Giving Oviraptorosaurs a Hand

[Caption of this figure is pretty long, so it’s placed at the bottom.]

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Last year, when dealing with the apparent basal oviraptorid Wulatelong gobiensis (Xu et al., 2013) I created a graphical chart of many caenagnathid and oviraptorid hands, so that readers could view the rampant diversity (and diagnostic value) in oviraptorosaur hands. It wasn’t complete. I knew of Gigantoraptor erlianensis but had not included it, not that I can do much with it given the authors never supplied measurements for its hand, nor had I done non-caenagnathoids (the group that only includes Caenagnathidae and Oviraptoridae). The arrival of Anzu wyliei allows for a revision of this chart, shown above. I include this as a new post to bring attention to it, and allow use of the original one at the original link.

What has changed? First, I’ve added Gigantoraptor erlianensis (D), then fixed a lettering issue (K was omitted from the alphabet!), added Anzu wyliei (C), and finally added Protarchaeopteryx robusta and Caudipteryx sp. (A and B, respectively). This also necessitated some revision of the key, including the addition of another series of numbers so as to highlight differences or similarities. Gigantoraptor erlianensis (Xu et al., 2007), as it turns out, has a fairly oviraptorid-style manus, and I’m not sure what to make of this. I knew it was a pretty mosaic-y, and odd, duck; but this variance is tricky, as Xu et al. had used the hand in part to refer Gigantoraptor to Oviraptoridae. Nonetheless, its addition can’t be but to the good.

Adding in Anzu wyliei (Lamanna et al., 2014) enforces its caenagnathid features, as well as adds a character to the key I’d overlooked: the very stretched out proportions of the hands of caenagnathids (only Hagryphus giganteus among certain caenagnathids seems to have a “short” hand).

The presence of two basal oviraptorosaurs help reveal polarities in the manus, including some particularly maniraptoran characteristics. Caudipteryx spp. have a pretty basic hand morphology, with two missing bones from the third finger, but are otherwise very similar to Protarchaeopteryx robusta. And despite the dimensions of the arm in the latter, which are pretty big, the hand is proportionately short, smaller than Caudipteryx sp. despite the small actual size of the former. As all these hands are scaled to the same carpometacarpal length (conjoined projected lengths of distal carpal + metacarpal II), these proportions are very easy to see in comparison.

Below is the revised key for the above.

Caenagnathid apomorphies: Blue, C-G
1. Metacarpal 1 extends further than 40% of length of metacarpal 2;
2. Metacarpal 3 extremely gracile and much thinner than metacarpal 2;
3. Metacarpal 3 does not extend as far as distal end of metacarpal 2;
4. Digit 3 extremely gracile and much thinner than digit 2;
5. Phalanges 1 and 2 of digit 3 of nearly even length;
6. Digit 3 does not extend as far distally as manual digit 2;
7. Unguals with broad bases expand laterally, forming “spurs”;

Oviraptorid apomorphies: Red, H-O
8. Metacarpal 1 shorter than 40% of length of metacarpal 2;
9. Digit 1 ungual as long or longer than unguals 2 or 3;
10. Phalanx 1 of digit 2 shorter than phalanx 2;
11. Metacarpal 3 thicker than 50% or metacarpal 2;
12. Metacarpal 3 extends as far as distal end of metacarpal 2;
13. Phalanx 2 of digit 3 shorter than phalanx 1, and much shorter than phalanx 3;
14. Digit 3 extends as far as distal end of digit 2;
15. Unguals narrow, lacking expanded “spurs”;

“Ingeniine” apomorphies: Green, P-R
16. Metacarpal 1 much broader than metacarpal 2;
17. Metacarpal 1 extends further than 50% of metacarpal 2 (convergent with Caenagnathidae);
18. Digit 1 extends as far as distal ends of digits 2 and 3, due to shortening of digits 2 and 3;
19. Phalanx 2 of digit 2 shorter than phalanx 1;
20. Phalanges of digit 3 become progressively shorter until ungual;
21. Digit 3 does not extend as far as digit 2 (convergent with Caenagnathidae);

Other apomorphies of selected taxa: Yellow
22. Interphalangeal joints of phalanges much broader than diaphyses of phalanges;
23. Carpometacarpal fusion (possibly ontogenetic);
24. Phalanges 1 and 2 of digit 2 of relatively even length;
25. Digit 2 extremely elongated relative to metacarpal 2;

Characteristics generally not found in Caenagnathoidea: Violet, A & B
26. Semilunate carpal block not fused;
27. Phalanx 2 of digit 2 significantly longer than phalanx 1;
28. Phalanges 1 and 2 of digit 3 don’t extend as far as midlength of phalanx 1 of digit 2;
29. Phalanx 3 of digit 3 significantly longer than phalanges 1, 2, or combined 1+2 of digit 3;
30. Loss of ungual on digit 3;
31. Ungual of digit 1 80% or less the length of phalanx 1.

Caption:
The hands of oviraptorosaurs, showing basal oviraptorosaurs (A-B), Caenagnathidae (C-G) and Oviraptoridae (H-R). Colors signify diagnostic attributes of each group, with blue representing caenagnathid features (1-7), red representing oviraptorid features (8-15), green representing “ingeniine” features (16-21), light orange representing other features (22-25) not evenly distributed among taxa, and violet representing features basal to or restricted to non-caenagnathoid oviraptorosaurs (26-31). See text for clarification.

A, Protarchaeopteryx robusta, based on NGMC 2127;
B, Caudipteryx sp., based on IVPP V12430;
C, Anzu wyliei, based on CM 78000;
D, Gigantoraptor erlianensis, based on LH V0011;
E, Chirostenotes pergracilis, based on CMN 2367 and RTMP 1979.20.1;
F, Hagryphus giganteus, based on UMNH VP 12765;
G, Elmisaurus rarus, based on ZPAL MgD-I/98;
H, Wulatelong gobiensis, based on IVPP V18409;
I, Oviraptor philoceratops, based on AMNH FABR 6517;
J, the Bayan Mandahu “oviraptorine,” IVPP V9608;
K, the Zamyn Khondt “oviraptorid,” MPC-D 100/42;
L, Citipati osmolskae, based on MPC-D 100/979;
M, Conchoraptor gracilis, based on MPC-D 100/20;
N, Khaan mckennai, based on MPC-D 100/1127;
O, Machairasaurus leptonychus, based on IVPP V15979;
P, Nemegtomaia barsboldi, based on MPC-D 107/15 and 107/16;
Q, “Ingenia“ yanshini, based on MPC-D 100/30;
R, Heyuannia huangi, based on HYMV1-2.

All manus are scaled to the same carpal-metacarpal lengths, with missing material shaded.

Lamanna, M. C., Sues, H.-D., Schachner, E. R. & Lyson, T. R. 2014. A new large-bodied oviraptorosaurian theropod dinosaur from the Latest Cretaceous of western North America. PloS ONE 9 (3): e92022.
Xu X., Tan Q., Wang J., Zhao X. & Tan, L. 2007. A gigantic bird-like dinosaur from the Late Cretaceous of China. Nature 447:844-847.
Xu X., Tan Q.-w., Wang S., Sullivan, C., Hone, D. W. E., Han F.-l., Ma Q.-y., Tan L. & Xiao D. 2013. A new oviraptorid from the Upper Cretaceous of Nei Mongol, China, and its stratigraphic implications. Vertebrata PalAsiatica 51 (2): 85–101. [PDF]