Alvarezsaurs in the Lori matrix

This time our topology is-

 

I provide a new definition for Alvarezsauroidea that adds Therizinosaurus as an external specifier since I find it most parsimonious for Therizinosauria to be its sister group, and uses Alvarezsaurus as the internal specifier unlike Sereno's that uses Shuvuuia- (Alvarezsaurus calvoi < - Ornithomimus velox, Therizinosaurus cheloniformis, Passer domesticus) .  Alvarezsauroids have had a controversial phylogenetic placement, with the Lori matrix recovering them as basal maniraptorans sister to therizinosaurs.  Yet they can be outside therizinosaurs plus pennaraptorans in 3 steps, become arctometatarsalians in 4 steps (can bring therizinosaurs or not), non-maniraptoriforms in 6 steps (they bring therizinosaurs), closer to pennaraptorans than therizinosaurs in 6 steps, paravians in 11 steps (therizinosaurs move with), closer to Compsognathus than to birds in 15 steps, closer to birds than deinonychosaurs in 27 steps, and closer to Archaeopteryx and other birds than to dromaeosaurids and troodontids in 30 steps.

Fukuivenator is an odd taxon, recovered here as the basalmost alvarezsauroid.  But it can be a therizinosaurian in only two steps, and outside Maniraptoriformes in 4 steps (it emerges in Coeluridae).  One thing I don't think it is is a dromaeosaurid, as that takes 27 more steps, and getting it into Paraves or Pennaraptora requires 11 and 7 steps respectively.  Still, I wouldn't be surprised to see this taxon work its way around the base of Maniraptoriformes once an osteology comes out.

Shuvuuia deserti IGM 100/975 axial elements in ventral view and pelvis in dorsal view (courtesy AMNH).

Nqwebasaurus was recently redescribed by Sereno (2017), which I incorporated into its scorings.  Choiniere et al. (2012) recovered it in Ornithomimosauria, but note most of the characters they list to support that are also said to be present in alvarezsauroids.  Even they could place it in Alvarezsauroidea with only 4 steps.  The Lori matrix needs 6 steps to place it in Ornithomimosauria, which I think is higher partially due to it finding Pelecanimimus to be an alvarezsauroid too.  So similarities between the two like their teeth being in a common groove and maxillary teeth being confined to the anterior third of the bone are no longer ornithomimosaur-like.  As recently noted by Cerroni et al. (2019), this makes more sense biogeographically as well.  Oh, and note that the Lori matrix found Afromimus to be a ceratosaur as in that paper.  In any case, Nqwebasaurus takes 10 steps to move to Compsognathidae, and 7 steps to move sister to Pennaraptora.

As for Pelecanimimus itself, it seems plausibly alvarezsauroid if you think about it.  The skull is famously similar to Shuvuuia, the posterior tympanic recess is in the otic recess, ossified sterna are otherwise unknown for ornithomimosaurs, the long manual digit I was always out of place compared to Harpymimus, and Europe makes more sense for otherwise Gondwanan clades in the Cretaceous.  Now if only someone would release Perez-Moreno's thesis describing it in detail...

Shuvuuia deserti IGM 100/975 pectoral and forelimb elements. Note the tiny phalanx from digit II or III at the bottom (courtesy AMNH).

Patagonykus and Bonapartenykus are usually closer to parvicursorines than Alvarezsaurus and Achillesaurus, but the Lori matrix found them just outside Alvarezsauridae instead.  Interestingly, Xu et al. (2018) recovered the same results.  It takes 3 steps to move Patagonykus closer to parvicursorines, and 4 steps to join Alvarezsaurus and Patagonykus to the exclusion of parvicursorines as in Alifanov and Barsbold (2009).  Xu et al. recover these in 5 and 7 steps respectively, and the most recent version of Longrich and Currie's alvarezsaurid matrix (Lu et al., 2018) recovers a basal Patagonykus and a basal Parvicursorinae in 3 steps each.

One odd result is that the newly described Xiyunykus and Bannykus fall in Patagonykinae too.  Yet only 2 steps move them outside the Patagonykus plus Parvicursorinae clade, where they form a clade.  Another step breaks that up to place Xiyunykus more basal as in Xu et al..  Them being basal certainly fits better stratigraphically, and Xu et al. use several characters designed for alvarezsauroids that the Lori matrix didn't include yet.  Hopefully full osteologies will be published as well.

Mononykus olecranus cast YPM 56693 (of holotype) pes in plantar view (courtesy of Senter).

A patagonykine Achillesaurus as suggested by Agnolin et al. (2012) takes 7 additional steps in the Lori matrix where it instead emerges just closer to parvicursorines than Alvarezsaurus.  On the other hand, only a single step joins it with Alvarezsaurus as in Longrich and Currie (2009) and only 2 steps makes it just further from parvicursorines than Alvarezsaurus as in Xu et al. (2018).

Alnashetri is known from type hindlimb material, but now also from MPCA 377, a nearly complete specimen with interesting characters like flat and unfused sternal plates.  Makovicky et al. (2016) used this data to recover it as the sister group to Alvarezsauridae, and while the few published details left it more derived in the Lori tree, it can go to a more basal position with only two steps.  It should be interesting to compare to e.g. Bannykus once it is published.

Mononykus olecranus cast YPM 56693 (of holotype) (courtesy of Senter).

The arctometatarsal clade has a unique topology, but no other analysis has included nearly as many characters or all of these taxa, with Lu et al. omitting Albinykus and Ceratonykus among non-fragmentary specimens, and Xu et al. omitting the more recently described Qiupanykus.  Enforcing the Lori topology in Lu et al.'s matrix is only 5 steps longer, and doing so in Xu et al.'s matrix is only 6 steps longer.  On the other hand, Xu et al.'s topology is so unresolved at this level, the only difference in mine is placing the Albinykus plus Xixianykus clade basally near Albertonykus, which takes 5 steps to do in the Lori matrix.

It should be noted that Lu et al.'s illustrated topology (their Figure 3) is not their matrix's real result, as they did not fully analyze tree space.  Instead of 20 trees, there are 214 trees.  These differ in that Albertonykus, YPM 1049 and undescribed 41HIII-0104 can fall out anywhere more derived than Patagonykus, and that Parvicursor, the Tugriken Shireh taxon, Shuvuuia and Mononykus form an unresolved polytomy.  This leaves Linhenykus, Qiupanykus and Xixianykus unresolved between that polytomy and Patagonykus, which is perfectly compatible with the Lori topology.  This may also show that the small alvarezsauroid-specific matrix of Longrich and Currie is insufficient given all the new taxa described since 2009.  YPM 1049 was far too fragmentary to include (distal metatarsal III) but I tried testing undescribed Quipa specimen 41HIII-0104.  Didn't make it into the publication, but here's its scorings-

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Tugriken Shireh parvicursorine (IGM 100/99) vertebrae and ilia in ventral view, forelimb and fibula in lower right (courtesy AMNH).

Interestingly, Agnolin et al., Xu et al. and the Lori analysis all recovered Albinykus sister to Xixianykus outside Parvicursorinae.  Wonder if that's a real signal?  Unfortunately, the only attempt to name this clade was Agnolin et al. who also recovered Ceratonykus in there and called it Ceratonykini.  Xu et al. place Ceratonykus closer to parvicursorines, while I found it more basal than either, sister to Qiupanykus which neither of the other studies used.  Forcing Ceratonykus sister to Albonykus plus Xixianykus takes 3 more steps in the Lori matrix.  Forcing Ceratonykus sister to Mononykus as in its original description (with or without Qiupanykus) takes 5 more steps.  As stated in the paper, we were the first analysis to include Hateg tibiotarsi Bradycneme and Heptasteornis.  While the former can fall into many positions in Maniraptora, the latter was resolved as an alvarezsaurid as proposed by Naish and Dyke (2004).  Note this used only the tibiotarsus and not alvarezsaurid-like distal femur FGGUB R.1957.  A single step moves Heptasteornis to Troodontidae.

We also provide an updated definition for Parvicursorinae (Mononykus olecranus + Parvicursor remotus), like Choiniere et al.'s (2010) but using species.   One accident of our definitional and discovery history is that all these newer arctometatarsal alvarezsaurids (Xixianykus, Albertonykus, Albinykus, Linhenykus, Qiupanykus, Ceratonykus, etc.) emerge outside the originally discovered and defined Parvicursorinae.  We could really use some clade defining taxa closer to Mononykus than Patagonykus, Alvarezsaurus or Achillesaurus.  In any case, I got a lot of experience with parvicursorine specimens, examining Shuvuuia and the Tugriken Shireh specimen IGM 100/99 in person, and having photos of high quality casts of Mononykus thanks to Senter.  I found the Tugriken Shireh taxon closer to Shuvuuia, but moving it closer to Parvicursor as in Longrich and Currie is just 1 step longer.

Tugriken Shireh parvicursorine (IGM 100/99) vertebrae and ilia in dorsal view, forelimb and fibula in lower right (courtesy AMNH).

Next time, therizinosaurs...

References-  Naish and Dyke, 2004. Heptasteornis was no ornithomimid, troodontid, dromaeosaurid or owl: The first alvarezsaurid (Dinosauria: Theropoda) from Europe. Neus Jahrbuch für Geologie und Paläontologie. 7, 385-401.

Alifanov and Barsbold, 2009. Ceratonykus oculatus gen. et sp. nov., a new dinosaur (?Theropoda, Alvarezsauria) from the Late Cretaceous of Mongolia. Paleontological Journal. 43(1), 94-106.

Longrich and Currie, 2009. Albertonykus borealis, a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: Implications for the systematics and ecology of the Alvarezsauridae. Cretaceous Research. 30(1), 239-252.

Choiniere, Xu, Clark, Forster, Guo and Han, 2010. A basal alvarezsauroid theropod from the early Late Jurassic of Xinjiang, China. Science. 327, 571-574. 

Agnolin, Powell, Novas and Kundrat, 2012. New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs. Cretaceous Research. 35, 33-56.

Makovicky, Apesteguia and Gianechini, 2016. A new, almost complete specimen of Alnashetri cerropoliciensis (Dinosauria: Theropoda) impacts our understanding of alvarezsauroid evolution. XXX Jornadas Argentinas de Paleontologia de Vertebrados. Libro de resumenes, 74.

Sereno, 2017. Early Cretaceous ornithomimosaurs (Dinosauria: Coelurosauria) from Africa. Ameghiniana. 54, 576-616.

Lu, Xu, Chang, Jia, Zhang, Gao, Zhang, Zhang and Ding, 2018. A new alvarezsaurid dinosaur from the Late Cretaceous Qiupa Formation of Luanchuan, Henan Province, central China. China Geology. 1, 28-35.

Xu, Choiniere, Tan, Benson, Clark, Sullivan, Zhao, Han, Ma, He, Wang, Xing and Tan, 2018. Two Early Cretaceous fossils document transitional stages in alvarezsaurian dinosaur evolution. Current Biology. 28, 1-8. DOI: 10.1016/j.cub.2018.07.057

Cerroni, Agnolin, Egli and Novas, 2019. The phylogenetic position of Afromimus tenerensis Sereno, 2017 and its paleobiogeographical implications. Journal of African Earth Sciences. DOI: 10.1016/j.jafrearsci.2019.103572

Hartman, Mortimer, Wahl, Lomax, Lippincott and Lovelace, 2019. A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ. 7:e7247. DOI: 10.7717/peerj.7247