypsibema missouriensis, a hadrosaurid dinosaur

Hypsibema missouriensis
(Cope 1869; Gilbert and Stewart 1945; Gilbert 1945; Baird and Horner 1979; Darrough et al. 2005; Parris 2006; Campanian, 84-71 mya, Late Cretaceous) is a fairly large hadrosaurid dinosaur discovered in 1942, at what later became known as the Chronister Dinosaur Site near Glen Allen, Missouri. At present this literal pinprick in the map of Missouri is the only site that preserves dinosaur bones.

Figure 2. Where the Hypsibema maxilla chunk came from on the skull of Saurolophus.

Figure 2. Where the Hypsibema maxilla chunk (Figure 3) came from modeled on the skull of Saurolophus.

Small pieces of broken bone and associated caudals and toes
were first discovered when digging a cistern. They had been found about 8 feet (2.4 m) deep imbedded in a black plastic clay. The area is in paleokarst located along downdropped fault grabens over Ordovician carbonates.

Gilmore and Stewart 1945 described a series of Chronister caudal centra (now at the Smithsonian) as sauropod-like, reporting, “The more elongate centra of the Chronister specimen, with the possible exception of Hypsibema crassicauda Cope, and the presence of chevron facets only on the posterior end appear sufficient to show that these vertebral centra do not pertain to a member of the Hadrosauridae.”

First named Neosaurus missouriensis,
the caudals were renamed Parrosaurus missouriensis by Gilmore and Stewart 1945 because “Neosaurus” was preoccupied. The specimen was allied to Hypsibema by Baird and Horner 1979.

Figure 3. Back portion of a Hypsibema maxilla showing tooth root grooves and cheek indention close to jugal.

Figure 3. Back portion of a Hypsibema maxilla showing tooth root grooves and cheek indention close to jugal.

Back in the 1980s
I enjoyed going to the Chronister site with other members of the local fossil club, the Eastern Missouri Society for Paleontoogy. I was lucky enough to find both a maxilla fragment (Fig. 3) and a dromaeosaurid tooth. I remember the horse flies were pesky and  one morning, before the other members got there, I was met by a man with a shot gun who relaxed when I identified myself. A friend found a series of hadrosaur toe bones, each about as big as a man’s hand (sans fingers). The bone was so well preserved you could blow air through the porous surfaces.

References
Baird D and Horner JR 1979. Cretaceous dinosaurs of North Carolina. Brimleyana 2: 1-28.
Cope  ED 1869.
Remarks on Eschrichtius polyporusHypsibema crassicaudaHadrosaurus tripos, and Polydectes biturgidus“. Proceedings of the Academy of Natural Sciences of Philadelphia 21:191-192.
Darrough G; Fix M; Parris D and Granstaff B 2005.
 Journal of Vertebrate Paleontology 25 (3): 49A–50A.
Gilmore CW and Stewart DR 1945. A New Sauropod Dinosaur from the Upper Cretaceous of Missouri. Journal of Paleontology (Society for Sedimentary Geology 19(1): 23–29.
Gilmore CW 1945. Parrosaurus, N. Name, Replacing Neosaurus Gilmore, 1945. Journal of Paleontology (Society for Sedimentary Geology 19 (5): 540.
Parris D. 2006. New Information on the Cretaceous of Missouri. online

wiki/Hypsibema_missouriensis
bolinger county museum of natural history
More info and links

Carrano et al. 2012: Basal Tetanurae interrelations

The classification of theropods
has been going on for a hundred years, spurred every year by the discovery of new taxa. Before computers the main division was based on size. The use of software has clarified that issue.

Several years ago,
Carrano, Benson and Sampson (2010) undertook a large study of theropod dinosaurs, focusing on the basal Tetanurae (closer to birds than to Ceratosaurus), up to and not including Coelurosauria (Compsognathus, Ornitholestes and further derived taxa including birds and kin. The authors note: “Tyrannosauridae is now universally included within Coelurosauria (Novas 1991a; Holtz 1994a), whereas ceratosaurs and coelophysoids are basal to Tetanurae.”

They also note, “The placement of many individual taxa within any of these frameworks also varies. ‘Megalosaurs’ pose an even greater and more complex problem. Many of the taxa that have at one time been referred to Megalosauridae have now been dispersed elsewhere, but a large number of putative megalosaur species remain.”

“In summary, although a great deal of progress has been achieved in recent years (measured mainly by increased consensus), several points of uncertainty remain in tetanuran phylogeny and are therefore of primary interest here. These are: (1) whether spinosauroids (= megalosauroids) and allosauroids form a clade, or are serially arranged outside Coelurosauria; (2) whether ‘megalosaurs’ form a valid clade and, if so, its membership; (3) placement of fragmentary forms of potential geographic and temporal importance; and (4) placement of relatively well known but problematical forms (e.g. Cryolophosaurus, Marshosaurus, Monolophosaurus, Neovenator and Piatnitzkysaurus).”

Their work involved firsthand examination
of hundreds of theropod specimens, but no reconstructions were made. Looking at hundreds of specimens is a very good thing, but reconstructions are the notes that let the reader know how bones were interpreted. Without them one must laboriously go through the raw numbers to check for accuracy. No one wants to do that. Reconstructions are a sort of shorthand enabling one to quickly make comparisons of hundreds of characters.

Zanno and Makovicky (2013) recovered a virtually identical theropod tree topology.

In counterpoint
The large reptile tree (subset: Fig. 1) keeps growing without changing topology. Perhaps it offers some insight into theropod relations. Some of the stability of this tree may be due to the inclusion set. Some taxa are tested together here for the first time. There are fewer theropod taxa here than in the works referenced below, but several theropod taxa are included here that are not included in the referenced works.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs. See the large reptile tree for included taxa not shown here.

References
Carrano MT, Benson RBJ and Sampson SD 2012. The phylogeny of Tetanurae (Dinosauria: Theropoda). Journal of Systematic Palaeontology 10(2):211–300.
Zanno L and Makovicky PJ 2013. Neovenatorid theropods are apex predators in the Late Cretaceous of North America. Nature Communications | 4:2827 | DOI: 10.1038/ncomms3827 |www.nature.com/naturecommunications

They’re out there somewhere!

Back in the ’90s, 
I built several full scale prehistoric reptile models out of wood, wire, foam, glass (eyes) and what have you. Two of them are shown here (Fig. 1).

Figure 1. Baby Camarasaurus and featherless Deinonychus models built by David Peters in the 1990s.

Figure 1. Baby Camarasaurus and featherless Deinonychus models built by David Peters in the 1990s.

At the time, 
like the the extinct Steve Czerkas and the extant Charlie McGrady, I wanted to be build dinosaurs, not just illustrate them in books. At the time, St. Louis did not have a Science Museum and that’s when (so I was told) you are supposed to get in on the ground floor. Also at the time the late sculptor Bob Cassilly was building squids, pterosaurs, sharks and rays for the St. Louis Zoo based on illustrations in my book Giants. (Bob was instrumental in bringing Sharovipteryx, Longisquama and the other Russian dinosaur exhibit to St. Louis.) Alas, that phase fizzled and the writing of papers followed. Early on you’re driven by enthusiasm and reined in by naiveté. In evolutionary terms, it worked out for that time and place.

Along with
the baby Camarasaurus and adult Deinonychus, I built a plesiosaur, Tanystropheus, fuzzy Dimorphodon, Pterodactylus and the several pterosaur skeletons seen here. The fleshed out sculptures went to the AMNH in NYC. The baby sauropod went to Martin Lockley in Colorado. The skeletons all went to Mike Triebold. Many artists want to see their art hanging in museums. Well, it happened to me, sort of, with those pterosaur skeletons. They’re out there, all over the world. The AMNH ultimately decided to display only skeletons in their renovated prehistoric displays and sold off what they had purchased.

I have no idea
where the various pieces are now or what shape they are in. But it was fun for awhile and the mailman probably told his kids about the address that had dinosaurs under the carport. Now a longer list of illustrated and animated prehistoric reptiles can be found on the Internet here.

Agilisaurus and the origin of the Pachycephalosauridae

Stegoceras validum (Lambe 1902; Late Cretaceous, Late Campanian; 75mya; 2m length; Fig. 1) was a basal dome-head dinosaur, or pachycephalosaur. Traditionally pachycephalosaurs have been linked to to stegosaurs, like Stegosaurus, troodontids like Sinornithoides, and ceratopsians, like Triceratops, but those are not supported in the large reptile tree (subset Fig. 4).

In the large reptile tree
Stegoceras was recovered as a sister to Agilisaurus (Peng 1990; ZDM 6011; Middle Jurassic; 1.2m length; Figs. 2-4).

In Stegoceras
the nares face somewhat forward, as in Agilisaurus. Similarly the forelimbs are tiny on this biped. The palpebral bones are incorporated into the skull itself. The antorbital fenestra is no longer visible. The dorsal and caudal ribs are quite wide, giving this dinosaur a wider than deep torso and tail first noted by Greg Paul, who kindly provided permission for his famous reconstruction (Fig. 1). The posterior tail is stiffened with ossified tendons originally thought to be gastralia.

Figure 1. Stegoceras, a basal pachycephalosaur from the Mid-Cretaceous is derived from a sister to Agilisaurus.

Figure 1. Stegoceras, a basal pachycephalosaur from the Mid-Cretaceous is derived from a sister to Agilisaurus.

Sullivan 2003 writes,
“Pachycephalosaurian dinosarus, known primarily fro their unusually thickened crania, are perhaps the most enigmatic and poorly understood dinosaurs.” Sullivan, like many traditional paleontologist, used ceratopsids for his phylogenetic outgroup. Traditionally pachycephalosaurs and ceratopsids have been lumped in the clade “Marginocephalia” (Sereno 1986). The large reptile tree (subset Fig. 3) does not support that nesting. Instead, the odd Agilisaurus nests with Stegoceras. It shares many traits including incipient anteriorly facing nares, small fore limbs and a long tail. The presence of upper temporal fenestrae in Stegoceras,though tiny, mark this as a basal pachycephlosaur.

Sereno (1986)
based the taxon on four synapomorphies (listed before the publication of Agilisaurus, which does or could share all 4 traits):

  1. narrow parietal shelf
  2. posterior squamosal shelf
  3. short posterior premaxillary palate
  4. short postpubic process (the original retroverted pubis sans the prepubic process)

The most basal member of the Marginocephalia
is reported to be Stenopelix, which we looked at earlier here. With current data,
the clade “Marginocephalia” has no utility because pachycephalosaurs do not nest with ceratopsians to the exclusion of all other taxa.

Sullivan continues
“It is clear that pachycephalosaurids appear rather abruptly in the fossil record (the Santonian). The origin of this group, and the directionality in dispersals of its taxa can only be speculative based on current (2003) information.”

Figure 1. The skull of Agilisaurus (Late Jurassic) provides the bauplan for the skull of more derived pachycephlosaurs, like Stegoceras.

Figure 1. The skull of Agilisaurus (Late Jurassic) provides the bauplan for the skull of more derived pachycephlosaurs, like Stegoceras. Note the anteriorly facing nares. The palpebral bone is in two parts here.

Agilisaurus is an ornithischian oddball.
And, as in other phylogenetic enigmas, like Longisquama and Sharovipteryx, the oddballs (in this case, Agilisaurus + pachycephlosaurs) nest together. The enigmatic structures suddenly become synapomorphies when sister taxa are found to share apparent autapomorphic (unique) traits.

Figure 3. Agilisaurus, like Stegoceras, was a biped with tiny forelimbs and a long tail, providing the blueprint for later pachycephalosaurs.

Figure 3. Agilisaurus, like Stegoceras, was a biped with tiny forelimbs and a long tail, providing the blueprint for later pachycephalosaurs. Note the broad fronts and tiny parietals.

The large and broad frontals
of Agilisaurus, together with the relatively small parietals are precursor traits to the dome skulls of pachypleurosaurs. At this point, and with the limited number of taxa in the ornithischian subset of the large reptile tree, this is how relationships are recovered. Xu et al. 2006 in their paper on Yinlong, recovered Agilisaurus basal to heterodontosaurs in the branch leading to their “Marginocephalia.”

Figure 4. The phytodinosauria. Here Stegoceras and the pachycephalosaurs nest with the Middle Jurassic Agilisaurus.

Figure 4. The phytodinosauria. Here Stegoceras and the pachycephalosaurs nest with the Middle Jurassic Agilisaurus.

One of the problems traditional paleontologists have
with the Ornithischia is they don’t know which taxa are basal. They often use Lesothosaurus, rather than Chilesaurus and Daemosaurus as a basal taxon. Here Lesothosaurus is basal to Stegosaurus through Scutellosaurus. We talked about Chilesaurus earlier here. Traditional paleontologists don’t recognize the clade Phytodinosauria, either. When they do, everything will become clear.

I’d like to know more about
Micropachycephylosaurus, a tiny taxon with a long name, reportedly close to the origin of the Ceratopsia, but I need data.

References
Barrett PM, Butler RJ and Knoll F 2005. Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. Journal of Vertebrate Paleontology 25:823-834.
Currie PJ and Padian K 1997. Encyclopedia if Dinosaurs. Academic Press.
Dodson P. 1990. Marginocephalia. Pp. 562-563 in The Dinosauria (Weishampel DB, Dodson P and Osmólska H, eds.) University of California Press, Berkeley.
Lambe LM 1902. New genera and species from the Belly River series (Mid-Cretaceous). Contributions to Canadian Paleontology. Geological Survey of Canada 3:25-81.
Lambe LM 1918. The Cretaceous genus Stegoceras, typifying a new family referred provisionally to the Stegosauria. Transactions of the Royal Society of Canada. 12(4):23-36. Peng G-Z 1990. New small ornithopod (Agilisaurus louderbacki gen. et sp. nov.) from Zigong, China. Newsletter of the Zigong Dinosaur Museum 2: 19–27.
Peng G-Z 1992. Jurassic ornithopod Agilisaurus louderbacki (Ornithopoda: Fabrosauridae) from Zigong, Sichuan, China. Translated by Will Downs. Vertebrata Palasiatica 30: 39-51.
Sullivan RM 2003. Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae). Journal of Vertebrate Paleontology 23 (1): 181–207.
Xu X, Forster CA, Clark JM and Mo J 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. Proceedings of the Royal Society B: Biological Sciences 273: 2135–40. doi:10.1098/rspb.2006.3566. PMC 1635516. PMID 16901832.

wiki/Agilisaurus
wiki/Stegoceras