It's time for the annual review of The Compact Thescelosaurus. As is traditional, there's a new sheet, which this year covers mosasaurs, as you might have guessed from the image. The classification diagram page has been updated as well. (Don't forget, Wednesday the 14th is also National Fossil Day!)
Mosasaurus conodon, hanging out at the Science Museum.
For the purposes of this exercise, I covered Mosasauroidea, consisting of aigialosaurids and mosasaurids. This left out a few things that have sometimes been allied with mosasaurs historically, e.g., dolichosaurids. Something you may notice immediately is that the provenance columns ("I" through "L") are frequently rather heavily populated. Whether this is because mosasaur species often attained much more cosmopolitan distributions compared to the other groups I've covered, researchers are more comfortable identifying far-flung remains to established species, or a little of both, I can't say. There's also some additional geographic quirks to contend with. For example, places like Israel, Jordan, and Syria were then within the northeast corner of the African Plate (the Arabian Plate not yet having established itself), while the area encompassing Croatia and Slovenia was made up of free fragments of Gondwanan origin. As on other tabs, the place that yielded the type specimen is listed first, then the rest.
Another difference is, unlike dinosaurs or pterosaurs, the most prominent mosasaur genera contain
multiple species with at least some argument for validity, from two to as many
as nine. Possibly related to this, another thing I noticed while working through the
various species is that many of the genera do not plot out as monophyletic. I don't mean some piddling "species X occasionally clades with a
different genus." I mean "Prognathodon laughs at you and your pitiful notion of
monophyly," to mention a
recent example (e.g., Lively 2020 or Street et al. 2020). This is not a new thing,
either; you can see it in Bell (1997), the Ur-text of mosasauroid cladistic
analysis, in which Clidastes, Mosasaurus, Platecarpus,
and Prognathodon are all blissfully
paraphyletic. I could
have slapped quotes around everything but type species, but because I was in
Rome, I opted to do as the Romans do. Anyway, they're the new tab, there's 123 of them waiting for you, have fun! (If you like having historical perspective, download Russell 1967 to go along with it.)
Moving on to the review:
We last checked in October 13, 2019. Since then, there have been 113 entries on the Updates sheet. Among them are 58 new species plus one previously overlooked, 7 reevaluated existing species, 7 existing species moved to 6 new genera, 4 species sunk, 4 species moved to existing genera, 2 species removed, and whatever the heck it was I did with Paraophthalamosaurus, Yasykovia, and Nannopterygius. (Ichthyosaurs are terrible.)
Looking at the stratigraphic distribution, the Cretaceous again comes out on top. There were 2 new Middle Triassic species, 3 Upper Triassic, 1 from a Triassic unit of uncertain stratigraphic position, 2 Lower Jurassic, 1 Lower–Middle Jurassic, 4 Middle Jurassic, 6 Upper Jurassic, 2 Upper Jurassic–Lower Cretaceous, 11 Lower Cretaceous, 1 "Middle Cretaceous", and 25 Upper Cretaceous. For geography, Asia was the clear leader, with 19 new species. Next were South America with 12 and North America with 11, then Europe with 9, 5 from Africa (counting Mimodactylus libabensis from Lebanon, which, as above, was on the northeast end of the African Plate in the Cretaceous, but omitting 2 from Madagascar), and 2 from Madagascar. We have the same top three nations as last year, in the same order, but not the same totals: 15 from China, 8 from Argentina, and 7 from the United States. Behind them with 4 is Mongolia, and Morocco and the United Kingdom with 3. 5 nations came in with 2 (Brazil, Canada, Madagascar, Mexico, and Norway), and 8 with 1 (Chile, Ecuador, Germany, Lebanon, Lesotho, Portugal, Romania, and Switzerland).
In taxonomic terms, there are:
1 new choristodere species:
Heishanosaurus pygmaeus (not to be confused with Heishansaurus)
5 new ichthyosaur species:
Good year for ichthyosaurs.
1 new placodont species:
2 new plesiosaur species:
9 new pterosaur species:
All Cretaceous, but a fairly wide spread taxonomically speaking, with no one group dominating.
1 new dinosauromorph species:
Kongonaphon kely, a lagerpetid
20 new theropod species (classic dinosaur):
Xunmenglong yinliangis (not to be confused with Yunmenglong)
2 new basal sauropodomorph species:
8 new sauropod species:
"Omeisaurus" puxiani (quotes because of house rules regarding Omeisaurus proliferation)
Schleitheimia schutzi (which ended up here because of the definition of Sauropoda I use)
1 new uncommitted ornithischian species:
1 new thyreophoran species:
5 new ceratopsian species:
2 new ornithopod species:
Odd that neither was a hadrosaur, or even a large-bodied iguanodont.
1 overlooked species:
Lariasaurus sanxiaensis, a basal sauropterygian
7 reinstated or newly accepted species:
If it has quotes, it's probably just a housekeeping addition. Also, Chacaicosaurus cayi and Keilhauia nui were reinstated at the generic level.
7 existing species were moved to 6 new genera:
"Camposipterus" sedgwickii to Aerodraco
"Ornithopsis" greppini to Amanzia
"Ornithomimus" elegans to Citipes
"Ornithocheirus" capito and Coloborhynchus fluviferox to Nicorhynchus
"Orthomerus" weberae to Riabininohadros
"Ornithocheirus" wiedenrothi to Targaryendraco
If you were a species waiting to be transferred to a new genus, and your old genus was "Ornitho"-something, it was your year.
4 species that had their own listings were sunk:
"Colymbosaurus" sklerodirus considered indeterminate within Colymbosaurus
"Platypterygius" ochevi into Maiaspondylus cantabrigiensis
Sarcosaurus andrewsi into Sarcosaurus woodi
Sigilmassasasaurus brevicollis (including Spinosaurus maroccanus) into Spinosaurus aegyptiacus
4 species were moved to existing genera:
"Acanthopholis" macrocercus to Syngonosaurus
Asiamericana asiatica to Richardoestesia
"Ophthalmosaurus" cantabrigiensis to Maiaspondylus
Rubeosaurus ovatus to Styracosaurus
Finally, two species were removed:
Lukousaurus yini (considered pseudosuchian)
"Thecodontosaurus" subcylindrodon (no real evidence it was dinosaurian)
Bell, G. L., Jr. 1997. A phylogenetic revision of North American and Adriatic Mosasauroidea. Pages 293–332 in J. M. Callaway and E. L. Nichols, editors. Ancient marine reptiles. Academic Press, San Diego, California.
Lively, J. R. 2020. Redescription and phylogenetic assessment of 'Prognathodon' stadtmani: implications for Globidensini monophyly and character homology in Mosasaurinae. Journal of Vertebrate Paleontology, article e1784183. doi:10.1080/02724634.2020.1784183.
Russell, D. A. 1967. Systematics and morphology of American mosasaurs (Reptilia, Sauria). Bulletin of the Peabody Museum of Natural History 23.
Strong, C. R. C., M. W. Caldwell, T. Konishi, and A. Palci. 2020. A new species of longirostrine plioplatecarpine mosasaur (Squamata: Mosasauridae) from the Late Cretaceous of Morocco, with a re-evaluation of the problematic taxon ‘Platecarpus’ ptychodon. Journal of Systematic Palaeontology. doi:10.1080/14772019.2020.1818322.