Restoring and re-nesting Murusraptor

Traditional megaraptorans,
like Megaraptor namunhuaiquii (Novas 1998, Fig. 1) and Murusraptor barrosaensis (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; MCF-PVPH-411; Fig. 1), are currently only known from bits and pieces. Perhaps for these reasons Wikipedia reports, “the clade Megaraptora (Benson, Carrano and Brusatte 2010 ) has controversial relations to other theropods.”

According to Wikipedia
“Murusraptor is a megaraptoran, one of a group of large predatory dinosaurs whose exact classification remains disputed. Once believed to be dromaeosaurids, they have since been classified as either allosauroid carnosaurs or as tyrannosauroid coelurosaurs. While the discovery of Murusraptor does not clarify as of yet the placement of this group of theropods, the specimen does add further clarity to some aspects of megaraptoran anatomy and potentially, eventual classification of the Megaraptora within the theropod evolutionary tree.”

Definition
Megaraptora (Benson et al 2010) “The most inclusive clade comprising Megaraptor namunhuaiquii, but not Chilantaisaurus tashuikouensis.” 

Wikipedia reports,
“Megaraptorans were most diverse in the early Late Cretaceous of South America, particularly Patagonia. However, they had a widespread distribution. Fukuiraptor, the most basal (“primitive”) known member of the group, lived in Japan. Megaraptoran material is also common in Australia, and the largest known predatory dinosaur from the continent, Australovenator, was a megaraptoran.” 

Taxa traditionally included within Megaraptora:

  1. Megaraptor (known from a long maxilla and forelimb, Figs. 1, 2)
  2. Fukuiraptor (known from jaw fragments, coracoids, humeri, femur, acetabulum, two vertebrae
  3. Australovenator (known from a dentary, a few dorsal ribs, distal forelimbs and nearly complete hind limbs)
  4. Murusraptor (known from several skull elements and other bones Figs. 1, 2)

Of these, only two, Megaraptor and Murusraptor, are tested in the LRT.

Other megaraptoran traits according to Wikipedia

  1. “Their forelimbs were large and strongly built,
  2. The ulna bone had a unique shape (except Fukuiraptor).
  3. The first two fingers were elongated, with massive curved claws ,
  4. The third finger was small. 
  5. Megaraptoran skull material is very incomplete, but a juvenile Megaraptor described in 2014 preserved a portion of the snout, which was long and slender. 
  6. Leg bones referred to megaraptorans were also quite slender and similar to those of coelurosaurs adapted for running. 
  7. Although megaraptorans were thick-bodied theropods, their bones were heavily pneumatized, or filled with air pockets. The vertebrae, ribs, and the ilium bone of the hip were pneumatized to an extent which was very rare among theropods, only seen elsewhere in taxa such as Neovenator
  8. Other characteristic features include opisthocoelous neck vertebrae
  9. and compsognathid-like teeth.” 

Several of the above traits
are shared with other taxa. The LRT employes a suite of 231 shared, unique and often convergent traits to lump, split and ultimately nest all taxa. Surprisingly, even the poorly preserved, disarticulated and incomplete Megaraptor and Murusraptor found secure nodes.

Araciaga, Rolando, Novas and Agnolin 2019
bring us ‘new evidence about the phylogenetic relationships of Megaraptora.’ They report, “The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

From their abstract:
“Murusraptor is particularly similar to juvenile specimens of tyrannosaurids; both share: 1) lacrimal with a long anterior prosess; 2) corneal process and; 3) lateral pneumatic fenestra; 4) square and dorsoventrally low frontals; 5) parietals with well-developed sagittal and nuchal crests, among other features. The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

“Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary.

“Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp. include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded  dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor.”

A little backstory with links for more details:
Aerostean is a giant (9m) Late Cretaceous theropod with no skull material known. Orkorpator is a large (6m) Latest Cretaceous theropod includes only a post-orbital and quadratojugal for skull material and bits and pieces otherwise.

Figure 1. Murusraptor compared with related taxa to scale.

Figure 1. Murusraptor compared with related taxa to scale. Ghosted rostrum of Guanlong added to missing rostrum of Mururaptor.

Phylogenetic analysis
In the large reptile tree (LRT, 1415 taxa; Fig. 4) Megaraptor (Fig. 1) nests with the basal theropod, Sinocalliopteryx. Murusraptor (Fig. 1) nests between long-snouted Dilong and the long-snouted Guanlong / Spinosaurus clade.

One problem comes from
the hypothesis of relationships published by Coria and Currie 2016 that nests long-snouted Xiongguanlong, Dilong, Proceratosaurus and Guanlong with robust-snouted Tyrannosaurus, rather than with long-snouted spinosaurs. Even so, Coria and Currie 
nest Murusraptor with Megaraptor. The closest theropod also tested in the LRT is the finback allosaurAcrocanthosaurus. So, the Coria and Currie cladogram is different in most respects from the LRT. Coria and Currie also nest the giant horned theropod, Ceratosaurus, as a basalmost/outgroup taxon. In the LRT (Fig. 4) Ceratosaurus has no descendants.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale. The Rolando et al. restoration draws more on Megaraptor and Dilong.

In counterpoint to Coria and Currie 2016,
Novas et al. 2016 reported, “megaraptorids retained several of the manual features present in basal tetanurans, such as Allosaurus. In this regard, Megaraptor and Australovenator are devoid of several manual features that the basal tyrannosauroid Guanlong shares with more derived coelurosaurs (e.g., Deinonychus).” 

In the LRT,
(Fig. 4) Guanlong is closer to Allosaurus than to Tyrannosaurus.

Figure 4. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1.

Figure 3. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1. According to the LRT, Suchomimus is not related to Megaraptor, but is shown here to demonstrate the convergence.

According to the writers of Wikipedia,
the large compsognathid, Sinocallioteryx (Figs. 1-3) is not related to megaraptorids, despite the many similarities in the skull. Curiously, other long-snouted theropods with massive curved claws on their forelimbs, like Suchomimus (Fig. 3), are also not traditionally considered related to megaraptorids. I wish they were. Everyone wishes they were. However, I have to report results, no matter how controversial, as I have for the last eight years. That way, if I made mistakes, someone will tell me. If someone has forgotten certain taxa, perhaps next time they will add them.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

In conclusion
Murusraptor barrosaensis
  (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; Late Cretaceous) was originally considered a sister to Megaraptor and close to tyrannosaurs. Here (Fig. 4) Murusraptor nests between Dilong and Guanlong closer to spinosaurs. Megaraptor nests with Sinocalliopteryx, a basal theropod, not close to Murusraptor. Wherever other traditional megaraptorans (see list above) nest has not yet been tested in the LRT. We looked at the relationship of long-snouted theropods with spinosaurs, rather than tyrannosaurs earlier here.


References
Rolando AMA, Novas FE and Agnolin FL 2019. A reanalysis of Murusraptor barrosaensis Coria & Currie (2016) affords new evidence about the phylogenetical relationships of Megaraptora. Cretaceous Research. https://doi.org/10.1016/j.cretres.2019.02.021
Benson RBJ, Carrano MT and Brusatte SL 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic.
Naturwissenschaften 97(1): 71–78.
Coria RA and Currie PJ 2016. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE 11(7): e0157973. doi:10.1371/journal.pone.0157973
Novas FE 1998. Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia. Journal of Vertebrate Paleontology. 18: 4–9. doi:10.1080/02724634.1998.10011030
Novas FE, Rolando AMA and Agnolín FL 2016. Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy. Memoirs of Museum Victoria. 74: 49–61.
Porfiri JD, Novas FE, Calvo JO.; Agnolín FL.; Ezcurra MD and Cerda IA. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research. 51: 35–55.

wiki/Megaraptor
wiki/Murusraptor
wiki/Megaraptora

2 thoughts on “Restoring and re-nesting Murusraptor

  1. Just looked at this article, and I thought I should point something out. While it doesn’t contain a phylogeny (it is a relatively informal palaeo book, after all!), Holtz’s “Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages” does consider Megaraptor, at least, to be a member of the Spinosauroidea, if not Spinosauridae proper. While I’ve not seen it repeated elsewhere, the connection has been made.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.