The Theropoda: just a few (albeit heretical) changes to traditional trees

Adding taxa
is a method I have supported in order to discover taxonomic relationships among reptiles. The large reptile tree (theropod subset in Fig. 1) has now passed 650 taxa. The theropod subset has been considered at odds with traditional trees. But when you really look at it, maybe, not so much.

Figure 1. Theropod subset of the large reptile tree. Unresolved clades are resolved in heuristic analyses. Here traditional clades are named. A few taxa nest somewhere other than their traditional nestings here. Click to slightly enlarge.

Figure 1. Theropod subset of the large reptile tree. Unresolved clades are resolved in heuristic analyses. Those are due to incomplete skeletons. Here traditional clades are named. A few taxa nest somewhere other than their traditional nestings here. Click to slightly enlarge.

I added four more theropods
to the large reptile tree and applied traditional names to various clades (Fig. 1). Those additions and all scoring corrections did not change the overall tree topology.

Tradition is upheld overall here
as the major clades: 1. Neotheropoda; 2. Avetheropoda/Averostra; 3; Tetanurae; 4. Maniraptora; 5. Paraves; 6. Deinonychosauria/Eumaniraptora; 7. Troodontidae; and 8. Birds/Aves appear in their traditional order and with most of their traditional taxa.

Heresy is introduced here

  1. A clade between Tawa and Coelophysis includes Marasuchus, Segisaurus and Procompsognathus, taxa too often omitted from traditional theropod trees.
  2. Several former compsognathids, including Juravenator, Sinosauropteryx, now nest as derived maniraptors close to Limusaurus + Khaan and another former compsognathid, Sinocalliopteryx, now nests with spinosaurs.
  3. Several former tyrannosauroids, including Proceratorsaurus, Dilong, Guanlong and Xiongguanlong now nest with spinosaurs.
  4. A former ornithomimid, Deinocheirus, now nests with spinosaurs.
  5. Several former dromaeosaurs, including Microraptor, Sinornithosaurus, Zhenyuanlong and Tianyuraptor now nest with tyrannosauroids.
  6. A former bird/dromaeosaur, Rahonavis now nests with basal therizinosaurs.
  7. A former ceratosaur, Limusaurus, now nests with oviraptors.
  8. Eotyrannus and Tanycolagreus nest together as basal Paraves.

The following taxa do not belong in theropod studies
because they are basal phytodinosaurs.

  1. Eodromaeus
  2. Eoraptor
  3. Daemonosaurus
  4. Chilesaurus

The problem for traditional theropod workers is
the above heretical sisters really do look like sisters, both overall and in detail. With 651 nesting opportunities, this is where they found maximum parsimony (the fewest changes to their morphology).

These nestings look like heresies, but they follow prior work

  1. Ornithomimosaurs and maniraptors were both derived from Compsognathidae (Compsognathus) according to Lee et al. 2014.
  2. A series of small troodontids give rise to birds according to Godefroit et al. 2013.
  3. Dilophosaurus nests with Coelophysis according to Sues et al., 2011.
  4. Others I missed? It’s better for everyone when I’m not the first to notice taxonomic similarities.

Added taxa
have, so far, only supported earlier clades from earlier large reptile tree topologies. There have been score changes, but that’s standard operating procedure when adding taxa. It goes to show that a pretty good tree CAN have scoring mistakes. The best tree, of course, has no mistakes.

It is so good to have photo references
to look over when trying to decide what an unidentified or misidentified crumb of bone might represent. I can’t imagine having to buy a ticket to go revisit a fossil every time I needed to see it again. The logistics would prove nightmarish. (You have to realize that NO ONE does this). Remember, no one is an expert on a fossil the moment they first see it. Spending time with data makes you an expert on it. How much of an expert do you need your experts to be?

References
Lee YN, Barsbold R, Currie PJ, Kobayashi Y, Lee HJ, Godefroit P, Escuillié F and Chinzorig T 2014. Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus. Nature 515 (7526): 257–260.
Godefroit P, Cau A, Hu D-Y, Escuillié, Wu, W-H and Dyke G 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498 (7454): 359–362.
Sues H-D, Nesbitt SJ, Berman DS and Henrici AC 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B 278 (1723): 3459–3464

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2 thoughts on “The Theropoda: just a few (albeit heretical) changes to traditional trees

  1. “A former ornithomimid, Deinocheirus, now nests with spinosaurs.”
    I am not going to spend a bunch of time picking at this post, but I will note that I don’t see any compete ornithomimids in your tree at all. So I would suggest you include some (there are plenty of well known ornithomimids) before you radically change the placement of a taxon. You do want to compare it to appropriate taxa, right?

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