|Elasmosaurid Thalassomedon haningtoni, Denver Museum of Nature and Science|
I started out just intending to do Plesiosauria, but then added basal sauropterygians on the premise "when am I ever going to be here again?" All told they sorted out into three sheets: one for plesiosaurs proper, one for basal sauropterygians and relatives (nothosaurs, pachypleurosaurs, etc.), and one for placodonts, because I chickened out on their position and decided to hedge my bets. Not that it hurts, because there are enough placodonts to make a decent sheet, and they make a pretty tight-knit clan. I'm not sure if I will add another sheet next year; I may do something else. With plesiosaurs, I really got into the margins of my marginal expertise, and I don't know if I fancy going much farther into, say, mosasaurs or ichthyosaurs.
Plesiosauria is one place where my insistence on including dubious taxa bit me. (169 of 316 names on the plesiosaur sheet are dubious, and that's not counting another couple dozen or so vintage names that were hopeless.) Plesiosaurus taxonomy makes Cetiosaurus, Iguanodon, and Megalosaurus seem well-thought-out. I am aware that 19th century Victorian paleontologists did not have the many years of experience we now have (nor our publication standards), but that doesn't mean every damn plesiosaur vertebra required its own species. Anyway, if Column D has the dreaded "Nomen dubium", or the genus name is in quotes, beware!
Onto the review! Since October 8, 2017, I have logged 83 changes on the Updates sheet. Of these, there were 43 new taxa, 5 reinstatements, 3 sinkings of species, 1 transfer of a species to a different genus (Ajancingenia yanshini to Heyuannia), 1 reinstatement of a species to a new genus ("Pterodactylus" crassipes to new genus Ostromia), and 1 species removed from a sheet because it was already listed on another sheet ("Ornithocheirus" hilsensis, now only to be found on the dinosaur sheet). The other changes were the usual run of changing classifications, updated formation ages, or updated geography.
Temporally, the list was again heavily biased to the Cretaceous, a bit more to the Late Cretaceous than last year: 4 Late Triassic, 2 Early Jurassic, 1 Early–Middle Jurassic, 1 Middle Jurassic, 3 Late Jurassic, 11 Early Cretaceous, 1 Early–Late Cretaceous, and 20 Late Cretaceous. Geographically, China leads again with 12, followed by the United States at 8. Third place was a three-way tie between Argentina, Mongolia, and Morocco, then Canada at sixth with 3, and eight nations with a single species (Australia, Brazil, Egypt, France, Mexico, Niger, Russia, and South Africa). Taxonomically, we get:
5 new pterosaur species:
C. hanseni is pretty basal, while the other four are much more derived.
1 new dinosauromorph species:
Soumyasaurus aenigmaticus, a silesaurid
13 new theropod species:
This list is overwhelming coelurosaurian. With the exception of basal tetanuran Pandoravenator fernandezorum and possible exception of megaraptoran Tratayenia rosalesi (it depends on where you stand on megaraptoran classification), these are all coelurosaurians. Two of the less species-rich coelurosaur clades come out well this time around, with two ornithomimosaurs (Afromimus tenerensis and Arkansaurus fridayi) and three alvarezsaurs, after several years of no new alvarezsaurs (Bannykus wulatensis, Qiupanykus zhangi, and Xiyunykus pengi).
2 new basal sauropodomorph species:
Both ends of the "prosauropod" spectrum are represented. (Ledumahadi mafube goes with the sauropods in my list, as discussed before.)
10 new sauropod species:
This group actually covers sauropod diversity in time and space fairly well, the main exceptions being absences of the Late Jurassic and Europe. It's been an unusually good 12 months for dicraeosaurids, with Lingulong shenqi and Pilmatueia faundezi.
7 new ankylosaurian species:
It has been a very strong year for ankylosaurs, particularly from the Late Cretaceous of North America. The only odd species out is Jinyunpelta sinensis, from the Early–Late Cretaceous of China.
0 new ceratopsian species:
5 new ornithopod species:
No hadrosaurids this year. Rhabdodonts pick up one new species (Matherodon provincialis) and gain from a reinstatement (Rhabdodon septimanicus).
These were primarily housekeeping moves, although in keeping with the ankylosaurian festivities, that group gains three more.
Drinker nisti, "Nanosaurus" rex, and Othnielosaurus consors all joined their powers with Nanosaurus agilis to form a super Morrison "hypsilophodont". (We can dicker about the name, but it seems reasonable to me that there was basically one Morrison hypsil genus and, seemingly, species.)